Reliability and validity of intraoral and extraoral scanners

Effect of printing technology, layer height, and orientation on assessment of 3D-printed models

BACKGROUND

Three-dimensional (3D) printing technologies have become popular in orthodontics. The aim of this study is to determine the effect of printing technology, orientation, and layer height on the accuracy of 3D-printed dental models.

METHODS

The maxillary arch of a post-treatment patient was scanned and printed at different orientations (0°, 90°) and layer thicknesses (25 µm, 50 µm, 100 µm, and 175 µm) using two different printing technologies (digital light processing and stereolithography). The 120 models were digitally scanned, and their average deviation from the initial model was analyzed using 3D algorithm. A multivariable linear regression analysis was used to estimate the effect of all variables on the average deviation from the initial model for the common layer thicknesses (50/100 µm). Finally, one-way ANOVA and Tukey posthoc test was used to compare the stereolithography (SLA) 25 µm and digital light processing (DLP) 175 µm groups with the groups that showed the least average deviation in the former analysis.

RESULTS

The multivariable linear regression analysis showed that the DLP 50 µm (mean ± SD: -0.022 ± 0.012 mm) and 100 µm (mean ± SD: -0.02 ± 0.009 mm) horizontally printed models showed the least average deviation from the initial model. Finally, the DLP 175 µm horizontally printed models (mean ± SD: 0.015 ± 0.005 mm) and the SLA 25 µm horizontally (mean ± SD: 0.011 ± 0.005 mm) printed models were more accurate.

CONCLUSIONS

All the models showed dimensional accuracy within the reported clinically acceptable limits. The highest accuracy was observed with DLP printer, 175 µm layer thickness, and horizontal orientation followed by SLA printer, 25 µm layer thickness, and horizontal orientation.

Effect of finish line location and saliva contamination on the accuracy of crown finish line scanning

PURPOSE

Intraoral scanners are used widely as an alternative to conventional impressions, but studies on the influence of finish line location and saliva contamination on scanning trueness are lacking. The purpose of this in vitro study was to evaluate the influence of finish line location and saliva contamination on the scanning trueness of crown finish lines.

MATERIALS AND METHODS

Three ivorine teeth were prepared for all-ceramic crowns with finish lines placed equigingivally, 0.5 mm subgingivally, and 1.0 mm subgingivally. A single-cord technique was used for gingival retraction, and a total of 180 intraoral scans were made using two intraoral scanners (Emerald; Planmeca USA Inc., Hoffman Estates, IL, USA & Trios 3; 3Shape A/S, Copenhagen, Denmark). The prepared teeth were separated from the dentoform and scanned using the same intraoral scanners to create reference scans. All scans were imported to the design software (Dental System 2019; 3Shape A/S, Copenhagen, Denmark). After marking the finish lines of prepared teeth, intraoral scans were aligned to the reference scans for comparisons. Vertical and horizontal marginal discrepancies were measured at four different measuring points (buccal, lingual, mesial, and distal) and analyzed. Two-way ANOVA and Tukey HSD tests were used for statistical analysis (α = 0.05).

RESULTS

The average vertical and horizontal discrepancies from various groups ranged from -33 to 440 µm. For both intraoral scanners, subgingival finish line groups showed greater vertical and horizontal discrepancies compared with equigingival finish line groups. Saliva contamination significantly increased both vertical and horizontal discrepancies for all finish line locations. The discrepancy increases due to saliva contamination were greater for the subgingival groups.

CONCLUSIONS

Subgingival finish lines were not accurately captured using the intraoral scanners. The presence of saliva significantly reduced scanning trueness, and this was amplified when the finish lines were located subgingivally.

Accuracy of Intraoral Scanner for Recording Completely Edentulous Arches-A Systematic Review

Scanning edentulous arches during complete denture fabrication is a crucial step; however, the quality of the resulting digital scan is still questionable. The purpose of this study is to systematically review studies (both clinical and in vitro) and determine whether intraoral scanners have clinically acceptable accuracy when recording completely edentulous arches for the fabrication of removable complete dentures. An electronic search in medical databases like PubMed, Scopus, and Web of Science (WOS), using a combination of relevant keywords, retrieved 334 articles. After full-text evaluation, twelve articles fulfilled the inclusion criteria for this review (eight clinical studies and four in vitro studies). A quality analysis of the included studies was carried out using the QUADAS-2 tool. The accuracy values varied between different intraoral scanners. Different regions of the edentulous arches showed differences in trueness and precision values in both in vitro and clinical studies. Peripheral borders, the inner seal, and poorly traceable structures like the soft palate showed maximum discrepancies. The accuracy of intraoral scanners in recording clear anatomic landmarks like hard tissues with attached mucosa was comparable to conventional edentulous arch impressions. However, higher discrepancies were recorded when digitizing mobile and poorly traceable structures. Intraoral scanners can be used to digitize denture-bearing areas, but the interpretation of the peripheral border and the soft palate should be carefully carried out.

