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Objective: The objective of this study was to evaluate the histological response of rat molars to four materials placed on the dental pulp.
Methods: We used 24 female Wistar rats (6 per group). The pulp chamber roof of the first and second upper molars was perforated. After control of bleeding (<5 minutes), a pulp coating material (ProRoot®MTA, Ifabond™, Calcipast+I or Biodentine™) was placed. After 30 days of treatment, the molars were observed under an optical microscope.
Results: ProRoot®MTA produced no inflammation of any pulp (p<0.0005). With Calcipast+I, inflammation was absent only in 18.7% of the pulps. All samples in all groups presented pulpal vitality. The ProRoot®MTA, Ifabond™ and Biodentine™ groups showed a dentin bridge and reparative dentin in all pulps. Only ProRoot®MTA showed a completely regular odontoblastic layer (p<0.0005). Ifabond™ and Biodentine™ generated an irregular odontoblastic layer in all pulps (p<0.00l) and Calcipast+I showed 50% regular and 50% irregular layers. All samples treated with ProRoot®MTA (p<0.0005), 81.25% with Calcipast+I and only 37.5% of those treated with Ifabond™ and Biodentine™ (p<0.0005) showed fibrosis. In all groups, calcifications appeared in areas outside the dentin bridge (p=0.027).
Conclusion: Although ProRoot®MTA had the best performance, the response of the pulp of rat molars to the materials used was similar according to the histological criteria of degree of inflammation and pulpal vitality. The regularity or irregularity of the odontoblastic layer did not influence the presence of a dentin bridge.