Evaluation of a glaze polishing technique for pigmented denture acrylic resin submitted to thermocycling and disinfection

Abstract

IntroductIon Acrylic resin is the most commonly used material to manufacture conventional removable prostheses; it is a low-cost material, has good adaptability to oral tissue, it is easy to manipulate, and possesses satisfactory esthetic characteristics. [1-3] The acrylic resin must mimic the soft tissue features to provide an excellent esthetic outcome, [4] and there are two techniques to do so: An extrinsic characterization in which the pigments are added after the polymerization process; and an intrinsic characterization in which the pigments are incorporated into the acrylic before the polymerization. The intrinsic technique provides good results since pigmentation is internal. The pigments age with the prosthetic material and are not influenced by damage on the prosthesis surface. [2] Some physical properties are directly linked to material longevity, such as microhardness, surface roughness, and color stability. These properties can be influenced through time due to constant temperature changes, contact to wet oral tissues, the disinfection process used, and contact to different solutions. [1,5-13] Different polishing techniques have been used in an attempt to improve these characteristics; the polish can be mechanical, performed with different polishing pastes and soft brushes, or Aims: Compare the mechanical and physical properties of two polishing techniques for acrylic resins under the influence of disinfection. Materials and Methods: Two hundred and eight circular samples (10 mm diameter × 3 mm height) were manufactured, with 160 for the color stability, hardness, surface roughness, and wettability (n = 10) analyses, and 48 for the scanning electron microscopy and atomic force microscopy evaluation (n = 1). Two brands of prosthesis acrylic resin, Onda Cryl and Lucitone, were used to manufacture the samples. Half of the samples were intrinsically pigmented with a purple acrylic pigment (Policor) at 7% of the total weight in powder; half of those received the mechanical polish with sand paper under constant water irrigation in a universal polishing machine at 300 rpm (control), and half received a uniform coat of a photopolymerized glaze (Megaseal) to be tested. The samples were kept immersed in distilled water for 24 h before the initial measurements (T0), afterward, they were divided into two disinfection procedures; half were disinfected through microwave energy and half through cleaning tablets (Efferdent) for 60 days (T1). Results: The glaze polished groups presented inferior chromatic stability and the pigments prevented discoloration for the glaze polish. The disinfectant solutions promoted a superficial degradation of the acrylic resin for both polishing techniques. Lucitone presented higher hardness values than Onda Cryl (P < 0.001) and the glaze technique had higher hardness values than the mechanic polish. Conclusion: The photopolymerized glaze improved some characteristics of the acrylic resin, such as the surface hardness and roughness suggesting it is an adequate polish for acrylic resins.

The Effect of Polishing Techniques on Surface Hardness of De-flex Denture Base

“…Resistance to the micro crack because of the De-flex acrylic resin contains extra hard fibers in the material. The outcomes of the current researches are in agreement with Goiato et al (22) the glaze polished groups presented higher surface hardness results. Also in agreement with Sesma et al (23) glaze crack may have happened due to the inflexibility that the glaze layer need after the heating of light and an elevated surface rigidity and a reduction in the influence strength and transverse winding strength of resins surface coated with a surfaces glaze.…”

Effect of Different Solutions on the Colour Stability of Nanoparticles or Fibre Reinforced PMMA

“…A study has found that a glossy, smooth surface prevents discolouring films from forming, impedes plaque formation, and assists the removal of plaque [17]. The structure of the acrylic resin in combination with the accumulation of substances can also impact the colour stability, particularly if the material has a higher surface roughness [8,38]. Polychronakis et al [36] assessed the impact that denture cleaners had on the surface roughness, colour and gloss of nylon and heat-polymerised acrylic denture base resins before and after immersion in test liquids for 30 days.…”

“…Hong et al [18] found that there was a positive correlation between colour change in acrylic resins and immersion time as a result of monomer leaching out and the absorption of water. Furthermore, Goiato et al [38] concluded that any monomer released during storage could interact with the glaze layer, resulting in increased colour change. The primary discolouring mechanism is likely to be the sorption of liquids (solutions) [9].…”

Effect of Cleansers on the Colour Stability of Zirconia Impregnated PMMA Bio-Nanocomposite

“…It has been reported that a smooth surface prevents the formation of discolouring films, affects plaque formation and facilitates its removal [10]. The composition of the acrylic resin and built-up substances can also influence the colour stability, especially if the surface roughness is higher [23]. Polychronakis et al evaluated the influence of denture cleaners on colour, surface roughness and gloss of nylon and heat polymerized acrylic denture base resins before and after 30 days of immersion [12].…”

“…Goiato et al found that the release of monomer during storage could interact with the glaze layer and cause increased colour change [23]. In addition, residual monomer can react with pigments inside the polymer, causing further colour changes [3].…”