Comparison of 3-dimensional dental models from different sources: diagnostic accuracy and surface registration analysis

Comparison of the accuracy (trueness and precision) of virtual dentofacial patients digitized by three different methods based on 3D facial and dental images

STATEMENT OF PROBLEM

The accuracy of virtual dentofacial patients has been explored, but the accuracy of virtual patients established by using a straightforward and reliable method and the accuracy of different virtual patients are unclear.

PURPOSE

The purpose of this clinical study was to compare the accuracy of virtual dentofacial patients digitized by using registered-block impression, exposed anterior teeth, and cone beam computed tomography (CBCT) reconstruction methods based on 3-dimensional (3D) facial and dental images.

MATERIAL AND METHODS

From the 15 selected participants who needed CBCT scanning, 3 kinds of virtual dentofacial patients were established by using 3 registration methods based on digital dental casts: 3D facial images, CBCT data, and registered-block impression. Compared with actual measurement, 25 linear distances of all virtual dentofacial patients were selected and measured by using a software program, and 3 separate measurements were calculated by the same person. The 1-way analysis of variance (ANOVA) was used to compare the deviations among 3 kinds of virtual dentofacial patients (trueness) and the deviations within groups (precision). The 1-sample t test was used to compare the difference between the deviation and the ideal error of 0.00 (α=.05).

RESULTS

Compared with the actual measurement, the trueness of the average deviations for registered-block impression (1.02 ±1.24 mm) was better than that of exposed anterior teeth (2.35 ±1.71 mm) and CBCT reconstruction (2.86 ±1.61 mm). The precision of the average deviations for registered-block impression (1.29 ±1.43 mm) was better than that of exposed anterior teeth (2.00 ±1.72 mm) and CBCT reconstruction (2.12 ±1.94 mm). Significant differences in trueness and precision were found among the 3 groups of virtual dentofacial patients (P<.01). Significant differences among the deviations of all linear distances and the ideal error of 0.00 were observed for all groups of virtual dentofacial patients (P<.05).

CONCLUSIONS

The accuracy of registered-block impression was better than that of the exposed anterior teeth and CBCT reconstruction. The accuracy of exposed anterior teeth was lower than that of the other methods but could satisfy the requirements of clinical diagnostics and scientific methods. The accuracy of CBCT reconstruction was poor and could only be used for special situations that permitted low accuracy.

Comparison of 2 different wear protocols of vacuum-formed retainers with respect to the conventional parameters and 3-dimensional superimpositional analysis

INTRODUCTION

This study aimed to compare the effectiveness of 2 different wear protocols of vacuum-formed retainers (VFR) in terms of angular and linear displacement of teeth using 3-dimensional (3D) superimpositional analysis and conventional model parameters.

METHODS

The study was conducted on 2 groups, each consisting of 17 patients randomly assigned to the part-time group or full-time group of VFR wearing after a nonextraction treatment. While conventional model measurements were assessed on 3D dental casts, 3D tooth movements were evaluated by digitally superimposed scans of casts acquired at 4-time points (debonding and 1, 3, and 6 months after debonding). Regarding conventional parameters, the difference between time-dependent changes among the groups was tested using the nonparametric Brunner-Langer and parametric linear mixed models. Considering 3D measurements, comparisons of groups were made using the Student t tests.

RESULTS

There were no significant intergroup differences regarding conventional model parameters at any time (P >0.05). Significant intergroup differences were observed regarding angular and linear relapses in the labiolingual direction for maxillary and mandibular incisors, as well as the rotational relapses for maxillary left canine and mandibular right lateral incisor, which were greater in the part-time group in the first month and at the end of 6 months (P <0.05).

CONCLUSIONS

Conventional model parameters appear to play a debatable role in evaluating the effectiveness of a retainer wear regimen. Three-dimensional analysis of tooth movements revealed that part-time VFR wear was less effective in retaining labiolingual and rotational tooth movements for the first month after debonding.

