Clinical study comparing the accuracy of interocclusal records, digitally obtained by three different devices

Evaluation of efficacy of digital or virtual bite registration over conventional techniques- A systematic review

Background

Bite registration procedures have been transformed by the digital revolution in dentistry, thus it is now necessary to compare the accuracy of digital or virtual techniques to conventional ones.

Aim

To assess the accuracy of digital or virtual bite registration systems in comparison to conventional methods to clarify any potential advantages or disadvantages.

Methodology

A thorough search in numerous databases, including PubMed, Embase, the Cochrane Library, Scopus, and Web of Science, was carried out in accordance with PRISMA criteria. The review focused on the accuracy of digital or virtual bite registration and covered a variety of study formats, including randomized controlled trials, clinical studies, and in-vitro investigations. For each of the included 7 studies, a thorough assessment of bias was conducted using the Newcastle-Ottawa Scale and the Cochrane Risk of Bias tool. As there would be expected variability in study designs, data synthesis required both a narrative explanation of the results and a qualitative synthesis.

Results

This systematic review compared 7 studies on traditional bite registration methods versus digital/virtual techniques. Digital techniques highlighted improved efficiency and innovation with increased speed, accuracy, and integration advantages. Evaluations performed with the Newcastle-Ottawa Scale and ROBINS-I tool showed little bias in cross-sectional studies. Nevertheless, in vitro studies have identified biases in participant selection and result reporting, indicating a need for better study rigor and reporting standards. A study received a noteworthy 8 out of 9 score on the Newcastle-Ottawa Scale, indicating strong methodology with careful sample selection, solid comparability, and comprehensive outcome evaluation, enhancing its credibility in assessing bite registration techniques.

Conclusion

The benefits of digital/virtual bite registration methods over traditional ones are demonstrated in this systematic review, which also shows how these methods improve speed, accuracy, and integration. Although some studies have shown biases, overall results support the validity and efficiency of digital techniques in improving dental practice.

Accuracy and precision of intraoral scanners for shade matching: A systematic review

STATEMENT OF PROBLEM

The use of intraoral scanners is rising in prosthetic dentistry; however, systematic analysis of their accuracy and precision for shade matching is scarce.

PURPOSE

The purpose of this systematic review was to evaluate the accuracy and precision of intraoral scanners for shade matching.

MATERIAL AND METHODS

In addition to a manual search, an electronic systematic search was conducted on MEDLINE/PubMed, EMBASE, Web of Science, Cochrane, and Scopus databases. English-language original studies published between January 1, 2010 and March 1, 2022 with intraoral or digital scanners were chosen based on the keywords of tooth color or shade selection or determination, color or shade matching, accuracy, validity, or trueness, and precision, repeatability, or reproducibility as inclusive criteria. Two reviewers independently performed the literature search, selected the studies, collected the data from the studies included, and evaluated the quality of the studies included using a quality assessment method and the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies. A third reviewer resolved disagreements.

RESULTS

A total of 17 articles concerning the shade matching accuracy and precision of intraoral scanners were selected and reviewed. Among them, 4 articles evaluated only accuracy, 4 articles assessed only precision, and 9 articles investigated both accuracy and precision. Ten articles reported low levels of shade matching accuracy for intraoral scanners, while 11 articles reported high levels of shade matching precision for intraoral scanners.

CONCLUSIONS

Based on the current literature, intraoral scanners show acceptable precision but unacceptable accuracy for shade matching.

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.

An innovative evaluation method for clinical comparative analysis of occlusal contact regions obtained via intraoral scanning and conventional impression procedures: a clinical trial

OBJECTIVES

To compare the occlusal contact regions (OCRs) obtained through an intraoral scanning system and conventional impression procedures via an innovative evaluation method.

MATERIALS AND METHODS

Fifteen participants with complete dentitions and stable centric occlusion were included. Three groups were created based on the technique used to obtain the OCRs of quadrant posterior teeth at the maximal intercuspal position: 100 μm articulating paper (Control), an intraoral scanner (Test 1, T1) and conventional impression procedure (Test 2, T2). OCRs of control group were digitized by the intraoral scanner, while all conventional impressions were cast and digitized by an extraoral scanner. The virtual occlusal records of the 2 test groups were obtained by buccal bite registration. The OCRs within 100 μm in the 3 groups were three-dimensionally superimposed based on the tooth surfaces and the area of OCRs (SC, ST1, ST2) was calculated. The area of overlapping OCRs (SO) between the test groups and the control group was calculated. In the two test groups, the consistency rate of OCRs (SO/SC) and the positive rate of OCRs (SO/ST) were calculated and compared. For occlusal tightness evaluation, the mean occlusal clearances (OC) as well as minimum OC between the upper and lower models were calculated and compared.

