Comparison of mechanical properties of 3-dimensional printed and thermoformed orthodontic aligners.

INTRODUCTION: Orthodontic treatment using clear aligners has experienced exponential growth since its introduction in the late 1990s. Three-dimensional (3D) printing has also grown in popularity among orthodontists, and companies have begun to produce resins to directly print clear aligners. This study aimed to examine the mechanical properties of commercially available thermoformed aligners and direct 3D-printed aligners under laboratory conditions and a simulated oral environment. METHODS: Samples were prepared (approximately 2.5 × 20 mm) from 2 thermoformed materials, EX30 and LD30 (Align Technology Inc, San Jose, Calif), as well as 2 direct 3D-printing resins, Material X (Envisiontec, Inc; Dearborn, Mich) and OD-Clear TF (3DResyns, Barcelona, Spain). Wet samples were subjected to phosphate-buffered saline at 37°C for 7 days, whereas dry samples were stored at 25°C. Tensile and stress relaxation tests were carried out on an RSA3 Dynamic Mechanical Analyzer (Texas Instruments, Dallas, Tex) and Instron Universal Testing System (Instron, Norwood, Mass) to calculate elastic modulus, ultimate tensile strength, and stress relaxation. RESULTS: The elastic modulus of dry and wet samples was 103.2 ± 17.3 MPa and 114.4 ± 17.9 MPa (EX30), 61.3 ± 9.18 MPa and 103.5 ± 11.4 MPa (LD30), 431.2 ± 16.0 MPa and 139.9 ± 34.6 MPa (Material X), and 38.4 ± 14.7 MPa and 38.3 ± 8.4 MPa (OD-Clear TF), respectively. The ultimate tensile strength of dry and wet samples was 64.41 ± 7.25 MPa and 61.43 ± 7.41MPa (EX30), 40.04 ± 5.00 MPa and 30.09 ± 1.50 MPa (LD30), 28.11 ± 3.75 MPa and 27.57 ± 4.09 MPa (Material X), and 9.34 ± 1.96 MPa and 8.27 ± 0.93 MPa (OD-Clear TF), respectively. Residual stress of wet samples at 2% strain for 2 hours was 59.99 ± 3.02% (EX30), 52.57 ± 12.28% (LD30), 6.98 ± 2.64% (Material X), and 4.39 ± 0.84% (OD-Clear TF). CONCLUSIONS: There was a significant difference in elastic modulus, ultimate tensile strength, and stress relaxation among the samples tested. Moisture, specifically a simulated oral environment, appears to have a greater effect on the mechanical properties of direct 3D-printed aligners when compared with thermoformed aligners. This is likely to impact the ability of 3D-printed aligners to generate and maintain adequate force levels for tooth movement.

Student learning of head and neck anatomy using cone beam computed tomography and immersive virtual reality.

OBJECTIVES: The purpose of this study was to evaluate the efficacy of student learning of anatomy and 3D imaging concepts using cone beam computed tomography (CBCT) and immersive virtual reality (VR) technology. METHODOLOGY: Ninety (n = 90) first year dental students with no previous experience in 3D imaging were recruited. All participants completed a 10-item, multiple-choice questionnaire (MCQ) and a pre-survey prior to the educational intervention. Following a brief video orientation on CBCT and anatomy, each participant underwent a one-on-one educational intervention using immersive VR with calibrated instructors to identify head and neck anatomic structures using a VR/CBCT educational tool. Immediately following the intervention, all participants completed a postsurvey, a second MCQ, NASA task load index and presence questionnaires. Participants completed a third MCQ 2 weeks following the intervention. Analysis of objective measures of performance on MCQ's (p < 0.05) and subjective data from the questionnaires was completed. RESULTS: The students doubled their mean test scores 2.45 ± 1.274 to 5.99 ± 1.576 on MCQ's immediately following the educational intervention (p < 0.05). The significant increase in the MCQ test scores was maintained after 2 weeks, 5.73 ± 1.721 (p < 0.05). There were no gender differences in student test performance. Students rated the immersive VR/CBCT educational intervention experience highly for control, sensory, and realism factors with minimal distraction and frustration factors. CONCLUSION: Results from this study show that immersive VR/CBCT educational intervention improved test performance and contributed to information recall in students. Further benefits reported by participants include the sense of presence and increased engagement using immersive VR.

