Accuracy of photogrammetry, intraoral scanning, and conventional impression techniques for complete-arch implant rehabilitation: an in vitro comparative study

Effect of a Novel 'Scan Body' on the In Vitro Scanning Accuracy of Full-Arch Implant Impressions

OBJECTIVE

This in vitro study aimed to determine whether a newly designed arcuate scan body can improve intraoral scanning accuracy for implant rehabilitation of edentulous jaws.

MATERIAL AND METHODS

A master model containing 4 implant abutment replicas was fabricated and digitized with different scan bodies using an intraoral scanner. Four types of scan bodies were evaluated: original scan bodies (group OS), computer-aided design and computer-aided manufacturing (CAD/CAM) scan bodies without extension (group CS), CAD/CAM scan bodies with straight extension (group CSS), and CAD/CAM scan bodies with arcuate extension (group CSA). Conventional splinted open-tray impressions (group CI) were used as controls. The master model and the poured casts were digitized using a laboratory scanner. Impressions were repeated 10 times each in 5 groups. Scans in standard tessellation language format were exported to reverse engineering software and root mean square (RMS) values were used for trueness and precision assessments. In each group, 45 RMS values were acquired for precision evaluation and 10 RMS values were obtained for trueness assessment. Statistical evaluation was performed with the Kruskal-Wallis test and Dunn-Bonferroni test (α = 0.05).

RESULTS

The median trueness values were 41.40, 55.95, 39.80, 39.75, and 22.30 μm for group OS, CS, CSS, CSA, and CI, respectively. CI showed better trueness than OS (P = .020), CS (P < .001), and CSS (P = .035). The median precisions for group OS, CS, CSS, CSA, and CI were 47.40, 51.50, 43.90, 25.20, and 24.60 μm. respectively. The precision of CSA and CI were higher than OS (P < .001), CS (P < .001), and CSS (P < .001). Between CI and CSA, there was no significant difference (P = 1.000).

CONCLUSIONS

For full-arch implant rehabilitation, the scan body with arcuate extension could improve the intraoral scanning precision and showed similar 3-dimensional discrepancy compared to conventional splinted open-tray impressions.

Influence of splinting scan bodies or incorporating three-dimensionally printed scan aids on the trueness of complete arch digital scans

STATEMENT OF PROBLEM

Studies are sparse on how splinting scan bodies or incorporating 3-dimensionally (3D) printed scan aids influence the trueness of complete arch digital scans.

PURPOSE

The purpose of this in vitro study was to compare the trueness of multisite implant recordings obtained using 6 different methods on an edentulous mandible.

MATERIAL AND METHODS

A definitive cast of an edentulous mandible with 4 multi-unit analogs placed at different angles and interanalog distances was extraorally scanned, and the resulting data were saved as a reference file. To obtain experimental files, 6 distinct methods were used: conventional impression with splinted open-tray impression copings (IC), intraoral scanning (IOS) without splinting scan bodies or using any scan aids (SB), IOS with pattern resin-splinted scan bodies (PR), IOS with composite resin-splinted scan bodies (CR), IOS with 3D printed custom scan bodies (CSB), and IOS with 3D printed auxiliary apparatus (AA). The experimental files were aligned to the reference file in a metrology software program. The 3D comparison algorithm was run to quantify the root mean square estimate error (RMS). Scan bodies in the files were converted to hollow virtual cylinders, and the Cartesian coordinates of the lines passing through the centers of these cylinders were recorded to analyze angular (AD) and linear distortion (LD). LD was further analyzed along the x (∆X), y (∆Y), and z axes (∆Z). One-way ANOVAs with the Tukey HSD test were used for statistical analysis (α=.05).

RESULTS

AD at all sites, LD at all sites, and the RMS error showed significant differences (P<.05). The IC group showed the lowest AD values across all sites, followed by the AA, CSB, PR, CR, and SB groups. The SB group had the greatest LD values at all sites, while the IC group indicated the lowest LD values at all sites except the left anterior site. In terms of 3D distortions, the SB group had the largest RMS value, whereas the IC group showed the lowest RMS value. ∆X, ∆Y, and ∆Z values also showed significant differences at all sites (P<.001) except for the ∆Z values at the right anterior site (P=.194). The highest mean ∆X, ∆Y, and ∆Z values were recorded in the SB group except for the ∆Z measurement of the left posterior site.

