SummaryCalcium hydroxide has been advocated for use in avulsed teeth as a temporary dressing in an attempt to prevent or inhibit external resorption. However, there have been no long‐term histological studies that have examined gutta‐percha versus calcium hydroxide treatment in avulsed teeth. The purpose of this study was to determine the long‐term therapeutic effect of calcium hydroxide therapy in avulsed teeth. Six adult macaca monkeys were anesthetized and all four maxillary incisors were extracted and bench‐dried for 25 min. The teeth were replanted and splinted with composite for approximately 2 weeks. Each animal served as its own control and the teeth were accessed, instrumented, and filled with either Ca(OH)2or gutta‐percha and AH26 cement. All access openings were filled with composite. The Ca(OH)2was replaced twice during the experimental period (approximately every 8 weeks). The animals were killed between 5 and 7.5 months postavulsion. The teeth were removed, sectioned, and examined histologically by two examiners. The results of the histological evaluation of external resorption indicated that there were no statistically significant differences in resorption indices between the teeth obturated with gutta percha or with calcium hydroxide (P>0.05). Replacement resorption was the primary cause of root destruction and only a few histological sections exhibited evidence of inflammatory r