Comparison of the dimensional and morphological accuracy of three-dimensional digital dental casts digitized using different methods

The purpose of this study was to compare the accuracy of digital dental casts from plaster cast scanning (PCS), impression scanning (IPS), intraoral scanning (IOS), and cone-beam computed tomography (CBCT) scanning (CCS) methods. The maxillary and mandibular dental casts of 15 patients who needed CBCT scans for oral examination or treatment were digitized via four methods. 12 linear distance measurements of all digital dental casts were selected and acquired with software and compared to those of the reference plaster cast to evaluate the dimensional accuracy. Three-dimensional deviation analysis of the IPS, IOS and CCS groups with respect to the reference PCS group was performed to evaluate the morphological accuracy. The discrepancy in linear distances between the digital dental casts and reference plaster casts was statistically significant (p < 0.01). The dimensional accuracies of the PCS (0.06 ± 0.12 mm) and IPS (0.03 ± 0.05 mm) casts were better than those of the IOS (0.37 ± 0.30 mm) and CCS (0.54 ± 0.40 mm) casts. The one-sample t test showed that there were statistically significant differences between the discrepancies in 8 of the linear distances for the PCS group and 9 of the linear distances for the IPS group between the digital dental casts and reference plaster casts, with an ideal error of 0.00 (p < 0.05). The sequence of morphological accuracy from good to poor was maxillary and mandibular IPS, mandibular IOS; maxillary IOS; and maxillary and mandibular CCS. The accuracy of the digital dental casts from the PCS and IPS methods was greater than that of IOS and CCS methods. Although accuracy of the digital dental cast from IOS was low, it satisfied the clinical requirements for fixed restorations in small units. The accuracy of the digital dental cast from CCS was poorest and could only be used for procedures with lower accuracy requirements.

Potentialities and limitations of computer-aided design and manufacturing technology in the nonextraction treatment of Class I malocclusion

INTRODUCTION

Computer-aided design and manufacturing (CAD-CAM) systems have assisted orthodontists to position brackets virtually. The purpose of this study was to evaluate if a CAD-CAM system could predict the orthodontic treatment outcome of patients with Angle Class I malocclusion with mild crowding or spacing and with no need for orthodontic extraction.

METHODS

Using the American Board of Orthodontics Cast-Radiograph Evaluation (ABO-CRE) and color map superimposition, the treated occlusion was compared with the virtual final occlusion of 24 young adults with Class I occlusion. Using eXceed software (eXceed, Witten, Germany), we created the final occlusion prediction for each patient (virtual set up group). A digital model of the final occlusion of each patient was created (treated occlusion group). ABO-CRE score was used to compare groups. In addition, a color map was created for all subjects to access the mean and range values between the virtual set up model and treated occlusion model of each patient. Random and systematic errors were calculated. In addition, chi-square and t test were used.

RESULTS

Comparisons between virtual set up occlusion and treated occlusion showed statistically significant differences in 3 out of 7 measurements: interproximal contact score was larger for treated than virtual occlusion (0.45 mm and 0.04 mm, respectively), and the treated occlusion showed larger values than the virtual occlusion for occlusal contacts (14.13 mm and 7.62 mm, respectively) and overjet (7.37 mm and 0.66 mm, respectively). Although the treated occlusion showed a larger score than the virtual occlusion (50.41 mm and 34.58 mm, respectively), there is no significant difference between both. Root angulation decreased (from 1.95 ± 1.29 to 0.65 ± 0.71) because of the treatment.

CONCLUSIONS

ABO-CRE overall score presents no difference between groups. In addition, CAD-CAM setup occlusion closely predicts the final teeth alignment and leveling with interarch relationships showing less ABO-CRE score deduction.

Impact of Matching Point Selections on Image Registration Accuracy between Optical Scan and Computed Tomography

