Differences in maxillomandibular relationship recorded at centric relation when using a conventional method, four intraoral scanners, and a jaw tracking system: A clinical study

STATEMENT OF PROBLEM

Digital systems including intraoral scanners (IOSs) and optical jaw tracking systems can be used to acquire the maxillomandibular relationship at the centric relation (CR). However, the discrepancy of the maxillomandibular relationship recorded at the CR position when using digital methods remains uncertain.

PURPOSE

The purpose of this clinical study was to compare the accuracy of the maxillomandibular relationship recorded at the CR position using a conventional procedure, 4 different IOSs, and an optical jaw tracking system.

MATERIAL AND METHODS

A completely dentate volunteer was selected. A Kois deprogrammer (KD) was fabricated. Six groups were created based on the technique used to obtain diagnostic casts and record the maxillomandibular relationship at the CR position: conventional procedures (CNV group), 4 IOS groups: TRIOS4 (TRIOS4 group), iTero Element 5D (iTero group), i700 wireless (i700 group), Primescan (Primescan group), and a jaw tracking system (Modjaw) (Modjaw group) (n=10). In the CNV group, conventional diagnostic stone casts were obtained. A facebow record was used to mount the maxillary cast on an articulator (Panadent). The KD was used to obtain a CR record for mounting the mandibular cast, and the mounted casts were digitized by using a scanner (T710) to acquire the reference scans. In the TRIOS group, intraoral scans were obtained and duplicated 10 times. The KD was used to obtain a bilateral virtual occlusal record at the CR position. To acquire the specimens of the iTero, i700, and Primescan groups, the procedures in the TRIOS4 group were followed, but with the corresponding IOS. In the Modjaw group, the KD was used to record and export the maxillomandibular relationship at the CR position. Articulated virtual casts of each group were exported. Thirty-six interlandmark linear measurements were computed on both the reference and experimental scans. The distances obtained on the reference scan were used to calculate the discrepancies with the distances obtained on each experimental scan. The data were analyzed by using 1-way ANOVA followed by the pairwise comparison Tukey tests (α=.05).

RESULTS

The trueness and precision of the maxillomandibular relationship record were significantly affected by the technique used (P<.001). The maxillomandibular relationship trueness values from high to low were iTero (0.14 ±0.09 mm), followed by the Modjaw (0.20 ±0.04 mm) and the TRIOS4 (0.22 ±0.09 mm) groups. However, the iTero, Modjaw, and TRIOS4 groups were not significantly different from each other (P>.05). The i700 group obtained the lowest trueness and precision values (0.40 ±0.22 mm) of all groups tested, followed by the Primescan grop (0.26±0.13 mm); however, the i700 and Primescan groups had significantly lower trueness and precision than only the iTero group (P<.05).

CONCLUSIONS

The trueness and precision of the maxillomandibular relationship recorded at the CR position were influenced by the different digital techniques tested.

The impact of mandibular partial edentulous distal extension on virtual occlusal record accuracy when using two different intraoral scanners: An in vitro analysis

OBJECTIVES

This in vitro study was formulated to clarify how mandibular partial edentulous distal extension involving three missing teeth affects the virtual occlusal record (VOR) accuracy, in terms of both trueness and precision, when using two different intraoral scanners (IOSs) - the Primescan (PS) and Trios 4 (TR) scanners.

METHODS

A typodont model missing the left mandibular second premolar, first molar, and second molar as well as the right mandibular first molar was mounted on a semi-adjustable articulator. Four implants were placed at the sites of the missing mandibular teeth. Six pairs of stainless steel markers (diameter: 0.5 mm) were affixed to the maxillary and mandibular casts in the buccal gingiva adjacent to the implants and on the facial surfaces of teeth as reference positions for measurements. The model was digitized with an inEox X5 laboratory scanner to create a reference dataset. Intraoral scans were performed with the PS and TR scanners, with each scan duplicated 10 times to generate 20 paired IOS files. Automatic VOR generation followed the bilateral buccal scan protocol, divided into PS and TR groups (n = 10). Six subgroups of linear distances between interarch markers were assessed with Geomagic Control software, comparing deviations from the reference scan. Data normality was confirmed with the Shapiro-Wilk test. Trueness was evaluated with two-way ANOVAs and pairwise comparisons performed with Tukey's test, whereas precision was assessed with the Levene test (α=0.05).

RESULTS

The mean linear deviation (Δd) and standard deviation (SD) of VOR were both significantly affected by marker position (P < 0.001), and a significant position × scanner interaction was detected (P < 0.001). Negative mean deviations were observed for the distally extended edentulous areas in both groups. PS scans exhibited trueness that was significantly better than that for TR scans in the D16-46, D13-43, D23-33, and D27-37 subgroups (P < 0.05), whereas there were no significant differences in the D25-35 or D26-36 subgroups. PS scanning was associated with significantly better precision than TR scanning (P < 0.001), and worse precision was observed at D27-37 for both tested IOSs.

CONCLUSIONS

Mandibular partial edentulous distal extension can significantly affect VOR accuracy. The type of IOS could also affect VOR accuracy depending on the area being scanned, with better overall performance observed for the Primescan device as compared to the Trios 4 scanner. Both of these IOSs tended to underestimate VOR occlusal dimensions in mandibular distally extended edentulous areas.