CONCLUSIONS

The IC group outperformed the other groups. The AA group exhibited distortion comparable with that of the IC group. Splinting scan bodies or using scan aids enhanced the trueness.

Accuracy of traditional open-tray impression, stereophotogrammetry, and intraoral scanning with prefabricated aids for implant-supported complete arch prostheses with different implant distributions: An in vitro study

STATEMENT OF PROBLEM

Conventional impression techniques for complete arch implant-supported fixed dental prostheses (CIFDPs) are technique sensitive. Stereophotogrammetry (SPG) and intraoral scanning (IOS) may offer alternatives to conventional impression making.

PURPOSE

The purpose of this in vitro study was to assess the accuracy and passive fit of IOS with prefabricated aids, SPG, and open tray impression (OI) for CIFDPs with different implant distributions.

MATERIAL AND METHODS

Three definitive casts with 4 parallel implants (4-PARA), 4 inclined implants (4-INCL), and 6 parallel implants (6-PARA) were fabricated. Three recording techniques were tested: IOS with prefabricated aids, SPG, and OI. The best and the worst scans were selected to fabricate 18 milled aluminum alloy frameworks. The trueness and precision of distance deviation (∆td and ∆pd), angular deviation (∆tθand ∆pθ), root mean square errors (∆tRMS for ∆pRMS), and passive fit score of frameworks were recorded. Two-way ANOVA was applied.

RESULTS

SPG showed the best trueness and precision (95%CI of ∆td/∆tθ/∆tRMS, 31 to 39 µm, 0.22 to 0.28 degrees, 20 to 23 µm; 95%CI of ∆pd/∆pθ/∆pRMS, 9 to 11 µm, 0.06 to 0.08 degrees, 8 to 10 µm), followed by OI (61 to 83 µm, 0.33 to 0.48 degrees, 28 to 48 µm; 66 to 81 µm, 0.29 to 0.38 degrees, 32 to 41 µm) and IOS (143 to 193 µm, 0.37 to 0.50 degrees, 81 to 96 µm; 89 to 111 µm, 0.27 to 0.31 degrees, 51 to 62 µm). Tilted implants were associated with increased distance deviation. Increased implant number was associated with improved recording precision. The passive fit of frameworks was negatively correlated with the RMS error, and the correlation coefficient was -0.65 (P=.003).

CONCLUSIONS

SPG had the best accuracy. Implant distributions affected implant precision. The RMS error can be used to evaluate the passive fit of frameworks.

Accuracy of different digital acquisition methods in complete arch implant-supported prostheses: An in vitro study

STATEMENT OF PROBLEM

Digital methods such as intraoral scanners for recording the location of implants supporting complete arch prostheses have limitations. Photogrammetry devices should be able to digitize implant positions accurately, but standardized comparisons between different digital acquisition methods are lacking.

PURPOSE

The purpose of this in vitro study was to compare the repeatability of different digital acquisition methods for complete arch prostheses supported by 6 and 4 implants.

MATERIAL AND METHODS

A master cast was created with 6 and 4 dental implants with multiunit abutments to obtain the master digital casts. The evaluated devices were the industrial high-resolution 12-megapixel scanner (reference) Atos Compact Scan 12M (GOM), the laboratory scanners D2000 (3Shape A/S) and S900 Arti (Zirkonzahn), the photogrammetry devices iCam (iMetric4D) and PIC (PIC Dental), and the intraoral scanners TRIOS 3 (3Shape A/S) and iTero Element 5D (Align Technology). The resulting files were imported to a computer-aided design software program (exocad GmbH) to obtain the implant replicas as standard tessellation language (STL) files. These files were imported into a software program (Geomagic Control X) and superimposed per group through the best-fit algorithm to determine repeatability, defined as the closeness of agreement between each group's scanned results as root mean square (RMS) values. The normality of distribution was tested by the Shapiro-Wilk normality test, and the Kruskal-Wallis test with adjustment with the Bonferroni correction method was used accordingly (α=.05).

