Accuracy of Intraoral Scanners for Recording the Denture Bearing Areas: A Systematic Review

In vitro evaluation of the impact of intraoral scanner, scanning aids, and the scanned arch on the scan accuracy of edentulous arches

PURPOSE

To assess the accuracy of complete maxillary and mandibular edentulous arch scans obtained using two different intraoral scanners (IOSs), with and without scanning aids, and to compare these results to those obtained using conventional impression methods.

MATERIALS AND METHODS

Two IOSs were used (TRIOS 4 [TRI] and Emerald S [EMR]) to scan maxillary and mandibular typodonts. The typodonts were scanned without scanning aids [TRI_WSA and EMR_WSA groups] (n = 10). The typodonts were then scanned under four scanning aid conditions (n = 10): composite markers [TRI_MRK and EMR_MRK groups], scanning spray [TRI_SPR and EMR_SPR groups], pressure indicating paste [TRI_PIP and EMR_PIP groups], and liquid-type scanning aid [TRI_LQD and EMR_LQD groups]. Conventional impressions of both arches were also made using irreversible hydrocolloids in stock trays [IHC] and using polyvinyl siloxane (PVS) impression material in custom trays (n = 10) which were digitized using a laboratory scanner. Using a metrology software program, all scans were compared to a reference scan in order to assess trueness and to each other to assess precision. Trueness and precision were expressed as the root mean square (RMS) of the absolute deviation values and the statistical analysis was modeled on a logarithmic scale using fixed-effects models to meet model assumptions (α = 0.05).

RESULTS

The main effect of arch (p = 0.004), scanner (p < 0.001), scanning aid (p = 0.041), and the interaction between scanner and scanning aid (p = 0.027) had a significant effect on mean RMS values of trueness. The arch (p = 0.015) and scanner (p < 0.001) had a significant effect on the mean RMS values of precision. The maxillary arch had better accuracy compared to the mandible. The TRIOS 4 scanner had better accuracy than both the Emerald S scanner and conventional impressions. The Emerald S had better precision than conventional impressions. The scanning spray and liquid-type scanning aids produced the best trueness with the TRIOS 4 scanner, while the liquid-type scanning aid and composite markers produced the best trueness for the Emerald S scanner.

CONCLUSION

The scanned arch and the type of scanner had a significant effect on the accuracy of digital scans of completely edentulous arches. The scanning aid had a significant effect on the trueness of digital scans of completely edentulous arches which varied depending on the scanner used.

Impact of intraoral scanner, scanning strategy, and scanned arch on the scan accuracy of edentulous arches: An in vitro study

STATEMENT OF PROBLEM

The scanning strategy used when making complete arch digital scans affects the accuracy of the scan, and the accuracy of the strategy may be influenced by the scanner used. However, these effects have not been investigated thoroughly with complete arch edentulous scanning.

PURPOSE

The purpose of this in vitro study was to determine the effect of scanning strategies and the scanned arch on the accuracy of complete arch edentulous scans using 2 intraoral scanner (IOS) systems.

MATERIAL AND METHODS

Two IOSs were used (TRIOS 4 and Emerald S) to scan maxillary and mandibular typodonts using 6 scanning strategies (test scans), and conventional impressions of both arches were also made. By using a metrology software program, test scans were superimposed onto a reference scan, and the root mean square (RMS) of the absolute deviation values was calculated to express trueness. The sample with the best trueness was used as reference onto which the remaining samples from the same group were superimposed, and the RMS of the absolute deviation values was calculated to express precision. Statistical modeling was applied using the fixed effects models (α=.05).

RESULTS

The main effects of scanner and strategy significantly impacted the trueness RMS values (P<.001), with significant interactions between them (P=.012). The main effects of scanner, strategy, and arch significantly impacted the precision of RMS values (P=.004), (P=.033), and (P=.023). Conventional impressions and the TRIOS 4 scanner had comparable accuracy, while the Emerald S scanner was inferior to both. P-O-B had the highest overall accuracy and strategy ZZ had the worst. Better precision was found with the maxillary arch.

CONCLUSIONS

The scanner type and scanning strategy significantly impacted the accuracy of the digital scans of completely edentulous arches, with a significant interaction between scanner and strategy. The arch being scanned had a significant effect on scan precision but not on scan trueness.

Recent Advances in Digital Technology in Implant Dentistry

Digital technology has emerged as a transformative tool in dental implantation, profoundly enhancing accuracy and effectiveness across multiple facets, such as diagnosis, preoperative treatment planning, surgical procedures, and restoration delivery. The multiple integration of radiographic data and intraoral data, sometimes with facial scan data or electronic facebow through virtual planning software, enables comprehensive 3-dimensional visualization of the hard and soft tissue and the position of future restoration, resulting in heightened diagnostic precision. In virtual surgery design, the incorporation of both prosthetic arrangement and individual anatomical details enables the virtual execution of critical procedures (e.g., implant placement, extended applications, etc.) through analysis of cross-sectional images and the reconstruction of 3-dimensional surface models. After verification, the utilization of digital technology including templates, navigation, combined techniques, and implant robots achieved seamless transfer of the virtual treatment plan to the actual surgical sites, ultimately leading to enhanced surgical outcomes with highly improved accuracy. In restoration delivery, digital techniques for impression, shade matching, and prosthesis fabrication have advanced, enabling seamless digital data conversion and efficient communication among clinicians and technicians. Compared with clinical medicine, artificial intelligence (AI) technology in dental implantology primarily focuses on diagnosis and prediction. AI-supported preoperative planning and surgery remain in developmental phases, impeded by the complexity of clinical cases and ethical considerations, thereby constraining widespread adoption.

