Genetic association study has been progressed in medicine along with advance in genetic technology. It focused on the individual differences in genotype due to errors occurring during DNA duplication, which can cause vulnerability to specific diseases. Polymorphism defines the varieties in phenotype due to those genetic variations. Polymorphism due to change in one DNA base sequence is called as a Single Nucleotide Polymorphism. In the near future, the evaluation of relative risk to specific disease according to SNP will be essential part of fundamental of medicine for the diagnosis, treatment and prevention. Dental caries and periodontal diseases has been first subject to genetic association study in dentistry and broaden out to other areas like bone formation and resorption. This article presents the current state of genetic association study and its application to dentistry.