Flexural Strength Of Acrylic Resin Research Articles

The effect of different concentration of emodin nanoparticles, as an antibacterial agent, on the flexural resistance of acrylic resin used in orthodontics: An in vitro study

The aim of this study was to investigate the impact of emodin nanoparticles (n-Emo) on the flexural strength of acrylic resin used in orthodontics. A total of 24 acrylic resin discs were prepared according to ISO:20795-1 and divided into four groups (n=6): 0% n-Emo, 0.5% n-Emo, 1% n-Emo, and 2% n-Emo. The flexural strength of each group was measured using the Universal Testing Machine. One-way analysis of variance (ANOVA) and Tukey tests were used to analyse the data. The highest flexural strength values were observed in the groups containing 0% and 0.5% concentrations of n-Emo, while the lowest mean flexural strength was recorded in the group containing 2% concentration of n-Emo. There were significant difference in flexural strength values between the groups containing 0% with those containing 1% and 2% concentrations (P=0.045, P=0.011, respectively), as well as between those containing 0.5% and 2% concentrations of n-Emo (P=0.041). The results of the study showed that the incorporation of n-Emo had a negative impact on the flexural strength of the acrylic resin utilized in orthodontics. Nonetheless, the mean flexural strength values of all groups fell within the normal range, implying that the addition of n-Emo did not jeopardize the mechanical properties of the acrylic resin. It is therefore conceivable that the use of n-Emo as an antimicrobial agent in acrylic resin could be a promising approach to reducing enamel demineralisation and dental caries, while preserving its mechanical properties. This study was approved by the ethics committee of the Tehran University of Medical Sciences (1401-2-398-54892).

Novel Denture Cleanser Formulated From Virgin Coconut Oil and The Anionic Emulsifier Against Candida albicans Biofilms Formed on 96-Wells Plate and Acrylic Resin Surfaces

Abstract The objectives of this study were to investigate the inhibitory effect of coconut oil denture-cleansing (CDC) formula against Candida albicans biofilm formed on 96-wells plate and acrylic surfaces at various immersion times and to determine the effects on physical properties of heat-cured acrylic surfaces. A total of twenty-seven CDC formulas were prepared. All CDC formulas were evaluated the stability and anticandidal activity by freeze-defrost cycles and broth microdilution assays, respectively. The formula 22th (F22) containing 0.3 g of anionic emulsifier at a ratio 40:60 of virgin coconut oil to distilled water showed the highest stability and anticandidal activity. The percent inhibition against C. albicans biofilm formed on 96-well plate and acrylic resin surfaces of the F22 after 8 hours of immersion were 86.87 ± 0.65%, and 91.19 ± 1.81%, respectively. However, the F22 had significantly lower inhibitory activity than 0.12% chlorhexidine gluconate (P <0.05). Furthermore, flexural strength of acrylic resin specimens was determined using a 3-point bending test and surface roughness was measured with a profilometer. The flexural strength and the change in surface roughness of F22 were not significant different compared with chlorhexidine and distilled water after 8 hours immersion for 30 days (P >0.05). In conclusions, F22 which containing 0.3 g of anionic emulsifier at the ratio of coconut oil to distilled water at 40:60 exhibited the potent inhibitory activity to Candida albicans biofilms and had no significant effect on the flexural strength and surface roughness of acrylic resins after immersion for 30 days. Keywords: Denture cleanser, Coconut oil, Anionic emulsifier, Biofilm, Candida albicans, Acrylic resins

The effect of non-dental glass fiber volume fraction on flexural strength of heat cured acrylic resin

Background: Heat-cured acrylic resin is a material that is often used for the manufacture of removable partial dentures in dentistry because it uses simple equipment, relatively inexpensive, and is easy to repair. Acrylic resin also has a disadvantage, such as the low value of flexural strength so that it can cause the denture to fracture. This study determine the effect of non-dental glass fiber volume fraction on the flexural strength of heat cured acrylic resin. Method: This research are post-test only control group design. Acrylic resins were divided into four groups (6 sample each group), group 1 without the addition of non-dental glass fiber or 0% and heat cured acrylic resin group with the addition of non-dental glass fiber 1%,2%, and 3% (group 2, 3 and 4). Result: The average flexural strength of acrylic resin with a volume fraction of 2% of non-dental glass fiber had the highest value compared to other groups. The results of the Mann-Whitney test from several test groups showed significant differences in the value of flexural strength from each group (p<0.05), except for the 0% and 3% group. Conclusion: There is an effect of volume fraction of non-dental glass fiber on the flexural strength of heat cured acrylic resin.

