European Journal of Cardiovascular Medicine

The mandible is one of the strongest bones in the human body. The mandible is formed by the union of two halves at the symphysis menti. Each half of the mandible has a body and a ramus. The ramus of the mandible shows superiorly two processes, i.e., a coronoid process anteriorly and a condylar process posteriorly separated by a mandibular notch. The coronoid process is an upward projection of a piece of bone from the ramus of the mandible. The coronoid process is a Greek word that means “like a crown.” Some animals have independent coronoid bones, and they articulate with the splenial, angular, and supra-angular bones. The coronoid bone forms a common “dentary bone” similar to the mandible in human beings⁽¹⁾. The mandible receives attachment of the muscles of mastication; especially, the coronoid process receives the insertion of the temporalis muscle. The coronoid process usually does not move out of place in fractures of the mandible due to strong support from the tendinous attachment of the temporalis. Fractures of the coronoid process are not common and do not require any treatment unless there is impingement on the zygomatic arch⁽²⁾.

The size and shape of the coronoid process are determined by the genetic constitution, dietary habits, hormones, and the activity of the temporalis muscle⁽³⁾. For the bone graf procedure, various bones are used, like hip bone, calvaria, mandible, etc. The knowledge of the anatomy of the mandible, especially the morphometry of the coronoid process, is important in various branches like oro-maxillofacial surgery, cosmetology, plastic surgery, etc. In recent days the coronoid process is gaining much importance as an autogenous graft material in various aspects of the reconstructive oro-maxillofacial surgeries like paranasal augmentation, correction of the temporomandibular joint ankylosis, and orbital floor reconstruction, etc. ⁽⁴⁾. The coronoid process is commonly used to take a bone graft, as it is easily accessible with less dissection and morbidity to the patient. In the present era, in both genders, with the recent advancements in cosmetology, knowledge of various shapes of the coronoid process is becoming important for the facial contour correction and jaw correction surgeries.

The present study was conducted on 100 adult human dry mandibles, in which 68 belonged to males and 32 belonged to females. The gender of the mandible was identified by the features of non-metric analysis, like the heaviness of the mandible, muscular impressions, the shape of the chin, and the eversion of the gonion. These mandibles were collected from the Department of Anatomy, Konaseema Institute of Medical Sciences and Research Institute, Amalapuram, and the Department of Anatomy, Rangaraya Medical College, Kakinada. A total of 200 coronoid processes on both the right and left sides were studied. The mandibles with damaged or deformed coronoid processes were discarded. The shapes of mandibles were observed and recorded (fig-1). Morphometric measurements, like the average length of the base, anterior arm, posterior arm, and height of the coronoid process, were taken with the help of vernier calipers and recorded (fig-2).

For measuring the sige of the coronoid process, a point is marked on the lowest point on the mandibular notch and its distance from the base is noted. At the same height, the points ‘A’ and ‘B’ are marked on the anterior and the posterior border of the coronoid process respectively. A point ‘C’ is marked on top of the coronoid process. The points A, B and C are joined to form a triangle where AB represents the Base, AC represents the anterior arm and BC represents the posterior arm of the coronoid process. A perpendicular line is drawn from point ‘C’ to meet the base AB at ‘D’. The line CD represents the height of the coronoid process. The lengths of various parameters were measured in millimeters, photographed, and tabulated according to the side and gender. The present study is compared with the standard literature and studies done by other authors.

The present study includes 100 mandibles. Out of which 68 belonged to males and 32 belonged to females.  A total of 200 coronoid processes, of which 100 were on the right side and 100 were on the left side were studied. Depending on various parameters, the shapes of coronoid processes were broadly classified under three shapes: triangular, hood shape, and round (fig - 1) and recorded in table – I. Measurement of mean length of each arm of triangle (fig - 2) in millimeters of right coronoid process in both genders were recorded in table – II and measurement of mean length of each arm of triangle (fig -2) in millimeters of left coronoid process in both genders were recorded in table – III.

Figure 1 : Various shapes of the coronoid process

Figure 2 : Measurement of mean length of the base, height, anterior and posterior arms of the coronoid process

The mandible is a separate bone in the facial skeleton and a strong bone. It is formed by the membrano-cartilaginous ossification. The ramus of the mandible has two bony projections, the coronoid process and the condylar process. The condylar process is involved in the formation of the temporomandibular joint, and the coronoid process is free and gives attachment to the muscles of mastication. The coronoid process on its medial side, anterior border, and posterior border receives the insertion of the temporalis muscle and on the lateral side, it has an attachment of a few fibers of the masseter. The pull of these muscles and the chewing pattern of a person are thought to contribute as one of the important factors resulting in various shapes of the coronoid process. The morphometric parameters of the coronoid process, like size and shape, show differences. These parameters are influenced by various factors like genetics, the pull of the temporalis muscles, dietary patterns, and also hormones⁽⁵⁾. The coronoid process lies close to the last molar tooth, so variations in the shape result in narrowing of vestibular space, which affects movement of the mandible^(2,6). Number of previous studies had reported various shapes of the coronoid processes in adult human mandibles, like hook-shaped, triangular-shaped, and round-shaped coronoid processes, opposed to the regular description of 'crows’ beak' type of coronoid process^(5,7). The race of the people affects the facial skeleton development and indirectly contributes to the difference in shape of the coronoid process. The incidence of the hook shape of the coronoid process was individual^(3).

The coronoid process is commonly used as an autogenous graft for the correction of facial defects, as it has a separate vascular pedicle⁽⁷⁾. The bone grafts can be obtained from various bones of the human body, like ribs, ilium, calvarias, etc., but each autogenous graft site has its own morbidity associated with it. The coronoid process of the mandible can be used for a local bone graft, as it can be harvested easily, with less dissection and very minimal morbidity, short hospitalization time, and no cutaneous scarring seen as the bone is harvested by the intraoral method^(8,9). Hence, the knowledge of the morphological shapes of the coronoid process in the local population is very important.

In the present study conducted in the East Godavari population, Andhra Pradesh, the triangular shape (55%) was more common than the hook shape. Triangular shape was more common in studies conducted by prajapat et al, Issac et al etc^(10,11). The rounded shape was the least among all three shapes. The incidence of different shapes compared with previous studies is represented in a tabular form.

The most common shape of the coronoid process found was a triangular shape in the population of East Godavari district, Andhra Pradesh. Knowledge of the shape of the coronoid process and the morphometry of the mandible is helpful in subjects like craniofacial surgery, radiology, anthropology, and oral dentistry. The differences in morphometric features of the coronoid process, like size and shape, were because of various factors like the race, the dietary habits, the chewing habits, and the pull of the temporalis muscle.

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