Heritability of Caries Scores, Trajectories, and Disease Subtypes.

Previous studies report that dental caries is partially heritable, but there is uncertainty in the magnitude of genetic effects and little understanding of how genetic factors might influence caries progression or caries subtypes. This study aimed to estimate the relative importance of genetic and environmental factors in the etiology of different caries outcomes using a twin-based design. Analysis included up to 41,678 twins in the Swedish Twin Register aged 7 to 97 y, and dental data were obtained from preexisting dental records. The outcome measures were 1) summary indices of caries experience, 2) parameters representing trajectory in caries progression derived from longitudinal modeling, and 3) caries scores in groups of biologically similar tooth surfaces derived from hierarchical clustering of tooth surfaces (termed caries clusters). Additive genetic factors explained between 49.1% and 62.7% of variation in caries scores and between 50.0% and 60.5% of variation in caries trajectories. Seven caries clusters were identified, which had estimates of heritability lying between 41.9% and 54.3%. Shared environmental factors were important for only some of these clusters and explained 16% of variation in fissure caries in molar teeth but little variation in other clusters of caries presentation. The genetic factors influencing these clusters were only partially overlapping, suggesting that different biological processes are important in different groups of tooth surfaces and that innate liability to some patterns of caries presentation may partially explain why groups of tooth surfaces form clusters within the mouth. These results provide 1) improved quantification of genetic factors in the etiology of caries and 2) new data about the role of genetics in terms of longitudinal changes in caries status and specific patterns of disease presentation, and they may help lay the foundations for personalized interventions in the future.

Carbonic Anhydrase 6 Gene Variation influences Oral Microbiota Composition and Caries Risk in Swedish adolescents.

Carbonic anhydrase VI (CA6) catalyses the reversible hydration of carbon dioxide in saliva with possible pH regulation, taste perception, and tooth formation effects. This study assessed effects of variation in the CA6 gene on oral microbiota and specifically the acidophilic and caries-associated Streptococcus mutans in 17-year old Swedish adolescents (n = 154). Associations with caries status and secreted CA6 protein were also evaluated. Single Nucleotide Polymorphisms (27 SNPs in 5 haploblocks) and saliva and tooth biofilm microbiota from Illumina MiSeq 16S rDNA (V3-V4) sequencing and culturing were analysed. Haploblock 4 (rs10864376, rs3737665, rs12138897) CCC associated with low prevalence of S. mutans (OR (95% CI): 0.5 (0.3, 0.8)), and caries (OR 0.6 (0.3, 0.9)), whereas haploblock 4 TTG associated with high prevalence of S. mutans (OR: 2.7 (1.2, 5.9)) and caries (OR: 2.3 (1.2, 4.4)). The TTG-haploblock 4 (represented by rs12138897(G)) was characterized by S. mutans, Scardovia wiggsiae, Treponema sp. HOT268, Tannerella sp. HOT286, Veillonella gp.1 compared with the CCC-haploblock 4 (represented by rs12138897(C)). Secreted CA6 in saliva was weakly linked to CA6 gene variation. In conclusion, the results indicate that CA6 gene polymorphisms influence S. mutans colonization, tooth biofilm microbiota composition and risk of dental caries in Swedish adolescents.

Microbial Complexes and Caries in 17-Year-Olds with and without Streptococcus mutans.

Streptococcus mutans is a key bacterial species in the caries process, which affects >90% of the population worldwide. However, other acidogenic and aciduric/acidophilic species may contribute to disease development. In Sweden, a country with low prevalences of caries and S. mutans, a significant portion of caries-affected adolescents lack detectable levels of S. mutans. The objectives of the present study were 1) to characterize the tooth biofilm and saliva microbiota of adolescents with caries disease, with or without detectable S. mutans, from tooth biofilm and saliva samples and 2) to assess taxa clustering in the tooth biofilm and saliva samples and relate this information to caries status. For 17-y-old participants ( N = 154), enamel and dentin caries (the total number of present carious surfaces in the enamel and dentin) and caries experience (the number of decayed and filled tooth surfaces) were recorded, dental biofilm and saliva samples obtained, and information on medical and lifestyle habits collected. Multiplex 16S rDNA (V3-V4) sequencing of bacterial DNA was performed with the Illumina MiSeq platform. The Human Oral Microbiome Database and the ProbeSeq pipeline were used in the HOMI NGS procedure. In subjects with caries experience, high levels of S. mutans were associated with a few species and low levels with a panel of saccharolytic species. Present caries was similarly associated with a panel of saccharolytic species in subjects without S. mutans. Furthermore, tooth biofilm microbiota could be used to establish 4 clusters of subjects with different caries experiences. In particular, high levels of S. mutans were associated with the presence of a few influential species in multivariate modeling, including Scardovia wiggsiae. By contrast, a panel of less avid lactic acid-producing species was influential in patients with undetectable or low S. mutans levels in such modeling. These findings support a prominent role of S. mutans in infected adolescents but also the ecologic concept, especially in S. mutans-free subjects.

