Factors affecting marginal integrity of class II bulk-fill composite resin restorations

Abstract

Background. Bulk-fill composite resins are a new type of resin-based composite resins, claimed to have the capacity to be placed in thick layers, up to 4 mm. This study was carried out to evaluate factors affecting gap formation in Cl II cavities restored using the bulk-fill technique. Methods. A total of 60 third molars were used in this study. Two Cl II cavities were prepared in each tooth, one on the mesial aspect 1 mm coronal to the CEJ and one on the distal aspect 1 mm apical to the CEJ. The teeth were divided into 4 groups: A: The cavities were restored using the bulk-fill technique with Filtek P90 composite resin and its adhesive system and light-cured with quartz tungsten halogen (QTH) light-curing unit. B: The cavities were restored similar to that in group A but light-cured with an LED light-curing unit. C: The cavities were restored using the bulk-fill technique with X-tra Fil composite resin and Clearfil SE Bond adhesive system and light-cured with a QTH curing unit. D: The cavities were restored similar to that in group C but light-cured with an LED light-curing unit. The gaps were examined under a stereomicroscope at ×60. Data were analyzed with General Linear Model test. In cases of statistical significance (P<0.05), post hoc Bonferroni test was used for further analyses. Results. The light-curing unit type had no effect on gap formation. However, the results were significant in relation to the composite resin type and margin location (P<0.001). The cumulative effects of light-curing unit*gingival margin and light-curing unit*composite resin type were not significant; however, the cumulative effect of composite rein type*gingival margin was significant (P=0.04) Conclusion. X-tra Fil composite exhibited smaller gaps compared with Filtek P90 composite with both light-curing units. Both composite resins exhibited smaller gaps at enamel margins.

Influence of adhesive-composite application modalities on their bonding to tooth structure and resistance of the performed restorations to failure

“…On the other hand; the concept of bulk filling the prepared tooth cavities was simultaneously existed with the availability of a new category of bulk-fill resin composite restoratives 13 , 14 . Both bulk-fill and preheated resin composites were reported to allow the curing light to go more deep through, however most of the manufacturers' recommendations insisted that the successful bulk-fill restorations should not exceed 4 mm in depth 16 , 20 , 21 . This feature accordingly suggested a possible success of adhesive's co-curing approach in bonding the bulky-inserted resin composites to tooth structure.…”

“…Some investigators 18 , 19 referred this weakness to the possible insufficient curing of the adhesive together with the subsequent contraction stresses of the curing overlaying resin composite. In response, the current study estimated a considerable success of the adhesive co-curing technique in presence of bulk-fill resin composite based on the documented lower contraction stresses and the ability of bulk-fill composite materials to transmit the curing light much deeper 16 , 20 , 21…”

In-Vitro Evaluation of Microleakage of Class II Cavities Restored with Bulk-Fill Flowable Composite

“…None of the two materials used in the current study could completely prevent microleakage in the dentinal margins of the gingival wall. However, no significant differences in the microleakage of the gingival wall margins of bulk-fill flowable composites and high frequency of microleakage score zero in these groups justify their safe use [16]. Low polymerization shrinkage of bulk-fill flowable composites is partly due to their different resin content.…”

“…The time at which the substance cannot compensate the polymerization shrinkage determines the final tensions in the material [18]. Therefore, this type of composite resins behaves differently compared to conventional methacrylate-based materials [16]. It should be noted that no dye penetration occurred between the two layers of bulk-fill and microhybrid composites, which was expected since they were both manufactured by the same company.…”

Light-Curing Units, Photoinitiators System, and Monomers on Physico-Mechanical Properties of Experimental Composite Resins

“…Thus, QTH LCU require filters to limit the wavelength range. Thus, only the blue spectral region is selected for composite resin light-curing, since it is the camphorquinone (CQ) absorption peak [4,6].…”