Angulation Of Maxillary Incisors Research Articles

Machine Learning Algorithms for the Diagnosis of Class III Malocclusions in Children.

This study aims to propose an innovative machine learning (ML)-based diagnostic model for automatically classifies dental, skeletal and functional Class III malocclusions. The collected data related to 46 cephalometric feature measurements from 4-14-year-old children (n = 666). The data set was divided into a training set and a test set in a 7:3 ratio. Initially, we employed the Recursive Feature Elimination (RFE) algorithm to filter the 46 input parameters, selecting 14 significant features. Subsequently, we constructed 10 ML models and trained these models using the 14 significant features from the training set through ten-fold cross-validation, and evaluated the models' average accuracy in test set. Finally, we conducted an interpretability analysis of the optimal model using the ML model interpretability tool SHapley Additive exPlanations (SHAP). The top five models ranked by their area under the curve (AUC) values were: GPR (0.879), RBF SVM (0.876), QDA (0.876), Linear SVM (0.875) and L2 logistic (0.869). The DeLong test showed no statistical difference between GPR and the other models (p > 0.05). Therefore GPR was selected as the optimal model. The SHAP feature importance plot revealed that he top five features were SN-GoMe (the ratio of the length of the anterior skull base SN to that of the mandibular base GoMe), U1-NA (maxillary incisor angulation to NA plane), Overjet (the distance between two lines perpendicular to the functional occlusal plane from U1 and L), ANB (the difference between angles SNA and SNB), and AB-NPo (the angle between the AB and N-Pog line). Our findings suggest that ML models based on cephalometric data could effectively assist dentists to classify dental, functional and skeletal Class III malocclusions in children. In addition, features such as SN_GoMe, U1_NA and Overjet can as important indicators for predicting the severity of Class III malocclusions.

Relationship of Maxillary Incisor Angulation with Upper Lip Strain

Relationship of Maxillary Incisor Angulation with Upper Lip Strain

Comparative Analysis of the Differences in Dentofacial Morphology According to the Tongue and Lip Pressure.

The aim of this study was to evaluate the effects of the tongue and lip pressure on dentofacial morphology. The subjects comprised 194 patients with malocclusion. Anterior and posterior tongue elevation and lip pressures were evaluated using the Iowa Oral Performance Instrument (IOPI) device. The lateral cephalograms of each subject were traced and digitized to perform the analysis. Statistical analysis was used to investigate the relationship between perioral muscle force and the cephalometric variables. Anterior and posterior tongue pressure was both higher in males than in females. No sex difference in lip pressure was observed. The group with a low posterior tongue pressure showed a short ramus height, short posterior facial height, and clockwise-rotated mandible. On the other hand, lip pressure had a significant influence on maxillary incisor angulation. Skeletal pattern was not found to be significantly related with lip pressure. The anterior tongue pressure appeared as a mixed pattern of the two results. Tongue pressure was related to skeletal measurements, such as short posterior facial height, and lip pressure was related to the angulation of the anterior teeth. This study suggests that there may be differences in dentofacial morphology according to the differences in perioral muscle force.

Clinical assessment of the palatal alveolar bone thickness and its correlation with the buccolingual angulation of maxillary incisors for immediate implant placement.

Clinicians needed to be aware of the thinness of the palatal bone plate when identifying severe protrusion of maxillary incisors, as this could result in perforation of the palatal bone plate during surgical procedures associated with immediate maxillary implant placement. This study evaluated the thickness of the palatal bone plate, the buccolingual angulation of maxillary incisors, and the correlation between these two parameters in relation to immediate implant placement. Cone-beam computed tomography images of 37 Asian patients (20-60 years old) with no evidence of dental treatment in the maxillary incisor area were collected and classified into groups based on sex and incisor locations. Sagittal slices were used to measure the palatal bone plate thickness at the cervical, middle, and apical levels, and the buccolingual angulation of each tooth was also measured. The intraclass correlation, Shapiro-Wilk test, descriptive analysis, Student's t-test, and Pearson correlation were used for statistical and correlation analyses, with P < .05 applied as the criterion for statistical significance. At the apical level of all inspected teeth and the middle level of lateral incisors, the palatal bone was significantly thicker in males than in females. The inclination of the maxillary lateral incisor showed a moderate negative linear correlation with the palatal bone thickness at the apical level (R = -0.517 and R = -0.579 for males and females, respectively). In an Asian population, an increased buccolingual angulation of the maxillary lateral incisors was correlated with a thinner palatal bone plate at the apical level.