The point-based surface registration method involves the manual selection process of paired matching points on the data of computed tomography and optical scan. The purpose of this study was to investigate the impact of selection error and distribution of fiducial points on the accuracy of image matching between 3-dimensional (3D) images in dental planning software programs. Computed tomography and optical scan images of a partial edentulous dental arch were obtained. Image registration of the optical scan image to computed tomography was performed using the point-based surface registration method in planning software programs under different conditions of 3 fiducial points: point selection error (0, 1, or 2 mm), point distribution (unilateral, bilateral), and planning software (Implant Studio, Blue Bio Plan) (n = 5 per condition, N = 60). The accuracy of image registration at each condition was evaluated by measuring linear discrepancies between matched images at X, Y, and Z axes. Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction, and 3-way analysis of variance were used to statistically analyse the measurement data (α = 0.05). No statistically significant difference was exhibited between the 0 and 1 mm point mismatch conditions in either unilateral or bilateral point distributions. The discrepancy values in the 2 mm mismatch condition were significantly different from the other mismatch conditions, especially in the unilateral point distribution (P < 0.05). Strong interactions among point selection error, distribution, and software programs on the image registration were found (P < 0.001). Minor matching point selection error did not influence the accuracy of point-based automatic image registration in the software programs. When the fiducial points are distributed unilaterally with large point selection error, the image matching accuracy could be decreased.

3-Dimensional prediction of pre-surgical decompensation after atypical extractions and soft tissue simulation for ortho-surgical management of skeletal Class III malocclusion: A case report

Three dimensional imaging systems whether in the form of digital models, facial scanning or dolphin software play an important role in proper diagnosis and treatment planning of the orthosurgical cases. This case report highlights importance of three-dimensional treatment planning in the ortho-surgical management of the patient with skeletal Class III malocclusion involving atypical extraction. On clinical examination, patient had concave profile, prominent chin, deficient midface, flat cheekbone contour and prominent nasal projection. He had Class III molar and canine relation bilaterally with missing 12 (previously extracted), negative overbite and overjet with discordant maxillomandibular midlines. After 3-dimensional digital model set-up for occlusion planning and dolphin simulation for soft tissue prediction, extraction of left maxillary lateral incisor was planned followed by maxillary advancement and mandibular setback surgery and finish the occlusion in Class II molar relationship. After the orthodontic and orthognathic surgical treatment, the skeletal and dental imbalance was corrected, and most of the treatment objectives were achieved and patient was extremely satisfied with his facial profile. The treatment results were stable at the 3 years follow-up.

Three-dimensional comparison of 2 digital models obtained from cone-beam computed tomographic scans of polyvinyl siloxane impressions and plaster models

Purpose

This study was performed to evaluate the dimensional accuracy of digital dental models constructed from cone-beam computed tomographic (CBCT) scans of polyvinyl siloxane (PVS) impressions and cast scan models.

Materials and Methods

A pair of PVS impressions was obtained from 20 subjects and scanned using CBCT (resolution, 0.1 mm). A cast scan model was constructed by scanning the gypsum model using a model scanner. After reconstruction of the digital models, the mesio-distal width of each tooth, inter-canine width, and inter-molar width were measured, and the Bolton ratios were calculated and compared. The 2 models were superimposed and the difference between the models was measured using 3-dimensional analysis.

Results

The range of mean error between the cast scan model and the CBCT scan model was −0.15 mm to 0.13 mm in the mesio-distal width of the teeth and 0.03 mm to 0.42 mm in the width analysis. The differences in the Bolton ratios between the cast scan models and CBCT scan models were 0.87 (anterior ratio) and 0.72 (overall ratio), with no significant difference (P>0.05). The mean maxillary and mandibular difference when the cast scan model and the CBCT scan model were superimposed was 53 µm.

Conclusion

There was no statistically significant difference in most of the measurements. The maximum tooth size difference was 0.15 mm, and the average difference in model overlap was 53 µm. Digital models produced by scanning impressions at a high resolution using CBCT can be used in clinical practice.

A review on multiplatform evaluations of semi-automatic open-source based image segmentation for cranio-maxillofacial surgery

BACKGROUND AND OBJECTIVES

Computer-assisted technologies, such as image-based segmentation, play an important role in the diagnosis and treatment support in cranio-maxillofacial surgery. However, although many segmentation software packages exist, their clinical in-house use is often challenging due to constrained technical, human or financial resources. Especially technological solutions or systematic evaluations of open-source based segmentation approaches are lacking. The aim of this contribution is to assess and review the segmentation quality and the potential clinical use of multiple commonly available and license-free segmentation methods on different medical platforms.

