Mean Gonial Angle Research Articles

The Influence of the Mandibular Gonial Angle on the Incidence of Mandibular Angle Fracture—A Radiomorphometric Study

The aim of this radiomorphometric study was to analyze the association between the mandibular gonial angle and the risk of mandibular angle fracture. A retrospective analysis of medical records and radiographs of patients treated for mandibular fractures was performed. The exposure studied was the presence of a high gonial angle and the outcome was fracture of the mandibular angle. The mandibular gonial angle and mandibular height at the angle were measured using Facad software (Ilexis AB, Linköping, Sweden). Data obtained were analyzed using SPSS 16 (IBM Corp, Armonk, NY). The study sample was comprised of 210 mandibular fractures (70 mandibular angle fractures and 140 non-angle fractures). The mean gonial angle in patients with mandibular angle fractures was 126.8 ± 7.9°, which was 4.5° larger than in patients with other mandibular fractures (P= .0001). Patients with a high gonial angle were 11.77 times more likely to sustain an angle fracture than those with normal or low gonial angles (adjusted odds ratio= 11.77; 95% confidence interval, 3.65-37.94; P < .001). There also was a statistically significant decrease in mandibular height at the angle in patients with a high gonial angle (P= .0001). This study shows that people with a high gonial angle are at an increased risk for angle fracture and presents the related clinical implications.

Reliability of panoramic radiography in assessing gonial angle compared to lateral cephalogram in adult patients with Class I malocclusion

Introduction: Gonial angle is an important angle of the craniofacial complex. Lateral cephalogram and orthopantomogram (OPG) can be used to determine this angle. Objectives: To investigate whether OPGs can be used as an alternative to lateral cephalogram for measuring the gonial angle. Study Design: A total of 100 radiographs were collected from patients with Angle's Class I malocclusion (50 males and 50 females) with age ranging from 15 to 30 years, with a mean age of 18.24 years. Materials and Methods: The radiographs were taken with digital panoramic system (Kodak 8000C) under standard exposure factors, as recommended by the manufacturer. Gonial angle was determined by the tangent of the inferior border of the mandible and the most distal aspect of the ascending ramus and condyle on both panoramic and cephalometric radiographs. Statistical Analysis: Mean values were evaluated using z test. The statistical analysis was performed by using the Statistical Package for the Social Sciences (version 11.5). Results: The mean gonial angle was 121.13° and 122.22° on panoramic and cephalometric radiographs, respectively. There was no statistical significant difference between the measured gonial angles on panoramic and cephalometric radiographs (P > 0.005). Conclusion: Panoramic radiography can be used to determine the gonial angle as accurately as lateral cephalogram. In addition, we can determine the right and left gonial angles of a patient in an OPG without interferences due to superimposed images of anatomical structures in lateral cephalogram.

Mandibular Ramus and Gonial Angle Measurements as Predictors of Sex and Age in an Egyptian Population Sample: A Digital Panoramic Study

Objective: The determination of sex and age is necessary in forensic practice and medico legal purposes. Mandible may play a vital role in sex estimation as it is the most dimorphic bone of skull that often recovered intact. In this respect, the availability of plentiful antemortem orthopantomograms may be of great value in studying and developing population specific standards for accurate sex and age estimation. Therefore, the purpose of the current study was to assess the usefulness of various mandibular ramus linear and gonial angle measurements on digital panoramic images as indicators for sex and age in an Egyptian population sample. Methods: 191 panoramic images (105 males and 86 females) of Egyptian patients aged (6-70) years old were selected. Five mandibular ramus linear measurements (upper ramus breadth, lower ramus breadth, projective height,condylar ramus height and coronoid ramus height) and gonial angle measurements were performed bilaterally resulting in a total of 382 rami being assessed. Stepwise discriminant and regression analyses were performed to determine the most significant predictors of sex and age respectively. Results: Males showed statistically significant higher mean linear ramus measurements and lower mean gonial angle values than females. Condylar and coronoid ramus heights were the most significant predictors for sex and age respectively. The discriminate function equation was: (D= 14.698 - 1.895 Condylar ramus height) with an accuracy of 81% in males and 77.9% in females and an overall accuracy of 79.6%. The regression equation for age estimation in the whole studied sample was: (Age= - 32.306 + 8.481 Coronoid ramus height) that yields no significance on comparing actual and estimated ages. Conclusion: In the selected Egyptian population sample, the mandibular ramus showed a high sexual dimorphism and proved to be beneficial in sex and age estimation; while, the gonial angle could assist in sex estimation only.

