Acidic proline-rich protein Db and caries in young children

Association of Dental Caries in Primary Teeth With HLA Class II Gene Among Syrian Children

Background and objectives Numerous studies have shown that there is evidence that genetic factors contribute in different ways to the occurrence of caries lesions, and the multiple differences in the human leucocytes antigen (HLA) gene patterns play an important role in the body's immune response. Therefore, this study aimed to evaluate the association between some HLA class II alleles (HLA-DR4, HLA-DQ2, HLA-DQ4) and early childhood caries (ECC) occurrence in Syrian children. Materials and methods The study included 80 children aged three to six, divided into two groups: Group 1 (n = 40) being severe early childhood caries (S-ECC) children (deft ≥ 10) and Group 2 (n = 40) being free caries children (deft = 0). The genomic DNAs were extracted and collected by taking a buccal swab using a sterile metal strip and were amplified by polymerase chain reaction-single specific primer (PCR-SSP) and then HLA-typing was performed for all alleles. Results There were no statistically significant differences in the frequency of occurrence of S-ECC, HLA-DR4, and HLA-DQ2 alleles (p = 0.626, 0.256 respectively), while the incidence of S-ECC was associated with the DQ4 allele (p = 0.012). Conclusion HLA class II molecules may play a crucial role in predisposing to ECC, since positive HLA-DQ4 may enhance the chance of developing ECC. However, no association were found between (HLA-DR4 and HLA-DQ2) and ECC.

Microbiome and metabolome associated with white spot lesions in patients treated with clear aligners

White spot lesions (WSLs) have long been a noteworthy complication during orthodontic treatment. Recently, an increasing number of orthodontists have found that adolescents undergoing orthodontic treatment with clear aligners are at a higher risk of developing WSLs. The oral microbiota and metabolites are considered the etiologic and regulatory factors of WSLs, but the specific impact of clear aligners on the oral microbiota and metabolites is unknown. This study investigated the differences in the salivary microbiome and metabolome between adolescents with and without WSLs treated with clear aligners. Fifty-five adolescents (aged 11-18) with Invisalign appliances, 27 with and 28 without WSLs, were included. Saliva samples were analyzed using 16S rRNA gene sequencing and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS); the data were further integrated for Spearman correlation analysis. The relative abundances of 14 taxa, including Actinobacteria, Actinomycetales, Rothia, Micrococcaceae, Subdoligranulum, Capnocytophaga, Azospira, Olsenella, Lachnoanaerobaculum, and Abiotrophia, were significantly higher in the WSL group than in the control group. Metabolomic analysis identified 27 potential biomarkers, and most were amino acids, including proline and glycine. The metabolites were implicated in 6 metabolic pathways, including alanine, aspartate and glutamate metabolism; glycine, serine and threonine metabolism; and aminoacyl-tRNA biosynthesis. There was a correlation between the salivary microbial and metabolomic datasets, reflecting the impact of clear aligners on the metabolic activity of the oral flora. A concordant increase in the levels of Lachnoanaerobaculum, Rothia, Subdoligranulum and some amino acids had predictive value for WSL development. In summary, when adolescents undergo long-term clear aligner therapy with poor oral hygiene habits, clear aligners can disrupt the balance of the oral microecosystem and lead to oral microbiota dysbiosis, thereby increasing the risk of developing WSLs. Our findings might contribute to the understanding of the pathogenesis of WSLs and provide candidate biomarkers for the diagnosis and treatment of WSLs associated with clear aligners.

Genetic aspects of dental caries

Dental caries is a common chronic disease affecting humans in all age groups. Various factors can affect the formation of caries including demineralization and remineralization processes with oral flora; dietary and oral hygiene habits; salivary composition, flow rate, pH and buffering capacity; morphological features of the teeth; fluoride exposures, environmental and socioeconomic factors. One of the most important factors causing inter-individual variations in caries susceptibility is the host genetics. Several genes affect individual caries susceptibility. Genes play a role in immune response, development of saliva and tooth enamel. The present review aims to overview the literature focusing on the genetic features of dental caries.

