Abstract
Thio-urethane oligomers improve conversion and mechanical properties of resin cements. The objective of this study was to evaluate the effect of resin cements formulated with thio-urethane (TU) oligomers on microtensile bond strength (µTBS) of ceramics to composites subjected to thermal/mechanical cycling.Methods: BisGMA/UDMA/TEGDMA (50/30/20 wt%) containg 0 (control, EC) or 20 wt% aliphatic or aromatic thiourethane (HDDI and BDI, respectively) were mixed with CQ/amine (0.2/0.8 wt%) and 25 wt% 0.7um Ba glass. Rely X Ultimate (RU-3M ESPE) was used as the commercial control. The cements were sandwiched between ceramic (IPS e.max Press) and resin composite blocks (Filtek Supreme, 3 M-ESPE). Eight bonded blocks were produced per experimental group. Prior to bonding, ceramic surfaces were etched (20 s – 10% HF) and silanized. Composite surfaces were treated with Single Bond Universal (3 M ESPE). Specimens were stored for 24 h in distilled water at 37 °C, and then either tested immediately, or subjected to thermal (10,000, 5 °C and 55 °C) or mechanical cycling (300,000 cycles). Sticks (1 mm2, average of 25 sticks per block) were cut and tested for µTBS (1.0 mm/min). Data were analyzed with two-way ANOVA/Tukey’s test (α = 5%). Fracture surfaces were analyzed to determine failure modes.Results: The µTBS for HDDI and RU was significantly higher than BDI and EC cements. BDI led to significantly higher µTBS than EC after 24 h, Tc and Mf. µTBS decreased significantly after thermal/mechanical cycling for all groups. Failure modes were predominantly adhesive or mixed.Significance: The use of selected thio-urethane oligomers was able to increase the µTBS of composite-cement-ceramic specimens. Tc and Mf reduced µTBS for all resins cements.
Highlights
All-ceramic systems have been widely used in dentistry to indirectly restore fractured/lost/decayed teeth, mainly due the growing demand for highly esthetic treatments
Conventional resin cements are extensively used in restorative dentistry because of their ability to chemically bond to the ceramic material and mechanically interlock the tooth substrate via hybrid layer formation
For the results obtained after 24 h storage in distilled water, the mean values of microtensile bond strength (mTBS) of RelyX Ultimate, the experimental resin cement modified by HDDI and experimental resin cement modified with BDI were significantly higher than the experimental resin
Summary
All-ceramic systems have been widely used in dentistry to indirectly restore fractured/lost/decayed teeth, mainly due the growing demand for highly esthetic treatments. The long-term clinical success of the bond between dental ceramics and resin cements primarily depends on the composition of the ceramic material and the cementation procedure [1,2]. The luting procedure between the ceramic and the tooth is based on clinical adhesive strategies usually employing a resin cement [3,4]. The current gold standard for cementation of ceramics is the pretreatment of the ceramic with hydrofluoric acid (HF) etching, followed by application of a silane coupling agent and subsequently a resin cement [1,5,6,7]. Conventional resin cements are extensively used in restorative dentistry because of their ability to chemically bond to the ceramic material and mechanically interlock the tooth substrate via hybrid layer formation. Due to the tapered nature of crown preparations for ceramic restorations and the constant physical and mechanical challenges to which these restorations are subjected, resin cements need strong adhesion to the tooth and the ceramic, adequate mechanical properties, solubility resistance to avoid cement degradation,
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