Reparative dentin is produced in reaction to various stimuli such as attrition, caries or a restorative dental procedure. Its composition is still not well defined. Reactive dentin at the occlusal portion of the rat incisor is enriched in noncollagenous matrix proteins (NCPs). Recently, it has been reported that amelin is expressed in traumatized odontoblasts and that enamel proteins (EPs) promote dentin repair. Objectives: The aim of the present study was to examine the presence and distribution of NCPs and EPs in reparative dentin produced following pulp exposure. Methods: The pulp chambers of first and second maxillary molars of male Wistar rats weighing between 130-160 g were perforated and left open. At 11 days following exposure, the maxillae were dissected out and fixed by microwave irradiation to improve antigen retention. They were then embedded in LR White resin and processed for immunogold labeling with antibodies to amelin/ameloblastin (AMBN), amelogenin (AMEL), bone sialoprotein (BSP) and osteopontin (OPN). Results: Reparative dentin was deposited along the wall of the radicular dentin, more abundantly towards the apical portion of the root. It formed a continuous layer or distinct globular masses, sometimes with embedded cells. The matrix contained few collagen fibers and much afibrillar material intensely stained for OPN and moderately for BSP. Reactivity for these two proteins was weak and diffuse over the dentin matrix proper and strong over cementum. No significant accumulation of labeling for AMBN or AMEL was observed over reparative dentin while matrix surrounding epithelial cells trapped at the junction between dentin and cementum was intensely reactive. Conclusion: The data indicate that reparative dentin has a distinct composition and is enriched in NCPs found in relative abundance in bone and cementum. Supported by the Canadian Institutes of Health Research and Le Fonds Paul Geoffrion.

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