Evaluation of surface roughness as a function of multiple blasting processing variables

Objectives: This study evaluated the effect of implant surface blasting variables, such as blasting media size, velocity, and surface coverage and their two- and three-way interaction in surface roughness parameters. Material and methods: Machined, grade IV titanium-alloy implants (n = 180) had their surfaces treated by a combination of 36 different blasting protocols according to the following variables: aluminum oxide blasting media particle size (50, 100, and 150 μm); velocity (75, 100, 125, and 150 m/s), and surface coverage (5, 15, 25 g/in.²) (n = 5 per blasting protocol). A single 0.46 inch nozzle of the blaster was pointed at the threaded area and spaced 0.050 inches away. Surface topography (n = 5 measurements per implant) was assessed by scanning electron microscopy. Roughness parameters Sa, Sq, Sdr, and Sds were evaluated by optical interferometry. A GLM statistical model evaluated the effects of blasting variables on the surface parameters, and their two- and three-way interaction (P < 0.05). Statistical inferences for Sa and Sq were performed after a log₁₀ transformation to correct for data skewness. Results: Prior to the log₁₀ transformation, Sa and Sq values for all processing groups ranged from ~0.5 to ~2.6 μm and from ~0.75 to 4 μm, respectively. Statistical inferences showed that Sa, Sq, and Sdr values were significantly dependent on blasting media, velocity, and surface coverage (all P < 0.001). Media × velocity, media × coverage, and media × velocity × coverage also significantly affected Sa, Sq, and Sdr values (P < 0.002). The highest levels were obtained with 100 μm blasting media, coverage for 5 g/in.², and velocity of 100 m/s. No significant differences were observed for Sds (P > 0.15). Conclusions: The blasting variables produced different surface topography features and knowledge of their interaction could be used to tailor a desired implant surface configuration.