Temporomandibular joint segmentation in MRI images using deep learning.

OBJECTIVES: Temporomandibular joint (TMJ) internal derangements (ID) represent the most prevalent temporomandibular joint disorder (TMD) in the population and its diagnosis typically relies on magnetic resonance imaging (MRI). TMJ articular discs in MRIs usually suffer from low resolution and contrast, and it is difficult to identify them. In this study, we applied two convolutional neural networks (CNN) to delineate mandibular condyle, articular eminence, and TMJ disc in MRI images. METHODS: The models were trained on MRI images from 100 patients and validated on images from 40 patients using 2D slices and 3D volume as input, respectively. Data augmentation and five-fold cross-validation scheme were applied to further regularize the models. The accuracy of the models was then compared with four raters having different expertise in reading TMJ-MRI images to evaluate the performance of the models. RESULTS: Both models performed well in segmenting the three anatomical structures. A Dice coefficient of about 0.7 for the articular disc, more than 0.9 for the mandibular condyle, and Hausdorff distance of about 2mm for the articular eminence were achieved in both models. The models reached near-expert performance for the segmentation of TMJ articular disc and performed close to the expert in the segmentation of mandibular condyle and articular eminence. They also surpassed non-experts in segmenting the three anatomical structures. CONCLUSION: This study demonstrated that CNN-based segmentation models can be a reliable tool to assist clinicians identifying key anatomy on TMJ-MRIs. The approach also paves the way for automatic diagnosis of TMD. CLINICAL SIGNIFICANCE: Accurately locating the articular disc is the hardest and most crucial step in the interpretation of TMJ-MRIs and consequently in the diagnosis of TMJ-ID. Automated software that assists in locating the articular disc and its surrounding structures would improve the reliability of TMJ-MRI interpretation, save time and assist in reader training. It will also serve as a foundation for additional automated analysis of pathology in TMJ structures to aid in TMD diagnosis.

MRI alone versus MRI-CBCT registered images to evaluate temporomandibular joint internal derangement.

OBJECTIVE: To evaluate the effect of magnetic resonance imaging-cone beam computed tomography (MRI-CBCT) image registration on inter- and intraexaminer consistency when evaluating temporomandibular joint (TMJ) internal derangement compared to MRI alone. METHODS: MRI and CBCT images of 25 patients (50 TMJs) were obtained and coregistered using mutual-information rigid image registration via Mirada XD software. Two experienced radiologists independently and blindly evaluated two types of images (MRI alone and MRI-CBCT registered images) at two different times (T1 and T2) for TMJ internal derangement, based on sagittal and coronal articular disc position in relation to the head of the condyle and the posterior slope of the articular eminence. RESULTS: The intraexaminer consistency with MRI alone (examiner 1 = 0.85 [0.74-0.92]; examiner 2 = 0.91 [0.84-0.95]) was lower than for the MRI-CBCT registered images (examiner 1 = 0.95 [0.91-0.97]; examiner 2 = 0.97 [0.96-0.99]). The interexaminer consistency of evaluating internal derangement with MRI alone (0.52 [0.18-0.73] at T1; 0.71 [0.45-0.84] at T2) was lower than for the MRI-CBCT registered images (0.97 [0.95-0.98] at T1; 0.98 [0.96-0.99] at T2). When disc position classification was dichotomized to normal versus anteriorly displaced, intraexaminer agreement for the two examiners was 0.52 and 0.63 for MRI alone, but was 0.91 and 0.92 for MRI-CBCT registered images. Interexaminer agreement for MRI alone was 0.29 at T1 and 0.42 at T2, but was 0.96 at both examination times for MRI-CBCT registered images. CONCLUSION: The MRI-CBCT registered images improved intra- and interexaminer consistency in the evaluation of internal derangement of TMJ.

Dental and skeletal changes in mild to moderate Class II malocclusions treated by either a Twin-block or Xbow appliance followed by full fixed orthodontic treatment.

