Teeth are the only mineralized partially tissues exposed to the external environment, and they have a suitable surface for the development of a biofilm, a thin layer of bacteria, proteins, glucides and water that represents an ideal medium for many bacterial species. So a biofilms can have several bacterial species causing a bacterial plaque, then the proliferation leads to the formation of tartar, removed only with a professional intervention in a dentist's study. Periodontal disease refers to a group of inflammatory conditions that affect tooth supporting tissues resulting from a plaque stockpile; generally there are two forms of the periodontal disease: gingivitis and periodontitis. The first is a reversible inflammation limited to a periodontal gingival tissues, so it not causes a loss of attachment, while periodontitis is a group of inflammatory conditions causing an irreversible tissue destruction of tooth support. To this day periodontitis is considered a multifactorial disease that arises from the interaction between genetic and environmental factors as bacterial infections, inflammatory response, smoking, age, sex, aging and unstable socio-economic conditions (Stabholz et al. 2010). At least 10-15% of the population is affected.
Periodontal disease is divided into different categories (Armitage 1999): gumboild disease, chronic periodontitis, aggressive periodontitis, periodontitis as a manifestation of systemic diseases, necrotizing periodontal infections.
Inflammation is a response to pathogens, to free the body from each entity to generate cellular damage (microorganisms, toxins, etc.) or from the effects of the damage (death cells, necrotic tissue).
A key role in the regulation during the inflammatory process is played by protein called cytokines. There are cytokines that play a proinflammatory function, to promote and sustain inflammation, such as some types of interleukins (IL-1, IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha); others play an anti-inflammatory function, like interleukin 10 (IL-10). If a regulatory mechanism is altered, the inflammation prolongs becoming harmful, since the pro-inflammatory cytokines cause a persistent over-activation of osteoclasts, cells responsible for bone absorption, so there is a massive tissue loss that leads to periodontitis.
Several studies have shown that in the encoding cytokines genes there are single
nucleotide polymorphisms (SNPs), which could alter the gene expression and then the effects on the inflammatory process. In the TNF-alpha gene promoter there is a polymorphism: if it is present in the variant A causes the TNF-alpha production, increasing the risk of onset of chronic periodontitis (Ianni et al. 2013; Hu et al. 2011; Erciyas et al. 2010). A polymorphism in the gene IL 6 is related to increased levels of Interleukin 6 and then, for carrier individuals (homozygous DD) there is an increased risk of periodontitis, especially in aggressive form (Shao et al. 2009; Nibali et al. 2009; Moreira et al. 2007; Wohlfahrt et al. 2006; Holla et al. 2004; Trevilatto et al. 2003).
Other studies have shown the association of two polymorphisms of IL-1b gene with the increased risk of chronic periodontitis (Wu X et al. 2014; Deng et al. 2013; Karimbux et al. 2012; Nikolopoulos et al. 2008). The downregulation of the inflammatory process could happen even if the production of anti-inflammatory interleukins is altered; case-control studies and meta-analysis (Chambrone et al. 2014; Ianni et al. 2013; Zhong et al. 2012; Jaradat et al. 2012; Albuquerque et al. 2012; Atanasovska-Stojanovska et al. 2012; Cullinan et al. 2008) showed that the polymorphisms in IL-10 gene cause a decrease of the interleukin 10 synthesis, so the inflammatory process persists and it increases the risk of chronic periodontitis. The genetic test in periodontal disease is important for:
1. screening in the young people with predisposition to periodontal disease, with a development of prevention protocols;
2. treatment plan optimization in patients who have already developed the disease,
thanks to the integration of clinical information with objective data provided by the test;
3. evaluation of risk of periodontitis development for implant failure in patients who undergo implant-prosthesis rehabilitation;
4. improvement of patient’s compliance, who properly informed about its staff profile,
will cling more aware to a prevention plan;
5. acquisition of objective data to develop a periodontal maintenance and implant plan.
Pathogenic bacteria organized in biofilms (plaque) acts with colonization strategies in complex, recently reclassified according to Socransky (2008). Some bacteria species in the oral cavity (Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Treponema denticola) trigger the disease (Feng et al. 2006). In the
diagnosis and prognosis of the parodontal disease is important to indentify the principal pathogen species involved in the specific forms of patodontitis; it was demonstrated a strong correlation between clinical gingival inflammation parameters and a microbiological profile.
The genetic predisposition test and the microbiologic test can be performed separately,
each one. For each of the two, the results are available after 10-12 days from arrival of the sample in our lab.
For the genetic test: DNA extracted from buccal mucosa cells picked with a cotton swab
or cytobrush; alternatively, DNA extracted from peripheral blood lymphocytes collected by
a withdrawal in tubes with EDTA (both types of sampling can be performed in our Center).
For microbiological tests: DNA extracted from gingival material collected through a special
"cone of paper" by a specialist dentist.