RESULTS

The repeatability means and 95% confidence intervals for the 4 implant scans were: 1.07 µm (0.86; 1.29) for GOM, 2.05 µm (1.89; 2.21) for D2000, 3.61 µm (3.23; 3.99) for S900, 7.01 µm (6.11; 7.91) for iCam, 5.18 µm (4.6; 5.76) for PIC, 20.52 µm (18.33; 22.72) for TRIOS 3, and 20.5 µm (17.37; 23.63) for iTero. Statistically significant differences were found between devices, except for iCam versus PIC, GOM versus S900, iCam versus D2000, PIC versus D2000, and TRIOS 3 versus iTero. The repeatability means and 95% confidence intervals for the 6 implant groups were: 1.36 µm (1.08; 1.65) for GOM, 3.17 µm (3.01; 3.33) for D2000, 2.15 µm (2.04; 2.25) for S900, 8.67 µm (8.06; 9.28) for iCam, 13.88 µm (12.62; 15.14) for PIC, 40.32 µm (36.29; 44.36) for TRIOS 3, and 38.86 µm (34.01; 43.71) for iTero. Statistically significant differences were detected between devices, except for S900 versus GOM, PIC versus iCam, and iTero versus TRIOS 3.

CONCLUSIONS

The results suggest that photogrammetry could be a suitable alternative for recording implant locations of complete arch prostheses supported by 4 or 6 implants, with better repeatability than intraoral scanners. Increasing the number of implants decreased the repeatability of every device tested except the laboratory scanners.

Accuracy of Complete-Arch Scans Obtained by Intraoral Scanner and Smartphone Three-Dimensional Scanning Applications With Different Smartphone Position Setups: An In Vitro Study

INTRODUCTION

The high cost of intraoral scanners (IOS) for complete-arch scans makes them less accessible for many dental practitioners. As a viable alternative, smartphone scanner applications (SMP) provide comparable scanning capabilities at a significantly low cost. However, there is limited data on the accuracy of SMP, especially when used in various smartphone positions. This study aimed to compare the three-dimensional (3D) and linear accuracy of complete-arch scans acquired by an IOS and SMP (KIRI Engine, KIRI Innovations, Guangdong, China) at three shooting angles (0°, 45°, and 90° for SMP_3A) and two shooting angles (30° and 60° for SMP_2A).

METHODS

A stone dental cast was scanned with a laboratory scanner as a reference, with 11 scans performed by an IOS, SMP_2A, and SMP_3A. In 3D analysis, trueness and precision were evaluated through superimposition with the reference scan and within each group, respectively, using the best-fit algorithm of Geomagic Wrap software (3D Systems, Inc., Rock Hill, SC). Trueness in linear discrepancy was assessed by comparing the occlusal-cervical and mesiodistal dimensions of reference teeth (canine, premolar, and molar), intercanine width, and intermolar width on the digital casts to measurements of the stone cast, while precision was measured using the coefficient of variance. Differences between groups were analyzed using the Friedman test, followed by the Dunn-Bonferroni post hoc test with a significance level set at 0.05.

RESULTS

IOS exhibited significantly lower trueness than SMP_2A (p = 0.003) with significantly greater width discrepancies on canines (p = 0.001) and molars (p < 0.001). Discrepancy patterns differed among the three scanning methods. The IOS showed greater discrepancies on the occlusal surfaces of posterior teeth. While SMP_3A demonstrated higher variation on the palatal surfaces and interproximal areas of posterior teeth. For precision, SMP_3A (p = 0.028) and SMP_2A (p = 0.003) showed a significantly lower precision in 3D analysis, but a comparable reproducibility in linear measurement to IOS.

CONCLUSION

TRIOS IOS (3Shape, Copenhagen, Denmark) exhibited lower trueness in 3D and linear accuracy analyses for complete-arch scans. The positions of the smartphone significantly enhanced trueness at the undercut region. SMP_2A and SMP_3A can be a potential alternative for precise linear measurement in complete-arch scans with selective use.

Accuracy of edentulous full-arch implant impression: An in vitro comparison between conventional impression, intraoral scan with and without splinting, and photogrammetry

OBJECTIVES

The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry.

MATERIALS AND METHODS

An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations.

RESULTS

Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05).

