Trueness of 12 intraoral scanners in the full-arch implant impression: a comparative in vitro study

Intraoral scanners in implant prosthodontics. A narrative review

OBJECTIVES

To review the developments in intraoral scanner (IOS) technologies applied in implant prosthodontics, emphasizing their influence on the accuracy of digital impressions, occlusal registrations, and the fit of implant-supported restorations.

DATA

A collection of published articles related to implant prosthodontics, the accuracy of digital impressions, occlusal registration, and the fit of implant-supported fixed restorations.

SOURCES

Three search engines were selected: Medline/PubMed, EBSCO, and Cochrane. A manual search was also conducted.

STUDY SELECTION

A literature search screened relevant databases and journals for studies on IOS applications in digital implant prosthodontic workflows from Dec 2018 to Dec 2023. Inclusion criteria encompassed randomized control trials, clinical trials, case series, and in vitro research focused on the use of IOS in digital implant prosthodontics.

CONCLUSIONS

The increased utilization of digital dental technologies has led to significant integration of digital implant prosthodontic workflows into clinicians' clinical practice. Several variables affect the accuracy of digital impressions generated by IOS. Generally, the prevailing opinion in academic papers is that digital workflows are suitable for addressing short-span implant-supported restorations. However, when it comes to long-span defects, the accuracy of digital workflows is still a matter of debate. Digital bite registration is an integral part of the workflow. It depends mainly on the defect size and location, scan strategy, anatomical tooth variations, overbite and other factors. The overall fit of digitally prefabricated implant restorations comprises of proximal, occlusal contacts and how accurately the restoration connects with implants. Research methodologies need standardization for further validation.

CLINICAL SIGNIFICANCE

In clinical practice, it is essential to have a thorough and up-to-date comprehension of various factors that can affect the accuracy of digital impressions and the fit of the final prosthesis in implant prosthodontics.

Trueness of maxillomandibular relationship in 3D-printed and conventional casts

OBJECTIVES

To compare the trueness of maxillomandibular relationship between articulated 3D-printed and conventional diagnostic casts in maximum intercuspation (MIP).

METHODS

Reference casts were articulated in MIP, and scanned using a Coordinate Measurement Machine (CMM, n = 1). Digital scans were made from the reference casts by using an intraoral scanner (IOS, n = 10) (Trios 4; 3Shape A/S). IOS scans were processed to create 3D-printed casts by using MAX UV385 (Asiga) and NextDent 5100 (3DSystems) 3D-printers. The conventional workflow implemented vinylpolysiloxane (VPS) impressions and Type IV stone. Stone and 3D-printed casts were articulated and digitized with a laboratory scanner (E4; 3Shape A/S). The 3D-printed casts were scanned on two occasions: with and without positioning pins. Inter-arch distances and 3D-contact area were measured and compared. Statistical tests used were Shapiro-Wilk, Levene's, Welch's t-test, and 2-way ANOVA (α=0.05).

RESULTS

IOS group showed similar or better maxillomandibular relationship trueness than stone casts and 3D-printed casts (p < 0.05). 3D-contact area analysis showed similar deviations between 3D-printed and stone casts (p > 0.05). The choice of 3D-printer and presence of positioning pins on the casts significantly influenced maxillomandibular relationship trueness (p < 0.05).

CONCLUSIONS

Articulated 3D-printed and stone casts exhibited similar maxillomandibular relationship trueness.

CLINICAL SIGNIFICANCE

Although 3D-printing methods can introduce a considerable amount of deviations, the maxillomandibular relationship trueness of articulated 3D-printed and stone casts in MIP can be considered similar.

Do intraoral scanning technologies affect the trueness of dental arches with crowding, diastema, and edentulous spaces? A clinical perspective

OBJECTIVES

To evaluate the trueness of dental arches digitised by two intraoral scanning (IOS) technologies from patients presenting crowding, diastema, and bilateral posterior edentulous space with tilted molar.

METHODS

Conventional impressions and dental stone models were generated from three patients presenting the aforementioned dental arch conditions. These models were digitised on a desktop scanner, and the resulting mesh was used as reference. Subsequently, the patients were scanned using confocal based (CF; iTero Element 2) and blue laser-multiscan (BLM; Virtuo Vivo) imaging IOS technology, totalling thirty scans. The meshes from the scans were exported in Standard Tessellation Language format and analysed using Geomagic Control X software. Root mean square (RMS) indicated deviation magnitude. Differences in IOS technologies were evaluated with paired t-tests, and dental arch conditions compared using ANOVA and post-hoc Tukey tests (α=0.05).

RESULTS

Digital dental arch from blue laser-multiscan technology showed lower trueness compared to confocal based technology for crowding (p = 0.0084) and edentulous spaces (p = 0.0025) conditions. When the types of oral condition were compared, discrepancies were significantly different for both IOS technologies, featuring the arch with diastema showing the lowest trueness, followed by edentulous spaces and crowding.

CONCLUSION

Dental arches presenting crowding and edentulous spaces digitised by blue laser-multiscan technology exhibited greater discrepancies compared to confocal based imaging technology. Furthermore, trueness varied among the dental arch conditions.

CLINICAL SIGNIFICANCE

The IOS technology and patient's dental arch condition can influence the trueness of dental arch digitisation. Being aware of these effects allows clinicians to take them into account during scanning procedures, digital planning and manufacturing.

Post sterilization of intraoral scan body and the effect it has on the axes and distances between three adjacent implants: in-vitro study

BACKGROUND

The purpose of this pilot in-vitro study was to assess the effect of sterilization on the intra-implant axis, inter-implant axis, intra-implant distance and inter-implant distance of three implants in a straight line by using laboratory scanner (LBS) versus intra-oral scanner (IOS) with intra-oral scan bodies (ISB).

METHODS

A printed 3D model with three internal hex analogs in the positions 15#,16#,17# was used. Zirkonzhan (ZZ) intra-oral scan body (ISB), two-piece titanium was used. The ZZ ISBs were scanned by 7 Series dental wings (LBS) and 30 times by Primescan (IOS) pre sterilization and 30 times post sterilization. For each scan (pre and post) stereolithography (STL) file was created and a comparison between all the scans pre sterilization and post sterilization were superimposed on the laboratory scan by using a 3D analyzing software. A Kolmogorov-Smirnov test performed followed by Wilcoxon Signed Ranks tests. (p < 0.05) Results: Post sterilization of the ZZ ISB, the mean errors were significantly increased for the inter-implant distances (p < 0.0005), intra-implant distances 1,2,3 (p < 0.0005), intra-implant axis 1,3 (p < 0.0005) and inter-implant axes 13,23 (p < 0.05). In contrast, the mean errors for intra-implant axis 2 (p < 0.0005) and inter-implant axis 12 (p < 0.0005) were significantly reduced.

CONCLUSIONS

ZZ ISB showed changes in all four parameters after sterilization. The middle ISB had the largest changes in mean error regarding all four parameters. Sterilization process may affect the three-dimensional (3D) structure of the ZZ ISB after three cycles. There is a lack in the literature in this field and there is a need for further studies to explore the effect of sterilization (multiple cycles) on different ISBs and for creating an approved guidelines regarding the amount of sterilization for each ISB in the industry.

Trueness of Intraoral Scanners in Different Scan Patterns for Full-Arch Digital Implant Impressions

The optimal scan pattern for full-arch digital implant impressions remains to be determined. This study aimed to analyze the effects of different scan patterns on the trueness of intraoral scanners for full-arch digital implant impressions. A maxillary plaster model with 4 implant analogs was employed as the master model. Scan bodies were attached to the master model and scanned with a laboratory scanner to obtain reference data. Test scans were obtained using 3 different scan patterns with Cerec Primescan and Trios 3. Each test datum was superimposed onto the reference data. The trueness was assessed by determining the 3D distance and angular deviations between the test and reference data. Significant differences in 3D distance deviation were detected among the scan patterns for both scanners. Significant differences in angle deviation were detected among the scan patterns for the Cerec Primescan, whereas it was not substantial for the Trios 3. Cerec Primescan exhibited superior trueness across all scan patterns compared with Trios 3. The zigzag pattern resulted in more accurate scans for the Cerec Primescan, whereas both the zigzag and occlusal-palatal-buccal patterns showed higher accuracy for the Trios 3.

Comparison of the accuracy of two techniques for three-dimensional digital indirect bonding of orthodontic brackets: A randomized controlled trial

OBJECTIVE

This study aimed to clinically compare the accuracy of bracket positioning between three-dimensionally (3D) printed indirect bonding trays and vacuum-formed trays made over 3D-printed models.

MATERIAL AND METHODS

Fourteen patients, planned for fixed orthodontic therapy, were randomly divided into two equal groups. For both groups, both dental arches were scanned, to acquire virtual models, brackets were virtually positioned from central incisors to second premolars, and scans for the final bracket positions were performed. In the first group, transfer trays were 3D-printed. In the second group, virtual models were 3D-printed, and vacuum-formed soft sheets were thermoformed on the printed model. Teeth were indirectly bonded and then scanned. Superimposition of the virtual and the final bracket positioning scans was performed to measure linear and angular deviations in brackets positions.

RESULTS

The first group showed significantly less occlusogingival and buccolingual linear errors than the second group. No significant differences in angular deviations were found between both groups. The frequencies of clinically acceptable linear errors within 0.5 mm and angular errors within 2° showed no statistically significant difference between both groups (p> 0.05 for all measurements). The transfer errors in both groups showed linear directional biases toward the mesial, gingival and labial directions. There was no statistically significant difference in the rate of immediate debonding between both groups (10.7% and 7.1% for the first and the second groups, respectively, p=0.295).

CONCLUSIONS

3D-printed indirect bonding trays were more accurate than vacuum-formed trays, in terms of linear deviations. Both types of trays showed similar angular control.

Effect of different impression coping and scan body designs on the accuracy of conventional versus digital implant impressions: An in vitro study

OBJECTIVES

This in vitro study compared the accuracy of conventional versus digital impression techniques for angulated and straight implants using two different impression coping and scan body designs.

METHODS

Two implant systems were used: Straumann and Dentegris. Two implants were placed for each system, straight and angulated at 15 degrees mesiodistally. Conventional impressions were made using the splinted open-tray technique using narrow impression coping (NIC) and wide impression coping (WIC). The stone casts produced from the conventional impression were digitized with a lab scanner (3Shape D2000). Digital impressions were made using four intraoral scanners (IOS): 3Shape Trios 3, Medit i700, Cerec Omnicam, and Emerald Planmeca using short scanbodies (SSB) and long scanbodies (LSB). The scanning was repeated ten times to generate the Standard Tessellation Language (STL) files. The distance and angle deviations between impression copings and scanbodies were measured in reference to the master model.

RESULTS

The trueness and precision of SSB and WIC were significantly better than LSB and NIC (p<0.001). The range trueness of the platform deviation was better with SSB (37.1 to 51.9) than LSB (89.6 to 127.9 μm) and for WIC than NIC in conventional impressions (58.2 and 75.1 μm, respectively). The trueness of the angle deviation of digital scans with SSB (0.11 to 0.25 degrees) was significantly better than scans with LSB (0.31 to 0.57 degrees) and for WIC than NIC (0.21 and 0.52 degrees, respectively). The precision of the platform deviation of digital scans with SSB (12.4 to 34.5 μm) was higher than other scans and conventional impressions (42.9 to 71.4 μm). The precision of the angle deviation of Medit i700 and Trios 3 with SSB (0.17 and 0.20 degrees, respectively) was higher than other scans with SSB and conventional impressions (0.54 to 1.63 degrees).