Protein Intake and Oral Health in Older Adults-A Narrative Review

Oral health is vital to general health and well-being for all ages, and as with other chronic conditions, oral health problems increase with age. There is a bi-directional link between nutrition and oral health, in that nutrition affects the health of oral tissues and saliva, and the health of the mouth may affect the foods consumed. Evidence suggests that a healthy diet generally has a positive impact on oral health in older adults. Although studies examining the direct link between oral health and protein intake in older adults are limited, some have explored the relationship via malnutrition, which is also prevalent among older adults. Protein-energy malnutrition (PEM) may be associated with poor oral health, dental caries, enamel hypoplasia, and salivary gland atrophy. This narrative review presents the theoretical evidence on the impact of dietary protein and amino acid composition on oral health, and their combined impact on overall health in older adults.

Role of salivary physicochemical and peptide levels in dental caries among children: An original research

Introduction:

Dental caries is a common oral disease that still needs to be thoroughly evaluated for understanding the pathophysiology. Hence, in our study, we evaluate the physicochemical and the peptide properties of the saliva and their role in dental caries among children.

Materials and Methods:

We conducted an observational in vitro study among 100 subjects of age 5–15 years. Decayed, missing, and filled surface (DMFT)/dmft was used to calculate the caries activity. The unstimulated saliva was evaluated for the peptides “LL-37, human neutrophil peptide (HNP) 1-3, and human beta-defensin-3” by ELIZA and for the “pH, buffer, and flow rate” of the saliva. The data thus obtained were analyzed to correlate caries and the salivary physiochemical and peptides using the “linear regression analysis.” P < 0.05 was deliberated as significant.

Results:

Although no statistically significant variation was seen between low and high caries risk groups and the salivary parameters in our study, we observed a negative correlation of the salivary peptides and caries. For the salivary peptide “HNP1-3,” there was a statistically significant variation.

Conclusion:

The salivary peptides may be carioprotective. However, further research has to be done to establish the mechanism of the action of these substances against caries.

Genetic Aspects of Dental Erosive Wear and Dental Caries

Objectives

The present review aims to give an overview of the literature focusing on novel genetic aspects of dental erosion and dental caries. Once the tooth erupts into the oral cavity, the regenerative capability of enamel is fundamentally limited due to the loss of dental epithelium during eruption. The susceptibility or resistance to dental erosion and caries is presumably a result of environmental, phenotypic, and/or genetic influence. Even though it is evident that individuals frequently exposing their teeth to acid and sugar are at high risk of developing dental erosion and caries, the findings exclusively based on these factors are elusive. Data resources and study selection. The present review was based on data collected from the National Library of Medicine database with different combinations of the following terms: "tooth," "dental," "dentin," "enamel," "erosion," "erosive wear," "caries," "decay," "gene," and "genetic." A total of forty-six studies met the inclusion criteria. Data were extracted by one reviewer and verified by another.

Conclusion

The high prevalence of erosion and caries among certain groups, and observations that not all individuals appearing to be at risk develop these lesions, has sparked research on identifying genetic effects to these conditions. A connection of genome-wide and candidate gene studies has increased considerably in the literature. This review reveals largely varying success among studies, demonstrating the difficulties of developing the study with adequate sample sizes and durable phenotype definitions that permit enough statistical power to identify genetic contributors.

Association of salivary physicochemical characteristics and peptide levels with dental caries in children

AIM

The purpose of this investigation was to evaluate the association of physicochemical properties and antimicrobial peptide levels of saliva with caries activity in children.

MATERIALS AND METHODS

The required volume of unstimulated saliva was collected from 41 children aged 3-12 years with no systemic diseases. Caries activity was calculated using DMFS and dmfs records for each participating child. Collected saliva samples were then examined for their flow rate, pH, and buffering capacity. The concentration of three peptides was assessed including LL-37, human neutrophil peptide (HNP) 1-3, and human beta-defensin (HBD)-3 through an enzyme-linked immunosorbent assay. The correlation between caries activity score (CAS) and salivary variables was looked using the linear regression and Spearman's correlation method. The comparison of CAS means between high- and low-value groups of salivary items was performed using independent sample t-test while the association of CAS and salivary parameters in categorical scale was tested by Chi-square test.

