DLX6 and MSX1 from saliva samples as potential predictors of mandibular size: A cross-sectional study.

INTRODUCTION: Morphologic features of the mandible are influenced by the genes of each individual. Mandible size is important to orthodontists because the mandible is the mechanism by which the lower face influences facial esthetics and dental function. To date, no biological marker has been identified that indicates eventual mandible size. This study aimed to correlate the expression of DLX5, DLX6, EDN1, HAND2, PRRX1, and MSX1 to mandible size. METHODS: Fifty-nine orthodontic patients aged >6 years who had available cephalometric radiographs were studied. Patients were classified on the basis of condylion-to-gnathion measurements. Messenger RNA was isolated from saliva and subjected to real-time quantitative polymerase chain reaction. RESULTS: Threshold cycle values for subjects with small mandibles (>1 standard deviation [SD] from the mean) had the least expression of DLX6 and MSX1. Threshold cycle values for subjects with large mandibles (>1 SD) had less expression of DLX6 and MSX1 than subjects within 1 SD but more than those with small mandibles. CONCLUSIONS: DLX6 and MSX1 are related to mandible development and size. This finding could be used to improve treatment planning for medical and dental professionals seeking to understand the impact of genetics on bone growth.

Three-dimensional mandibular dental changes with aging.

INTRODUCTION: This study aimed to evaluate the 3-dimensional (3D) mandibular dental changes over 42 years using the registration of digital models. METHODS: The sample comprised digital dental models of 8 untreated subjects (4 males and 4 females) with normal occlusion measured longitudinally at ages 17 years (T1) and 60 years (T2). Using 13 landmarks placed on the mucogingival junction, we registered the T2 model on the T1 model. Three-dimensional changes in the position of the landmarks on the buccal cusp tip of the posterior teeth and incisal edge of the central incisors were measured by 2 examiners. Registration and measurements were performed using SlicerCMF (version 3.1; http://www.slicer.org) software. Intra- and interrater agreements were evaluated using intraclass correlation coefficients and the Bland-Altman method. One-sample t tests were used for evaluating interphase 3D dental changes (P <0.05). RESULTS: Adequate intra- and interrater reproducibility was found. From T1 to T2, the mandibular teeth showed significant 3D positional changes. A significant dental eruption relative to the mucogingival junction was observed for the anterior and posterior teeth. Anteroposterior movements of mandibular teeth were not significant except for the right molar that drifted mesially. Transverse movements included slight lingual tipping at canines and premolars regions. CONCLUSIONS: Dental changes in untreated normal occlusion were very slight from early to mature adulthood. The eruption of the mandibular teeth was the most consistent finding. A tendency for mesial movement of molars and lingual movement of first premolars and canines was observed in the mandible during the aging process.

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.

Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper.

The Board of Trustees of the American Association of Orthodontists asked a panel of medical and dental experts in sleep medicine and dental sleep medicine to create a document designed to offer guidance to practicing orthodontists on the suggested role of the specialty of orthodontics in the management of obstructive sleep apnea. This White Paper presents a summary of the Task Force's findings and recommendations.

Longitudinal cephalometric growth of untreated subjects with Class II Division 2 malocclusion.