Three-dimensional comparison of bone-borne and tooth-bone-borne maxillary expansion in young adults with maxillary skeletal deficiency.

OBJECTIVE: To compare the transverse dental and skeletal changes in patients treated with bone-anchored palatal expander (bone-borne, BB) compared to patients treated with tooth and bone-anchored palatal expanders (tooth-bone-borne, TBB) using cone-beam computer tomography (CBCT) and 3D image analysis. METHODS: The sample comprised 30 patients with transverse maxillary discrepancy treated with two different types of appliances: bone-borne (Group BB) and tooth-bone-borne (Group TBB) expanders. CBCT scans were acquired before (T1) and after completion of maxillary expansion (T2); the interval was 5.4 ± 3.4 and 6.2 ± 2.1 months between the T1 and the T2 scans of Group TBB (tooth-bone-borne) and Group BB (bone-borne), respectively. Transverse, anteroposterior and vertical linear and angular three-dimensional dentoskeletal changes were assessed after cranial base superimposition. RESULTS: Both groups displayed marked transverse skeletal expansion with a greater ratio of skeletal to dental changes. Greater changes at the nasal cavity, zygoma and orbital levels were found in Group BB. A relatively parallel sutural opening in an anterior-posterior direction was observed in Group TBB; however, the Group BB presented a somewhat triangular (V-shaped) opening of the suture that was wider anteriorly. Small downward-forward displacements were observed in both groups. Asymmetric expansion occurred in approximately 50% of the patients in both groups. CONCLUSION: Greater skeletal vs dental expansion ratio and expansion of the circummaxillary regions were found in Group BB, the group in which a bone-borne expander was used. Both groups presented skeletal and dental changes, with a similar amount of posterior palate expansion. Asymmetric expansion was observed in both groups.

Dental students' interest in orthodontic careers: do orthodontic-related experiences and faculty and practitioner role models matter?

OBJECTIVES: To assess the percentage of dental students interested in orthodontics and likely to apply to orthodontic residency programs, the role of orthodontic-related experiences, and of orthodontic faculty and practitioner role models for student career decision-making. MATERIALS AND METHODS: This study had a cross-sectional design. A total of 335 students from seven U.S. dental schools responded to an anonymous web-based survey. RESULTS: 35% were much/very much interested in becoming orthodontists and 26% were likely to apply for this specialty training. A total of 80.1% had orthodontic treatment, 58.7% knew an orthodontist in their community, 44% had shadowed an orthodontist, and 10.8% had worked in an orthodontic practice before dental school. Respondents evaluated orthodontic practitioners more positively than orthodontic faculty. They considered practitioners as more compassionate providers than faculty members (5-point scale with 5 = agree strongly: mean = 4.25 vs 3.83; P < .001), making more of a difference in their patients' lives (4.44 vs 4.05; P < .001), and as better role models (4.21 vs 3.94; P < .001) who encouraged students more to pursue orthodontics (4.03 vs 3.65; P < .001). Their interest in becoming an orthodontist and in applying for an orthodontic residency program correlated with educational experiences (r = 0.35; P < .001 / r = 0.34; P < .001) and positive impressions of orthodontic faculty (r = 0.23; P < .001 / r = 0.22; P < .001) and practicing orthodontists (r = 0.29; P < .001 / r = 0.27; P < .001). CONCLUSIONS: Better understanding of factors motivating dental students to pursue orthodontics is crucial. Orthodontic practitioners and faculty play an important role in this context.

Three-dimensional evaluation of skeletal and dental effects of treatment with maxillary skeletal expansion.