CLINICAL SIGNIFICANCE

Mandibular distal edentulous areas can contribute to occlusal dimensions that are underestimated in digital workflows, which may result in infraocclusal discrepancies that arise when performing restorations. IOSs and VOR scanning protocols should thus be carefully considered in order to minimize these risks.

Evaluation Methods and Influencing Factors on Accuracy for Static Virtual Articulation Obtained by Intraoral Scanners: A Critical Review of the Literature

OBJECTIVE

Digital technology in dentistry has advanced rapidly in recent years, and as a result, the identification of static virtual articulation as a crucial stage in the digital process has attracted increasing attention. The use of intraoral scanners (IOSs) has made the acquisition of occlusal records more efficient. The purpose of this article is to review information on evaluation methods and influencing factors on the accuracy of static virtual articulation obtained by intraoral scanners.

OVERVIEW

An electronic search of the published literature was performed up to November 2023 using five databases: PubMed, Cochrane, Embase, Web of Science, and Scopus. The inclusion criteria were defined as relevant clinical or in vitro English studies on the accuracy of the occlusal relationship obtained using intraoral scanners. Therefore, a total of 30 articles were selected, reviewed, and discussed. Based on the results of the literature review, three methods have been used to evaluate the accuracy of virtual interocclusal records, including distance measurement (10 studies), occlusal contact analysis (13 studies), and deviation analysis after superimposing casts (8 studies). However, direct comparisons between these studies are challenging due to the different methods employed. Factors that were found to potentially impact accuracies, such as the range of vestibular scans, the number and position of virtual interocclusal records (VIRs), the location and extension of edentulous areas, alignment methods, and evaluation software programs have been extensively studied, but the extent to which these factors affect accuracy remains uncertain and varies depending on the specific circumstances.

CONCLUSIONS

A combination of multiple evaluation methods for a more rigid assessment of virtual interocclusal records may be a better approach. Attention should be given to the factors that may influence the accuracy of virtual interocclusal records. Future research should focus on optimizing these factors to improve the clinical applicability of virtual interocclusal records.

CLINICAL SIGNIFICANCE

In restorative dentistry, virtual interocclusal records obtained with intraoral scanners have been successfully used with acceptable accuracy, although they present some issues. Understanding the evaluation methods for virtual interocclusal records and the factors that may affect the accuracy of VIRs may lead to better use in clinical practice.

Accuracy of intraoral scanners for static virtual articulation: A systematic review and meta-analysis of multiple outcomes

STATEMENT OF PROBLEM

Static virtual articulation with intraoral scanners (IOSs) can eliminate the human errors related to conventional articulation methods and enhance accuracy. A systematic review and meta-analysis based on multiple accuracy outcomes can combine the available literature and provide an evidence-based conclusion.

PURPOSE

The purpose of this systematic review and meta-analysis was to investigate whether static virtual articulation with IOSs has acceptable accuracy for completely dentate and partially edentulous patients.

MATERIAL AND METHODS

An electronic search was conducted on the PubMed, Web of Science, and Scopus databases. In addition, a manual search through reference lists of selected articles was performed. Clinical and in vitro studies evaluating the accuracy of static virtual articulation with IOSs based on diagnostic accuracy, trueness, precision, and occlusion of fabricated fixed restorations were included. The pooled results included sensitivity, specificity, positive likelihood ratio (+LR), negative likelihood ratio (-LR), diagnostic odds ratios (DORs), mean values, and 95% confidence intervals (CIs). Results were presented as forest plots. The summary receiver operator characteristic (SROC) was displayed to summarize the diagnostic test performance.

RESULTS

The initial search resulted in a total of 5061 articles, of which 29 articles were included in the analysis. The virtual interocclusal records (VIRs) with IOSs showed acceptable pooled results for diagnostic accuracy (sensitivity: 0.76; specificity: 0.80; DOR: 14.77, area under the SROC (AUC): 0.87; cut off point Q∗: 80; +LR: 3.66; -LR: 0.31). The pooled data for trueness and precision were within the acceptable limits. The pooled mean (95% CI) for trueness based on linear deviations was 243.53 (144.90, 342.17). The pooled mean (95% CI) for precision based on 3D deviation of articulated models was 54.97 (43.49, 66.46). In addition, the included studies reported accurate occlusion for fixed restorations fabricated by using VIRs with IOSs. Moreover, most of the studies on trueness based on virtual occlusal contact area reported acceptable accuracy.

CONCLUSIONS

VIRs with IOSs had acceptable accuracy for static virtual articulation.

Does the available interocclusal space influence the accuracy of the maxillomandibular relationship captured with an intraoral scanner?

STATEMENT OF PROBLEM

The accuracy of a maxillomandibular relationship acquired by intraoral scanners (IOSs) has been previously analyzed; however, the impact of the interocclusal space on the accuracy of the maxillomandibular relationship remains unknown.

PURPOSE

The purpose of this in vitro investigation was to evaluate the influence of the interocclusal space (0, 1, 2, 3, or 4 degrees of incisal opening in the articulator) on the accuracy of the maxillomandibular relationship captured with an IOS.