INTRODUCTION: Our objective was to evaluate the craniofacial growth of subjects with untreated Class II Division 2 malocclusion. METHODS: A mixed longitudinal sample of 39 white Class II Division 2 subjects was analyzed at 5 time points: T1 (6 or 7 years), T2 (9 or 10 years), T3 (12 or 13 years), T4 (15 or 16 years), and T5 (18 or 19 years). They were compared with an age- and sex- matched sample of Class I controls. Seventeen measurements (12 angular, 5 proportional) were computed. Multilevel modeling procedures were used to statistically describe the growth changes and to evaluate group differences. RESULTS: There were no group differences in the relative sizes and anteroposterior positions of the jaws during childhood, adolescence, or early adulthood. Subjects with Class II Division 2 malocclusion demonstrated significantly (P <0.05) smaller mandibular plane angles, smaller palatal-to-mandibular plane angles, larger posterior-to-anterior facial height ratios, smaller gonial angles, smaller cranial base angles, larger interincisal angles, and more retroclined maxillary incisors than did the Class I subjects. The hypodivergent patterns were established early and became more pronounced over time. Group differences in the mandibular plane angle, palatal-to-mandibular plane angle, gonial angle, interincisal angle, and maxillary incisor-to-cranial base angle, as well as the posterior-to-anterior facial height ratio all increased over time; the difference in the cranial base angle remained unchanged over time. Retroclination of the maxillary incisors occurred primarily during the early mixed dentition. CONCLUSIONS: Subjects with Class II Division 2 malocclusion are more hypodivergent and have more upright maxillary incisors than do subjects with Class I occlusion. Hypodivergence establishes itself early and increases progressively through early adulthood; maxillary incisor retroclination occurs early.

Relationship between body mass and dental and skeletal development in children and adolescents.

INTRODUCTION: The purpose of this investigation was to determine whether a relationship exists between body mass and dental and skeletal development in children and adolescents. A sample of 197 orthodontic patients (82 boys, 115 girls) was selected. Ethnicity was recorded, and body mass index (BMI) was calculated according to the standard equation from the Centers for Disease Control and Prevention, and then a BMI percentile according to sex and age was obtained. The panoramic radiographs were used to calculate the dental ages with an index. The chronologic ages were subtracted from the calculated dental ages to determine a "dental age difference" for each subject. The lateral cephalogram radiographs were analyzed for skeletal development using the cervical vertebral maturation stage method. RESULTS: The white population (60%) had an average BMI percentile of 53.6 and was statistically different from the Hispanic/black population (40%), which had an average percentile of 64.3. There were no significant differences for boys and girls for the BMI percentile and dental age difference, or for the BMI percentile and cervical vertebral stages. The multiple regression model showed that BMI percentile and ethnicity were statistically significant explanatory variables for the dental age difference. CONCLUSIONS: A relationship exists between body mass and dental and skeletal development. BMI percentile, dental age difference, and cervical vertebral stage are weakly correlated. No significant differences existed between boys and girls in any variables. BMI percentile and ethnicity are weak predictors of the discrepancy between dental age and chronologic age.

Posttreatment evaluation of maxillary canine positions in 15-year-old subjects.

INTRODUCTION: Esthetic improvement is a primary reason that people seek orthodontic treatment. The maxillary canine is considered by many to have great importance for both function and esthetics. Limited information is available about the position of the maxillary canine in relation to skeletal landmarks and whether the position can influence esthetic perceptions. The purposes of this study were to evaluate the normal maxillary canine position in relation to skeletal landmarks, to determine posttreatment 3-dimensional maxillary canine position with cone-beam computed tomography images, and to see whether maxillary canine position influences esthetic perceptions. METHODS: The Bolton standard template was used as the control sample, and the maxillary canine position was determined by implementing a Cartesian coordinate system. The right and left maxillary canines of 96 treated patients (48 boys, 48 girls; 15 years old) were analyzed by digitization of the cone-beam computed tomography volumes. The subjects' posttreatment smile photographs were ranked and quantified by 9 orthodontic residents who completed a Q-sort. Correlations were determined between canine positions and esthetic outcomes. RESULTS: The only difference between the right and left canine positions was the anteroposterior position of the root apex. Statistically significant sex differences were found for the superoinferior position of the right and left canine cusp tips, the mediolateral right and left canine root apices, and the mediolateral left canine cusp tips. No correlation was determined between the maxillary canine position and the esthetic perception. CONCLUSIONS: The maxillary canine position in relation to skeletal landmarks was determined and does not appear to significantly impact the esthetic perception, according to this study.

Evaluation of marginal alveolar bone in the anterior mandible with pretreatment and posttreatment computed tomography in nonextraction patients.

