European Journal of Cardiovascular Medicine

The mandible is included in facial bones. The mandible is the strongest bone in the human face and is also called the jawbone. It is the only movable bone of the skull (excluding ear ossicles). The word “mandible” is derived from the Latin term “mandibula” (used for chewing). The mandible consists of a body and a ramus which runs downwards from each side thus forming the gonial angle of the mandible.

Identification of human remains is the crux of medicolegal practice. The mandible, unlike any other bone in the face, has managed to draw the interest of many forensic odontologists owing to multiple muscle attachments, their usage and thus giving the mandible a unique angle to every human being. Apart from just muscle attachments, a lot has seemed to influence the grooves, surfaces, edges, and the angle of this bone.

While multiple researches seem to have focused on various aspects of this bone, research on the angle of the mandible - Gonial angle, has gained lesser attention. Interestingly, the parameters of the Gonial angle can guide us for better assessment of age and gender and also in the identification process done by forensic experts. It can also be used as a tool in age assessment in extreme situations like mass disaster, remains of human dead exhumed and murderous mutilations, missing individuals, etc. (in short, it is very useful and crucial when it comes to the process of identification). This angle varies from person to person. With age and the amount or type of usage of the function of the mandible, the angle has shown changes in size, shape and also in the origin and insertion of the muscles and thus variation in mandibular angle with age, gender, and even the dental status has been observed, which is supported by radiographic and anthropometric studies.[1]

A total of 105 living subjects have been included in the study as per the criteria stated below:

• All the subjects chosen were residents of Ahmedabad, Gujarat.
• Both males and females have been included in this study.
• The age of the subjects ranges from 10 years to 92 years of age.
• Edentulous and dentulous subjects have been included.
• All the subjects belonged to a high socioeconomic background.

Exclusion Criteria:

• The subjects who had fixed dentures.

From 105 subjects, 56 were females and 49 were males. The subjects have been divided into five groups on the basis of chronological age (1 – 20 years, 21-40 years…). The data is analyzed in the following manner: Physico-forensic anthropometry: Here, the gonial angle was measured as the angle formed by the base of the mandible and posterior border with the help of a protractor, which is placed over the angle of the mandible in such a way that the basic line or base of the protractor coincides with the base of the mandible. The angle is recorded in degrees. [2] Thus, with the help of a protractor and a scale, the angles were measured. The gonial angle was measured for each by two separate observers, each angle measured three times, with the mean taken as the final record. Insignificant variability was observed between the left and right sides on physico-forensic anthropometry, and for uniformity, the left side of the mandible was measured.

Observation

Comparisonofmeanangleofmandiblebetweendifferentagegroupsinmalesandfemalesindividually:

As the age of the males increases from paediatric age to adulthood, the gonial angle is seen to be decreasing, but from middle age (41-60 years) the angle is again increasing, and in old age (80+ years) it is reaching its highest value.

As the age of the females increases from paediatric age to adulthood, the gonial angle is seen to be decreasing, but from middle age (41-60 years) the angle is again increasing, and in old age (80+ years) it is reaching its highest value.

Comparison of angle of mandibles between male and female subjects:

From the graph given above, we can make out that the angle in females is somewhat higher than that of males in most of the age groups.

Comparison of angle of mandible with the dental status of the subjects:

First bar determines the angle in dentulous subjects. Second bar indicates the angle in edentulous subjects wearing dentures. Third bar indicates the angle in edentulous subjects who do not wear dentures.

From the above graph, we can make out that the angle of mandible is maximum in edentulous subjects, intermediate in edentulous subjects wearing dentures, and least for dentulous subjects.

From the study of 105 subjects that we have analyzed, we can observe a definite pattern in the above given graphs. As indicated in the graphs above, we can observe the angle is more in females in most of the cases but yet the mean angle is varying. Also, in males and females both, there is a significant decline in the degrees of the angle in middle age but then it is increasing again to its highest value in old age.