Effects of Nanocrystal Cellulose from Bamboo on the Flexural Strength of Acrylic Resin: In Vitro.

The purpose of this study is to evaluate the effects of nanocrystal cellulose (NCC) from bamboo on the flexural strength of heat-cured acrylic resin. A total of 35 specimens (3.3 mm × 10 mm × 64 mm) were prepared and the specimens were divided into five groups of seven specimens each. Group 1 used conventional acrylic resin that was prepared based on the instructions of the manufacturer (0%). The filled NCC from bamboo fiber in four concentrations (0.25, 0.5, 1, and 2% w/w) was used in the four-reinforcing resin workpiece groups. The specimens were loaded until failure occurred on a three-point bending test machine. One-way analysis of variance and Dunnett’s multiple comparison test at a 95% confidence level were used to determine the statistical differences in the flexural strength among the five groups. The results found that the average flexural strength of five specimen groups (0, 0.25, 0.5, 1, and 2% w/w) were 60.11 ± 2.4, 60.75 ± 2.18, 66.50 ± 5.08, 56.04 ± 0.31, and 48.05 ± 2.61 MPa, respectively. The flexural strength of 0.5 mg% w/w NCC-reinforced acrylic resin was significantly higher than the control group (p < 0.01). The reinforced NCC from bamboo fiber to acrylic resin improved the flexural strength properties.

The effects of TiO2 Nanoparticles on Flexural Strength of Self-Polymerized Resins: In Vitro Study

Self-polymerized resins are extensively utilized in removable prosthodontics for a variety of applications in maxillofacial rehabilitation, including interim appliances, repairs, relines, customized trays, and record bases. These materials, on the other hand, are prone to fracture. The goal of this study was to see how titanium dioxide nanoparticles affected the flexural strength of self-polymerized resins. A total of 30 samples were prepared from self-polymerized acrylic resins (control, 1% TiO2, and 2% TiO2). Using a universal testing machine, all samples were subjected to a flexural strength test until they fractured. The data were analyzed with SPSS version 20, and the Duncan test and ANOVA tests were used to compare all groups. The results showed that TiO2 increased the flexural strength of acrylic resins substantially when compared to the control. Furthermore, significant differences (P&lt;0.001) were found among all groups. The addition of TiO2 increases the flexural strength of acrylic resins.

The Flexural Strength of Acrylic Resin Repairs Reinforced with Different Nanoparticles

Objective: The purpose of this study is to assess the flexural strength of heat-cure acrylic resins repaired with auto-polymerized acrylic resins modified with 1%, 3% TiO2, Fe2O3, CuO nanoparticles. Materials and Methods: Fifty-six samples (65x10x2.5 mm) were prepared with heat-cure acrylic resins and divided into 7 groups (8 samples each) to make repair procedure: Specimens were repaired with unmodified (control group) and 1%, 3% TiO2, Fe2O3, CuO added auto-polymerized acrylic resins. For 3-point flexural test, the force was loaded at 5 mm/min crosshead speed directly to the middle part of the repaired acrylic resin with a Universal Testing Machine. Data were analyzed statistically by ANOVA followed by Tukey test (p &lt; 0.05). Results: Control group showed lower strength values than the other groups. 1% TiO2 nanoparticle added group showed significantly higher flexural strength values than 3% added groups and control group (p &lt; 0.05). The highest strength value was measured in 1% TiO2 group. Conclusion: Acrylic resins reinforced with 1% TiO2 developed higher strength than resins reinforced with 3 % TiO2, Fe2O3, CuO nanoparticles. Adding 1% nanoparticles to resins could improve the fracture strength of materials.

