Morphological and Morphometric Analysis of Gonial Angle with Reference to Lingula in South Indian Mandibles

Introduction: Gonial angle is located at the junction of lower border and posterior region of mandible. Lingula is a bony projection which provides attachment for sphenomandibular ligament and is superior to mandibular foramen. The purpose of this study was to research the gonial angle in reference to the position of the lingula helps to guide the oral surgeons to stop injury to inferior alveolar nerve and peripheral blood vessels during surgeries. Materials and Methods: The distance from the gonial angle to the tip of the lingula and the gonial angle to the base of the lingula on both right and left sides of the mandible was measured using a protractor. The values are calculated from gonial angle with reference to lingula on both sides. The obtained values of both sides were correlated using descriptive statistical analysis and by applying paired t-test. p<0.05 was considered statistically significant for this study. Results: The mean value for right gonial angle to base of lingula is 26.54 mm ± 3.30 mm and the left gonial angle to base of lingula is 25.59 ± 0.56 mm. The right gonial angle to lingula tip is 33.25 ± 2.65 and the left gonial angle to lingula tip is 32.83 ± 1.36mm. The mean gonial angle on the right side is 88.60° and on the left side it is 89.40°. Original Research Article Venkatakarthikeswari and Mohanraj; JPRI, 33(63A): 49-54, 2021; Article no.JPRI.78880 50 Conclusion: It was found that there was no correlation between the right and left side gonial angle to mandibular lingula since the mandibular angle, was measured within the group of unknown sex of dry human mandible.


INTRODUCTION
The lingula attached to sphenomandibular ligament plays an important role in protecting the nerves and blood vessels during mandibular movements and prevent overstretching during rapid opening and closing moments of mouth moments. Anatomical studies proved that more mandibular branches are located in the lingular region (1). Mandible pays an important role in identification the sex of unknown individuals. Sexual dimorphism is reflected in its size and shape of the mandibular region (2). Lingula is also called as spix spine is a ridge on medial surface of ramus region of mandible and also acts an important bony landmark for giving injection of local anaesthetics agent in dentistry or for excision of nerve for facial neuralgia (3).
Gonial angle is important in orthodontic research for study about changes during the developmental period. It shows the growth and direction of condyles in a gonial angle (4). In forensic studies and anthropology, using bony remnants they diagnosis the age and sex of every unknowm individuals.
The mandible is sexually dimorphic and shows changes in growth and sex between male and females (5)). The ramus bears both coronoid and Condyloid processes and mandibular mostly help in developing the musculoskeletal system, mainly the muscles which help in mastication attached with the mandible (6). Mandible is the last skull bone to end growth and sensitive to adolescent growth (6,7). In both male and female stages the development of the mandible is different and also in their masticatory forces of the mandible also seems to be different (8).
Lingula is also an important landmark for inferior alveolar nerve block anaesthesia and different maxillofacial surgeries which are mostly done by dentists. Lingula helps to find the location of mandibular foramen in the mandibular region (9). Location of mandibular foramen was measured in horizontal and vertical distances. Horizontal distance is from mandibular foramen to anterior region of ramus and vertical distance is from mandibular foramen to occlusal plane of dentition (10). Remodeling is concerned with changes in gonial angle with aging in dentulous (possesses teeth) and edentulous (Losing teeth) (10,11). Nicholson and Keros, analyzed the morphology of the mandibular foramen and lingula and on which they concluded that structures variability would account for failure to dam the inferior alveolar nerve (12). Our team has extensive knowledge and research experience that has translated into high quality publications (13)(14)(15)(16)(17)(18)(19)(20), (21), (22), (23), (24,25), (26), (27), (28)(29)(30)(31)(32). The aim of this study was to determine the difference between right side and left side of lingula with reference to gonial angle in dry human mandibles.

MATERIALS AND METHODS
The study was performed in 53 dry human mandible of unknown sex and without any abnormality were collected from department of anatomy, saveetha dental college and hospitals, chennai. Mandibles which are damaged were excluded from the study. This study is SRB approved. Investigator and principal investigator are the people involved in this study. All the data were statistically analysed in SPSS version 23, paired sample 't' test. p<0.05 was considered statistically significant for this study.

RESULTS
The morphometric observations measured were noted and analysed. The right gonial angle to lingula base mean value was 26.5 ± 3.30mm and the left gonial angle to lingula base mean value was 25.59 ± 0.56mm. The right gonial angle to lingula tip mean value was 33.25 ± 2.64mm and the left gonial angle to lingula tip mean value was 32.83 ± 1.36mm (Table 1). The angle of the right gonial angle and lingula base was 88° and the left gonial angle and lingula base was 89°.
The gonial angle to lingula base value was not statistically significant (p<0.05) and there was no correlation between the right with left side ( Table 2). The gonial angle to lingula tip was not statistically significant (p<0.05) and there was no correlation between the right and left side. The mean gonial angle on the right side was 88.60° and on the left side it was 89.40°. From these results it is understood that the right and left sides of mandibles are similar and both are statistically not significant. The lingula and the gonial angle on the right and left side of the mandible was shown in Figure 1.  Table 2: Shows the morphometric measurements of the correlation of right and left gonial angle to lingula base length (mm) and the mean gonial angle between the right and left side (degree).
Both the gonial angle to lingula base value and gonial angle to lingula tip was not statistically significant (p<0.05) and there was no correlation between the right and left side.

Parameters Correlation Significant
Right According to Nova, sex determination is not only for forensic studies but also for population history and variations.They proves that no significant analysis between right and left side of mandible, in angular and linear measurements. In their study of gonial angles they prove that male show significantly lower mean values than females and also females have downward and backward rotation and male have forward rotation in mandible (8). According to Srimani, Lingula is the most important anatomical structure which helps in facial surgeries like intraoral verticalsagittal ramus osteotomy and sagittal split Ramus osteotomy etc. The anatomical lingular region which localizes the mandibular foramen and helps in surgeries (9).
Limitation: The present study was conducted in a short span of time. If more dry human mandibles were used, more significant results would have been obtained.

CONCLUSION
The present study gives knowledge of the position of gonial angle with reference to lingula. This data has great clinical relevance, since it can be used as a parameter to carry out surgical procedures performed in the lingula region or inferior alveolar nerve block. It can be concluded from the study that there is no correlation between the gonial angle and the position of lingula.