MATERIAL AND METHODS

Markers were attached to the first molars and canines of maxillary and mandibular diagnostic casts, which were mounted on a semi-adjustable articulator, and digital scans were acquired (TRIOS 4). Both digital scans were duplicated 100 times and distributed into 5 groups depending on the incisal pin opening in the articulator (n=20): 0 (Group 0), 1 (Group 1), 2 (Group 2), 3 (Group 3), and 4 degrees (Group 4). In Group 0 (control), the casts were maintained in maximum intercuspation (MIP) with the incisal pin of the articulator set at 0 degrees. Then, a bilateral virtual occlusal record was acquired and automatically processed by using the IOS software program. A laboratory scanner (Medit T500) was used to digitize the mounted casts. The same procedures were completed in Groups 1, 2, 3, and 4 but with the incisal pin set at 1, 2, 3, and 4 degrees respectively. The interlandmark distances were used to calculate the discrepancies between the control and groups tested. One-way analysis of variance (ANOVA) and pairwise comparison Tukey HSD tests were used to inspect the data (α=.05).

RESULTS

The interocclusal space available when capturing the occlusal records affected the trueness of the maxillomandibular virtual relationship measured (P<.001). Group 0 (135 μm) obtained the highest distortion, while Group 3 (73 μm) and Group 4 (71 μm) showed the lowest distortion. Additionally, the interocclusal space available (P<.001) impacted the precision of the maxillomandibular virtual relationship measured. Group 0 (111 μm) obtained the highest distortion, while Group 4 (precision mean value of 59 μm) had the lowest distortion among the groups tested.

CONCLUSIONS

The interocclusal space available when acquiring virtual bilateral occlusal records using the IOS tested impacted the accuracy of the maxillomandibular relationship. The smallest available interocclusal space tested (maximum intercuspation) showed the worst trueness and precision mean values, while the group with the largest interocclusal space available had the highest trueness and precision mean values among the groups studied.

Discrepancies of centric occlusion located by using a conventional method and four intraoral scanners combined with a computer-aided design program: A pilot investigation

STATEMENT OF PROBLEM

Intraoral scanners (IOSs) can be used to record the maxillomandibular relationship at centric relation (CR). The articulated digital scans can be imported into a dental computer-aided design (CAD) program and used to locate centric occlusion (CO); however, the accuracy of the CO recorded by using IOSs and a dental CAD program remains unknown.

PURPOSE

The purpose of this clinical study was to compare the position of the CO located by using a conventional method and 4 IOSs combined with a dental CAD program.

MATERIAL AND METHODS

A patient volunteered to participate in this study. Conventional diagnostic stone casts were obtained. A facebow record (Kois Dentofacial Analyzer) was used to transfer the maxillary cast into a semi-adjustable articulator (Panadent PCH Articulator). A Kois deprogrammer (KD) was used to record the maxillomandibular relationship at CR and to transfer the mandibular cast into the articulator. Afterwards, CO was located in the articulated casts by removing the incisal pin and using an 8-µm articulating foil. CO was marked in the casts by using a blue articulating paper (control). Three groups were created based on the IOS used: TRIOS 4, iTero Element 5D Plus, i700, and Primescan. In each IOS group, a maxillary and mandibular scan were obtained. The scans were duplicated 10 times. Afterwards, a bilateral occlusal record captured with the KD was used to articulate each pair of duplicated scans. Each articulated specimen was imported into a CAD program (DentalCAD) and CO was virtually located. The teeth contacting at the CO of each specimen were compared with the control group. Categorical data were analyzed by using the chi-squared test (α=.05).

RESULTS

The chi-squared test revealed a significant association between the IOS system and the location of the CO (P=.004). The highest association was found between the TRIOS 4 and CO position, in which 100% of the specimens obtained the same CO position as in the conventional group. The lowest association was found between the i700 and CO position. In the i700 group, 20% of the specimens showed the same CO position as in the control group. A similar outcome was obtained in the iTero and Primescan groups. In both groups, 60% of the specimens demonstrated the same CO position as the control group.

CONCLUSIONS

The IOS system used to acquire articulated scans at CR impacted the CO position located by using the evaluated digital methods. The TRIOS 4 system was the only IOS that consistently reproduced the same CO position as the conventional method.

Influence of occlusal collision corrections completed by two intraoral scanners or a dental design program on the accuracy of the maxillomandibular relationship

STATEMENT OF PROBLEM

Occlusal collisions of articulated intraoral digital scans can be corrected by intraoral scanners (IOSs) or dental design software programs. However, the influence of these corrections on the accuracy of maxillomandibular relationship is unclear.

PURPOSE

The purpose of this clinical investigation was to measure the effect of occlusal collision corrections completed by the IOSs or dental design software programs on the trueness and precision of maxillomandibular relationship.