Effect of incorporating aluminum oxide nanoparticles on thermal conduction and flexural strength of acrylic resins

The mechanical and thermal properties of polymethyl methacrylate, as the most commonly used material for the fabrication of dental prostheses, should be improved due to its structural weaknesses. The present study aimed to compare the flexural strength and thermal conduction of two heat-cured and self-cured acrylic resins reinforced with aluminum oxide nanoparticles. In this in vitro study, a total of 114 samples consisting of heat- and self-cured three subgroups (1% and 3% Al2O3 and the control) with 66 samples for the thermal conduction (n = 11) and 48 samples for the flexural strength (n = 8) tests were prepared. Flexural strength was assessed with a three-point bending test using a universal testing machine. One-way ANOVA was applied for data analysis, followed by post hoc Tukey paired group comparison tests (P < 0.05). An increase in the aluminum oxide nanoparticle percentage in acrylic resins increased the thermal conduction in heat-cured acrylic resin from 2.142 ± 0.0298 to 2.487 ± 0.0359 m (2)/sec and in self-cured acrylic resin from 2.0150 ± 0.02646 to 2.1475 ± 0.04031 m (2)/sec and decreased the flexural strength in heat-cured acrylic resin from 60.521 ± 8.9278 to 49.747 ± 4.4729 MPa and in self-cured acrylic resin from 37.573 ± 10.9237 to 35.569 ± 6.1531 MPa (P < 0.05). The incorporation of aluminum oxide nanoparticles adversely affected acrylic resin flexural strength; however, it increased the thermal conduction.

Correlation between the water sorption and the flexural strength in heat-cured acrylic resin with different fillers

Purpose: The purpose of this study was to correlate the water sorption and flexural strength of acrylic resin reinforced with three different fillers. Materials and Methods: A Flexural strength test using a universal testing machine was done for 132 heat-cured acrylic resin specimens reinforced with titanium oxide nanoparticle, aluminum oxide nanoparticle, silanated, and non silanated glass fibers (n=12). Another 132 discs with the same fillers were evaluated for water sorption at 37°C ± 1°C using a four-digit electric balance. Specimens were stored in distilled water for 120 days. Statistical analysis was done using Pearson correlation (p < 0.05) to correlate the water sorption and the flexural strength at each nanoparticle concentration. Results: The correlation between the water sorption and the flexural strength was positive for the titanium oxide and aluminum oxide nanoparticles, and negative for the glass fibers specimens. However, these correlations were non-significant. Conclusion: Water sorption of heat-cured acrylic resin has no correlation with the flexural strength with the addition of titanium oxide nanoparticle, aluminum oxide nanoparticle, silanated and non silanated glass fibers

Influence of the addition of glass fibers reinforcements in the flexural strength of acrylic resin

Objective: To evaluate the influence of glass fiber reinforcements used in nautical and sports products on the flexural strength of acrylic resin. Materials and methods: Thirty thermoactivated acrylic resin bars (25 x 10.5 x 3.3 mm) were used. The samples were shared in 3 groups: bars with no glass fiber (control group, n = 10), bars reinforced with glass fiber and 0.18 mm thickness (group F1, n = 10) and bars reinforced with glass fiber and 0.80 mm thickness (group F2, n = 10). After 48 hours, samples were submitted to compression test in order to evaluate flexural strength. Obtained data were statistically analyzed with significance level of 5 %. Results: It was observed that the use of glass fiber effectively increased the flexural strength compared to the control group; the thickness of the glass fiber, however, did not present statistical differences. Conclusion: The use of fiber glass is a simple and cost-effective alternative to improve acrylic resin performance.KeywordsFlexural strength; Water sports; Dentures.

Effect of zinc oxide nanoparticles on the flexural strength of polymethylmethacrylate denture base resin.

