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Periodontitis is a multicausal disease, with each of the causal factors playing a role but the relative contribution of these vary from case to case.
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The disease behaves in a nonlinear fashion, with periods of aberrant host response and periods of a disease resolving state.
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To date only a few of the multitude of possible genetic factors for periodontitis have been identified.
What is the Contribution of Genetics to Periodontal Risk?
Section snippets
Key points
Periodontitis is a complex disease
The current concept of the etiology of periodontitis is that it is a complex disease. Complexity of periodontitis means that it is a process involving multiple causal components,10, 11 which interplay with each other simultaneously. Complex systems are almost always nonlinear. Nonlinearity in complex systems means that the causes and effects are disproportional so that a small cause may result in a large effect or a large cause may result in a small effect, and that the disease progression rate
Periodontitis development and progression
The bacteria in the subgingival biofilms, as well as their toxic and antigenic products (eg, endotoxin, bacterial metabolic components), initiate the inflammatory reactions that recruit polymorphonuclear neutrophilic granulocytes (PMN) and other inflammatory cells into the gingival tissues.27 Subsequently, the recruited immune cells, in particular PMNs, but also activated pocket epithelial cells and fibroblasts in the underlying matrix, release proinflammatory mediators, including cytokines,
Some theoretic background on genetics
Hundreds of thousands genetic loci can be identified in the human genome (ie, the complete set of chromosomes). These are stretches of DNA on the chromosomes with an order, with a start and an end. Many of these genetic regions do not contain a gene proper (a genetic region coding for a protein), rather just regulatory elements or DNA with unknown function (originally called “junk DNA”). There are some 20,000 to 30,000 genetic loci that do contain one or several genes coding for proteins and
Candidate Gene Approach
In general, the genetic loci and the known genetic polymorphisms occurring in such loci, are chosen for candidate gene association studies in periodontitis based on their relation with immune responses and/or have previously been associated with other chronic inflammatory diseases, such as rheumatoid arthritis, cardiovascular disease, Crohn disease (CD), type 2 diabetes, and systemic lupus erythematosus. The overlapping genetic risk factors for common chronic inflammatory diseases is called
The best replicated and validated genetic factors for periodontitis
We have ordered the results from the literature per chromosome.
Discussion and conclusions
Periodontitis has a multicausal etiology, in which genetic factors play a role. The various proposed causes for periodontitis work simultaneously, but the relative contribution of each of these varies from case to case. In young individuals often with AgP, a stronger contribution from genetic factors is apparent, whereas in older individuals often with CP, the relative contribution of the established subgingival biofilms (environmental factors) and lifestyle factors (eg, smoking, stress, diet)
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Authors B.G. Loos and M.L. Laine are supported in part by a grant from the University of Amsterdam, the Netherlands, for the focal point ‘Oral infection and inflammation’.
Disclosures: No potential conflicts of interests relevant to this review are reported.