Influence of dentin conditioning and contamination on the marginal integrity of sandwich class II restorations

This study investigated the influence of dentin conditioning and contaminat ion on the marginal adaptation of Class II sandwich restorations. Large butt-joint MOD cavities with cervical mm below the CEJ were cut into 72 extracted were filled using Z100 or a sandwich technique with either Vit remer or F2000 in combination with Z100. For all three material combination s three different pretreatments were compared: total etch, selective etch a nd dentin contamination with saliva and blood prior to primer/adhesive appl ication. After water storage for 21 days and thermocycling (2000x, 5 - 55 d egrees C) replicas were produced for quantitative marginal analysis in the SEM. Teeth were immersed in 0.5% basic fuchsin for 24 hours and dried. Perc ent dye penetration over the total marginal length was analyzed in three la yers using a sequential grinding techique. Statistical analysis was perform ed using a two-way ANOVA. Post-hoc analyses were carried out with univariat e Mann-Whitney-U-tests adjusting for multiple comparisons by a sequentially rejective test procedure (Bonferroni-Holm) at p<0.05. Both F2000 and Vitremer sandwich restorations showed better marginal adapta tion than Z100 total-bond restorations with all pretreatments. Acid etching of the dentin significantly influenced the marginal adaptation of Z100 tot al-bond restorations and Vitremer sandwich restorations. All types of resto rations showed considerable microleakage. On contaminated dentin, sandwich restorations showed better marginal integrity than total-bond restorations. Marginal adaptation did not correspond with microleakage in all groups. In conclusion, F2000/Z100 and Vitremer/Z100 sandwich restorations show bett er marginal adaptation than Z100 total-bond restorations in large Class II cavities with cervical margins in dentin. Microleakage cannot predictably b e prevented with the sandwich technique, Sandwich restorations seem to be l ess sensitive to contamination with saliva and blood.