Correlations between mandibular ramus height and occlusal planes in Han Chinese individuals with normal occlusion: A cross-sectional study

Objectives: The objective of the study is to determine the relationships between ramus height and occlusal planes (OPs) in Han Chinese individuals with normal occlusion. Materials and Methods: Two hundred and four participants with normal occlusion were included and their cephalograms were analyzed. The ramus height (Ar-Go), Frankfort horizontal plane-posterior OP (FH-POP), FH-anterior OP (FH-AOP) and FH-OP, anterior and posterior cranial base length, SNA, SNB, ANB, Frankfort-mandibular plane angle, SN-MP, jaw angle, and mandibular body length were measured on the subjects’ cephalograms. Pearson correlation coefficients were calculated among continuous variables. The ramus height was considered as dependent variable and the OPs as independent variables. Age, sex, and other cephalometric parameters were considered as possible confounding factors. Univariate and multivariate analyses were performed to determine whether the relationships were significant. Results: The FH-POP and FH-OP were moderately associated with ramus height, while the FH-AOP showed a weak association (P < 0.001). After adjusting age and sex, FH-POP, FH-AOP, and FH-OP showed significant negative associations with ramus height (β = −0.36, −0.28, and −0.37, respectively, P < 0.001). The OP flattened with the ramus height increased. After adjusting all the confounding factors, FH-POP and FH-OP showed significant negative associations with ramus height. The ramus height increased by 0.19 mm/1° flattening of FHPOP (β = −0.19, P = 0.002). Conclusion: After adjust age, sex, and other possible confounding factors, the FH-POP and FH-OP were associated with the ramus height. The flattening of FH-POP was associated with the increase of ramus height. The results should be treated with caution since it’s a cross-sectional study.

Evaluation of Postsurgical Stability And Condylar Morphology In Skeletal Class II Patients With Condylar Resorption Following Orthognathic Surgery

Background: To retrospectively evaluate postsurgical stability and condylar morphology for skeletal class II malocclusion patients with condylar resorption (CR) treated with orthognathic surgery.Methods: Thirty-five patients treated with combined orthodontic and orthognathic surgery between 2014 and 2018 were enrolled in this retrospective study. CT scans were acquired preoperatively (T0), 2–7 days after surgery (T1), and 1 year postoperatively (T2). The amount of mandibular advancement, postsurgical relapse, condylar morphology and joint spaces were analysed respectively. Statistical analysis was performed using R, version 3.4.3 (R Development Core Team 2010).Results: The average mandibular advancement and counter-clockwise rotation were 5.51 mm and -2.82 degrees respectively. The average relapse was 1.08 mm (19.6% of the advancement) and 1.13 degrees. The condylar volume showed a postoperative reduction of 161.86 mm3(13.7% of initial condylar volume). AJS increased after surgery and gradually returned to its original state, while SJS and PJS decreased and remained stable. Surgical advancement of B point was significantly correlated with skeletal relapse. The optimal cut-off values were as follows: MP-FH (40.75°); ramus height (51.125 mm); SJS (1.63 mm); surgical displacement (4.72 mm); CCR (-4.3°); AJSC (1.07 mm).Conclusions: Skeletal class II patients with CR have a high risk of postsurgical condylar resorption, which was most related to nonsurgical risk factors such as gender(female) and condylar angle. Condylar had moved posteriorly to the concentric position after surgery and remained quite stable through the 1-year follow-up. Preoperative skeletal patterns such as lower ramus height and surgical procedures such as larger advancement of the mandible were closely associated with sagittal relapse of the mandible.

Semi-Rigid Fixation Using a Sliding Plate for Treating Fractures of the Mandibular Condylar Process

Occlusal displacement often occurs after surgery for condylar process fractures because it is difficult to reduce these fractures precisely. However, performing semi-rigid fixation using a sliding plate may overcome this limitation. A retrospective clinical comparison between semi-rigid and rigid fixations was performed. Among 34 patients who had unilateral condylar process fractures, 17 were treated with rigid fixation and the remaining with semi-rigid fixation using a sliding plate. For all patients, panoramic radiographs were collected 1 day and 6 months after surgery. In these radiographs, ramus height and condylar process inclination were measured, and the differences between the fractured and normal sides were assessed. Additionally, the radiographic density of the fracture area was measured. Differences in surgical outcomes and operative times between the two groups and changes in postoperative deviations within each group were analyzed. There was no statistically significant difference in ramus height and condylar process inclination between the two groups at postoperative day 1 and 6 months. Radio-density was observed to be higher in the rigid fixation group, and it increased with time in both groups. The semi-rigid fixation group had a significantly shorter operative time than the other group did. Semi-rigid and rigid fixations showed no differences in terms of effectiveness and outcomes of surgery. In terms of operative time, semi-rigid fixation was superior to rigid fixation.

