Smear layer deproteinizing improves bonding strength of self-etch adhesives: Study

The study is published in the Journal of Dentistry.

Citra Kusumasari and colleagues from the Department of Conservative Dentistry, Faculty of Dentistry, University of Indonesia, Jakarta, Indonesia conducted the present study with the sole objective to evaluate the micro-tensile bond strength (μTBS) of self-etch adhesives (SEA) to normal and caries-affected dentin after smear layer deproteinization with papain enzyme-based and NaOCl-based chemo-mechanical caries removal agents (CRAs) and to compare their efficacy to a 6 % NaOCl solution.

The authors included a total of forty extracted human molars with occlusal carious lesions. All teeth were randomly divided into four pretreatment groups: no treatment (control), Papacarie for 60 s, Carisolv for 60 s, and 6 % NaOCl for 15 s. After pretreatment, Universal Bond Quick ER (UBQ, one-step, 1-SEA) or Clearfil SE Bond 2 (CSE, two-step, 2-SEA) was applied to the pre-treated surface, and built-up with resin composite (Clearfil AP-X).

The μTBS test was performed after 24 h water storage of the specimens at 37 °C, and the modes of failure were determined under SEM. Deproteinizing effects of the tested agents on smear layer-covered dentin was quantified by changes in the amide:phosphate ratio using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) analysis.

The results showed that-

1. On caries-affected dentin the μTBS improved significantly after pretreatment with Papacarie, Carisolv, and 6 % NaOCl with both SEAs (p < 0.05).
2. Papacarie pretreatment significantly improved the μTBS of UBQ on normal dentin compared to NaOCl pretreatment (p < 0.05).
3. ATR-FTIR revealed that all agents significantly decreased the amide:phosphate ratio on the smear layer-covered normal and caries-affected dentin (p < 0.05).

Hence, the authors concluded that "smear layer deproteinization with Papacarie (a papain enzyme-based gel) or Carisolv (a NaOCl-based gel) can improve the μTBS to normal and caries-affected dentin bonded with 2-step self-etch adhesives."