Effect of Tribochemical Coating on Composite Repair Strength

This study evaluated the effect of tribochemical coating on composite-to-composite repair interfacial fracture toughness (iFT). Sixty beam-shaped specimens (21x4x3 +/- 0.2 mm) were prepared with a nanofill composite (Filtek Supreme Ultra [FSU]) and a nanohybrid composite (Clearfil Majesty ES-2 [CME]) and aged for 50,000 thermocycles (5 degrees C-55 degrees C, 20-second dwell time) and then sectioned in half. The resulting 120 hemispecimens (60 for each composite) were randomly assigned to different repair methods (n=10): universal adhesive (Clearfil Universal Bond Quick [CUB]), sandblasting followed by CUB, or tribochemical coating (CoJet, CoJet sand, Espe-Sil, and VisioBond). The repair surface was prepared with a diamond bur (Midwest #471271), rinsed, and dried. Each aged composite brand (FSU, CME) was repaired with either the same composite or the opposite composite. All adhesives and composites were light cured with a high-irradiance LED curing light (Elipar DeepCure-S). After postrepair storage in 100% humidity and at 37 degrees C for 24 hours, iFT was measured as K-Ic (MPa.m(1/2)). Data were analyzed for statistical significance using two-way analysis of variance (ANOVA) and the Tukey honest significant difference post hoc test (alpha=0.05). Regardless of the substrate composite, ANOVA showed significant differences for surface treatment (p < 0.0001) and repair composite (p < 0.0001). Mean iFT values (SD) ranged from 0.91 (0.10) MPa.m(1/2) to 2.68 (0.12) MPa.m(1/2). Repairs made with FSU after CoJet resulted in significantly higher iFT (FSU: 2.68 MPa.m(1/2); CME: 2.21 MPa.m(1/2)) when compared to the other experimental groups. The repair iFT was higher with CoJet treatment and when the nanofill composite FSU was used as the repair composite.