The effect of different chemical intra-oral prostheses cleansers on the surface properties of Parylene-coated PMMA.

The purpose of this study was to investigate the effect of different chemical intra-oral prosthesis cleansers on the surface properties of Parylene-C coated and non-coated polymethyl methacrylate (PMMA). A total of 120 PMMA samples were prepared. Half of the samples were coated with 10 µm of Parylene-C. Samples were exposed to either air (control) or one of two types of denture cleansers, an alkaline peroxide cleanser (Steradent) or a neutral peroxide cleanser with enzyme (Poligrip). Surface roughness (Ra) and surface free energy (SFE) values were measured and compared between groups. Scanning electron microscopy was used for visual analysis. The samples coated with Parylene exhibited significantly lower mean Ra values compared to the non-coated samples (p<0.001). Immersion in Steradent increased the roughness of non-coated PMMA, but its effect was minimized on the coated surfaces. SFE increased for the samples exposed to air and Poligrip, but decreased for the samples exposed to Steradent.

Effect of different initial finishes and Parylene coating thickness on the surface properties of coated PMMA.

STATEMENT OF THE PROBLEM: The colonization of microorganisms on acrylic resin dentures may result in denture-induced stomatitis. No efficient coating has yet been proposed to address this issue. PURPOSE: The purpose of this in vitro study was to assess the effect of various initial surface finishes and different Parylene coating thicknesses on the surface roughness (Ra) and surface free energy (SFE) of Parylene coated polymethyl methacrylate (PMMA). MATERIAL AND METHODS: One hundred and sixty PMMA specimens were produced and divided into 8 groups as follows: group A: uncoated, 1000 grit finish; group Ap1: 10 µm Parylene coated, 1000 grit finish; group B: uncoated, 1200 grit finish; group Bp: 10 µm Parylene coated, 1200 grit finish; group C: uncoated, 2400 grit finish; group Cp: 10 µm Parylene coated, 2400 grit finish; group Ap2: 20 µm Parylene coated, 1000 grit finish; group Ap3: 30 µm Parylene coated, 1000 grit finish. The Ra of all specimens was measured with a noncontact profilometer. To calculate the SFE, the Owens-Wendt approach was applied after measuring the contact angles with a goniometer. The topography of the specimens was observed by scanning electron microscope. RESULTS: Groups Ap1 and Bp presented significantly lower Ra values compared with their respective uncoated groups A and B (P<.001). No statistical difference was found between the Ra values of groups C and Cp, between A and Ap3, and between Ap2 and Ap3. The SFE values of the coated groups were significantly higher than the SFE values of the uncoated groups with the same initial finish (P<.001). CONCLUSIONS: Coating with a 10-µm layer of Parylene C resulted in lower Ra values for the rougher groups and increased SFE values. Increasing the coating thickness resulted in an increase of the Ra.

Complete denture copy technique-A practical application.

The copy denture technique is a misnomer for the clinical and laboratory procedures involved in making complete dentures that replicate most of the features of the original prosthesis. The aim is to replicate the good features of an otherwise successful prosthesis that now requires replacement and to alter the poor features and so it is strictly speaking not a copy. There are many purported advantages to this technique which include reduced treatment time, increased patient acceptance especially for the elderly who may not adapt so well to a new prosthesis, maintenance of tooth position and vertical dimension. A typical case is presented illustrating the clinical stages involved with a discussion of the merits of this technique.

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.