RESULTS

The consistency rate of OCRs was 0.73 ± 0.17 for T1 group and 0.23 ± 0.13 for T2 group (p < 0.001). The positive rate of OCRs was 0.67 ± 0.15 for T1 group and 0.56 ± 0.23 for T2 group (p = 0.143). The mean OC was 51.32 ± 16.04 μm for T1 group and 68.20 ± 18.15 μm for T2 group (p = 0.024). The minimum OC was - 61.74 ± 35.38 μm for T1 group and 4.09 ± 27.15 μm for T2 group (p < 0.001).

CONCLUSIONS

For obtaining occlusal records in the quadrant posterior region, the tested intraoral scanning system was more reliable for recording occlusal contact regions and showed higher occlusal tightness compared with conventional impression procedures.

CLINICAL RELEVANCE

(1) The evaluation method can assist clinicians in making more objective analysis and comparisons among different sources of virtual occlusal records. (2) Occlusal tightness is a key and indispensable indicator in the evaluation of virtual occlusal records, and it can be quantified by measuring the occlusal clearance utilizing the current evaluation method.

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.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL SIGNIFICANCE

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

Insights into Occlusal Analysis: Articulating Paper versus Digital Devices

Background: As the demand for digital dentistry constantly increases, digital devices are gradually replacing conventional methods of recording occlusal contacts. The study aimed to assess the inter-rater reliability of occlusal contact point detection using 40 μm articulating paper, Medit i700, and OccluSense and to compare the distribution of occlusal contacts using the articulating paper and intraoral scanner. Material and Methods: The study included 25 participants aged 20 to 30 (13 women and 12 men). Photographs of contact points were taken and marked in maximum intercuspal position (MIP), in protrusive and laterotrusive movements, on working and non-working sides using 40 μm articulating paper and digital devices. The Cohen's Kappa coefficient assessed the inter-rater reliability. The Wilcoxon signed-rank test was used to compare dependent groups, articulating paper, and Medit i700. Results: The Cohen's Kappa index showed that almost perfect agreement was achieved with 40 μm articulating paper. Compared to Medit i700, the 40 μm articulating paper showed an increased mean number of contacts per tooth, except for the third molars. Conclusions: The 40 μm articulating paper has detected more overall contacts than the digital devices, particularly in the posterior areas. An ideal method for registering occlusal contacts has not been established yet.

Recording maximal intercuspation and border positions of the mandible with intraoral scanner using the acquisition software's multi-occlusion function

PURPOSE

This in vitro study was conducted to investigate the accuracy of intraoral scanner (IOS) for recording maximal intercuspal position (MIP) and border positions of the mandible.

MATERIALS AND METHODS

Maxillary and mandibular master casts were articulated in MIP, protrusive, and lateral interocclusal position sequentially on a semi-adjustable articulator. For each articulation relation, sites of occlusal contacts (SOCs) and sites of clearance (SCs) were identified on the master casts with articulating paper (reference sites). IOS was used to take full arch scans and nine virtual interocclusal records (VIRs) for virtual articulation of models. Virtual SOCs and SCs were detected with 3D processing software and compared to those identified with the articulating paper. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each articulation relation.

RESULTS

For MIP, IOS showed adequate sensitivity and NPV of 100%, and specificity and a PPV of 99%. For protrusive position, the IOS showed a sensitivity and a NPV of 100%, a high PPV of 86%, and a specificity of 83%. For lateral positions, the specificity and the PPV were high (93% and 79%, respectively), but the sensitivity and the NPV were below the clinically acceptable limits (28% and 56%, respectively).

CONCLUSION

IOS displayed clinically acceptable accuracy for recording MIP and protrusive border mandibular position. However, IOS had less accuracy for lateral border mandibular position.

