Association of gonial angle with morphology and bone mineral content of the body of the adult human mandible with complete permanent dentition

Age estimation from mandibles in Malay: A 2D geometric morphometric analysis

Objectives

In this study, the sizes and forms of mandibles in various age groups of the Malay population were measured and compared.

Methods

Geometric morphometric (GM) analysis of mandibles from 400 dental panoramic tomography (DPT) specimens was conducted. The MorphoJ program was used to perform generalized Procrustes analysis (GPA), Procrustes ANOVA, principal component analysis (PCA), discriminant function analysis (DFA), and canonical variate analysis (CVA). In the tpsDig2 program, the 27 landmarks were applied to the DPT radiographs. Variations in mandibular size and form were categorized into four age groups: group 1 (15-24 years), group 2 (25-34 years), group 3 (35-44 years), and group 4 (45-54 years).

Results

The diversity in mandibular shape among the first eight principal components was 81%. Procrustes ANOVA revealed significant shape differences (P < 0.001) among age groups. Mahalanobis distances indicated substantial differences among all age groups; group 1 and group 4 scored highest, at 2.114. The ranges for the cross-validation and discriminant function tests were 90-72% and 81-49%, respectively.

Conclusion

GM analysis through radiography is a simple, non-invasive, and non-destructive method of estimating age by using the mandible. GM analysis is unique because it can visualize the changes in mandible shape among age groups. This method should aid in age identification in forensic odontology investigations.

Is the distribution of cortical bone in the mandibular corpus and symphysis linked to loading environment in modern humans? A systematic review

OBJECTIVE

The human mandible is a unique bone with specific external and internal morphological characteristics, influenced by a complex and challenging loading environment. Mandibular cortical thickness distribution in cross-sections is reported to be related to facial divergence patterns, cultural and dietary habits and more generally, specific loading environment. This review hypothesises that a process of environmental mechanical sensitivity is involved in the distribution of cortical bone in the mandibular corpus and symphysis in modern humans, and that loading regimes can influence this distribution pattern. Based on a review of the recent literature, this study aims to answer the following question: "Is the distribution of cortical bone in the mandibular corpus and symphysis linked to the loading environment in modern humans?"

DESIGN

A systematic review was undertaken using the PubMed/Medline, Scopus and Cochrane Library databases for publications from 1984 to 2022 investigating the relationship between cortical bone distribution in the mandibular corpus and the loading environment. A subgroup meta-analysis was performed to determine the overall effect of facial divergence on cortical thickness.

RESULTS

From a total of 2791 studies, 20 fulfilled the inclusion criteria. The meta-analyses were performed in eight studies using a randomised model, finding a significant overall effect of facial divergence on cortical thickness in posterior areas of the mandible (p < 0.01).

CONCLUSIONS

Within the limitations of this review, specific loading regimes and their consequent variables (diet, culture, facial divergence) were linked to cortical thickness distribution. Sex was found to be unrelated to cortical thickness pattern.

Magnitude of Gonial Angle Influence on the Commonness of Mandibular Angle Fractures

Background:

The aim of the study was to review the literature on the influence of gonial angle on mandibular angle fracture. The present systematic review addresses the following focus question: Does the magnitude of gonial angle influence the incidence of mandibular angle fractures?

Materials and Methods:

Electronic and manual literature searches were conducted on databases: PubMed/MEDLINE, Embase, Science direct, the Cochrane Library, and clinicaltrials.gov for studies published up to August 2019 to collect information about the effect of gonial angle, a skeletal morphological parameter with an incidence of fracture of the angle of the mandibular arch. Systematic literature review was performed to identify studies evaluating the effect of gonial angle in patients suffering from mandible fractures. Large retrospective studies were included and case reports were excluded.

Results:

Fifteen hundred articles published before August 2019 were identified. One hundred and sixteen articles met the inclusion criteria. Two articles remained when exclusion criteria were applied. As measured in the two included studies containing 280 panoramic radiographs of mandibular fractures, the mean gonial angle of patients in the angle fracture group ranged from 126.8° ± 7.9° to 128.5° ± 5.4°. The mean gonial angle of patients in the nonangle fracture group ranged from 118.5° ± 4.4° to 122.3° ± 4.9°. The mean gonial angle of patients in the angle fracture group displayed a range from 118.9° to 134.7° (confidence interval [CI] 95% 5.89–8.05), whereas the mean gonial angle of patients in nonangle fracture group displayed a range from 114.1° to 127.2° (CI 95% 3.89–4.95).

Conclusion:

A high gonial angle is an important factor influencing the occurrence of mandibular angle fractures owing to the poorer quality of bone and reduced height at the ramus angle region, all of which necessitate a modification of osteosynthesis techniques.