INTRODUCTION: The objective was to determine the skeletal and dental changes with microimplant assisted rapid palatal expansion (MARPE) appliances in growing (GR) and nongrowing (NG) patients using cone-beam computed tomography and 3-dimensional imaging analysis. METHODS: The sample consisted of 25 patients with transverse maxillary discrepancy treated with a maxillary skeletal expander, a type of MARPE appliance. Cone-beam computed tomography scans were taken before and after maxillary expansion; the interval was 6.0 ± 4.3 months. The sample was divided into GR and NG groups using cervical vertebral and midpalatal suture maturation. Linear and angular 3-dimensional dentoskeletal changes were assessed after cranial base superimposition. Groups were compared with independent-samples t test (P <0.05). RESULTS: Both groups displayed marked transverse changes with a similar ratio of skeletal to dental transverse changes and parallel sutural opening from the posterior nasal spine-anterior nasal spine; a similar amount of expansion occurred in the anterior and the posterior regions of the maxilla. The maxilla expanded skeletally without rotational displacements in both groups. The small downward-forward displacements were similar in both groups, except that the GR group had a significantly greater vertical displacement of the canines (GR, 1.7 ±1.0 mm; NG, 0.6 ± 0.8 mm; P = 0.02) and anterior nasal spine (GR, 1.1 ± 0.6 mm; NG, 0.5 ± 0.5 mm; P = 0.004). CONCLUSIONS: Treatment of patients with MARPE appliance is effective in GR and NG patients. Although greater skeletal and dental changes were observed in GR patients, a similar ratio of skeletal to dental transverse changes was observed in both groups.

The effectiveness of a 3D virtual tooth identification test as an assessment tool for a dental anatomy course.

INTRODUCTION: There has been a recent demand in dental education for distance learning and the use of virtual assessment tools that can leverage technology to potentially replace physical testing facilities. However, virtual tools that evaluate student learning should be validated prior to adoption. The aim of this study was to investigate the effectiveness, efficiency and user satisfaction of a 3D tooth identification test for a dental anatomy course that can be given remotely. MATERIALS AND METHODS: First-year dental students (n = 41) enrolled in a dental anatomy course took both traditional in-person practical and virtual 3D tooth identification tests consisting of 25 test items. The test scores, average test durations, faculty time commitment and user perception were collected and analysed. Pearson product-moment correlation coefficients (p < .05) were determined for the criterion measures including real tooth identification test scores, comprehensive written examination and overall grade for the course. RESULTS: The average number of correct answers for the real and 3D virtual tooth identification examination was 21.3 ± 2.65 and 20.7 ± 2.56, respectively. The average test duration for the real and 3D virtual tooth identification test was 25:00 and 21:16 min, respectively. There was a positive correlation (p < .05) of the 3D virtual tooth identification test with the real tooth identification test (0.368), comprehensive written examination (0.334) and the overall course grade (0.646). The total faculty time commitment for the real and 3D virtual tooth identification test was 96 and 65 min, respectively. The students cited difficulty in manipulating the 3D models. CONCLUSION: This study presents evidence that the 3D virtual tooth identification test can be used to assess dental students' understanding of dental anatomy effectively and efficiently.

Analyses of oligodontia phenotypes and genetic etiologies.

Oligodontia is the congenital absence of six or more teeth and comprises the more severe forms of tooth agenesis. Many genes have been implicated in the etiology of tooth agenesis, which is highly variable in its clinical presentation. The purpose of this study was to identify associations between genetic mutations and clinical features of oligodontia patients. An online systematic search of papers published from January 1992 to June 2021 identified 381 oligodontia cases meeting the eligibility criteria of causative gene mutation, phenotype description, and radiographic records. Additionally, ten families with oligodontia were recruited and their genetic etiologies were determined by whole-exome sequence analyses. We identified a novel mutation in WNT10A (c.99_105dup) and eight previously reported mutations in WNT10A (c.433 G > A; c.682 T > A; c.318 C > G; c.511.C > T; c.321 C > A), EDAR (c.581 C > T), and LRP6 (c.1003 C > T, c.2747 G > T). Collectively, 20 different causative genes were implicated among those 393 cases with oligodontia. For each causative gene, the mean number of missing teeth per case and the frequency of teeth missing at each position were calculated. Genotype-phenotype correlation analysis indicated that molars agenesis is more likely linked to PAX9 mutations, mandibular first premolar agenesis is least associated with PAX9 mutations. Mandibular incisors and maxillary lateral incisor agenesis are most closely linked to EDA mutations.

Comparisons of orthodontic residents' performance and attitudes using 2D, 3D, and virtual reality surgical simulation methods.