Accuracy of intraoral scanning versus conventional impressions for partial edentulous patients with maxillary defects

This study aimed to evaluate the accuracy of digital dental impressions obtained by intraoral scanning (IOS) for partial edentulous patients with maxillary defects by comparing them with conventional impression techniques. Ten subjects underwent an experimental procedure where three ceramic blocks were affixed to the healthy palate mucosa. Digital dental impressions were captured using IOS and subsequently imported into software. Conventional impressions obtained by silicone rubber were also taken and scanned. Linear distance and best-fit algorithm measurements were performed using conventional impression techniques as the reference. Twenty impressions were analyzed, which included 30 pairs of linear distances and 10 best-fit algorithm measurements. Regarding linear distance, paired two-sample t-test demonstrated no significant differences between IOS and model scanning in groups A and C, whereas significant differences were found in group B (P < 0.05). Additionally, ANOVA revealed significant differences among the groups (P < 0.05). No significant differences were found for the best-fit algorithm measurement of the dentition. IOS can provide accurate impressions for partial edentulous patients with maxillary defects and its accuracy was found to be comparable with conventional impression techniques. A functional impression may be needed to ensure accurate reproduction of soft and hard tissues in defect or flap areas.

Factors influencing the dimensional accuracy of additively manufactured dental models: A systematic review of in vitro studies

OBJECTIVES

This study aims to systematically review the literature and evaluate the effect of post-printing factors such as aging, heat, appliance fabrication and storage on the dimensional accuracy of full-arch dental models manufactured by additive manufacturing (AM) technology for the intended use of working model purposes.

MATERIALS AND METHODS

Three online databases, Medline (Ovid), Scopus and Web of Science were screened and last searched in March 2023. In-vitro studies and publications involving any distortions and shrinkage to the additively manufactured (AMed) model after printing and post-processing were included. However, literature reviews, abstracts, publications in a language different from English, or publications not testing a dental model with an arch or dentition were excluded. The references cited in the studies included were also checked via Google Scholar to identify relevant published studies potentially missed.

RESULTS

The systematic search identified and screened 769 different studies after the removal of duplicates. After applying inclusion and exclusion criteria, a total of 30 relevant titles and abstracts were found, yielding six final selections after full-text screening. Four out of the six studies evaluated the effect of both storage and aging on the dimensional accuracy of AMed dental models. The other two studies assessed the dimensional accuracy after the fabrication of thermoformed and vacuum-formed appliances on the AMed dental model.

CONCLUSIONS

AMed models can be utilised as working models on the condition that specific printing parameters are followed and additional model design features are employed. No definitive conclusions can be drawn on standardised methods to assess the dimensional accuracy of AMed dental models after storage, aging and appliance fabrication. In addition, there is no consensus on specific storage periods for an AMed model. Majority of study designs removed the palatal region to create a horseshoe shaped model, making the results less applicable to a working model scenario requiring the palate for retention purposes. The parameters investigated on AMed models include storage, aging, and appliance fabrication through thermoforming and vacuum-forming. Printing densities of solid models and wall thickness of hollow models were shown to influence the accuracy of AMed models. Dimensional accuracy of AMed models have been shown to be affected during appliance fabrication through thermoforming and vacuum-forming in certain conditions.

SIGNIFICANCE

There is a clear need of standardisation when manufacturing AMed dental models for working model purposes. The current methods investigated in this study lack established protocols to accurately manufacture the AMed models, and effectively store and utilise an AMed dental model for fabrication of orthodontic and prosthodontic appliances.

The precision of two alternative indirect workflows for digital model production: an illusion or a possibility?

OBJECTIVE

Despite the clear drive from both research and clinical dentistry toward digital transformation, there are limitations to implementing intra-oral scanning (IOS) into daily dental practice. This study aimed to compare the precision of digital models obtained from two alternative indirect workflows to direct IOS.

MATERIAL AND METHODS

Two indirect digital workflows were evaluated in this study. In the IOS group (direct), IOS directly obtained digital impressions of participants' upper and lower dental arches, while in the Scan Impression (Scan Imp) group (indirect), a desktop scanner scanned silicone-based impressions of upper and lower whole arches that were taken with plastic trays. In the cone-beam computed tomography impression (CBCT Imp) group (indirect), a CBCT machine scanned the silicone-based impressions. Then, the precision of the entire arch and individual teeth for all digital impressions was virtually quantified. Following superimposition, differences between standard tessellation language (STL) files obtained from both-direct and indirect-methods were evaluated by color-mapping and measuring the surface distance between superimposed STL files. Furthermore, 18 linear measurements were taken from each digital model. ANOVA with repeated measures, Pearson coefficient, and intraclass correlation coefficient were used for intergroup comparisons.

RESULTS

The digital models obtained from the two indirect workflows differed from the IOS in some dental and intra-arch measurements but were considered clinically acceptable. Ranked against IOS, CBCT Imp models had greater precision, followed by Scan Imp.

