Abstract
It has been suggested that a relationship exists between severe temporomandibular joint (TMJ) pathology and craniofacial morphology. Although mandibular retrognathism has been reported particularly frequently, no reports have addressed acquired facial deformity of patients with mandibular prognathism. This study investigated the relationship between TMJ pathology and mandibular prognathism. In total, 160 female patients with malocclusion and suspicion of having TMJ disk displacement were enrolled in this study. Their mean age was 27.2 years (range, 15.0-56.0 years). Cluster analysis was performed on eight variables from the lateral cephalogram to evaluate differences in craniofacial morphology. The subjects were classified into a mandibular prognathism (MP) group (n = 59), class I group (n = 64), and micromandibular (MM) group (n = 37). The MP group was further subdivided into a high-angle MP (HMP) (n = 18), average-angle MP (AMP) (n = 35), and low-angle MP (LMP) group (n = 6) according to the cluster analysis results. Magnetic resonance imaging and orthopantomography were performed to identify each subject's intra-articular pathologic status. Orthopantomography was used to analyze the measurements of the mandibular condyle and ramus. The status of the TMJ was classified as disk displacement with/without reduction, osteoarthritis (OA), or normal. The relationship between the status of the TMJ and the craniofacial morphology was statistically investigated. The incidence of disk displacement and OA were lowest in the MP group and highest in the MM group with statistical significance. Additionally, the incidence of disk displacement without reduction was highest in the MM group with statistical significance. The greatest condylar height and condylar/ramus ratio occurred in the MP group with statistical significance. The next greatest occurred in the class I and MM groups, respectively. The smallest ramus height occurred in the MM group with statistical significance. There were no significant differences in the incidence of any TMJ pathology status among the three MP groups. The greatest condylar height occurred in the HMP group with statistical significance; the next greatest heights occurred in the LMP and AMP groups, respectively. The greatest ramus height occurred in the LMP group with statistical significance; the next greatest heights occurred in the AMP and HMP groups, respectively. The highest condylar/ramus ratio occurred in the HMP group with statistical significance.
CONCLUSIONS: This study suggests that patients with mandibular prognathism have a lower risk of onset and progression of TMJ disk displacement than do patients without mandibular prognathism. No definite correlation exists between the vertical craniofacial morphology of mandibular prognathism and TMJ pathology.