METHODS

In this contribution, the quality and accuracy of open-source segmentation methods was assessed on different platforms using patient-specific clinical CT-data and reviewed with the literature. The image-based segmentation algorithms GrowCut, Robust Statistics Segmenter, Region Growing 3D, Otsu & Picking, Canny Segmentation and Geodesic Segmenter were investigated in the mandible on the platforms 3D Slicer, MITK and MeVisLab. Comparisons were made between the segmentation algorithms and the ground truth segmentations of the same anatomy performed by two clinical experts (n = 20). Assessment parameters were the Dice Score Coefficient (DSC), the Hausdorff Distance (HD), and Pearsons correlation coefficient (r).

RESULTS

The segmentation accuracy was highest with the GrowCut (DSC 85.6%, HD 33.5 voxel) and the Canny (DSC 82.1%, HD 8.5 voxel) algorithm. Statistical differences between the assessment parameters were not significant (p < 0.05) and correlation coefficients were close to the value one (r > 0.94) for any of the comparison made between the segmentation methods and the ground truth schemes. Functionally stable and time-saving segmentations were observed.

CONCLUSION

High quality image-based semi-automatic segmentation was provided by the GrowCut and the Canny segmentation method. In the cranio-maxillofacial complex, these segmentation methods provide algorithmic alternatives for image-based segmentation in the clinical practice for e.g. surgical planning or visualization of treatment results and offer advantages through their open-source availability. This is the first systematic multi-platform comparison that evaluates multiple license-free, open-source segmentation methods based on clinical data for the improvement of algorithms and a potential clinical use in patient-individualized medicine. The results presented are reproducible by others and can be used for clinical and research purposes.

Comparison of reliability, validity, and accuracy of linear measurements made on pre- and posttreatment digital study models with conventional plaster study models

OBJECTIVES:

To compare the accuracy of the linear measurements made on pre- and posttreatment three-dimensional (3D) scanned digital models with conventional plaster study models.

MATERIALS AND METHODS:

The study was conducted on pre- and posttreatment study models of 132 patients. A 3D model scanner was used to scan the plaster models to form 3D digital models. The measurements were made on the plaster models using digital Vernier calipers, and the 3D digital models were assessed for similar measurement using a software of the model scanner. The intraclass correlation for intraoperator error showed good correlations between the measurements made on conventional plaster models and digital models.

RESULTS:

Although the comparison of the linear measurements made by conventional and digital methods on both pre- and posttreatment study models using intraclass coefficient showed a good correlation, analysis of variance showed significant mean differences in the measurements of multiple variables in both the groups. The number of variables showing significant differences was more in the pretreatment group. The measurements obtained by Vernier calipers were generally higher than those of scanned pre- and posttreatment study models.

CONCLUSION:

The linear measurements made by conventional and digital methods showed statistically significant mean differences. The accuracy of recording can be affected by the severity of pretreatment malocclusion, but the deviations were not large enough to contradict the use of the digital models for orthodontic records.

Comparison of automated grading of digital orthodontic models and hand grading of 3-dimensionally printed models

INTRODUCTION

Emerging workflows in orthodontics enable automated analysis of digital models and production of physical study models from digital files for the evaluation of treatment outcomes. The objective of this study was to compare the automated assessment of digital orthodontic models and the hand grading of 3D-printed models with the use of the American Board of Orthodontics cast-radiograph evaluation (ABO CRE) system.

METHODS

Plaster models from 15 cases were scanned with the use of a desktop model scanner to create digital models from which physical models were produced with the use of a stereolithography-based 3D printer. All digital models from each case were graded with the use of an automated software tool (SureSmile), and 3D-printed models were scored by hand with the use of the ABO CRE grading system. All hand-graded models were scored a second time at least 2 weeks later.

RESULTS

SureSmile gave statistically significantly higher scores to alignment and rotations (P < 0.001), overjet (P < 0.001), occlusal contacts (P < 0.001), and total score (P < 0.001). Hand grading scored higher in buccolingual inclination (P < 0.001). No significant differences were found in marginal ridges, occlusal relationships, and interproximal contacts.

CONCLUSIONS

Scores assessed in an automated manner by SureSmile are generally significantly greater than those assessed by hand grading.