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.

Influence of ambient light conditions on intraoral scanning: A systematic review

PURPOSE

To systematically assess the influence of ambient light on the accuracy and scanning time of intraoral scanning.

STUDY SELECTION

The present systematic review (CRD 42022346672) was registered at the International Prospective Register of Systematic Reviews (PROSPERO) and was performed based on the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020. Electronic searches were conducted using PubMed, Web of Science, and EMBASE, complemented by gray literature, references, and citations of the included studies. The primary outcome was accuracy, and the scanning time was a secondary outcome. Owing to the high heterogeneity, the pooled data were analyzed descriptively.

RESULTS

Six in vitro and two in vivo experiments were performed. Three in vitro studies reported both the accuracy and scanning time of the intraoral scans, whereas the remaining studies exclusively evaluated the accuracy. The studies mainly investigated the influence of illumination levels (0-11000 lux) on intraoral scanning. Intraoral scans revealed optimal accuracy at 1000-lux illumination for complete-arch dentition scans, whereas the influence of illumination levels on 4-unit or shorter scans was not clinically significant. The intraoral scans obtained using confocal microscopy were less affected by the illumination levels than those obtained using the active triangulation technique. Furthermore, the scanning time tended to increase with increasing illumination.

CONCLUSIONS

Evidently from the limited number of studies conducted, ambient light illumination had considerable influence on the accuracy and scanning time of intraoral scanning, which appeared to be related to the scanning range and imaging technology.

Fit and retention of complete denture bases: Part II - conventional impressions versus digital scans: A clinical controlled crossover study

STATEMENT OF PROBLEM

Although the intraoral scanning of edentulous ridges is feasible, clinical evidence that the resulting denture retention is equivalent to that achieved with conventional impressions is lacking.

PURPOSE

The purpose of this clinical study was to determine the retention of complete denture bases fabricated from digital intraoral scans versus conventional impressions by using border molding and posterior palatal seal compression.

MATERIAL AND METHODS

Twenty volunteers with an edentulous maxilla were recruited. An intraoral scan of the maxilla and a conventionally border-molded impression with a custom tray were made. The conventional impression was poured; the definitive cast was scanned. Three-dimensionally (3D) printed (PB1) and milled bases (MB1) were fabricated based on the scan of the definitive cast. Based on the intraoral scan, a 3D printed (PB2) and a milled base (MB2) were fabricated. On each base, a platform with a hook consisting of a central notch orienting the force against the post dam (PD) and 2 lateral notches orienting the forces against the left (LT) and right (RT) tuberosities was set in the center of the outer surface of the base. A traction dynamometer was inserted in the hook and oriented into the corresponding notch by applying force until dislodgement. All bases were subsequently stored in artificial saliva for 2 weeks and scanned. Retention testing was repeated by using the same procedure. To evaluate trueness and to visualize the differences on a color map, the scan of the definitive cast and the intraoral scans were matched and compared in 3 dimensions. The Wilcoxon tests were used to compare the retention of the different bases (95% confidence interval, α=.05).

RESULTS

Nineteen participants with a mean ±standard deviation age of 64.1 ±14.7 years completed the 4 study sessions. The retention of printed bases (PD: 16.08 ±15.28 N; LT: 14.98 ±14.72 N; RT: 11.28 ±9.57 N) and milled bases (PD:14.52 ±17.07 N; RT: 11.99 ±12.10 N; LT: 13.55 ±15.53 N) fabricated from conventional impressions presented significantly higher retentive forces than those printed (PD: 6.21 ±4.72 N; RT:5.12 ±2.78 N; LT: 4.45 ±2.77 N) and milled (PD: 6.58 ±4.92 N; RT: 4.65 ±2.63 N; LT: 5.02 ±3.58 N) from the intraoral scans (P<.05). The differences were significant in all directions of dislodgement, as well as after storage in artificial saliva for 2 weeks. Comparison of the 3D distances between the intraoral scan and the definitive cast revealed a mean deviation of 0.45 ±0.11 mm.

CONCLUSIONS

Conventional impressions of the edentulous maxilla, including the clinical steps of border molding and posterior palatal seal compression, provide better retention than digital intraoral scans with both milled and 3D printed denture bases.

Influence of connected and nonconnected calibrated frameworks on the accuracy of complete arch implant scans obtained by using four intraoral scanners, a desktop scanner, and a photogrammetry system

STATEMENT OF PROBLEM

Different techniques have been proposed for increasing the accuracy of complete arch implant scans obtained by using intraoral scanners (IOSs), including a calibrated metal framework (IOSFix); however, its accuracy remains uncertain.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of complete arch scans obtained with connecting and non-connecting the implant scan bodies (ISBs) recorded using intraoral scanners (IOSs), a laboratory scanner (LBS), and photogrammetry (PG).

MATERIAL AND METHODS

A cast with 6 implant abutment analogs was obtained. Six groups were created: TRIOS 4, i700, iTero, CS3800, LBS, and PG groups. The IOSs and LBS groups were divided into 3 subgroups: nonconnected ISBs (ISB), splinted ISBs (SSB), and calibrated framework (CF), (n=15). For the ISB subgroups, an ISB was positioned on each implant abutment analog. For the SSB subgroups, a printed framework was used to connect the ISBs. For the CF subgroups, a calibrated framework (IOSFix) was used to connect the ISBs. For the PG group, scans were captured using a PG (PIC Camera). Implant positions of the reference cast were measured using a coordinate measurement machine, and Euclidean distances were used as a reference to calculate the discrepancies using the same distances obtained on each experimental scan. Wilcoxon squares 2-way ANOVA and pairwise multiple comparisons were used to analyze trueness (α=.05). The Levene test was used to analyze precision (α=.05).

