Mechanical and thermal properties of polyamide versus reinforced PMMA denture base materials

Abstract

PURPOSEThis in vitro study intended to investigate the mechanical and thermal characteristics of Valplast, and of polymethyl methacrylate denture base resin in which different esthetic fibers (E-glass, nylon 6 or nylon 6.6) were added.MATERIALS AND METHODSFive groups were formed: control (PMMA), PMMA-E glass, PMMA-nylon 6, PMMA-nylon 6.6 and Valplast resin. For the transverse strength test the specimens were prepared in accordance with ANSI/ADA specification No.12, and for the impact test ASTM D-256 standard were used. With the intent to evaluate the properties of transverse strength, the three-point bending (n=7) test instrument (Lloyd NK5, Lloyd Instruments Ltd, Fareham Hampshire, UK) was used at 5 mm/min. A Dynatup 9250 HV (Instron, UK) device was employed for the impact strength (n=7). All of the resin samples were tested by using thermo-mechanical analysis (Shimadzu TMA 50, Shimadzu, Japan). The data were analyzed by Kruskal-Wallis and Tukey tests for pairwise comparisons of the groups at the 0.05 level of significance.RESULTSIn all mechanical tests, the highest values were observed in Valplast group (transverse strength: 117.22 ± 37.80 MPa, maximum deflection: 27.55 ± 1.48 mm, impact strength: 0.76 ± 0.03 kN). Upon examining the thermo-mechanical analysis data, it was seen that the E value of the control sample was 8.08 MPa, higher than that of the all other samples.CONCLUSIONAlthough Valplast denture material has good mechanical strength, its elastic modulus is not high enough to meet the standard of PMMA materials.

Effect of Denture Cleansers on Flexural Strength, Color Stability and Surface Roughness of Flexible and Microwave cured Acrylic Resin

“…Moreover, this result is in compliance with a study made by Salman and Saleem 37 which revealed that denture cleansers decreased the flexural strength of nylon denture base materials. On the contrary to our study, Soygun et al 42 , found that polyamide based For both groups (flexible denture base resin and microwave cured denture resin groups); Corega Tabs recorded the statistically significant lowest flexural strength values (53.78±1.38,60.23±1.49 respectively). This was attributed to the fact that peroxide radical formed from alkaline peroxide denture cleanser might attack the polymer chain backbone causing polymer degradation producing decrease in strength 31 .…”

Deterioration of polymethyl methacrylate dentures in the oral cavity

“…1b and 1c) showed agreement that long-term exposure to the oral cavity can lead to a decrease in hardness of the surface. On the other hand, occlusal force and thermal changes due to food and drink can be transmitted to the dentures (>100 µm) 5,7,8) , supporting that the decrease in hardness is caused not only by physiochemical factors but also by biological factors such as salivary enzymes and/or oral microbiota.…”

“…This deterioration is likely to be not only due to physiochemical factors such as heat and mechanical loading, but also to biological factors such as salivary enzymes and bacterial metabolic activity 2) . There are many studies about the physiochemical deterioration of surface properties and bending strength of PMMA due to water absorption 3) , chemical reagents such as ethanol and acid 4) , mechanical stress such as occlusal force 5) and thermal stress such as dietary components [6][7][8] . On the other hand, the elution of monomers from PMMA prosthesis 9,10) is the only study topic concerned with biological factors, such as salivary enzymes and oral microbiota.…”

A Review: Flexible Removable Partial Dentures

“…[1] When compared with PMMA, valplast (the most commonly used thermoplastic nylon) has higher transverse strength (117.22 ± 37.80 MPa) as well as impact strength (0.76 ± 0.03 kN). [2] III.…”

“…The elastic modulus of flexible nylon (valplast) is lesser than that of PMMA. [2] The valplast shows clinically significant chromatic instability, so the flexible removable partial denture might show staining and discoloration with time. [9] As flexible dentures flex under occlusal load so these can notmaintain the vertical dimension.…”