Introduction
Among the facial bones, mandible is the largest bone. Its body is horizontally curved with forward convexity. The two rami ascend posteriorly and have the coronoid and condyloid processes. The coronoid process of the mandible is a triangular plate of bone which projects upward and slightly forward. The temporalis muscle is attached to its margins and medial surface.1
Being a membranous bone, it can easily be removed intraorally without any functional deficiency and facial disfigurement. This is needed for reconstruction of orbital floor deformities, alveolar defects, paranasal sinus augmentation, non-union fractures of mandible, osseous defect reconstruction, and other repairing procedures in craniomaxillofacial surgeries.2
Many researchers have studied the morphology of coronoid process and have found varying shapes.3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 Similar study has not been done in this area. Hence, this study was conducted which will be useful to maxillofacial surgeons, forensic scientists and anthropologists.
Aims & Objectives
The present study was conducted to identify different morphological variations in shape of coronoid process of adult human mandible.
Material and Methods
Study setting
The present cross-sectional study was conducted in the department of Anatomy at a medical college of Bihar.
Study samples
The present study was conducted upon 46 dry adult human mandibles. Thus, a total of 92 coronoid processes were studied. Intact adult human mandibles available in the department were included. The mandibles which were damaged were excluded from the study.
Data collection procedure
The morphological analysis of mandibles were done to note the details of coronoid processes of both sides. Metric and nonmetric analysis were used for determination of sex of the mandible. Chin shape, gonial eversion, bigonial and bicondylar width and flexion on the posterior surface of mandible were considered for the same.
The morphological forms of coronoid process were noted. If the apex pointed straight upwards with straight anterior and posterior border, it was considered to be triangular. If the apex was blunt with straight anterior and posterior border, it was rounded. If the tip was pointing in backward direction with convex anterior and convex posterior border, it was taken as hook-shaped.
Results
The present study included a total of 92 coronoid processes of both sides from 46 mandibles. 62 of these (67.4%, 31 mandibles) were of males and 30 (32.6%, 15 mandibles) were of females.
Table 1 shows the shapes of coronoid processes. 57.6% of these were triangular in shape, 28.3% were rounded and 14.1% were hook shaped. Among the mandibles of males, 69.4% were triangular in shape, 19.4 % were rounded and 11.3% were hook shaped. Among the mandibles of females, 33.3% were triangular in shape, 46.7% were rounded and 20% were hook shaped. The difference between male and female mandibles was found to be statistically significant (p=0.004).
Discussion
The present study upon 92 coronoid processes of 46 mandibles revealed that 57.6% were triangular in shape, 28.3% were rounded and 14.1% were hook shaped. Rounded shape was more common in females. The difference between male and female mandibles was found to be statistically significant (p=0.004).
Quadri et al. (2016) observed that overall triangular type of coronoid process (67%) was more prevalent than hook shape (30%) and rounded (3%). Triangular type was more prevalent in males (72.2%) than females (51.1%), whereas hook shape was more prevalent in females (44.9%) than males (25.2%). Rounded shape was more prevalent in females (4.1%) than males (2.6).3
Sheela et al. (2015) reported that triangular shape coronoid process was found in 64.97%, hook shape in 21.02% sides and rounded in 14.01% sides of mandibles. Mean intercoronoid distance among males was found to be 9.2000 and 9.100 in females. 4
Sudha et al. also found that shapes of coronoid process were triangular (60.8%), rounded (14%) and hook (25.6%) in their study. Hook shape was found bilaterally in 28.8 %. In edentulous bone, hook type of coronoid process was found in 53.3% and there was no incidence of rounded type bilaterally.5
Sahithi et al. conducted a study of 200 digital OPG images, corresponding to 400 sides among which, 84 (168 sides) were of males and 116 (232 sides) were females. The most common shape for coronoid process was observed as triangular (215) which was distributed as 105(48.8%) on the right side and 110 (51.2%) on the left side. The next shape was found to be the round (143), of which 75 (52.4%) were on the right side and 68 (47.6%) were on the left side followed by the beak shape (34), of which 16 (47.1%) were on the right side and 18 (52.9%) on the left side. The least common shape observed for the coronoid process was flat (8), which was equally distributed on both sides. The distribution of the shapes of the coronoid process among the right and left sides had shown no statistical significance (p value = 0.90).6
Conclusion
Morphological variations of anatomic structures result from either due the developmental discrepancies through hereditary determinants or due to the functional variations that arise during the growth process. 6
The proper knowledge on the morphological shapes of coronoid process is useful for maxillofacial surgeons as it is used in reconstructions of orbital floor deformities, oromaxilla facial defects, and paranasal augmentation. Along with the other features of the skull, these could be used as an anthropological marker to assess different populations and races.
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