Orthopantomography and use of Mandibular Indices for the Evaluation of Gender Distribution in Navi Mumbai Population - A Retrospective, Single Blind Study

Introduction: The study of forensic sciences often leaves the forensic expert to draw conclusions from any and every material available in determining the identity of the deceased. The initial step in identifying a person is to determine their gender based on their adult skeleton. The human skeleton displays sexual dimorphism, of which the skull is most dimorphic providing an accurateness of 92%. However, in certain situations where the skull may not be found intact, the mandible plays a vital role. The mandible's thick covering of compact bone helps keep it from exploding during a mass tragedy. Dimorphism in the mandible is gender specific and is mainly reflected in its shape and size. The mandible is also easily radiographed and specific linear measurements of the mandibular rami as seen on an OPG are useful indices for gender determination. Aims: To examine the efficacy of mandibular rami measures such as maximum ramus breadth, maximum ramus height, minimum ramus breadth, condylar height, coronoid height, mandibular body length and gonial angles on the right and left side of an OPG in determining gender. Materials and methods: 110 digital OPG’s (55 males, 55 females) of a Navi Mumbai population were obtained retrospectively from a reputed dental college and hospital. The OPG’s were taken using Xtropan 2000 OPG machine, 10x12 PSP plates, exposure parameters of 75 Kvp, 8 mas, 13 sec, and KODAK CR 7400 digitizer. Master View 3.0 software was used on the desktop computer to measure the mandibular ramus's width and thickness. Maximum ramus breadth, Maximum Ramus height and lowest ramus breadth of the mandibular rami, as well as the height of the condyle and the coronoid bone, and the length of the mandibular body and gonial angles on the right and left sides of the mouth, were all measured. Using a statistical formula, the measurements were substituted and gender was estimated. Result: We used the IBM SPSS v 21.0 statistical software for social sciences to do our statistical study. p0.05 was deemed statistically significant, with a 5% margin of error and a 20% margin of error, giving the study an 80 percent power. In the study group, 51 of the 55 men were expected to be males, while 49 of the 55 females were anticipated to be females, while 6 of the 55 females were predicted to be males. Conclusion: This research shows that the mandibular ramus is a useful tool for determining gender, and digital panoramic imaging yielded the best accurate linear measures. There was considerable sexual dimorphism in the mandibular ramus in the chosen Navi – Mumbai subpopulation, and the combination of 8 factors demonstrated an accuracy of 91.81 percent and was helpful for gender determination.

AN ANATOMICAL STUDY OF HUMAN MANDIBLE IN DETERMINATION OF SEX BY USING VARIOUS MORPHOLOGICAL AND MORPHOMETRIC PARAMETRES

Determination of sex from unknown human mandible has an important role in forensic eld in relevance with Medicolegal issues to trace victim. Aim: To determine the sex of human mandible by using various morphological & morphometric data. Materials and methods: The study was conducted on 82 dry human mandibles of unknown sex. Based on morphological features the mandibles are grouped into Male (50) and Female (32) bones and the following morphometric parameters are taken for further statistical analysis. 1) Symphyseal height 2) Ramus height (Rt) 3) Ramus height (Lt) 4) Bimental width 5) Inter premolar width 6) Inter molar width 7) Bicoronoid width. Results: There was a statistically signicant difference found in the height of ramus (right), with mean value of 54.84 ± 4.5mm for males and 50.56 ± 5.4mm for females (P < 0.05), height of ramus (left) with mean value of 53.24 ± 4.3mm in males and 49.81 ± 5.03mm in females (P < 0.05) and bimental width with mean value of 42.96 ± 2.6mm in males and 41.58 ± 1.8mm in females (P < 0.05), whereas no signicant difference was found in symphyseal height, bicoronoid width, inter premolar width and inter molar width of male and female mandibles. The parameters used in this study gave an overall 76.8% accuracy in determining the sex of the mandible. Conclusion: Out of 7 parameters taken into account the interesting observation is that 3 parameters are most reliable and dependable for determination of sex. Out of these, 2 parameters have given most sensitive data and high accuracy rate for the determination of the gender.