PURPOSE: Advances in virtual reality technology for surgical simulation methods may improve diagnosis and treatment planning of complex orthognathic surgery cases. The objectives were to assess orthodontic residents' performance and attitudes when treatment planning orthognathic surgery cases using two-dimensional (2D) digital, three-dimensional (3D) digital, and virtual reality (VR) surgical simulations. METHODS: The study had a mixed methods study design involving 20 graduate orthodontic residents. Their previous experiences, confidence, and competence with orthodontic diagnosis and surgical treatment planning were assessed with a baseline survey. Each resident completed 2D, 3D, and VR treatment planning and simulation tasks in a randomized order and recorded their diagnosis, objectives, treatment plan, and special surgical concerns for each case using a treatment planning worksheet. The worksheets were scored and quantitative data were analyzed. Attitudinal responses to the simulation experience were captured with a post-survey and interview. RESULTS: The number of total prescribed surgical movements was greater for 3D and VR simulation methods (p = 0.001). There were no differences in the overall total written treatment plan analysis score among the three surgical simulation tasks. Participants took longer to complete the VR and 3D tasks (p < 0.001) and asked more questions regarding manipulation (p < 0.001) and software features (p < 0.002) for higher fidelity tools. Analysis of qualitative feedback showed positive attitudes toward higher fidelity tools with regard to visualization, manipulation, and enjoyment of the task. CONCLUSIONS: The results demonstrate that simulation methods of increased fidelity (3D and VR) are appropriate alternatives to 2D conventional orthognathic surgical simulation methods when combined with traditional records. Qualitative feedback confirms residents' readiness to adopt VR simulation. However, comprehensive training is needed to increase familiarity and comfort with using the new technology.

Management of Two Cases of Supernumerary Teeth.

Supernumerary teeth are commonly observed as an isolated developmental anomaly. While the familial tendency of supernumerary teeth has been documented, its genetic causality has not yet been determined. The purpose of this paper was to presents two cases with supernumerary teeth and the process leading to the diagnosis and determination of their underlying conditions. Cases were evaluated and family histories reviewed. Genetic counseling was recommended for the probands and followed by genetic testing of selected family members. The proband of family one, who has multiple supernumerary teeth, was determined to have a RUNX2 missense mutation (c.379C>T, p. Pro127Ser) and diagnosed with cleidocranial dysplasia. The proband of family two, who has a premolar region supernumerary tooth, was reported to have no bone defects also presented with a RUNX2 missense mutation (c.1381G>C, p. Gly461Arg). When patients present with multiple supernumerary teeth, a recommendation and guidance to genetic counseling and testing may facilitate accurate diagnosis and management.

Three-dimensional comparison of the skeletal and dentoalveolar effects of the Herbst and Pendulum appliances followed by fixed appliances: A CBCT study.

OBJECTIVES: To compare three-dimensional (3D) skeletal and dentoalveolar effects of the Herbst and Pendulum appliances followed by fixed orthodontic treatment in growing patients. SETTING AND SAMPLE POPULATION: A sample of 35 adolescents with cone-beam computed tomography scans obtained prior to Herbst and Pendulum treatment (T1) and immediately after fixed appliance treatment (T2). MATERIALS AND METHODS: Patients with Class II malocclusion was assessed retrospectively and divided into two treatment groups: Herbst group (n = 17, age: 12.0 ± 1.6 years) and Pendulum group (n = 18, age: 12.1 ± 1.5 years), with a mean treatment duration of 2.8 ± 0.8 years and 2.5 ± 0.7 years, respectively. Reconstructions of the maxillomandibular and dentoalveolar regions and data in 3D were obtained relative to cranial base, maxillary and mandibular regional superimpositions. Treatment outcomes (T2-T1) were compared between both groups using t tests for independent samples (P<.05). RESULTS: Significant increase in mandibular length was observed in the Herbst group (7.3 ± 3.5 mm) relative to the Pendulum group (4.6 ± 4.5 mm). Inferior and anterior displacements of Pogonion were 2.2 mm and 1.6 mm greater in the Herbst group, respectively. The mesial displacement of the lower first molars was significantly greater in the Herbst group (1.9 mm). The upper first molars had contrasting results in sagittal displacement, with 0.6 ± 1.7 mm of distal displacement with the Pendulum and 1.4 ± 2.1 mm of mesial displacement with the Herbst. Lower incisor projection and proclination were similar between groups. CONCLUSIONS: The Herbst and Pendulum appliances followed by comprehensive orthodontic treatment effectively corrected Class II malocclusion in growing patients, but with differing skeletal and dentoalveolar effects.

Validity and User Experience in an Augmented Reality Virtual Tooth Identification Test.

