Abstract
This study aimed at evaluating the marginal and internal adaptation of low-viscosity bulk-fill composites to enamel and dentin using a self-etch or an etch-and-rinse adhesive without and with artificial ageing. Hundred and twenty-eight MOD cavities in extracted molars were assigned to eight groups (n = 16), restored with the adhesives OptiBond FL (OFL) or Xeno V+ (X) and two low-viscosity bulk-fill composites SDR or x-tra base, covered with Premise. Tetric EvoCeram Bulk Fill and Premise served as a control. n = 8 per group were subjected to prolonged water storage (180 days) and thermocycling (2500×). Scanning electron microscopy was used to determine marginal gaps (MG) and interfacial adhesive defects (IAD). There were no significant differences between composite types in 44 out of 48 (MG) or 43/48 (IAD) comparisons. More MG were observed with X than with OFL (14 out of 16 comparisons, two significant), while in 16 of 16 comparisons with X more IAD were observed (14 significant). After artificial ageing, MG generally increased (9/16 significant), compared to IAD (one significant). The performance of the investigated composite types concerning the integrity of the tooth-composites interface was comparable. Compared to the 1-step self-etch system, the bond with the 3-step etch-and-rinse adhesive was raised.
Highlights
Since the end of the 1990s, due to improved durability and stability, the number of clinical indications for composite materials has grown and usage has continuously increased [1]
Since the year 2000 developments in resin composites are more focused on systems with reduced polymerization shrinkage and shrinkage stress to prevent consequential failures such as adhesive defects, postoperative sensitivity and restoration fracture, which can in turn
Regardless of adhesive system and artificial ageing, there were no significant differences between composite types in 44 out of 48 comparisons for marginal gaps (MG) (92%, p ≥ 0.077) or 43 out of 48 comparisons for interfacial adhesive defects (IAD) (90%, p > 0.05)
Summary
Since the end of the 1990s, due to improved durability and stability, the number of clinical indications for composite materials has grown and usage has continuously increased [1]. Today composite materials are the primary choice for direct restorations in the dental practice and clinical studies report positive outcomes of resin composites with increased longevity [2,3,4,5]. Despite similar chemical composition as conventional flowable composites, it can be applied in bulks of 4–6 mm depending on the individual product due to enhanced polymerization depth. The simplified procedures make the bulk filling technique popular with clinicians and several advantageous outcomes were noted such as lower polymerization shrinkage and stress, reduced cusp deflection, and improved self-levelling ability compared to conventional
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