The Microbiome in Populations with a Low and High Prevalence of Caries.

The oral microbiota was compared between Romanian adolescents with a high prevalence of caries and no dental care and Swedish caries-active and caries-free adolescents in caries prevention programs and with a low prevalence of caries. Biofilm samples were analyzed by FLX+ pyrosequencing of the V1 to V4 hypervariable regions of the 16S rRNA gene and polymerase chain reaction (PCR)/quantitative PCR (qPCR) for Streptococcus mutans and Streptococcus sobrinus. Sequences obtained blasted to 9 phyla, 66 genera, and 401 human oral taxa (HOT) in the 16S rRNA Human Oral Microbiome Database, of which 295 were represented by ≥20 sequences. The Romanian adolescents had more sequences in Firmicutes and fewer in Actinobacteria phyla and more sequences in the genera Bacteroidetes [G-3], Porphyromonas, Abiotrophia, Filifactor, Peptostreptococcaceae [11][G-4], Pseudoramibacter, Streptococcus, and Neisseria and fewer in Actinomyces, Selenomonas, Veillonella, Campylobacter, and TM7 [G-1] than the Swedish groups. Multivariate modeling employing HOT, S. sobrinus and S. mutans (PCR/qPCR), and sugar snacks separated Romanian from Swedish adolescents. The Romanian adolescents' microbiota was characterized by a panel of streptococci, including S. mutans, S. sobrinus, and Streptococcus australis, and Alloprevotella, Leptotrichia, Neisseria, Porphyromonas, and Prevotella. The Swedish adolescents were characterized by sweet snacks, and those with caries activity were also characterized by Prevotella, Actinomyces, and Capnocytophaga species and those free of caries by Actinomyces, Prevotella, Selenomonas, Streptococcus, and Mycoplasma. Eight species including Streptococcus mitis and Streptococcus species HOT070 were prevalent in Romanian and Swedish caries-active subjects but not caries-free subjects. In conclusion, S. mutans and S. sobrinus correlated with Romanian adolescents with caries and with limited access to dental care, whereas S. mutans and S. sobrinus were detected infrequently in Swedish adolescents in dental care programs. Swedish caries-active adolescents were typically colonized by Actinomyces, Selenomonas, Prevotella, and Capnocytophaga. Hence, the role of mutans streptococci as a primary caries pathogen appears less pronounced in populations with prevention programs compared to populations lacking caries treatment and prevention strategies.

White-spot lesions and gingivitis microbiotas in orthodontic patients.

White-spot lesions (WSL) associated with orthodontic appliances are a cosmetic problem and increase risk for cavities. We characterized the microbiota of WSL, accounting for confounding due to gingivitis. Participants were 60 children with fixed appliances, aged between 10 and 19 yrs, half with WSL. Plaque samples were assayed by a 16S rRNA-based microarray (HOMIM) and by PCR. Mean gingival index was positively associated with WSL (p = 0.018). Taxa associated with WSL by microarray included Granulicatella elegans (p = 0.01), Veillonellaceae sp. HOT 155 (p < 0.01), and Bifidobacterium Cluster 1 (p = 0.11), and by qPCR, Streptococcus mutans (p = 0.008) and Scardovia wiggsiae (p = 0.04) Taxa associated with gingivitis by microarray included: Gemella sanguinis (p = 0.002), Actinomyces sp. HOT 448 (p = 0.003), Prevotella cluster IV (p = 0.021), and Streptococcus sp. HOT 071/070 (p = 0.023); and levels of S. mutans (p = 0.02) and Bifidobacteriaceae (p = 0.012) by qPCR. Species' associations with WSL were minimally changed with adjustment for gingivitis level. Partial least-squares discriminant analysis yielded good discrimination between children with and those without WSL. Granulicatella, Veillonellaceae and Bifidobacteriaceae, in addition to S. mutans and S. wiggsiae, were associated with the presence of WSL in adolescents undergoing orthodontic treatment. Many taxa showed a stronger association with gingivitis than with WSL.

