Etiology and microbiology of periodontal diseases : A review

1 Food Science and Technology Department, Chemistry School, Coahuila Autonomus University, Blvd, V Carranza s/n, Col. Republica Oriente, Saltillo, Coahuila, CP 25280, Mexico. 2 Nanobioscience Group (UACOAH-CA-91), Chemistry School, Coahuila Autonomus University, Blvd. V Carranza s/n, Col. Republica Oriente. Saltillo, Coahuila. CP 25280, Mexico. 3 Dentistry School, Coahuila Autonomus University, Av. Cuquita Cepeda de Dávila s/n, Col. Adolfo López Mateos, CP 25125, Mexico.


INTRODUCTION
Periodontal disease and dental caries are the most prevalent infections affecting the human dentition (Brown et al., 1996).Periodontal disease is a chronic bacterial infection characterized by persistent inflammation, connective tissue breakdown and alveolar bone destruction (Yamamoto et al., 2011).The term periodontal disease refers to gingivitis and periodontitis as well.Gingivitis is a reversible dental plaque induced inflammation of the gingiva, is a common occurrence in children as young as 5 years old.
Periodontitis, which is bacterially induced, can be defined as a chronic inflammatory disease initiated by dental plaque biofilm and perpetuated by a deregulated immune response (Suvan et al., 2011) usually accompanied by gingivitis resulting in irreversible destruction of the supporting tissues surrounding the tooth, including the alveolar bone (Yamamoto et al., 2011).Periodontitis generally is defined as a condition where the supporting tissue of the teeth is destroyed (Reeves et al., 2006) and which leads to gingival recession (Saini et al., 2010), gingivitis (Lopez et al., 2005), loss of alveolar bone or teeth at the last stage of periodontal disease (Nesbitt et al., 2010), besides the loss of gingival collagen (LeRoy et al., 2010) and degradation of the periodontal ligament (Bonifait and Grenier, 2010).The hard and soft tissues of the oral cavity are colonized by bacterial biofilmscomposed by proteins epithelial cells, food residues, enzymes, plus different species of bacteria responsible for causing dental caries and periodontal disease (Bonifait and Grenier 2010).The gingiva, periodontium, alveolar bone and cement are structures that provide support to the tooth.Any pathological process affecting periodontum is defined as periodontitis.For a long time, it was thought that gingivitis and periodontal disease appeared as a result of aging of the periodontal tissues that gave rise to inflammation and recession of the gingival tissues bone and finally tooth loss.However, several studies have indicated that this is not just an adult disease, but also appears frequently in children (Escudero et al., 2008).
In latest research, 800-1,000 species that colonize the oral cavity were identified, nevertheless only about 50 species are strongly related to periodontal disease (Colombo et al., 2009).The metabolic action of early bacterial colonizers in the gingival crevice alters the environment and facilitates colonization by secondary organisms.These secondary colonizers are more pathogenic and when they exceed threshold levels, disease can occur, although, the presence of periodontopathic bacteria itself does not necessarily result in disease (Socransky and Haffajee, 2002).The concordance of a variety of bacterial virulence factors, the activity and composition of the commensal microbiota, and host immune factors, are required for the initiation of the disease process (Lamont and Jenkinson, 2010).
The objective of this review was to provide an overview of periodontal disease, as well as the microbiology aspects of this worldwide prevalent oral infection.

RISK FACTORS FOR PERIODONTAL DISEASE
Besides pathogenic microorganisms, genetic and environmental factors contribute to the development of this disease.The risk of periodontal disease increases with several factors as smoking, systemic diseases, medications such as steroids, antiepileptics, drugs for cancer therapy, poor placement of dental bridges, dental crowding, lack of teeth, pregnancy and contraceptive use.In addition to these factors, any health condition that triggers bacterial defense mechanisms such as human immunodeficiency virus (HIV), diabetes and neutrophils disorders can cause periodontal disease.The risk factors for periodontal disease are shown on Table 1.

