Pulpal response to a newly developed MMA based resin cement for bonding tooth-colored indirect restorations

To evaluate the pulpal responses to a newly-developed MMA-based self-etch resin cement, when used as a luting agent for indirect resin composite restoration, and to compare the results with those obtained from a total-etch luting agent, glass-ionomer cement, and amalgam restoration.

120 cervical cavities were prepared in monkey teeth and divided into four equal groups according to the restorative materials used: (1) the cavities were restored with resin composite inlays using a self-etch resin cement as a luting agent (M-Bond); (2) the cavities were also restored with resin composite inlays but using a total-etch resin cement as a luting agent (Super-Bond C & B); (3) the cavities were directly restored with glass-ionomer cement (Fuji II); or (4) the cavities were directly restored with amalgam (Dispersalloy). The restored teeth were extracted at 3, 30, or 90 days after restoration, then fixed in 10% neutral buffered formalin. The specimens were prepared using routine histopathological procedures. Five microm-thick sections were stained with hematoxylin and eosin or Brown & Brenn gram stain for bacterial observations. Histological responses in the pulpal tissue and bacterial penetration were observed under a light microscope and evaluated using standard scores. The results were statistically analyzed using the Kruskal-Wallis test (P< 0.05).

At all time intervals, no significant differences of pulpal inflammatory responses between M-Bond and Super-Bond C&B were observed (P> 0.05). Both resin cements showed no serious pulpal responses, such as necrosis or abscess formation. In general, both MMA-based resin cements showed similar pulpal responses to those of glass-ionomer cement except for congestion of pulpal blood vessels at 3 days after restoration in which glass-ionomer cement exhibited a lower level than that of the MMA-based resin cements. For the group restored with amalgam, at 3 days after restoration, severe odontoblastic disorders and blood vessel congestions with a large infiltration of inflammatory cells were detected. At 30 and 90 days after restoration, slightly inflammatory irritations were observed irrespective of the materials used. Reparative dentin formation and bacterial penetration were found mostly in the group restored with amalgam.