Research on Micro-Shear Bond Strength

According to recent research, it has been observed that only hydrophobic bonding resin (HBR) can obtain good micro-shear bond strength (MSBS) results, while atmospheric pressure plasma (PLA) alone was not beneficial, as published in the Journal of Esthetic and Restorative Dentistry.

Literature suggests very few studies where the effect of argon plasma on repair bond strength using nanofilled and microhybrid composites is evaluated.

Hence, William Matthew Negreiros and colleagues from the Dental Materials Division, Department of Restorative Dentistry, Piracicaba Dental School, University of Campinas, Piracicaba, São Paulo, Brazil conducted this present study with the sole aim to evaluate the effect of atmospheric pressure plasma (PLA), sandblasting (SAN), silanization (SIL), and hydrophobic bonding resin (HBR) on the micro-shear bond strength (MSBS) of fresh nanofilled (NF) or microhybrid (MH) composites to water-aged nanofilled composite.

The authors fabricated NF plates and stored them in distilled water for 4 months. The aged plates were assigned to the different groups (n = 6):

• 1- untreated
• 2- SAN + SIL + HBR
• 3- HBR
• 4- PLA + HBR
• 5- SAN + HBR
• 6- SAN + PLA + HBR
• 7- PLA

Two fresh composite cylinders were constructed on each plate with NF or MH composites and tested after 24 h or 1 year of water-storage, using the MSBS testing. Data were analyzed by three-way ANOVA and Tukey test (α = 0.05).

Key Findings

• NF yielded better outcomes than MH at 24 h, which was not observed at 1 year.
• HBR showed the highest MSBS results, while untreated and PLA groups yielded the lowest one.
• MSBS reduced for all groups after 1 year.

Therefore, it was concluded that "Only HBR can obtain good MSBS results, while PLA alone was not beneficial. After 1 year, a reduction in repair MSBS was observed and the type of composite did not influence the results."

Furthermore, the repair technique can be simplified with the use of only an adhesive and macromechanical retentions in the old composite, regardless of the type of fresh composite, the authors inferred.