118 Chapter 6 MUC5B levels of the palate with the palatal surface area. Furthermore, the participants were dichotomized based on their sex and the dimensions of the palate. The median of the palatal surface area was used to create two equal groups: ‘small’ palatal surface area (< 2138.0 mm2) and ‘large’ palatal surface area (≥ 2138.0 mm2). The size of the correlation coefficient was interpreted as poor (r = 0.1–0.2), fair (r = 0.3–0.5), moderate (r = 0.6–0.7) or very strong (r = 0.8– 0.9) correlation [39]. Furthermore, a multivariate analysis, multiple linear regression, was performed to investigate the possible association between the salivary film thickness and all independent variables. The salivary film thicknesses of both the anterior and the posterior palate were considered as dependent variables, while the palatal surface area, sex, the UWS and CH-SWS flow rate were considered as independent variables. All these independent variables were chosen because they could affect the thickness of the salivary film. To identify the degree of multicollinearity among the independent variables, the variance inflation factor (VIF) was calculated. The VIF for these variables was < 5, which indicates that there is no multicollinearity present among these variables [40, 41]. Additionally, the R square was reported. No multiple regression was conducted for the MUC5B levels of the anterior palate as the variance of the residuals was not constant and also multivariate normality was not met (residuals were not normally distributed). All significance levels (P) were set at 0.05. RESULTS Fifty-one volunteers signed up for this study (Fig. 1). The average age of female and male participants did not differ significantly (Mann–Whitney U test p > 0.05). Eleven volunteers had a systemic disease and/or were taking various medications that could initiate dry-mouth symptoms (Fig. 1). After the exclusion of these volunteers, the average age of the remaining 40 volunteers was 40.1 ± 13.4 years. The average age of the female and male participants did not differ significantly (Mann–Whitney U test p > 0.05). Ten of the remaining 18 female volunteers used contraceptive medication.
RkJQdWJsaXNoZXIy MTk4NDMw