CONCLUSIONS

Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

Utilization of 3D evaluation for assessing selective caries removal practice in pre-clinical dental students: a pilot study

BACKGROUND

Practicing and assessment of selective caries removal techniques in dental students remain challenges in many dental schools. The aim of this study was to utilize a 3D assessment technique, within a designated acceptable range of deviation, to evaluate the tendency of dental students in performing selective caries removal (SCR). The correlation between 3D assessment results and the conventional rubric rated by an instructor was also determined.

METHODS

Fifth-year dental students (n = 61) performed the SCR task on 3D-printed teeth containing simulated deep caries lesions in occlusal and proximal surfaces. One instructor assessed the results using a conventional analytic rubric. The excavated teeth were additionally evaluated using 3D analysis software with the designated acceptable range of deviations (± 0.5 mm) from the standard cavities. The average root mean square (RMS) value, representing the deviation between student-prepared cavities and the predefined standard cavities, was recorded. A tendency towards over-excavation was defined for RMS values > 0.5 mm, and towards under-excavation for RMS values < 0.5 mm.

RESULTS

The mean (min-max) of RMS was 0.27 (0.18-0.40) for occlusal and 0.29 (0.20-0.57)for proximal cavities. A tendency of dental students toward over-excavation was observed in both occlusal (74%) and proximal cavities (87%). There was a moderate negative correlation between the RMS values and the traditional rubric scores for both occlusal (R2 = 0.148, P = 0.002) and proximal cavities (R2 = 0.107, P = 0.010).

CONCLUSIONS

The 3D evaluation technique effectively revealed specific tendencies in dental students' caries removal skills. The integration of computerized assessments with traditional methods could potentially assist the instructors in delivering more objective and specific feedback to students. Further research is encouraged to investigate the impact of this assessment technique on improving student performance in selective caries removal skills.

Impact of scanning distance on the accuracy of a photogrammetry system

PURPOSE

To measure the impact of the scanning distance on the accuracy of complete-arch implant scans acquired by using a photogrammetry (PG) system.

MATERIAL AND METHODS

An edentulous cast with 6 implant abutment analogs was obtained. A brand new implant scan body was positioned on each implant abutment and digitized using an extraoral scanner (T710; Medit) and the reference file was obtained. Three groups were created based on the scanning distance used to acquire complete-arch implant scans by using a PG (PIC System; PIC Dental): 20 (20 group), 30 (30 group), and 35 cm (35 group). An optical marker (PIC Transfer, HC MUA Metal; PIC Dental) was placed on each implant abutment and a total of thirty scans per group were acquired. Euclidean linear and angular measurements were obtained on the reference file was obtained and used to compare the discrepancies with the same measurements obtained on each experimental scan. One-way ANOVA and Tukey tests were used to analyze trueness. The Levene test was used to analyze the precision values (α = 0.05).

RESULTS

Significant linear (P < .001) and angular trueness (P < .001) discrepancies were found among the groups. For linear trueness, Tukey test showed that the 20 and 30 groups (P < .001) and 30 and 35 groups were different (P < .001). For angular trueness, the Tukey test revealed that 20 and 30 groups (P = .003), 20 and 35 (P < .001), and 30 and 35 groups were different (P < .001) The Levene test showed no significant linear precision (P = .197) and angular discrepancies (P = .229) among the groups.

CONCLUSIONS

The scanning distance influenced the trueness of complete-arch implant scans obtained with the PG method tested. The maximum linear trueness mean discrepancy among the groups tested was 10 µm and the maximum angular trueness mean discrepancy among the groups tested was 0.02 .

Coordinate-based data analysis of the accuracy of five intraoral scanners for scanning completely dentate and partially edentulous mandibular arches

STATEMENT OF PROBLEM

Current methods for assessing the accuracy of intraoral scanners (IOSs) that reduce errors and provide comprehensive data compared with previous methods are lacking.

PURPOSE

The purpose of this in vitro study was to present a coordinate-based data analysis method to compare the accuracy of 5 IOSs for scanning completely dentate and partially edentulous casts.