CONCLUSIONS

Digital scans with SSB were more accurate than conventional splinted open-tray impressions. The type of impression coping and scanbody significantly affected the impression accuracy.

CLINICAL SIGNIFICANCE

The use of a short scanbody can increase the accuracy of digital impressions, and wide impression coping can increase the accuracy of conventional impressions, resulting in improved clinical outcomes.

Effect of splinting scan bodies on the trueness of complete arch digital implant scans with 5 different intraoral scanners

STATEMENT OF PROBLEM

The absence of fixed reference points can affect the trueness of complete arch intraoral digital implant scans. The effect of splinting intraoral scan bodies (ISBs) or the inclusion of artificial landmarks (AL) on the trueness of complete arch digital implant scans is still unclear.

PURPOSE

The purpose of this study was to analyze the effect of splinting ISBs or the inclusion of AL on the trueness of complete arch digital implant scans with 5 intraoral scanners (IOSs).

MATERIAL AND METHODS

Six tissue-level dental implants (Straumann Tissue Level) were placed in an edentulous patient, and the correspondent definitive cast was digitized with a desktop scanner (IScan4D LS3i) to obtain the reference digital cast. Digital scans (n=10) were performed with 5 IOSs: TRIOS 4, Virtuo Vivo, Medit i700, iTero Element 5D, and Cerec Primescan. Three different scanning techniques were evaluated: conventional (cIOSs), splinted (sIOSs), and AL (AL-IOSs). The scan data obtained were imported into a metrology software program and superimposed to the reference digital cast by using a best-fit algorithm. The overall deviations of the positions of the ISBs were evaluated by using the root-mean-square (RMS) error (α=.05).

RESULTS

The mean ±standard deviation trueness values for the cIOSs, sIOSs, and AL-IOSs groups were 48 ±8 µm, 53 ±7 µm, and 49 ±11 µm, respectively, with no statistically significant differences (P=.06). Significant differences were found for the IOSs used with each technique (P<.001). Primescan (27 ±4 µm cIOSs; 28 ±3 µm sIOSs; 31 ±3 µm AL-IOSs) showed significantly higher trueness than iTero 5D (47 ±5 µm cIOSs; 47 ±4 µm sIOSs; 50 ±6 µm AL-IOSs) (P=.002) and TRIOS 4 (93 ±18 µm cIOSs; 76 ±18 µm sIOSs; 107 ±13 µm AL-IOSs) (P=.001) for all techniques. In addition, no significant differences were found between the techniques by using iTero 5D or Primescan (P=.348 and P=.059, respectively).

CONCLUSIONS

The cIOSs, sIOSs, and AL-IOSs techniques showed similar trueness. The IOS used influenced the trueness of complete arch digital implant scans.

Evaluating the influence of palate scanning on the accuracy of complete-arch digital impressions-An in vitro study

OBJECTIVES

To assess the impact of including the palate and the number of images recorded during intraoral digital scanning procedure on the accuracy of complete arch scans.

METHODS

An experienced operator conducted 40 digital scans of a 3D printed maxillary model and divided them into two groups: 20 with inclusion of the palate (PAL) and 20 without (NPAL). Each set of scans was performed using an intraoral scanner (IOS) (Trios 5; 3Shape A/S; Copenhagen, Denmark). The resulting STL files were imported into the Geomagic Control X software (3D Systems, Rock Hill, SC, USA) for accuracy comparison. A reference STL file was created using a 3Shape E3 laboratory scanner (3Shape Scanlt Dental 2.2.1.0; Copenhagen, Denmark). The number of images captured was recorded during the scanning procedure.

RESULTS

In the case of the right side no statistically significant difference in trueness was detected (84 µm ± 45.6 for PAL and 80.4 ± 40.4 µm for NPAL). In the case of the left side no significant difference in trueness was observed (215.1 ± 70.2 µm for PAL and 233.9 ± 70.7 µm for NPAL). In the case of the arch distortion a statistically significant difference in trueness was seen between the two types of scans (135.3 ± 71.9 µm for PAL and 380.4 ± 255.1 µm for NPAL). The average number of images was 831.25, and 593.8 for PAL and NPAL, respectively.

CONCLUSIONS

Scanning of the palatal area can significantly improve the accuracy of dental scans in cases of complete arches. In terms of the number of images, based on the current results, obvious conclusions could not be drawn, and further investigation is required.

CLINICAL SIGNIFICANCE

Scanning the palate may be beneficial for improving the accuracy of intraoral scans in dentate patients. Consequently, this should be linked to an appropriate scanning strategy that predicts palatal scanning.

Evaluation of the accuracy of seven intraoral scanners for the full dentate and partially edentulous complete-arch mandibular casts: An in vitro comparison

Statement of problem

Intraoral scanners (IOSs) are widely used in dentistry, providing high accuracy in short-range scanning. Nevertheless, when scanning the full dental arch, it remains a challenge. Furthermore, there is a lack of studies reporting the differences in scan accuracy between dental arches with large-span mucosal areas and fully dentate casts or optimal IOS selection for different dental statuses.

Purpose

This study aimed to evaluate the accuracy and scanning time of different IOSs for full dentate (FD) and partially edentulous (PE) casts with missing teeth in the #34-#44 range and to determine the IOSs with the optimal clinical adaptability and scanning accuracy for different complete-arch casts.

Material and methods

Reference scans of two complete-arch (FD and PE) casts were obtained using a laboratory scanner (Ceramill Map 600). Subsequently, the same casts were scanned ten times each by seven IOSs (3Shape Trios 3, CS3600, Planmeca Emerald, iTero Element 5D, Medit i500, BAMBOO B1, and Shining Aoralscan 3), and the scanning time was recorded. The test data were superimposed on the reference scans for the selected areas, and three-dimensional deviations between the reference and test casts (trueness), and between test casts (precision) were determined using reverse engineering software (Geomagic Wrap). The dataset was analyzed using a two-factor analysis of variance with post-hoc Bonferroni tests.

Results

Two-factor analysis of variance revealed significant differences in accuracy and scanning time for different casts (P < 0.001) and IOSs (P < 0.001). For the FD cast, the i500 (0.35 ± 0.11 mm trueness) and CS3600 (0.23 ± 0.12 mm precision) performed worse than the remaining scanners. For the PE cast, the BAMBOO B1(0.89 ± 0.58 mm trueness; 0.88 ± 0.48 mm precision) performed worse than the remaining scanners. There were no differences in the accuracy of scanning between the Element 5D and Emerald for both cast types. However, the scanning time differed significantly between the different IOSs (P < 0.001). Regardless of the cast type, the fastest and slowest scans were performed by the Trios3 and CS3600 scanners respectively.

Conclusions

The accuracy and scanning time differed between the different IOSs and types of complete-arch casts.

Influence of the ambient color lighting on the accuracy of complete arch implant scans recorded by using two intraoral scanners

STATEMENT OF PROBLEM

The influence of different ambient factors including lighting has been previously studied. However, the influence of ambient color lighting settings on intraoral scanning accuracy remains uncertain.

PURPOSE

The purpose of this in vitro study was to assess the influence of ambient color lighting on the accuracy of complete arch implant scans recorded by using 2 intraoral scanners (IOSs).

MATERIAL AND METHODS

An edentulous maxillary cast with 6 implant scan bodies was digitized by using a laboratory scanner (DW-7-140) to obtain a reference file. Two groups were created based on the IOS tested: TRIOS 4 (IOS-1) and i700 (IOS-2). Seven subgroups were developed depending on the ambient color lighting (red, green, blue, yellow, cyan, magenta, and white) (n=15). Scanning accuracy was analyzed by using a metrology software program (Geomagic Control X). The Kruskal-Wallis, 1-way ANOVA, and pairwise comparisons were used to analyze the data (α=.05).

RESULTS

Significant trueness and precision values were found across the groups (P<.05) and subgroups (P<.05). For IOS-1, blue ambient lighting obtained the best trueness (19.8 ±1.8 µm) (P<.05); in precision, white light (20.8 ±7.3 µm) and blue light (22.1 ±13.5) showed the best results (P<.05). For IOS-2, white light showed the best trueness (51.9 ±16.7 µm); the best precision was obtained under magenta (38.6 ±10.4 µm) and yellow light (52.6 ±24.0 µm) (P<.05).

CONCLUSIONS

The optimal ambient color lighting varied between the IOSs assessed. As the best condition for maximizing accuracy was not found, ambient color lighting must be individualized for the IOS system used.

Accuracy of conventional impressions and digital scans for implant-supported fixed prostheses in maxillary free-ended partial edentulism: An in vitro study

OBJECTIVES

To evaluate the accuracy of conventional polyether impressions and digital scans produced by five intra-oral scanners (IOSs) in maxillary free-ended partial edentulism for long-span implant-supported prostheses.

METHODS

This in vitro study involved the impression of a maxillary model with free-end partial edentulism, in which six implants were placed before digitization using a desktop scanner to generate a digital reference model. Conventional impressions (Impregum Penta Soft, 3M) and digital scans with five IOSs (Trios 3 and 4, 3Shape; Primescan, Dentsply-Sirona; CS 3600, Carestream Dental; and i-500, Medit) were obtained. Conventional impressions were digitized using the same desktop scanner. Each digital STL file of conventional or digital impressions was superimposed over the reference STL file to enable comparison. Trueness was assessed by calculating angles and distance deviations. For precision, dispersions of values around their means were also measured.

RESULTS

The mean distance deviation was significantly higher for conventional impressions (454.24 ± 334.70 µm) than for IOSs (ranging from 160.98 ± 204.48 µm to 255.56 ± 395.89 µm) (p < 0.001). The mean angular deviation was high with conventional impressions (1.82 ± 1.51°), intermediate with CS 3600 (1.38 ± 1.42°), Primescan (1.37 ± 2.54°) and Trios 4 (1.30 ± 0.64°) scanners, and lower with I500 (0.97 ± 0.75°) and Trios 3 (1.01 ± 0.85°) scanners (p < 0.001). The dispersion of distance values around their means was lowest with Trios 3 and i-500, followed by CS3600, Primescan, and Trios 4, respectively, and higher for conventional impressions (p < 0.001). The dispersion of angular values was smallest with i-500, Trios 3, and Trios 4 compared with other groups and was highest with Primescan (p < 0.001).

CONCLUSIONS

Within the limits of the current study, Trios 3 scanner exhibited the highest accuracy, followed by i-500, Trios 4, CS 3600, Primescan, and conventional impressions respectively. IOSs might be reliable for the fabrication of an implant-supported prosthesis. In vivo studies are required to confirm these findings.

CLINICAL SIGNIFICANCE

Passive adaptation of the implant-supported framework is a challenge when rehabilitating patients with maxillary free-end partial edentulism. While Conventional impressions remain a reliable and validated technique, but IOSs demonstrated higher accuracy, suitable for the fabrication of long-span implant-supported prostheses in partially edentulous arch.