RESULTS

Linear and angular discrepancies were found among the groups (P<.001) and subgroups (P<.001). Linear (P=.008) and angular (P<.001) precision differences were found among the subgroups.

CONCLUSIONS

The digitizing method and technique impacted the trueness and precision of the implant scans. The photogrammetry and calibrated framework groups obtained the best accuracy. Except for TRIOS 4, the calibrated framework method improved the accuracy of the scans obtained by using the IOSs tested.

Improving the accuracy of complete arch implant digital scans by using auxiliary clips for intraoral scan bodies: A dental technique

A technique to improve the accuracy of complete arch implant intraoral digital scans and the accuracy of their virtual casts is described. Obtaining accurate complete arch implant intraoral digital scans with an intraoral scanner is challenging because of the smooth and movable tissues of edentulous areas. The described technique uses auxiliary clips attached to intraoral scan bodies to cover interimplant edentulous spans with immobile tooth-like geometric references that are more favorable for intraoral scanning. The technique is designed to be user friendly and compatible with any intraoral scanner.

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.

A guide for selecting the intraoral scan extension when fabricating tooth- and implant-supported fixed dental prostheses

OBJECTIVES

To describe a new classification for intraoral scans based on the scan extension and to introduce a decision guideline to choose the scan extension for fabricating tooth- and implant-supported fixed dental prostheses (FDPs).

OVERVIEW

Multiple operator- and patient-related factors have been identified that can decrease the scanning accuracy of intraoral scanners (IOSs), including scan extension. However, the decision criteria for selecting scan extension for fabricating tooth- and implant-supported restorations is unclear. Based on the extension of the intraoral digital scans, three types of scans can be defined: half-arch (anterior or posterior), extended half-arch, and complete-arch scan. Variables to consider when choosing the scan extension include the number and location of units being restored, as well as the extension and location of edentulous areas. Additionally, the accuracy of the virtual definitive cast and the accuracy of the maxillomandibular relationship captured by using IOSs should be differentiated.

CONCLUSIONS

A decision tree for selecting the scan extension is presented. The decision is based on the number and location of units being restored, and the extension and location of edentulous areas. Intraoral scans with reduced scan extension are indicated when fabricating tooth- and implant-supported crowns or short-span fixed prostheses, when the patient does not have more than one missing tooth in the area of the dental arch included in the scan. For the remaining clinical conditions, complete-arch intraoral scans are recommended.

CLINICAL SIGNIFICANCE

Scan extension is a clinician's decision that should be based on the number and location of units being restored and the extension and location of edentulous areas. Intraoral scans with a reduced scan extension is recommended, when possible.

Use of a dual-purpose implant scan body to obtain both digital and analog records for complete arch fixed implant restorations

A technique is described for capturing relative dental implant positions for an implant-supported fixed prosthesis in a completely edentulous arch with a novel implant indexing apparatus that also functions as a scannable verification device. A series of intraoral scans are made to record the contours and occlusal records of the existing prosthetics and soft tissue. The individual scans are aligned by using a dental software program to design either an interim or definitive prosthesis. The technique reduces the time needed to gather the records dental laboratory technicians require to fabricate a complete arch implant-supported prosthesis.

Influence of implant scan body design (height, diameter, geometry, material, and retention system) on intraoral scanning accuracy: A systematic review

PURPOSE

To evaluate the influence of implant scan body (ISB) design (height, diameter, geometry, material, and retention system) on the accuracy of digital implant scans.

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 evaluation of ISB design on the accuracy of digital scans obtained by using IOSs 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. Articles were classified based on the ISB features of height, geometry, material, and retention system.

RESULTS

Twenty articles were included. Among the reviewed studies, 11 investigations analyzed the influence of different ISB geometries, 1 study assessed the impact of ISB diameter, 4 studies investigated the effect of ISB splinting, 2 articles evaluated ISB height, and 2 studies focused on the effect of ISB material on scan accuracy. In addition, 8 studies involved ISBs fabricated with different materials (1- and 2-piece polyetheretherketone and 1-piece titanium ISBs), and all of the reviewed articles tested screw-retained ISBs, except for 3 in vitro studies.

CONCLUSIONS

The findings did not enable concrete conclusions regarding the optimal ISB design, whether there is a relationship between IOS technology and a specific ISB design, or the clinical condition that maximizes intraoral scanning accuracy. Research efforts are needed to identify the optimal ISB design and its possible relationship with the IOS selected for acquiring intraoral digital implant scans.

Additively manufactured devices with varying designs and sizes for acquiring initial intraoral implant scans

Dental literature has reported greater intraoral scanning accuracy when implant scan bodies (ISBs) are connected compared with non-connected methods. Initial intraoral digital implant scans are required for the fabrication of a custom framework to connect implant scan bodies (IOSFix; IOSFix Dental). This calibrated metal framework is used to acquire definitive intraoral implant scans. However, the acquisition of initial intraoral implant scans can be challenging when ISBs are not connected. This article describes a step-by-step technique for connecting ISBs by using additively manufactured devices to acquire initial intraoral implant scans. This technique aims to facilitate the recording of initial intraoral implant scans, provide different device designs and sizes to connect ISBs, and reduce chairside time.