By leveraging emerging technologies in augmented reality (AR) and virtual reality (VR), a Virtual Dental Library and AR virtual tooth identification test were developed at a U. S. dental school. The AR virtual tooth identification test is a vision- based AR application that uses three-dimensional models of extracted human teeth as test items. The aims of this study were to investigate the validity of the AR virtual tooth identification test and evaluate the users' experience with the virtual testing method. The AR virtual tooth identification test scores were compared with real tooth identification tests, scores on three quizzes, final exam, and final grade for the course to assess its validity. In addition, a survey was used to assess students' perceptions of the AR tool. In 2018, all 109 first-year dental students who had completed the dental anatomy course were invited to participate in the study. Of the 93 participants, 61 (56% of total students) were included in the correlation analysis (32 were excluded due to incomplete test answer sheets or missing criterion measures). All 93 could respond to the survey and provide comments. In the results, the AR virtual tooth identification test had a positive correlation with the real tooth identification test (r=0.410, p<0.01), a combined score of two real tooth identification tests (r=0.545, p<0.01), the final exam (r=0.489, p<0.01), and overall grade for the dental anatomy course (r=0.661, p<0.01). On the tests, the students had some difficulty in viewing and manipulating the images and experienced technical difficulties related to their smartphones, and their survey responses expressed little support for the AR tool. Nevertheless, this study demonstrated criterion validity of the AR virtual assessment tool for tooth identification.

Treatment effects of the Carriere® Motion 3D™ appliance for the correction of Class II malocclusion in adolescents.

OBJECTIVES: To determine the treatment effects produced in Class II patients by the Carriere® Motion 3D™ appliance (CMA) followed by full fixed appliances (FFA). MATERIALS AND METHODS: This retrospective study evaluated 34 adolescents at three time points: T1 (pretreatment), T2 (removal of CMA), and T3 (posttreatment). The comparison group comprised 22 untreated Class II subjects analyzed at T1 and T3. Serial cephalograms were traced and digitized, and 12 skeletal and 6 dentoalveolar measures were compared. RESULTS: Phase I with CMA lasted 5.2 ± 2.8 months; phase II with FFA lasted 13.0 ± 4.2 months. CMA treatment restricted the forward movement of the maxilla at point A. There was minimal effect on the sagittal position of the chin at pogonion. The Wits appraisal improved toward Class I by 2.1 mm during the CMA phase but not during FFA. Lower anterior facial height increased twice as much in the treatment group as in controls. A clockwise rotation (3.9°) of the functional occlusal plane in the treatment group occurred during phase I; a substantial rebound (-3.6°) occurred during phase II. Overjet and overbite improved during treatment, as did molar relationship; the lower incisors proclined (4.2°). CONCLUSIONS: The CMA appliance is an efficient and effective way of correcting Class II malocclusion. The changes were mainly dentoalveolar in nature, but some skeletal changes also occurred, particularly in the sagittal position of the maxilla and in the vertical dimension.

Mandatory Drug Testing of Dental Students: To Test or Not to Test: Viewpoint 1: Drug Testing of Dental Students Should Be Mandatory for the Benefit of Students, Institutions, Patients, and the Profession and Viewpoint 2: Mandatory Drug Testing of Dental Students Carries Costs and Risks for Institutions and Students and Has Unproven Benefits.

An educational institution's decision to test or not test its students for drug use is controversial and complex. Although negative consequences of substance use disorder are well known, the consumption of prohibited substances continues to increase in young adults. Given the awareness of increasing drug use on college campuses and the potential impact on future health care professionals, issues associated with mandatory drug testing of dental students warrant investigation. The purpose of this Point/Counterpoint article is to present opposing viewpoints on whether mandatory student drug testing (MSDT) should be implemented for dental students. Viewpoint 1 affirms that MSDT is legal, ensures public safety, is recognized as a need in health care education, promotes professional and ethical responsibility, and is cost-effective. Viewpoint 2 asserts that MSDT has not been proven to be an effective deterrent for student drug use and it poses risks and costs for both institutions and students, ranging from potential violation of students' civil liberties to the consequences of false positive tests. This article's presentation of the recent literature on both sides of this issue provides dental educators with pertinent information for considering implementation of MSDT in their institutions.

Superimposition of maxillary digital models using the palatal rugae: Does ageing affect the reliability?

