ABSTRACTBackground and objectives A link between the occurrence of periodontitis and zincdeficiency has been suggested. The aim of this study was to evaluate the effect of zincsupplementation on periodontal status in patients with type 2 diabetes mellitus.Methods Three hundred diabetic patients with chronic periodontitis (age range 45-65 yearsold) were selected. The patients divided into three groups as I :zinc supplement; II: scalingand polishing; III: zinc plus scaling and polishing. At initial visit, the blood samples of allpatients collected and analyzed for serum zinc and glucose. Periodontal status of the patientsbased on clinical attachment loss and probing pocket depth score was determined. Thepatients in group I and group III were assigned to receive 50 mg elemental zinc three times aday for six months period. Periodontal status reassessed after intervention following the sameprocedure.Results At initial, there were no significant differences in any parameter between the threegroups. At the end of the 6 months period, the mean values of clinical attachment loss andprobing pocket depth scores were significantly lower among group III as compared to groupII (P<0.01). The percentage of change in clinical attachment loss and probing pocket depthwere significantly higher in the group III as compared to group II ( p<0.05).Conclusion Zinc supplement for vulnerable population to low zinc status such as type 2diabetes mellitus patients decreases the chance of the occurrence of severe periodontitis.