Ashima Valiathan

Skeletal response to maxillary protraction with and without maxillary expansion: a finite element study.

INTRODUCTION The purpose of this finite element study was to evaluate biomechanically 2 treatment modalities-maxillary protraction alone and in combination with maxillary expansion-by comparing the displacement of various craniofacial structures. METHODS Two 3-dimensional analytical models were developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry young skull. AutoCAD software (2004 version, Autodesk, San Rafael, Calif) and ANSYS software (version 10, Belcan Engineering Group, Cincinnati, Ohio) were used. The model consisted of 108,799 solid 10 node 92 elements, 193,633 nodes, and 580,899 degrees of freedom. In the first model, maxillary protraction forces were simulated by applying 1 kg of anterior force 30 degrees downward to the palatal plane. In the second model, a 4-mm midpalatal suture opening and maxillary protraction were simulated. RESULTS Forward displacement of the nasomaxillary complex with upward and forward rotation was observed with maxillary protraction alone. No rotational tendency was noted when protraction was carried out with 4 mm of transverse expansion. A tendency for anterior maxillary constriction after maxillary protraction was evident. The amounts of displacement in the frontal, vertical, and lateral directions with midpalatal suture opening were greater compared with no opening of the midpalatal suture. The forward and downward displacements of the nasomaxillary complex with maxillary protraction and maxillary expansion more closely approximated the natural growth direction of the maxilla. CONCLUSIONS Displacements of craniofacial structures were more favorable for the treatment of skeletal Class III maxillary retrognathia when maxillary protraction was used with maxillary expansion. Hence, biomechanically, maxillary protraction combined with maxillary expansion appears to be a superior treatment modality for the treatment of maxillary retrognathia than maxillary protraction alone.

Cephalometric assessment of dentofacial vertical changes in Class I subjects treated with and without extraction

INTRODUCTION There is disagreement concerning the effect of premolar extractions on the dentofacial vertical dimension. It has been suggested that orthodontic forward movement of the posterior teeth after first premolar extraction leads to reduction in vertical dimension. The purpose of this study was to examine cephalometrically the dentofacial vertical changes in Class I Indian subjects treated with and without extractions. METHODS The extraction group included 31 normodivergent patients (26 female, 5 male; pretreatment age, 17.19 +/- 3.89 years) with maxillary and mandibular first premolar extractions. The nonextraction group included 29 patients (18 female, 11 male; pretreatment age, 18.48 +/- 3.61 years). A coordinate system with the Frankfort horizontal plane and a mandibular fiduciary line was used for the cephalometric calibration. To determine vertical dimension changes due to treatment and to compare differences between the 2 groups, paired and unpaired t tests were performed, respectively. RESULTS Both groups had increases in linear vertical dimensions (P <0.05), but the change was comparatively greater in the extraction group (P <0.05). Mesial movement of the maxillary and mandibular posterior teeth was coincidental with the extrusion to such an extent that it increased the vertical dimension, although the mandibular plane angle remained unchanged during treatment. CONCLUSIONS Extraction of teeth only to increase the overbite or decrease the mandibular plane angle might not be justified.

Craniofacial displacement in response to varying headgear forces evaluated biomechanically with finite element analysis

INTRODUCTION The aim of this study was to evaluate biomechanically the displacement patterns of the facial bones in response to different headgear loading by using a higher-resolution finite element method model than used in previous studies. METHODS An analytical model was developed from sequential computed tomography scan images taken at 2.5-mm intervals of a dry skull of a 7-year-old. Different headgear forces were simulated by applying 1 kg of posteriorly directed force in the first molar region to simulate cervical-pull, straight-pull, and high-pull headgear. Displacements (in mm) of various craniofacial structures were evaluated along the x, y, and z coordinates with different headgear loading. RESULTS All 3 headgears demonstrated posterior displacement of the maxilla with clockwise rotation of the palatal plane. The distal displacement of the maxilla was the greatest with the straight-pull headgear followed by the cervical-pull headgear. The high-pull headgear had better control in the vertical dimensions. The midpalatal suture opening was evident and was more pronounced in the anterior region. The articular fossa and the articular eminence were displaced laterally and postero-superiorly with each headgear type. CONCLUSIONS The high-pull headgear was most effective in restricting the antero-inferior maxillary growth vector. Midpalatal suture opening similar to rapid maxillary expansion was observed with all 3 headgear types. The center of rotation varied with the direction of headgear forces for both the maxilla and the zygomatic complex. A potential for chondrogenic and osteogenic modeling exists for the articular fossa and the articular eminence with headgear loading.

