Repair bond strength and nanoleakage of artificially aged CAD-CAM composite resin

Statement of problem

The polymerization of computer-aided design and computer-aided manufacturing (CAD-CAM) composite resins during their manufacture enhances their physical properties and biocompatibility but might compromise their reparability.

Purpose

The purpose of this in vitro study was to determine the microtensile bond strength and nanoleakage (NL) of aged LAVA Ultimate (LU) CAD-CAM composite resin after different repair protocols.

Material and methods

Fifty-eight LU miniblocks were prepared, thermocycled (10 000 cycles, 5°C to 55°C), and assigned to 10 surface pretreatment and bonding protocols: (1) tribochemical silica coating (CoJet, CoJet Sand; 3M ESPE)+Scotchbond Universal Adhesive (SBU; 3M ESPE); (2) CoJet+silane (SI, ESPE Sil; 3M ESPE)+Adper Scotchbond 1 XT Adhesive (XT; 3M ESPE); (3) CoJet+10-methacryloyloxydecyl dihydrogen phosphate–based silane (MO; Monobond Plus; Ivoclar Vivadent AG)+XT; (4) CoJet+XT; (5) 30-μm alumina airborne-particle abrasion (AL)+SBU; (6) AL+SI+XT; (7) AL+MO+XT; (8) AL+XT; (9) no pretreatment+SBU; and (10) no pretreatment+XT. All blocks were repaired using the Filtek Supreme XTE (3M ESPE) composite resin. Stick-shaped specimens (0.9×0.9 mm) were obtained and submitted to microtensile bond strength (μTBS) and %NL testing after 24 hours. μTBS data were analyzed with 1-way ANOVA, followed by the Tukey post hoc test, and NL data with nonparametric Kruskal-Wallis and Dunn tests (α=.05).

Results

For μTBS, CoJet, and AL pretreatments showed significantly higher mean μTBS, especially when used together with SBU. No pretreatment+XT yielded the lowest mean μTBS. For NL, marginal sealing improved significantly after the use of SBU regardless of the surface treatment. This improvement was only statistically different after tribochemical silica coating.

Conclusions

Airborne-particle abrasion with alumina particles, silica coated or not, together with the application of SBU resulted in the highest mean μTBS. The lowest %NL was recorded when aged LU blocks were repaired using SBU.