Intraoral digital implant scans: Parameters to improve accuracy

PURPOSE

To report the means to maximize the predictability and accuracy of intraoral digital implant scans through the evaluation of operator and patient-related factors.

MATERIALS AND METHODS

A search of published articles related to factors that can decrease the scanning accuracy of intraoral digital implant scans was completed in four data sources:MEDLINE, EMBASE, EBSCO, and Web of Science. All studies related to variables that can influence the accuracy of intraoral digital implant scans obtained by using intraoral scanners (IOSs) were considered. These variables included ambient lighting, scanning pattern, implant scan body (ISB) design, techniques for splinting ISBs, arch location, implant position, and inter-implant distance.

RESULTS

Among operator-related factors, ambient lighting conditions, scanning pattern, and ISB design (material, geometry, and retention design) can impact the accuracy of intraoral digital implant scans. The optimal ISB for maximizing IOS accuracy is unclear; however, polymer ISB can wear with multiple reuse and sterilization methods. Among patient-related factors, additional variables should be considered, namely arch (maxillary vs. mandibular arch), implant position in the arch, inter-implant distance, implant depth, and angulation.

CONCLUSIONS

Ambient lighting conditions should be established based on the IOS selected to optimize the accuracy of intraoral digital implant scans. The optimal scanning pattern may vary based on the IOS, clinical situation, and the number of implants. The optimal ISB design may vary depending on the IOS used. Metallic implant scan bodies are preferred over polymer ISB designs to minimize wear due to multiple use and sterilization distortion. Among patient-related factors, additional variables should be considered namely the arch scanned, implant position in the arch, inter-implant distance, implant depth, and angulation. The impact of these factors may vary depending on the IOS selected.

Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners

PURPOSE

To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs).

MATERIALS AND METHODS

A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3 mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3 mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05).

RESULTS

Trueness ranged from 91 to 139 μm and precision ranged from 5 to 23 μm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11 μm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4 μm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision.

CONCLUSION

Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Non-invasive oral implant position assessment: An ex vivo study using a 3D industrial scan as the reference model to mimic the clinical situation

AIM

To introduce an objective method to evaluate the accuracy of implant position assessment in partially edentulous patients by comparing different techniques (conventional impression, intraoral scan, CBCT) to a reference 3D model obtained with an industrial scanner, the latter mimicking the clinical situation.

MATERIALS AND METHODS

Twenty-nine implants were placed in four human cadaver heads using a fully guided flapless protocol. Implant position was assessed using (a) a conventional impression, (b) an intraoral scan, and (c) CBCT and compared to an industrial scan. Three-dimensional models of intraoral scan body and implant were registered to the arch models and the deviation at implant shoulder, apex, and the angle of deviation were compared to each other as well as to the reference model.

RESULTS

The three assessment techniques showed statistically significant deviations (p < .01) from the industrial scan, for all measurements, with no difference between the techniques. The maximum deviation at the implant shoulder was 0.16 mm. At the implant apex this increased to 0.38 mm. The intraoral scan deviated significantly more than the CBCT (0.12 mm, p < .01) and the conventional impression (0.10 mm, p = .02). The maximum implant angle deviation was 1.0°. The intraoral scan deviated more than the conventional impression (0.3°, p = .02).

CONCLUSION

All assessment techniques deviated from the reference industrial scan, but the differences were relatively small. Intraoral scans were slightly less accurate than both conventional impressions and CBCT. Depending on the application, however, this inaccuracy may not be clinically relevant.

Assessment of distortion of intraoral scans of edentulous mandibular arch made with a 2-step scanning strategy: A clinical study

STATEMENT OF PROBLEM

Manufacturers of several intraoral scanners have recommended a 2-step strategy for scanning the edentulous mandible. The 2-step technique requires scanning one side first and then moving to the other side. However, whether inconsistency in stitching occurs that results in loss of accuracy or distortion is unclear.

PURPOSE

The purpose of this clinical study was to measure the potential distortion of intraoral scans of edentulous mandibular arches made with a 2-step scanning strategy and to assess their differences with conventional impressions.

MATERIAL AND METHODS

Twenty mandibular edentulous arches were scanned by 1 investigator with an intraoral scanner using a 2-step scanning strategy, and a corresponding polysulfide conventional impression was obtained. The conventional impression was then immediately scanned with the same intraoral scanner. The obtained standard tessellation language (STL) files were superimposed with a surface-matching software program. After a preliminary alignment, the STL meshes were trimmed and reoriented; then, the final alignment was carried out and meshes moved to a metrology software program where their mean distance was measured. In addition, a surface curve (SIOS) was traced on the intraoral scan from the right to left retromolar pad along the residual ridge and automatically projected onto to the conventional impression scan to obtain a new curve (SC). The mean distance between SIOS and SC was measured and recorded as an indicator of the distortion by considering the X-, Y-, and Z-axes and the overall 3-dimensional (3D) deviation. The analysis was performed for the full curve length and after dividing it into 6 regions of interest. Univariate and multivariate statistical analyses were used to investigate the significance of the extent of the mean 3D distance, as well as the effects of measurement positions (side and region) between and within patients on differences along the X-, Y-, and Z-axes (α=.05).