CONCLUSION

Digital models obtained from two indirect, alternative workflows, desktop, and CBCT scanning of impression, have clinically acceptable accuracy and reliability of tooth size and intra-arch measurements, providing the use of proper methodologies.

CLINICAL RELEVANCE

There are some limitations to implementing IOS in daily clinical practice. However, several alternative digital model production techniques might provide an affordable solution. Although they may insignificantly differ in accuracy, all can be applied clinically.

A simple method for quick evaluation of the anterior tooth ratio: an observational study

Background

An ideal relationship of anterior teeth is closely related to postoperative function, stability, and aesthetics. Therefore, it is necessary to estimate the proportion of anterior teeth when communicating with patients about possible treatment plans and outcomes. This study aimed to establish a simple method for assessing the proportion of anterior teeth and to identify the standard ratio value to provide references for clinical work.

Methods

Five hundred fourteen patients were divided into derivation, standard, and validation datasets. We first deduced our novel simplified anterior tooth ratio (SATR) by finding the key teeth with the derivation datasets, then established standard values by measuring the standard models, and finally validated the diagnostic performance of SATR. Independent sample t-test was used to select key teeth. Pearson’s correlation analysis and linear regression analysis was used to test and verify the correlation between SATR and the anterior Bolton ratio. Chi-square test and diagnostic test were used to verify the diagnostic results using SATR. P values of < 0.05 were considered statistically significant.

Results

Patients with an abnormal anterior Bolton ratio were more likely to have variations in the maxillary and mandibular lateral incisors. Therefore, the ratio of maxillary and mandibular lateral incisors was chosen as a simple way to assess the anterior tooth ratio and was defined as SATR (simplified anterior tooth ratio). A positive correlation was observed between SATR and anterior Bolton ratio (r = 0.702, p < 0.001), with the linear regression equation as follows: y = 0.503 + 0.328x, x = SATR, y = anterior Bolton ratio. The standard value of SATR was established (85.69% ± 3.57%) and proven reliable in clinical practice.

Conclusions

The ratio of maxillary and mandibular lateral incisors can be used to estimate the anterior tooth ratio, which showed high reliability and efficiency.

Fully Digital versus Conventional Workflows for Fabricating Posterior Three-Unit Implant-Supported Reconstructions: A Prospective Crossover Clinical Trial

This study assessed the clinical variables influencing the success of three-unit implant-supported fixed dental prostheses (ISFDPs) fabricated using either fully digital or conventional workflows. The clinical trial evaluated 10 patients requiring three-unit ISFDPs in the posterior mandible. Maxillomandibular relation records, and digital and conventional impressions were obtained from each patient using an intraoral scanner (IoS) and polyvinylsiloxane (PVS), and the frameworks were fabricated using zirconia and cobalt-chromium, respectively. A 2 µm accuracy scanner scanned the conventional master casts and standard reference models. The stereolithography (STL) files of the digital and conventional impressions were superimposed on the standard model file, and the accuracy was calculated with the best-fit algorithm. The framework adaptation and passivity were assessed using the one-screw and screw resistance tests. The time required for occlusal adjustment of both types of reconstructions, including the duration of the whole treatment, was recorded. The aesthetic appearance of ISFDPs was rated by each patient and clinician using a self-administered visual analogue scale questionnaire and the FDI World Dental Federation aesthetic parameters, respectively. The sample size was based on the power calculation, and alpha was set at 0.05 for the statistical analyses. The impression accuracy, framework adaptation and passivity, and reconstructions aesthetics did not significantly differ between the digital and conventional approaches. The total fabrication time was significantly shorter using the digital workflow. Within the limitations of this clinical study, the fully digital workflow can be used for the fabrication of ISFDPs with a clinical outcome comparable to that of the conventional workflow.

Agreement of the Discrepancy Index Obtained Using Digital and Manual Techniques—A Comparative Study

The discrepancy index evaluates the complexity of the initial orthodontic diagnosis. The objective is to compare whether there is a difference in the final discrepancy index score of the American Board of Orthodontics (ABO) when obtained using digital and manual techniques. Fifty-six initial orthodontic records in a digital and physical format were included (28 each) in 2022 at the Center for Research and Advanced Studies in Dentistry. For the digital measurements, iTero and TRIOS 3 intraoral scanners were used, along with Insignia software and cephalometric tracing with Dolphin Imaging software. Manual measurements were obtained in dental casts using the ruler indicated for the previously mentioned discrepancy index, in addition to conventional cephalometric tracing. Student’s t-test did not show statistically significant differences between the digital and manual techniques, with final discrepancy index scores of 24.61 (13.34) and 24.86 (14.14), respectively (p = 0.769). Cohen’s kappa index showed very good agreement between both categorical measurements (kappa value = 1.00, p = 0.001). The Bland–Altman method demonstrated a good agreement between continuous measurements obtained by both techniques with a bias of 0.2500 (superior limit of agreement =9.0092988, inferior limit of agreement = −8.5092988). Excellent agreement was observed in obtaining the discrepancy index through digital technique (Intraoral scanning and digital records) and manual technique (conventional records).