This study evaluated the flexural strength of polymethyl methacrylate (PMMA) reinforced with various concentrations of zinc oxide (Zn O) nanoparticles. Nano ZnO was added in 0, 0.4, 0.6, 0.8, 1.2 and 1.4 percentage to PMMA denture base material. 60 specimens of heat cure polymerizing acrylic resin of dimensions 10mm x 4mm x 80mm were fabricated in accordance to ISO 20795-1-2013. The specimens were divided into 6 groups. Acrylic specimens were processed according to manufacturer's instruction. Three-point bending test was performed to evaluate the flexural strength. Surface analysis was performed with scanning electron microscopy (SEM) to observe the fracture surfaces of specimens. ANOVA and Tukey tests were used for the statistical analysis (p < 0.05). Statistical analysis revealed significant differences in strength between groups. The flexural strength improved with the addition ZnO nanoparticles. Highest mean value was observed in Group nZn -14 (91.31 MPa) and lowest in control Group nZn-0 (61.36 MPa). ANOVA and Tukey's honestly significance test found statistical significant differences among the groups ( p<0.001). The addition of ZnO nanoparticles in all concentrations increased the flexural strength of acrylic resin when compared to the control group.

Comparative Evaluation of the Flexural Strength of Heat Polymerized Acrylic Resin with the Addition of 8% and 13% Aluminum Oxide Powder: An In-vitro Study

Introduction: Acrylic resins have been used successfully as denture bases. However, acrylic resin denture base materials are brittle and have poor strength and thermal conductivity. Therefore, it is essential to improve the flexural strength of heat polymerized acrylic resin. The present study aimed to evaluate and compare the flexural strength of heated polymerized acrylic resin with the addition of 8% and 13% aluminum oxide powder. Methods: In total, 90 acrylic specimens were fabricated and divided into three groups of A1 (unmodified heat-cured denture base resin), A2 and A3 (heat-cured denture base resin polymer modified with 8% and 13% by weight of aluminum oxide powder, respectively). The specimens were stored in distilled water for one week, and flexural strength was assessed using a universal testing machine. Data analysis was performed using one-way analysis of variance (ANOVA). Results: Comparison of groups A1 and A2 (8%) showed the highest flexural strength (85.94 MPa) in group A2. A significant increase was observed in the values of flexural strength with 13% alumina addition. Comparison of groups A1 and A3 (13%) showed the highest flexural strength (86.41 MPa) in group A3, and the difference in the mean values of flexural strength was considered significant. Moreover, comparison of groups A2 and A3 indicated the highest flexural strength in group A3. Conclusion: Addition of alumina to conventional heat-cured acrylic resin shows increase in flexural strength. Increasing the flexural strength of acrylic resin base materials could results in higher clinical success rate.

Efecto de la incorporación de nanopartículas de óxido de zinc en la resistencia a la flexión de las resinas acrílicas autopolimerizadas.

Background: Auto-polymerized acrylic resins are commonly used in many applications in dentistry including in maxillofacial rehabilitation such as interim prostheses, denture repair, reline, orthodontic appliances, record base, among others. These substances, however, have some negative aspects such as poor mechanical properties. Aim: The objective of the current study was to evaluate the effect of incorporating zinc oxide nanoparticles to auto-polymerized acrylic resins on their flexural strength. Materials and methods: Thirty specimens were made from auto-polymerized acrylic resins, divided into three main groups (1 control and 2 experimental). Each group had ten specimens. The two experimental groups comprised the zinc oxide powder at 1% and 2% concentrations, respectively. Acrylic specimens were fabricated with the dimension of 65mm length, 10mm width and 2.5mm thickness according to ISO 1567 specification 1999. Each specimen was subjected to the flexural strength test by a universal testing machine. The crosshead speed for the flexural strength test was 5mm/min until fracture occurred. The SPSS version 16 was utilized for the statistical analysis. The ANOVA and Tukey were used for the comparison among all groups. Results: there was a significant increase (p&lt;0.001) in the flexural strength of the acrylic resins following the addition of zinc oxide particles (control group: 133.27 SD 1.73, ZnO 1%: 154.28 SD 2.90, ZnO 2%: 176.45 SD 0.94). Conclusions: The incorporation of zinc oxide nanoparticles has a significant effect on the flexural strength of auto-polymerized acrylic resins.

