Abstract
The focus of this study was to test the fracture resistance of upper arch dental retainers, made by two different manipulation techniques of acrylic resin. 84 plates Wraparound type retainers were made by two different manipulation techniques forming two groups (n = 42): Group 1 (Addition Technique) and Group 2 (Pressing Technique). All the retainers were duly shaped in U form with the aid of standardized plaster cast models. During the confection process the standardizing of the retainers was conducted carefully regarding their thickness and dimensions with the aid of a gauge and a straight caliper. After confection they remained immersed in water for 24 hours at 37°C. Next, they were tested through mechanical compression until fracture in a universal mechanical testing machine. Data were analyzed by Student's t test. The significance level was set at 5% (α = 0.05). It was found that the average was of 79.12 N for Group 1 and of 77.07 N for Group 2 with a standard deviation of 17.30 N and 16.31, respectively, showing that there is no significant difference in resistance for the retainers when made through any of the two methods ( P =0.788). The addition and pressure techniques of acrylic resin do not influence the resistance to compression of the upper dental retainers.
Highlights
In dentistry, the use of acrylic resin or poly methyl methacrylate (PMMA) is common among professionals, especially by orthodontists in the confection of several orthodontic devices such as space maintainers, reclaimers and dental retainers among others (SANTOS et al, 2013).Chemically activated resin is formed from the liquid, non polymerized methyl methacrylate and powder, which consists predominantly of prepolymerized spheres of poly, that, when mixed in the correct ratio, form a malleable mass with convenient physical properties (BAKER et al, 1988)
The focus of this study was to test the fracture resistance of upper arch dental retainers, made by two different manipulation techniques of acrylic resin. 84 plates Wraparound type retainers were made by two different manipulation techniques forming two groups (n = 42): Group 1 (Addition Technique) and Group 2 (Pressing Technique)
Manipulation methods described in literature for these materials are addition, wherein the polymer is incrementally saturated with its monomer and the pressing method, where powder and liquid are mixed in a ratio recommended by the manufacturer in a single event, in a 3:1 ratio of powder and liquid, respectively (BAKER et al, 1988; FALTERMEIER et al, 2007; BARLIN et al, 2011)
Summary
The use of acrylic resin or poly methyl methacrylate (PMMA) is common among professionals, especially by orthodontists in the confection of several orthodontic devices such as space maintainers, reclaimers and dental retainers among others (SANTOS et al, 2013).Chemically activated resin is formed from the liquid, non polymerized methyl methacrylate and powder, which consists predominantly of prepolymerized spheres of poly (methyl methacrylate), that, when mixed in the correct ratio, form a malleable mass with convenient physical properties (BAKER et al, 1988). In the technique that the polymer is incrementally saturated with its monomer has the advantage of increased working time and less likely to error in the confection of the plate. It has been questioned as disadvantage which the increase of the amount of monomer used in the confection of the plate could compromise the polymerization reaction (FILHO et al, 2007) and the physical properties of the material changed, besides of their characteristics of cytotoxicity (LEE et al, 2002; FALTERMEIER et al, 2007; GAURAV et al, 2008; ÖZTÜRK et al, 2011). The proposal of the authors of this study was to evaluate whether the manipulation techniques of acrylic resin for the fabrication of dental retainers influence the resistance of these devices
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