Influence of Age on the Radiomorphometric Indices of the Gonial Region of Mandible in North-Indian Population

Background: The gonial region of mandible plays a significant role in the determination of mandibular basal bone morphology. Gonial Angle is important for maintenance of a harmonius facial profile whereas Gonial Index is an indicator of the bone quality of the mandibular gonial region. Objectives: To examine the influence of age on two quantitative radiomorphometric indices of mandible, Gonial Angle (GA) and Gonial Index (GI) in a group of North-Indian population. Material and Methods: 60 adult human orthopantomographs were evaluated and divided into six age groups (35-65 years) with equal number of cases. Gonial Angle and Gonial Index were measured bilaterally on each radiograph. The measurements were analyzed for interactions with age and other interrelationships between the indices. The data obtained was subjected to statistical analysis using SPSS (Statistical Package for Social Studies) software version No. 18 and Mann- Whitney tests were used for various comparisons. Results: Gonial angle showed a significant positive correlation with age as the mean gonial angle values showed an increase with increasing age. Whereas in sharp contrast to this, gonial index showed no correlation with age as the mean gonial index values showed no pattern of either increase or decrease with increase in age. The correlation between gonial angle and gonial index was statistically insignificant (p>0.05). Conclusion: Age had a significant influence on the angular radiomorphometric index i.e. gonial angle but the linear radiomorphometric index i.e. gonial index remained independent of age.

Agreement Between Panoramic and Lateral Cephalometric Radiographs for Measuring the Gonial Angle

BackgroundThe gonial angle is one of the most important measurements required for orthodontic treatment and orthognathic surgery. It is difficult to determine the accurate measurement of each gonial angle on cephalometric radiographs because of superimposition of the left and right angles.ObjectivesThe aim of the present study was to determine the right and left gonial angles on panoramic radiographs and to compare them with an evaluated cephalometric sample.Patients and MethodsA total of 80 panoramic and 80 cephalometric radiographs were obtained from 6 to 12-year-old children and the gonial angle was determined by the tangent of the inferior border of the mandible and the most distal aspect of the ascending ramus and the condyleon both panoramic and cephalometric radiographs. We used Pearson’s correlation coefficient and paired t-test for comparison.ResultsThe mean gonial angle was 127.07 ± 6.10 and 127.5 ± 6.67 degrees on panoramic and cephalometric radiographs, respectively. There was no statistically significant difference between the measured gonial angles on panoramic and cephalometric radiographs and also no difference between the right and left (both Ps = 0.18)ConclusionThe value of the gonial angle measured on panoramic radiography was the same as that measured on the routinely used cephalometric radiography.

Molecular weight distribution of denture base acrylic

Statement of problem: The gonial angle plays an important role in ensuring a harmonious facial profile. Changes in this angle especially after surgery may be an aesthetic concern for both the patient and the surgeon. Purpose: The aim of the present study was to evaluate gonial angle changes after mandiblular setback with the BSSRO technique and to measure postsurgical relapse two years after surgery. Material and Methods: Nineteen patients with mandibular prognathism referred to Taleghani Hospital were selected from 1999 to 2001. All subjects underwent surgery for mandibular setback with the BSSRO technique and IMF for 8 weeks. Lateral cephalograms were taken before surgery, immediately postoperatively and 2–4 years after surgery. The setback rate (relapse) and gonial angle changes were evaluated during these periods. Pearson correlation and student t tests were used for statistical analysis. Results: The mean gonial angle decreased in all subjects, it was 135.05° (6.41) before and 128.73° (5.43) after surgery. The mean reduction of the gonial angle was 6.32° (4.08) immediately after surgery while it showed 4.89° (3.44) decrease after 2 years follow-up at the final examination. The mean of setback was 6.27 (2.28) mm which decreased to 5.82 (1.82) mm after follow-up. A significant correlation was observed between the amount of setback and reduction of the gonial angle (P=0.0001) but no correlation was found between sex and gonial angle changes or mandibular setback relapse. Conclusion: Surgical correction of mandibular prognatism using BSSRO and IMF can cause a decrease in the gonial angle. This increase in the setback, may reduce the gonial angle and have correlation to the amount of relapse.