The gonial angle is actually found to be varying with age, gender, and dental status of an individual. There were a total of 56 female subjects whose average angle measured 121.35 degrees and the average of 49 male subjects was 109.10 degrees. If we look at the graph which shows comparison in angles of males and females individually with age, we can say the angle decreased initially from 127.9375 to 113.8235 in females and 120.2222 to 115.8333 in males from age group 1 to 20 years to 41 to 60 years. In the last graph, we can make out the average angle is highest in edentulous people who avoid wearing dentures i.e., 136 degrees, it is intermediate in edentulous subjects who wear dentures i.e., 130 degrees and is found least in subjects who are dentulous i.e., 119.2 degrees.

As per a research conducted before, the gonial angle of the mandible and the mandibular and condylar height were measured using panoramic radiographs. In edentulous subjects, the gonial angle was significantly larger, while the ramus and condylar height were significantly smaller on both sides compared with dentulous subjects. Women had a significantly larger gonial angle and smaller ramus and condylar height on both sides compared with men. In conclusion, the morphology of the mandible changes as a consequence of tooth loss, which can be expressed as a widening of the gonial angle and shortening of the ramus and condylar height. These findings highlight the importance of rehabilitation of the masticatory system to maintain good functioning of the masticatory muscles for as long as possible. [2] As per this research, the results are the same but the methodology used is more accurate. Due to lack of resources, my research fails to be as accurate and precise. Another research conducted priorly states: Preliminary results of the analysis (ANOVA) showed that the number of teeth had a decisive influence on the size of the gonial angle. The correlation coefficients between size of the gonial angle and age showed that age explained approximately 8–16% of the variation of the angle through its relation with age. Sex differences in age and size of the gonial angle were not statistically significant in any of the three tooth retention categories. [3] On the contrary, Sir P. Lonberg concluded that the angle actually decreases in edentulous subjects. [4] A study conducted in India itself has found no significant relation between gonial angle and gender of a person. [1] The fact that there is no significant relation between the gonial angle and genders is also supported by multiple studies. [5][6][7] Thus, there are multiple variations related to this study and the relation of gonial angle with sex, age, and dental status still remains hazy. Yet, the angle of mandible does serve as an important parameter when it comes to class 2 and class 3 malocclusion.

The present study concludes that gonial angle can serve as an additional forensic parameter that can guide for age group, gender, and dental status assessment of a subject. It can thus be a crucial tool for identification in cases of medicolegal cases or mass death due to natural disasters, etc. to the forensic experts.

1. Upadhyay, R. B., J. Upadhyay, P. Agrawal, and N. N. Rao. "Analysis of Gonial Angle in Relation to Age, Gender, and Dentition Status by Radiological and Anthropometric Methods." Journal of Forensic Dental Sciences, vol. 4, no. 1, Jan. 2012, pp. 29.
2. Huumonen, S., K. Sipilä, B. Haikola, M. Tapio, A. L. Söderholm, T. Remes-Lyly, K. Oikarinen, and A. M. Raustia. "Influence of Edentulousness on Gonial Angle, Ramus and Condylar Height." Journal of Oral Rehabilitation, vol. 37, no. 1, Jan. 2010, pp. 34-38.
3. Ohm, E., and J. Silness. "Size of the Mandibular Jaw Angle Related to Age, Tooth Retention and Gender." Journal of Oral Rehabilitation, vol. 26, no. 11, Nov. 1999, pp. 883-91.
4. Lonberg, P. "Changes in the Size of the Lower Jaw on Account of Age and Loss of Teeth." Acta Genetica et Statistica Medica, vol. 2, Suppl. 2, 1951, pp. 9-76.
5. Raustia, A. M., and M. A. Salonen. "Gonial Angles and Condylar and Ramus Height of the Mandible in Complete Denture Wearers—A Panoramic Radiograph Study." Journal of Oral Rehabilitation, vol. 24, no. 7, July 1997, pp. 512-16.
6. Ceylan, G., N. Yanıkoglu, A. B. Yılmaz, and Y. Ceylan. "Changes in the Mandibular Angle in the Dentulous and Edentulous States." The Journal of Prosthetic Dentistry, vol. 80, no. 6, Dec. 1998, pp. 680-84.
7. Al-Faleh, W. "Changes in the Mandibular Angle in the Dentulous and Edentulous Saudi Population." Egyptian Dental Journal, vol. 54, 2008, pp. 2367-75.