Background: Mast cells are initiating immune response and acting as first line of host defense against bacterial and parasitic infection . They are known to play an important role in allergic reaction, local homeostasis, inflammation and angiogenesis.

  Objective: The aim of the present study was to evaluate the association between mast cell count and chronic periodontitis.

  Methods: This case-control study was conducted on subjects referred to dentistry centers in Qazvin from 2004 to 2005. Periodontal parameters including probing depth, clinical attachment level, bleeding on probing, gingival and plaque indices were measured. Gingival specimens from 20 moderate to advanced chronic periodontitis sites (case group) and 18 healthy/ gingivitis sites (control group) in routine periodontal surgeries (flap and crown lengthening) were prepared. The specimens were examined after toluidine-blue staining for mast cells and Hematoxylin and Eosin staining for histological assessment of the inflammation. Mast cell counting and inflammation grading was performed 3 times by 2 observers in 5 micron length sections, using light microscope at 100 and 400 magnifications. Data were analyzed by T - test and ANOVA .

  Findings: Mast cell count were 34.5±23.1 in case group and 13±9.8 in control group and the difference was statistically significant (P=0.001). In small grades of pathologic inflammation, mast cell count were 42.2±33.2 in case group and 8.4+5.4 in control group and the difference was statistically significant (P=0.04) as well. There was no relationship in high grades of inflammation.

  Conclusion: The present study indicates that mast cell numbers in chronic periodontitis sites are more than healthy or gingivitis sites. The results of this study suggest more studies to clarify the role of mast cells in the pathogenesis of chronic periodontitis and also to evaluate the dynamic aspects of host defense simultaneously with other aspects of immune system.