Influence of intraoral scanning coverage on the accuracy of digital implant impressions - An in vitro study

OBJECTIVES

To evaluate the influence of intraoral scanning coverage (IOSC) on digital implant impression accuracy in various partially edentulous situations and predict the optimal IOSC.

METHODS

Five types of resin models were fabricated, each simulating single or multiple tooth loss scenarios with inserted implants and scan bodies. IOSC was subgrouped to cover two, four, six, eight, ten, and twelve teeth, as well as full arch. Each group underwent ten scans. A desktop scanner served as the reference. Accuracy was evaluated by measuring the Root mean square error (RMSE) values of scan bodies. A convolutional neural network (CNN) was trained to predict the optimal IOSC with different edentulous situations. Statistical analysis was performed using one-way ANOVA and Tukey's test.

RESULTS

For single-tooth-missing situations, in anterior sites, significantly better accuracy was observed in groups with IOSC ranging from four teeth to full arch (p < 0.05). In premolar sites, IOSC spanning four to six teeth were more accurate (p < 0.05), while in molar sites, groups with IOSC encompassing two to eight teeth exhibited better accuracy (p < 0.05). For multiple-teeth-missing situations, IOSC covering four, six, and eight teeth, as well as full arch showed better accuracy in anterior gaps (p < 0.05). In posterior gaps, IOSC of two, four, six or eight teeth were more accurate (p < 0.05). The CNN predicted distinct optimal IOSC for different edentulous scenarios.

CONCLUSIONS

Implant impression accuracy can be significantly impacted by IOSC in different partially edentulous situations. The selection of IOSC should be customized to the specific dentition defect condition.

CLINICAL SIGNIFICANCE

The number of teeth scanned can significantly affect digital implant impression accuracy. For missing single or four anterior teeth, scan at least four or six neighboring teeth is acceptable. In lateral cases, two neighboring teeth may suffice, but extending over ten teeth, including contralateral side, might deteriorate the scan.

Influence of a specially designed geometric device and modified scan bodies on the accuracy of a maxillary complete arch digital implant scan: An in vitro study

STATEMENT OF PROBLEM

Capturing accurate complete arch digital implant scans remains a challenging process because of the lack of recognizable anatomic landmarks. The effect of modified scan bodies (SBs) on improving scanning accuracy is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the accuracy of a maxillary complete arch digital implant scan when using a specially designed geometric device with the accuracy of modified scan bodies.

MATERIAL AND METHODS

Four implants were placed in an edentulous maxillary model made of porous bone material with polyurethane attached gingiva. Scan bodies were attached to the implants and then digitized with a high precision laboratory scanner to create the reference scan. Round depressions were made on the buccal and palatal surfaces of the scan bodies, and the model was scanned with an intraoral scanner using 4 different scenarios: the model with no geometric device or modified scan bodies (ND-NM), device only without modified scan bodies (D-NM), no device but with modified scan bodies (ND-M), and device with modified scan bodies (D-M). Each group was scanned 10 times for a total of 40 scans. Trueness and precision were evaluated using inspection software to measure the 3D surface deviation. Trueness was measured by superimposing each test scan on the reference scan, and precision was calculated by superimposing the test scans of the same group with each other. Data were analyzed using the GraphPad Prism version 8.0.0 software program. Two-way ANOVA was performed to assess the effect of the device and modifications on trueness and precision (α=.05).

RESULTS

Both the geometric device and SB modifications had a significantly significant effect on trueness and precision (P<.001). Regarding trueness, group D-M had the lowest mean and standard deviation (0.158 ±0.028 mm) in contrast with group ND-NM, which had the highest deviation (0.282 ±0.038 mm). In terms of precision, group D-M showed the lowest mean and standard deviation (0.134 ±0.013 mm), while group ND-NM revealed the highest deviation (0.222 ±0.031 mm). However, no statistically significant interaction was found between the device and modifications regarding either trueness or precision (P>.05).

CONCLUSIONS

Using a specially designed geometric device improved both the trueness and precision of complete arch digital implant scans. The modified SBs had a positive influence on the scanning trueness and precision, and the best accuracy was achieved when using the geometric device and the modified SBs simultaneously.

Obtaining more accurate complete arch implant digital scans with the aid of a geometric pattern: A dental technique

A technique to obtain more accurate complete arch implant digital scans and virtual casts is described. In order to obtain complete arch implant digital scans with greater accuracy, short-span intraoral digital scans are superimposed with the aid of a geometric pattern. Therefore, the technique takes advantage of the accuracy of intraoral scanners to obtain digital scans of reduced spans. Two virtual designs of the geometric pattern have been made available online: one for maxillary arches and one for mandibular arches. From these virtual designs, new virtual designs of geometric patterns of different sizes and shapes can be created to better fit different arch forms and implant positions.

A comparative analysis of the passivity of fit of complete arch implant-supported frameworks fabricated using different acquisition techniques

STATEMENT OF PROBLEM

The accuracy of intraoral scanners (IOSs) in recording edentulous jaws has improved recently. However, improvement in accuracy does not necessarily imply the clinical validity of the scans, and limited information is available regarding the manufacture of passively fitting prostheses.

PURPOSE

The purpose of this in vitro study was to analyze the passivity of complete arch screw-retained frameworks fabricated using different acquisition techniques.

MATERIAL AND METHODS

A 3-dimensional maxillary edentulous model to receive all-on-4 screw-retained frameworks was prototyped. Eighteen polymethylmethacrylate (PMMA) frameworks were fabricated with a 5-axis milling machine and divided into 3 groups according to the acquisition technique (n=6): scanned by using an IOS (CEREC Primescan; Dentsply Sirona), scanned with the aid of an auxiliary device by using the same IOS, and by using a conventional impression and then scanning the stone cast with an extraoral scanner (EOS). The passivity of fit of the frameworks was tested with the 1-screw test, the terminal screw of the framework assembly was tightened on the multiunit abutment (MUA), and the vertical marginal gap (µm) was measured at the other 3 framework-to-abutment interfaces by using a digital microscope at ×40 magnification. A modification to the 1-screw test was analyzed by tightening all screws and then unscrewing all except 1 of the anterior abutments. Data were explored for normality by using the theoretical quantile-quantile (Q-Q) plots and the Shapiro-Wilk test of normality. The Friedman test compared data between the different acquisition techniques; the tightening methods and locations (buccal and palatal) were used as the block variable. The post hoc Dunn test was used when the Friedman test was significant. The Kruksal-Wallis test compared the data from the 2 groups of the tightening methods and the 2 location groups. The aligned rank transformation (ART) ANOVA test was used for the interaction effects among the 3 variables. A multiway ANOVA was applied to the ranked data. (α=.05 for all tests).

RESULTS

Significant differences were found among all groups (P<.001). Regarding the passivity of fit, the mean vertical marginal gap was 50 µm for frameworks fabricated from an intraoral scan with the aid of an auxiliary device, 62 µm for frameworks fabricated by using an IOS, and 140 µm for frameworks fabricated by using an EOS. No significant difference was found among all groups regarding the tightening method (P=.355) or location measured (P=.175).

CONCLUSIONS

Digital scanning with the aid of an auxiliary device resulted in the best fit; however, digital approaches with or without the auxiliary device resulted in a more accurate fit with a smaller marginal gap than with the conventional impression.

Improving the accuracy of complete arch implant intraoral digital scans by using horizontal scan bodies with occlusal geometry: A dental technique

A technique to improve the accuracy of complete arch implant intraoral digital scans and to obtain more accurate virtual casts with them is described. First, 2 complete arch intraoral digital scans were obtained with an intraoral scanner: a multiunit abutment digital scan and an implant digital scan with reusable horizontal intraoral scan bodies (ISBs) placed on the implants. These were previously created by combining the conventional ISBs compatible with the patient's implants with extensional structures with occlusal geometry. Once the digital scans had been acquired, the position of the implants was obtained by superimposing a virtual design of the conventional ISB onto each horizontal ISB of the complete arch implant digital scan. Finally, the virtual cast was obtained by superimposing the complete arch multiunit abutment digital scan on the complete arch implant digital scan.

Evaluation of effects of brackets and orthodontic wires on intraoral scans: A prospective in-vivo study

OBJECTIVE

To evaluate any distortion produced by multibracket fixed orthodontic appliances on digital models obtained from intraoral scans (IOS), considering the presence of both brackets only and brackets/archwire combination.

SETTING/SAMPLE

The IOS data of the arches of 20 patients (12 females and 8 males; mean age = 15.55 ± 2.84 years) were acquired using the CS3600 intraoral scanner (Carestream Dental, Atlanta, USA), without any appliances (model A), with vestibular brackets alone (model B) and then with brackets and orthodontic archwire fitted (model C).

MATERIALS AND METHODS

Data were acquired between the months of January and October 2021 at the moment of indirect bonding phase. On each model, five intra-arch linear measurements were obtained (inter-canine, inter-premolar 1 and 2, inter-molar and arch depth), and after digital matching between model A and B (match 1) and A and C (match 2), the linear discrepancies were evaluated at 20 points (10 occlusal and 10 gingivolingual) previous identified on the reference model A. All measurements were performed using Geomagic Control X software (3D Systems, Morrisville, USA), and any dimensional variations and distortions were evaluated by the linear regression analysis and two-sample t-test (P ≤ .05).

RESULTS

The results show an almost perfect correlation between both models B and C and the reference model A, both as regards the intra-arch linear measurements and the linear discrepancies found at the 20 identified points.

CONCLUSIONS

Multibracket fixed orthodontic appliances do not produce any relevant distortions in digital models obtained via intraoral scanning. Therefore, the removal of archwire is not mandatory before IOS.

Virtual implant scan body switch by using computer-aided design programs avoiding the need of obtaining a new intraoral implant digital scan: A novel protocol

OBJECTIVE

The present manuscript describes a technique to virtually switch an implant scan body eliminating the need of obtaining a new intraoral implant digital scan.

CLINICAL CONSIDERATIONS

Implant scan bodies assist on transferring the 3-dimensional position of the implants into the virtual definitive implant cast. However, if a different implant part is desired during the designing procedures of the implant restoration such as selecting a different implant abutment of varying height, angulation, or manufacturer, a new intraoral implant digital scan with the specific implant scan body is required.

CONCLUSIONS

This novel protocol aims to reduce possible complications that require capturing a new intraoral implant digital scan, facilitate prostheses design modifications after the obtention of the definitive intraoral implant digital scan, and to ease the manufacturing procedures.

CLINICAL SIGNIFICANCE

The novel technique may provide a solution for virtually switch implant scan bodies for fabricating implant-supported single crowns or short-span prostheses. Additional studies are needed before its clinical implementation.

Effect of scan pattern on the scan accuracy of a combined healing abutment scan body system

STATEMENT OF PROBLEM

A recently introduced scan body combined with a contoured healing abutment enables digital scans of the implant while its healing abutment shapes the soft tissue for an appropriate emergence profile. However, information on the effect of different scan patterns on the scan accuracy of this new system is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of scan pattern on the accuracy of digital implant scans by using a combined healing abutment-scan body system.

