Influence of laser micropatterning on the mechanical strength of dental grade zirconia

Abstract

Laser surface treatments have been explored to create controlled roughness on ceramic implants, aiming to enhance tissue-implant interaction. Among these techniques, Direct Laser Interference Patterning (DLIP) employs light interference to generate well-defined nano- and micro-scale patterns [1]. However, DLIP can induce detrimental effects on bioceramics, including microcrack nucleation, phase transformation, and potentially compromised mechanical resistance. This study investigated the impact of DLIP on the surface morphology, microstructure, mechanical properties, and biological behavior of dental-grade zirconia (3Y-TZP). An infrared nanosecond laser was employed to create linear structures with 6 µm periodicity on discs fabricated via ceramic powder pressing and sintering. Samples were further subjected to aging and mechanical cycling protocols simulating 10 years of clinical service. Confocal microscopy, scanning electron microscopy, and X-ray diffractometry were used to analyze surface and subsurface features, microstructure, and crystallographic changes, respectively. Cell viability on textured surfaces was assessed through biological tests. The nanosecond DLIP treatment introduced surface defects and heterogeneities, including groove depth variations, a recrystallized layer, microcracks, and porosity. Additionally, DLIP-induced phase transformation in 3Y-TZP was observed, further amplified by aging or mechanical cycling. While the flexural strength of laser-textured 3Y-TZP samples remained similar, a lower standard deviation was noted, suggesting enhanced reliability. Interestingly, neither aging nor mechanical cycling significantly affected flexural strength. These findings demonstrate the potential of DLIP for patterning zirconia surfaces but highlight the need for careful optimization to mitigate its detrimental effects on mechanical performance. Future research should focus on exploring alternative laser sources, pulse parameters, and post-treatment strategies to minimize microcrack formation, stabilize phase transformation, and improve overall biocompatibility.