The use of substances that inhibit root resorption may be an alternative for cases of unsuccessful reimplants. Hence, the purpose of this study was to test a solution of acetazolamide, a resorption inhibitor, as an intracanal therapeutic agent for late reimplanted teeth. Thirty rat maxillary right central incisors were avulsed and kept dry for 30 min. The teeth were instrumented, and the root surfaces treated with 1% hypochlorite solution followed by application of 2% sodium fluoride. Thereafter, the teeth were divided into two groups according to the intracanal dressing: Group I, solution of acetazolamide and Group II, calcium hydroxide paste. Teeth were then reimplanted in their respective sockets. The animals were killed at 15, 30, and 60 days after reimplantation and the samples processed for morphometric and microscopic analysis. The results showed that calcium hydroxide paste limited root resorption, even though not avoiding it. In contrast, no root resorption was observed after 60 days in the acetazolamide group, confirming the efficacy of the substance in inhibiting root resorption.