RESULTS

The mean (-0.08 mm; standard error: 0.025) 3D distance between the intraoral scan and conventional impression was significantly different from zero (P=.003). No significant effect of the factor "side" was found by using generalized estimated equation models for the X-, Y-, and Z-axes, and global 3D deviations between SIOS and SC (P>.05), which appeared to exclude distortion. Conversely, a significant effect was found for the factor "region" (P<.05), with no significant differences (P>.05) between corresponding regions on the 2 sides.

CONCLUSIONS

Intraoral scans of the edentulous mandibular arch made in a 2-step procedure did not exhibit significant distortion in comparison with conventional impressions.

Application of three-dimensional reconstruction technology in dentistry: a narrative review

BACKGROUND

Three-dimensional(3D) reconstruction technology is a method of transforming real goals into mathematical models consistent with computer logic expressions and has been widely used in dentistry, but the lack of review and summary leads to confusion and misinterpretation of information. The purpose of this review is to provide the first comprehensive link and scientific analysis of 3D reconstruction technology and dentistry to bridge the information bias between these two disciplines.

METHODS

The IEEE Xplore and PubMed databases were used for rigorous searches based on specific inclusion and exclusion criteria, supplemented by Google Academic as a complementary tool to retrieve all literature up to February 2023. We conducted a narrative review focusing on the empirical findings of the application of 3D reconstruction technology to dentistry.

RESULTS

We classify the technologies applied to dentistry according to their principles and summarize the different characteristics of each category, as well as the different application scenarios determined by these characteristics of each technique. In addition, we indicate their development prospects and worthy research directions in the field of dentistry, from individual techniques to the overall discipline of 3D reconstruction technology, respectively.

CONCLUSIONS

Researchers and clinicians should make different decisions on the choice of 3D reconstruction technology based on different objectives. The main trend in the future development of 3D reconstruction technology is the joint application of technology.

Development and Comparison of Conventional and 3D-Printed Laboratory Models of Maxillary Defects

BACKGROUND

Recording accurate impressions from maxillary defects is a critical and challenging stage in the prosthetic rehabilitation of patients following maxillectomy surgery. The aim of this study was to develop and optimize conventional and 3D-printed laboratory models of maxillary defects and to compare conventional and digital impression techniques using these models.

METHODS

Six different types of maxillary defect models were fabricated. A central palatal defect model was used to compare conventional silicon impressions with digital intra-oral scanning in terms of dimensional accuracy and total time taken to record the defect and produce a laboratory analogue.

RESULTS

Digital workflow produced different results than the conventional technique in terms of defect size measurements which were statistically significant (p < 0.05). The time taken to record the arch and the defect using an intra-oral scanner was significantly less compared with the traditional impression method. However, there was no statistically significant difference between the two techniques in terms of the total time taken to fabricate a maxillary central defect model (p > 0.05).

CONCLUSIONS

The laboratory models of different maxillary defects developed in this study have the potential to be used to compare conventional and digital workflow in prosthetic treatment procedures.

Influence of arch location and scanning pattern on the scanning accuracy, scanning time, and number of photograms of complete-arch intraoral digital implant scans

OBJECTIVES

To measure the influence of arch location and scanning pattern on the accuracy, scanning time, and number of photograms of complete-arch implant scans acquired using an intraoral scanner (IOS).

MATERIALS AND METHODS

A maxillary (maxillary group) and mandibular (mandibular group) model with 6 implant abutments on each cast was digitized using a desktop scanner (control scans). Six subgroups were created based on the scanning pattern used to acquire the scans using an IOS (Trios 4): occluso-buccal-lingual (OBL subgroup), occluso-linguo-buccal (OLB subgroup), bucco-linguo-occlusal (BLO subgroup), linguo-buccal-occlusal (LBO subgroup), zigzag (ZZ subgroup), and circumferential (C subgroup). The control scans were used as a reference to measure the discrepancy with the experimental scans calculating the root mean square error. Two-way ANOVA and the pairwise comparison Tukey tests were used to analyze the data (α = .05).

RESULTS

Significant discrepancies in trueness (p < .001), precision (p < .001), scanning time (p < .001), and number of photograms (p < .001) were found. The maxillary group obtained poorer trueness and precision values, higher scanning times, and a larger number of photograms than the mandibular group. The C subgroup obtained the best trueness and precision values, but was not significantly different from the OLB, BLO, and LBO subgroups. The ZZ subgroup obtained the worst trueness and precision values (p < .05). The C subgroup obtained the lowest scanning time and number of photograms (p < .05).

CONCLUSIONS

Arch location and scanning pattern influenced scanning accuracy, scanning time, and number of photograms of complete-arch implant scans.

Scanning accuracy and scanning area discrepancies of intraoral digital scans acquired at varying scanning distances and angulations among 4 different intraoral scanners

STATEMENT OF PROBLEM

The accuracy of intraoral scanners (IOSs) can be affected by operator handling; however, the scanning area and accuracy discrepancies acquired at different scanning distances and angulations among IOSs remain uncertain.

PURPOSE

The objective of this in vitro study was to compare the scanning area and scanning accuracy of the intraoral digital scans obtained at 3 scanning distances with 4 different scanning angulations among 4 different IOSs.

