Effect of Nd: YAG Laser on Hardness and Color Change of High Impact Acrylic Denture Base Material

Polymethyl methacrylate (PMMA) is widely used for denture bases but suffers from limited fracture resistance; high impact acrylic, enhanced with butadiene styrene rubber, improves strength. Lasers, particularly the Nd: YAG type, have been used to modify acrylic surfaces, mainly to enhance bonding with soft liners; however, little is known about the effect of Nd: YAG laser treatment on other properties like hardness and color, which are critical for clinical performance and esthetics. The study objective was to evaluate the effect of nanosecond pulsed Nd: YAG laser irradiation with two different hatch values on the hardness and color of high-impact acrylic denture base material. Fifty acrylic samples were made and divided into three groups: untreated control, laser-treated at 0.03 mm hatch (H3), and laser-treated at 0.05 mm hatch (H5). Hardness was measured using a Shore D durometer, and color changes were evaluated with a digital colorimeter using the CIELab system; chemical surface analysis was conducted by FTIR spectroscopy. Statistical analysis included ANOVA and independent t-tests, with a significance level at p ≤ 0.05. The results of FTIR spectra showed no chemical changes in acrylic after laser treatment, and hardness values did not differ significantly among groups (p > 0.05); however, laser treatment resulted in a significant color change, with ΔE values corresponding to a “much” perceptible color difference, which may compromise esthetics (p ≤ 0.05). In conclusion, Nd: YAG laser treatment does not alter the chemical structure or hardness of high-impact acrylic denture base material but induces significant color changes that could adversely affect esthetic outcomes