The effect of Parylene coating on the surface roughness of PMMA after brushing.

OBJECTIVES Acrylic resins, used in the manufacturing of different types of intra-oral prostheses, are vulnerable to colonisation by microorganisms which potentially endanger the general health of the prostheses, wearers. The aim of this study was to investigate the influence of a novel coating (Parylene) on surface roughness of poly-methyl-methacrylate (PMMA) samples after simulated cleansing using an electric toothbrush and two brushing media (paste and pumice). METHODS Fifty-six square PMMA samples were fabricated. Half of the samples were coated with a uniform 10μm, coating of Parylene. All samples were subjected to simulated brushing with either paste or pumice. Changes in surface roughness were measured with a laser non-contact profilometer and compared between groups. Scanning electron microscopy (SEM) and Raman spectroscopy were utilised for surface visualisation and analysis. RESULTS In the coated samples, the mean surface roughness remained the same before and after brushing in the Paste group 2.69μm (SD=0.92 and SD=0.87 respectively), and increased from 3.73μm (SD=1.25) to, 5.05μm (SD=1.40) in the Pumice Group. In the uncoated samples, the mean surface roughness increased from 4.45μm (SD=0.92) to 6.73μm (SD=1.73) in the Paste group, and from 3.67μm (SD=0.74), to 7.50μm (SD=2.25) in the Pumice Group. Differences between the coated and uncoated groups were statistically significant (p<0.05). The surface analyses revealed that the coating remained adhered to the PMMA, although signs of partial detachment were noticed in the Pumice Group. CONCLUSION The Parylene coating resulted in a reduction of surface roughness of PMMA after brushing procedures. CLINICAL SIGNIFICANCE Parylene appears to maintain a low surface roughness of PMMA after abrasion by brushing.