INTRODUCTION: Our objectives were to evaluate marginal alveolar bone height in the anterior mandible after orthodontic treatment and to assess any correlations between morphologic and treatment changes. METHODS: We used 57 pretreatment and posttreatment cone-beam computed tomography images (17 male and 40 female subjects; 22 Class I, 35 Class II; average age, 18.7 ± 10.8 years; average treatment time, 22.7 ± 7.3 months) to measure cortical bone thickness, ridge thickness, distance from the apex to the labial cortical bone, and the distance from the cementoenamel junction to the marginal bone crest. Changes in the cementoenamel junction to the marginal bone crest distance were correlated with pretreatment measurements and treatment changes. RESULTS: Although there were great variations, the average facial and lingual vertical bone losses were 1.16 ± 2.26 and 1.33 ± 2.50 mm, respectively. The incisor-mandibular plane angle changes were also highly variable, averaging 2.4°. CONCLUSIONS: Orthodontic treatment causes changes in alveolar bone height and cortical bone thickness around the mandibular incisors. Although pretreatment cortical bone thickness, ridge width thickness, and specific tooth movements all play roles in what happens to the bone during treatment, incisor inclination was not correlated with alveolar bone height changes.

Extraction vs no treatment: Long-term facial profile changes.

INTRODUCTION: Long-term soft tissue response to extraction orthodontic treatment has been a subject of interest for years. The purposes of this study were to investigate long-term soft tissue profile changes in an extraction sample and to compare them with profile changes in an untreated sample. METHODS: A premolar extraction-treated sample (n = 47) and an untreated control sample (n = 57) were studied. Descriptive statistics were collected, and individual t tests were used for comparison and contrast of the treated and untreated samples. RESULTS: We found that the untreated soft tissue profile changed in the downward and forward direction. The treated soft tissue profile change was similar, but with more of a forward component than in the untreated sample. Most noteworthy was the finding that the soft tissue profiles of both the untreated and the treated samples were similar at the end point. CONCLUSIONS: The following conclusions were derived from the study. (1) There was no substantive difference in the soft tissue profiles of the samples, but there were some differences in the directional changes between them. (2) The changes for the untreated sample were the greatest for the lips and the chin, with the change occurring in the downward and forward direction. (3) The soft tissue profiles of the extraction sample also had the greatest measurable changes in the lips and the chin, but the changes had more of a forward component than they did in the untreated sample. (4) Extraction treatment does not adversely impact soft tissue profile changes over time.

Treatment effects of a modified palatal anchorage plate for distalization evaluated with cone-beam computed tomography.

INTRODUCTION: The purpose of this study was to evaluate the treatment effects of maxillary posterior tooth distalization performed by a modified palatal anchorage plate appliance with cephalograms derived from cone-beam computed tomography. METHODS: The sample consisted of 40 lateral cephalograms obtained from the cone-beam computed tomography images of 20 Class II patients (7 men, 13 women; average age, 22.9 years) who underwent bilateral distalization of their maxillary dentition. The lateral cephalograms were derived from the cone-beam computed tomography images taken immediately before placement of a modified palatal anchorage plate appliance and at the end of distalization. Paired t tests were used for comparisons of the changes. RESULTS: The distal movement of the maxillary first molar was 3.3 ± 1.8 mm, with distal tipping of 3.4° ± 5.8° and intrusion of 1.8 ± 1.4 mm. Moreover, the maxillary incisors moved 3.0 ± 2.7 mm lingually, with lingual tipping of 6.2° ± 7.6° and insignificant extrusion (1.1 mm; P = 0.06). The occlusal plane angle was increased significantly (P = 0.0001). CONCLUSIONS: The maxillary first molar was distalized by 3.3 mm at the crown and 2.2 mm at root levels, with distal tipping of 3.4°. It is recommended that clinicians should consider using the modified palatal anchorage plate appliance in treatment planning for patients who require maxillary total arch distalization.