Effects of orthopedic skeletal Class III correction in growing subjects using skeletal anchorage and Class III elastics

Aim of the study: The objective of this study was to evaluate the skeletal and dental effects of intermaxillary Class III elastics using bone anchored miniplates compared to an untreated Class III control group.Subjects and methods: 24 subjects (14 females and 10 males) having skeletal Class III malocclusion with maxillary deficiency with an age range of 8-11 years old were divided into two groups 12 patients each (n=12). Group A constituted treatment with Class III elastics anchored to 4 titanium miniplates, 2 anchored in the zygomatic buttress of the maxilla and 2 miniplates anchored in the symphyseal region of the mandible at the lateral/canine region. Group B (n=12) constituted untreated skeletal Class III cases (control group). The treatment and observation periods for both groups were 8 months. Lateral cephalometric radiographs were taken for the patients at start of treatment (T1) and at the end of the treatment/observation periods (T2). The radiographs were analyzed by performing lateral cephalometric analysis. Independent student t test was done to compare variables between the two groups.Results: There was correction of the skeletal Class III in the miniplates group with statistically significant increase in angle SNA (mean 3.50° ± 0.68), A-Nperp (mean 4.04mm ± 1.20), ANB (mean 4.06◦±0.95) and Witts appraisal (mean 4.91mm ± 1.76) .Slight mandibular retrusion occurred with a reduction in angle SNB (mean -0.56◦ ±0.57). Changes in B-Nperp were (-1.85mm±1.36).Overjet correction was obtained and no significant changes in the maxillary incisor angulation was observed. There was proclination of mandibular incisors by (mean 6.43◦±2.11).Conclusions: The use of intermaxillary Class III elastics and miniplates in the orthopedic treatment of skeletal Class III is a successful technique with more skeletal than dental effects.

Effect of Crown Angulation of Maxillary Incisor on Effective Arch Perimeter.

It has been postulated that crown angulation and inclination has potential space implication within the arch. With the insight of space implication of the axial relations of teeth, cases of genuine tooth size discrepancies can be dealt with improved stability. This in vitro study was designed to investigate and quantify the influence of angulation and inclination of maxillary incisors on the effective arch perimeter. Acrylic teeth were arranged over typhodont frame with spaced maxillary anterior segment. Known value of tip and torque in increments were incorporated to maxillary incisors through bracket positioning and corresponding consumption of the interdental spaces were measured using coordinate measuring machine. Study revealed that increase in maxillary incisor crown angulation by 1o results in consumption of approximately 0.012 mm of arch perimeter. Similarly, there is a consumption of 0.021 mm of arch perimeter with each degree increase in labial crown inclination. The knowledge of the space implication can be included in the space analysis during the orthodontic treatment planning. Depending upon the amount of space discrepancy, an accurate degree of required alteration in the axial relation of one or more teeth can be planned.

Phenotypic diversity in white adults with moderate to severe Class II malocclusion

Class II malocclusion affects about 15% of the population in the United States and is characterized by a convex profile and occlusal disharmonies. The specific etiologic mechanisms resulting in the range of Class II dentoskeletal combinations observed are not yet understood. Most studies describing Class II phenotypic diversity have used moderate sample sizes or focused on younger patients who later in life might outgrow their Class II discrepancies; such a focus might also preclude the visualization of adult Class II features. The majority have used simple correlation methods resulting in phenotypes that might not be generalizable to different samples and thus might not be suitable for studies of malocclusion etiology. The purpose of this study was to address these knowledge gaps by capturing the maximum phenotypic variations in a large sample of white Class II subjects selected with strict eligibility criteria and rigorously standardized multivariate reduction analyses. Sixty-three lateral cephalometric variables were measured from the pretreatment records of 309 white Class II adults (82 male, 227 female; ages, 16-60 years). Principal component analysis and cluster analysis were used to generate comprehensive phenotypes to identify the most homogeneous groups of subjects, reducing heterogeneity and improving the power of future malocclusion etiology studies. Principal component analysis resulted in 7 principal components that accounted for 81% of the variation. The first 3 components represented variation on mandibular rotation, maxillary incisor angulation, and mandibular length. The cluster analysis identified 5 distinct Class II phenotypes. A comprehensive spectrum of Class II phenotypic definitions was obtained that can be generalized to other samples to advance our efforts for identifying the etiologic factors underlying Class II malocclusion.

Maxillary incisors mesiodistal angulation changes in patients with orthodontically treated anterior superior diastemas

OBJECTIVE: The aims of this study were to describe the patterns of maxillary incisor angulation in patients with upper interincisive diastemas, to evaluate angulation changes with treatment and posttreatment period, and to assess whether there are association between incisor angulation and interincisive diastema relapse. METHODS: The sample comprised 30 Class I or Class II patients with at least one pretreatment anterior diastema of 0.77 mm or greater after eruption of maxillary permanent canines. Data were obtained from panoramic radiographs at pretreatment, posttreatment and at least 2 years post-retention. RESULTS: Incisors presented a mesial tipping tendency after treatment, but only lateral incisors showed significant changes between pre and posttreatment stages. CONCLUSION: Regarding post-retention period, no changes were found. Finally, no relation was found between diastema relapse and maxillary incisor axial angulation.

