Alteration of the angle of the coronoid process in prognathism

Abstract

Muscles and bones may dynamically affect the functions of each other, resulting in changes in the activity of the muscle and/or morphological change in the bones. However, alterations of the morphology of the coronoid process have not been documented in relation to the temporal muscle between the mandible and the cranium. Angles of the coronoid process to the line through the right and the left frontotemporale were measured on posteroanterior (PA) cephalograms in patients with normal occlusions and Class II, division 1 malocclusions, and those with true skeletal Class III malocclusions. Standard deviation of the angle of the coronoid process in patients with Class III malocclusions was greater than those subjects with normal occlusion or Class II, division 1 malocclusions. Differences of angles between the right and the left coronoid process in each patient of either sex were significantly large in true skeletal Class III malocclusions (both P < 0.001). Large variation of angle of the coronoid process was related to prognathism, and this effect may represent adaptation of temporal muscle function to a variety of alterations in mandibular morphology.

Relationship between the inclination of the coronoid process of the mandible and the electromyographic activity of the temporal muscle in skeletal Class I and II individuals

“…Class II individuals did not present a significant variation in this inclination, indicating uniformity of the group with regard to this parameter (9).…”

“…The mandible undergoes morphological and spatial alterations during the growth of the craniofacial complex, and these alterations vary, depending on the maxillomandibular relationship of the individual (9,11,21). Analysis of the correlation between the inclination of the coronoid process and activity of the anterior part of the temporal muscle in different skeletal classes shows the influence of the alterations inherent to these classes, as undergone by the mandible, on the morpho-functional relationship between the coronoid process and the temporal muscle.…”

“…It has also been clarified that the tension exerted by this muscle can distinctly influence the growth and morphology of the coronoid process in different skeletal classes (9).…”

The utility of domestic dogs in assessing human morphological variation

“…Patients with congenital, bilateral coronoid process enlargement have significantly greater lower facial height and a square-shaped mandible with a small gonial angle (Isberg and Eliasson, 1990). Yamaoka et al (2001) measured the angle of the coronoid process relative to the cranium on radiographs of patients with malocclusions. Differences in angle by side were related to prognathism; in men, the angle of the coronoid process (lateral inclination) was greater on the right than on the left side.…”

Bilateral mandibular coronoid hypoplasia

“…1 The mandible and the temporal bone develop according to the temporalis muscle function before and after birth. 2 It is also known that the posterior muscle group in the temporal region helps the development of the condyle and coronoid process. 2 This may result as hyperplasia or hypoplasia of the bone.…”