MATERIAL AND METHODS

Casts of a participant mounted on an articulator were digitized (T710). The experimental scans were obtained by using 2 IOSs: TRIOS 4 and i700. The intraoral digital scans of the maxillary and mandibular arches were obtained and duplicated 15 times. For each duplicated pair of scans, a bilateral virtual occlusal record was acquired. Articulated specimens were duplicated and assigned into 2 groups: IOS-not corrected and IOS corrected (n=15). In the IOS-not corrected groups, the IOS software program postprocessed the scans maintaining the occlusal collisions, while in the IOS-corrected groups, the IOS software program eliminated the occlusal collisions. All articulated specimens were imported into a computer-aided design (CAD) program (DentalCAD). Three subgroups were developed based on the CAD correction: CAD-no change, trimming, or opening the vertical dimension. Thirty-six interlandmark distances were measured on the reference and each experimental scan to compute discrepancies by using a software program (Geomagic Wrap). Root mean square (RMS) was selected to compute the cast modifications performed in the trimming subgroups. Trueness was examined using 2-way ANOVA and pairwise comparison Tukey tests (α=.05). Precision was evaluated with the Levene test (α=.05).

RESULTS

The IOS (P<.001), the program (P<.001), and their interaction (P<.001) impacted the trueness of the maxillomandibular relationship. The i700 obtained higher trueness than the TRIOS 4 (P<.001). The IOS-not corrected-CAD-no-changes and IOS-not-corrected-trimming subgroups obtained the lowest trueness (P<.001), while the IOS-corrected-CAD-no-changes, IOS-corrected-trimming, and IOS-corrected-opening subgroups showed the highest trueness (P<.001). No significant differences in precision were found (P<.001). Furthermore, significant RMS differences were found (P<.001), with a significant interaction between Group×Subgroup (P<.001). The IOS-not corrected-trimmed subgroups obtained a significantly higher RMS error discrepancy than IOS-corrected-trimmed subgroups (P<.001). The Levene test showed a significant discrepancy in the RMS precision among IOSs across subgroups (P<.001).

CONCLUSIONS

The trueness of the maxillomandibular relationship was influenced by the scanner and program used to correct occlusal collisions. Better trueness was obtained when the occlusal collisions were adjusted by the IOS program compared with the CAD program. Precision was not significantly influenced by the occlusal collision correction method. CAD corrections did not improve the results of the IOS software. Additionally, the trimming option caused volumetric changes on the occlusal surfaces of intraoral scans.

Impact of scanning range and image count on the precision of digitally recorded intermaxillary relationships in interocclusal record using intraoral scanner

PURPOSE

The effect of scan range and the number of scanned images on the precision of in vivo intermaxillary relationship reproduction was evaluated using digital scans acquired with an intraoral scanner.

METHODS

The study involved 15 participants with normal occlusion. Two different interocclusal recording settings were employed using the intraoral scanner (TRIOS 4): 'MIN,' focusing on the minimal scan range of the first molar region, and 'MAX,' including the scan range from the right first premolar to the right second molar. These settings were combined with three different image counts, resulting in six experimental conditions. Interocclusal recordings were performed four times for each condition. Dimensional discrepancies between datasets were analyzed using three-dimensional morphometric software and compared using two-way analysis of variance.

RESULTS

Median dimensional discrepancies (interquartile range; IQR) of 39.2 (30.7-49.4), 42.2 (32.6-49.3), 30.3 (26.8-44.1), 20.1 (16.0-34.8), 21.8 (19.0-25.1), and 26.6 (19.9-34.5) µm were found for MIN/200, MIN/400, MIN/600, MAX/200, MAX/400, and MAX/600, respectively. Significant differences in dimensional discrepancies according to scan range were found. Wilcoxon signed-rank test showed significant differences between MAX and MIN (P < 0.01).

CONCLUSION

Scan range may affect the precision of intermaxillary relationship reproduction. Thus, scanning of the most extensive region practically achievable is recommended.

Evaluation of repeatability of different alignment methods to obtain digital interocclusal records: An in vitro study

STATEMENT OF PROBLEM

The alignment of the maxillary and mandibular digital scans obtained with an intraoral scanner (IOS) generates digital interocclusal records. Although the accuracy of maxillary and mandibular digital scans obtained from an IOS is widely studied, the accuracy of digital interocclusal records obtained with them is not; even less studied is the accuracy (trueness and precision) of the alignment methods that are available to obtain them.

PURPOSE

The purpose of this in vitro study was to assess the precision under repeatability conditions (repeatability) of the different alignment methods used to obtain digital interocclusal records.

MATERIAL AND METHODS

Digital scans of maxillary and mandibular casts of a dentate healthy adult were acquired with an IOS. Casts were then mounted in maximum intercuspal position in a semi-adjustable mechanical articulator (1801 AR Model PSH Articulator), and left and right occlusal digital scans were acquired with the IOS. Occlusal digital scans were repeated 7 times under repeatability conditions. After obtaining each pair of occlusal digital scans, the software program of the IOS automatically aligned the maxillary and mandibular digital scans with occlusal digital scans (TRI method), resulting in 7 digital interocclusal records composed of aligned maxillary and mandibular digital scans and occlusal digital scans. All 7 sets of aligned digital scans were exported and realigned in a dental computer-aided design software program by means of global and reference alignment methods (EXO-B and EXO-R methods, respectively). To assess the repeatability, the 7 aligned digital scan sets of each group were repositioned in the common coordinate system by aligning maxillary digital scans, and repeatability was calculated in terms of the distance between the vertices of the mandibular digital scans for each of the possible nonrepeating combinations of pairs (7C2=21). The repeatability was tested by using the Kruskal-Wallis test for nonparametric distribution followed by the Mann-Whitney U test and Bonferroni correction for pairwise comparisons (α=.05).