RESULTS

No statistically significant differences were found between the CAS means at low and high categories of each salivary physicochemical parameter and those of antimicrobial peptides. There was a negative correlation between HNP1-3 and CAS and also between HBD-3 and CAS, but these results were not statistically meaningful. High HNP1-3 concentration was noted in 67% of the low caries rate group and 29% of the high caries rate group, with a statistically significant difference between the low and high caries rate groups (P = 0.019).

CONCLUSION

Salivary inherent factors are not dominant determinants in caries activity. The current results may suggest that α-defensins (HNP1-3) have a protective role against dental caries.

Association of Salivary Statherin, Calcium, and Proline-Rich Proteins on Oral Hygiene: A Cross-Sectional Study

Background

Saliva, as a complex biofluid, plays a pivotal role in maintaining oral health and tooth integrity. There has been inconsistent data available on the relationship between salivary parameters and oral health. This study aims to investigate the association between salivary statherin, acidic proline-rich proteins (aPRP), and calcium with oral hygiene status.

Methods

One hundred and eighty-eight healthy subjects aged between 18 and 50 years with varying oral hygiene status who gave consent to participate were included in this cross-sectional study. The subjects were recruited from primary oral health care of MAHSA University. Oral hygiene of all the participants was measured using Oral Hygiene Index–Simplified (OHI-S). Stimulated saliva collected using paraffin wax was analyzed for salivary statherin, aPRP, and calcium. The relationship between salivary statherin, aPRP, and calcium levels with OHI-S was assessed using Spearman's Rank correlation coefficient; the strength of relationship was assessed by multiple linear regression analysis.

Results

The study found a weak positive correlation (r = 0.179, p = 0.014) between salivary statherin and OHI-S; weak negative correlation (r = −0.187, p = 0.010) between salivary aPRP and OHI-S; and moderate negative correlation between salivary statherin and salivary aPRP levels (r = −0.50, p < 0.001) which were statistically significant.

Conclusion

Poor oral hygiene is associated with increased statherin and reduced aPRP levels in saliva. Thus, these salivary components may have a role in predicting oral hygiene status.

Host genetics role in the pathogenesis of periodontal disease and caries

BACKGROUND

This study aimed to produce the latest summary of the evidence for association of host genetic variants contributing to both periodontal diseases and caries.

MATERIALS AND METHODS

Two systematic searches of the literature were conducted in Ovid Medline, Embase, LILACS and Cochrane Library for large candidate gene studies (CGS), systematic reviews and genome-wide association studies reporting data on host genetic variants and presence of periodontal disease and caries.

RESULTS

A total of 124 studies were included in the review (59 for the periodontitis outcome and 65 for the caries outcome), from an initial search of 15,487 titles. Gene variants associated with periodontitis were categorized based on strength of evidence and then compared with gene variants associated with caries. Several gene variants showed moderate to strong evidence of association with periodontitis, although none of them had also been associated with the caries trait.

CONCLUSIONS

Despite some potential aetiopathogenic similarities between periodontitis and caries, no genetic variants to date have clearly been associated with both diseases. Further studies or comparisons across studies with large sample size and clear phenotype definition could shed light into possible shared genetic risk factors for caries and periodontitis.

Salivary Protein Roles in Oral Health and as Predictors of Caries Risk

This work describes the current state of research on the potential relationship between protein content in human saliva and dental caries, which remains among the most common oral diseases and causes irreversible damage in the oral cavity. An understanding the whole saliva proteome in the oral cavity could serve as a prerequisite to obtaining insight into the etiology of tooth decay at early stages. To date, however, there is no comprehensive evidence showing that salivary proteins could serve as potential indicators for the early diagnosis of the risk factors causing dental caries. Therefore, proteomics indicates the promising direction of future investigations of such factors, including diagnosis and thus prevention in dental therapy.

