TMKARPIŃSKI
ISSN: 2084-3577
PUBLISHER
Journal of Biology and Earth Sciences
MEDICINE
REVIEW
Microbiology of dental caries Tomasz M. Karpiński 1 , Anna K. Szkaradkiewicz2 1University 2University
of Medical Sciences in Poznań, Department of Medical Microbiology, Poznań, Poland
of Medical Sciences in Poznań, Department of Conservative Dentistry and Periodontology, Poznań, Poland
ABSTRACT
Dental caries is one of the most prevalent chronic diseases of people worldwide. The disease process may involve enamel, dentin and cement, causing decalcification of these tissues and disintegration of the organic substances. It is believed that bacteria of the species Streptococcus mutans is the main factor that initiates caries, and the bacteria of the genus Lactobacillus are important in further caries development, especially in the dentin. Caries can also be caused by other bacteria, including members of the mitis, anginosus and salivarius groups of streptococci, Enterococcus faecalis, Actinomyces naeslundii, A. viscosus, Rothia dentocariosa, Propionibacterium, Prevotella, Veillonella, Bifidobacterium and Scardovia.
Key words: Dental caries; Dental plaque; Streptococcus mutans; Streptococcus sobrinus; Lactobacillus. J Biol Earth Sci 201 3; 3(1 ): M21 -M24
Corresponding author:
Tomasz M. Karpiński University of Medical Sciences in Poznań Department of Medical Microbiology Wieniawskiego 3, str., 61 -71 2 Poznań, Poland e-mail:
[email protected] Original Submission: 09 February 201 3; Revised Submission: 06 March 201 3; Accepted: 08 March 201 3 Copyright © 201 3 Author(s). Journal of Biology and Earth Sciences © 201 3 Tomasz M. Karpiński. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
http://www.journals.tmkarpinski.com/index.php/jbes or http://jbes.strefa.pl e-mail:
[email protected] Journal of Biology and Earth Sciences, 201 3, Vol 3, Issue 1 , M21 -M24
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Karpiński & Szkaradkiewicz Microbiology of dental caries
INTRODUCTION Dental caries is a multifactorial, chronic bacterial disease, that causes demineralization and destruction of the hard tissues, usually by production of acid by bacterial fermentation of the food debris accumulated on the tooth surface. Today, caries remain one of the most common diseases of people worldwide. Individuals are susceptible to this disease throughout their lifetime. Worldwide, approximately 36% of the population have dental caries in their permanent teeth. In baby teeth it affects about 9% of the population [1 ]. Risk of caries includes physical, biological, environmental, behavioural and lifestyle-related factors [2].
REVIEW The essence of the teeth carious process is local demineralization of enamel, expressing in degradation of hydroxyapatites. This process is initiated within bacterial biofilm - dental plaque, that covers a tooth surface. Caries lesions develop where oral biofilms are allowed to mature and remain on teeth for long periods. On environmental acidification of the tooth, affects not only the number and species of bacteria, but also the release rate, viscosity and buffer capacity of saliva, the presence of fluoride in enamel and plaque, type of diet and the frequency of sugars consumption. Lowering the pH of the plaque below the "critical value" (5.5 to hydroxyapatite, 4.5 to fluoroapatite, 6.7 to cement) causes dissolution of calcium phosphates included in the hydroxyapatite and initializes loss of the tooth mineral substances [2, 3]. Over time the caries process may involve enamel, dentin and cement, causing decalcification of these tissues and disintegration of the organic substances. Caries progression can give rise to infection of the tooth pulp, which can spread to the supporting tissues and the jaws [3]. About 700 different bacteria species have been identified from the human oral microbiome [4]. In the pathogenesis of dental caries an important role play cariogenic bacteria, i.e. oral streptococci, especially of group mutans and lactic acid bacteria (Lactobacillus spp.). It is believed that bacteria of the species Streptococcus mutans is the main factor that initiates caries and very important factor of enamel decay. The bacteria of the genus