MATERIAL AND METHODS

A combined healing abutment-scan body system was secured on a single implant at the right first molar site in a dentate mandibular model. A master reference model was generated by scanning the model with an industrial light scanner. The model was then scanned with 4 different scan patterns (SP-A, SP-B, SP-C, and SP-D) by using an intraoral scanner (TRIOS 3). Test scans (n=8) were superimposed over the master reference model by using a metrology software, and distance and angular deviations were calculated. Distance and angular deviation data were analyzed with a multivariate analysis of variance and the Tukey honestly significant difference tests for trueness and precision (α=.05).

RESULTS

Distance deviations (trueness [P=.461] and precision [P=.533] deviations) in the scans were not significantly affected by the scan pattern. Scan pattern affected the trueness (P=.001) and precision (P=.002) when angular deviations were considered. In terms of trueness, SP-D resulted in the highest angular deviations in scans (P≤.031), while the difference in deviations in scans obtained by using other scan patterns was not significant (P≥.378). When angular deviation data were considered, SP-D resulted in lower scan precision than SP-A (P=.014) and SP-B (P=.007). The precision of scans using SP-C was similar to the precision of the scans made by using other scan patterns (P≥.055) in terms of angular deviations.

CONCLUSIONS

The scan accuracy of a combined healing abutment-scan body system was affected by the scan pattern. The scans performed with SP-D presented the lowest accuracy considering the angular deviation data and, therefore, may be the least favored among the patterns tested for scanning a combined healing abutment-scan body system.

Effect of artificial landmarks of the prefabricated auxiliary devices located at different arch positions on the accuracy of complete-arch edentulous digital implant scanning: An in-vitro study

OBJECTIVES

To examine the effect of artificial landmarks of prefabricated auxiliary devices (PAD) located at different arch positions on the accuracy of complete-arch edentulous digital implant scanning.

METHODS

A reference model containing four analogs and PAD were fabricated by a 3D printer (AccuFab-C1s, 3DShining). 10 digital scans were performed using an intraoral scanner (Aoralscan 3, 3DShining), sv 1.0.0.3115, with artificial landmarks located at different arch positions: group I, without any artificial landmarks; group II, with artificial landmarks at the anterior region; group III, with artificial landmarks at the posterior region. group IV: with artificial landmarks at both anterior and posterior regions. For group V: Conventional open-tray splinted impressions. The reference file and conventional stone casts were digitalized by using a dental laboratory scanner. The related files were imported into inspection software for trueness and precision assessment. Statistical analysis was performed with One-way ANOVA and Kruskal-Wallis test. The level of significance was set at α=0.05.

RESULTS

For the global accuracy assessment, significantly higher global trueness was seen in group II (p < 0.01), III (p < 0.001), IV (p < 0.001) and V (p < 0.001) than group I. Significantly higher global precision was seen in group III (p < 0.001), IV (p < 0.001) and V (p < 0.001) than group I. For the local accuracy assessment, the PAD primarily improved accuracy on the linear deviations.

CONCLUSIONS

Artificial landmarks of PAD at different arch positions significantly influenced the scanning accuracy. Applying the PAD in group IV could achieve comparable outcomes to conventional open-tray splinted impressions. Artificial landmarks on the posterior region may be more pivotal than those on the anterior region.

CLINICAL SIGNIFICANCE

Group IV could achieve comparable accuracy to conventional open-tray splinted impressions.

Trueness of intraoral scanning for different tooth-size arch-length deficiencies

Background/purpose

As science and technology continue to advance, the utilization of intraoral scanners (IOSs) has become increasingly popular in the orthodontic workflow. The aim of this study was to discuss whether the degree of crowded arches affects scan accuracy.

Materials and methods

Three different crowding levels of dental models (model MI: mild, model MO: moderate, and model SE: severe) were scanned using both an IOS and desktop scanner. Stereolithographic files were obtained and superimposed via CAD software to calculate differences between each measuring point of a model and the farthest corresponding point. The deviations from three models were compared with statistical analysis.

Results

The trueness of different crowding arches showed that the deviation value of model SE was the maximum, followed by model MI, and model MO in the maxillary arch. In the mandibular arch, the order of the deviation from greatest to least was firstly model SE, then model MO, and model MI. Significant differences were observed among the maxillary models (P < 0.001), but there was no significant difference between models in the mandible (P = 0.669).

Conclusion

The trueness of the three crowded arches is in the clinically acceptable range. The degree of crowding increases, the trueness of scanning at each position decreases. In the maxillary arch, more severe crowding corresponds to higher deviations. In the mandible, the degree of crowding is not explicitly related to the maximum deviation; therefore, the clinician should notice the deviation when using IOSs for crowding cases.

Effect of prefabricated auxiliary devices and scanning patterns on the accuracy of complete-arch implant digital impressions

OBJECTIVES

This study aimed to evaluate the impact of prefabricated auxiliary devices (PAD) and scanning patterns on the accuracy of complete-arch implant digital impressions.

METHODS

An edentulous maxillary model was inserted with four parallel implant analogs and four PAD. The model was scanned with D2000 dental laboratory scanner as the reference scans. Test scans were obtained by 8 different scanning patterns (SP), which including SPA, SPB, SPC, SPD, SPE, SPF, SPG and SPH, with (test group) or without (control group) using the PAD by an intraoral scanner (Aoralscan 3, 3DShining). SPA was the scanning pattern recommended by the manufacturer. Each scanning time was recorded. The related files were imported into inspection software for assessment. Aligned Ranks Transformation ANOVA, Kruskal-Wallis and Mann-Whitney tests were used to evaluate the values. The level of significance was set at α = 0.05.

RESULTS

The scanning patterns significantly influenced the linear accuracy in the test group and the scanning time for both groups. Lower linear trueness in the test group was found in SPF (p<0.05) and SPG (p<0.05). Longer scanning time was found in SPB and SPG for both groups. The test group demonstrated linear accuracy enhancement in all the scanning patterns; angular trueness enhancement was seen in SPA (p<0.05), SPC (p<0.01) and SPH (p<0.01). Significant longer scanning time was found in SPB (p<0.05), SPF (p<0.05), SPG (p<0.05) and SPH (p<0.05) when using PAD.

CONCLUSION

The scanning patterns impact the accuracy differently depending on the PAD's existence. The scanning time can be significantly influenced by the scanning patterns and the PAD.

CLINICAL SIGNIFICANCE

In daily clinical practice, selecting a suitable scanning pattern is significant in achieving accurate digital impressions. The PAD demonstrated effective linear accuracy enhancement in all the scanning patterns tested.

Influence of scanbody design and intraoral scanner on the trueness of complete arch implant digital impressions: An in vitro study

This study aimed to compare the accuracy of full-arch digital implant impressions using seven different scanbodies and four intraoral scanners. A 3D-printed maxillary model with six implants and their respective multi-unit abutments was used for this study. Seven scanbodies (SB1, SB2, SB3, SB4, SB5, SB6, and SB7) and four intraoral scanners (Primescan®, Omnican®, Trios 3®, and Trios 4®) were assessed. Each combination group was scanned ten times and a dental lab scanner (D2000, 3Shape) was used as a reference. All scans were exported as STL files, imported into Convince software (3Shape) for alignment, and later into Blender software, where their 3D positions were analyzed using a Python script. The 3D deviation, angular deviation, and linear distance between implants #3 and #14 were also measured. Accuracy was measured in terms of "trueness" (scanbody 3D deviation between intraoral scan and desktop scan). Kruskal-Wallis followed by the Bonferroni correction was used to analyze the data (⍺ = .05). The study found statistically significant differences in digital impression accuracy among the scanners and scanbodies (p<0.001). When comparing different intraoral scanners, the Primescan system showed the smallest 3D deviation (median 110.59 μm) and differed statistically from the others, while Trios 4 (median 122.35 μm) and Trios 3 (median 130.62 μm) did not differ from each other (p = .284). No differences were found in the linear distance between implants #3 and #14 between Trios 4, Primescan, and Trios 3 systems. When comparing different scanbodies, the lowest median values for 3D deviation were obtained by SB2 (72.27μm) and SB7 (93.31μm), and they did not differ from each other (p = .116). The implant scanbody and intraoral scanner influenced the accuracy of digital impressions on completely edentulous arches.

Influence of age, training, intraoral scanner, and software version on the scan accuracy of inexperienced operators

PURPOSE

To evaluate the effect of operator age on the scan accuracy (trueness and precision) of inexperienced operators when compared with experienced operators, and how training, intraoral scanner (IOS), and software version affect scan accuracy.

MATERIAL AND METHODS

Thirty-four operators were sorted into groups: G1 (operators <25 years old, no experience), G2 (operators >40 years old, no experience), and G3 (experienced IOS operators). They conducted partial-arch scans before and after a 4-session training with two IOSs (Trios 3 and True Definition) and two software versions. These scans were compared with the reference scans obtained from conventional impressions and a laboratory scanner (IScan D103i) to evaluate trueness (mean root mean square values) and precision (standard deviation of root mean square values) with a software program (Geomagic Control X). Kruskal-Wallis and post-hoc Dunn's tests were used to evaluate the effect of age on the scan accuracy of inexperienced groups when compared with experienced operators, while the effect of training, IOS, and software version on scan accuracy was evaluated with Wilcoxon or Mann-Whitney U tests (α = 0.05).

RESULTS

Before training, G1 and G2 scans had similar accuracy (p ≥ 0.065). After training, G1 scans had higher accuracy when IOS data was pooled and had higher precision with TD (p ≤ 0.004). Training increased the scan accuracy (p < 0.001), while newer software increased the trueness of inexperienced operator scans (p = 0.015).

CONCLUSIONS

Age affected the scan accuracy of inexperienced operators after training, indicating that extended training may be required for older operators. Training increased the scan accuracy, and newer software increased the trueness of inexperienced operator scans.

Trueness and precision of complete arch dentate digital models produced by intraoral and desktop scanners: An ex-vivo study

OBJECTIVES

The study aimed to compare the trueness and precision of five intraoral scanners (Emerald S, iTero Element 5D, Medit i700, Primescan, and Trios 4) and two indirect digitization techniques for both teeth and soft tissues on fresh mandibular and maxillary cadaver jaws.

METHODS

The maxilla and mandible of a fully dentate cadaver were scanned by the ATOS industrial scanner to create a master model. Then, the specimens were scanned eight times by each intraoral scanner (IOS). In addition, 8 polyvinylsiloxane (PVS) impressions were made and digitized with a Medit T710 desktop scanner. Stone models were then poured and again scanned with the desktop scanner. All IOS, PVS, and stone models were compared to the master model to calculate the mean absolute surface deviation for mandibular teeth, maxillary teeth, and palate.