OBJECTIVES: The aim of this study was to evaluate the reliability of 3-dimensional maxillary dental changes using two methods of digital model superimposition. SETTING AND SAMPLE POPULATION: The Department of Orthodontics of Bauru Dental School, University of São Paulo and University of Michigan Craniofacial Growth Center. Fifteen subjects with normal occlusion. MATERIAL & METHODS: The sample was composed of digital study models of 15 normal occlusion subjects taken at 13 (T1), 18 (T2) and 60 years of age (T3). Using the software SlicerCMF 3.1, superimposition (registration) was conducted using 9 landmarks placed on the incisive papilla, second and third palatal rugae and 10 mm distal to the third palatal rugae. Two registration methods were compared: landmarks (LA) and regions of interest (ROI). Three-dimensional changes of landmarks on the buccal cusp tip of posterior teeth bilaterally and the incisal edge of the right central incisor were measured by three examiners. Intraclass correlation coefficients and Bland-Altman method evaluated intra- and inter-examiner agreements. RESULTS: Good or excellent intra-examiner agreement was found for T1-T2 and T2-T3 measurements using both registration methods. Inter-examiner agreements were good to excellent for T1-T2 measurements and poor to fair for most T2-T3 measurements. Mean T1-T2 differences were less than 0.5 mm for most measurements. CONCLUSION: Maxillary digital dental models of patients with normal occlusion superimposed on palatal rugae showed an adequate reliability for a 5-year interval comparison using landmarks or regions of interest. Lower than acceptable reproducibility using both superimposition methods was found for a 40-year interval comparison.

Accuracy and reliability of mandibular digital model registration with use of the mucogingival junction as the reference.

OBJECTIVE: The aim of the study was to validate a method of mandibular digital model (DM) registration, acquired from an intraoral scanner, compared with high-resolution voxel-based cone beam computed tomography (CBCT) registration with use of the mucogingival junction as the reference. STUDY DESIGN: Pre- and post-treatment CBCT and DM images from 12 adults were randomly selected from an initial sample of 40 patients who had undergone orthodontic treatment. The DM registration was performed in 6 steps: (1) construction of 3-dimensional (3-D) volumetric label maps of CBCT scans, (2) voxel-based registration of CBCT scans, (3) prelabeling of CBCT images, (4) approximation and registration of DM models to the corresponding CBCT models, (5) mucogingival-junction registration of pretreatment and post-treatment DM images, and (6) measurements. The Mann-Whitney U test was used to calculate the significance of differences between the CBCT and DM registrations. The intraclass correlation coefficient (ICC) was performed to assess reproducibility of the registration method. RESULTS: When registered CBCT models and registered DM models were compared, no statistically significant differences in the measurements were found (right-left P = .267; anterior-posterior P = .238; superior-inferior P = .384; and 3-D P = .076). ICC showed excellent intra- and inter-rater correlation (ICC > 0.90). CONCLUSIONS: The method of DM registration of the mandible with use of the mucogingival junction as the reference is accurate, reliable, and reproducible.

Taurodontism, variations in tooth number, and misshapened crowns in Wnt10a null mice and human kindreds.

WNT10A is a signaling molecule involved in tooth development, and WNT10A defects are associated with tooth agenesis. We characterized Wnt10a null mice generated by the knockout mouse project (KOMP) and six families with WNT10A mutations, including a novel p.Arg104Cys defect, in the absence of EDA,EDAR, or EDARADD variations. Wnt10a null mice exhibited supernumerary mandibular fourth molars, and smaller molars with abnormal cusp patterning and root taurodontism. Wnt10a (-/-) incisors showed distinctive apical-lingual wedge-shaped defects. These findings spurred us to closely examine the dental phenotypes of our WNT10A families. WNT10A heterozygotes exhibited molar root taurodontism and mild tooth agenesis (with incomplete penetrance) in their permanent dentitions. Individuals with two defective WNT10A alleles showed severe tooth agenesis and had fewer cusps on their molars. The misshapened molar crowns and roots were consistent with the Wnt10a null phenotype and were not previously associated with WNT10A defects. The missing teeth contrasted with the presence of supplemental teeth in the Wnt10a null mice and demonstrated mammalian species differences in the roles of Wnt signaling in early tooth development. We conclude that molar crown and root dysmorphologies are caused by WNT10A defects and that the severity of the tooth agenesis correlates with the number of defective WNT10A alleles.