MATERIAL AND METHODS

A reference device (reference file) was designed with 4 inclinations (0, 15, 30, and 45 degrees) and printed. Four groups were created based on the IOS: i700, TRIOS4, CS 3800, and iTero scanners. Four subgroups were generated depending on the scanning angulation (0, 15, 30, and 45 degrees). Each subgroup was divided into 3 subgroups based on the scanning distance: 0, 2, and 4 mm (N=720, n=15). The reference devices were positioned in a z-axis calibrated platform for standardizing the scanning distance. In the i700-0-0 subgroup, the 0-degree reference device was positioned in the calibrated platform. The wand of the IOS was positioned in a supporting framework with a 0-mm scanning distance, and the scans were acquired. In the i700-0-2 subgroup, the platform was lowered for a 2-mm scanning distance followed by the specimen acquisition. In the i700-0-4 subgroup, the platform was further lowered for a 4-mm scanning distance, and the scans were obtained. For the i700-15, i700-30, and i700-45 subgroups, the same procedures were carried out as in the i700-0 subgroups respectively, but with the 10-, 15-, 30-, or 45-degree reference device. Similarly, the same procedures were completed for all the groups with the corresponding IOS. The area of each scan was measured. The reference file was used to measure the discrepancy with the experimental scans by using the root mean square (RMS) error. Three-way ANOVA and post hoc Tukey pairwise comparison tests were used to analyze the scanning area data. Kruskal-Wallis and multiple pairwise comparison tests were used to analyze the RMS data (α=.05).

RESULTS

IOS (P<.001), scanning distance (P<.001), and scanning angle (P<.001) were significant factors of the scanning area measured among the subgroups tested. A significant group×subgroup interaction was found (P<.001). The iTero and the TRIOS4 groups obtained higher scanning area mean values than the i700 and CS 3800 groups. The CS 3800 obtained the lowest scanning area among the IOS groups tested. The 0-mm subgroups obtained a significantly lower scanning area than the 2- and 4-mm subgroups (P<.001). The 0- and 30-degree subgroups obtained a significantly lower scanning area than the 15- and 45-degree subgroups (P<.001). The Kruskal-Wallis test revealed significant median RMS discrepancies (P<.001). All the IOS groups were significantly different from each other (P<.001), except for the CS 3800 and TRIOS4 groups (P>.999). All the scanning distance groups were different from each other (P<.001).

CONCLUSIONS

Scanning area and scanning accuracy were influenced by the IOS, scanning distance, and scanning angle selected to acquire the digital scans.

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.

Trueness of intraoral scanning of edentulous arches: A comparative clinical study

PURPOSE

To compare the accuracy of intraoral scanning (IOS) of the edentulous arch with the hybrid protocol of cast digitization (CD), and to investigate the effect of arch type and area on trueness.

MATERIALS AND METHODS

Participants that were edentulous in both arches were recruited. Two impression protocols were used; the IOS as the test protocol with an IOS device (TRIOS 4; 3Shape, Denmark), and the CD as the control, including tracing compound (TRACING STICKS; Kemdent, UK) for border molding, polyvinyl siloxane (Hydrorise Monophase; Zhermack, Italy) for impression, and cast digitization with a laboratory scanner (ceramill® map400, AMANNGIRRBACH, Germany). Scanned files were exported to a 3D inspection software (Geomagic Control X; 3D Systems, NC) for trueness analysis. The CD file (reference file) for each participant was split into 2 areas; the dynamic area representing the mobile tissues at the peripheral border, and the static area representing the rest of the arch. Statistical analyses were performed with 1-sample t-test for the difference between CD and IOS protocols, paired sample t-test for the difference between the static and dynamic areas for each arch, and an independent sample t-test for the difference between the maxillary and mandibular arches for each area, with α = 0.05. Effect size was calculated with Cohen's d (d), with 0.2 as small, 0.5 as medium, and 0.8 as large.

RESULTS

A total of 21 participants were included. The difference between the IOS and CD protocol was significant for all subset comparisons (p < 0.001, d: 2.5-6.2, large effect size). Dynamic areas had lower trueness in comparison with static areas (p < 0.001, d = 4.57, large effect size for the maxillary arch, p < 0.001, d = 3.96, large effect size for the mandibular arch). Mandibular arch had lower trueness in comparison with the maxillary arch (p < 0.001, d = 1.45, large effect size for the static areas, p = 0.009, d = 0.85, large effect size for the dynamic areas, p < 0.001, d = 1.71, large effect size for all areas). Color difference map showed marked positive deviation in the buccal dynamic areas of both arches, and nonmatching areas with evident overstretching.

CONCLUSIONS

While the IOS of edentulous arches could be feasible for attached mucosa, providing a functional shape for the peripheral border remains a challenge, with a thinner and more outward border for the IOS in comparison with the CD protocol. The IOS of the mandibular arch is more difficult and has lower trueness in comparison with the maxillary arch.

A guide for maximizing the accuracy of intraoral digital scans: Part 2-Patient factors

OBJECTIVES

To describe the factors related to patient intraoral conditions that impact the scanning accuracy of intraoral scanners (IOSs). A new classification for these influencing factors is proposed to facilitate dental professionals' decision-making and maximize the accuracy and reliability of intraoral digital scans.

OVERVIEW

Variables related to intraoral conditions of the patient that can influence the scanning accuracy of IOSs include tooth type, presence of interdental spaces, arch width variations, palate characteristics, wetness, existing restorations, characteristics of the surface being digitized, edentulous areas, interimplant distance, position, angulation, and depth of existing implants, and implant scan body selection.

CONCLUSIONS

The knowledge and understanding of the patient's intraoral conditions that can impact the scanning accuracy of IOSs is a fundamental element for maximizing the accuracy of IOSs.

CLINICAL SIGNIFICANCE

The patient's intraoral conditions, or patient factors, can significantly impact intraoral scanning accuracy. Dental professionals must know and understand these influencing patient factors to maximize the accuracy of IOSs.

