The aim of this in vivo study was to evaluate the effects of direct pulp capping techniques on the short-term response of mechanically exposed pulps using three commercially available adhesive resin systems. Class V cavities were prepared on the facial surface of 200 intact monkey teeth. Pulps were exposed with a carbide bur on the cavity floor. Each exposed pulp was capped with one of three commercially available adhesive resins or a hard-setting calcium hydroxide liner. All cavities were sealed with an adhesive resin, and were restored with hybrid resin composites. Inflammatory cell infiltration and dentine bridging of the exposed pulp and protrusion of the exposed pulp tissue into the cavities were evaluated histologically at 3, 7, 14, 30 and 60 days. A slight inflammatory cell infiltration was the principal reaction of the exposed pulp. The exposed area was occluded over time with dentine bridging in all groups. However, a protrusion of pulp tissue into the prepared cavity was observed at the periphery of the exposed area in all groups. These tissues communicated with the underlying pulp. The incidence of pulp tissue protrusion was ranked in order of increasing severity: Liner Bond II < Dycal < Bondwell LC = Super Bond C&B. Following pulp capping of the mechanical exposures, slight inflammation was the main reaction. Exposures became occluded with a dentine bridge over time. However, the protrusion of pulp tissue into cavities varied, depending on the materials used.