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

Abstract

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.

Keywords: Acrylic; Brushing; Coating; PMMA; Parylene; Roughness.