Heat-cured Denture Base Resin Research Articles

Comparative Evaluation of Antifungal Property of Chitosan and Two Different Natural Oils on Heat-cured Denture Base Resins Against Candida albicans: An in vitro Study

Comparative Evaluation of Antifungal Property of Chitosan and Two Different Natural Oils on Heat-cured Denture Base Resins Against Candida albicans: An in vitro Study

Assessment of Adaptability and Linear Dimensional Changes of Two Heat Cure Denture Base Resin with Different Cooling Techniques: An In Vitro Study.

The current study was designed to assess the linear dimensional changes and adaptability of two heat-cured denture base resins using various cooling methods. To prepare a total of 90 acrylic resin samples (45 acrylic resin samples for each material), four rectangular stainless-steel plates measuring 25 × 25 × 10 mm were fabricated. For both groups, the material was put into the mold at the dough stage. Group I - SR Triplex Hot Heat Cure acrylic; group II - DPI Heat Cure acrylic. Both groups used the same curing procedure. One of the following three techniques was used to cool the material (15 samples from each material) once the curing cycle was finished: (A) water bath, (b) quenching, and (C) air. A traveling microscope was used to measure the distance between the markings on the acrylic samples. The data was recorded and statistically analyzed. In SR Triplex Hot heat cure acrylic material, the maximum linear dimensional changes were found in the quenching technique (0.242 ± 0.05), followed by the air technique (0.168 ± 0.11) and the least was found in the water bath technique (0.146 ± 0.01). In DPI Heat Cure acrylic material, the maximum linear dimensional changes were found in the quenching technique (0.284 ± 0.09), followed by the air technique (0.172 ± 0.18) and the least was found in the water bath technique (0.158 ± 0.10). There was a statistically significant difference found between these three cooling techniques. On comparison of adaptability, the water bath technique, the marginal gap SR Triplex Hot was 0.012 ± 0.02 and DPI Heat Cure was 0.013 ± 0.02. In the quenching technique, the marginal gap SR Triplex Hot was 0.019 ± 0.04 and DPI Heat Cure was 0.016 ± 0.04. In the air technique, the marginal gap SR Triplex Hot was 0.017 ± 0.01 and DPI Heat Cure was 0.019 ± 0.01. The present study concluded that among the different cooling methods, the water bath technique had the least linear dimensional change, followed by the air and quenching techniques. When comparing the materials, DPI Heat Cure acrylic resin showed a greater linear dimensional change than SR Triplex Hot heat cure acrylic resin. During polymerization, heat-cured acrylic resins experience dimensional changes. Shrinkage and expansion are dimensional changes that occur in heat-cured acrylic resins and have an impact on the occlusal relationship and denture fit. However, the denture base's material qualities and the different temperature variations it experiences during production may have an impact on this. How to cite this article: Kannaiyan K, Rathod A, Bhushan P, et al. Assessment of Adaptability and Linear Dimensional Changes of Two Heat Cure Denture Base Resin with Different Cooling Techniques: An In Vitro Study. J Contemp Dent Pract 2024;25(3):241-244.

Flexural Strength of Heat Cure Denture Base Resin incorporated with Curcumin: An In-Vitro Study

Introduction: Acrylic resin when used for fabrication of denture is susceptible for microbial colonization. Many antimicrobial agents have proven effective against the microbial colonization when they were incorporated into the acrylic resin but adding anything into the acrylic resin can alter its mechanical properties resulting into unacceptable intraoral use. This study was done to evaluate ifadding an antimicrobial agent, Curcumin, alters the flexural strength of acrylic agent. Methods: 172 acrylic strips were fabricated. They were divided equally into 4 groups depending upon concentration of curcumin as Control, T1: 1% curcumin, T2: 3% curcumin and T4: 5% curcumin. Flexural strength was tested using 3-point bend test using Universal Testing Machine. Results: There was no significant difference in values of mean flexural strength for control, 1% and 3% curcumin groups. There was significant difference in the mean value between control and 5% curcumin group. Conclusion: 1% and 3% curcumin can be incorporated into acrylic resin without significantly altering its mechanical properties.

A Comparison of the Wetting Ability of Three Artificial Saliva Substitutes on Heat-Cured Denture Base Resin - An In vitro Study.

Salivary substitutes are gaining popularity these days because of the increase in patients with dry mouth. These substitutes must satisfy certain criteria to fulfill the patient's needs. One of these is wettability. One hundred fifty rectangular specimens of heat-cured denture base acrylic resin were prepared. A drop of test liquids (human saliva, distilled water, aqwet, saleva, and wet mouth) was placed over the test specimen and right and left contact angles were measured using optical contact angle machine. All test liquids performed better than distilled water. Human saliva has the least contact angle followed by aqwet. Carboxymethyl cellulose base aqwet saliva substitute was found to be best having similar contact angle values to human saliva.