OBJECTIVE: To compare the short-term skeletal and dental effects of two-phase orthodontic treatment including either a Twin-block or an XBow appliance. MATERIALS AND METHODS: This was a retrospective clinical trial of 50 consecutive Class II cases treated in a private practice with either a Twin-block (25) or XBow (25) appliance followed by full fixed orthodontic treatment. To factor out growth, an untreated Class II control group (25) was considered. RESULTS: A MANOVA of treatment/observation changes followed by univariate pairwise comparisons showed that the maxilla moved forward less in the treatment groups than in the control group. As for mandibular changes, the corpus length increase was larger in the Twin-block group by 3.9 mm. Dentally, mesial movement of mandibular molars was greater in both treatment groups. Although no distalization of maxillary molars was found in either treatment group, restriction of mesial movement of these teeth was seen in both treatment groups. Both treatment groups demonstrated increased mandibular incisor proclination with larger increases for the XBow group by 3.3°. The Wits value was decreased by 1.6 mm more in the Twin-block group. No sex-related differences were observed. CONCLUSIONS: Class II correction using an XBow or Twin-block followed by fixed appliances occurs through a relatively similar combination of dental and skeletal effects. An increase in mandibular incisor inclination for the XBow group and an increased corpus length for the Twin-block group were notable exceptions. No overall treatment length differences were seen.

Dental and skeletal changes in mild to moderate Class II malocclusions treated by either a Twin-block or Xbow appliance followed by full fixed orthodontic treatment.

OBJECTIVE: To compare the short-term skeletal and dental effects of two-phase orthodontic treatment including either a Twin-block or an XBow appliance. MATERIALS AND METHODS: This was a retrospective clinical trial of 50 consecutive Class II cases treated in a private practice with either a Twin-block (25) or XBow (25) appliance followed by full fixed orthodontic treatment. To factor out growth, an untreated Class II control group (25) was considered. RESULTS: A MANOVA of treatment/observation changes followed by univariate pairwise comparisons showed that the maxilla moved forward less in the treatment groups than in the control group. As for mandibular changes, the corpus length increase was larger in the Twin-block group by 3.9 mm. Dentally, mesial movement of mandibular molars was greater in both treatment groups. Although no distalization of maxillary molars was found in either treatment group, restriction of mesial movement of these teeth was seen in both treatment groups. Both treatment groups demonstrated increased mandibular incisor proclination with larger increases for the XBow group by 3.3°. The Wits value was decreased by 1.6 mm more in the Twin-block group. No sex-related differences were observed. CONCLUSIONS: Class II correction using an XBow or Twin-block followed by fixed appliances occurs through a relatively similar combination of dental and skeletal effects. An increase in mandibular incisor inclination for the XBow group and an increased corpus length for the Twin-block group were notable exceptions. No overall treatment length differences were seen.

Short-term treatment effects produced by the Twin-block appliance: a systematic review and meta-analysis.

OBJECTIVE: To evaluate dental, skeletal, and soft tissue effects during Twin-block treatment. METHODS: A systematic search of several electronic databases (Medline, PubMed, Embase, all EBM reviews, and Web of Science) was conducted until July 2013, as well as a limited grey-literature search (Google Scholar). Human cephalometric studies that used a Twin-block appliance in a non-extraction and non-surgical approach were selected. A comparable control group of untreated subjects was required. Two authors independently reviewed and extracted data from the selected studies. Risk of bias was assessed. The type of meta-analysis was selected based on heterogeneity. RESULTS: Ultimately 10 articles were included. Proclination of lower incisors, retroclination of upper incisors, distal movement of upper molars and/or mesial movement of lower molars, increase in mandibular length, and/or forward movement of the mandible were consistently reported. Clinically significant restraint of maxillary growth was not found. Although the mandibular body length is increased, the facial impact of it is reduced by the simultaneous increment of the face height. Changes of lower face height and occlusal plane inclination varied, suggesting that vertical dimension can be manipulated in patients who would benefit from lower molar extrusion. As for lip position, there is not enough evidence to suggest clear lip position changes. CONCLUSIONS: Changes associated with a Class II correction were identified. Most of the changes individually were of limited clinical significance, but when combined reached clinical importance. No long-term changes were available.