RESULTS

The median with interquartile range for the TRI alignment method was 47 (27) μm for the EXO-B method 41 (25) μm and 16 (5) μm for EXO-R. The Kruskal-Wallis test showed statistical difference between test groups (P<.05). The post hoc Dunn test with Bonferroni adjustment detected significant statistical differences between the EXO-R-TRI (P<.001) and EXO-R-EXO-B (P<.001) alignment methods.

CONCLUSIONS

This study found that the alignment method could influence the repeatability of digital interocclusal records. The reference best-fit alignment method (EXO-R) provided better repeatability.

Virtual occlusal records acquired by using intraoral scanners: A review of factors that influence maxillo-mandibular relationship accuracy

PURPOSE

This review aims to provide a comprehensive summary of how much progress has been made in the field of virtual occlusal records (VOR) obtained with intraoral scanners (IOSs), their accuracy, and what factors influence their accuracy.

MATERIALS AND METHODS

An electronic search was performed in MEDLINE via PubMed and Scopus databases in February 2023. Eligible articles were clinical or in vitro studies evaluating the accuracy of virtual occlusal records with intraoral scanners in completely dentate and partially edentulous arches.

RESULTS

Virtual occlusal records have shown promising results in terms of accuracy, with some studies reporting a high level of agreement with traditional methods. Key factors influencing the accuracy of VOR through intraoral scanners were identified which encompass multiple parameters such as scanner brands, imaging technology, scan quality, best-fit alignment, software algorithms, intermesh penetrations, and the number of sections and dimensions of the virtual occlusal record. In partially edentate areas, the lack of landmarks in the edentulous area compromises the accuracy of VOR, thus limiting the use of IOS in patients with missing teeth.

CONCLUSION

Understanding and recognizing these influencing factors will increase the predictability and reliability of dental treatments completed by using digital workflows.  However, certain challenges need to be addressed which can influence its accuracy and limit its use in daily practice. Future research should focus on improving these factors to enhance the clinical applicability of virtual occlusal records.

Factors that influence the accuracy of maxillomandibular relationship at maximum intercuspation acquired by using intraoral scanners: A systematic review

OBJECTIVE

To review the factors that influence the accuracy of the maxillomandibular relationship at maximum intercuspation (MIP) acquired by using intraoral scanners (IOSs).

MATERIAL AND METHODS

A systematic search was performed using five databases: MEDLINE/PubMed, Cochrane, Embase, World of Science, and Scopus. A manual search was also completed. Studies assessing the factors that influence the MIP acquired by using IOSs were included and organized based on the analyzed factor. Studies were evaluated by applying the Joanna Briggs Institute Critical Appraisal Checklist.

RESULTS

Twenty-nine articles were included. Seven factors have been identified: IOS system, scan extension, edentulous areas, number, location, and extension of occlusal records, occlusal force, tooth mobility, and alignment methods. Nine studies evaluated the influence of IOS system. Four studies assessed the influence of the extension of the arch scan. Three studies evaluated the effect of edentulous spaces. Four studies agreed on the impact of the number, location, and extension of the occlusal records on the MIP accuracy. One study assessed the influence of the occlusal force, showing a smaller average interocclusal space with increased occlusal force. One study evaluated the influence of tooth mobility. Seven studies analyzed the influence of the alignment method on the MIP accuracy.

CONCLUSIONS

Most of the studies reported no difference on the MIP accuracy between half- and complete-arch scans. Areas with 2 or more missing teeth reduce the MIP accuracy. A bilateral and frontal record including 2 teeth or a bilateral posterior occlusal including at least 4-teeth is indicated for maximizing the MIP accuracy.

CLINICAL IMPLICATIONS

When a complete-arch intraoral scans is obtained, a bilateral and frontal record including 2 teeth or a bilateral posterior occlusal record including at least 4-teeth is recommended for maximizing the accuracy of the MIP. When a half-arch intraoral scan is acquired, a posterior occlusal record including at least 4-teeth is indicated for optimizing the accuracy of the MIP.

Accuracy of optical interocclusal registration using an intraoral scanner

PURPOSE

This study aimed to clarify the effect of occlusal force on appropriate optical interocclusal registration in clinical practice, considering periodontal ligament and jawbone deformation.

METHODS

Forty participants with natural, healthy dentition were enrolled (19 men and 21 women; mean age, 27.7 ± 2.0 years). A TRIOS3 intraoral scanner was used to scan the right lateral first premolar to the second molar areas of the upper and lower jaws. During scanning for interocclusal registration, participants were instructed to "bite normally," "bite lightly," and "bite strongly" to obtain data for the three occlusal patterns. The standard triangulated language (STL) data for each occlusion condition were superimposed using the appropriate software, following which the tooth displacement was calculated. The conventional method was also used to record the occlusal contact area for a silicone model using a dental contact analyzer.

RESULTS

Tooth displacement was significantly lower for the strong-bite condition than for the weak-bite condition (0.018 mm vs. 0.028 mm, P<0.05). As the occlusal force increased, the occlusal contact area also increased, and significant differences were observed among the different occlusal conditions (P<0.05).