MATERIAL AND METHODS

Reference scans of 2 complete arch casts (completely and partially dentate) were digitized using a high-precision laboratory scanner (Ceramill Map 600). Each cast was scanned 10 times each using 5 IOSs (3Shape TRIOS 3, Planmeca Emerald, iTero Element 5D, Medit i500, and Shining Aoralscan 3). The dataset of all 10 test groups was analyzed by using a reverse engineering software program (Geomagic Wrap). Each test cast was aligned with the reference cast by 3-dimensional (3D) superimposition to determine the translation and rotation along the x-, y-, and z-axes. The dataset was analyzed using the Kruskal-Wallis and post hoc Bonferroni tests (α=.05).

RESULTS

Significant differences were observed in all parameters among all scanners when scanning the same cast (P<.05). Significant differences were observed in at least 1 parameter for all scanners, except Element 5D after scanning different casts using the same scanner. Deviations in the test data generally relocated toward the mesial, buccal, and apical sides, and the casts were almost always rotated clockwise around the y-axis and counterclockwise around the z-axis. For the completely dentate cast, among all IOSs, Element 5D demonstrated the highest accuracy in most of the measured parameters, specifically in the y-axis translation (0.06[0.07] mm), z-axis translation (0.08[0.05] mm), and y-axis rotation (0.21[0.16] degree) (P<.05). For the partially edentulous cast, Element 5D displayed higher accuracy in most of the measured parameters, including the x-axis translation (0.11[0.14] mm) and z-axis rotation (0.12[0.18] degree) (P<.05). Emerald also displayed higher accuracy in most of the measured parameters, including the y-axis translation (0.05[0.08] mm) and y-axis rotation (0.14[0.12] degree) (P<.05). Element 5D exhibited no difference in the scanning accuracy between the 2 types of casts (P>.05).

CONCLUSIONS

Element 5D offered a high level of accuracy and was an appropriate scanner for both situations. The method presented in this study provides a good assessment of accuracy deviations in complete arch scans using 3D coordinate-based data analysis.

Influence of implant reference on the scanning accuracy of complete arch implant scans captured by using a photogrammetry system

STATEMENT OF PROBLEM

Photogrammetry has been reported to be a reliable digital alternative for recording implant positions; however, the factors that may impact the accuracy of photogrammetry techniques remain unknown.

PURPOSE

The purpose of this in vitro study was to assess the influence of the implant reference on the accuracy of complete arch implant scans acquired by using a photogrammetry system.

MATERIAL AND METHODS

An edentulous cast with 6 implant abutment analogs (MultiUnit Abutment Plus Replica) was obtained and digitized by using a laboratory scanner (T710; Medit). A photogrammetry system (PIC System) was selected to obtain complete arch implant scans. An optical marker (PIC Transfer, HC MUA Metal; PIC Dental) was positioned on each implant abutment of the reference cast. Each optical marker code and position was determined in the photogrammetry software program. Three groups were created based on the implant reference selected before acquiring the photogrammetry scans: right first molar (IPR-3 group), left canine (IPR-11 group), and left first molar (IPR-14 group) (n=30). Euclidean linear and angular measurements were obtained on the digitized reference cast and used to compare the discrepancies with the same measurements obtained on each experimental scan. One-way ANOVA and the Tukey tests were used to analyze the trueness data. The Levene test was used to analyze the precision values (α=.05 for all tests).

RESULTS

One-way ANOVA revealed significant linear (P=.003) and angular (P=.009) trueness differences among the groups tested. Additionally, the Tukey test showed that the IPR-11 and IPR-14 groups had significantly different linear (P<.001) and angular trueness (P<.001). The Levene test showed no significant precision linear (P=.197) and angular (P=.235) discrepancies among the groups tested. The IPR-3 group obtained the highest trueness (P<.001) and precision (P<.001) values among the groups tested.

CONCLUSIONS

Implant reference impacted the accuracy of complete arch implant scans obtained by using the photogrammetry system tested. However, a trueness ±precision linear discrepancy of 6 ±3 µm and an angular discrepancy of 0.01 ±0.01 degrees were measured among the groups tested; therefore, the impact of the discrepancy measured should not be clinically significant.

Accuracy of intraoral optical scan versus stereophotogrammetry for complete-arch digital implant impression: An in vitro study

PURPOSE

To assess and compare the accuracies of intraoral scanners (IOS) and stereophotogrammetry (SPG) devices for complete-arch digital implant impressions.

