Complementary Experimental Methods in Genetics Open Up New Avenues of Research to Elucidate the Pathogenesis of Periodontitis.

A complex disease such as periodontitis is the sum of environmental and genetic effects. The personal genetic constitution interacts with the effects of internal and external risk factors like smoking, oral hygiene, malnutrition, emotional stress, and age. Accordingly, individuals who live in the same environmental context and share comparable lifestyle habits have different disease risks. Genetic research offers the identification of DNA sequence variants that have a causal role in disease etiology and allows the identification of disease relevant immune and metabolic pathways that contribute to disease susceptibility and pathogenesis in specific situations. Real advances have been made in genetic medical research in the last years. Starting from candidate gene association studies, new approaches were employed that have expanded the study design of genomewide association studies to genomewide meta-analyses and gene x environment interaction studies. Cost efficient whole-exome and whole-genome sequencing of patients with rare severe forms of periodontitis has the potential to identify genes and pathways with a direct role in the pathogenesis of common forms. In parallel, animal models were developed that use genetically highly diverse mouse lines to identify risk genes of human diseases. This chapter presents the main studies and the identified susceptibility genes that have clear statistical evidence. In addition, it describes pioneering studies that used advanced methods in experimental dental research, opening up new avenues of research. Although the knowledge of the genetic architecture of periodontitis is still in its infancy, genetic research is building the basis for future works with the potential to advance dental medicine in ways that will determine the various causes of periodontal diseases. This knowledge may eventually allow making predictions about disease risk for individual patients and leading to diagnosis and treatments that do not treat the symptoms but heal the disease.