Comparative cross-sectional study of masticatory performance and mastication predominance for patients with missing posterior teeth

Abstract

Purpose

Missing posterior teeth can decrease masticatory function and cause horizontal mastication deviation, i.e., mastication predominance. Mastication predominance may lead to abnormal tooth attrition and temporomandibular disorders. This study evaluated masticatory performance and mastication predominance in patients with missing posterior teeth to investigate effects of missing posterior teeth on masticatory performance and mastication predominance.

Methods

Thirty volunteers with normal dentition (control group), 30 patients with unilateral missing posterior teeth (unilateral group), and 23 patients with bilateral missing posterior teeth (bilateral group) participated. Gummy jellies were used to evaluate participants’ masticatory performance, and electromyography was used to assess the degree of mastication predominance. Chewing gums, gummy jellies, and peanuts were used as foods of various hardnesses for evaluating mastication predominance.

Results

Compared with the control group, masticatory performance did not differ in the unilateral group but was significantly decreased in the bilateral group. With chewing gum and gummy jellies, the degree of mastication predominance was significantly increased in both unilateral and bilateral groups than the control group. With peanuts, the degree of mastication predominance was significantly increased in the unilateral group than the control group.

Conclusions

Although masticatory performance was not decreased in the unilateral group, the degree of mastication predominance was increased. Decreased masticatory performance was observed in the bilateral group, and for foods with normal hardness and soft foods, the degree of mastication predominance was increased. These results suggested that mastication predominance should be considered in the recovery of masticatory performance in patients with missing posterior teeth.

Introduction

Tooth loss may occur due to a range of causes, including periodontal disease, dental caries, and external injury [1], and it has been reported that its prevalence increases with age. Posterior teeth are relatively prone to loss, for reasons such as difficulty in performing efficient dental hygiene in this area and the considerable occlusal force to which they are subjected [2]. Several studies have investigated effects of posterior teeth loss on masticatory function [3], [4], with most focusing on decreased masticatory performance resulting from decreased occlusal support [5], [6], [7], [8]. The restoration of missing posterior teeth is considered important because decreased masticatory performance can decrease the quality of life [9]. In contrast, it has also been reported that even if posterior teeth are missing, masticatory performance is not significantly affected unless occlusal support decreases markedly [10]. Therefore, it appears that decreased masticatory performance is related to the overall condition of the dentition, i.e., how many and which teeth are missing.

In addition, missing posterior teeth can cause horizontal deviation toward the chewing side with increased occlusal support, i.e., mastication predominance [11]. Mastication predominance involves differences among masticatory performance, occlusal force, and jaw movement patterns on left and right sides [12], [13], [14] and can also increase mastication frequency and food accumulation in the oral vestibule [15]. Furthermore, sustained mastication predominance may cause facial deformities, abnormal tooth attrition, tooth fracture, jaw dysfunction, and temporomandibular disorders [16]. Moreover, it has been reported that the degree of mastication predominance varies according to the type of food being consumed [17].

In routine clinical dentistry, patients with missing posterior teeth undergo prosthodontic treatment with removable partial dentures, fixed partial dentures, or dental implants. The overall aim of these treatments is to restore masticatory performance. However, the importance of improvement in mastication predominance should be considered as well. This, in turn, requires a detailed grasp of the state of masticatory performance and mastication predominance in patients with missing posterior teeth, which has not been investigated before.

The present study aimed to investigate how unilateral and bilateral missing posterior teeth affected masticatory performance and mastication predominance. For this, a study population comprising volunteers with normal dentition and patients with unilateral missing posterior teeth and those with bilateral missing posterior teeth was enrolled. These participants’ masticatory performance was evaluated with the use of gummy jellies, whereas the degree of mastication predominance was evaluated by means of a portable electromyography (EMG) device.