OBJECTIVETo observe the changes in subgingival microflora before and after Er:YAG laser treatment on diabetic patients with periodontitis, and to compare with the subgingival microflora of chronic periodontitis.

METHODSSubgingival plaque of 13 pairs of teeth (26 sites) was selected from type 2 diabetic patients at pretreatment, one month post-treatment, and three months post-treatment. Subgingival plaque was also obtained from 11 cases of moderate to severe chronic periodontitis with similar severity of periodontitis. The DNA of the subgingival plaque samples was extracted. Whole bacterial 16S rDNA gene fragments separated by denaturing gradient gel electrophoresis. Specific DNA bands were then chosen for retrieval and sequencing.

RESULTSThe gene sequencing results of the special DNA bands of subgingival plaque samples show that the pathogenic bacteria of both diabetic periodontitis and simple chronic periodontitis were Prevotella intermedia and Tannerella forsythia, respectively. The composition of the subgingival microflora before and after laser treatment changed. Some DNA bands, including that of Tannerella forsythia, disappeared or weakened one month after treatment. A new strip appeared, which belonged to Actinomyces sp.

CONCLUSIONThe profiles of the subgingival microflora changed after treatment, and one month was indicated as an important stage. Er:YAG laser may have an important function in delaying microflora recolonization.