Comparative evaluation of digitally fabricated complete dentures versus conventional complete dentures: A randomized, single-blinded, cross-over clinical trial

STATEMENT OF PROBLEM

Clinical trials comparing outcomes associated with digital complete dentures (CDs) fabricated from intraoral scan data with those of CDs fabricated by using the conventional workflow are lacking.

PURPOSE

The purpose of this randomized clinical trial was to evaluate the clinical performance of and patient satisfaction associated with digitally versus conventionally fabricated CDs.

MATERIAL AND METHODS

Eight participants requiring CDs were enrolled in this study. Two sets of CDs were fabricated for each participant. One set was fabricated by using a digital workflow, which involved digital scanning with an intraoral scanner, whereas the other set was made by using the conventional workflow. The participants were given 1 set of CDs for 1 month and another set for the next month. The order of placing CDs was randomly selected for each participant. The internal adaptation, masticatory force, and masticatory efficiency of the CDs in each group were evaluated for objective analysis. Additionally, a questionnaire was provided to the participants, and the responses were evaluated for subjective satisfaction analysis. All parameters were analyzed by using t tests (α=.05).

RESULTS

The internal adaptation did not statistically significantly differ between the conventional and digital CDs with regard to the maxillary arches (P=.406) and mandibular arches (P=.412). The average masticatory force (P=.051) and maximum masticatory force (P=.110) likewise did not statistically significantly differ between the 2 types of CDs. Masticatory efficiency, expressed via the mixing ability index, was statistically better for conventional CDs than the digital CDs (P=.009). No statistically significant differences were observed between the 2 types of CDs in terms of overall patient satisfaction as assessed by using the study questionnaire (P=.172 for maxillary CD and P=.161 for mandibular CD). However, the conventional CDs were statistically significantly better than the digital CDs with regard to subjective satisfaction with pronunciation ability (P=.006).

CONCLUSIONS

The digital CDs were inferior to the conventional CDs in terms of masticatory efficiency and pronunciation. However, internal adaptation and overall patient satisfaction were comparable between conventional and digital CDs. This finding suggests that intraoral scanning and additively manufactured CDs may be suitable for edentulous patients, at least for interim use.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The Scientific Investigation Committee of the American Academy of Restorative Dentistry offers this review of the 2021 dental literature in restorative dentistry to inform busy dentists regarding noteworthy scientific and clinical progress over the past year. Each member of the committee brings discipline-specific expertise to coverage of this broad topical area. Specific subject areas addressed, in order of the appearance in this report, include COVID-19 and the dental profession (new); prosthodontics; periodontics, alveolar bone, and peri-implant tissues; implant dentistry; dental materials and therapeutics; occlusion and temporomandibular disorders; sleep-related breathing disorders; oral medicine and oral and maxillofacial surgery; and dental caries and cariology. The authors focused their efforts on reporting information likely to influence daily dental treatment decisions with an emphasis on future trends in dentistry. With the tremendous volume of dentistry and related literature being published daily, this review cannot possibly be comprehensive. Rather, its purpose is to update interested readers and provide important resource material for those interested in pursuing greater details on their own. It remains our intent to assist colleagues in negotiating the extensive volume of important information being published annually. It is our hope that readers find this work useful in successfully managing the patients and dental problems they encounter.

Digital technology for fabrication of removable dental prosthesis with double crowns combining fiber-reinforced composite and zirconia

PATIENTS

This clinical report describes the process for fabricating a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia using digital technology. An 83-year-old woman presented with gingival swelling around the maxillary right premolar. The swollen tooth was the abutment tooth of a cross-arch fixed partial denture. An intraoral scanner (IOS) and computer-aided design/manufacturing as digital technology were used to plan treatment with a double-crown-retained removable dental prosthesis. A metal-free prosthesis using zirconia for the primary crown and fiberglass-reinforced composite resin for the secondary crown was planned, and the patient consented to the treatment plan. After autotransplantation of a tooth as one of the abutments, the IOS was used to obtain digital scans of the prepared surface of the abutment teeth, opposing dentition, and occlusal relationships. First, primary crowns were milled using zirconia. Next, the intraoral scanner obtained a pick-up impression of the primary crowns, and secondary crowns were designed and milled from the fiber-reinforced composite. After delivery, the patient expressed satisfaction with the functionality, esthetics, and fit of the double-crown-retained removable dental prosthesis.

DISCUSSION

Digital technology offers many advantages such as efficient fabrication of double crowns, reduced material costs, improved biocompatibility, and good aesthetics of metal-free materials.

CONCLUSION

This clinical report describes the application of digital technology for the fabrication of a double-crown-retained removable dental prosthesis combining a fiber-reinforced composite and zirconia, resulting in patient satisfaction.

Evaluation of the potential denture covering area in buccal shelf with intraoral scanner

Background/purpose

The characteristic of soft tissue changes in buccal shelf area during function is unclear. This study aimed for evaluating the potential denture covering area in buccal shelf area in different ranges of mouth opening by a digital approach.

Materials and methods

Nineteen qualified dentate participants were enrolled. An intraoral scanner was used to record soft tissue in buccal shelf area in different ranges of mandibular opening, which were maximum intercuspation, 10 mm, 20 mm, and 30 mm of interincisal distance. The experiment was performed by two examiners. The common area of each range was generated within the clinically acceptable denture adaptation range, which was represented as the potential denture covering area. Data were statistically analyzed using descriptive statistic, one-way repeated measure ANOVA, intraclass correlation coefficient (ICC), and the Pearson correlation test.