Accuracy between intraoral and extraoral scanning: Three-dimensional deviation and effect of distance between implants from two scanning methods

Aim

Evaluate the accuracy between the intraoral and extraoral scanning regarding the three dimensional (3D) deviation and distances between the implants, through 2 scanning methods.

Settings and Design

An in vitro study.

Materials and Methods

An edentulous mandibular model was used to install four implants and abutments, recommending 6 distances between the implants. Scans were performed using an intraoral (SI) and extraoral (SE) scanner for each studied group: Scanning with the scan bodies (SB) and device (SD) (n = 10). The files were imported into a surface evaluation program to assess 3D deviations and measure distances between implants.

Statistical Analysis

Precision was assessed as the difference between files (Kruskal-Wallis test), while trueness was assessed from the difference between scans, applying the Wilcoxon and Mann-Whitney test.

Results

As for the 3D deviations, SI showed accuracy, for the faces and positions of the implants in relation to the SE, in both scanning methods (P < 0.05). Regarding the capture of distances between implants, the SD scan obtained better trueness than the SB group (P < 0.05).

Conclusion

We concluded that the type and scanning methods used did not influence the 3D deviations, while for distances, scanning with the device had better trueness.

Case Study on the Diffusion of Digital Dental Technology Innovation–Double Diamond Model Perspective

This research employs a case study of a professional dental medical equipment company in Taiwan, cites the theoretical basis of innovation diffusion, and uses the design-thinking double-diamond model to review the company's history of promoting digital IOSs in the market from ground zero. Integrating the theoretical foundations of medical institution procurement and innovation diffusion, this study finds that different target customers have very different perceptions and acceptance of new technologies. The knowledge and attitude of medical personnel are the primary factor affecting new technology procurement, only then will decision-making factors such as financial, functional, and service aspects be further considered.

Accuracy of digital dental models and three-dimensional printed dental models in linear measurements and Bolton analysis

Background: Due to advances in digital technology, it is possible to obtain digital dental models through intraoral scanning. The stereolithographic data collected from the scanner can subsequently be printed into a three-dimensional dental model in resinic material. However, the accuracy between digital dental models and printed dental models needs to be evaluated since it might affect diagnosis and treatment planning in orthodontic treatment.

This study aimed to evaluate the accuracy of digital models scanned by a Trios intraoral scanner and three-dimensional dental models printed using a Formlabs 2 3D printer in linear measurements and Bolton analysis.

Methods: A total of 35 subjects were included in this study. All subjects were scanned using a Trios intraoral scanner to obtain digital study models. Stereolithographic data from previous scanning was printed using a Formlabs 2 3D printer to obtain printed study models. Mesiodistal, intercanine, intermolar, and Bolton analysis from all types of study models were measured. The intraclass correlation coefficient was used to assess intraobserver and interobserver reliability. All data were then statistically analyzed.

Results: The reliability tests were high for both intraobserver and interobserver reliability, which demonstrates high reproducibility for all measurements on all model types. Most of the data compared between study models showed no statistically significant differences, though some data differed significantly. However, the differences are considered clinically insignificant.

Conclusion: Digital dental models and three-dimensional printed dental models may be used interchangeably with plaster dental models for diagnostic and treatment planning purposes.

Keywords: Accuracy, 3D printing, digital dental model, printed dental model.

New Approach to Dental Morphometric Research Based on 3D Imaging Techniques

Recent progress in imaging and image processing techniques has provided for improvements in odontological research in a variety of aspects. Thus, the presented method has been developed precisely in order to assess metrically 3D reconstructions of teeth. Rapidly and accurately obtained data of a wide range and appropriate density are sufficient enough for morphometric studies rather than tooth size assessments which are inherent to conventional techniques. The main contributions providing for holistic and objective morphometric analysis of teeth are the following: (1) interpretation of basic dental morphological features; (2) automated of orientational coordinate system setup based on tooth surface analysis; (3) new tooth morphometric parameters which could not be obtained through application of conventional odontometric techniques; (4) methodological novelty for automated odontomorphometric analysis pipeline. Application of tomographic imaging, which has been used for obtaining 3D models, expands the proposed method potential further through providing detailed and comprehensive reconstructions of teeth. The current study was conducted on unique material from the archaeological site of Sunghir related to the Upper Palaeolithic period. Metric assessments of external and internal morphological layers of teeth were performed in common orientation and sectioning. The proposed technique allowed more profound analysis of Sunghirian teeth which date back to the times of modern human morphology formation.