Effect of green gold nanoparticles synthesized with plant on the flexural strength of heat-polymerized acrylic resin.

The aim of this study was to investigate the effect of gold nanoparticle on the flexural strength of polymethyl methacrylate (PMMA). PMMA specimens (65 mm × 10 mm × 3.3 mm) containing different sizes (45 nm, 55 nm, and 65 nm) and concentrations (0.05% and 0.2%) of gold nanoparticles were prepared, along with a control group containing no added nanoparticles. Flexural strength of all specimens was measured, and one-way ANOVA and Tukey-Kramer post hoc multiple comparisons tests were performed to identify statistical differences between groups. The addition of gold nanoparticles increased the flexural strength of acrylic resin. Significantly greater increases were obtained with lower concentrations (0.05%) when compared to higher concentrations (0.20%). Differences in concentrations of gold nanoparticles added to PMMA have significantly different effects on PMMA flexural strength, whereas differences in sizes of gold nanoparticles added to PMMA do not significantly affect its flexural strength. Accordingly, adding gold nanoparticles to PMMA may enhance the mechanical properties of denture bases used in clinical practice.

A Novel Silica-Nylon Mesh Reinforcement for Dental Prostheses

Statement of the Problem. Acrylic resin-based dentures can fracture; thus they can benefit from reinforcement.Purpose. To evaluate the effect of a novel reinforcement structure made of nylon fibers and silica particles on the flexural strength of acrylic resin after relining and aging.Materials and Methods. Bar-shaped specimens were fabricated and divided into the following experimental groups (n=20): control (acrylic resin without reinforcement); acrylic resin nylon fiber-reinforced; acrylic nylon and silica fiber-reinforced; acrylic nylon fiber-reinforced-relined; acrylic nylon and silica fiber-reinforced-relined. Half of the specimens from each group were aged by thermomechanical cycling (10000 cycles between 5°C and 55°C) before flexural strength testing to failure using a universal testing machine. Data (MPa) were statistically analyzed using analysis of variance and Tukey tests (α=5%).Results. Adding nylon fibers or silica-containing nylon fibers significantly increased the flexural strength of all the groups tested. Within the similar groups processed in the same manner, the relining procedure reduced the flexural strength of the specimens, whereas aging process had no effect on the strength values.Conclusion. Incorporating a silica-containing nylon fiber mesh into acrylic resin yielded the greatest flexural strength for the evaluated structures.

The Effect of Silica and Prepolymer Nanoparticles on the Mechanical Properties of Denture Base Acrylic Resin.

To evaluate how hydrophobic nanoparticle silica and prepolymer affect the flexural strength, surface hardness, surface roughness, and resilience of a denture base acrylic resin. A total of 40 denture base acrylic resin specimens with dimensions 65×10×3 mm3 were fabricated in this study. Specimens were divided into five experimental groups (n = 8) according to surface-treated silica and prepolymer concentration incorporated into the acrylic resin (weight %) prior to polymerization: G1 acted as control, no fillers were used in this group. G2: 1 wt% 12 nm silica nanoparticles; G3: 5 wt% 12 nm silica nanoparticles; G4: 1 wt% 12 nm prepolymer nanoparticles; G5: 5 wt% 12 nm prepolymer nanoparticles were added into the acrylic mixture. Acrylic specimens were polymerized according to the manufacturer's instructions. Three-point bending test was performed to evaluate the flexural strength and the resilience of the specimens. Then, a digital profilometer was used to determine the surface roughness of the specimens. Surface hardness was conducted by a digital Shore D hardness testing machine. Surface analysis of one specimen in each group was performed with a scanning electron microscopy (SEM) to observe the fracture surfaces of specimens. ANOVA and Tukey tests were used for the statistical analysis (p<0.05). Statistical analysis revealed significant differences among the groups. All groups showed poor flexural strength as compared with the control (p<0.05). Regarding resilience, silica 5% showed the highest value whereas silica 1% showed the lowest value. Regarding Shore D hardness, silica 1% had the lowest hardness whereas polymer addition did not significantly influence the hardness of the acrylic resin (p<0.05). Furthermore, silica 1% presented the highest roughness as compared with the other groups (p<0.05). SEM images indicated some porosity and voids on fracture surfaces. Both the silica and prepolymer incorporation into acrylic resin adversely affected the flexural strength of the acrylic resin compared to control group. In all concentrations, prepolymer incorporation resulted in increased flexural strength of acrylic resins compared to silica addition. The greater concentrations of the fillers resulted in increased mechanical properties of the acrylic resin.

