Evaluation of masticatory efficiency in patients with jaw deformities using the gummy jelly method

The gummy jelly method is easy to perform and is a reliable method for evaluating masticatory function. This study aimed to evaluate the masticatory function of patients with jaw deformities using the gummy jelly method and to analyse the factors that influence the masticatory function. Twenty-one patients who underwent the correction of jaw deformity at our department from January 2018 to April 2019, along with individuals with normal occlusion (controls), were enrolled in the study. The study subjects were divided into two groups: the post-treatment group, patients who had undergone orthognathic surgery for jaw deformity (n = 21); and the control group comprising individuals with normal occlusion (n = 20). Masticatory efficiency, number and area of occlusal contacts, and maximal mouth opening were measured. The masticatory efficiency decreased 1 month after surgery and then gradually increased, but the final mean value 12 months after surgery was approximately 60% in the control group. The number and area of occlusal contacts before surgery were significantly lower in the post-treatment group than those in the control group and decreased 1 month after surgery and then gradually increased. However, the mean values of the post-treatment group were significantly lower than those of the control group at all time points in this study. Furthermore, no correlations were observed between masticatory efficiency (shearing ability) and the number and area of occlusal contacts. In conclusion, the masticatory efficiency and occlusal contacts of patients undergoing orthognathic surgery for jaw deformity at 12 months postoperatively were poorer than the normal occlusion group.