Improving the precision of recordings acquired with digital occlusal analyzers: A dental technique

A technique to improve the precision of recordings acquired with the 2 main digital occlusal analyzers on the market (T-Scan and OccluSense) is presented. This technique consists of using digital occlusal analyzers with a customizable centering tray. The virtual design of the centering tray is available online, together with that of the adapters required for both digital occlusal analyzers. The designs can be downloaded and additively manufactured for clinical use. These parts improve the positioning of the piezoelectric film sensors of the digital occlusal analyzers in the patient's mouth and thus the precision of their records. Improving the precision of the records of the digital occlusal analyzers is especially important for the comparison of records obtained at different stages of rehabilitation treatment.

In vivo evaluation of T-Scan in quantifying occlusal contact

BACKGROUND

The T-scan system has been used previously to analyse occlusion, but the quantitative analysis of occlusal contact by T-Scan system has yet to be reported.

OBJECTIVES

To evaluate the reliability and validity of T-Scan system for quantitatively measuring occlusal contact area and occlusal contact number.

METHODS

Twenty-two individuals with normal occlusion, 11 men and 11 women, were recruited for the study. Two occlusal analysis methods, including silicone transmission analysis method (STA) and T-Scan occlusion analysis method (TSO), were used to make quantitative analysis to measure occlusal contact area (OCA) and occlusal contact number (OCN). A test-retest check was performed with an interval of 2 weeks. The values of intraclass correlation coefficients (ICC) between test-retest of each method were calculated for reliability evaluation. Pearson correlations analysis, paired t-tests, regression analysis and Bland-Altman analysis were performed for validity evaluation.

RESULTS

The ICC values of STA were greater than those of TSO for OCA while for OCN, ICC values of TSO were greater than STA. The higher OCA and OCN values were found in TSO compared with STA. Pearson's correlation coefficient indicated strong relations between TSO and STA (0.730-0.812) for OCA, while good relations between then (0.569-0.583) for OCN. Paired t-test showed a significant difference between the OCA and OCN values between TSO and STA. Bland-Altman analysis showed good agreement between OCA and OCN values of TSO and STA both in men and women. Regression analysis identified a linear correlation between OCA values obtained from these two methods.

CONCLUSIONS

T-Scan method showed strong reliability for measuring OCA and OCN quantitatively. Strong correlations were found between OCA values from TSO and STA method, but the validity of TSO for measuring OCN needs to be promoted.

CLINICAL SIGNIFICANCE

T-Scan system demonstrates good potential in quantitative analysis of occlusion, which will expand its clinical application.

Reliabilty of recording occlusal contacts by using intraoral scanner and articulating paper - A prospective study

OBJECTIVE

The recording of occlusal contacts is a pivotal step in many dental procedures, yet the lack of a standardized method could introduce clinical errors. The aim of this study was to compare the occlusal contacts recorded using a intraoral scanner to the contacts recorded using articulating paper. As a secondary outcome, the subjective clinical assessment made using the two methods was compared between different observers.

METHODS

Twenty-eight records were analysed for this study. Digital scan and intraoral photos of the coloured marks impressed by articulating paper were taken at the same time point for every patient. Using a standardized occlusal template, two operators recorded the number of occlusal contacts for every tooth provided by the two techniques. Then, 11 clinicians analysed the collected records and answered questions about the quality of the occlusions observed.

RESULTS

The statistical analysis showed significant differences between the number of contacts recorded by digital scan and those recorded by the photographed articulation marks, except in the case of the upper central incisors and first premolars. The Kappa Fleiss showed slight and fair agreement between clinicians when judging the occlusions.

CONCLUSION

The occlusal contacts recorded using the intraoral scanner and those recorded with the articulating paper did not match, and overall the clinicians showed low agreement when rating the recorded data.

CLINICAL SIGNIFICANCE

Despite of the great clinical importance of occlusal contact there is a lack of a precise method for recording and collecting occlusal contacts.

Digital superimposition of scans for recording and transferring vertical relation from provisional restorations when rehabilitating worn-out dentition: A dental technique

Excessive wear of the natural dentition results in the loss of tooth anatomy and the vertical dimension of occlusion (VDO) which may necessitate full mouth rehabilitation. Successful full-mouth rehabilitation with increased VDO requires accurate recording and transfer of the newly raised VDO with provisional restorations. Conventional bite registration can incur errors during the recording and transfer of vertical dimensions. This article introduces a digital approach-the superimposition of scans using an intraoral scanner (IOS) to transfer VDO, occlusion, and aesthetic data from provisional restorations for designing and fabricating indirect restorations in the management of worn-out dentition.

