Association between salivary flow rate and depressive symptoms with adjustment for genetic and family environmental factors in Japanese twin study

Factors Influencing the Localization of Mandibular Third Molars in Twins

PURPOSE

The aim of the present study was to evaluate the genetic and environmental factors influencing the localization of mandibular third molars by analyzing the panoramic radiographs of twins. We examined the mandibular third molars of Japanese monozygotic (MZ) and dizygotic (DZ) twins recruited by the Osaka University Center for Twin Research.

MATERIALS AND METHODS

The present study included 49 pairs (98 participants) of MZ twins and 11 pairs (22 participants) of DZ twins. Using panoramic radiography, we evaluated the degree of eruption of mandibular third molars according to the height of the alveolus bone and the third molar space/crown width ratio. Using co-twin control analysis and a generalized linear mixed model, we evaluated the effects of various factors, including gender, age, body height, number of teeth, length of the lower dental arch, existence of a second molar, bruxism, and previous orthodontic therapy.

RESULTS

Body height, third molar space/crown width ratio, and length of the mandibular dental arch were related to the degree of mandibular third molar eruption and were strongly influenced by genetic factors rather than common or unique environmental factors.

CONCLUSIONS

The degree of third molar eruption was more similar among MZ twins than among DZ twins; therefore, genetic factors can be expected to have more significant influence than will environmental factors. These results can help identify the trend of third molar eruption from a young age, allowing us to advise the early extraction of mandibular third molars for patients with a short stature, narrow retromolar space, or short mandibular dental arch. In addition, if the genes that influence the degree of eruption were identified, we would be better equipped to predict an individual's risk of impaction, and indications for extraction might change.

Factors associated with hyposalivation and xerostomia in older persons in South Brazil

OBJECTIVE

This study aimed to investigate characteristics associated with xerostomia and hyposalivation in older persons.

BACKGROUND

Saliva is one of the most important body fluids and plays an important role in food bolus formation, lubricating the oral mucosa and protecting teeth against demineralisation.

MATERIALS AND METHODS

This is a cross-sectional study nested within a cohort and includes a sample of 872 older persons living independently in the community, both in rural and urban areas in Carlos Barbosa, Brazil. Data collection included standardised interviews to identify sociodemographic, behavioural and health-related variables, as well as oral clinical examination performed by two trained/calibrated dentists. Poisson regressions with robust variance were used to calculate the crude and adjusted prevalence ratios (PR) and their respective 95% confidence intervals.

RESULTS

The mean age was 68.5 ± 6.7 years, and the majority of the sample consisted of women (65.3%). The prevalence of xerostomia, of low stimulated salivary flow rate and low at rest salivary flow rate were 338 (38.8%), 494 (56.6%), 320 (36.7%), respectively. In the final adjusted model, women had a significantly increased prevalence of xerostomia (PR = 1.34; 95% CI: 1.12-1.61), as well as participants taking medication continuously (PR = 1.45; 95% CI: 1.16-1.82) and those with depressive symptoms (PR = 1.49; 95% CI: 1.27-1.76). Lower at rest (PR = 1.45, 95% CI: 1.22-1.72) and lower stimulated salivary flow were more prevalent in women (PR = 1.27, 95% CI: 1.11-1.44), while lower stimulated salivary flow was more prevalent in older persons taking medication continuously (PR = 1.24, 95% CI: 1.07-1.43).

CONCLUSION

Salivary hypofunction and xerostomia were more prevalent in women and in those with continuous medication use; however, depressive symptoms were associated only with xerostomia. Measures are required to promote oral comfort in cases of xerostomia, thereby reducing the unpleasant sensation of dry mouth and hyposalivation consequences in clinical practice.