Mode of birth delivery affects oral microbiota in infants.

Establishment of the microbiota of the gut has been shown to differ between infants delivered by Caesarian section (C-section) and those delivered vaginally. The aim of the present study was to compare the oral microbiota in infants delivered by these different routes. The oral biofilm was assayed by the Human Oral Microbe Identification Microarray (HOMIM) in healthy three-month-old infants, 38 infants born by C-section, and 25 infants delivered vaginally. Among over 300 bacterial taxa targeted by the HOMIM microarray, Slackia exigua was detected only in infants delivered by C-section. Further, significantly more bacterial taxa were detected in the infants delivered vaginally (79 species/species clusters) compared with infants delivered by C-section (54 species/species clusters). Multivariate modeling revealed a strong model that separated the microbiota of C-section and vaginally delivered infants into two distinct colonization patterns. In conclusion, our study indicated differences in the oral microbiota in infants due to mode of delivery, with vaginally delivered infants having a higher number of taxa detected by the HOMIM microarray.

Influence of a low xylitol-dose on mutans streptococci colonisation and caries development in preschool children.

AIM: To evaluate the effect of xylitol-containing tablets on mutans streptococci colonisation and caries development in preschool children. STUDY DESIGN: Randomised single-blind prospective design. METHODS: The material consisted of 132 healthy 2-year-old children, 71 boys and 61 girls and they were assigned to a xylitol tablet (test) group or a non-intervention control group. The mean age was 2 years + 1 month in both groups. The drop-out rate was 10.6% during the 2-year trial. The test group was given 1-2 xylitol tablets (0.5-1g) per day during 1.5 years. Mutans streptococci (MS) enumeration was performed at baseline and semi-annually in the children and at baseline or shortly after in the mothers with a chair-side technique. Caries prevalence was scored at baseline and the age of 4 years. RESULTS: No statistically significant differences in MS colonisation were disclosed between the test and control groups at baseline or any of the designated follow-ups. A statistically significant positive relationship was found between the maternal salivary MS levels and the colonisation of the children in the control group at 2.5 years, 3 years and 3.5 years (r=0.39, r=0.35; r=0.30; p<0.01, p<0.01 and p<0.05) but not in the xylitol tablet group (p<0.05). The mean caries prevalence was lower in the test group compared with the control group at 4 years of age (dmfs 0.38 +/-1.05 vs. 0.80 +/-2.60) but the difference was not statistically significant. CONCLUSION: The findings do not support a low-dose xylitol tablet program for caries prevention in preschool children.

Xylitol concentration in saliva and dental plaque after use of various xylitol-containing products.

The study consisted of two sets of experiments, one in saliva and one in dental plaque. The xylitol concentration in saliva was determined enzymatically in 12 children (mean age 11.5 years) after a standardised use of various xylitol products: (A) chewing gums (1.3 g xylitol), (B) sucking tablets (0.8 g xylitol), (C) candy tablets (1.1 g xylitol), (D) toothpaste (0.1 g xylitol), (E) rinse (1.0 g xylitol), and (F) a non-xylitol paraffin. Unstimulated saliva was sampled 1, 3, 8, 16 and 30 min after use. The concentration in dental plaque was determined after mouthrinses with contrasting amounts of xylitol (LX = 2.0 g, HX = 6.0 g, and control) and supragingival plaque was collected and pooled after 5, 15 and 30 min. The mean xylitol concentration in saliva at baseline was approximately 0.1 mg/ml. All xylitol-containing products resulted in significantly increased levels (p < 0.05) immediately after intake and remained elevated for 8-16 min in the different groups. The highest mean value in saliva was obtained immediately after use of chewing gums (33.7 +/- 16.4 mg/ml) and the lowest was demonstrated after using toothpaste (8.2 +/- 4.9 mg/ml). No significant differences were demonstrated between chewing gums (A), sucking tablets (B), candy (C) and rinses (E). In dental plaque, the mean values were 8.6 +/- 5.4 and 5.1 +/- 4.0 mg/ml 5 min after HX and LX rinses. Concerning the higher concentration, the values remained significantly elevated (p < 0.05) during the entire 30-min follow-up. In conclusion, commonly advocated xylitol-containing products gave elevated concentrations of xylitol in unstimulated whole saliva and dental plaque for at least 8 min after intake.