METHODS

A 4-analog model was digitized using a desk scanner to obtain a reference file. Thirty test scans were conducted using the investigated IOS device, while an additional 30 scans were performed using the SPG device. Using the best-fit algorithm, the resulting 60 test files were aligned with the reference file. Linear (ΔX, ΔY, and ΔZ-axis) and angular deviations (ΔANGLE) were evaluated. Three-dimensional (3D) deviation was calculated based on the Euclidean distance (ΔEUC). The analysis was stratified according to the scanning device and implant position. Fisher's F and t-tests were used to compare the variances and expected values of the two scanning systems.

RESULTS

IOS expressed a higher 3D (ΔEUC) mean deviation than SPG (52.8 µm vs. 33.4 µm, P < 0.0001), with extreme measurements up to 181.9 µm. A significantly higher standard deviation (SD) was associated with IOS (37.1 µm vs. 17.7 µm, P < 0.0001). Considering angular deviations, the IOS showed slightly higher angular mean deviations (ΔANGLE) than the SPG (0.28° vs. 0.24°, P = 0.0022), with extreme measurements of up to 0.73°. The SPG SD values were significantly lower than the IOS SD values (0.14° vs. 0.04°, P < 0.0001).

CONCLUSIONS

The SPG showed significantly higher 3D and angular accuracies for complete arch implant impressions, with consistent repeatability. IOS scanning revealed significantly higher extreme deviations exceeding the acceptable threshold value. Despite study limitations, SPG appears more feasible than IOS for complete-arch digital implant impressions.

Accuracy, scanning time, and patient satisfaction of stereophotogrammetry systems for acquiring 3D dental implant positions: A systematic review

PURPOSE

To evaluate accuracy, scanning time, and patient satisfaction of photogrammetry (PG) systems for recording the 3D position of dental implants.

MATERIAL AND METHODS

A literature search was completed in five databases: PubMed/Medline, Scopus, Embase, World of Science, and Cochrane. A manual search was also conducted. Studies reporting the use of commercially available PG systems were included. Two investigators evaluated the studies independently by applying the Joanna Briggs Institute critical appraisal. A third examiner was consulted to resolve any lack of consensus.

RESULTS

A total of 14 articles were included: 3 in vivo, 6 in vitro, and 6 case report manuscripts. One clinical study evaluated trueness, another one tested precision, and the third one assessed impression time and patient and operator satisfaction. All the in vitro studies evaluated the trueness and precision of a PG system. Additionally, all the reviewed studies investigated completely edentulous conditions with multiple implants. The number of placed implants per arch among the reviewed clinical studies varied from 4 to 8 implants, while the number of implants placed on the reference casts included 4, 5, 6, or 8 implants. Not all the studies compared the accuracy of PG systems with conventional impression methods, using intraoral scanners as additional experimental groups. For the PIC system, trueness ranged from 10 to 49 μm and precision ranged from 5 to 65 μm. For the iCam4D system, trueness ranged from 24 to 77 μm and the precision value ranged from 2 to 203 μm.

CONCLUSIONS

PG systems may provide a reliable alternative for acquiring the 3D position of dental implants. However, this conclusion should be interpreted carefully, as one study reported a mean precision value of one PG system higher than the clinically acceptable discrepancy. Lower scanning time and higher patient and operator satisfaction have been reported when compared with conventional techniques. Further studies are needed to increase the evidence regarding the accuracy, scanning time, and patient and operator satisfaction of the commercially available PG systems.

Trueness and precision of mandibular complete-arch implant scans when different data acquisition methods are used

OBJECTIVES

To evaluate the effect of different data acquisition methods on the trueness and precision of mandibular complete-arch implant scans.

METHODS

An edentulous polyurethane master mandibular model with 6 implants was digitized by using an industrial-grade blue light scanner (ATOS Core 80 5MP) to obtain a master standard tessellation language (MSTL) file. The master model was also digitized by using either direct digital workflow with a stereoscopic camera (iCam 4D (IM)) or intraoral scanners (CEREC Primescan (PS) and Trios 4 (T4)) or indirect digital workflow with laboratory scanners (inEos X5 (X5) and CARES 7 (S7)) to obtain test-scan STLs (n = 10). All STL files were imported into a metrology-grade analysis software (Geomagic Control X 2020.1) and test-scan STLs were superimposed over MSTL. The root mean square method was used to calculate surface deviations, while angular deviations were also calculated. Kruskal-Wallis and Dunn's tests were used to evaluate measured deviations (surface and angular) for trueness and precision (α = 0.05).