Anatomical characteristics of mandibular bone in skeletal Class I, II and III patients by using cone beam computed tomography images in an iranian population

Objetive: This study aimed to compare the anatomical characteristics of the mandible in patients with skeletal class I, II and class III disorders using cone beam computed tomography (CBCT). Material and Methods: CBCT scans of patients between 17 to 40 years taken with NewTom 3G CBCT system with 12-inch field of view (FOV) were selected from the archive. Lateral cephalograms were obtained from CBCT scans of patients, and type of skeletal malocclusion was determined (Class I, II or III). All CBCT scans were evaluated in the sagittal, coronal and axial planes using the N.N.T viewer software. Results: The ramus height and distance from the mandibular foramen to the sigmoid notch in class II patients were significantly different from those in skeletal class I (P < 0.005). Distance from the mandibular canal to the anterior border of ramus in class III individuals was significantly different from that in skeletal class I individuals (P < .005). Conclusion: Length of the body of mandible in skeletal class I was significantly different from that in skeletal class II and III patients. Also, ramus height in skeletal class I was significantly different from that in skeletal class II patients. CBCT had high efficacy for accurate identification of anatomical landmarks. Keywords Prognathism; Retrognathism; Mandible; Anatomy; Cone beam computed tomography.

Posterior Mandibular Displacement. A Systematic Review Based on Animal Studies

Treating extreme mandibular growth is challenging. The mandible is pushed backwards to address itsprotrusion. Nevertheless, conclusions after such displacement in animals have been contradictory. The aim of the present review is to present measurable alterations of the mandible and the condyle following retractionin healthy rats or rabbits. PubMed, Scopus and Web of Science were accessed for relevant studies up to October 2020. Eligibility was determined by the PICOS process, while the risk of bias was estimated with SYRCLE’s risk of bias tool. Retraction resulted in a more distal molar occlusion and the condyle rested more posteriorly. Mandibular anteroposterior bilateral growth restriction was achieved, the condylar process measured smaller and its angulation increased. The condylar neck thickened, its posterior surface flattened, the coronoid process was measured longer, and enlarged retromolar density was registered. Differences in the ramus height and the intercondylar distance were insignificant. Changes persisted for the period of study and subsequently the mandible resumed its inherited growth pattern. The timing of mandibular shaping and TMJ outcomes might depend on the properties of the applied force. Stability is of concern and well-structured, long-term studies are expected to resolve the issue and further clarify the results of posterior mandibular displacement.

Symptoms, disc position, occluding pairs, and facial skeletal characteristics of older patients with temporomandibular disorders

Objective To describe the proportions of different osseous diagnoses in older patients with temporomandibular disorders (TMD) and to analyze the symptoms, disc position, occluding pairs, and facial skeletal characteristics of patients with bilateral osteoarthrosis (BOA) and bilateral normal joints (BNJ). Methods This retrospective cross-sectional study constituted 88 older patients (age ≥60 years). The osseous diagnosis, symptoms, disc position, occluding pairs, and facial skeletal characteristics were evaluated. Variables in BOA patients and BNJ patients were compared using the t-test and chi-square test. Results Forty-eight patients had BOA, 7 had unilateral osteoarthrosis, 11 had intermediate osteoarthrosis, and 22 had BNJ. The prevalence of disc displacement without reduction (DDw/oR) in BOA patients was significantly higher than in BNJ patients. BOA patients exhibited greater ANB angle, PP-MP, U1-NPo, L1-NPo, and facial convexity angle; shorter posterior cranial base; and decreased ramus height. Conclusion BOA patients with associated DDw/oR had more complaints of orofacial pain and exhibited a shorter posterior cranial base, and greater mandibular retrusion, anterior tooth protrusion, and protruded profile than BNJ patients.

Comparison between antegonial notch depth, symphysis morphology and ramus morphology among different growth patterns in skeletal class I and class II subjects

In orthodontics and dentofacial orthopaedics, a thorough knowledge of growth and development is essential in order to understand various factors that contribute as to how a particular type of growth takes place. When planning of orthodontic treatment for a malocclusion, one has to take into account the growth pattern, because it would considerably affect the success of the treatment. The purpose of this study was to compare antegonial notch depth, symphysis morphology, and ramus morphology in different growth patterns in skeletal class I and class II subjects. In this study, a total of 60 cephalograms were taken which comprised 30 cephalograms in skeletal class I and 30 cephalograms of skeletal class II patients. The groups were further divided into three groups, namely average, horizontal, and vertical growth patterns based on Jarabak’s ratio. Antegonial notch depth, symphysis width and symphysis angle, and ramus height were measured and compared between the growth patterns and between class I and class II skeletal patterns. An analysis of variance (ANOVA) test was performed to determine the comparison between groups for all these variables in both skeletal class I and class II. Independent 't' test was done to determine the comparison between skeletal class I and class II subjects for all variables. Mean and SD values for all variables were determined for all the groups. Depth of antegonial notch was found to be greater in vertical growth patterns compared to horizontal and average growth patterns. Large symphysis angle and symphysis width were noted in a horizontal growth pattern. Increased ramus height was noted in horizontal and average growth patterns. There was no significant difference between skeletal class I and class II malocclusion for all parameters.