CAD-CAM and analog occlusal splints comparison based on the amount of occlusal adjustments. 3D analysis of the volumetric changes: A pilot study

OBJECTIVE

To evaluate the volumetric changes on occlusal surface of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal devices fabricated following a fully digital workflow after occlusal adjustment, compared to those fabricated with an analog workflow.

MATERIALS AND METHODS

Eight participants were included in this clinical pilot study, receiving two different occlusal devices fabricated with two different workflows, fully analog and fully digital. Every occlusal device was scanned before and after the occlusal adjustments to compare the volumetric changes using a reverse engineering software program. Moreover, three independent evaluators assessed a semi-quantitative and qualitative comparison using visual analog scale and dichotomous evaluation. The Shapiro-Wilk test was performed to validate normal distribution assumption, and a dependent t-Student test for paired variables was used to determine statistically significant differences (p-value < 0.05).

RESULTS

The root mean square value was extracted from the 3-Dimensional (3D) analysis of the occlusal devices. The average values of the root mean square were higher for the analogic technique (0.23 ± 0.10 mm) than the digital technique (0.14 ± 0.07 mm) but the differences were not statistically significant (paired t-Student test; p = 0.106) between the two fabrication techniques. The semiquantitative visual analog scale values between the impression for the digital (5.08 ± 2.4 cm) and analog (3.80 ± 3.3 cm) technique were significant (p < 0.001), and statistically significant differences values were assessed for evaluator 3 compared to the other evaluators (p < 0.05). However, the three evaluators agreed on the qualitative dichotomous evaluation in 62% of the cases, and at least two evaluators agreed in 100% of the evaluations.

CONCLUSIONS

Occlusal devices fabricated following a fully digital workflow resulted in fewer occlusal adjustments, as they could be a valid alternative to those fabricated following an analog workflow.

CLINICAL SIGNIFICANCE

Fabricated occlusal devices following a fully digital workflow could have some advantages over analog workflow such reduce occlusal adjustments at delivery appointment, which can result in reduced chair time and therefore increased comfort for the patient and clinician.

Diagnostic Applications of Intraoral Scanners: A Systematic Review

In addition to their recognized value for obtaining 3D digital dental models, intraoral scanners (IOSs) have recently been proven to be promising tools for oral health diagnostics. In this work, the most recent literature on IOSs was reviewed with a focus on their applications as detection systems of oral cavity pathologies. Those applications of IOSs falling in the general area of detection systems for oral health diagnostics (e.g., caries, dental wear, periodontal diseases, oral cancer) were included, while excluding those works mainly focused on 3D dental model reconstruction for implantology, orthodontics, or prosthodontics. Three major scientific databases, namely Scopus, PubMed, and Web of Science, were searched and explored by three independent reviewers. The synthesis and analysis of the studies was carried out by considering the type and technical features of the IOS, the study objectives, and the specific diagnostic applications. From the synthesis of the twenty-five included studies, the main diagnostic fields where IOS technology applies were highlighted, ranging from the detection of tooth wear and caries to the diagnosis of plaques, periodontal defects, and other complications. This shows how additional diagnostic information can be obtained by combining the IOS technology with other radiographic techniques. Despite some promising results, the clinical evidence regarding the use of IOSs as oral health probes is still limited, and further efforts are needed to validate the diagnostic potential of IOSs over conventional tools.

Comparison of Virtual Intersection and Occlusal Contacts between Intraoral and Laboratory Scans: An In-Vivo Study

BACKGROUND

The inaccurate maxillomandibular relationship of virtual casts following alignment by the vestibular scan may result in intersection (intermesh penetration) between opposing dental arch surfaces. Intersection occurs at short interocclusal distances in the occlusal contact area (OCA) and may result in infra-occluded definitive restorations. The purpose of this clinical study was to compare initial (by the proprietary scanner software) and new alignments (by a standalone 3D software) of virtual casts regarding OCA and intersection failure. New alignments aimed to rectify intersections by refinement of occlusal contacts.

