Composite repair: On the fatigue strength of universal adhesives

Objectives: To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.Methods: Composite samples were aged in water at 37 degrees C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 x 2 x 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (alpha = 0.05).Results: Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p Significance: Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.(c) 2021 The Author(s). Published by Elsevier Inc. on behalf of The Academy of Dental Materials. CC_BY_NC_ND_4.0</p

COMPOSITE REPAIR : ON THE FATIGUE STRENGTH OF UNIVERSAL ADHESIVES

Objectives: The repair of defective restorations has been a well-accepted treatment modality. Recently, universal, one-bottle adhesives were introduced, to ensure a fast and reliable bonding procedure. This study evaluated the strength and fatigue resistance of the bonded interfaces between aged and new composite as a function of adhesive resin treatment. Methods: Composite specimens (2x2x12mm) were prepared (Filtek Supreme XTE, 3M, ESPE) for four point-bending and aged in water (37 °C/ 180 days). The twin bonded interface (TBI) specimens between the aged and new composite resin ((Filtek Supreme XTE) were prepared using different adhesives: 1) iBond Universal (IB), Heraus Kulzer, (2)Futurabond U (FBM+), Voco, (3)Scothbond Universal (SU), 4) Scotchbond Universal Plus (SU+) 3M-ESPE 4) Clearfil Universal Bond Quick (CFU), Kuraray.5)Clearfil repair (CFR), Kuraray. Unrepaired aged samples (AC) as well as fresh samples (FC) served as controls. The specimens were subjected to either quasi-static (n=12) or cyclic (n=25/group) four-point flexure testing using a stress ratio of 0.1 and frequency of 4Hz to failure in hydrated conditions (1.2 million cycles). Data were analyzed using one-way ANOVA for quasi-static and Wilcoxon Rank Sum test for fatigue data (α=0.05). Results: Under quasi-static loading, flexural strength of the fresh (120 ±10MPa) and aged (114±16MPa) controls were significantly higher than other groups (p<0.05). The fatigue resistance of the fresh or unrepaired specimens were significantly higher than repaired ones. No significant differences occurred between bonding protocols with the exception of CFU, which produced significantly lower values. Conclusions: The fatigue resistance of the repaired interfaces were adhesive protocol dependent and showed lower fatigue resistance than the controls