Short-term dentin bridging of mechanically-exposed pulps capped with adhesive resin systems

Dentin bridging of 150 mechanically exposed monkey pulps to two adhesive resins [BondWell LC (BW); Clearfil Liner Bond II (LB)] and a calcium hydroxide cement [Dycal (DY)] were histopathologically evaluated at 3, 7, 14, 30, and 60 days after operation (n = 10). The dentin bridge structure was three-dimensionally reconstructed from serial sections using a computer-aided reconstruction system. At three and seven days, in all pulps, no necrotic tissue and slight inflammatory cell infiltration was observed just below the exposure site. At 14 days, spindle-shaped fibroblast cells could be detected at the wound surface. All dentin chips showed reparative dentin deposition along the periphery of the wound surface. From this stage, the formation of secondary dentin from the pulpal wall at the periphery of the exposed area was recognized in all pulps. At 30 days, initial signs of dentin bridging were observed at the wound surface with a well-organized layer of odontoblastoid cells. The exposed area became occluded with a dentin bridge as the observation period increased. Group DY showed significantly higher incidence of dentin bridging than other groups at 30 days (p < 0.05). However, no significant difference of dentin bridge formation was found between Group DY and Groups BW and LB at 60 days. Bacterial penetration along the cavity walls and pulp tissue could not be detected in all groups. Histopathological observations and three-dimensional image analysis suggested that dentin bridge formation may occur following three patterns: (1) formed from the periphery of the residual dentin chip at the wound surface within 14 days, (2) formed within 14 days from the periphery of the cavity floor and with formation of reparative dentin by stimulation during the cavity preparation, and (3) formed from the wound surface within 30 days after exposure.