RESULTS

For mandibular teeth, the PVS trueness was only significantly better than the Medit i700 (p < 0.001) and Primescan (p < 0.05). In maxillary teeth, the PVS trueness was significantly better than all IOSs (p < 0.05-0.001); the stone trueness was significantly better than Emerald S (p < 0.01), Medit i700 (p < 0.001) and Primescan (p < 0.01). In the palate, PVS and stone trueness were significantly lower than the iTero Element 5D (p < 0.01) and Trios 4 (p < p < 0.01). Stone trueness was significantly lower than the Medit i700 (p < 0.05). The precision in the palate was significantly lower for PVS and stone than for Emerald S (p < 0.01, p < 0.05), iTero Element 5D (p < 0.01, p < 0.01), Primescan (p < 0.001, p < 0.001), and Trios 4 (p < 0.001, p < 0.01). Significant differences in trueness between the IOSs were observed only in the mandibular teeth. The Medit i700 performed worse than Emerald S (p < 0.01) and iTero Element 5D (p < 0.01). For mandibular teeth, the Medit i700 was significantly more precise than Primescan (p < 0.01) and the Emerald S (p < 0.05). The Trios 4 was significantly less precise than Emerald S (p < 0.05). The precision of Medit i700 was significantly worse than iTero Element 5D (p < 0.01) for maxillary teeth, as well as the Primescan (p < 0.01) and Trios 4 (p < 0.05) for the palate.

CONCLUSIONS

In general, indirectly digitized models from PVS impressions had higher trueness than IOS for maxillary teeth; precision between the two methods was similar. IOS was more accurate for palatal tissues. The differences in trueness and precision for mandibular teeth between the various techniques were negligible.

CLINICAL SIGNIFICANCE

All investigated IOSs and indirect digitization could be used for complete arch scanning in mandibular and maxillary dentate arches. However, direct optical digitization is preferable for the palate due to the low accuracy of physical impression techniques for soft tissues.

Trueness and precision of combined healing abutment scan body system scans at different sites of maxilla after multiple repositioning of the scan body

OBJECTIVES

To evaluate the accuracy of the scans of the combined healing abutment-scan body (CHA-SB) system located at different sites of the maxilla when SBs are replaced in between each scan.

METHODS

Three SBs were seated into HAs located at the central incisor, first premolar, and first molar sites of a maxillary model inside a phantom head, and the model was scanned extraorally (CEREC Primescan SW 5.2). This procedure was repeated with new SBs until a total of 10 scans were performed. Standard tessellation language files of CHA-SBs at each implant location were isolated, transferred into analysis software (Geomagic Control X), and superimposed over the proprietary library files to analyze surface (root mean square), linear, and angular deviations. Trueness and precision were evaluated with one-way analysis of variance and Tukey tests. The correlation between surface and angular deviations was analyzed with Pearson's correlation (α=0.05).

RESULTS

Molar implant scans had the highest surface and angular deviations (P≤.006), while central incisor implant scans had higher precision (surface deviations) than premolar implant scans (P=.041). Premolar implant scans had higher accuracy than central incisor implant scans on the y-axis (P≤.029). Central incisor implant scans had the highest accuracy on the z-axis (P≤.018). A strong positive correlation was observed between surface and angular deviations (r = 0.864, P<.001).

CONCLUSION

Central incisor implant scans mostly had high accuracy and molar implant scans mostly had lower trueness. SBs were mostly positioned apically; however, the effect of SB replacement can be considered small as measured deviations were similar to those in previous studies and the precision of scans was high.

CLINICAL SIGNIFICANCE

Repositioning of scan bodies into healing abutments would be expected to result in similar single crown positioning regardless of the location of the implant, considering high scan precision with the healing abutment-scan body system. The duration of the chairside adjustments of crowns in the posterior maxilla may be longer than those in the anterior region.

The accuracy of intra-oral scanners in full arch implant rehabilitation: a narrative review

This narrative review aims to study the accuracy of different intra-oral scanner (IOS) devices already available on the market. The accuracy emerged during in vitro, in vivo and ex vivo studies made with IOS devices during the scan of a full arch implant rehabilitation that have been analysed to evaluate which device may be the most suitable in this clinical situation. The literature review was performed by searching topics and keywords using the PubMed and Medline databases, for example, 'digital workflow', 'full arch', 'full arch implant rehabilitation' and 'accuracy of IOS'. Inclusion and exclusion criteria for studies were: correct IMRAD (introduction, methods, results and discussion) structure; article with clear and detailed objectives; consistency of the articles with the purpose of the review; two-year range from the year of publication of the article; reproducible materials and methods; and correct follow-up. Most of the intra-oral scanners employed in vitro provided acceptable accuracy (below a threshold of 150 μm). The main parameters identified for their influence on precision were interim plant distance, body scan design, scanning pattern and operator experience. Even though literature is limited, significant differences emerged between the different models of intra-oral scanners evaluated in the studies considered within this review.

Full-arch restoration with the NEXUS IOS® system: A retrospective clinical evaluation of 37 restorations after a one year of follow-up

OBJECTIVES

Report the results with a novel workflow of digital restoration for completely edentulous patients with implant supported full arch fixed dental prostheses (ISFDP).

METHODS

This multicenter retrospective clinical study was based on the evaluation from a cohort of 29 patients restored with 37 ISFDP designed and manufactured from the data captured by a direct intraoral scan, using a novel full digital system (NEXUS IOS®, Osteon Medical, a Keystone Dental Group company, Melbourne, Australia). Data was collected over a 3-year period, in six different dental centers. This study reported on the clinical parameters including: precision of marginal fit, functional and aesthetic integration of Nexus ISFDP. All patients were followed for a period of one year post delivery. Implant survival, biologic and prosthetic complications were assessed, at one year. A statistical analysis was conducted.

RESULTS

All 37 ISFDP were deemed clinically acceptable on insertion. Implant survival at one year was 100 %. The biologic and prosthetic complications were minimal during the follow-up period.

CONCLUSIONS

ISFDP, designed and manufactured using the NEXUS IOS® system, are clinically acceptable, with a low incidence of complications at one year. Long-term clinical studies are needed.

STATEMENT OF CLINICAL RELEVANCE

Within the limitations of this study (retrospective design, small patient sample, limited follow-up) the NEXUS IOS® system seems to represent a viable solution for the restoration of completely edentulous patients with ISFDP, in a full digital workflow.

Accuracy of single-implant digital impression with various scanbody exposure levels at anterior and posterior regions

OBJECTIVES

This in vitro study aimed to evaluate the effect of the exposure heights of the scanbody on the accuracy of digital implant impressions at different positions.

METHODS

Four maxillary master models with one analog at the anterior and posterior region were fabricated by a 3-dimensional (3D) printer. The analogs were submerged from the gingival margin to ensure four exposure heights of the scanbody: 10, 8, 6, and 4 mm. . The master models were then scanned with D2000 dental laboratory scanner as the reference models. An intraoral scanner obtained ten test models for each group. After aligning the scanbody library file, the related files were imported into inspection software for superimposition by a local fit algorithm based on the adjacent teeth.

RESULTS

3D trueness was significantly decreased at 6 and 4 mm scanbody exposure at the anterior region. In comparison, a significant decrease was only seen at 4 mm scanbody exposure at the posterior region. 3D precision was significantly decreased at 4 mm scanbody exposure at both anterior and posterior regions.

CONCLUSION

The exposure height of the scanbody influenced the accuracy of the digital implant impression, according to the implant positions. Scanbody exposure of less than 6 mm at the anterior region and 4 mm scanbody exposure at the posterior region could lead to increased deviations, but still in the tolerance range.

CLINICAL SIGNIFICANCE

The scanbody exposure height less than 6 mm at the anterior region and 4 mm scanbody exposure height at the posterior region could lead to significantly increased deviations. Though these deviations may be still in the clinically acceptable range, caution should be taken.

Effect of novel prefabricated auxiliary devices attaching to scan bodies on the accuracy of intraoral scanning of complete-arch with multiple implants: An in-vitro study

OBJECTIVES

To examine the effect of novel prefabricated auxiliary devices with different geometric features called Scan Body Clasp (SBC) at different levels on the accuracy of intraoral scanning of complete-arch with multiple implants.

METHODS

An edentulous maxilla 4-implant model and SBCs with different geometric features (flat or curved) were fabricated by a 3D printer (AccuFab-C1s, 3DShining, Hangzhou, China). Test scans were performed using an intraoral scanner (Aoralscan 3, 3DShining, Hangzhou, China) software version 1.0.0.3104 under different scenarios: group A (CO), without any SBCs; group B&C (LC&HC), with curved SBCs adjacent to and away from the mucosa; group D&E (LF&HF), with flat SBCs adjacent to and away from the mucosa. 20 scans were done for each group (CO, LC, HC, LF and HF). Reference Scans were obtained by digitizing the model in group A using a dental laboratory scanner (D2000, 3Shape, Copenhagen, Denmark). The related files were imported into inspection software for trueness and precision assessment. Statistical analysis was performed with One-way ANOVA, Independent-Sample T test for trueness values. Kruskal-Wallis test and Mann-Whitney test were used to assess the precision values. The level of significance was set at α=0.05.

RESULTS

Groups with SBCs demonstrated trueness enhancement, among which LF revealed the best trueness. Significant differences were also found between LF and HC (p < .01), LF and HF (p < .001), LC and HF (p < .01). LF and HF showed precision enhancement. The best precision was LF, which was found to be more precise than LC (p < .001) and HC (p < .001). HF was more precise than LC (p < .001) and HC (p < .001).

CONCLUSIONS

Attaching the scan bodies with SBCs at different levels significantly influenced the scanning accuracy. The SBCs near the mucosa result in superior trueness, while the flat morphology benefits the precision.

CLINICAL SIGNIFICANCE

The results demonstrated the feasibility of the SBCs in enhancing intraoral complete-arch implant scanning accuracy. Among the configurations tested in the present study, low-level and flat surfaces of the artificial landmarks may be the potential pivotal elements to optimizing long-span scanning accuracy.

Evaluation of the accuracy of intraoral scanners for complete-arch scanning: A systematic review and network meta-analysis

OBJECTIVES

This network meta-analysis (NMA) aimed to compare the complete-arch scanning accuracy of different intraoral scanners (IOSs) to that of reference standard tessellation language (STL) files.

DATA

Studies comparing the trueness and precision of IOS STL files with those of reference STL scans for different arch types (dentate, edentulous, completely edentulous with implants, and partially edentulous with implants) were included in this study.

SOURCES

An electronic search of five databases restricted to the English Language was conducted in October 2021.

STUDY SELECTION

A total of 3,815 studies were identified, of which 114 were eligible for inclusion. After study selection and data extraction, pair-wise comparison and NMA were performed to define the accuracy of scanning for four arch subgroups using four outcomes (trueness and precision expressed as mean absolute deviation and root mean square values). Cochrane guidelines and the QUADAS-2 tool were used to assess the risk of bias. GRADE was used for certainty assessment.

RESULTS

Fifty-three articles were included in this NMA. Altogether, 26 IOSs were compared directly and indirectly in 10 network systems. The accuracy of IOSs scans were not significantly different from the reference scans for dentate arches (three IOSs), edentulous arches (three IOSs), and completely edentulous arches with implants (one IOS). The accuracy of the IOSs was significantly different from the reference scans for partially edentulous arches with implants. Significant accuracy differences were found between the IOSs, regardless of clinical scenarios.

CONCLUSIONS

The accuracy of complete-arch scanning by IOSs differs based on clinical scenarios.

CLINICAL SIGNIFICANCE

Different IOSs should be used according to the complete arch type.

Clinical performance of full-arch implant-supported fixed restorations made of monolithic zirconia luted to a titanium bar: A retrospective study with a mean follow-up of 16 months

OBJECTIVES

This retrospective case series aimed to evaluate the short-term clinical advantages and limitations of full-arch implant-supported restorations made of monolithic zirconia suprastructures passively luted to titanium bar infrastructures and to report the rate of complications within a minimum of 1-year follow-up.

