Histological evaluation of pulpal responses after full pulpotomy in mature dogs' teeth using mineral trioxide aggregate with and without the addition of zinc oxide

Abstract Background: Addition of zinc oxide (ZnO) to mineral trioxide aggregate (MTA) has been shown to overcome the problem of tooth discoloration; however, the biological effects of ZnO addition have not been elucidated. The aim of this study was to evaluate the pulpal responses to MTA containing 5% ZnO when used in full pulpotomy in dogs’ teeth. Methods: Forty caries-free premolars were selected from mixed-breed dogs and were subjected to full pulpotomy. The exposed pulpal tissues were randomly capped with either Angelus MTA (MTA) or Angelus MTA mixed with 5% ZnO (MTA+ZnO) (n = 20 each). After 4 weeks, the teeth were extracted and processed for histological evaluation and stained with hematoxylin and eosin. Data related to tissue response were analyzed by the Mann-Whitney U test with a significance level of 95%. Results: The incidence, thickness and continuity of hard-tissue bridge formation was significantly lower for the MTA+ZnO (p = 0.007, p =0 .001 and p=0.002, respectively). In both experimental groups, most samples exhibited no inflammatory cells. None of the samples in either group demonstrated necrosis. Conclusions:Incorporation of ZnO into Angelus MTA compromised the quantity and quality of hard-tissue bridge formation observed subsequent to full pulpotomy in dogs’ premolars.