Influence of Processing Techniques on Microhardness and Impact Strength of Conventional and Reinforced Heat Cured Acrylic Resin: A Comparative Study

Abstract

This study determined and compared the influences of various processing techniques including air circulating oven (ACO), dry heat oven (DHO) and water bath (WB) on the impact strength (IS) and microhardness (HV) of the conventional heat cure acrylic resin (CHCAR) and rubber reinforced heat cure acrylic resin (RRHCAR). Samples were fabricated using CHCAR (control Group A; n=114) and RRHCAR (experimental Group B; n=114). Group A and B were further divided into subgroups according to processing techniques: ACO, DHO and WB (n=38 each) for both testing variables microhardness and impact strength (n=19 each). Charpy testing machine and Vickers microhardness tester were utilized. Analysis of variance was applied to determine the presence of significant differences among processing techniques while P-value ≤ 0.05 was considered as significant. Water bath (P-value [0.001) and DHO technique (p-value [0.001) showed significant differences between both groups� impact strength and microhardness. Microhardness of group A and B showed a significant difference (p-value 0.002) when processed by ACO. Impact strength and micro hardness were improved in RRHCAR compared to CHCAR processed by ACO and DHO in comparison to WB technique. Rubber reinforced heat cure acrylic resin revealed improvement in the impact strength and microhardness. The air circulating oven exhibited highest microhardness in both testing materials. Dry heat oven showed improved values of impact strength in conventional heat cure acrylic resin.

Mechanical Properties of the Modified Denture Base Materials and Polymerization Methods: A Systematic Review

“…The characteristics of the included papers are presented in Table 3 . The inclination toward using a conventional heat cure denture base PMMA polymer was seen as very common in the majority of papers [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. However, a few studies focused on experimenting with a chemically modified PMMA polymer by incorporating a monomer either in pre-polymerized polymer powder of PMMA [ 40 ] or in unpolymerized MMA liquid [ 23 , 29 ].…”

“…Inclination towards the use of PEEK material as denture base was seen only in one research paper [ 33 ]. Only two papers evaluated the mechanical properties of rubber reinforced PMMA denture base material [ 19 , 31 ].…”

“…In the majority of the papers, compression moulding using a water bath was observed as the dominant technique for the polymerization of denture base [ 19 , 20 , 21 , 22 , 24 , 28 , 29 , 30 , 31 , 32 , 35 , 36 , 37 , 38 , 39 ]. However, the dry heat polymerization method was also explored by some investigators with a promising effect on mechanical properties [ 27 , 31 ]. The use of high pressure during heat polymerization also produced encouraging results on the mechanical properties of denture base material [ 24 , 30 ].…”

“…Among the other notable polymerization methods used were microwave [ 21 , 23 , 25 , 26 , 38 , 39 ], injection moulding [ 20 , 36 , 37 ] autoclave [ 19 , 23 ], air circulating [ 31 , 32 ], and dry heat [ 31 , 32 ].…”

“…FS was the most commonly used testing parameter employed to evaluate the mechanical properties [ 20 , 23 , 24 , 25 , 26 , 27 , 29 , 30 , 32 , 34 , 35 , 36 , 37 , 39 , 40 ]. The investigators were also interested to see TS [ 19 , 28 , 33 ], SH [ 19 , 21 , 22 , 24 , 27 , 31 , 38 ] and IS [ 19 , 27 , 28 , 31 , 33 , 35 ]. In contrast, FT was evaluated in only one research paper [ 25 ].…”