MATERIALS AND METHODS

This study included 31 patients (19 men and 12 women) requiring full-arch implant-supported prostheses in the upper or lower jaw. The patients were treated using an entirely digital approach from implant planning and guided implant placement to prosthetic construction planning, design, and fabrication. Full-arch implant-supported monolithic zirconia suprastructures luted to prism-shaped titanium bars were used in all the cases. All the restorations were evaluated for biological and technical complications during fixed control appointments.

RESULTS

No implant failures or serviceable prosthetic complications were reported, and the prosthetic survival rate was 100%, with a follow-up duration ranging from 12 months to 20 months. In two cases, a fracture line was observed in the zirconia suprastructures, although it did not require any intervention.

CONCLUSIONS

After a 16-month mean follow-up period, the monolithic zirconia implant-supported full-arch fixed dental prostheses demonstrated no biological or technical complications. Further clinical studies with long-term results are required to confirm these reported outcomes.

CLINICAL SIGNIFICANCE

CAD-/CAM-milled monolithic zirconia structures passively luted to titanium bar infrastructures are a viable treatment option for full-arch restorations over implants, demonstrating 100% survival and success rates in the present study. The outcomes of this short-term retrospective study indicated high success in function, aesthetics, phonetics, and the ability to maintain flawless hygiene. However, the long-term results of restorations produced using the proposed technique should be considered before recommending this approach for routine clinical use.

Comparison of 3D accuracy of three different digital intraoral scanners in full-arch implant impressions

PURPOSE

This in vitro study aimed to evaluate the performance of digital intraoral scanners in a completely edentulous patient with angled and parallel implants.

MATERIALS AND METHODS

A total of 6 implants were placed at angulations of 0°, 5°, 0°, 0°, 15°, and 0° in regions #36, #34, #32, #42, #44, and #46, respectively, in a completely edentulous mandibular polyurethane model. Then, the study model created by connecting a scan body on the implants was scanned using a model scanner, and a 3D reference model was obtained. Three different intraoral scanners were used for digital impressions (PS group, TR group, and CS group, n = 10 in each group). The distances and angles between the scan bodies in these measurement groups were measured.

RESULTS

While the Primescan (PS) impression group had the highest accuracy with 38 µm, the values of 104 µm and 171 µm were obtained with Trios 4 IOSs (TR) and Carestream 3600 (CS), respectively (P = .001). The CS scanner constituted the impression group with the highest deviation in terms of accuracy. In terms of dimensional differences in the angle parameter, a statistically significant difference was revealed among the mean deviation angle values according to the scanners (P < .001). While the lowest angular deviation was obtained with the PS impression group with 0.185°, the values of 0.499° and 1.250° were obtained with TR and CS, respectively. No statistically significant difference was detected among the impression groups in terms of precision values (P > .05).

CONCLUSION

A statistically significant difference was found among the three digital impression groups upon comparing the impression accuracy. Implant angulation affected the impression accuracy of the digital impression groups. The most accurate impressions in terms of both distance and angle deviation were obtained with the PS impression group.

Assessment of guide fitting using an intra-oral scanner: An in vitro study

OBJECTIVES

The aim of this study was to evaluate the capacity of an intra-oral scanner (IOS) to assess the position of an endodontic guide in vitro.

METHODS

Fourteen extracted human teeth were placed into a maxillary model and scanned using computed tomography and a reference laboratory scanner. An ideal endodontic guide was then created and modified by adding defects of different thicknesses to simulate incorrect positions: 50 μm, 150 μm, 400 μm, and 1000 μm. For each thickness, guides were printed three times and each guide was scanned by three experimented operators using a Trios 4 IOS (3Shape, Copenhagen, Denmark). The 36 scans were compared using a best-fit alignment to the master model without defect to define the accuracy of the method and the positioning error.

RESULTS

The IOS presented a mean trueness of 1.28 μm (SD= 12.70) and a mean precision of 11.52 μm (SD= 62.17). Considering all sizes of defect, the mean measured position of the endodontic guide was highly correlated (R>0.99) with the expected position. Compared to the ideal guide, there was a mean linear deviation of 46.11 μm (SD= 23.21) and a mean angular deviation of 5.9° (SD= 1.2); this deviation was not influenced by the operator.

CONCLUSION

The present study found that an IOS had good performance to detect a positioning error of the endodontic guide in vitro.

CLINICAL SIGNIFICANCE

This new application of IOS has a promising potential in clinical practice to assist practitioners during the fitting of guides.

Accuracy (trueness and precision) of 3D printed orthodontic models finalized to clear aligners production, testing crowded and spaced dentition

BACKGROUND

The study's objective was to assess the accuracy (trueness and precision) of orthodontic models obtained from crowded and spaced dentition finalized for the production of clear aligners. Four 3D printers featuring different technologies and market segments were used for this purpose.

METHODS

Two digital master models were obtained from two patients featuring respectively crowded dentition (CM group) and diastema/edentulous spaces (DEM group). The 3D printers tested were: Form 3B (SLA technology, medium-professional segment), Vector 3SP (SLA technology, industrial segment), Asiga Pro 4K65 (DLP technology, high-professional segment), and Anycubic Photon M3 (LCD technology, entry-level segment). Each 3D printed model was scanned and superimposed onto the reference master model and digital deviation analysis was performed to assess the trueness and precision calculated as root mean square (RMS). All data were statistically examined to obtain intra-group and inter-groups comparisons(p 0.05).

RESULTS

In both CM and DEM groups, SLA 3D printers (Vector 3SP and Form 3B) showed lower trueness error compared to DLP/LCD technologies (Asiga Pro 4K65, Anycubic Photon M3) (p < 0.001). In general, the entry-level printer (Anycubic Photon M3) showed the greatest trueness error (p < 0.001). Comparing CM and DEM models generated with the same 3D printer, statistically significant differences were found only for Asiga Pro 4k65 and Anycubic Photon M3 printers (p > 0.05). Concerning data of precision, the DLP technology (Asiga Pro 4k65) showed lower error compared to the other 3D printers tested. The trueness and precision errors were within the accepted clinical error for clear aligner manufacturing (< 0.25 mm), with the entry-level 3D printer nearly reaching this value.

CONCLUSIONS

The accuracy of orthodontic models generated for clear aligners can be affected by different 3D printer technologies and anatomical characteristics of dental arches.

Predictability of intraoral scanner error for full-arch implant-supported rehabilitation

OBJECTIVES

The present study aimed to analyze the behaviors of three intraoral scanners (IOSs): evaluating the interdistance and axial inclination discrepancies in full-arch scans, predictable errors were searched.

MATERIALS AND METHODS

Six edentulous sample models with variable numbers of dental implants were used; reference data were obtained with a coordinate-measuring machine (CMM). Each IOS (i.e., Primescan, CS3600, and Trios3) performed 10 scans per model (180 total scans). The origin of each scan body was used as a reference point to measure interdistance lengths and axial inclinations. Precision and trueness of interdistance measurements and axial inclinations were evaluated to address error predictability. Bland-Altman analysis, followed by linear regression analysis and Friedman's test (plus Dunn's post hoc correction), was performed to evaluate the precision and trueness.

RESULTS

Regarding interdistance, Primescan showed the best precision (mean ± SD: 0.047 ± 0.020 mm), while Trios3 underestimated the reference value more than the others (p < 0.001) and had the worst performance (mean ± SD: -0.079 ± 0.048 mm). Concerning the inclination angle, Primescan and Trios3 tended to overestimate angle values, while CS3600 underestimated them. Primescan had fewer inclination angle outliers, but it tended to add 0.4-0.6° to the measurements.

CONCLUSIONS

IOSs showed predictable errors: they tended to overestimate or underestimate linear measurements and axial inclinations of scan bodies, one added 0.4-0.6° to the angle inclination values. In particular, they showed heteroscedasticity, a behavior probably related to the software or the device itself.

CLINICAL SIGNIFICANCE

IOSs showed predictable errors that could affect clinical success. When performing a scan or choosing a scanner, clinicians should clearly know their behaviors.

Evaluation of Marginal and Internal Fit of Ceramic Laminate Veneers Fabricated with Five Intraoral Scanners and Indirect Digitization

The long-term success of ceramic laminate veneers (CLVs) is influenced by the marginal and internal fit of the restorations. However, studies comparing the fit of CLVs using different intraoral scanners or the indirect digitization technique are lacking. The purpose of this study was therefore to assess the marginal and internal fit of CAD/CAM-milled CLVs using different intraoral scanners and the indirect digitalization technique. An ivorine typodont maxillary left-central incisor was prepared; the tooth and the neighboring teeth were scanned and used as a template to print ninety 3D partial models. Thereafter, ceramic laminate veneers (CLVs) (N = 90) were milled from IPS-Emax CAD blocks and divided into six equal groups (15 specimens each) according to the type of intraoral scanner (IOS), as follows: Omnicam IOS, SC3600 IOS, Trios 3 IOS, Emerald IOS, I500 IOS. Fifteen further CLVs were fabricated using the conventional indirect digitalization technique. After cementation on the resin dies and embedding in clear epoxy resin, specimens were sectioned inciso-gingivally and mesio-distally. At the incisal and cervical positions, the marginal discrepancy was measured and evaluated in addition to the internal gap at six locations using SEM (200×). Differences between gap measurements among the six groups were determined using ANOVA. Games-Howell multiple comparisons for homogenous variances and LSD multiple comparisons for non-homogenous variances were used with 95% confidence intervals. The significance level was set at 0.05. The lowest mean absolute marginal gap at the incisal margins (AMGI) was recorded for Omnicam group (203.28 ± 80.14) µm, while the highest mean absolute marginal gap at the cervical margins (AMGC) was recorded for Omnicam group (147.16 ± 59.78) µm. The mean AMGC was reported to be significantly different between the conventional technique (146.75 ± 38.43) µm and Trios 3 (91.86 ± (35.51) µm; p = 0.001) and between Emerald (112.37 ± (50.31) µm; p = 0.042) and I500 (86.95 ± (41.55) µm; p < 0.001). The mean MGI was found to be significantly different between the conventional technique (114.11 ± (43.45) µm and I500 group (186.99 ± (73.84) µm) only (p = 0.035). However, no significant differences were found in the mean MGI between all types of IOSs. The means of AMG and MG were significantly different at incisal or cervical areas between the conventional technique and IOSs and within the scanner groups (p > 0.05). Marginal gaps were higher in the incisal region compared to the cervical region with both the indirect digitization technique and the IOSs. Ceramic laminate veneers (CLVs) fabricated using IOSs produced overall internal and marginal fit adaptation results comparable to CLVs fabricated from the indirect digitalization method, and both techniques produced clinically acceptable results.

Effect of measurement techniques and operators on measured deviations in digital implant scans

OBJECTIVES

To evaluate the effect of different measurement techniques and operators on measured deviations in vitro implant scans.

