Rolf Müllejans | PubMed Health

PubMedDate not supplied

An in vitro comparison of metal and transparent matrices used for bonded class II resin composite restorations.

This study compared excess formation of direct bonded Class II restorations using different matrix systems-metal or transparent. Sixty freshly extracted, non-carious, posterior human teeth were used. In all of the teeth, standardized MOD-cavities were prepared with the gingivoproximal margins located 1.0-1.5 mm cervical to the cemento-enamel junction. The prepared teeth were randomly assigned to six groups. Half were restored using metal matrices and wooden wedges; the other half were restored using transparent matrices and reflective wedges. Three different material systems were used to fill the cavities: 1) a hybrid composite (Tetric) plus an adhesive bonding agent (Syntac Classic), 2) a flowable composite (Tetric Flow) plus Syntac Classic and 3) a compomer (Dyract AP) together with an adhesive bonding agent designed for compomers (Prime & Bond NT). After the specimens were preserved in saline solution, scanning electron microscopy (SEM) assessed the amount of overhang formation at the restoration margins. The data collected indicated the use of transparent matrices resulted in significantly higher amounts of excess material at the restoration margins compared with metal matrices. Moreover, there was no significant difference between the materials when the same matrix was used. All of the dental restorations examined displayed material overhang. Based on these findings, the authors concluded that the type of matrix exerts a major impact on overhang formation, with metal matrices resulting in significantly less excess material buildup.

Compomers↗

PubMedDate not supplied

Increment technique for extended Class V restorations: an experimental study.

The application and polymerization of composite or polyacid-modified resin composites in thin layers (increment technique) for filling cavities might partially compensate for the stress associated with polymerization shrinkage. In this study, the effect of this technique on the marginal integrity of Class V polyacid-modified composite restorations was investigated. In 30 extracted premolars, extended Class V cavities were prepared with the apical margin in root dentin and the coronal margin in enamel. They were then subjected to different treatments (10 teeth in each case): a) placement and polymerization of a thin resin composite layer (Dyract-Dyract PSA) in the coronal part of the cavity (plus one increment for the residual part) (Group 1), b) a thin layer at the apical part of the cavity (plus one increment for the residual part) (Group 2) and c) restoration of the entire cavity with one increment (bulk technique) (Group 3). Following three days' storage in water, the teeth were subjected to cyclic thermal loading (4 degrees C <-> 55 degrees C, 2,000 cycles). The percentages of defective bonding detected along the total length of the restoration margin were assessed before and after thermocycling by scanning electron microscopy. Following loading and thermocycling, no significant differences were found at the restoration-enamel interface. Fewer gaps were found at the restoration-dentin interface in Group 1 (18.7 +/- 25.7%) and Group 2 (20.5 +/- 22.8%) compared to the reference Group 3 (42.2 +/- 30.6%) (Mann-Whitney U test: p<0.05). Moreover, there were no significant differences between the two increment groups (1 and 2). In a significantly larger number of cases, a completely intact dentin restoration margin was detected when a coronal increment (Group 1) (44.4%) was used instead of the bulk technique (Group 3) (13.6%) (Chi square test: p<0.05). These results indicate that gap formation can be significantly minimized by using an increment technique to restore extended Class V cavities with polyacid-modified composite materials.

Chi-Square Distribution↗