Pulpal responses to mineral trioxide aggregate with and without zinc oxide addition in mature canine teeth after full pulpotomy

The addition of zinc oxide (ZnO) to mineral trioxide aggregate (MTA) has been shown to prevent tooth discoloration; however, its biological effects remain unclear. This study aimed to evaluate the pulpal responses to MTA containing 5% ZnO in full pulpotomy of dogs' teeth. Forty caries-free premolars from mixed-breed dogs were subjected to full pulpotomy. 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, processed for histological evaluation, and stained with hematoxylin and eosin. Tissue response data were analyzed using the Mann-Whitney U test at a 95% significance level. The incidence, thickness, and continuity of hard-tissue bridge formation were significantly lower in the MTA + ZnO group (p = 0.007, p = 0.001, and p = 0.002, respectively). Most samples in both groups exhibited no inflammatory cells, and none showed signs of necrosis. Incorporating ZnO into Angelus MTA compromised the quantity and quality of hard-tissue bridge formation following full pulpotomy in dogs' premolars.