are important in further caries development, especially in the dentin. Mutans streptococci and lactobacilli are characterized by the ability to grow in an acid environment and the property of rapid metabolism of sugars supplied in the diet to organic acids, including lactic acid [5-7]. The microbial community from dentinal lesions is diverse and contains many facultatively- and obligately-anaerobic bacteria belonging to the genera Actinomyces, Bifidobacterium, Eubacterium, Lactobacillus, Parvimonas and Rothia. Streptococci are recovered less frequently [4]. Caries can also be caused by other bacteria, including members of the mitis, anginosus and salivarius groups of streptococci, Propionibacterium, Enterococcus faecalis and Scardovia [8-1 0]. In molecular studies using 1 6S rRNA analysis has been demonstrated, that the predominant microbes in deep caries lesions were S. mutans and genus Lactobacillus but also included the genera Prevotella, Selenomonas, Dialister, Fusobacterium, Bifidobacterium and Pseudoramibacter [11 , 1 2]. In studies of Becker et al. [1 3] and Aas et al. [1 4], they reported that genera associated with dental caries in both primary and permanent dentitions are Streptococcus including S. mutans, S. sanguinis and non-S. mutans streptococci, Veillonella, Actinomyces, Bifidobacterium, Lactobacillus, Propionibacterium, and Atopobium. In other study, has been shown that in plaque significantly associated with dental caries are the genera of Streptococcus, Veillonella, Actinomyces, Granulicatella, Leptotrichia and Thiomonas [1 5]. The development of the caries lesion is conditioned by the carbohydrates supply frequency, mainly sucrose and glucose from food, sometimes impact of cariogenic factors, as well as the tooth surface susceptibility. Recent studies confirm participation of the genetic factors in the pathogenesis of dental caries [1 6, 1 7]. Lactobacillus
Mutans streptococci
Mutans streptococci are the most cariogenic pathogens as they are highly acidogenic, producing short-chain acids which dissolve hard tissues of teeth. They metabolize sucrose to synthesize insoluble extracellular polysaccharides, which enhance their adherence to the tooth surface and encourage biofilm formation. The reactions are catalyzed by three isozymes of glucosyltransferases
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[1 8]. The most important mutans streptococci isolated from tooth caries samples are S. mutans and S. sobrinus. S. mutans is more cariogenic than S. sobrinus because specific cell-surface proteins, which aid in its primary attachment to the tooth. S. sobrinus lacks such proteins [1 9]. Streptococcus mutans S. mutans is able to
metabolise a number of sugars and glycosides such as glucose, fructose, sucrose, lactose, galactose, mannose, cellobiose, glucosides, trehalose, maltose and a previously unrecognised, group of sugar-alcohols. In the presence of extracellular glucose and sucrose, S. mutans synthesizes intracellular glycogen-like polysaccharides (IPSs) [20]. S. mutans produces also mutacins (bacteriocins), what is considered to be an important factor in the colonization and establishment of S. mutans in the dental biofilm [21 ]. Streptococcus sobrinus S. sobrinus has been
implicated in caries development particularly in instances where caries development appears to be independent of S. mutans. It is interesting that S. sobrinus displays higher acid production and acid tolerance compared to S. mutans [1 9, 22].
Lactobacilli
Among the Lactobacillus rods in the oral cavity occur: L. acidophilus, L. casei, L. fermentum, L. delbrueckii, L. plantarum, L. jensenii, L. brevis, L. salivarius and L. gasseri. Lactobacilli are divided into two main groups: - homofermentative which in the fermentation process of glucose produce mainly lactic acid, e.g. Lactobacillus casei, Lactobacillus acidophilus, - heterofermentative which in addition to lactic acid produce acetate, ethanol and carbon dioxide, e.g. Lactobacillus fermentum [23, 24]. Lactobacilli are isolated from deep caries lesions but rarely just before the development of dental caries and in the early tooth decay. It is believed that they are pioneering microorganisms in the caries progress, especially in dentin [6]. Studies have shown that Lactobacilli are a dominant part of the flora inhabiting the deep cavities, and their number correlates with the amount of carbohydrates [25-27]. Recently it is known that lactobacilli demonstrate
also antagonistic action against periodontopathogens such as Aggregatibacter actinomycetem comitans, Prevotella intermedia and Porphyro monas gingivalis, inhibiting their growth [28-30]. This action consists in the production of acids mainly lactic acid, lowering the pH of the environment, release of hydrogen peroxide [31 , 32] and bacteriocins [33-35]. Thus, Lactobacillus in addition to a cariogenic activity also play a key role in maintaining the microecological balance in the mouth and gastrointestinal tract.
CONCLUSIONS Dental caries is one of the most prevalent diseases in the world, that causes demineralization and destruction of the hard tissues of teeth. In the development of caries a major role play bacteria of the Streptococcus and Lactobacillus genera which are acidogenic and aciduric. At the same time, recent studies show that in the dental caries development may also affect other bacteria.
TRANSPARENCY DECLARATION The authors declare no conflicts of interest.
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