Results

Trends of the mean distance of the potential denture covering area increased from the frenum area to the second premolar and the first molar area then decreased in the second molar area, along with the ranges of mouth opening increased. The distance in the second molar area had drastic percentage changes during the mouth opening. The mean distances changed significantly when the mouth opening increased (P < 0.001). All ICC values of intra-, inter-rater reliability indicated good to excellent reliability. The correlation between the results from two examiners was strong (P < 0.001).

Conclusion

The characteristic of the denture covering area posteriorly to the first molar area is inversely proportional in length to ranges of mouth opening.

Intraoral Digital Scans for Fabricating Tooth-Supported Prostheses Using a Custom Intraoral Scan Body

This article describes a technique to assist with intraoral digital scans for fabricating tooth-supported prostheses by using a custom intraoral scan body when the extension of the scan or the clinical characteristics might compromise the reliability of the intraoral digital scan. A preliminary intraoral scan of the tooth preparations is used to design a custom intraoral scan body which is manufactured using polymethylmethacrylate and a 5-axis milling machine. A low-viscosity polyvinyl siloxane impression of the tooth preparations is obtained using the custom intraoral scan body. Subsequently, the custom intraoral scan body is digitized using an intraoral scanner. A design software program is used to align the digitized custom intraoral scan body with the preliminary intraoral scan to obtain the definitive virtual cast. This technique aims to reduce manual conventional laboratory procedures such as pouring dental impression or die trimming which might minimize inaccuracies on the virtual definitive cast.

Accuracy of intraoral scans of edentulous jaws with different generations of intraoral scanners compared to laboratory scans

PURPOSE

Purpose of this in vitro study was to determine the accuracy of different intraoral scans versus laboratory scans of impressions and casts for the digitization of an edentulous maxilla.

MATERIALS AND METHODS

A PEEK model of an edentulous maxilla, featuring four hemispheres on the alveolar ridges in region 13, 17, 23 and 27, was industrially digitized to obtain a reference dataset (REF). Intraoral scans using Cerec Primescan AC (PRI) and Cerec AC Omnicam (OMN), as well as conventional impressions (scannable polyvinyl siloxane) were carried out (n = 25). Conventional impressions (E5I) and referring plaster casts were scanned with the inEOS X5 (E5M). All datasets were exported in STL and analyzed (Geomagic Qualify). Linear and angular differences were evaluated by virtually constructed measurement points in the centers of the hemispheres (P13, P17, P23, P27) and lines between the points (P17–P13, P17–P23, P17–P27). Kolmogorov-Smirnov test and Shapiro-Wilk test were performed to test for normal distribution, Kruskal-Wallis-H test, and Mann-Whitney-U test to detect significant differences in trueness, followed by 2-sample Kolmogorov-Smirnov test to detect significant differences in precision (P < .008).

RESULTS

Group PRI showed the highest trueness in linear and angular parameters (P < .001), while group E5I showed the highest precision (P < .001).

CONCLUSION

Intraoral scan data obtained using Primescan showed the highest trueness while the indirect digitization of impressions showed the highest precision. To enhance the workflow, indirect digitization of the impression itself appears to be a reasonable technique, as it combines fast access to the digital workflow with the possibility of functional impression of mucosal areas.

Intraoral scanners for capturing the palate and its relation to the dentition

Proper superimposition of intraoral scan generated 3D models enables detailed assessment of soft and hard tissue surface changes. This requires accurate 3D models and stable structures as superimposition references. In the maxilla, different reference areas have been proposed, mostly located at the palatal region. In this in vivo study we evaluated the precision of two intraoral scanners (TRIOS 3, 3Shape and CS 3600, Carestream) at the maxilla, focusing on the palate itself and also on its spatial relation to the dentition, following palatal superimposition. Precision was tested through the superimposition of repeated scans on the palate and the dental arch. Overall, the median precision of both scanners was high (< 0.1 mm). Scanner precision was comparable when the palatal area was tested individually. However, TRIOS 3 showed higher precision regarding the assessment of the dental arch, following superimposition of repeated models on the palate (median difference: approximately 40 μm). In few cases, local areas of higher imprecision were present for both scanners, exceeding 0.3 mm. Thus, scanner precision seems to be high in small, but slightly reduced considering larger areas, with differences between scanners. However, the effect on individual tooth position relative to the palate was for both scanners limited.

Clinical Applications of Intraoral Scanning in Removable Prosthodontics: A Literature Review

PURPOSE

This review aimed to identify the reported intraoral scanning applications in fabricating different types of removable prostheses in the field of prosthodontics.

METHODS

A comprehensive electronic search was performed using the PubMed and MEDLINE databases. This review included in vitro studies and clinical reports published between January 2013 and March 2021. The main keywords were as follows: intraoral scanning, digital impression, computerized digital impression, removable prosthesis, chairside computer-aided design/computer-assisted manufacturing, digital complete denture, digital immediate complete denture, digital interim complete denture, digital removable partial denture, digital removable overdenture, digital obturator, digital occlusal splints, and digital maxillofacial prostheses.

RESULTS

In total, 33 papers (22 clinical reports, 8 papers focused on dental techniques, and 3 clinical studies) were included in the final analysis.

CONCLUSIONS

The efficiency of using intraoral scanning in the field of removable prosthodontics was documented. However, there is a need for more clinical studies to identify intraoral scanning-usage protocols and to yield reliable and valid data.