Proteomic and bioinformatics analysis of human saliva for the dental-risk assessment

Background: Dental caries disease is a dynamic process with a multi-factorial etiology. It is manifested by demineralization of enamel followed by damage spreading into the tooth inner structure. Successful early diagnosis could identify caries-risk and improve dental screening, providing a baseline for evaluating personalized dental treatment and prevention strategies. Methodology: Salivary proteome of the whole unstimulated saliva (WUS) samples was assessed in caries-free and caries-susceptible individuals of older adolescent age with permanent dentition using a nano-HPLC and MALDI-TOF/TOF mass spectrometry. Results: 554 proteins in the caries-free and 695 proteins in the caries-susceptible group were identified. Assessment using bioinformatics tools and Gene Ontology (GO) term enrichment analysis revealed qualitative differences between these two proteomes. Members of the caries-susceptible group exhibited a branch of cytokine binding gene products responsible for the regulation of immune and inflammatory responses to infections. Inspection of molecular functions and biological processes of caries-susceptible saliva samples revealed significant categories predominantly related to the activity of proteolytic peptidases, and the regulation of metabolic and catabolic processes of carbohydrates. Conclusions: Proteomic analysis of the whole saliva revealed information about potential risk factors associated with the development of caries-susceptibility and provides a better understanding of tooth protection mechanisms.

Gene-environment Interactions in the Etiology of Dental Caries

Dental caries is a multifactorial disease that can be conceptualized as an interaction between genetic and environmental risk factors. The aim of this study is to examine the effects of AMELX, CA6, DEFB1, and TAS2R38 gene polymorphism and gene-environment interactions on caries etiology and susceptibility in adults. Genomic DNA was extracted from the buccal mucosa, and adults aged 20 to 60 y were placed into 1 of 2 groups: low caries risk (DMFT ≤ 5; n = 77) and high caries risk (DMFT ≥ 14; n = 77). The frequency of AMELX (+522), CA6 (T55M), DEFB1 (G-20A), and TAS2R38 (A49P) single-nucleotide polymorphisms was genotyped with the polymerase chain reaction-restriction fragment length polymorphism method. Environmental risk factors examined in the study included plaque amount, toothbrushing frequency, dietary intake between meals, saliva secretion rate, saliva buffer capacity, mutans streptococci counts, and lactobacilli counts. There was no difference between the caries risk groups in relation to AMELX (+522) polymorphism (χ(2) test, P > 0.05). The distribution of CA6 genotype and allele frequencies in the low caries risk group did not differ from the high caries risk group (χ(2) test, P > 0.05). Polymorphism of DEFB1 (G-20A) was positively associated, and TAS2R38 (A49P) negatively associated, with caries risk (χ(2) test, P = 0.000). There were significant differences between caries susceptibility and each environmental risk factor, except for the saliva secretion rate (Mann-Whitney U test, P = 0.000). Based on stepwise multiple linear regression analyses, dental plaque amount, lactobacilli count, age, and saliva buffer capacity, as well as DEFB1 (G-20A), TAS2R38 (A49P), and CA6 (T55M) gene polymorphism, explained a total of 87.8% of the variations in DMFT scores. It can be concluded that variation in CA6 (T55M), DEFB1 (G-20A), and TAS2R38 (A49P) may be associated with caries experience in Turkish adults with a high level of dental plaque, lactobacilli count, and age and when saliva buffer capacity is low.