Changes in temporomandibular joint sagittal disc position over time in adolescents: a longitudinal retrospective study.

INTRODUCTION: Temporomandibular joint (TMJ) disc displacement (DD) is a common finding in preorthodontic adolescents. The natural progression of this disorder has not been described with magnetic resonance imaging. METHODS: The TMJs of a longitudinal sample of 94 preorthodontic adolescents were evaluated with magnetic resonance imaging to quantify sagittal disc position (SDP). The average time between imaging visits (V1 and V2) was 3.7 years (range, 1-6 years). Boys and girls had significantly different SDP values at V1, and therefore changes in SDP from V1 to V2 were analyzed separately for each sex. RESULTS: The highest standard deviation was 0.58 mm for intraobserver measurement error. Regression analysis identified no significant association between change in disc status and time between imaging. There was no significant difference in mean change in SDP in girls or the right TMJ in boys. The boys' left TMJ showed a significant mean increase (0.87 mm of anterior displacement). Approximately 10% of right TMJs and 15% of left TMJs had more than 2 mm of anterior DD during the study. In the girls, approximately 8% of the right TMJs and 3% of the left TMJs showed more than 2 mm of posterior disc position changes from V1 to V2. CONCLUSIONS: A natural progression in severity of DD in adolescents was not identified. Some subjects had large increases in anterior DD.

Longitudinal study of temporomandibular joint disc status and craniofacial growth.

INTRODUCTION: The objective of this retrospective cohort study was to assess the association of temporomandibular joint (TMJ) disc status and craniofacial growth. METHODS: Seventy-nine subjects (52 female, 27 male) with and without TMJ disc abnormalities were followed for a mean time of 3 years 8 months. Of this sample, 40 subjects (21 female, 19 male) received orthodontic treatment. Disc displacement and disc length measurements from magnetic resonance imaging of the jaw joints were used to evaluate TMJ disc status. A principal component analysis was used to produce a single disc status score per subject. Horizontal and vertical growth changes were obtained from cephalometric radiographs. The Fishman skeletal maturation index system was used to obtain the percentage of the total craniofacial growth attained. In addition, previous orthodontic treatment and time frames between the follow-up cephalometric radiographs were considered. RESULTS: A stepwise multiple linear regression analysis was used to evaluate the influence of TMJ disc status and orthodontic treatment on the displacement vectors between initial records (T1) and final records (T2) for each cephalometric point. Less horizontal and vertical growth was found in specific regions of the maxilla and the mandible in subjects with TMJ disc abnormalities, although their respective determination coefficients were mild (R2 <11.2%). CONCLUSIONS: TMJ disc abnormality was associated with reduced forward growth of the maxillary and mandibular bodies. TMJ disc abnormality was associated with reduced downward growth of the mandibular ramus.

Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements.

INTRODUCTION: The objective of this validation study was to compare standard plaster models (the current gold standard for cast measurements) with their digital counterparts made with emodel software (version 6.0, GeoDigm, Chanhassen, Minn) for the analysis of tooth sizes and occlusal relationships--specifically the Bolton analysis and the peer assessment rating (PAR) index and their components. METHODS: Dental casts were poured from 24 subjects with 8 malocclusion types grouped according to American Board of Orthodontics categories. Measurements were made with a digital caliper to the nearest 0.01 mm from plaster models and with the software from the digital models. A paired samples t test was used to compare reliability and validity of measurements between plaster and digital methods. RESULTS: Reproducibility of digital models via the concordance correlation coefficient was excellent in most cases and good in some. Although statistically significant differences in some measurements were found for the reliability and validity of the digital models via the average mean of the absolute differences of repeated measurements, none was clinically significant. Grouping of the measurements according to the 8 American Board of Orthodontics categories produced no significant difference (Kruskal-Wallis test). No measurement associated with Bolton analysis or PAR index made on plaster vs digital models showed a clinically significant difference. The PAR analysis and its constituent measurements were not significantly different clinically between plaster and emodel media. CONCLUSIONS: Preliminary results did not indicate that digital models would cause an orthodontist to make a different diagnosis of malocclusion compared with plaster models; digital models are not a compromised choice for treatment planning or diagnosis.

