Monographs in Oral Science最新文献

In reality, most microorganisms are not free floating. They exist in biofilms, a community of many of them from the same species or from other genera and attached to surfaces.Microorganisms undergo a transition from free-floating, planktonic microorganisms to a sessile, surface-attached one. Contact with a surface induces changes in gene expression, and a strong attachment of microcolonies occurs only after a few hours. The maturation of a biofilm is associated with matrix formation. The matrix is of importance as it provides stability and protects against environmental insults, it consists of polysaccharides, water, lipids, proteins, and extracellular DNA. Biofilms can be found everywhere - in the environment, in water systems - and they play an important role in medicine and dentistry. In medicine, infections of chronic wounds, of the respiratory tract in cystic fibrosis infections, or when linked with incorporated biomaterial are mostly biofilm associated. In the oral cavity, the most prevalent oral diseases, dental caries, and periodontitis are multi-species biofilm-associated diseases. Although not acting alone, key pathogens drive the development of the microbial shift. Microorganisms metabolize sugar and create an acidic environment where aciduric bacteria (including mutans streptococci) become dominant, which leads to the demineralization of enamel and dentine. Porphyromonas gingivaliscauses biofilm dysbiosis in the development of periodontal disease. Biofilm-associated infections are extremely difficult to treat. The matrix serves as a barrier to antimicrobial agents and there are subpopulations of dormant bacteria resistant to antimicrobials requiring metabolically active cells. Approaches to treat biofilm-associated infections include the modification of the biofilm composition, inhibitors of quorum-sensing molecules, or interfering with matrix constituents.

The use of fluorides to address dental caries experience in populations was one of the biggest successes of public health in the twentieth century. The widespread use of fluorides also brought fluorosis to areas that otherwise would not be affected. This chapter briefly discusses the impact of fluorides on dental caries and amelogenesis and emphasizes the impact of fluorides on genes that are relevant to amelogenesis, dental caries, erosive tooth wear, and fluorosis.

Dental caries is a bacteria-mediated disease that inherently triggers a response from the host. The impact of this response is discussed in this chapter with a focus on genes involved in either the innate or the adaptive immune system. Since erosive tooth wear involves losses of structure not mediated by bacteria, the impact of the immune system is likely neglectable.

The study of twins is a powerful tool to infer the presence and amount of contribution of genetic variation to a particular trait or disease. The ability to compare identical or monozygotic twins with dizygotic twins permits the direct comparison of pairs of individuals that share 100% of their genomic DNA with pairs that share only 50%, with the assumption that these pairs are under the same environment. In the case of dental caries, the environment is same parents, under the same roof, with the same diet, oral hygiene habits, culture, and lifestyle. These data have consistently suggested that a relevant proportion of the variation of dental caries in populations is due to genetics.

Caries and inflammatory periodontal diseases have a high prevalence worldwide. Although improvements in oral health status in our patients have been shown, there is still an increased demand for preventive measurements - especially in view of the systemic influence of the chronic disease periodontitis. The main focus of such measurements lies on an optimal biofilm management which can be divided into professional biofilm management and home care measurements. Since home care mechanical measurements such as toothbrushing and interdental cleaning are often insufficient or not on a regular basis, they can be supported by antibacterial agents which are able to inhibit or kill any oral microorganisms that remain. Besides a proven effect on plaque bacteria and gingival inflammation, agents should have a high substantivity in the oral cavity that outlast the short rinsing period. This chapter aims to present the background and rationale of using antibacterial mouth rinses, their common agents, to show sensible indications, and to evaluate the scientific evidence of their additional effect over toothbrushing alone.

Untreated dental caries is the most prevalent disease worldwide. Development of caries is associated with the intake of sugar. The microorganisms utilize the sugar and create an acidic environment, which results in mineral loss. The appropriate use of fluoride is associated with a decline of caries. Another approach in preventing caries might be the increase of pH in dental plaque. During recent years, arginine has increasingly become the focus of interest. This is based on the fact that certain streptococci possess an arginine deiminase system (ADS) which metabolizes free arginine. In vivo, the incidence of caries was inversely correlated with ADS activity in saliva and dental plaque. ADS is highly active in Streptococcus gordonii and S. sanguinis, but is absent in S. sobrinus and S. mutans. In the presence of 1.5% L-arginine, S. gordonii and S. sanguinis, but not S. mutans and S. sobrinus, synthesize the metabolite citrulline and increase the pH of the environment.In defined multispecies biofilms consisting of ADS-positive and ADS-negative streptococci, supplementation with 1.5% arginine suppressed the growth of ADS-negative by favoring ADS-positive streptococci together with an increase in the pH of the environment. Evaluating the influence of daily manual removal of the biofilm in vitro by brushing with a commercial toothpaste containing fluoride and arginine resulted in less surface microhardness even when compared with a toothpaste with fluoride only. Recent studies clinically investigated the effect of using an arginine-containing dentifrice and reported a decrease of DMFS by about 10-20%.

When analyzing the activity of antimicrobial agents, it should be considered that microorganisms mainly occur in biofilms. Data obtained for planktonic bacteria cannot be transferred non-critically to biofilms. Biofilm models should consider both the relevant microorganisms and the conditions present in the environment. The selection of the model depends on the question to be answered. In dentistry, single species, multispecies, or microcosms originating from saliva or dental biofilm are used to culture biofilms. Microorganism selection depends on the focus of the study, for example caries biofilms mostly include Streptococcus mutans, an endodontic biofilm consists mostly of Enterococcus faecalis, and defined anaerobes are used in periodontal/peri-implant biofilms. In contrast to single-species biofilm models in medicine, where the lowest concentration of the antimicrobial that kills microorganisms is measured, the common analyzed variables are counts of colony-forming units or the percentage of dead bacteria determined by confocal laser scanning microscopy after applying a differentiating stain. All the models are helpful to evaluate new antimicrobial treatment options. Conclusions regarding the antimicrobial activity tendency of the therapeutics can be drawn. However, there are limitations of the model and ultimately a new therapy has to be proven in randomized controlled clinical trials.

The formation of the dental enamel is a consequence of a complex series of events and when disturbed, visible consequences ranging from hypoplasia to hypomineralization occur. Less dramatic alterations of the enamel structure and conformation are argued to modulate individual susceptibility to dental caries or erosive tooth wear. The effort to associate genes known to regulate dental enamel formation with dental caries experience has been carefully reviewed in the literature, and this chapter reflects on these studies from their conception standpoint, highlighting limitations in design, and adds a review to the work on erosive tooth wear.

The evidence for a genetic component to dental caries is in comparison much less explored in the literature than the other classically described components of the disease: microbiota and diet. Diet can be said to have been conclusively linked to the etiology of dental caries by the results of the Vipeholm study, which did not deal with any microbial aspect of the disease. What is much less emphasized is that these same results provided one of the most robust lines of evidence that exist in support of a genetic component to dental caries. The results of the study showed great variability, with some study participants showing a dramatic increase in the establishment of new carious lesions under conditions that did not affect the majority of the other subjects. Similarly, highly cariogenic conditions due to a diet rich in sugars did not cause an increase in new carious lesions in other participants. The best explanation for these variable results is the existence of individual biological factors (genetic variation) modulating the disease. This chapter also comments on the ethical controversy surrounding the study and the need for finally intervening on the effects of sugars in oral health.