Association of sweet taste receptor gene polymorphisms with dental caries experience in school children

Sweet taste is a powerful factor influencing food acceptance. The peripheral taste response to sugar is mediated by the TAS1R2/TAS1R3 taste receptors. The aim of the study was to determine the relationship between TAS1R2 (rs35874116 or rs9701796) and/or TAS1R3 (rs307355) single nucleotide polymorphisms with dental caries experience in schoolchildren. A total of 184 schoolchildren aged between 7 and 12 years (101 girls, 83 boys) were included in the study. Genomic DNA was extracted from saliva samples and the genotypes were identified by qPCR. The genotype frequencies were as follows: 6.6% for homozygous wild type, 41.8% for heterozygous and 51.6% for homozygous polymorphic genotype carriers of TAS1R2 gene rs35874116; 27.8% for heterozygous and 72.2% for homozygous polymorphic genotype carriers of TAS1R2 gene rs9701796, and 83.1% for homozygous wild type and 16.9% for heterozygous genotype carriers of TAS1R3 gene rs307355 polymorphism. A significant association was observed between total caries experience (dft + DMFT - decayed filled primary teeth + decayed, missing and filled permanent teeth) and TAS1R2 rs35874116 (p = 0.008) and TAS1R3 rs307355 (p = 0.04) gene polymorphisms but not for TAS1R2 gene rs9701796 polymorphism. TAS1R3 gene rs307355 polymorphism has been found to be an independent risk factor for dental caries experience by logistic regression analysis and to have increased the risk of caries. Moderate caries experience (4-7 caries) was found to be associated with TAS1R3 rs307355 heterozygous genotype, whereas high-risk caries experience (>8 caries) was found to be associated with TAS1R2 rs35874116 homozygous polymorphic genotype.

Salivary proline-rich proteins and gluten: Do structural similarities suggest a role in celiac disease?

PURPOSE

Gluten proteins, the culprits in celiac disease (CD), show striking similarities in primary structure with human salivary proline-rich proteins (PRPs). Both are enriched in proline and glutamine residues that often occur consecutively in their sequences. We investigated potential differences in the spectrum of salivary PRPs in health and CD.

EXPERIMENTAL DESIGN

Stimulated salivary secretions were collected from CD patients, patients with refractory CD, patients with gastrointestinal complaints but no CD, and healthy controls. PRP isoforms/peptides were characterized by anionic and SDS-PAGE, PCR, and LC-ESI-MS.

RESULTS

The gene frequencies of the acidic PRP isoforms PIF, Db, Pa, PRP1, and PRP2 did not differ between groups. At the protein level, PRPs peptides showed minor group differences, but these could not differentiate the CD and/or refractory CDs groups from the controls.

CONCLUSIONS AND CLINICAL RELEVANCE

This extensive study established that salivary PRPs, despite similarity to gluten proteins, show no apparent correlation with CD and thus will not serve as diagnostic markers for the disease. The structural basis for the tolerance to the gluten-like PRP proteins in CD is worthy of further exploration and may lead to the development of gluten-like analogs lacking immunogenicity that could be used therapeutically.

Caries: review of human genetics research

The NIH Consensus Development Program released a statement in 2001 (http://consensus.nih.gov/2001/2001DentalCaries115html.htm) and listed six major clinical caries research directions. One of these directions was the need for genetic studies to identify genes and genetic markers of diagnostic, prognostic and therapeutic value. This last decade has seen a steep increase in studies investigating the presence of genetic factors influencing individual susceptibility to caries. This review revisits recent caries human genetic studies and provides a perspective for future studies in order to fulfil their promise of revolutionizing our understanding of and the standard of care for the most prevalent bacteria-mediated non-contagious disease in the world.

MMP13 polymorphism decreases risk for dental caries

Recent evidence suggests that genetic studies may contribute to a better understanding of individual susceptibility to caries. Matrix metalloproteinases (MMPs) and their tissue inhibitors have been suggested to be involved in the caries process. The purpose of this study was to determine if polymorphisms in MMP2 (rs243865), MMP9 (rs17576), MMP13 (rs2252070), and TIMP2 (rs7501477) were associated with caries. Eligible unrelated children and adolescents were evaluated using a cross-sectional design. Data on oral health habits was obtained through a questionnaire and caries data was collected by clinical examination. Genotyping of the selected polymorphisms was carried out by real-time PCR. Allele and genotype frequencies were compared between individuals with and without caries experience. Of 505 subjects, 212 were caries-free and most subjects (61.2%) had mixed dentition. Allele frequency of MMP2, MMP13 and TIMP2 was different between caries-affected and caries-free individuals, with significant association for MMP13 (p = 0.004). Mutant allele carriers for MMP13 demonstrated a significantly decreased risk for caries (OR = 0.538, 95% CI 0.313-0.926); this result remained significant after adjustment for candidate genes, type of dentition and dietary factors. Allelic and genotype frequencies of the polymorphism in MMP9 were similar in caries-affected and caries-free individuals. Genetic variations in MMP13 may contribute to individual differences in caries susceptibility. Our findings reinforce that susceptibility to caries results from gene-environment interactions.