Computed tomography data collection of the complete human mandible and valid clinical ground truth models

Image-based algorithmic software segmentation is an increasingly important topic in many medical fields. Algorithmic segmentation is used for medical three-dimensional visualization, diagnosis or treatment support, especially in complex medical cases. However, accessible medical databases are limited, and valid medical ground truth databases for the evaluation of algorithms are rare and usually comprise only a few images. Inaccuracy or invalidity of medical ground truth data and image-based artefacts also limit the creation of such databases, which is especially relevant for CT data sets of the maxillomandibular complex. This contribution provides a unique and accessible data set of the complete mandible, including 20 valid ground truth segmentation models originating from 10 CT scans from clinical practice without artefacts or faulty slices. From each CT scan, two 3D ground truth models were created by clinical experts through independent manual slice-by-slice segmentation, and the models were statistically compared to prove their validity. These data could be used to conduct serial image studies of the human mandible, evaluating segmentation algorithms and developing adequate image tools.

A novel method for superimposition and measurements on maxillary digital 3D models-studies on validity and reliability

Background

Serial 3D models can be used to analyze changes, but correct superimposition is crucial before measurements can be assessed. Earlier studies show that every palatal structure changes due to growth or treatment. Here, we describe a new method that uses an algorithm-based analysis to perform superimpositions and measurements in maxillary 3D models. This method can be used to identify deformations. In a second step, only unchanged areas are used for superimposition.

Objectives

This study investigates the validity and reliability of this novel method.

Methods

Digital 3D models from 16 cases were modified by an independent 3D engineer to simulate space closure and growth. True values for tooth movements were available as reference. Measurements and repeated measurements were performed by four observers.

Results

The total tooth movement had an absolute mean error of 0.0225 mm (SD 0.03). The intraclass correlation coefficient (ICC) was 0.9996. Rotational measurements had an absolute mean error of 0.0291 degrees (SD 0.04 degrees) and an ICC of 0.9999.

Limitations

Serial models need to be taken with a moderate interval (1 to 2 years). Obvious changed areas in the palate need to be cropped before processing the models.

Conclusion

The tested method is valid and reliable with excellent accuracy and precision even when changes through growth or orthodontic treatment occur.

Three-dimensional evaluation of mandibular anterior dental crowding in digital dental casts

Introduction:

Digital dental models provide a more accurate and comprehensive assessment of orthodontic cases. Although this technique is quite promising, there are few three-dimensional measurements methods described in the literature.

Objective:

The aim of this study was to propose a method for assessing the degree of mandibular anterior dental crowding in the three planes of space, using digital dental models.

Methods:

Thirty dental casts were selected and scanned by Maestro 3D Dental Scanner and imported by Geomagic Qualify 2013 software. The degree of crowding was calculated by two examiners, based on the Little's Irregularity Index, by means of the definition of axial, coronal and sagittal planes for each model. Intraexaminer analysis was performed with Dahlberg's Formula (DF) and Intraclass Correlation Coefficients (ICC), and interexaminer analysis was performed with ICC and paired t-test.

Results:

The ICC showed an excellent agreement (p < 0.05) for all measurements, except for the intraexaminer and interexaminer in the Z-axis, in which it was found a moderate agreement. The DF showed a satisfactory accuracy with all measurements showing less than 1 mm difference. The paired t-test showed statistical difference between the examiners in two measurements, although it was clinical irrelevant.

Conclusion:

When comparing the three planes of space, the Z-axis showed the greatest variation in landmarks placement; however, overall, the present method seems precise and reproducible.

Clinical evaluation of semi-automatic open-source algorithmic software segmentation of the mandibular bone: Practical feasibility and assessment of a new course of action

INTRODUCTION

Computer assisted technologies based on algorithmic software segmentation are an increasing topic of interest in complex surgical cases. However-due to functional instability, time consuming software processes, personnel resources or licensed-based financial costs many segmentation processes are often outsourced from clinical centers to third parties and the industry. Therefore, the aim of this trial was to assess the practical feasibility of an easy available, functional stable and licensed-free segmentation approach to be used in the clinical practice.