MATERIAL AND METHODS

The virtual casts of 30 patients following digital and conventional impression-taking were analyzed, which were acquired for single implant restoration in the posterior site. Digital impressions were performed by both IOS 1 (3M True Definition) and IOS 2 (TRIOS 3), either as complete- or partial-arch scans, respectively. Mounted gypsum casts were digitized as complete-arch by a laboratory scanner (LS) in enabled and disabled mode to avoid intersection [LS (+)/LS (-)]. All virtual casts were newly aligned by a 3D software. The difference of the OCA and the area of intersection were calculated for initial and new alignments, using interocclusal distance ranges of 0-100 μm, 0-10 μm or <0 μm (=intersection). The difference of the OCA was compared using a linear mixed model. The distribution of occlusal contact points per modality and alignment was assessed independently by three observers and estimated by inter- and intraclass correlation (ICC) coefficients.

RESULTS

Virtual casts following initial alignment demonstrated intersections irrespective of the modality. The mean area of the intersection was most for IOS 2 (79.23 mm2), followed by IOS 1 (48.28 mm2), LS (-) (2.77 mm2), and LS (+) (2.01 mm2) in partial-arch scans. Complete-arch scans demonstrated an area of intersection of 70.63 mm2 for IOS 1 followed by 65.52 mm2 (IOS 2), 6.13 mm2 [LS (-)] and 2.76 mm2 [LS (+)]. Newly aligned scans showed no intersections. The overall distribution of occlusal contact points demonstrated moderate reliability (ICC 0.63). Good reliability could be observed (ICC 0.9) for LS (-) scans.

CONCLUSIONS

Intersections in the area of occlusal contact points are a phenomenon restricted to virtual casts, which should be considered in CAD/CAM. Initial alignments of LS are less affected by this virtual phenomenon, and contact points may be more distinct according to their anatomic region compared to IOS. Furthermore, intersections can be rectified in a 3D software by adjustment of the maxillomandibular relationship.

Measurement of the morphological data of primary teeth in northwest China

OBJECTIVE

This study aims to digitally obtain the morphological data of children's primary teeth in northwest China and evaluate the reliability of digitally obtaining the anatomical morphological data of primary teeth.

METHODS

A total of 308 extracted primary teeth and cone-beam computed tomography (CBCT) images of 407 primary teeth were collected in northwest China. Electronic digital Vernier callipers (accuracy: 0.01 mm) were used to measure the mesiodistal and buccolingual diameters and crown length of the extracted primary teeth and calculate the crown area and crown index. Each sample was scanned with an intraoral scanner (Trios2 3shape, Denmark), and the resulting stl format files were imported into Geomagic Wrap 2015 to measure the axial and buccolingual diameters and crown length. The crown area and crown index were then calculated. After verifying the accuracy of the CBCT image measurement, the CBCT image data of 407 samples were measured in SmartV software using the "measure length" function by referring to the coronal, sagittal, and horizontal planes to adjust the position of the reference line.

RESULTS

Northern Chinese have larger primary teeth than other populations (Japanese, white American, African, Icelander, Spanish, and Dominican Mestizo) but smaller primary teeth than native Australians. Compared to Indian primary teeth, northwest Chinese's primary teeth have larger diameters on the central axis and smaller diameters on the buccolingual surface. Male teeth are usually larger than female teeth. Compared with the results of Wang Huiyun's study, the axial and buccolingual diameters and crown length of all native tooth types in this total sample were significantly smaller at the 0.1% level, and only the axial diameters of the upper first molar and lower second molar and the crown length of the lower lateral incisor were significantly smaller at the 1% level. The results of the intraclass correlation coefficient of 308 extracted primary teeth expressed an excellent degree of agreement between the callipers and intraoral scanner for the following: mesiodistal diameter (0.956-0.991), buccolingual diameter (0.963-0.989), crown length [0.864-0.992, except for the upper canine (0.690)], crown index (0.850-0.975), and crown area (0.946-0.993).

CONCLUSION

The digital measurements of the intraoral scanner and CBCT image are in good agreement with the manual measurement of the Vernier calliper. The difference between the anatomical morphology size of the primary teeth measured in this study and the results of different populations could be due to different genetic backgrounds and environmental factors.