3D Scanners in Orthodontics-Current Knowledge and Future Perspectives-A Systematic Review

Background: Nowadays the use of intraoral scanners has become a routine practice in orthodontics. It allows the introduction of many treatment innovations. One should consider to what extent intraoral scanners have influenced the everyday orthodontic practice and in what direction should the further research in this field be conducted. This study is aimed to systematically review and synthesize available controlled trials investigating the accuracy and efficacy of intraoral scanners for orthodontic purpose to provide clinically useful information and to direct further research in this field. Methods: A literature search of free text and MeSH terms was performed by using MedLine (PubMed), Scopus, Web of Science and Embase. The search engines were used to find studies on application of intraoral scanners in orthodontics (from 1950 to 30 September 2020). The following keywords were used: “intraoral scanners AND efficiency AND accuracy AND orthodontics”. Results: The number of potential identified articles was 71, including 61 from PubMed, two from Scopus, three from Web of Science and five from Embase. After removal of duplicates, 67 full-text articles were analyzed for inclusion criteria, 16 of them were selected and finally included in the qualitative synthesis. Conclusions: There are plenty of data available on accuracy and efficacy of different scanners. Scanners of the same generation from different manufacturers have almost identical accuracy. This is the reason why future similar research will not introduce much to the orthodontics. The challenge for the coming years is to find new applications of digital impressions in the orthodontic practice.

Accuracy of intraoral scan images in full arch with orthodontic brackets: a retrospective in vivo study

Objectives

The purpose of this retrospective study was to evaluate the accuracy of intraoral scan (IOS) images in the maxillary and mandibular arches with orthodontic brackets.

Material and methods

From digital impressions of 140 patients who underwent orthodontic treatment, consecutive IOS images were selected based on standardized inclusion criteria: Two pre-orthodontic IOS images (IOS1 and IOS2) of permanent dentition with fully erupted second molars and IOS images obtained immediately after orthodontic bracket bonding (IOSb). Superimpositions were performed to evaluate the reproducibility of repeated IOS images. Accuracy of IOSb images was analyzed by comparing the average surface errors between IOS1c and IOS2c images, which were IOS images cut based on the same region of the interest as between IOS1 and IOSb images.

Results

A total of 84 IOS images was analyzed. The average surface errors between IOS1 and IOS2 images were 57 ± 8 μm and 59 ± 14 μm in the maxillary and mandibular arch, respectively, and their reliability was almost perfect. The average errors between IOSb and IOS1c images exhibited an increase, which measured 97 ± 28 μm in the maxillary arch and 95 ± 29 μm in the mandibular arch. These surface deviations between IOSb and IOS1c images were significantly larger in each region as well as entire dentition (P < 0.001) compared to those between IOS1c and IOS2c images.

Conclusions

The average surface errors of the scans with brackets showed increased values compared with those without brackets. This suggests that orthodontic brackets could affect the trueness of intraoral scan images.

Clinical relevance

It is necessary for clinicians to consider the effect of brackets on digital impression when using IOS images in orthodontic patients.

Accuracy and Precision Evaluation of International Standard Spherical Model by Digital Dental Scanners

With the popularization of digital technology and the exposure of traditional technology's defects, computer-aided design and computer-aided manufacturing (CAD/CAM) has been widely used in the field of dentistry. And the accuracy of the scanning system determines the ultimate accuracy of the prosthesis, which is a very important part of CAD/CAM, so we decided to evaluate the accuracy of the intraoral and extraoral scanners. In this study, we selected the sphere model as the scanning object and obtained the final result through data analysis and 3D fitting. In terms of trueness and precision, the scanner of SHINING was significantly different from that of others; however, there was no significant difference between TRIOS and CEREC. SHINING showed the lowest level of accuracy, with CEREC slightly lower than TRIOS. The sphere model has also been proven to be scanned successfully.

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.

Effect of Magnet Position on Tipping and Bodily Tooth Movement in Magnetic Force-Driven Orthodontics

The goal of our study is to launch magnetic force-driven orthodontics. This continuous study investigated the influence of magnet position on tipping and bodily tooth movement, using 3D printing technology and digital analysis. Orthodontic typodont models (TMs) for space-closure were 3D printed to mimic maxillary central incisors. Nd-Fe-B magnets were placed in the middle third (Model-M), and the cervical third (Model-C), of the tooth. TMs, before and after movement, were digitally scanned and superimposed. The 3D digital coordinates (X, Y, and Z axes), and rotations (yaw, pitch, and roll) of the tooth crown and root, were calculated and compared between the two magnet position settings. Model-M showed higher rates of movement, but more rotation than Model-C (p < 0.01). The root apex of Model-M moved in the opposite direction of the crown (R = −0.29), indicating tipping movement. In contrast, the crown and root apex moved in the same direction (R = 0.56) in Model-C, indicating bodily movement. These patterns were confirmed in a typodont model of a moderate crowding case. The results validated that modifying the magnet position increased the amount of bodily tooth movement, and decreased rotation/tipping in an ex vivo setting.

Scanning accuracy of nondental structured light extraoral scanners compared with that of a dental-specific scanner

STATEMENT OF PROBLEM

Diagnostic stone casts can be digitized by using dental optical scanners based on structured light scanning technology. Nondental structured light scanning scanners could also be used; however, the accuracy of these nondental scanners remains unclear.

PURPOSE

The purpose of this in vitro study was to measure the scanning accuracy (trueness and precision) of 3 nondental extraoral structured light scanners.

