2015 Volume 58 Issue 1 Pages 53-59
Purpose: Direct Crowns made of a composite resin material have recently been developed by 3M ESPE. These crowns maintain the coronal morphology even in an uncured state. The advantage of Direct Crowns is that the entire process of crown fabrication until cementing and delivery can be completed chairside on the same day. However, there is little information available regarding the immediate bonding property of resin cement to light-cured composite resin crowns. Thus, this study examined the effects of time after crown fabrication on the bonding property.
Methods: This study used a combination of composite resin and resin cement from the same manufacturer. The materials used were: Direct Crowns with RelyX Unicem 2 Automix (3M ESPE, USA) and Estenia C & B with Panavia F 2.0 (Kuraray Noritake Dental). Discs of Estenia C & B and Direct Crowns were fabricated and divided into the following four groups: bonding performed immediately after fabrication of discs ( (1) 0h-Direct Crown group and (2) 0h-Estenia C & B group) and bonding performed after 48 hours ( (3) 48h-Direct Crown group and (4) 48h-Estenia C & B group). A microtensile bond strength test was performed and the fracture surface was examined by scanning electron microscopy. ATR-FTIR (attenuated total reflection-fourier transform infrared spectroscopy) analysis was performed on the Direct Crowns.
Results: The adhesive strength was significantly higher in the 0h-Direct Crown group (76.6±13.4 MPa) compared with the 0h-Estenia C & B group (60.9±14.8 MPa), the 48h-Direct Crown group (45.8±9.7 MPa), and the 48h-Estenia C & B group (53.7±12.5 MPa). When fracture surfaces were examined after the microtensile bond strength test, the 0h-Direct Crown group had many mixed fractures but no fracture at the interface between composite resin and resin cement. The other three groups had mainly mixed fractures and fractures at the interface between composite resin and resin cement. The results of ATR-FTIR analysis suggest that the degree of surface polymerization was low for Direct Crowns immediately after fabrication compared with Direct Crowns 24 hours later.
Conclusion: The results of this study suggest that Direct Crowns are effective in clinical use with their high adhesion due to bonding immediately after fabrication.