Influence of first premolar extraction on mandibular third molar angulation.

OBJECTIVE To compare the angular changes in the developing mandibular third molars in both first premolar extraction and nonextraction cases and to determine whether premolar extraction results in a more mesial movement of the mandibular buccal segment and causes favorable rotational changes in the mandibular third molar tilt, which can enhance later eruption of the third molars. MATERIALS AND METHODS Pretreatment (T1) and posttreatment (T2) panoramic radiographs were taken of 25 subjects who had been treated by the extraction of all the first premolars and 25 subjects who had been treated with nonextraction. The horizontal reference plane was used to measure and compare the changes in the angles of the developing mandibular third molars. RESULTS The mean uprighting of the mandibular third molars seen in the extraction group was 8.2 +/- 5.4 degrees on the left side and 6.3 +/- 6.5 degrees on the right side following treatment (T2 - T1). For the nonextraction group the mean difference was 1.3 +/- 4.3 degrees on the left side and 1.7 +/- 5.4 degrees on the right side. There was a statistically significant difference between the groups (P = .012 on the right side and P < .001 on the left side). CONCLUSIONS Premolar extractions had a positive influence on the developing third molar angulations. Nonextraction therapy did not have any adverse effects.

Unusual intraosseous transmigration of impacted tooth

Transmigration of an impacted tooth through the symphyseal suture is a rare and special developmental anomaly of unknown etiology that is unique to the mandibular canine. Maxillary canine transmigration is even rarer. Transmigrated canines are particularly significant due to the aesthetic and functional importance. A maxillary lateral incisor crossing the mid-palatal suture has never been reported in the literature. The aim of this report is to present the first case of simultaneous transmigration of a lateral incisor and canine in the maxilla. The paper also reports four unusual cases of unilateral canine transmigration in the maxilla and mandible and successful eruption of one of the transmigrated mandibular canines following orthodontic traction. Etiology of transmigration and its clinical considerations are also discussed.

Interdisciplinary treatment of a periodontally compromised adult patient with multiple missing posterior teeth.

This article reports the comprehensive, interdisciplinary treatment of a 50-year-old periodontally compromised adult patient with multiple missing posterior teeth. After initial periodontal treatment, the maxillary first molars and right central incisor were intruded orthodontically. Miniscrews were used to intrude the maxillary first molars by 3 mm. The mandibular arch was restored with a tooth-supported overdenture. Root coverage of the maxillary right central incisor was performed using Alloderm (Biohorizons, Birmingham, Ala). At the end of the interdisciplinary therapy, the results were esthetically pleasing, with the patients oral functions restored to the optimum. The emphasis of this report is to highlight the importance of integrating various specialties such as periodontics, orthodontics, endodontics, and restorative dentistry toward a common goal of improving the patients oral health, function, and esthetics.

An evaluation of the Pi analysis in the assessment of anteroposterior jaw relationship

Objective This study has investigated two new cephalometric variables, the Pi angle and Pi linear in the evaluation of anteroposterior skeletal discrepancy. Design Retrospective cross-sectional study. Setting Manipal College of Dental Sciences, Manipal, India Subjects and method A sample of 155 subjects (mean age 19·7 years) were subdivided into skeletal class I, II and III groups based upon ANB angle. Descriptive data were calculated for each variable and group. Receiver operating characteristics curves were used to examine sensitivity and specificity of the Pi angle in the discrimination between different skeletal groups. Correlation coefficients were obtained for each of the parameters to compare their relationship with other parameters in the class I group. Coefficient of determination, regression coefficient, regression equation and standard error of estimate were also calculated from the parameters showing significant correlation with the Pi angle. Results Mean values for the Pi angle in skeletal class I, II and III subjects were 3·40 (±2·04), 8·94 (±3·16) and −3·57 (±1·61) degrees, respectively. For the Pi linear they were 3·40 (±2·20), 8·90 (±3·56) and −3·30 (±2·30) mm for class I, II and III subjects, respectively. Receiver operating characteristic curves showed that a Pi angle greater than 5 degrees had 89% sensitivity and 82% specificity for discriminating a skeletal class II group from class I. A Pi angle of less than 1·3 degrees had 100% sensitivity and 84% specificity in discriminating skeletal class III groups from class I. The overall accuracy for discriminating class II groups from class I was 85% and for class III from class I, 90%. Thus, a cut-off point between class I and II groups could be considered a Pi angle of approximately 5 degrees and between class I and class III, approximately 1·3 degrees. There were no statistically significant correlations found between Pi angle and ANB (0·07), Beta angle (−0·04) and WITS analysis (0·19). The highest level of correlation was obtained for the Pi angle and Pi linear (0·96). Conclusion The anglar and linear components of the Pi analysis are a suitable method for assessing anteroposterior jaw discrepancy in daily clinical practice.