MICROBIOLOGY OF PERIODONTAL DISEASE
Infectious diseases have in common, the fact that they are necessarily associated with the presence of bacteria that colonize the sub gingival niche (Escribano et al., 2005).The mouth facilitates the growth of a characteristic resident microbiota.The composition of the oral microbiota is influenced by temperature, pH and atmosphere, as well as by the host defences and host genetics (Marsh and Devine, 2011).The subgingival microbiota involved in periodontal disease has been a mayor research topic for more than 40 years (Contreras et al., 2000).
Recently, published studies show the association between certain families of virus and periodontal disease.Contreras et al. (2000) demonstrated the presence of some virus like Epstein-Barr type 1, cytomegalovirus and human herpes in crevicular fluid of Nigerian children with necrotizing ulcerative gingivitis.This pathogenicity is attributed to the degradation of the host defense mechanisms due to viral infection of the gingiva, favoring the bacteria colonization (Ling et al., 2004).In latest research, they identified 800-1,000 species that colonize the oral cavity, nevertheless only about 50 species are strongly related to periodontal disease (Colombo et al., 2009).However, a major portion of this species remains incompletely characterized, that is why their virulence and immunobiology are still unknown.
Bacteria are responsible for stimulating the host response, which define tissue changes causing periodontal lesions (Ling et al., 2004).Such bacteria are in communities within a glycocalyx forming a biofilm, which allows microorganisms to join and multiply on different surfaces (Lamont et al., 2013).The biofilm protects the microorganisms from toxic substances in the environment; it also facilitates the uptake of nutrients, the cross-feed, the elimination of metabolic products and the development of an appropriate environment with suitable physicochemical condition for their growth (Socransky and Haffajee, 2002).
Biofilms that colonize the oral cavity are among the most complex of nature, as in the mouth, there are 4 different niches: masticatory mucosa, tongue dorsum, saliva and hard surfaces such as tooth surfaces and restorative materials (Escribano et al., 2005).
Bacteria that cause periodontal disease can be classified according to their function in the associations between them when colonizing the gingival sulcus (Socransky and Haffajee, 2002).In Table 2, the Socransky classification is shown.
Microbiology related to periodontal disease has been a subject of discussion, although Lamont et al. (2013) identified specific bacteria related to gingivitis and periodontitis as shown in Table 3.Of all the bacteria forming biofilm, there are three that are particularly relevant in the initiation and progression of periodontal disease: Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg) and Tannerella forsythensis

Stress
Emotional and psychosocial stress can cause periodontal disease, although the precise role is still unknown.Silva et al., 1995;Hugoson et al., 2002 (Tf) (Sanz et al., 2000), this bacteria are designated major pathogens or "red complex" bacterias, as shown in Table 4.

Microbiological diagnosis
There are several methods developed for microbiological diagnosis in recent times.Which are shown in Table 5.

Treatment
Nowadays, periodontal disease has a variety of possible treatments depending on the stage of the disease, the way the patient respond to previews treatments and the patient oral health.Some of these treatments are: Professional dental cleaning, scaling and root planing, antibiotic therapy and surgical procedures.
Lately, the dental community was in search of new noninvasive treatments to restore oral health like the use of natural products such as plants; their components have been in use for treatment and cure of diseases all around the globe from ancient times much before the discovery of the current modern drugs (Dua et al., 2015).Hambire et al. (2015) tested 60 children of ages 9-14 with mouthwash of Camellia sinesis, obtaining as a result, an improvement in the children gingiva as well as the antiplaque effectiveness of this plant.Also, Hussain et al. (2015) demostrated in their in vitro test, the inhibition of three periodontopathic bacteria such as: Aggregatibacter actinomycetemcomitans, Prevotella intermedia and P. gingivalis with ethanolic extracts of Citrus sinesis, reporting a minimum inhibitory concentration of 12-15 mg/ml.
On the other hand, some researchers are interested in the application of phytomedicine as a possible treatment for dental decay and other oral health conditions.Jain et al. (2015) tested the antimicrobial activity of six plant extract against Streptococcus mutans, concluding that garlic, amla and ginger contains certain compounds that inhibit this cariogenic pathogen, reporting a zone of inhibition between 18.76-24.62mm.Ardakani et al. (2014) also tested mouthrinses of green tea against S. mutans, Streptococcus sanguis, Enterococcus faecalis, Pseudomonas aerogenosa and Escherichia coli, and obtaining a larger zone of growth inhibition with green tea   (Lamont et al., 2013).

-Porphyromona gingivalis -Tannerella forsythia -Treponema denticola -Campylobacter rectus -Fusobacterium nucleatum -Eikenella corrodens -Selenomonas noxia
Recently, Segura et al. (2015) reported that the extracts of Quercus rubra, Carya illinoinensis and Smilax glyciphylla with papin have an inhibitory effect on the dental biofilm formation, they also did an in vivo test with mouthrinses, proving once more the antibacterial activity of these extracts.

CONCLUSION
Periodontal disease is a worldwide health issue, but is particularly severe in individuals with low-income, mainly because they do not receive adequate dental care because of economic constrains and scarcity of affordable dental services.
The increasing evidence of the importance of periodontum health and its relation with other systemic diseases makes the dental community to develop safe and effective methods to control periodontal infections.pure extract than with 0.2% chlorhexidine.
Knowledge of basic periodontology, risk factors, classification and microbiology of periodontal disease are   -Inability to provide information on the sensitivity to antibiotics critical for a successful periodontal therapy.The recent advances in molecular diagnosis will hopefully give new tools for the oral microbiota study, leading to a better understanding of the initiation and progression of periodontal disease.

Method
Nowadays, the periodontal therapies mainly used are pocket debriment and the administration of antibiotics.However, some other equally effective treatments are being investigated lately, such as the phytomedicine.

Table 1 .
Risk factors for periodontal disease.

Table 3 .
Bacterial colonizers during gingivitis and periodontitis

Table 4 .
Main bacteria involved in periodontal disease.

Table 5 .
Main methods for microbiological diagnosis, pros and cons.