MATERIAL AND METHODS

A representative maxillary diagnostic cast was obtained and digitized by using an extraoral dental scanner (Advaa Lab Scan; GC Europe), and a reference or control standard tessellation language file was obtained. Three nondental extraoral scanners were evaluated: groups ND-1 (Space Spider; Artec), ND-2 (Capture Mini; Geomagic), and ND-3 (DAVID SLS3; David). Ten digital scans per group were recorded at a constant room temperature (23 °C) by an experienced geodetic engineer following the manufacturer's recommendations. The control or reference file was used as a reference to measure the discrepancy between the digitized diagnostic cast and 3 different nondental scans by using an open-source software (CloudCompare v.2.6.1; CloudCompare) and the iterative closest point technique. The Shapiro-Wilk test revealed that the data were normally distributed. The data were analyzed by using 1-way ANOVA, followed by post hoc Bonferroni tests (α=.05).

RESULTS

Significant differences between the 3 experimental nondental scanners and the control or reference scan (P<.001) were found. The ND-2 group had the lowest absolute mean error (trueness) and standard deviation (precision) (39 ±139 μm), followed by the ND-3 group (125 ±113 μm) and the ND1 group (-397 ±25 μm). No statistically significant differences were found in the mean error between the ND-2 and ND-3 groups (P=.228).

CONCLUSIONS

Only 1 nondental extraoral scanner tested obtained trueness mean values similar to those of the reference dental scanner. In all groups, the precision mean values were higher than their trueness values, indicating low relative precision.

Comparison of Intraoral and Extraoral Digital Scanners: Evaluation of Surface Topography and Precision

The aim of this study was to evaluate the surface topography and the precision measurements of different intraoral and extraoral digital scanners. A reference model of a maxillary arch with four implant analogs was prepared and scanned by three intraoral and two extraoral scanners. The reference model was scanned fifteen times with each digital scanning system, investigating the surface topography and precision measurements for the same-arch and cross-arch measurements. The data was exported to 3D inspection and mesh-processing software (GOM Inspect, Braunschweig, Germany). Statistical analysis was performed using a one-way Analysis of Variance (ANOVA) with the Tukey method for pairwise comparisons. The effect of parameters on generating the surface topography was analyzed by Univariate Linear Regression Analysis. Of the scanner systems evaluated, iTero (IT) exhibited the most number of triangulation points, followed by Trios 3 Shape (TR) and Straumann Cares (SC). There were no significant differences observed in the surface topography when comparing flat and contoured surfaces, the anterior and posterior position, and interproximal areas. For the precision measurement in the same quadrant, no statistical difference was noted between intra- and extraoral scanners. However, the extraoral scanners showed substantially higher precision measurements for the cross-arch measurement. Surface topography did not correlate to precision. Rather, precision correlated with the scanning mechanism. For a quadrant scanning, both intraoral and extraoral scanners are recommended, but extraoral scanners are recommended for a full-arch scanning.

Comparison of the Accuracy of Three-Dimensional Printed Casts, Digital, and Conventional Casts: An In Vitro Study

Objectives  The integration of computer-aided design and manufacturing technologies in diagnosis, treatment planning, and fabrication of prosthetic restoration is changing the way in which prosthodontic treatment is provided to patients. The aim of this study was to compare the accuracy of three-dimensional (3D) printed casts produced from the intraoral scanner using stereolithographic (SLA) 3D printing technique, their digital replicas, and conventional stone casts.

Materials and Methods  In this in vitro study, a typodont of maxillary and mandibular arches with full dentate ivory teeth was used as a reference cast. The typodont was digitized using Trios 3Shape intraoral scanner to create digital casts. The digital files were converted into 3D printed physical casts using a prototyping machine that utilizes the stereolithography printing technology and photocurable polymer as printing material. Linear measurements (mesiodistal and occlusocervical) and interarch measurements (intercanine and intermolar) were made for digital and prototyped models and were compared with the original stone casts. The reference teeth were canines, first premolars and second premolars in the maxillary and mandibular arches on the right and left sides. The measurements on printed and conventional casts were done by digital caliper while on digital casts; Geomagic Qualify software was used.

Statistical Analysis  One-way analysis of variance (ANOVA) was used to compare measurements among groups.

Results  Digital casts showed significantly higher error than the other two groups in all linear and interarch measurements. The mean errors of the digital cast in occlusocervical (OC) and mesiodistal (MD) measurements (0.016 and 0.006, respectively) were higher compared with those in the other two groups (OC, 0.004 and 0.007 and MD, 0.003 and 0.005 [ p < 0.0001 and p = 0.02, respectively]). Also, digital mean error in intermolar width (IMW) and intercanine width (ICW) (0.142 and 0.113, respectively) were greater than the other two groups (IMW, 0.019 and 0.008 and ICW, 0.021 and 0.011 [ p < 0.0001]). However, the errors were within the acceptable clinical range.

Conclusion  The 3D printed casts may be considered as a substitute for stone casts with clinically acceptable accuracy that can be used in diagnosis, treatment planning, and fabrication of prosthetic restorations.