The pH effect of solvent in silanization on fluoride released and mechanical properties of heat-cured acrylic resin containing fluoride-releasing filler.

This study aimed to evaluate the effect of an acidic-adjusted pH of solvent in silanization on the amount of fluoride released and mechanical properties of heat-cured acrylic resin containing a silanized fluoride-releasing filler. The experimental groups were divided into 4 groups; non-silanized, acidic-adjusted pH, non-adjusted pH, and no filler as control. For fluoride measurement, each specimen was placed in deionized water which was changed every day for 7 days, every week for 7 weeks and measured. The flexural strength and flexural modulus were evaluated after aging for 48 h, 1, and 2 months. Two-way ANOVA indicated significant differences among groups, storage times, and its interaction in fluoride measurement and flexural modulus. For flexural strength, there was significant difference only among groups. Acidic-adjusted pH of solvent in silanization enhanced the amount of fluoride released from acrylic resin, while non-adjusted pH of solvent exhibited better flexural strength of acrylic resin.

Effects of Denture Cleansers on Heat-Polymerized Acrylic Resin: A Five-Year-Simulated Period of Use

This study evaluated color stability, surface roughness and flexural strength of acrylic resin after immersion in alkaline peroxide and alkaline hypochlorite solutions, simulating a five-year-period of use. Sixty disc-shaped (16 x 4 mm) and 60 rectangular specimens (65 x 10 x 3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and assigned to 3 groups (n = 20) of immersion (20 min): C1: distilled water; AP: warm water and one alkaline peroxide tablet; SH: 0.5% NaOCl solution. Color data (∆E) were determined by a colorimeter and also quantified according to the National Bureau of Standards units. A rugosimeter was used to measure roughness (μm) and the flexural strength (MPa) was measured using a universal testing machine. Data were evaluated by Kruskal-Wallis followed by Dunn tests (color stability and surface roughness) and by one-way ANOVA and Bonferroni test (flexural strength). For all tests was considered α = 0.05. AP {0.79 (0.66;1.42)} caused color alteration significantly higher than C1 {0.45 (0.37;0.57)} and SH {0.34 (0.25;0.42)}. The mean ∆Ε values quantified by NBS were classified as "trace" for C1 (0.43) and SH (0.31) and "slight" for AP (0.96). SH {-0.015 (-0.023;0.003)} caused significantly higher ΔRa than the C1 {0.000 (-0.004;0.010)} and AP {0.000 (-0.009;0.008)} groups. There was no statistically significant difference among the solutions for flexural strength (C1: 84.62 ± 16.00, AP: 85.63 ± 12.99, SH: 84.22 ± 14.72). It was concluded that immersion in alkaline peroxide and NaOCl solutions simulating a five-year of 20 min daily soaking did not cause clinically significant adverse effects on the heat-polymerized acrylic resin.

The influence of polymerization type and reinforcement method on flexural strength of acrylic resin.