CONCLUSIONS

Occlusal contact area changed depending on the bite force when using the silicone impression or optical intraoral scanning methods. Moreover, using optical impression methods in "strong bite force" may reduce the deviation and allow for stable interocclusal registration.

Digital mounting accuracy of 2 intraoral scanners with a single anterior or bilateral posterior occlusal scan: A three-dimensional analysis

STATEMENT OF PROBLEM

Although intraoral scanners (IOSs) are popular, few studies have evaluated the accuracy of digital mounting by using IOSs.

PURPOSE

The purpose of this in vitro study was to compare the accuracy of digital mounting by using 2 IOSs and 2 occlusal scanning methods.

MATERIAL AND METHODS

Fourteen Ø5-mm zirconia balls were attached approximately 5 mm apical to the free gingival margin of both second molars, second premolars, and canines and between the central incisors in maxillary and mandibular epoxy casts. A polyetheretherketone hexagonal cube with a 10-mm-long edge was attached to the buccal side of the missing mandibular right first molar area, and the cube was used to set a part coordinate system. Two IOSs (TRIOS 3, Primescan) were used to assess the intra-arch and interarch accuracies. For intra-arch assessment, each IOS was used to digitally scan the mandibular epoxy cast 15 times and fabricate 15 datasets. The deviation of each zirconia ball centroid was statistically compared between the IOSs. For interarch assessment, each IOS was used to digitally scan the maxillary and mandibular epoxy casts, and the data were digitally mounted by using a single anterior occlusal scan (A) or bilateral posterior occlusal scan (P). Both occlusal scans were performed 15 times; therefore, 4 groups (15 datasets per group) of mounted digital datasets were assigned. The deviation of each maxillary zirconia ball centroid, as well as the interarch distance between the corresponding maxillary and mandibular zirconia ball centroids, were compared among the 4 groups. For statistical analysis, the Mann-Whitney U test and Kruskal-Wallis test with Bonferroni correction were used (α=.05).

RESULTS

Primescan had less deviation than TRIOS 3 in the complete arch scan. When the zirconia balls were close to the origin, the bilateral posterior occlusal scan produced less deviation of their centroids. Primescan produced decreased interarch distance in the anterior and posterior dentition, while TRIOS 3 produced increased interarch distance in the anterior dentition and decreased interarch distance in the posterior dentition.

CONCLUSIONS

A significant difference was noted in intra-arch accuracy between the IOSs, and the difference influenced the digital mounting accuracy. The type of occlusal scan and IOS significantly influenced the accuracy of digital mounting. Both IOSs produced decreased interarch distances in the second molar area.

Assessment of physiological posterior-tooth displacement under habitual occlusal force by intraoral scanning using implant-supported crowns as the reference

STATEMENT OF PROBLEM

Studies that have used digital methods to quantitatively evaluate physiological tooth displacement under occlusal force are sparse.

PURPOSE

The purpose of this clinical study was to measure physiological posterior tooth displacement under occlusal force by intraoral scanning and reverse engineering technology by using implants as the reference.

MATERIAL AND METHODS

A total of 14 participants received 15 implant-supported single mandibular first molar crowns. The surface data of maxillary and mandibular posterior teeth (U1 and L1) and the buccal occlusal data in the maximum intercuspal position (MIP) with habitual occlusal force were obtained by using an intraoral scanner (TRIOS 3, v20.1.2). The U1 and L1 data were segmented into single teeth, which were then aligned to the buccal occlusal data by using the "best-fit alignment" command to build the data under occlusal force (U2 and L2). U1 and L1 data were compared with U2 and L2 data to calculate the centroid and functional cusp vertex displacements and the long axis deflections of the second premolars and second molars, taking the first molar as the reference. The medians, and first quartile (Q₁), third quartile (Q₃) of the above data were reported, and the Shapiro-Wilk and Wilcoxon tests were used to analyze the differences (α=.05).

RESULTS

Under occlusal force, the median (Q₁, Q₃) centroid displacements of posterior teeth ranged from 61 (52, 101) μm to 146 (80, 186) μm; the functional cusp vertex displacements ranged from 82 (62, 117) μm to 146 (98, 189) μm, and the long axis deflections ranged from 0.45 (0.25, 0.87) degrees to 1.03 (0.52, 1.41) degrees. Mandibular second premolars displaced lingually, mesially, and apically; mandibular second molars displaced distally and apically; and maxillary second premolars and second molars displaced lingually and apically.

CONCLUSIONS

A digital method taking implant-supported single crowns as the reference was used to demonstrate physiological posterior-tooth displacement under habitual occlusal force.

Influence of the Number of Teeth and Location of the Virtual Occlusal Record on the Accuracy of the Maxillo-Mandibular Relationship Obtained by Using An Intraoral Scanner

PURPOSE

To assess the influence of the number of teeth (2, 3, or 4) and location (molars, molar and premolar, or premolars and canines) of the bilateral virtual occlusal record on the accuracy of the virtual maxillo-mandibular relationship acquired by an intraoral scanner (IOS).

