Effect of adhesive materials on tensile-bond strength and microscopic bonding gaps of sisal nanofiber and nanofiller composite to tooth structure

Inorganic filler is used in dental composite, which does not chemically adhere to organic materials. There are numerous organic compounds in the tooth structure and adhesive materials. Organic material may be used in place of inorganic fillers, such as sisal fiber. Adhesive materials consisted of total-etch and self-etch. In this study, sisal nanofiber was used as filler for a dental composite. The purpose of this study was to analyze the tensile strength and microscopic bonding gaps of sisal nanofiber, sisal nanofiber with coupling agent and nanofiller composite to tooth structure with different adhesive materials. The sisal fibers were reduced to nano size and combined with BisGMA, UDMA, TEGDMA, champhorquinone, DGEBA (as coupling agent) (all available from Sigma Aldrich). As a control, Z350 XT composite (3M ESPE) was used. Twenty-four cone-shaped samples (4 x 4 x 2 mm) were used. The sisal nanofiber composite was labeled group A, sisal nanofiber with coupling agent (group B) and the Z350 XT (group C). Premolar teeth that had been extracted were filled with samples using total-etch and self-etch (3M ESPE) adhesives. The samples were evaluated using a universal testing machine (Vertical test ASL-S) and a scanning electron microscope (SEM) (JSM-6510LA). The Kruskal-Wallis test was used to process the data. The values of tensile-bond strength and microscopic bonding gaps are as follow of group A (total-etch 1.412 ± 0.324 MPa and 10,451 ± 2,175 µm; group A self-etch 0.995 ±0.470 MPa and 2,827 ± 1,975 µm), group B (total-etch 2.245 ±1.846 MPa and 5,813 ± 1,529 µm; group B self-etch 1.537 ± 0.701 MPa and 7,295 ± 3,603 µm), and Group C (total-etch 2.447 ±2.404 MPa and 5,615 ± 2,465 µm; Group C self-etch 1.875 ± 0.829 MPa and 1,590 ± 0,174 µm). The results of the analysis of tensile-bond strength have shown 0.479 (sig: p > 0.05). Nanofiller composite with total-etch showed the highest tensile-bond strength. Nanofiller composite with self-etch showed the lowest microscopic bonding gaps. This study may contribute to the invention of a new dental restorative composite material with organic filler, which is sisal nanofibers. This study has demonstrated that composites with sisal nanofiber can bond to tooth structure using two different adhesive materials.