Epidemiology of dental caries: from prevention to the relationship with helicobacter pylori infection

Oral diseases, such as dental caries and periodontal diseases, are the most prevalent worldwide nowadays. The World Health Organization (WHO) considers these pathologies important public health issues. It is fundamental to focus on the oral health, since oral diseases can cause problems related to difficulties in chewing, food intake, learning and concentration, sleep and reduced quality of life during childhood and adolescence. Oral health is a medical field in constant development, both in Portugal and in the rest of the world. Therefore, it is important to know the various aspects of research that can be performed in this specific public health domain. The complementarity between the epidemiological and laboratory research is a current reality and it is essential to investigate and assess important public health problems related to oral health and even to allow the improvement of biomaterials aiming at the prevention of oral diseases. The developed doctoral work plan consisted in: 1) assessing the prevalence of dental caries and the distribution pattern of fissure sealants; 2) evaluating the presence of Helicobacter pylori (H. pylori) in the oral cavity to determine if there is any association between H. pylori infection, socio-demographic variables and the prevalence of dental caries; 3) investigating the prevalence of salivary Streptococcus mutans (S. mutans), Lactobacillus and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) and their influence on the risk of dental caries development and also their association with socio-demographic factors; 4) evaluating the effectiveness of incorporating an antibacterial agent (silver diamine fluoride) in a resin-based fissure sealant to inhibit the growth of S. mutans; 5) describing different strategies that can foster the development of appropriate oral health promotion programs, at a community and individual levels. For the epidemiological approach an observational cross-sectional study was conducted with a non-probabilistic convenience sample of 447 adolescents, aged 12 to 18 years old, who attended a public school in Sátão, Portugal. Data collection was accomplished through a questionnaire that was answered by the adolescents in the classroom followed by an intra-oral observation, saliva collection and, finally, H. pylori infection detection using the Urease Breath Test (UBT). The bacterial strains in the saliva were identified using the Polymerase Chain Reaction technique (PCR). Simultaneously, an in vitro study was performed to check if the incorporation of silver diamine fluoride in a resin-based fissure sealant had an inhibitory effect on a bacterial strain S. mutans. This study demonstrated that there was a moderate level of prevalence of dental caries, with a higher number of filled teeth in comparison with the number of decayed and missing teeth due to dental caries. This indicates that most adolescents are having dental appointments during their lives, at least for the treatment of dental caries. These results demonstrate the improvement of oral health registered in Portugal, since children and adolescents have easier and a more regular access to dental appointments. The prevalence of H. pylori present in saliva was very low in the sample of adolescents analyzed. One possible explanation may be correlated with the absence of gastric pathology. In contrast, other studies where adult samples were used demonstrated a clear diagnosis of gastric pathology associated with H. pylori infection. The observed differences in the prevalence of oral H. pylori can also be justified by the different methodologies / techniques applied in the previous studies to detect this bacteria. In the present study salivary detection of H. pylori was performed by identifying the specific gene of H. pylori, vacuolating citotoxin gene A (vacA), whereas in previous studies the presence of the bacterial strain was determined based on the urea content which is also produced by other bacterial strains in the oral cavity. Furthermore, the influence of oral microflora in the oral health of adolescents was also studied. The high diversity of oral microflora requires a fully characterization in order to understand the oral ecosystem. Such knowledge is crucial to know the etiology of dental caries and suggest new therapeutic targets to treat the disease. In this study no direct association was found between bacterial strains and dental caries. However, the presence of A. actinomycetemcomitans was noticed to be associated with socio-demographic factors, such as the age and residence area of adolescents. These results can be considered important because they can allow the detection, at an earlier stage, of a potential bacterial strain that originates a periodontal disease that will arise in adulthood. The requirement to improve biomaterials applied in dental medicine is also essential to prevent the beginning and development of oral diseases. With this idea in mind, we developed a laboratorial approach, with the main goal of demonstrating at an early stage, the possibility of enhancing the antibacterial effect of a biomaterial used in the primary prevention, in this case, a resin-based fissure sealant. In this study, considering the proven clinical application of silver diamine fluoride (SDF) in the significant inhibition of S. mutans, its incorporation into the fissure sealant proved to be a possible association that may enhance the antibacterial effect of the same fissure sealant, and avoid the development of dental caries in the presence of infiltration or partial loss of a fissure sealant. The last part of the study presented in this thesis shows the need to implement community-oriented oral health promotion programs, which must be considered and developed in order to improve the knowledge and behaviors related to oral health of children, adolescents, parents, teachers and health professionals. Primary prevention should be taken into account to reduce the risk of oral disease development, primarily by significantly improving population’s oral health behaviors. The research described in this PhD thesis gives the scientific community the opportunity to analyze various issues, such as: epidemiology of oral diseases and primary prevention methods; characterization of the oral microflora and associated environmental factors that can influence oral health; influence of H. pylori bacterial strain on oral health; new applications that can be assigned to biomaterials used in dental medicine with a view to improving clinical outcomes in the future; and description of oral health educational strategies to improve health behaviors and reduce the incidence of oral diseases.