MATERIAL AND METHODS

In this retrospective, randomized, controlled trail the accuracy and accordance of the open-source based segmentation algorithm GrowCut was assessed through the comparison to the manually generated ground truth of the same anatomy using 10 CT lower jaw data-sets from the clinical routine. Assessment parameters were the segmentation time, the volume, the voxel number, the Dice Score and the Hausdorff distance.

RESULTS

Overall semi-automatic GrowCut segmentation times were about one minute. Mean Dice Score values of over 85% and Hausdorff Distances below 33.5 voxel could be achieved between the algorithmic GrowCut-based segmentations and the manual generated ground truth schemes. Statistical differences between the assessment parameters were not significant (p<0.05) and correlation coefficients were close to the value one (r > 0.94) for any of the comparison made between the two groups.

DISCUSSION

Complete functional stable and time saving segmentations with high accuracy and high positive correlation could be performed by the presented interactive open-source based approach. In the cranio-maxillofacial complex the used method could represent an algorithmic alternative for image-based segmentation in the clinical practice for e.g. surgical treatment planning or visualization of postoperative results and offers several advantages. Due to an open-source basis the used method could be further developed by other groups or specialists. Systematic comparisons to other segmentation approaches or with a greater data amount are areas of future works.

Dental measurements and Bolton index reliability and accuracy obtained from 2D digital, 3D segmented CBCT, and 3d intraoral laser scanner

Background

To compare the reliability and accuracy of direct and indirect dental measurements derived from two types of 3D virtual models: generated by intraoral laser scanning (ILS) and segmented cone beam computed tomography (CBCT), comparing these with a 2D digital model.

Material and Methods

One hundred patients were selected. All patients’ records included initial plaster models, an intraoral scan and a CBCT. Patients´ dental arches were scanned with the iTero® intraoral scanner while the CBCTs were segmented to create three-dimensional models. To obtain 2D digital models, plaster models were scanned using a conventional 2D scanner. When digital models had been obtained using these three methods, direct dental measurements were measured and indirect measurements were calculated. Differences between methods were assessed by means of paired t-tests and regression models. Intra and inter-observer error were analyzed using Dahlberg´s d and coefficients of variation.

Results

Intraobserver and interobserver error for the ILS model was less than 0.44 mm while for segmented CBCT models, the error was less than 0.97 mm. ILS models provided statistically and clinically acceptable accuracy for all dental measurements, while CBCT models showed a tendency to underestimate measurements in the lower arch, although within the limits of clinical acceptability.

Conclusions

ILS and CBCT segmented models are both reliable and accurate for dental measurements. Integration of ILS with CBCT scans would get dental and skeletal information altogether.

Key words:CBCT, intraoral laser scanner, 2D digital models, 3D models, dental measurements, reliability.

Accuracy and reproducibility of dental measurements on tomographic digital models: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review with meta-analysis was to assess the accuracy and reproducibility of dental measurements obtained from digital study models generated from CBCT compared with those acquired from plaster models.

METHODS

The electronic databases Cochrane Library, Medline (via PubMed), Scopus, VHL, Web of Science, and System for Information on Grey Literature in Europe were screened to identify articles from 1998 until February 2016. The inclusion criteria were: prospective and retrospective clinical trials in humans; validation and/or comparison articles of dental study models obtained from CBCT and plaster models; and articles that used dental linear measurements as an assessment tool. The methodological quality of the studies was carried out by Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. A meta-analysis was performed to validate all comparative measurements.

RESULTS

The databases search identified a total of 3160 items and 554 duplicates were excluded. After reading titles and abstracts, 12 articles were selected. Five articles were included after reading in full. The methodological quality obtained through QUADAS-2 was poor to moderate. In the meta-analysis, there were statistical differences between the mesiodistal widths of mandibular incisors, maxillary canines and premolars, and overall Bolton analysis. Therefore, the measurements considered accurate were maxillary and mandibular crowding, intermolar width and mesiodistal width of maxillary incisors, mandibular canines and premolars, in both arches for molars.