METHODS

A 2-piece system that comprises a healing abutment (HA) and a scan body (SB) was mounted onto an implant at right first molar site of a polymethylmethacrylate mandibular dentate model. Model was digitized by using an industrial scanner (reference model scan, n = 1) and an intraoral scanner (test scan, n = 20). All standard tessellation language files were imported into a 3-dimensional analysis software and superimposed. Three operators with similar experience performed circle-based and point-based deviation analyses (n = 20). Deviations measured with different techniques were compared with paired samples t-test within each operator, while the reliability of the operators was assessed by using F-tests for both technqiues (α = 0.05).

RESULTS

Point-based technique resulted in lower deviations than circle-based technique for all operators (P = .001) with to higher reliability among operators (ICC = 0.438, P = .001). The correlation among the operators was nonsignificant when circle-based technique was used (ICC = 0.114, P = .189).

CONCLUSION

Lower deviations were detected with the point-based technique. In addition, different operators' measurements had higher correlation when point-based technique was used compared with circle-based technique.

CLINICAL SIGNIFICANCE

Point-based technique may be preferred over circle-based technique for research studies on scan accuracy of implants, given its higher reliability. The accuracy of measured deviations may increase if the number of planes are increased, which can facilitate point generation at different surfaces of the scan body.

Effect of intraoral scanner and fixed partial denture situation on the scan accuracy of multiple implants: An in vitro study

BACKGROUND

Accuracy of intraoral implant scans may be affected by the region of the implant and the type of the intraoral scanner (IOSs). However, there is limited knowledge on the scan accuracy of multiple implants placed for an implant-supported fixed partial denture (FPD) in different partially edentulous situations when digitized by using different IOSs.

PURPOSE

To investigate the effect of IOS and FPD situation on the scan accuracy of two implants when partial-arch scans were performed.

MATERIALS AND METHODS

Tissue level implants were placed in 3 maxillary models with implant spaces either at right first premolar and right first molar sites (Model 1, 3-unit FPD), at right canine and right first molar sites (Model 2, 4-unit FPD), or at lateral incisor sites (Model 3, 4-unit FPD). Reference standard tessellation language (STL) files of the models were generated by using an optical scanner (ATOS Capsule 200MV120). Two IOSs (CEREC Primescan [CP] and TRIOS 3 [TR]) were used to perform partial-arch scans (test-scans) of each model (n = 14), which were exported in STL format. A metrology-grade analysis software (GOM Inspect 2018) was used to superimpose test-scan STLs over the reference STL to calculate 3D distance, inter-implant distance, and angular (mesiodistal and buccopalatal) deviations. Trueness and precision analyses were performed by using bootstrap analysis of variance followed by Welch tests with Holm correction (α = 0.05).

RESULTS

Trueness of the scans was affected by IOS and FPD situation when 3D distance deviations were considered, while inter-implant distance, mesiodistal angular, and buccopalatal angular deviations were only affected by the FPD situation (p < 0.001). Scan precision was affected by the interaction between the IOSs and the FPD situation when 3D distance and buccopalatal angular deviations were concerned, while IOSs and FPD situation were effective when all deviations were concerned (p≤ 0.001). When 3D distance deviations were considered, CP scans had higher accuracy TR scans in Models 1 and 3 (p ≤ 0.002), and the Model 1 scans had the highest accuracy (p < 0.001). When inter-implant distance deviations were considered, Model 1 scans had the highest accuracy with CP and higher accuracy than Model 2 when TR was used (p ≤ 0.030). When mesiodistal angular deviations were considered, Model 1 scans had the highest accuracy (p ≤ 0.040). When buccopalatal angular deviations were considered, Model 1 scans had the highest accuracy among models when CP was used (p ≤ 0.020).

CONCLUSIONS

Posterior 3-unit fixed partial denture implant scans, CP scans, and combination of these two factors had accuracy either similar to or better than their tested counterparts.

Effect of material type, torque value, and sterilization on linear displacements of a scan body: An in vitro study

BACKGROUND

There is limited knowledge on the effect of scan body (SB) material type, torque value, and sterilization on linear displacements of implant SBs.

PURPOSE

To evaluate the effect of material type, torque value, and sterilization on linear displacements of SBs during screw tightening by using digital image correlation (DIC) analysis.

MATERIALS AND METHODS

One polyetheretherketone (PEEK, Zfx Intraoral Scan Body) and one titanium SB (Ti, MPS Zimmer Scanbody R1410) were tightened with 5 Ncm torque on two implants (Zimmer TSV ⌀4.7 mm) by using a digital torque limiting device. SBs' initial spatial positions relative to the implants were recorded by using 3D DIC technique. Measurements were repeated after initially increasing torque value to 10 Ncm and then to 15 Ncm, and these steps were repeated for a total of 10 PEEK and 10 Ti SBs on both implants (n = 20). All SBs were then sterilized 25 times by using an autoclave (STATIM 5000 S G4) according to manufacturer's recommendations and all measurements were repeated. Linear displacements on three axes were calculated for each SB with increasing torque values (from 5 to 10 Ncm and from 10 to 15 Ncm) before and after sterilization. SB displacements within each torque value-sterilization pair were compared by using Mann-Whitney U test, whereas Wilcoxon signed-rank test was used to compare SB displacements within each material-torque value pair between conditions and within each material-sterilization pair between torque values (α = 0.05).

RESULTS

On x-axis, PEEK SBs had higher displacements than Ti SBs (p < 0.001), whereas sterilization (p ≤ 0.028) and 15 Ncm torque application (p ≤ 0.006) led to higher displacements of PEEK SBs. On y-axis, PEEK SBs had higher displacements than Ti SBs with 15 Ncm torque application (p ≤ 0.033). A total of 15 Ncm torque-applied PEEK SBs and 10 Ncm torque-applied Ti SBs had higher displacements after sterilization (p ≤ 0.028). Application of 15 Ncm torque led to higher displacements regardless of the material (p ≤ 0.002). On z-axis, PEEK SBs had higher displacements (p ≤ 0.015), except for 10 Ncm torque-applied sterilized SBs (p = 0.102). With 10 Ncm torque application, sterilization decreased the displacement values of PEEK SBs (p = 0.044). Greater displacements were observed with 10 Ncm torque-applied Ti SBs before sterilization and 15 Ncm torque-applied PEEK SBs after sterilization (p ≤ 0.033).

CONCLUSIONS

Axial displacement of SBs was affected by material type, torque value, and sterilization. Ti SBs mostly had lower displacements than PEEK SBs. Application of 15 Ncm torque to tested PEEK SBs should be refrained from and a calibrated tightening tool may enable the application of 10 Ncm or lower torque values for lower displacements. Sterilization generally increased PEEK SB displacements.

In vitro comparison of five desktop scanners and an industrial scanner in the evaluation of an intraoral scanner accuracy

OBJECTIVES

The study aimed to compare the precision of ATOS industrial, 3ShapeE4, MeditT710, CeramillMap400, CSNeo, PlanScanLab desktop, and Mediti700 intraoral scanners. The second aim was to compare the trueness of Mediti700 assessed by ATOS and desktop scanners.

METHODS

Four plastic dentate models with 7-12 abutments prepared for complete arch fixed dentures were scanned by all scanners three times. Scans were segmented to retain only the abutments. The precision and trueness were calculated by superimposing scans with the best-fit algorithm. The mean absolute distance was calculated between the scan surfaces. The precision was calculated based on the 12 repeats. Trueness was evaluated by superimposing the desktop and IOS scans to the industrial scans. IOS was also aligned with the two most accurate desktop scanners.

RESULTS

The precision of 3ShapeE4 and MeditT710 (3-4μm) was only slightly lower than that of ATOS (1.7μm, p<0.001) and significantly higher than CeramillMap400, CSNeo, and PlanScanLab (6-10 μm, p<0.001). The trueness was the highest for the 3Shape E4 (12-13 μm) and Medit T710 (13-16 μm) without significant difference. They were significantly better than CeramillMap400, CSNeo, and PlanScanLab (22-31μm, p<0.001). Accordingly, the Mediti700 trueness was evaluated by ATOS, 3ShapeE4, and MeditT710. The three trueness was not significantly different; ATOS (23-26 μm), 3Shape E4 (22-25 μm), and Medit T710 (20-23 μm).

CONCLUSIONS

All desktop scanners had the acceptable accuracy required for a complete arch-fixed prosthesis. The 3Shape E4 and the Medit T710 might be used as reference scanners for studying IOS accuracy.

CLINICAL SIGNIFICANCE

3ShapeE4, MeditT710, CeramillMap400, CSNeo, PlanScanLab laboratory, and Mediti700 intraoral scanners can be used for the prosthetic workflow in a complete arch. 3ShapeE4 and the MeditT710 could be used to test the accuracy of various phases of a laboratory workflow, replacing the industrial scanners.

In Vitro Trueness and Precision of Intraoral Scanners in a Four-Implant Complete-Arch Model

(1) Background: New intraoral (IOS) and laboratory scanners appear in the market and their trueness and precision have not been compared. (2) Methods: Seven IOS and two laboratory scanners were used to scan a mandibular edentulous model with four parallel internal hexagon implant analogues and PEEK scan bodies. Digital models in Standard Tessellation Language (STL) were created. The master model with the scan bodies was scanned (×10) with a computerized numerical control 3D Coordinate Measuring Machine (CMM). The short (distances of adjacent scan posts) and long distances (distances of the scan posts with non-adjacent sites in the arch) among the centroids of the four analogues were calculated using CMM special software. Trueness (comparisons with the master model) and precision (intragroup comparisons) were statistically compared with ANOVA, chi-square and Tukey tests. (3) Results: Laboratory scanners had the best trueness and precision compared to all IOSs for long distances. Only iTero (Align Technologies Inc., Milpitas, CA, USA) had comparable trueness with one laboratory scanner in short and long distances. For short distances, CS3600 (Carestream Health, Inc., Rochester, NY, USA), Omnicam, Primescan (Sirona Dental Sys-tems GmbH, Bens-heim, Germany) and TRIOS 4 (3Shape A/S, Copen-hagen, Denmark) had similar trueness to one laboratory scanner. From those, only Omnicam and Primescan had similar precision as the same laboratory scanner. Most IOSs seem to work better for smaller distances and are less precise in cross-arch distances. (4) Conclusions: The laboratory scanners showed significantly higher trueness and precision than all IOSs tested for the long-distance group; for the short distance, some IOSs were not different in trueness and precision than the laboratory scanners.

Performance of high-translucent zirconia CAD/CAM fixed dental prostheses using a digital workflow: A clinical study up to 6 years

Background/purpose

Zirconia has recently become a popular material for fixed restorations. The purpose of this study was to use a digital workflow to fabricate monolithic zirconia fixed dental prostheses (FDPs) and assess the connection between variable connector sizes compared to their clinical performance.

Materials and methods

Clinicians evaluated monolithic zirconia FDPs in 58 patients. After definitive impressions were made, stone casts were obtained. The stone casts were scanned to a standard triangle language (STL) file. A digital wax up was fabricated, and corresponding provisional restorations were milled. Final FDPs were fabricated from a high-translucent zirconia material. During digital fabrication, the connector area of each FDP was recorded while meticulous attention was paid to ensure that the connector cross-sectional area was ≥9 mm² for the 3-unit restorations (pontic to retainer) and ≥12 mm² for the 4-unit restorations (pontic to pontic). Biological an technical outcomes of the FDPs were performed at 1 week, 6 months and then annually for 6 consecutive years.

