Evaluation of interface between tooth and dental composite resin with monocalcium phosphate MCP

Abstract

Sealing ability of dental material could determine long-term clinical outcomes of restoration. Monocalcium phosphate (MCP) added in dental composites promotes swelling and precipitation of apatite at the tooth restoration interface.  The aim of this study was to assess whether these features can improve sealing capability at the tooth-material interface when no bonding agent was employed.  A bonded composite was used as control. Cavities; 3 mm in diameter and 2 mm in depth, were prepared in the middle of buccal surfaces of sound premolars.  Fifteen samples (N=5/group) were randomly assigned for restoration either in Group I- conventional composite (Filtek Z350XT;Adper Single Bond 2), Group II- composite with MCP (Renewal MI), and Group III- composite-MCP aged in artificial saliva for 28 days (aged Renewal MI).  After restoration and thermocycling 5,000 times between 5 and 55 °C, teeth were sectioned and gap formation at the tooth-restoration interface were assessed using scanning electron microscopy (SEM). Whereas all samples restored with Filtek Z350 XT with adhesive system; Adper Single Bond 2, had no gap at the material / enamel interface, both aged and unaged Renewal MI formed gaps.  Aged Renewal MI, however, showed smaller gaps.  Furthermore, in this group layer of element was observed intermittently at the interface. The results that aged Renewal MI formed narrower interfacial gap suggest that MCP added in dental composite, when contact with artificial saliva, might improve sealing of restoration by material expansion and precipitation.