RESULTS

X5 and S7 had the lowest, and IM had the highest surface deviations (P ≤ .036). The angular deviations of PS were lower than those of X5, S7, and IM (P ≤ .008). When surface deviations were considered, T4 had the lowest precision among tested scanners (P ≤ .002), and the scans of IM had higher precision than those of PS (P = .003). Scanner type did not affect the precision of the scans when angular deviations were considered (P = .084).

CONCLUSIONS

The data acquisition method affected the trueness (surface and angular deviations) and precision (surface deviations) of mandibular complete-arch implant scans.

CLINICAL SIGNIFICANCE

Tested data acquisition methods may be feasible to digitize mandibular complete-arch implants considering the deviations of the scans, which were in the range of previously reported thresholds, and the high precision of scans. However, the frameworks fabricated with the direct digital workflow that involves the scans of the stereoscopic camera might require more adjustments than those fabricated by using the scans of other tested scanners.

In-vitro accuracy of a novel jaw-tracking technology

OBJECTIVES

As jaw-tracking systems integrate into digital prosthetic workflows, their accuracy remains underexplored. This study aimed to evaluate the in vitro accuracy of a novel digital jaw-tracking system (Modjaw, Villeurbanne, France) by comparing its precision and trueness to that of an industrial scanner.

METHODS

Upper and lower typodont models were scanned with an industrial-grade optical scanner (ATOS Q, Carl Zeiss GOM Metrology GmbH, Germany) to produce master scans. The models were placed in a phantom head with artificial joints to replicate five different intermaxillary relationships (IMRs). The 1, 2, 3, 4, and 5 mm IMR distances were stabilized by five silicone bites. The silicone bites were repositioned after each measurement. ATOS scanned the whole artificial joint with the models three times in each IMR to assess the precision of the repositioning (i.e., bite precision). The master scans were uploaded to Modjaw. Modjaw recorded the five IMR positions three times each to assess the precision of the Modjaw. Precision was calculated by aligning the scans within the same group, whereas Modjaw trueness was evaluated by aligning ATOS and Modjaw scans. The mean absolute distance (MAD) between aligned surfaces was calculated. The effect of IMR on the MAD was evaluated using a linear mixed model.

RESULTS

The mean bite precision across the IMRs was 7.6 ± 0.53 µm. Modjaw precision over the IMRS was 9.7 ± 1.76 µm, and the trueness was 10.8 ± 1.40 µm. Increased IMRs up to 4 mm significantly increased the MAD from 6.5 to 8.5 µm for the bite precision, 4.8 to 15.7 µm Modjaw precision, and 7.1 to 14.9 µm for trueness.

CONCLUSIONS

Modjaw excelled in accuracy, comparable to industrial scanners and superior to traditional methods. IMR elevation marginally deteriorates the accuracy. Future studies should extend to varied movements beyond centric relations and encompass the influence of intraoral scanners.

Accuracy of 2 direct digital scanning techniques-intraoral scanning and stereophotogrammetry-for complete arch implant-supported fixed prostheses: A prospective study

STATEMENT OF PROBLEM

Conventional impression techniques for complete arch implant-supported prostheses are technique-sensitive. Stereophotogrammetry (SPG) and intraoral scanning (IOS) may offer an alternative to conventional impression making.

PURPOSE

The purpose of this prospective study was to compare the accuracy of IOS and SPG for complete arch implant scans and to evaluate the passive fit of frameworks fabricated with SPG.

MATERIAL AND METHODS

Laboratory scanning of gypsum casts, SPG, and IOS were performed for all participants. The data regarding the abutment platform were superimposed to calculate the 3D deviation of SPG and IOS compared with that of laboratory scanning as an evaluation of accuracy. The effect of implant position and number on accuracy was analyzed. The more accurate technique between SPG and IOS was used to fabricate the titanium frameworks, as was laboratory scanning. The passive fit of the frameworks was assessed by clinical examination, the Sheffield test, and panoramic radiography.

