In vitro marginal leakage of Class II composite resin restorations by thermal cycling.

In vitro marginal leakage on class II composite resin restorations by thermal stress was investigated at the cervical, proximal, bucco-lingual, and mesio-distal margins of extracted human premolars. The composite materials used in this study were: (1) Occlusin with Bonding Agent(a), (2) Palfique Light-S with Light Bondb, (3) P-50 with Dentin Primer & Scotchbond 2c, and (4) P-50 with Vitrabond and Scotchbond 2c. Those four groups were representatives of a (l) conventional bonding agent, (2) hydrophilic bonding agent, (3) dentin priming or conditioning agent with a hydrophilic bonding agent, and (4) glass ionomer cement used for a sandwich technique. The number of experimental teeth investigated in each group was ten. The marginal seal among the margins and composite materials was investigated by a dye penetration test using a basic fuchsin solution. The results showed that marginal seals at the cervical margins were found to be improved significantly by the use of dentin bonding materials and methods when compared with a conventional (enamel) bonding agent. However, the proximal margins generally had a less effective marginal seal than the occlusal (bucco-lingual and mesio-distal) margins. In addition, the mesio-distal margins showed a less favorable result than did bucco-lingual ones. These differences among margins might be from the efficacy of a round bevel along the occlusal cavo-surface margin, the different thicknesses of cavity enamel, and the order of light exposure.(ABSTRACT TRUNCATED AT 250 WORDS)