MATERIAL AND METHODS

Diagnostic casts mounted on a semi-adjustable articulator were obtained. Four markers were adhered on the facial surfaces of the first molars and canines. The mounted casts were digitized using an extraoral scanner. Maxillary and mandibular intraoral digital scans were obtained using an intraoral scanner (TRIOS 4). The maxillary and mandibular digital scans were duplicated 105 times and divided into 7 groups based on the number of teeth (2, 3, or 4) and location (molar, molar and premolar, or premolars and canines) of the bilateral virtual occlusal records (n = 15). The alignment of the scans was automatically performed after the acquisition of the corresponding occlusal records by the IOS program. Eight linear distances between the gauge balls were computed on the reference scan and on the 105 digital scans. The distances obtained on the reference scan were used to calculate the discrepancies with the distances obtained on each experimental scan. The Shapiro-Wilk test showed that the data was normally distributed. The trueness and precision data were analyzed using 2-way ANOVA followed by pairwise comparison Tukey tests (α = 0.05).

RESULTS

Two-way ANOVA showed that the number of teeth (p < 0.001) and the position of the virtual occlusal record (p < 0.001) were significant factors on the accuracy of the maxillo-mandibular relationship. Tukey test showed significant overall mean differences between the different groups tested: the 4-teeth group obtained the highest trueness, and the 2-teeth group showed the lowest trueness values (p < 0.001). Tukey test showed significant trueness differences between the virtual occlusal record locations. The 2-teeth record located more posteriorly obtained the lowest trueness. Significant differences in precision values were found among the subgroups tested (p < 0.001). The 2-teeth group obtained significantly more precision values than the 3- and 4-teeth groups. Additionally, there was a significant difference in precision values between the subgroup tested in which the first molar and second premolar location had the highest precision, while the first and second premolar's location obtained the lowest precision.

CONCLUSIONS

The number of teeth and the location of the bilateral virtual occlusal record influenced the accuracy of the virtual maxillo-mandibular relationship obtained by the intraoral scanner tested. The more teeth included in the bilateral virtual occlusal record, the higher the accuracy of the maxillo-mandibular relationship. Additionally, the more anteriorly located the virtual bilateral occlusal record involving 2 or 3 teeth was, the higher the accuracy mean value.

In vivo precision of digital static interocclusal registration for full arch and quadrant arch scans: a randomized controlled clinical trial

BACKGROUND

Clinical studies comparing the accuracy of digital and conventional records for static interocclusal registration are lacking. Therefore, the purpose of this clinical study was to assess the precision of digital interocclusal registration compared to conventional registration for full arch and quadrant arch conditions.

METHODS

Nine individuals with complete natural dentition were enrolled in this study. Each participant received digital scans, conventional impressions, and static interocclusal records according to the following groups: group DF, full arch digital scans and bilateral buccal scans with Medit i700 intraoral scanner (IOS); group DQ, quadrant arch digital scans and unilateral buccal scans with Medit i700 IOS; group CF, full arch polyvinyl siloxane (PVS) impressions and PVS interocclusal records; group CQ, quadrant arch PVS impressions and PVS interocclusal records. For group CF and group CQ, the impressions were poured, mounted with the silicone bites, scanned with a laboratory scanner, and articulated virtually with buccal scans with the laboratory scanner. In each group, each participant received three interocclusal records to repeat the virtual articulation three times and the articulated models were saved as STL files. The STL files were imported into a 3D-processing software to calculate the discrepancies between repeated measures using best-fit-alignment method. The significance between the study groups was calculated with two-tailed paired t-test at P < 0.05.

RESULTS

For full arch, group DF showed significantly better precision with a mean value of 31 ± 19 µm compared to 204 ± 81 µm for group CF (P = 0.0003). Similarly, for quadrant arch, group DQ showed significantly better precision with a mean value of 18 ± 6 µm compared to 255 ± 136 µm for group CQ (P = 0.0009). No significant difference in precision was found between quadrant arch and full arch when the digital or the conventional method was used.

CONCLUSIONS

The digital approach had significantly better precision for static interocclusal registration compared to the conventional method in both full and quadrant arch situations. Trial Registry This clinical trial was registered on 06/07/2022 in the Pan African Clinical Trial Registry database, the number for the registry is PACTR202207648490275.

Reliability and Time Efficiency of Digital vs. Analog Bite Registration Technique for the Manufacture of Full-Arch Fixed Implant Prostheses