A comparative evaluation of the retention of metallic brackets bonded with resin-modified glass ionomer cement under different enamel preparations: A pilot study

Introduction: For orthodontists, the ideal bonding material should be less moisture-sensitive and should release fluoride, thereby reducing unfavorable iatrogenic decalcification. Resin-Modified Glass Ionomer Cements (RMGICs), due to their ability to bond in the presence of saliva and blood can be a very good bonding agent for orthodontic attachments especially in the areas of mouth, which are difficult to access. Moreover, their fluoride releasing property makes them an ideal bonding agent for patients with poor oral hygiene. However, their immediate bond strength is said to be too low to immediately ligate the initial wire, which could increase the total number of appointments. The effect of sandblasting and the use of sodium hypochlorite (NaOCL) on the immediate bond failure of RMGIC clinically have not been reported in the literature until the date. This investigation intended to assess the effect of sandblasting (of the bracket base and enamel) and NaOCL on the rate of bond failure (with immediate ligation at 30 min) of Fuji Ortho LC and its comparison with that of conventional light cured composite resin over a period of 1 year. Materials and Methods: 400 sample teeth were further divided into 4 groups of 100 each and bonded as follows: (1) Group 1: Normal metallic brackets bonded with Fuji Ortho LC. (2) Group 2: Sandblasted bracket base and enamel surface, brackets bonded with Fuji Ortho LC. (3) Group 3: Deproteinized enamel surface using sodium hypochlorite and brackets bonded with Fuji Ortho LC. (4) Group 4: Normal metallic bracket bonded with Transbond XT after etching enamel with 37% phosphoric acid. This group served as control group. Results and Conclusion: Results showed that sandblasting the bracket base and enamel, can significantly reduce the bond failure rate of RMGIC.

Investigation of the transmigrated canine in an orthodontic patient population

Objective To investigate the prevalence, demographic and clinical characteristics of transmigrated canines in a south Indian orthodontic patient population. Design Retrospective observational study. Setting Manipal University, Manipal, India. Subjects and methods Panoramic radiographs of 3500 patients were examined and data collected regarding the number and side of transmigrated canines, sex and age of patients, any other associated pathologies and subsequent treatment. Transmigrated canines were classified according to Mupparapus classification. Results The prevalence of transmigrated canines in this population was found to be 0·46% of which, seven were males (age: 17–51 years) and nine were females (age: 17–35 years). All transmigrated canines were unilateral and impacted. Eleven canines migrated from the left to the right side, and five migrated from the right to the left. Of the 16 patients, 13 had retained primary canines and 3 had exfoliated primary canines. Eight canines exhibited a type 1 transmigratory pattern, type 2, type 4 and type 5 transmigratory patterns were exhibited by two canines each. One of the canines was classified as type 3. Three canines were associated with dentigerous cyst formation. Four cases were treated by orthodontic traction, while one was removed surgically. Others were observed periodically. Conclusions Diagnosis of transmigration at earlier stages is important to prevent more complex occlusal problems.

Correction of bilateral impacted mandibular canines with a lip bumper for anchorage reinforcement

Multiple treatment options are available to patients with impacted manibular canines in addition to a retained deciduous canine. This article describes the treatment of a prepubertal girl, aged 10 years 6 months, with a skeletal Class I, dental Class II Division 1 malocclusion, retrognathic mandible, deep overbite, proclined maxillary incisors, midline diastema, and bilateral mandibular canine impaction. The orthodontic treatment plan included extraction of the deciduous canine and forced eruption of the impacted canines. A modified lip bumper appliance was used both for forced eruption and to reinforce anchorage. Through the collaborative efforts of an orthodontist and an oral surgeon, an excellent esthetic and functional outcome was achieved.