CONCLUSIONS

Digital models obtained from CBCT were not accurate for all measures assessed. The differences were clinically acceptable for all dental linear measurements, except for maxillary arch perimeter. Digital models are reproducible for all measurements when intraexaminer assessment is considered and need improvement in interexaminer evaluation.

The Accuracy and Reproducibility of Linear Measurements Made on CBCT-derived Digital Models

OBJECTIVE

To evaluate the accuracy and reproducibility of linear measurements made on cone-beam computed tomography (CBCT)-derived digital models.

MATERIALS AND METHODS

A total of 25 patients (44% female, 18.7 ± 4 years) who had CBCT images for diagnostic purposes were included. Plaster models were obtained and digital models were extracted from CBCT scans. Seven linear measurements from predetermined landmarks were measured and analyzed on plaster models and the corresponding digital models. The measurements included arch length and width at different sites. Paired t test and Bland-Altman analysis were used to evaluate the accuracy of measurements on digital models compared to the plaster models. Also, intraclass correlation coefficients (ICCs) were used to evaluate the reproducibility of the measurements in order to assess the intraobserver reliability.

RESULTS

The statistical analysis showed significant differences on 5 out of 14 variables, and the mean differences ranged from -0.48 to 0.51 mm. The Bland-Altman analysis revealed that the mean difference between variables was (0.14 ± 0.56) and (0.05 ± 0.96) mm and limits of agreement between the two methods ranged from -1.2 to 0.96 and from -1.8 to 1.9 mm in the maxilla and the mandible, respectively. The intraobserver reliability values were determined for all 14 variables of two types of models separately. The mean ICC value for the plaster models was 0.984 (0.924-0.999), while it was 0.946 for the CBCT models (range from 0.850 to 0.985).

CONCLUSION

Linear measurements obtained from the CBCT-derived models appeared to have a high level of accuracy and reproducibility.

Accuracy of Bolton analysis measured in laser scanned digital models compared with plaster models (gold standard) and cone-beam computer tomography images

OBJECTIVE

The aim of this study was to compare the accuracy of Bolton analysis obtained from digital models scanned with the Ortho Insight three-dimensional (3D) laser scanner system to those obtained from cone-beam computed tomography (CBCT) images and traditional plaster models.

METHODS

CBCT scans and plaster models were obtained from 50 patients. Plaster models were scanned using the Ortho Insight 3D laser scanner; Bolton ratios were calculated with its software. CBCT scans were imported and analyzed using AVIZO software. Plaster models were measured with a digital caliper. Data were analyzed with descriptive statistics and the intraclass correlation coefficient (ICC).

RESULTS

Anterior and overall Bolton ratios obtained by the three different modalities exhibited excellent agreement (> 0.970). The mean differences between the scanned digital models and physical models and between the CBCT images and scanned digital models for overall Bolton ratios were 0.41 ± 0.305% and 0.45 ± 0.456%, respectively; for anterior Bolton ratios, 0.59 ± 0.520% and 1.01 ± 0.780%, respectively. ICC results showed that intraexaminer error reliability was generally excellent (> 0.858 for all three diagnostic modalities), with < 1.45% discrepancy in the Bolton analysis.

CONCLUSIONS

Laser scanned digital models are highly accurate compared to physical models and CBCT scans for assessing the spatial relationships of dental arches for orthodontic diagnosis.

Reliability and validity of intraoral and extraoral scanners

Background

This study evaluated the reliability and validity of one extraoral [Ortho Insight 3D™ (Motionview Software, Hixson, TN/USA)] and two intraoral [ITero™ (Align Technologies, San Jose, CA/USA) and Lythos™ (Ormco Corp., Orange, CA/USA)] scanners.

Methods

Fifteen dry human mandibles were scanned twice with each of the scanners, and digital models were generated. Five measurements were made on the dry mandibles and on each of the generated models, including intermolar width, intercanine width, posterior arch length, premolar crown diameter, and canine height. Systematic and random errors were evaluated based on replicate analyses. Differences were assessed using paired Student’s t tests.

