Restoration of occlusal and proximal contacts by a single molar crown improves the smoothness of the masticatory movement

Objectives This study aimed to investigate the influence of the occlusal form variation of a single molar crown on the smoothness of masticatory movement. Methods The subjects included 19 adults who visited the hospital seeking a single prosthetic restoration on a molar. Three types of crown were used: (i) an anatomical form, (ii) a flat occlusal table with occlusal contacts and (iii) a flat occlusal table without occlusal contacts. All restored the proximal contacts, and were temporarily cemented in random order. One week after each crown was cemented, the jaw movement trajectory was recorded during gum chewing and the normalized jerk-cost (NJC) was calculated for each chewing cycle. The mean and standard deviation of the chewing rhythms, pathways and peak speeds, were also calculated. Results Restoration by the anatomical occlusal form crown significantly decreased the standard deviation of the parameters for the chewing rhythm. The jerk analysis showed a significant NJC decrease after all types of crown were placed on the treated side. The smoothness of masticatory movement was more improved in the subjects who received each type of crown on their mandibular molar than those on the maxillary molar. Conclusions These results suggest that achieving occlusal and proximal contacts by a single crown treatment is associated with a reduction in the variability of jaw movements. These findings confirm the clinical importance of restoring occlusal contacts and proximal contacts even for a single tooth.