Conventional and natural products against oral infections

In 1674, the Netherlander Antony van Leeuwenhoek (1632 1723), recognized as the discoverer of the microorganisms, created a device composed by plates of metal and lens, like a microscope, where he observed from human saliva, teeth and faeces, little movable objects, invisible through the naked eyes, that he called “animalcule” [1]. The oral cavity is an environment highly infected by commensal microorganisms that, initially, play the role of protection of the mucosa. The “resident” microbiota cohabits in a harmonic relationship with the host, as a beneficial infection and as a local host defense, since it makes difficult the implantation of pathogenic species, strange for this microbiota. This resident microbiota can become pathogenic when the host conditions are changed or the harmonic equilibrium is broken [2]. Due to the existence of teeth and periodontal spaces, the oral cavity shows many different ecological sites with peculiar environmental characteristics. The oral microbiota is the most complex inside the human, with more than 30 different genders of bacteria and more than 700 species. There are approximately 350 bacterial cultivable species and more than 200 species identified only by molecular techniques. The total number of oral microorganisms is similar to the intestinal microbiota besides more complex about the number of species [3, 4, 5]. However, the accumulation of the microbial biofilms can develop some diseases. Beyond the bacteria, other microorganisms such as virus and fungi can also colonize and induce oral diseases. The oral infections own specific characteristics, with a predominantly strict anaerobic and/or facultative microbiota, with propitious surfaces for adhesion and suitable nutrients. These microorganisms organize themselves quickly into biofilms, from initial adhesion to the dental enamel surface, gingival epithelium, tongue and mucosa, once they are flooded by saliva. Saliva contains proteins that can favor the molecular adsorption. Some species possess receptors or produce polysaccharides that can facilitate the adhesion and start the multiplication process. The nutrients come from saliva, accumulated food and gingival fluid [3, 5, 6, 7]. In addition, the oral microorganisms have to compete for sites where the receptors are already occupied by initial colonizers, deal with the positive and negative relationships among other microorganisms, resist to host defenses and possess some virulence factors [2, 8]. At the intrauterine life, the mouth is free of microorganisms. Some hours after the birth, the infection starts, with microorganisms coming from people in a strait contact with the baby, especially the mother, as a vertical infection. The facultative anaerobic bacteria are the most adaptable to the new mucosa, mainly the genus Streptococcus. When the teeth appear, new ecological sites are created and the oral microbiota develops more complex and intensely [3, 9]. The most prevalent species capable to adhere to the teeth surfaces are facultative anaerobic species as S. sanguinis, S. gordonii and S. oralis, in addition to some species of Actinomyces. Interproximal areas, enamel grooves and cracks provide conditions for the development of strict anaerobic bacteria. The gingival groove is a niche with very low content of oxygenation and it is conducive to installation of these anaerobes. The toothed adult man can have until 10 bacterial cells per mL of saliva and 10 cell per gram of dental biofilm [3, 5]. Bacteria can adhere to the dental surface directly or to other initial colonizers by means of adesins and fimbriae. Some Gram-negative periodontopathogens are not able to adhere to the teeth, however, they have adherence binders toward to the periodontal pocket epithelium and/or to the initial colonizers [4, 8]. Saliva is responsible for the regulation of the supragengival microbiota, since it offers to the adhered microorganisms suitable temperature, pH, and humidity, in addition to some nutrients as proteins, amino acids, carbohydrates, vitamins and inorganic compounds. On the other side, saliva possess antibodies, antimicrobial substances and enzymes as lysozime and lactoferrin, pH stabilization system and a mechanical drag action due to the salivary flux. This salivary flux is increased during the speech and chewing, what is favorable to the removal of bigger accumulation of microorganisms. In spite of, during the sleep, this flux is greatly reduced, promoting the accumulation of biofilms and maintaining the acid pH [2,10]. The gingival fluid also helps to regulate the subgingival microbiota. Since the biofilm accumulation increases, the inflammatory response develops and the gingival exudate increases too. This fluid possesses many host defense factors as cells and the complement, however, is a great source of nutrients for anaerobic bacteria as proteins, hemin, k vitamin and hormones [3, 4]. Other factors that can promote the oral microorganism accumulation are cavities, inadequate restorations, prosthesis, crowding, orthodontic devices, epithelium loss, and in a more effective way, the systemic condition of the host, the diet and the quality of oral hygiene [3, 11]. Microbial pathogens and strategies for combating them: science, technology and education (A. Mendez-Vilas, Ed.)