Synthesis and characterization of a new methacrylate monomer derived from the cashew nut shell liquid (CNSL) and its effect on dentinal tubular occlusion.

Objective: The aim of this study was to synthesize, to characterize and to evaluate the effects on tubular occlusion of new monomer derived from cashew nut shell liquid (CNSL), also studying the effects of acid challenge (AC) on dentin surfaces treated with desensitizers.

Methods: The intermediary cardanol-epoxy (CNE) was synthesized through epoxidation of CNSL, followed by synthesis of cardanol-methacrylate-epoxy (CNME) through methacryloyl chloride esterification. Products were purified through chromatography column and characterized by Fourier transform infrared spectrometry and nuclear magnetic resonance. Resinous dentin desensitizers were formulated containing either unsaturated cardanol (CNU), CNE or CNME. Dentin disks were divided into seven groups: SL - Smear-layer, EDTA - EDTA-treated only, GLUMA - Gluma Desensitizer, OCB - One Coat Bond, CNU - CNU desensitizer, CNE - CNE desensitizer and CNME - CNME desensitizer. Dentinal fluid rate (DFF) was obtained using a Flodec equipment and tubular occlusion employing a scanning electron microscope (SEM), before and after AC. Data of DFF were submitted to two-way ANOVA and Tukey's test (p<0.05).

Results: GLUMA showed the lower reduction in DFF when compared to the other products, which were statistically similar. Even after AC, CNME presented the most homogenous and occluded surface, while CNE and CNU were partially removed, GLUMA was completely removed and OCB keep an occluded, but irregular surface.

Significance: CNME showed a great reduction of DFF and a homogenous occluded surface, suggesting that it may be a suitable and acid-resistant treatment option for dentine hypersensitivity.