The aim of the present work is to study the effect of different formulations of Ca (OH)₂ on healing of induced periapical lesions in dog. A total of 96 teeth with intentionally induced periapical lesions were classified according to the observation period into three groups; I, II and III (2 dogs each).  Each group was subdivided into four subgroups (8 teeth each) namely; A, B, C and D which were dressed with Ca(OH)₂ with saline, Ca(OH)₂ with chlrohexidine, Ca(OH)₂ with iodoform and control respectively. Histopathological findings showed that the apical and periapical repair were better in subgroup A than in other subgroups in all groups. Total inflammatory cell count was significantly different between the four subgroups in group I. In both groups II and III, there was no significant difference between subgroups B and C. In conclusion, the use of saline as a vehicle for Ca (OH)₂ has a favorable action on periapical tissue healing in endodontically treated dogs.

Key words: Calcium Hydroxide, Chlorohexidine, Dogs, Iodoform, Periapical Tissue, Saline