Research progress in effect of chewing-side preference on temporomandibular joint and its relationship with temporo-mandibular disorders / 浙江大学学报·医学版

Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.

Correlation of mastication and masticatory movements and effect of chewing side preference

The aims of this study were to correlate masticatory performance with mandibular movements during mastication, and to evaluate masticatory performance and mandibular movements of subjects with different types of mastication. Seventy-eight healthy dentate subjects were selected and divided into 2 groups: bilateral and unilateral chewers. This classification was set by using kinesiography during mastication of an artificial material. Unilateral mastication was defined as the majority of the cycles took place at one specific side. The same tracings used to define type of mastication were used to evaluate mandibular movements by means of its parameters. Masticatory performance was analyzed by comminution of the artificial material and a sieving method. Statistical analysis was performed by Spearman’s correlation method, and Mann-Whitney and Studentʼs t-test, when appropriate, at 5 percent significance level. No correlation was found between masticatory performance and parameters of mandibular movement during mastication. Bilateral chewers presented significantly better (p<0.05) masticatory performance than unilateral ones, however no differences in parameters of mandibular movement were found between groups. Within the limits of this study, it may be concluded that parameters of jaw movements during mastication are not related to masticatory performance, and that the presence of a preferred chewing side worsens mastication.

Os objetivos deste estudo foram correlacionar a performance mastigatória com trajetória mandibular durante a mastigação, assim como avaliar performance mastigatória e trajetória mandibular de indivíduos com tipos diferentes de mastigação. Setenta e oito indivíduos saudáveis e dentados foram selecionados e divididos em 2 grupos: mastigação do tipo bilateral e unilateral. Esta classificação foi estabelecida utilizando-se um cinesiógrafo durante a mastigação de um material artificial. A mastigação foi definida como unilateral quando a maioria dos ciclos mastigatórios foi realizada em um lado específico. Os mesmos traçados obtidos para a classificação do tipo de mastigação foram usados para avaliar a trajetória mandibular durante esta função, por meio dos parâmetros do movimento. A performance mastigatória foi analisada pela trituração do material artificial mencionado e um sistema de peneiras. A análise estatística foi determinada pelo método de correlação de Spearman, e pelos testes de Mann-Whitney ou T-Student com nível de significância de 5 por cento. Não foi encontrada correlação entre performance mastigatória e os parâmetros da trajetória mandibular durante a mastigação. Indivíduos com mastigação bilateral apresentaram melhor performance mastigatória do que indivíduos com mastigação unilateral (p<0,05), contudo, os parâmetros da trajetória mandibular não foram diferentes entre os 2 tipos de mastigadores. Nos termos em que este estudo foi conduzido, pode-se concluir que os parâmetros do movimento mandibular durante a mastigação não estão relacionados com a performance mastigatória, que a presença de preferência de lado prejudica a mastigação.