Comparison of accuracy of mesiodistal tooth measurements made in conventional study models and digital models obtained from intraoral scan and desktop scan of study models

OBJECTIVE

To compare the measured values obtained from the plaster model, digital models created by scanning the plaster models and direct intraoral scanning with the values obtained from direct intraoral measurements.

DESIGN

This was a prospective clinical study.

SETTING

The study was conducted in Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India.

PARTICIPANTS

Ten patients before the start of orthodontic treatment were selected for the study.

METHODS

A computer-aided design and manufacturing (CAD-CAM) system is an advanced technology that is being adopted in the field of orthodontics for diagnosis, treatment planning and documentation of patient records. Mesiodistal tooth width measurements of first premolars, canines, lateral incisors and central incisors, and transverse width measurement from mesial pit of right first premolar to mesial pit of left first premolar in both maxilla and mandible were obtained from direct intraoral measurement (gold standard), study model obtained from alginate impression, intraoral scanned image, and desktop scanned image of the study model. Descriptive statistics and ANOVA was performed to find the difference in mean among the groups.

RESULTS

A P value > 0.05 was obtained in ANOVA indicating that there is no statistically significant difference in the measurements obtained by either of the methods.

CONCLUSION

Conventional stone models and digital models obtained from intraoral scan and desktop scanning of plaster models are clinically reliable as the variations in measurements obtained from these methods were clinically negligible.

Accuracy of digital light processing printing of 3-dimensional dental models

INTRODUCTION

This study aimed to investigate whether a digital light processing (DLP) printer could perform efficiently and with adequate accuracy for clinical applications when used with different settings and variations in the orientation of models on the build plate.

METHODS

Digital impressions of the oral environment were collected from 15 patients. Subsequently, digital impressions were used to make 3-dimensional printed models using the DLP printing technique. Three variables of the printing technique were tested: placement on the build plate (middle vs corner), thickness in the z-axis (50 microns vs 100 microns), and hollow vs solid shell. After being printed with different printing techniques and orientations on the same printer, a total of 240 maxillary and mandibular arches were measured. These variables generated 8 printing combinations. Tooth and arch measurements on each model type were compared with each other. Intraobserver reliability of the repeated measurement error was assessed using intraclass correlation coefficient.

RESULTS

All mean differences among the printing variations were statistically insignificant. The Bland-Altman plots verified a high degree of agreement among all model sets and printing variations. In addition, the measurements were highly reproducible; this was demonstrated by the high intraclass correlation coefficient for all measurements recorded.

CONCLUSIONS

The DLP printer produced clinically acceptable models in all areas of the build plate, with hollow and solid model shells, and at its high-speed setting of 100 microns. The applications of the DLP printer tested should be a viable option for printing in a clinical environment at a high-speed setting while filling the build plate and printing with less resin.

Accuracy and reliability of the expected root position setup methodology to evaluate root position during orthodontic treatment

INTRODUCTION

Current methods to evaluate root position either are inaccurate (panoramic radiograph) or expose patients to relatively large amounts of radiation (cone-beam computed tomography [CBCT]). A method to evaluate root position by generating an expected root position (ERP) setup was recently reported but has not been validated. The purpose of this study was to quantitatively assess the accuracy and reliability of the ERP setup with adequate statistical power.

METHODS

This retrospective study included 15 subjects who had completed phase 2 orthodontic treatment. An ERP setup was generated for all patients after treatment. The ERP setup was compared with the posttreatment CBCT scan, which served as the control. The mesiodistal angulation and buccolingual inclination of all teeth in both the ERP setup and the posttreatment CBCT scan were measured and compared. Bland-Altman analysis was used to assess interoperator reliability, intraoperator reliability, and agreement between the ERP setup and the posttreatment CBCT scan.

RESULTS

Bland-Altman plots showed high interoperator and intraoperator reliabilities. These plots also showed strong agreement between the ERP setup and the posttreatment CBCT scan; 11.8% of teeth measured for mesiodistal angulation and 9.6% of teeth measured for buccolingual inclination were outside the ±2.5° range of clinical acceptability.

CONCLUSIONS

We validated that the method to generate an ERP setup to evaluate root position for posttreatment orthodontic assessment is accurate and reliable.

Conformity, reliability and validity of digital dental models created by clinical intraoral scanning and extraoral plaster model digitization workflows

BACKGROUND

In dentistry, digitization of dental arches with intraoral scanners could one day replace impressions and plaster model digitization processes, if accuracy is clinically sufficient. This study aimed to assess the reliability, validity and conformity of an intraoral scanning procedure (Lythos^©, Ormco) and of two extraoral digitization workflows via alginate impression and plaster model scanning with the D810^© (3shape) or the Atos II Triple Scan^© (GOM) under clinical conditions.

