The effect of pulp capping and pulpotomy on hard tissue bridges of contaminated pulps

The pulp and dentine of permanent incisors in 13 young monkeys were exposed by grinding. The pulpal perforations were treated by partial pulpotomy with a tungsten carbide fissure bur after exposure for 4, 48, or 168 hours in nine animals, and by direct pulp capping after exposure for 4 or 48 hours in the remaining four animals. After haemostasis, the pulpal wounds were covered with calcium hydroxide (Dycal), followed by conventional amalgam (Revalloy). Initial and subsequent formation of hard tissue bridges over the wounds was studied by conventional histology after 1-6 months. Screening showed three categories of initial bridging development, differing in nature and rate of formation. A significant difference in the distribution of the two main categories was found between the two methods of treatment (P less than 0.02). A similar difference was observed when partial pulpotomy was performed after 168 hours compared with that performed after 4 hours (P = 0.055). No relationship was found between the initial bridging category and the eventual development of complete dentine bridges.