The scientific exploration of saliva in the post-proteomic era: from database back to basic function

The proteome of human saliva can be considered as being essentially completed. Diagnostic markers for a number of diseases have been identified among salivary proteins and peptides, taking advantage of saliva as an easy-to-obtain biological fluid. Yet, the majority of disease markers identified so far are serum components and not intrinsic proteins produced by the salivary glands. Furthermore, despite the fact that saliva is essential for protecting the oral integuments and dentition, little progress has been made in finding risk predictors in the salivary proteome for dental caries or periodontal disease. Since salivary proteins, and in particular the attached glycans, play an important role in interactions with the microbial world, the salivary glycoproteome and other post-translational modifications of salivary proteins need to be studied. Risk markers for microbial diseases, including dental caries, are likely to be discovered among the highly glycosylated major protein species in saliva. This review will attempt to raise new ideas and also point to under-researched areas that may hold promise for future applicability in oral diagnostics and prediction of oral disease.

Susceptibility to dental caries and the salivary proline-rich proteins

Early childhood caries affects 28% of children aged 2–6 in the US and is not decreasing. There is a well-recognized need to identify susceptible children at birth. Caries-free adults neutralize bacterial acids in dental biofilms better than adults with severe caries. Saliva contains acidic and basic proline-rich proteins (PRPs) which attach to oral streptococci. The PRPs are encoded within a small region of chromosome 12. An acidic PRP allele (Db) protects Caucasian children from caries but is more common in African Americans. Some basic PRP allelic phenotypes have a three-fold greater frequency in caries-free adults than in those with severe caries. Early childhood caries may associate with an absence of certain basic PRP alleles which bind oral streptococci, neutralize biofilm acids, and are in linkage disequilibrium with Db in Caucasians. The encoding of basic PRP alleles is updated and a new technology for genotyping them is described.

Streptococcus mutans strains recovered from caries-active or caries-free individuals differ in sensitivity to host antimicrobial peptides

Antimicrobial peptides (AMPs) are among the repertoire of host innate immune defenses. In the oral cavity, several AMPs are present in saliva and have antimicrobial activities against oral bacteria, including Streptococcus mutans, a primary etiological agent of dental caries. In this study, we hypothesized that unique S. mutans strains, as determined by DNA fingerprinting from sixty 13-year-old subjects with or without experience of caries, would have different susceptibilities to α-defensins-1-3 (HNP-1-3), β-defensins-2-3 (HBD-2-3) and LL-37. The salivary levels of these peptides in subjects were also measured by enzyme-linked immunosorbent assays. We found that S. mutans strains from children with active caries showed greater resistance to salivary HNP-1-2, HBD-2-3 and LL-37 at varying concentrations than those from caries-free subjects. In addition, combinations of these peptides increased their antimicrobial activity against S. mutans either additively or synergistically. The salivary levels of these peptides were highly variable among subjects with no correlation to host caries experience. However, the levels of a number of these peptides in saliva appeared to be positively correlated within an individual. Our findings suggest that the relative ability of S. mutans to resist host salivary AMPs may be considered a potential virulence factor for this species such that S. mutans strains that are more resistant to these peptides may have an ecological advantage to preferentially colonize within dental plaque and increase the risk of dental caries.

