Comparative study of the bond strength of composite resins in the cementation of indirect restorations

Abstract

Introduction: Nowadays there is an increasing development of materials capable of reducing the time of appointment, as is the case of multi-mode adhesive systems. The same occurs with composite resins as the creation of bulk-fill resins. This new type of resin can be classified, for its properties, between the fluid resins and the nanohybrid and microhybrid resins [1]. As for their mechanical properties, these materials have been shown to be stiffer (higher modulus of elasticity) and more plastic (greater plastic deformation) than conventional fluid resins. However, they have lower mechanical properties when compared with conventional nano-hybrid and microhybrid resins [1]. The new generation of bulk-fill resins has a low polymerization contraction value when compared to both nanohybrid and microhybrid fluid and non-flowing resins [2–4], so the aim of this study is to evaluate if it is possible to cement indirect restorations with Filtek™ Bulk Fill. Materials and methods: This work was approved by the IUEM Ethics Committee (nº572). Eighteen healthy molars were submitted to immediate dentin sealing (IDS) after exposure of the middle dentin. After 24 hours, they were randomly divided into two groups according to the type of restorative material, composite resin (Filtek™ Z100 3M ESPE) or lithium dissilicate (IPS e.max CAD - Ivoclar Vivadent). Each group was subdivided into three subgroups according to the adhesion material. 9 disks were obtained through a calibrated cylinder in 4x4 mm composite resin (Filtek™ Z100 3M ESPE) and adhered to the crowns with Filtek™ Z100 (3M ESPE), Filtek™ Bulk Fill (3M ESPE) and RelyX™ Veneer (3M ESPE). 9 ceramic blocks (IPS e.max CAD - Ivoclar Vivadent) with similar dimensions were produced and adhered with the same materials. The samples were stored for 24 hours at 37 °C and sectioned in beams. The specimens were pulled in a universal testing machine at 1 mm/min speed. The resulting fractures were classified stereoscopically. The adhesive interfaces were morphologically evaluated with SEM. Statistical analysis was performed using Student’s t tests, Anova One-Way (p ≤ 0.05). Results: The differences between the materials used in the adhesion of indirect restorations are not statistically significant, so Filtek ™ Bulk Fill can be used as cementing material. The highest adhesion values were obtained by the RelyX™ Veneer resin cement (Table 1, p = .385; Table 2, p = .158). Discussion and conclusions: This investigation tested the adhesive strength of three composite resins when cemented to two different types of indirect restorations. No statistically significant differences were obtained between the different adhesion materials, regardless of restorative material, so any of the materials can be used in adhesion of indirect restorations to composite resin or ceramic. Indirect restorations in both composite resin and lithium disilicate can be adhered with either Filtek ™ Z100, Filtek ™ Bulk Fill or RelyX ™ Veneer, as no statistically significant differences were obtained when indirect restorations are adhered with these materials. RelyX ™ Veneer resin cement was the adhesion material that achieved best adhesive strength results and the highest adhesive strength results were obtained in the indirect composite resin restoration.