Canadian orthodontist Internet user profile.

An anonymous, self-administered, mail-out survey of Canadian Orthodontists was conducted to evaluate the characteristics of orthodontic Internet use. The response rate was 45.6% (304 of 667). A total of 76.6% of orthodontists reported having Internet access at work, and an additional 12.4% reported having Internet access from a different location. Statistically significant associations between Internet usage and office staff size (P < .001) and years of practice (P = .046) were observed. Offices with larger staffs had greater Internet access. Number of staffs and number of case starts were positively correlated (P < .001, r = 0.498). The odds ratio for having Internet access on the basis of increased case starts from the less than 100 to 300-399 categories was 5.67. Although not statistically significant, there was a trend for greater Internet access by younger practitioners.

Perceptions and attitudes of Canadian orthodontists regarding digital and electronic technology.

INTRODUCTION: To plan for future acceptance and implementation of computer-related technology, it is necessary to understand orthodontists' current perceptions and attitudes toward emerging technologies. METHODS: An anonymous, self-administered, mail-out survey of Canadian orthodontists was conducted. The response rate was 45.6% (304/667). RESULTS: Most orthodontists indicated that computer technology could improve current practice efficiency and quality of patient care. Only 15% reported that digital models are quite or very useful; 73.6%, 69.1%, 55%, and 37.4% agreed or strongly agreed with using digital and electronic technology to consult with other dental specialists, other orthodontists, general dentists, and the public, respectively. Cost of the technology was reported as a significant or insurmountable obstacle by 54% of the respondents. Interprovincial legislation, unclear consultation remuneration guidelines, and lack of comfort with the technology were not perceived as significant obstacles. Only 36% reported security or privacy issues as a significant or insurmountable obstacle. CONCLUSIONS: Canadian orthodontists seem to view digital and electronic technology as useful and capable of improving their offices' efficiency and production. Although they are sensitive to some potential obstacles, they are willing to overcome these and incorporate the technology into their practices.

Predictors for Class II treatment duration.

BACKGROUND: The purpose of this study was to identify clinical factors that predict treatment length for patients with Class II malocclusions. METHODS: A sample of 237 active retention patients representing 3 observational groups (Angle Class I nonextraction, and Class II Division 1 extraction and nonextraction), based on specific selection criteria, was obtained from 3 private offices. From the patient records, data were collected in these categories: (1) patient information, (2) model information, (3) pretreatment cephalogram information, and (4) treatment information. Two regression analyses were completed, with total treatment time as the dependent variable for both models. RESULTS: The first regression analysis (Class I and Class II patients) indicated significant predictors for the patient, model, and cephalometric variables. These predictors included age, pretreatment overjet, and pretreatment ANB angle. The second regression analysis (Class II treatment variables) identified the following factors as significantly associated with treatment length: (1) type of Class II appliance, (2) number of months of Class II appliance wear, (3) number of months of interarch elastic wear, (4) maxillary expansion, (5) number of debonds, and (6) average time (weeks) between appointments. CONCLUSIONS: Six variables explained 56.7% of the variation in Class II treatment length. Further research is required to help explain more of the variance associated with treatment duration.

Use of skeletal maturation based on hand-wrist radiographic analysis as a predictor of facial growth: a systematic review.

