Optimized regression model for microhardness of experimental dental composite resins with nano-hydroxyapatite filler particles

Abstract

ABSTRACT Background: Bioactive materials produce a biological reaction such as stimulation of pulpal cells for dentinal repair and induction of the formation of hydroxyapatite. Aim: The study was conducted to evaluate the microhardness of experimental dental composite resins (EDCR) containing nano-hydroxyapatite, zirconia, and glass filler particles. Materials and Methods: The EDCR was prepared with varying concentrations of barium aluminum fluoride glass (5–20 nm), zirconia (4–11 nm), and hydroxyapatite (20–80 nm) filler particles added to the organic matrix. The L9 orthogonal array was used to prepare a sample size of 27 samples. Disc-shaped specimens of 10 mm diameter and 4 mm thickness were prepared using the American Society for Testing and Materials E384 standard for testing the microhardness. The Taguchi’s method of optimization was used to obtain a composite with optimum microhardness. A regression model was developed. Results: EDCR with 23.7% of zirconia, 27.5% of nano-hydroxyapatite, and 20% of glass filler particles gave the optimum microhardness of 222.67 HV. The confirmatory experimental test of EDCR gave a microhardness of 225 HV. The model developed with regression equation for the microhardness was 60–123 Z + 114 H + 17.8 G + 2.48 ZH − 0.02 HG + 0.97 Z2 − 3.40 H2. The difference between the R 2 (99.9) and adjusted R 2 values (99.4) is <0.5, this shows that the model is acceptable. Conclusion: The EDCR developed after using Taguchi’s method of optimization had microhardness superior to that of the commercially available composite resins.