Results

A total of 23 men and 35 women received a total of 63 full-contour zirconia FDPs in the posterior regions and were observed for a time period ranging between 50 and 70 months. No decementation occurred and no caries were detected during the observation period, however signs of gingivitis were detected in 4 patients. The dimension of the connector areas was 12 mm² in the two broken 4-unit FDPs.

Conclusion

The results of this study suggest that the use of digital scanning and milling to fabricate monolithic zirconia FDPs of posterior regions may be an acceptable alternative restorative approach to traditional metal-ceramic restorations.

Retentive design of a small surgical guide for implant surgery: An in-vitro study

OBJECTIVES

Instability of the surgical guide is an overlooked factor that can result in a difference between the planned and the actual positions of an implant. Our aim was to compare the stability of the retentive surgical guide (RSG) with a conventional surgical guide (CSG) in an in-vitro experiment.

METHODS

A platform to evaluate the stability of the surgical guide was designed using 3D-modelling software (Meshmixer 3.5, Autodesk). Imaging data from 15 patients with a single missing tooth were used to plan the virtual implant. Two surgical guides were designed (Blue Sky Plan 4.8, Blue Sky Bio) and 3D printed (Form2, Dental SG resin, Formlabs) for each case: the CSG with the default, predetermined software settings, and the RSG, designed on a dental model with a 0.1-mm undercut and altered production parameters (reduced guide-to-teeth offset of 0.07 mm, reduced guide thickness of 2.3 mm and a retentive clasp in a marginal area). The dental models were reproducibly secured on the testing platform using a digital force gauge, and the surgical guides were positioned. An increasing force of 0.1 N, 1 N, 2.5 N, and 5 N was sequentially applied from the buccal and the oral directions to the surgical guide via a drill handle. For each force, either the magnitude of the guide's displacement was captured with an intra-oral scanner (CEREC Omnicam AC, Dentsply Sirona; software version: SW 4.5.2) or the dislodgement of the guide was recorded. Scans were imported for analysis (GOM Inspect 2018, GOM GmbH), and library files of the surgical guides and implants were superimposed as a joined complex. The deviation of the implant's position was calculated from the displacement of the guide's position RESULTS: Three-way repeated measures using ANOVA revealed a more significant guide displacement and virtually projected implant deviation in the CSG group than the RSG group and with increasing force in all the deviation parameters. Both groups showed greater resistance to the displacement with the force applied from the oral direction than the buccal direction. The application of the force in the buccal direction resulted in guide dislodgements of 13% and 0% for the CSG and RSG, respectively. In the oral direction, the dislodgement rates were 33% and 7% for the CSG and RSG, respectively.

CONCLUSIONS

Within the limitations of this study, the retentive design increased the stability of the surgical guide and, consequently, the accuracy of the virtually projected implants in comparison to the conventional surgical guide designed using the default settings. Clinical trials are needed to confirm its advantages in clinical use.

CLINICAL SIGNIFICANCE

With a simple modification to the design, the surgical guide retention provided greater stability, with smaller deviations under loading; this resulted in improved implant precision parameters without requiring additional materials or software. Further studies are needed to assess the clinical feasibility of this surgical guide with improved retention and function.

Accuracy of Digital Impressions at Varying Implant Depths: An In Vitro Study

PURPOSE

Implants placed at variable depths may vary the amount of visible scannable surface of a scan body. Intraoral scanner technology uses advanced optical principles to record the surface of the scan body to accurately capture the implant position. The purpose of this study is to investigate the effect implant placement depth has on the accuracy of digital implant impressions using an intraoral scanner.

MATERIALS AND METHODS

A partially edentulous gypsum master model was fabricated to allow the positioning of a single implant analog at different depths. Four groups were created based on the planned implant depths of 7, 6, 3, and 0 mm and corresponding visibility of the scan body at 2, 3, 6, and 9 mm. The model was digitized with a laboratory scanner for the reference scan and with an intraoral scanner to generate 15 test scans per group, with a total of 60 scans. The test scans were superimposed onto the reference scan using the best fit algorithm to analyze and measure the positional (dXYZ) and angular deviation (d⍬) of the scan body using three-dimensional metrology software. Statistical analysis was performed using a one-way ANOVA and pairwise comparison was done with a Tukey-Kramer HSD test (α = 0.05).

RESULTS

The one-way ANOVA of the groups for the dXYZ and dθ parameters was statistically significant (F_3,56 = 11.45, p < 0.001, F_3,56 = 24.04, p < 0.001). Group D (9 mm) showed the least positional deviation at 38.41 μm (95% CI 30.26; 46.56) and the least angular deviation of 0.17° (95% CI 0.12; 0.21). Group A (2 mm) showed the greatest positional deviation of 77.17 μm (95% CI 65.23; 89.11) and greatest angular deviation of 0.84° (95% CI 0.65; 1.03). The positional and angular deviation increased with increased implant depth.

CONCLUSIONS

The accuracy of digital impressions is influenced by the implant depth and the amount of visibility of the scan body. The trueness and precision are highest when the implant is placed at 0 mm depth with complete visibility of the scan body and decreases with subgingival implant placement.

A guide for maximizing the accuracy of intraoral digital scans. Part 1: Operator factors

OBJECTIVES

To describe the factors related to the operator skills and decisions that influence the scanning accuracy of intraoral scanners (IOSs). A new classification for these factors is proposed to facilitate dental professionals' decision making when using IOSs and maximize the accuracy and reliability of intraoral digital scans.

OVERVIEW

Each IOS system is limited by the hardware and software characteristics of the selected device. The operator decisions that can influence the accuracy of IOSs include the scanning technology and system selection, scanning head size, calibration, scanning distance, exposure of the IOS to ambient temperature changes, ambient humidity, ambient lighting conditions, operator experience, scanning pattern, extension of the scan, cutting off, rescanning, and overlapping procedures.

CONCLUSIONS

The knowledge and understanding of the operator factors that impact scanning accuracy of IOSs is a fundamental element for maximizing the accuracy of IOSs and for successfully integrating IOSs in daily practices.

CLINICAL SIGNIFICANCE

Operator skills and clinical decisions significantly impact intraoral scanning accuracy. Dental professionals must know and understand these influencing operator factors for maximizing the accuracy of IOSs.

In vivo trueness and precision of full-arch implant scans using intraoral scanners with three different acquisition protocols

OBJECTIVES

To evaluate an in situ reference acquisition method for implant positions in complete edentulous maxillae using an industrial scanner and allowing for in vivo trueness analysis of the restorative workflow. To assess in vivo trueness and precision of intraoral scanners (IOS) using different acquisition protocols. Furthermore, to compare IOS trueness with impression-based models and implant-supported fixed dentures (IFD) in a parallel study on the same cohort using the same in situ reference scan.

METHODS

Six scan-bodies mounted to maxillary implants in five subjects were reference scanned (REF) using an industrial scanner. Subjects were scanned with IOS three times using three different protocols: control (CT), dental floss assisted (DF), and acrylic splint (SP). CAD-files of scan-bodies with inter-aligned analogues were geometry-aligned to REF, and SP. Scan-bodies were aligned to CT and DF in proprietary dental laboratory software and exported with analogue positions. Resulting six CAD-analogues per scan were Globally Aligned using a consistent geometry-based alignment. Deviations were computed after a Reference Point System Alignment at the implant/prosthetic platform for Cartesian axes with a linear Resultant.

RESULTS

Resultant trueness was CT: 41±11 µm, DF: 49±22 µm, SP: 55±8 µm. Resultant precision was CT: 48±7 µm, DF: 50±7 µm, SP: 45±6 µm.

CONCLUSIONS

This method is applicable for assessing trueness of maxillary full-arch implant scans in vivo. The CT protocol was most accurate. CT trueness showed no difference to digitised impression-based models in parallel study. CT was more accurate than IFD in a parallel study. CT displayed similar numerical trueness as existing in vitro studies.

CLINICAL SIGNIFICANCE

Using IOS to acquire full-arch implant scans is controversial. The modified protocol in this pilot shows promising results in the maxilla where great care was taken to manage non-attached tissues when a modified scanning pattern was used. However, other IOS may show varying results in vivo. A completed scan does not necessarily equate to an accurate scan.

A method based on 3D affine alignment for the quantification of palatal expansion

INTRODUCTION

The current methodologies to quantify the palatal expansion are based on a preliminary rigid superimposition of 3D digital models representing the status of a given patient at different times. A new method based on affine alignment is proposed and compared to the gold standard, leading to the automatic analysis of 3-dimensional structural changes and to a simple numeric quantification of overall expansion vector and a better alignment of the digital models.

MATERIALS AND METHODS

40 digital models (timing span delta 25.8 ± 12.5 months) from young patients (mean age 10.7 ± 2.6) treated with two different palatal expansion techniques (20 subjects with RME-Rapid Maxillary Expander, and 20 subjects with NiTiSE, NiTi self-expander) were superimposed with the new affine alignment technique implemented as an extension package of the open-source MeshLab, from a golden standard starting point of rigid alignment. The results were then compared.

RESULTS

The new measurement function indicates a mean expansion expressed in a single numeric value of 9.3%, 10.3% for the RME group and 8.4% for the NiTiSE group respectively. The comparison with the golden standard showed a decrease to the average error from 0.91 mm to 0.58 mm.

CONCLUSIONS

Affine alignment improves the current perspective of structural change quantification in the specific group of growing patients treated with palatal expanders giving the clinician useful information on the 3-dimensional morphological changes.

Trueness of full-arch dental models obtained by digital and conventional impression techniques: an in vivo study

The aim of this study was to compare the trueness of complete- and partial-arch impressions obtained using conventional impression materials and intraoral scanners in vivo. Full-arch impressions were taken using polyether and polyvinylsiloxane. Gypsum casts were digitized using a laboratory scanner (IM, AF). Casts obtained from polyether impressions were also scanned using an industrial blue light scanner to construct 3D reference models. Intraoral scanning was performed using CEREC Omnicam (CO) and Trios 3 (TR). Surface matching software (Atos Professional) enabled to determine the mean deviations (mean distances) from the reference casts. Statistically significant discrepancies were calculated using the Wilcoxon signed-rank test. The mean distance for trueness ranged from 0.005 mm (TR) to 0.023 mm (IM) for the full arch, from 0.001 mm (CO) to 0.068 mm (IM) for the anterior segment, and from 0.019 mm (AF) to 0.042 mm (IM) for the posterior segment. Comparing the anterior vs. the posterior segment, significantly less deviations were observed for anterior with CO (p < 0.001) and TR (p < 0.001). Full-arch comparisons revealed significant differences between AF vs. IM (p = 0.014), IM vs. CO (p = 0.002), and IM vs. TR (p = 0.001). Full-arch trueness was comparable when using Affinis and the two intraoral scanners CEREC Omnicam and Trios 3. The digital impression devices yielded higher local deviations within the complete arch. Digital impressions of the complete arch are a suitable and reliable alternative to conventional impressions. However, they should be used with caution in the posterior region.Trial registration: Registration number at the German Clinical Trial Register (04.02.2022): DRKS00027988 ( https://trialsearch.who.int/ ).