**4. Epigenetic modifications**

Epigenetic modifications such as DNA methylation, histone modifications and RNA-associated silencing (micro RNA) play a role in susceptibility to disease. These modifications express or repress certain genes.

Loo et al. in their study showed that methylation of E-Cadherin and COX-2 was observed in periodontitis patients. Nahid et al. demonstrated the expression of miR-146a in infections caused by periodontopathic bacteria. Park et al. in their study observed that miRNA-132 played a major role in pathogenesis induced by P. Gingivalis. Several studies have reported the influence of various microRNAs especially miR-146a, let-7a, miR-196a, miR-499a, and miR-125a in susceptibility to

**45**

*Genetic Biomarkers in Periodontal Disease Diagnosis DOI: http://dx.doi.org/10.5772/intechopen.88058*

in south Indian population [30].

tion with host genetic variants [31, 32].

etiopathogenesis of periodontitis.

Gurumoorthy Kaarthikeyan\* and Swarna Meenakshi

\*Address all correspondence to: drkarthik79@yahoo.co.in

provided the original work is properly cited.

Department of Periodontics, Saveetha Dental College and Hospitals, Saveetha

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Institute of Medical and Technical Sciences (SIMATS), Chennai, India

**5. Infectogenomics**

**6. Conclusion**

**Author details**

chronic periodontitis [27–29]. Priyanka et al. in their study have found association of microRNA-125a and microRNA-499a polymorphisms with chronic periodontitis

Infectogenomics refers to the association of the host genetic variants like single nucleotide polymorphisms with the composition of the microbial complexes in the host body. The recent meta-analysis by Nibali et al. has shown an association of 13 host genetic variants with the red/orange complex bacteria in periodontitis. The study by Divaris et al. has shown an association of two genetic loci (KCNK1 and DAB2IP) with high colonization of red complex bacteria. A more detailed knowledge of the human oral microbiome could provide more information on its associa-

Although there are several studies that associate various candidate gene polymorphisms to periodontitis, till date there is not much clarity in the genetic susceptibility to the disease since there are a multitude of etiological factors and epigenetic factors that contribute to the susceptibility as well as severity of periodontal disease. Future research should focus on the multitude of genes, their multiple interactions and the epigenetic regulation during different stages of periodontal disease pathogenesis is required to fully understand the molecular mechanisms behind the

chronic periodontitis [27–29]. Priyanka et al. in their study have found association of microRNA-125a and microRNA-499a polymorphisms with chronic periodontitis in south Indian population [30].