Objective: Information about full-digital protocols for bite registration with intraoral scanners on multiple implants in the edentulous jaw is scarce. The purpose of this comparative in vivo study was to investigate the reliability and time efficiency of a novel full-digital bite registration technique for the manufacture of full-arch maxillary fixed implant prostheses. Material and methods: In ten patients, a full-arch maxillary fixed implant prosthesis was manufactured on multi-unit abutment level through an analog prosthetic workflow. The bite registration was performed with use of a screw-retained polymethyl methacrylate (PMMA) verification jig with detachable wax rim. To articulate the definitive edentulous maxillary implant cast in centric relation at the appropriate occlusal vertical dimension (OVD) to the mandibular antagonist cast, a type II articulator (Artex, Amann Girrbach) was used. Three to six months later, a full-digital bite registration was performed with use of dual-function scan bodies and bilateral connected bite pillars. The bite pillars screwed into the scan bodies were used to adjust and articulate the edentulous maxillary implant arch to the mandibular antagonist arch at the defined OVD. Treatment time for analog and digital bite registration technique was measured in each patient. The reliability of the digital bite registration technique was evaluated by 3D comparison of two sets of stereo lithographic (STL) files obtained from each patient. The three-dimensional deviation was defined along the X-, Y- and Z-axes (Geomagic Control X, 3D Systems Inc., Rock Hill, SC, USA). Results: The treatment time for digital bite registration using dual-function scan bodies and bite pillars was significantly shorter than analog bite registration with verification jig and wax rim (60.30%, SD 5.72%). Minor differences between the two techniques were observed with a linear deviation range of 1115 µm (SD 668 µm) overall, 46.2 µm (SD 731.3 µm) along the X-axis, −200.3 µm (SD 744.3 µm) along the Y-axis and 67.1 µm (SD 752.2 µm) along the Z-axis. Bilateral balanced contacts were registered in all patients during full-digital bite registration. Conclusions: The novel digital bite registration technique with dual-function scan bodies and bite pillars allows for a full-digital workflow for full-arch implant supported restorations. The digital bite workflow was 60% faster, and the overall deviation was around 1 mm, which can be considered clinically acceptable.

An In-Vitro Evaluation of Articulation Accuracy for Digitally Milled Models vs. Conventional Gypsum Casts

With the advent of a digital workflow in dentistry, the inter-occlusal articulation of digital models is now possible through various means. The Cadent iTero intraoral scanner uses a buccal scan in maximum intercuspation to record the maxillomandibular relationship. This in-vitro study compares the occlusion derived from conventionally articulated stone casts versus that of digitally articulated quadrant milled models. Thirty sets of stone casts poured from full arch polyvinyl siloxane impressions (Group A) and thirty sets of polyurethane quadrant models milled from digital impressions (Group B) were used for this study. The full arch stone casts were hand-articulated and mounted on semi-adjustable articulators, while the digitally derived models were pre-mounted from the milling center based on the data obtained from the buccal scanning procedure. A T-scan sensor was used to obtain a bite registration from each set of models in both groups. The T-scan data derived from groups A and B were compared to that from the master model to evaluate the reproducibility of the occlusion in the two groups. A statistically significant difference of the contact region surface area was found on #11 of the digitally articulated models compared to the master. An analysis of the force distribution also showed a tendency for a heavier distribution on the more anterior #11 tooth for the digitally articulated models. Within the limitations of this study, the use of a digitally articulated quadrant model system may result in a loss of accuracy, in terms of occlusion, the further anteriorly the tooth to be restored is located. Care must be taken to consider the sources of inaccuracies in the digital workflow to minimize them for a more efficient and effective restorative process.

Clinical evaluation of the precision of interocclusal registration by using digital and conventional techniques

STATEMENT OF PROBLEM

Although studies have evaluated the accuracy of data obtained by intraoral scanners (IOSs), studies on the precision of interocclusal registrations made with IOSs are lacking.

PURPOSE

The purpose of this clinical study was to compare the precision of IOS interocclusal registration with that of conventional methods with a silicone impression material and a gypsum cast.

MATERIAL AND METHODS

Eight participants with complete natural dentitions were enrolled. Images of their maxillary and mandibular quadrant arches and their interocclusal relationship were scanned with 2 IOSs: the 3M True Definition Scanner and the TRIOS Scanner 3. In the conventional method, impressions of complete-arch dentition and quadrant-arch dentition were made with a silicone impression material, and gypsum casts were fabricated, mounted on a dental articulator related with a silicone interocclusal record, and scanned with a 3D laboratory scanner. These procedures were repeated 4 times, and 4 sets of interocclusal registration data in standard tessellation language (STL) format were generated for each condition. Interocclusal registration precision was evaluated by determining the discrepancy of the STL data between repeated measurements by using the best-fit-algorithm method.

RESULTS

The average discrepancies for all participants were 25 ±12 μm for the True Definition, 31 ±7 μm for the TRIOS 3, 154 ±59 μm for the complete arch, and 128 ±33 μm for the quadrant arch. The Kruskal-Wallis test revealed that the effect of the impression methods on the discrepancy was statistically significant (P<.001). The Steel-Dwass test showed that both digital scan methods exhibited significantly smaller discrepancies than the 2 conventional methods (P=.005).

CONCLUSIONS

These results suggest that the intermaxillary relationship captured by the digital scan method by using IOSs had better precision than that obtained by the conventional method.

Fully digital fabrication of an occlusal device using an intraoral scanner and 3D printing: A dental technique

This dental technique describes a fully digital method for fabricating occlusal devices using a complete-arch intraoral scan and 3D printing. The maxillary and mandibular arches of a healthy, fully dentate volunteer were digitized using an intraoral scanner. A second scan and modified recording of the centric relation enabled a virtual arrangement of the maxillary and mandibular arches, both in centric relation and in the desired vertical dimension of occlusion. An occlusal device was subsequently designed virtually and fabricated from a light-polymerizing acrylic resin using a 3D printer. The occlusal device was tested for fit, occlusion, and patient-friendly handling. As only minor occlusal corrections were required, the fully digital procedure described is suitable for the fabrication of occlusal devices.