Correlations Between Masticatory Performance by a Fully Automated Analyzing System and Craniofacial Morphology in Patients with Mandibular Prognathism

Purpose : Previous studies on masticatory function in patients with mandibular prognathism have examined various aspects such as occlusal contact area, mandibular movement, and masticatory muscle activity. However, there have been few reports on the relationship between objective masticatory performance and craniofacial morphology in patients with mandibular prognathism due to the lack of a quick and simple method. This study aimed to clarify the relationship between masticatory performance and craniofacial morphology for patients with mandibular prognathism by using a fully automatic system. Subjects and Methods : Ten patients with mandibular prognathism (age : 16.6±1.3 years) and 10 volunteers with individual normal occlusion (age : 24.1±2.6 years) as controls were enrolled in this study. At the initial examination, lateral cephalograms were taken and analyzed. Masticatory performance was assessed by a fully automatic measuring system (Tokyo-koden, Tokyo, Japan) using a testing gummy jelly (UHAMikakuto, Osaka, Japan). Chewing time was measured with a stopwatch. Occlusal contact area was measured using a silicone testing material and analyzing device (BiteEye, GC, Tokyo, Japan). Maximum bite force was also measured by using an occlusal force meter (Morita, Osaka, Japan). Wilcoxon's rank sum test was used for comparing the masticatory performance, occlusal contact area and maximum bite force between the two groups. Spearman's rank correlation coefficient was used to evaluate the relationship between masticatory performance and craniofacial morphology. Results : Masticatory performance, occlusal contact area and maximum bite force were significantly lower in the patient group than in the control group. These results suggest that remarkable skeletal discrepancy and lack of tooth contact in the anterior regions and lateral segments may yield a decrease in occlusal contact area, maximum bite force and masticatory performance. A negative correlation was found between masticatory performance and gonial angle and ANS-Me, whereas a positive correlation was found between masticatory performance and chewing time. These findings suggest that the load on the masticatory muscles was reduced in patients with mandibular prognathism due to a decrease in masticatory performance, resulting in the opening of the gonial angle which is the attachment area of the masseter muscle, and in the enlargement of anterior lower facial height. Conclusions : A close relationship between masticatory 1)新潟大学大学院医歯学総合研究科歯科矯正学分野(主任:齋藤 功教授) 2)新潟大学大学院医歯学総合研究科包括歯科補綴学分野(主任:小野高裕教授) 1)Division of Orthodontics, Niigata University Graduate School of Medical and Dental Sciences (Chief : Prof. Isao SAITO) 2)Division of Comprehensive Prosthodontics, Niigata University Graduate School of Medical and Dental Sciences(Chief : Prof. Takahiro ONO) 238 日顎変形誌 2019 年 深町 直哉,他 performance and craniofacial morphology was found in the patient group with mandibular prognathism. The fully automatic measuring system is considered to be useful for evaluating masticatory performance in patients objectively and quantitatively in a short time.