Evidence of measures of normalcy for thickness of masseter muscle evaluated with ultrasound: a review study

The objective was to study measures of normality for the thickness of the masseter muscle, and the methods of measurement of thickness using ultrasound. Was conducted a review from databases MEDLINE, LILACS, JCR and PubMed. Publications were used until June 2013. Works that involved young-adults individuals, healthy as the stomatognathic system - without the presence of signs and symptoms of temporomandibular joint disorders were included. 166 articles has been found. By reading the titles, repeated articles were excluded, remaining 108 studies. After reading the title and the exclusion of articles that were not related to the theme, 54 papers were obtained. Reading the abstracts allowed the acquisition of 22 studies. In the analysis of the measures t tests were used for paired-sample and independent, verified the confidence intervals and prepared forest plot graphics to study the heterogeneity of the studies. It was observed that the masseter muscle in males demonstrates to be thicker when compared to the women's, both at rest and in contraction. A comparison of resting state between the genders revealed no significant difference. The same occurred in the contraction. Also was verified the association of other methods with ultrasonography. The probability sample obtained revealed values for the state of contraction and rest in both sexes. Measurements demonstrated differences between the genders. Significant heterogeneity was found in the study's data. The measurement of the thickness of the masseter muscle with ultrasonography is presented in different studies as an objective method, precise and reproducible.本研究旨在探究咬肌厚度的正常测量指标，以及采用超声检测咬肌厚度的方法。本研究针对MEDLINE、LILACS、JCR及PubMed数据库开展了系统综述，检索时限截至2013年6月。纳入研究对象为健康青年成人，且口颌系统无颞下颌关节紊乱病的体征与症状。初检出166篇文献，通过标题筛选剔除重复文献后剩余108项研究；进一步阅读标题并排除与主题无关的文献后得到54篇论文；再通过阅读摘要最终纳入22项研究。数据分析采用配对样本t检验与独立样本t检验，同时验证置信区间并绘制森林图以分析研究间的异质性。结果显示，无论在静息状态还是收缩状态，男性的咬肌厚度均大于女性；但静息状态下不同性别间的咬肌厚度无显著差异，收缩状态下亦如此。此外，本研究还验证了其他检测方法与超声检测法的关联性。本次抽样获得了两性在静息与收缩状态下的相关数值，测量结果存在性别差异。研究数据显示存在显著的异质性。现有多项研究表明，采用超声检测咬肌厚度是一种客观、精准且可重复的测量方法。