The normal range of maximum mouth opening and its correlation with height or weight in the young adult Chinese population

BACKGROUND/PURPOSE: Maximum mouth opening (MMO) is an important diagnostic reference for dental clinicians. However, the relationship between either body height or weight of the individual and their subsequent MMO has, up to now, been unclear. The purpose of this study was to measure the MMO of healthy young Chinese adults and to analyze the possible correlation of MMO with either height or weight. MATERIALS AND METHODS: A total of 452 young Chinese adults, aged 20–35 years (238 males, 214 females) were selected for this cross-sectional study. We recorded the MMO, age, sex, height, and weight of the participants. Two standardized examiners performed the clinical oral assessments. Independent sample t tests were used to examine the difference in MMO relative to sex. Pearson's correlation and simple linear regression were used to estimate the correlation between MMO and either height or weight. RESULTS: The average MMO across the 452 participants was 52.02 ± 5.09 mm, and the average MMO of males (54.18 ± 5.21 mm) was significantly larger than that of females (49.62 ± 3.69 mm; P < 0.001). The mean MMO was moderately positively correlated with height (r = 0.54; P < 0.001) and weight (r = 0.50; P < 0.001). In the regression model, it was estimated that, for every 10 cm or 10 kg, MMO increased by about 3.6 mm or 1.8 mm, respectively. CONCLUSION: With the limits of the present study, both height and weight were found to be significantly correlated with the MMO of Chinese young adults and may be significant predictors of MMO measurement.