RESULTS

Seventeen participants (21 arches, 120 implants) were included. The accuracy of SPG ranged from 2.70 μm to 92.80 μm, with a median (Q1, Q3) of 17.00 (11.68, 22.50) μm, which was significantly more accurate than that of IOS, ranging from 21.30 μm to 815.60 μm, with a median (Q1, Q3) of 48.95 (34.78, 75.88) μm. No significant correlation was found between position or number of implants and 3D deviation in the SPG group. A weak positive correlation was found between implant number and 3D deviation in the IOS group. SPG and laboratory scanning were used to fabricate titanium frameworks. The passive fit between the frameworks and abutment platforms was confirmed.

CONCLUSIONS

SPG, which was not affected by position or number of implants, was more accurate than IOS and comparable with laboratory scanning. The frameworks fabricated based on SPG and laboratory scanning were comparable in their passive fit. The SPG technique may be an alternative to laboratory scanning for complete arch implant scans.

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.

A completely digital workflow aided by cone beam computed tomography scanning to maintain jaw relationships for implant-supported fixed complete dentures: A clinical study

STATEMENT OF PROBLEM

The conventional workflow for the fabrication of implant-supported fixed complete dentures (IFCDs) is complex and makes it impossible to maintain jaw relationships. A fully digital workflow might solve this problem.

PURPOSE

The purpose of this clinical study was to develop a completely digital workflow aided by a cone beam computed tomography (CBCT) scan for the fabrication of IFCDs and to evaluate the accuracy of this workflow with regard to the maintenance of jaw relationships.

MATERIAL AND METHODS

All participants received a preoperative CBCT scan while wearing radiographic diagnosis dentures and occluding in the maximum intercuspal position. After the implant surgery, CBCT scanning, intraoral scanning, and stereophotogrammetry were performed to identify jaw anatomy, soft tissue, and the 3-dimensional (3D) locations of the implants, respectively. Then, all data were merged to transfer jaw relationships and generate digital casts to fabricate interim prostheses. A posttreatment CBCT scan was performed while the participants were wearing the interim prostheses and occluding in the maximum intercuspal position. The preoperative and postoperative jaw relationships were compared by CBCT cephalometric analysis. A meaningful and unacceptable difference was defined as 0.8 degrees and 2.4 degrees, respectively.

RESULTS

Six participants (6 jaw relationships, 9 arches, and 58 implants) were included. All interim prostheses were stable and achieved symmetric occlusion after only minimal adjustment. A total of 18 angles were measured. Three angles revealed a meaningful minimal difference, and 1 angle revealed an unacceptable minimal difference. No prosthodontic complications were reported during the study.

CONCLUSIONS

A completely digital workflow for fabricating IFCDs achieved sufficient accuracy for the maintenance of jaw relationships throughout the treatment.

Comparison of accuracy between digital and conventional implant impressions: two and three dimensional evaluations

PURPOSE

The present study compared the accuracy between digital and conventional implant impressions.

MATERIALS AND METHODS

The experimental models were divided into six groups depending on the implant location and the scanning span. Digital impressions were captured using the intraoral optical scanner TRIOS (3Shape, Copenhagen, Denmark). Conventional impressions were taken with the monophase impression material based on addition-cured silicones, Honigum-Mono (DMG, Hamburg, Germany). A high-precision laboratory scanner D900 (3Shape, Copenhagen, Denmark) was used to obtain digital data of resin models and stone casts. Surface tessellation language (STL) datasets from scanner were imported into the analysis software Geomagic Qualify 14 (3D Systems, Rock Hill, SC, USA), and scan body deviations were determined through two-dimensional and three-dimensional analyses. Each scan body was measured five times. The Sidak t test was used to analyze the experimental data.

RESULTS

Implant position and scanning distance affected the impression accuracy. For a unilateral arch implant and the mandible models with two implants, no significant difference was observed in the accuracy between the digital and conventional implant impressions on scan bodies; however, the corresponding differences for trans-arch implants and mandible with six implants were extremely significant (P<.001).

CONCLUSION

For short-span scanning, the accuracy of digital and conventional implant impressions did not differ significantly. For long-span scanning, the precision of digital impressions was significantly inferior to that of the traditional impressions.