Evaluation of Ki-67 Antigen and Protein P53 Expression in Orthokratinized and Parakratinized Odontogenic Keratocyst

Statement of Problem: Odontogenic Keratocysts (OKC) make up 10-12% of all developmental cysts with dental origin. OKCs are classified into parakeratotic and orthokeratotic types, with completely different clinical features. In order to investigate biological behavior of OKCs, an immunohistochemical study was designed, using Ki-67 antigen as proliferation marker and P53 protein as tumor suppressor gene. Purposes: The aim of the present study was to investigate the expression of P53 and Ki-67 markers in two types of OKCs and to determine their relationship with the biological behaviour of OKC. Materials and Methods: A total of 20 OKCs (parakeratotic n=10, orthokeratotic n=10) were stained immunohistochemically for Ki-67 and P53 protein by Biotin – Streptavidine method. Then, slides were studied quantitatively through optical lense (magnification=X10) and the number of positively stained cells was counted/mm BM. Results: The average number of Positively stained cells for Ki-67 were 62.30±11.96 cells/mm BM in parakeratotic, and 29.90±4.90 cells/mmBM in orthokeratotic OKCs (P<0.05). Positive cells for Ki-67 were dominantly located in parabasal layer. Mean stained cells for P53 were 4.30± 2.21cells/mmBM in parakeratinized and 4.80±1.75 cells/mmBM in orthokeratotic types that was not statistically significant. (P<0.58) Parakeratotic OKCs mostly occur in the lower jaw (90%), whereas just 50% of orthokeratotic OKCs occur in mandible (P=0.05) Conclusion: Regarding other clinical features and the existence of daughter cysts, no significant statistical difference was found between two types of OKCs.