The purpose of this systematic review was to evaluate the predictive value of hand-wrist radiographic assessment of skeletal maturity in estimating facial growth timing and velocity. A search of PubMed, Medline, Cochrane Database of Systematic Reviews, Embase, Web of Sciences, and Lilacs identified 16 articles that met the following inclusion criteria: use of hand-wrist radiographs for skeletal maturation determination, facial growth evaluated through cephalometric radiographs, and cross-sectional or longitudinal studies. Five articles were rejected because of major methodological issues. Most of the remaining articles had small sample size, and there was no report of randomization or method error. Skeletal maturity determined by hand-wrist radiographic analysis was well related to overall facial growth velocity. Maxillary and mandibular growth velocities were related to skeletal maturity, but their relationship was less robust than that for overall facial growth. The available articles have not adequately defined a relationship between cranial base growth velocity and skeletal maturity. Hand-wrist radiographic assessment of skeletal maturity for use in facial growth prediction should include bone staging as well as ossification events. The role of skeletal maturity assessment in clinical and research applications is discussed and recommendations are provided.

Effect of Herbst treatment on temporomandibular joint morphology: a systematic literature review.

The purpose of this systematic review was to evaluate the effect of Herbst appliance therapy on temporomandibular joint (TMJ) morphology, with special reference to glenoid fossa remodeling, condylar remodeling, condylar position, and articular disc position. Publications of controlled trials of Herbst treatment of Class II patients using magnetic resonance imaging (MRI), computerized tomography scans, or tomography to assess TMJ morphology were identified with Medline (1966-2001), Best Evidence (1991-2001), Cochrane Database of Systematic Reviews (second quarter, 2001), and Embase (1998-2001). Case reports were excluded. Based on our search, only 5 studies met the selection criteria. All studies used internal controls with pretreatment and posttreatment imaging. Four studies used MRI, and 1 used tomograms. The 4 MRI studies used overlapping patient samples and were not considered as independent evidence. The MRI studies did not provide conclusive evidence of osseous remodeling or condyle position change. The tomography study demonstrated minor condyle position change. Methodological deficiencies prevented major conclusions regarding disc position. The reviewed studies highlight the importance of further research. Prospective controlled studies using serial MRI and tomography are required to establish the effect of Herbst treatment on TMJ morphology.

Temporomandibular joint morphology changes with mandibular advancement surgery and rigid internal fixation: a systematic literature review.

The purpose of this systematic review was to evaluate the effect of bilateral sagittal split mandibular osteotomy (BSSO) with rigid internal fixation (RIF) on temporomandibular joint (TMJ) morphology. Controlled trials of BSSO with RIF treatment of Class II patients using transcranial radiographs, submental vertex (SMV) radiographs, tomographic radiography, computed tomography (CT) scan, or magnetic resonance imaging (MRI) to assess TMJ morphology were identified by Medline (1966-2001) and PubMed. Case reports were excluded. On the basis of our search only six studies were included in this review. All studies used internal controls with pre- and posttreatment imaging. Two studies used SMV, one used transcranial radiographs, one used tomography, two used CT scan and one used MRI. Methodological deficiencies prevent major conclusions regarding osseous remodeling and disk status. There was a wide range of individual variability in condyle position change. The reviewed studies have highlighted the importance of further research. Prospective controlled studies using serial MRI and tomography or CT scan are required to establish effect of BSSO with RIF on TMJ morphology.

Tomographic assessment of temporomandibular joint osseous articular surface contour and spatial relationships associated with disc displacement and disc length.

The objective of this retrospective study was to determine whether associations exist between osseous temporomandibular joint (TMJ) characteristics and TMJ internal derangement (disc position and deformation) in an adolescent population. Magnetic resonance imaging (MRI) was used to quantitatively determine disc position and length in 335 TMJs in 175 subjects (106 female and 69 male) between the ages of 7.27 and 20.0 years (mean age, 13.08 years). Nine tomographic variables were measured from pretreatment tomograms. Tomographic data were cross-referenced with MRI data. Male and female samples were evaluated separately. Stepwise linear regression identified associations between disc displacement and reduced superior joint space, increased posterior joint space, increased anterior joint space, and reduced articular eminence convexity (male R(2) value, 0.41; female R(2) value, 0.38). Associations between reduced disc length and condylar position and eminence flattening were weaker (male R(2) value, 0.16; female R(2) value, 0.32). This study demonstrates that TMJ internal derangement is associated with functional osseous adaptation within the joint.