Mutans streptococci in preschool twins

Objective: The purpose of this study was to determine whether genetic factors influence variation in salivary levels of the mutans streptococci (MS) in preschool twins. Design: The study population consisted of 48 pairs of monozygotic (MZ) twins and 54 pairs of dizygotic (DZ) twins. Genotyping eight highly polymorphic DNA markers determined zygosity. Demographic data and antibiotic exposure as reported by mothers were obtained by a face-to-face interview. Salivary levels of MS were determined by the Stripmutans (TM) test. Test results are reported on a scale of 0-3. Regression analysis, two sample t-tests and structural equation modeling were applied to analyse the data. Results: Only 6 % of the participants ever visited a dentist (F component of the DMFS was 0 for this population). Average salivary scores for the mutans streptococci were significantly different between MZ (1.1 +/- 0.1) and DZ (0.8 +/- 0.1) twins (p = 0.021). High salivary levels of MS (scores 2 and 3) were observed in 42 % of MZ twins and in 26 % of DZ twins. Regression analysis on the MS salivary levels revealed no significant effects of age, gender and antibiotic intake for MZ or DZ twins. The heritability of mutans streptococci colonisation in 48 pairs MZ and in 26 pairs of DZ twins was estimated to be 52 %. The non-shared environment contribution was estimated to be 48 %. Conclusions: These results suggest that variation in the salivary levels of the mutans streptococci is significantly contributed by genetic factors. (c) 2004 Elsevier Ltd. All rights reserved.