METHODS

In 20 subjects three consecutive intraoral scans, three alginate and one reference polyether impression were taken of both the upper and lower dental arch, respectively. The digital models created from the corresponding plaster models and the intraoral scans were superimposed with the polyether reference standard by both a global and a local best-fit algorithm. Reliability, validity and conformity of the three digital workflows were assessed via intraclass (ICC) and Lin's concordance correlation coefficients (CCC) as well as analyses according to Bland-Altman.

RESULTS

The digital models created from the intraoral scanning procedure were less in agreement with the polyether reference (validity) than those from the extraoral procedures with reduced conformity and reliability. Local numerical deviations from the reference standard were approximately twice as high compared to the extraoral procedures, which showed high conformity and were equivalent and clinically acceptable in terms of reliability and validity.

CONCLUSIONS

Although the intraoral scanning method with Lythos^© seems to have drawbacks in terms of reliability, validity and conformity to the indirect alginate methods, all procedures proved to be clinically equivalent for diagnostic purposes.

Accuracy of three-dimensional dental resin models created by fused deposition modeling, stereolithography, and Polyjet prototype technologies: A comparative study

OBJECTIVES

The aim of this study was to assess the dimensional accuracy of fused deposition modeling (FDM)-, Polyjet-, and stereolithography (SLA)-produced models by comparing them to traditional plaster casts.

MATERIALS AND METHODS

A total of 12 maxillary and mandibular posttreatment orthodontic plaster casts were selected from the archives of the Orthodontic Department at the Indiana University School of Dentistry. Plaster models were scanned, saved as stereolithography files, and printed as physical models using three different three-dimensional (3D) printers: Makerbot Replicator (FDM), 3D Systems SLA 6000 (SLA), and Objet Eden500V (Polyjet). A digital caliper was used to obtain measurements on the original plaster models as well as on the printed resin models.

RESULTS

Comparison between the 3D printed models and the plaster casts showed no statistically significant differences in most of the parameters. However, FDM was significantly higher on average than were plaster casts in maxillary left mixed plane (MxL-MP) and mandibular intermolar width (Md-IMW). Polyjet was significantly higher on average than were plaster casts in maxillary intercanine width (Mx-ICW), mandibular intercanine width (Md-ICW), and mandibular left mixed plane (MdL-MP). Polyjet was significantly lower on average than were plaster casts in maxillary right vertical plane (MxR-vertical), maxillary left vertical plane (MxL-vertical), mandibular right anteroposterior plane (MdR-AP), mandibular right vertical plane (MdR-vertical), and mandibular left vertical plane (MdL-vertical). SLA was significantly higher on average than were plaster casts in MxL-MP, Md-ICW, and overbite. SLA was significantly lower on average than were plaster casts in MdR-vertical and MdL-vertical.

CONCLUSIONS

Dental models reconstructed by FDM technology had the fewest dimensional measurement differences compared to plaster models.

Intraoral scanners in dentistry: a review of the current literature

BACKGROUND

Intraoral scanners (IOS) are devices for capturing direct optical impressions in dentistry. The purpose of this narrative review on the use of IOS was to: (1) identify the advantages/disadvantages of using optical impressions compared to conventional impressions; (2) investigate if optical impressions are as accurate as conventional impressions; (3) evaluate the differences between the IOS currently available commercially; (4) determine the current clinical applications/limitations in the use of IOS.

METHODS

Electronic database searches were performed using specific keywords and MeSH terms. The searches were confined to full-text articles written in English and published in peer-reviewed journals between January 2007 and June 2017.

RESULTS

One hundred thirty-two studies were included in the present review; among them, 20 were previous literature reviews, 78 were in vivo clinical studies (6 randomized controlled/crossover trials, 31 controlled/comparative studies; 24 cohort studies/case series; 17 case reports) and 34 were in vitro comparative studies.

CONCLUSIONS

Optical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and/or in case of bleeding, there is a learning curve, and there are purchasing and managing costs. The current IOS are sufficiently accurate for capturing impressions for fabricating a whole series of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses and obturators. The literature to date does not support the use of IOS in long-span restorations with natural teeth or implants. Finally, IOS can be integrated in implant dentistry for guided surgery and in orthodontics for fabricating aligners and custom-made devices.

Intraoral Scanner Technologies: A Review to Make a Successful Impression

To overcome difficulties associated with conventional techniques, impressions with IOS (intraoral scanner) and CAD/CAM (computer-aided design and manufacturing) technologies were developed for dental practice. The last decade has seen an increasing number of optical IOS devices, and these are based on different technologies; the choice of which may impact on clinical use. To allow informed choice before purchasing or renewing an IOS, this article summarizes first the technologies currently used (light projection, distance object determination, and reconstruction). In the second section, the clinical considerations of each strategy such as handling, learning curve, powdering, scanning paths, tracking, and mesh quality are discussed. The last section is dedicated to the accuracy of files and of the intermaxillary relationship registered with IOS as the rendering of files in the graphical user interface is often misleading. This overview leads to the conclusion that the current IOS is adapted for a common practice, although differences exist between the technologies employed. An important aspect highlighted in this review is the reduction in the volume of hardware which has led to an increase in the importance of software-based technologies.