Results

Replicate analyses showed statistically significant systematic errors for only one measure (intermolar width measured from Ortho Insight 3D scans). Measurements taken from all three scanners were highly reliable, with intraclass correlations ranging from .926 to .999. Method errors were all less than 0.25 mm (averaged ≈0.12 mm). Posterior arch length and canine height were significantly smaller when measured on the Ortho Insight 3D scans than when measured on the dry mandibles and significantly smaller than when measured from the ITero and Lythos models.

Conclusions

While all three scanners produced reliable measures, Ortho Insight 3D systematically underestimated arch length and canine height.

Methodological accuracy of digital and manual model analysis in orthodontics - A retrospective clinical study

INTRODUCTION

Computer-based digital orthodontic models are available for clinicians, supplemented by dedicated software for performing required diagnostic measurements. The purpose of this study was to evaluate the accuracy of measurements made on three-dimensional digital models obtained with a CBCT-scanner (DigiModel™, OrthoProof(®), Nieuwegin, The Netherlands).

METHODS

66 orthodontic dental casts of primary and early mixed dentitions were selected. Three-dimensional images were obtained on this CBCT-scanner and analyzed by means of the DigiModel™ software. Measurements were made with a digital caliper directly on the conventional casts and also digitally on the virtual models. 6 anatomic dental points were identified, and a total of 11 measurements were taken from each cast, including midline deviation, overjet, overbite and arch widths. Conformity of digital and manual measurements as well as intra-, inter- and repeated-measurement-reliability were evaluated by Lin's Concordance Correlation Coefficient, ICC and a Bland-Altman-analysis.

RESULTS

The agreement and conformity of digital and manual measurements was substantial for all parameters evaluated. Intra-, inter- and repeated-measurement-reliability was excellent.

CONCLUSIONS

Measurements on digital models obtained by a CBCT scan of conventional casts (DigiModel™, OrthoProof(®)) are suited for reliable diagnostic measurements, which compare well to those obtained from plaster casts, the current gold standard.

Intra-arch dimensional measurement validity of laser-scanned digital dental models compared with the original plaster models: a systematic review

A systematic review was undertaken to evaluate the validity of intra-arch dimensional measurements made from laser-scanned digital dental models in comparison with measurements directly obtained from the original plaster casts (gold standard). Finally included articles were only those reporting studies that compared measurements from digital models produced from laser scanning against their plaster models. Measurements from the original plaster models should have been made using a manual or digital caliper (gold standard). Articles that used scans from impressions or digital photographs were discarded. Detailed individual search strategies for Cochrane, EMBASE, MEDLINE, PubMed, and LILACS were developed. The references cited in the selected articles were also checked for any references that could have been missed in the electronic database searches. A partial gray literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item quality assessment tool for diagnostic accuracy studies (QUADAS). Only 16 studies were finally included for the qualitative/quantitative synthesis. The selected studies consistently agree that the validity of measurements obtained after using a laser scanner from plaster models is similar to direct measurements. Any stated differences would be unlikely clinically relevant. There is consistent scientific evidence to support the validity of measurements from digital dental models in comparison with intra-arch dimensional measurements directly obtained from them.

Reliability of linear and angular dental measurements with the OrthoMechanics Sequential Analyzer

INTRODUCTION

The aim of this study was to evaluate the reliability of newly developed software in the assessment of orthodontic tooth movement 3 dimensionally.

METHODS

The sample consisted of pretreatment and posttreatment computed tomography scans and plaster dental models of 20 orthodontic patients treated with a hyrax palatal expander as a part of their comprehensive orthodontic treatment. Dental-arch measurements, including arch widths, tooth inclinations, and angulation parameters, were measured on the scans using InvivoDental 3D imaging software (version 5.1; Motionview, Hixson, Tenn). The plaster dental models were laser scanned and superimposed, and measurements were obtained digitally using the new software. Agreement between the digital models and the computed tomography measurements was evaluated with intraclass correlation coefficients, paired t tests, and Bland-Altman plots. A P value of ≤0.05 was considered statistically significant.

RESULTS

High agreement, a nonsignificant paired t test, and no indication of agreement discrepancies were observed for most of the measured parameters.

CONCLUSIONS

The results confirmed that the new software program offers a reliable tool for dental-arch measurements obtained from 3-dimensional laser-scanned models.