Resemblance of salivary protein profiles between children with early childhood caries and caries-free controls

Although prolonged bottle feeding with a carbohydrate-rich content is commonly agreed to be the main etiologic factor for early childhood caries (ECC), in recent years additional endogenous factors, including the composition of saliva, have been suspected as predisposing factors in children for the development of this aggressive form of dental caries. As a basis for investigating the putative involvement of salivary proteins in the etiology of ECC, a qualitative comparison of major salivary protein profiles between children with ECC and caries-free controls was performed. Saliva was collected from 30 children with ECC and, after separation by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, was compared with saliva from 20 caries-free controls for the general composition of proteins by means of silver staining, glycoprotein staining, and lectin blotting. Gels and blots were analysed using densitometry, and the protein-banding patterns resulting from the individuals' samples were compared by image analysis for the presence or absence of protein bands. Dendrograms obtained after comparison of all samples showed a high degree of similarity for the experimental groups. In summary, the results attest a uniform expression of the major protein components in children's saliva, regardless of the clinical manifestation of ECC, and thus pave the way for further detailed investigations of more subtle differences in the salivary proteome.

Correlations of oral bacterial arginine and urea catabolism with caries experience

BACKGROUND/AIM

Alkali generation by oral bacteria plays a key role in plaque pH homeostasis and may be a major impediment to the development of dental caries. To determine if the capacity of oral samples to produce ammonia from arginine or urea was related to caries experience, the arginine deiminase system (ADS) and urease activity in saliva and dental plaque samples were measured in 45 adult subjects.

METHODS

The subjects were divided into three groups according to caries status; 13 caries-free (CF) individuals (decayed, missing, and filled teeth = 0); 21 caries-active (CA) individuals (decayed teeth >or= 4); and 11 caries-experienced (CE) individuals (decayed teeth = 0; missing and filled teeth > 0). Real-time polymerase chain reaction was used to quantify the proportion of certain acid- or alkali-producing organisms in the samples.

RESULTS

The amount of ammonia generated from the test substrates by plaque samples was generally higher than that produced by salivary samples in all groups. Significantly higher levels of salivary ADS activity and plaque urease activity were observed in CF subjects compared to CA subjects (P = 0.0004 and P = 0.014, respectively). The proportions of Streptococcus mutans from saliva and dental plaque of CA subjects were significantly higher than those from the CF group (P = 0.0153 and P = 0.0009, respectively). In the CA group, there was an inverse relationship between urease activity and the levels of S. mutans (P < 0.0001).

CONCLUSION

This study supports the theory that increased caries risk is associated with reduced alkali-generating capacity of the bacteria colonizing the oral cavity; providing compelling evidence to further our understanding of oral alkali-generation in health and disease.

Enamel formation genes are associated with high caries experience in Turkish children

There is evidence for a genetic component in caries susceptibility, and studies in humans have suggested that variation in enamel formation genes and their interaction with Streptococcus mutans levels may contribute to caries. For the present study, we used DNA samples collected from 173 unrelated children from Istanbul: 91 children with 4 or more affected tooth surfaces and 82 caries-free children. Six single-nucleotide polymorphism markers were genotyped in selected candidate genes (ameloblastin, amelogenin, enamelin, tuftelin 1 and tuftelin interacting protein 11) that influence enamel formation. Allele and genotype frequencies were compared between groups with distinct caries experience. Regression analysis was used for the evaluation of individual gene effects, environmental effects and gene-environment interactions. Overrepresentation of the C allele of the amelogenin marker was seen in cases with dmft scores higher than 8 (p = 0.01) when compared to controls. Also, overrepresentation of the T allele of the ameloblastin marker was seen in cases with dmfs scores higher than 10 (p = 0.05) when compared to controls. In addition, the CT genotype of the tuftelin rs3790506 marker was overrepresented in cases with dmft scores higher than 5 (p = 0.05) and dmfs scores higher than 6 (p = 0.05) compared to controls. The best-fitting model showed that dmfs is increased when the following factors are present: (1) females and both the anterior and posterior teeth are affected simultaneously, (2) when the T allele of the tuftelin rs3790506 is involved, and (3) the C allele of the amelogenin rs17878486 is involved. Our study provides support that genes involved in enamel formation modify caries susceptibility in humans.