The aim of this study was to evaluate the flexural strength of acrylic resin bars by varying the types of resin polymerization and reinforcement methods. Fourteen groups (N = 10) were created by the interaction of factors in study: type of resin (self-cured (SC) or heat-cured (HC)) and reinforcement method (industrialized glass fiber (Ind), unidirectional glass fiber (Uni), short glass fiber (Short), unidirectional and short glass fiber (Uni-Short), thermoplastic resin fiber (Tpl), and steel wire (SW)). Reinforced bars (25 × 2 × 2 mm) were tested in flexural strength (0.5 mm/min) and examined by scanning electron microscopy (SEM). Data (MPa) were submitted to factorial analysis, ANOVA, and Tukey and T-student tests (a = 5%) showing significant interaction (P = 0.008), for SC: Uni (241.71 ± 67.77)a, Uni-Short (221.05 ± 71.97)a, Ind (215.21 ± 46.59)ab, SW (190.51 ± 31.49)abc, Short (156.31 ± 28.76)bcd, Tpl (132.51 ± 20.21)cd, Control SC (101.47 ± 19.79)d and for HC: Ind (268.93 ± 105.65)a, Uni (215.14 ± 67.60)ab, Short (198.44 ± 95.27)abc, Uni-Short (189.56 ± 92.27)abc, Tpl (161.32 ± 62.51)cd, SW (106.69 ± 28.70)cd, and Control HC (93.39 ± 39.61)d. SEM analysis showed better fiber-resin interaction for HC. Nonimpregnated fibers, irrespective of their length, tend to improve fracture strength of acrylics.

Color Stability, Surface Roughness and Flexural Strength of an Acrylic Resin Submitted to Simulated Overnight Immersion in Denture Cleansers

This study evaluated color stability, surface roughness and flexural strength of acrylic resin specimens after immersion in alkaline peroxide and alkaline hypochlorite, simulating a period of one and a half year of use of overnight immersion. Sixty disc-shaped (16x4 mm) and 80 rectangular specimens (65x10x3.3 mm) were prepared from heat-polymerized acrylic resin (Lucitone 550) and distributed into 4 groups (n=20): C1: without immersion, C2: 8 h immersion in distilled water; AP: 8 h immersion in alkaline peroxide effervescent tablet; SH: 8 h immersion in 0.5% NaOCl solution. Properties were evaluated at baseline and after the immersion. Color data were also calculated according the National Bureau of Standards (NBS). Results were analyzed statistically by ANOVA and Tukey's HSD test (α=0.05). AP (2.34 ± 0.41) caused color alteration significantly higher than C2 (0.39 ± 0.30) and SH (1.73 ± 0.52). The mean ΔE values were classified as indicial for C2 (0.36 ± 0.29) and noticeable for AP (2.12 ± 0.39) and SH (1.59 ± 0.48). SH (0.0195 ± 0.0150) caused significantly higher ΔRa (p=0.000) than the C2 (0.0005 ± 0.0115) and PA (0.0005 ± 0.0157) groups. There was no statistically significant difference (p=0.063) among the solutions for flexural strength (C1: 105.43 ± 14.93, C2: 100.30 ± 12.43, PA: 97.61 ± 11.09, SH: 95.23 ± 10.18). In conclusion, overnight immersion in denture cleansing solutions simulating a year and a half of use did not alter the flexural strength of acrylic resin but caused noticeable color alterations, higher for alkaline peroxide. The 0.5% NaOCl solution caused increase in surface roughness.

Effect of Curing Time on the Flexural Strength of Heat Cured Acrylic Resin

Objectives: The aim of this study was to find out the proper curing time and flexural strength of heat cured acrylic resin cured in boiling water at 100°c with time difference and to compare the maximum flexural strength in optimum time. Methods: In this study, 60 heat cured acrylic resin samples were processed with compression moulding technique at 100°c among which each of 20 samples were cured for 20, 40 and 60 minutes separately. Flexural strength of samples was determined by using 3 point bending test by universal testing machine. Data was analyzed using ANOVA test and unpaired t-test. Results: The ANOVA result showed that there was no significant differences among the groups with respect to the mean flexural strength (P&gt;0.05) and unpaired t-test also showed no significant differences among the groups. The mean flexural strength of acrylic resin cured at 100°c with compression moulding technique at 100°c at 20 minutes was 80.09±14.58 MPa, at 40 minutes was 79.71±13.1 MPa and at 60 minutes was 80.76±15.75 MPa. Conclusion: The flexural strength of heat cured acrylic denture base resin cured at 100°c for different period of time (at 20, 40 &amp; 60 minutes) have given no significant differences. DOI: http://dx.doi.org/10.3329/cdcj.v9i2.12316 City Dental College J. Volume-9, Number-2, July-2012