Relationship between maxillary canine intra-alveolar position and maxillary incisor angulation: a cone beam computed tomography study

The aims of the present study were to evaluate the angulation and inclination of permanent maxillary incisors and to correlate the results to the intra-alveolar permanent maxillary canine position during mixed dentition, using cone beam computed tomography (CBCT). The subjects were 30 children aged 7 to 10 years in the inter-transitory period of mixed dentition (permanent incisors and first molars erupted; primary canines, first and second molars erupted; and permanent canines intraosseous). The CBCT scans were obtained and, using the Dolphin Imaging(®) software - version 11.0, 3D images were reconstructed and the measurements were performed. The angulation of the right and left lateral and central maxillary incisors was measured in relation to the sagittal plane and their inclination was measured in relation to the coronal plane. The intra-alveolar height of the right and left maxillary canines was measured from the cusp tip to the axial plane. Pearson's correlation at 5% significance level showed positive correlation between the canine height and the lateral incisor angulation. It was concluded that the intra-alveolar position of the maxillary canines has a direct influence on the angulation of maxillary incisors, especially the lateral incisors.

Maxillary Incisor Angulation and Its Effecton Molar Relationships

To determine the variation in molar relationships when upper incisor angulations are altered in a Class I occlusion with normal overjet and overbite. Typodonts were set up to simulate a Class I occlusion on a normal skeletal base. The lower incisors were positioned normally at 92 degrees to the mandibular plane and the upper incisor angulations were altered from 90 degrees to 130 degrees by 2 degrees increments to the palatal plane. The changes in molar relationships were measured with every 2 degrees of upper incisor angulation change. A regression analysis was performed on the experimental data, and the regression coefficients, slope, and intercept were estimated. A negative linear relationship between upper incisor angulations and change in molar relationship was observed. On average, a change of 20 degrees in upper incisor angulation will alter the molar relationship by 1.8 mm. Changes in upper incisor angulations are significantly related to change in the molar relationship. Upper incisor angulations that deviate significantly from normal values are likely to result in less than ideal buccal segment relationships.

Variation in Class II malocclusion: Comparison of Mexican mestizos and American whites

This study compared the skeletal and dental characteristics of Class II Division 1 white Americans and Mexicans. It was designed specifically to the evaluate ethnic, age, and sex differences of 101 whites and 107 Mexican mestizos, with approximately equal numbers in each subgroup. Three-way analyses of variance were used to simultaneously evaluate the effects of age, sex, ethnicity, and their interactions. Although Mexicans and whites in the United States had similar maxillomandibular relationships, Mexicans showed greater protrusion of the jaws and teeth. Mexican subjects with Class II malocclusions also showed less divergence of the cranial base (SN-FH angle) and greater vertical tendencies (MPA, Y-axis, and palatal plane angle) than their white counterparts. In comparison with children (mean age 9.0 years), young adults (mean age 20.1 years) had significantly larger craniofacial dimensions, jaws that were positioned more forward, and teeth that were more protruded. Sex differences pertained only to size (men were larger) and maxillary incisor angulation (men were more protrusive). The findings pertaining to the ethnic differences have important clinical implications regarding treatment decisions for Mexican and white patients. In addition, this study provides a foundation for future studies pertaining to Class II malocclusion in Mexicans.

Effect of maxillary incisor angulation and inclination on arch length

This article discusses the quantitative effects of angulation of incisors on dental arch length. The incisors are approximated mathematically to rectangular shapes, which enables the authors to calculate the change in arch length when teeth are tipped and to describe graphically the effect of other influencing parameters. The authors demonstrate that the height and the width of a tooth crown can enhance or diminish the effect of angulation on arch length. In addition to angulation, dental arch length is also influenced by torque. A mathematic formula has been derived and the results are demonstrated numerically and graphically. The authors show that vertical positioning of the brackets plays an important role because torquing is a rotational movement around the center of the bracket slot. Hence, in calculating the effect of torque on dental arch length, one must consider different angles and axes than those discussed by Andrews. The interaction between angulation and inclination and its influence on dental arch length has been investigated. It has been found to cause little change in arch length.

Variation in morphology of the maxillary central incisors found in Class II, Division 2 malocclusions

Class II, Division 2 malocclusions show several common characteristics. One of the features is the presence of a deep overbite (“deckbiss”), which can be the result of an excessive eruption of the maxillary central incisors. This study tested the theory that the deep overbite, together with the apparent entrapment of the mandible, may be partly due to the bending of the maxillary central incisors or the presence of the Collum angle. In a comparison between the group of patients with Class II, Division 2 malocclusions and the control group, it was determined that the former group exhibited significantly larger Collum angles than the latter group (p < 0.005). It is suggested that in describing the maxillary incisor angulation in this type of malocclusion, the long axis of the crown, rather than the long axis of the tooth connecting the incisal edge to the apex, be used as a measure of their position.