The influence of the mandibular gonial angle on the occurrence of mandibular angle fracture

BACKGROUND/AIMS

Angle fractures represent the largest percentage of mandibular fractures. They pose as a unique entity because of their codependent morphological dynamic factors, rendering the understanding of the mechanism, and treatment challenging. The aim of this study was to analyze the association between the mandibular gonial angle and the risk of mandibular angle fracture while highlighting its clinical relevance.

MATERIALS AND METHODS

A retrospective analysis of radiographs of patients treated for mandibular fractures was done. The factors studied were as follows: the presence of a high gonial angle and an impacted third molar. The outcome was mandibular angle fracture. The gonial angle was measured using Planmeca Digital Software 3.7.0.R. Status of the third molar was also noted. Data obtained were analyzed using SPSS 22 (IBM Corp, Armonk, NY).

RESULTS

The sample comprised 70 mandibular fractures (32 angle fractures and 38 non-angle fractures). The mean gonial angle in the angle fracture group was 128.5 ± 5.4º which was 10.2° larger than in the non-angle group (mean 118.5 ± 4.4º; P = 0.0001). Patients with a high gonial angle were 8.7 times more likely to sustain an angle fracture than those with normal or low gonial angles. A statistically significant relationship between the presence of impacted third molar and patients sustaining mandibular angle fractures was noted (P = 0.0001).

CONCLUSION

Subjects with a high gonial angle and an impacted third molar are at an increased risk for mandibular angle fracture due to direct and indirect morphological factors.

Comparative analysis of the gonial angle on lateral cephalometric radiographs and panoramic radiographs

We measured the gonial angle (GA) on panoramic radiography (PR) and analyzed the correlation between the GA on PR and lateral cephalometric radiography (LCR). In total, 49 PR films and LCR films from dentate young adults were evaluated. Orthodontists plotted four points (articulare, menton, posterior gonion, and lower gonion) on the PR and carefully traced them. Using a protractor, two radiologists measured the GA on LCR images. A simultaneous experimental study of two dry skulls was performed to compare the GA on LCR and PR. The GA was slightly smaller on the PR of the dry mandible than on the LCR and tended to decrease continuously with magnitude toward the Frankfort horizontal plane. The mean GA was 115.1 ± 5.2° on PR and 122.2 ± 6.4° on the LCR. The values were highly correlated (Pearson product-moment correlation coefficient, 0.801). The GA on PR was nonsignificantly smaller than that measured on LCR. The difference may be due to head position, the inclination angle of the mandibular body, and/or the direction of the incident X-ray beam.

Centric slide in different Angle's classes of occlusion

The purpose of this study was to test the possible differences in centric slide values between different Angle's classes of occlusion. The study included 98 participants divided into four groups: Angle's class I, Angle's class II, subdivision 1, Angle's class II, subdivision 2 and Angle's class III. All recordings were obtained using an ultrasound jaw tracking device with six degrees of freedom. The distance between the maximum intercuspation (reference position) and the centric occlusion was recorded at the condylar level. Anteroposterior, superoinferior and transversal distance of the centric slide were calculated for each participant, and the data were statistically analyzed (analysis of variance and Newman-Keuls post hoc test). No statistically significant difference was found in the anteroposterior and transversal distance of the centric slide between tested groups, while Angle's class II, subdivision 2 showed smaller vertical amount of the centric slide compared to Angle's class I and class II, subdivision 1. None of the 98 participants showed coincidence of centric occlusion and maximum intercuspation. Our results suggest that coincidence of the maximum intercuspation with the centric occlusion should not be expected. Smaller extent of the vertical distance of the centric slide could be morphological and a functional expression characteristic of the Angle's class II, subdivision 2.

The evaluation of MCI, MI, PMI and GT on both genders with different age and dental status

OBJECTIVES

The aim of this study was to measure the mandibular cortical index (MCI), mental index (MI), panoramic mandibular index (PMI) and cortical bone thickness in the zone of the gonial angle (GT) in panoramic radiographies from a large sample of males and females and to determine how they relate to patients' age, gender and dental status.

METHODS

910 panoramic radiographs were obtained and grouped into age, dental status and gender. The MCI, MI, PMI and GT were analysed.

RESULTS

Remarkable differences were observed for MCI and GT regarding gender, age groups and dental status on both sides (p < 0.05). While age and dental status had an effect on the MI and PMI in females, dental status had an effect on the MI and PMI in males (p < 0.05). Also, gender had an effect on the MI and PMI (p < 0.05).

CONCLUSIONS

The effects of age and tooth loss are different in females and males. In females, the harmful effects of tooth loss and age are more prominent according to the PMI and MI measurements. The effects of age and tooth loss in the GT and MCI measurements are similar, and these indices can be accepted as more reliable in studies including both genders.