Effect of Monomer Application for Different Time Periods on Bond Strength between Heat Cured Denture Base Resin and Acrylic Resin Teeth

Aim: To find out the effect of monomer application for different time periods on tensile bond strength of heat cured denture base resin and acrylic resin teeth. Methodology: Ninety specimens were fabricated as per ADA standards No 15 and were divided into 3 groups through purposive sampling technique. In Group 1 monomer was applied on acrylic resin teeth just before heat cured denture base material was packed. In Group 2 monomer was applied for 10 seconds and in Group 3 for 60 seconds. Universal testing machine applied tensile load between denture base and acrylic teeth. Visual observation was done to detect types of failure. Result: Group 2 showed the highest value of tensile bond strength followed by Group 1 and 2 however there was no statistically significant (p>0.05) difference between the groups. Practical implication: Monomer application enhances bond strength between denture base and acrylic teeth but time period of its application which could provide maximum benefit is not very clear. Therefore this study is carried out so that the most effective time period of its application can be figured out. Conclusion: Bond strength was not affected by monomer application for different time periods. Keywords: Monomer, Time period, Denture base resin, Acrylic teeth

Comparative Evaluation of Flexural Strength of Heat Cured Denture Base Resin Modified with Silver Nanoparticles and Silanized Zirconium Oxide Nanoparticles Using Two Curing Cycles – An in Vitro Study

Comparative Evaluation of Flexural Strength of Heat Cured Denture Base Resin Modified with Silver Nanoparticles and Silanized Zirconium Oxide Nanoparticles Using Two Curing Cycles – An in Vitro Study

Evaluation of the Impact of Different Disinfectants on Color Stability of Denture Base Materials: A Comparative Study

Aim of the current research was to assess the effect of different disinfectant solutions on the color steadiness of denture base materials. Ninety samples were made employing the Meliodent and ProBase Hot heat cure denture base resin materials. Metallic disks measuring 3 mm thick as well as 20 mm in diameter were utilized to make the samples. Forty-five samples of every denture base material were immersed in three chemical disinfectants: 2% alkaline glutaraldehyde, 0.5% chlorhexidine gluconate, 0.5% sodium hypochlorite solution as well as distilled water that served as a control. Color scoring was performed at baseline and following first, 14th as well as 21 days. Color was calculated as per CIE L*a*b* color scale as related to standard source C alongside a white background on a reflection spectrophotometer. Subsequent to the immersion of Meliodent heat-cured denture base resin materials within distilled water, the baseline color steadiness score was 6.16 ± 0.12, 6.12 ± 0.08 on the first day, 5.98 ± 0.06 on day 14 and 5.74 ± 0.14 on day 21. Within 2% alkaline glutaraldehyde the baseline color constancy mean value was 6.12 ± 0.28, 6.08 ± 0.04 on the first day, 5.04 ± 0.11 on day 14 and 4.22 ± 0.14 on day 21. Within 0.5% chlorhexidine gluconate the baseline color constancy mean value was 6.14 ± 0.09, 6.02 ± 0.12 on the first day, 5.38 ± 0.19 at 14th day and 4.84 ± 0.10 on day 21. In 0.5% sodium hypochlorite solution the baseline color steadiness mean value was 6.16 ± 0.18, 6.10 ± 0.06 on the first day, 4.98 ± 0.26 on 14th day and 3.14 ± 0.14 on day 21. ProBase Hot heat cure denture base resin materials after immersion in Distilled water delineated the baseline color constancy mean value was 6.48 ± 0.02, 6.34 ± 0.09 on the first day, 6.08 ± 0.14 on 14th day and 5.88 ± 0.07 on day 21. Within 2% alkaline glutaraldehyde the baseline color constancy mean value was 6.42 ± 0.16, 6.18 ± 0.11 on the first day, 5.12 ± 0.18 at 14th day and 4.24 ± 0.24 on day 21. Within 0.5% Chlorhexidine gluconate the baseline color steadiness mean value was 6.48 ± 0.10, 6.26 ± 0.08 on the first day, 5.48 ± 0.11 on 14th day and 4.88 ± 0.06 on day 21. In 0.5% sodium hypochlorite solution the baseline color steadiness mean value was 6.44 ± 0.12, 6.14 ± 0.08 on the first day, 4.98 ± 0.16 on 14th day, and 3.34 ± 0.06 on day 21. There was a statistically noteworthy difference amid the dissimilar time points in each of the three disinfectants. In the confines of the inherent limitations of this research, it can be inferred that the color steadiness of either denture base resins was enhanced following immersion in 0.5% chlorhexidine gluconate in pursuit by 2% alkaline glutaraldehyde as well as 0.5% sodium hypochlorite solution. Distilled water exerted the smallest amount of influence on the color change of the samples of denture base resins. Techniques that help infection prevention influence denture disinfection. Currently, there is a dearth of commercially marketed agents that are specifically intended to disinfect dentures. Color constancy of the denture materials is an important parameter to be given due consideration while selecting a disinfectant. This would be a pivotal characteristic for practitioners to consider as they choose disinfectant solutions to disinfect dentures.

Evaluation of the In-Vitro Cytotoxicity of Heat Cure Denture Base Resin Modified with Recycled PMMA-Based Denture Base Resin.

Aim:The aim of the present study was to evaluate the in-vitro cytotoxicity of heat-cure denture base resin (PMMA) modified with recycled denture base resin at 10%, 20%, 30%, 40%, and 50% (w/w) concentration.Materials and Methods:A total of 30 disk-shaped specimens were prepared and divided into six groups (n = 5). The Control group (R0) consisted of unmodified processed denture base resin, the experimental group consisted of denture base resin processed with substitution of 10% 20%, 30%, 40%, and 50% (w/w) of recycled denture base resin (R10, R20, R30, R40, and R50). Eluates were prepared using five sterile specimens of each group. The mouse fibroblast cell line (L929) was seeded in a 96-well cell plate system at a concentration of 1 × 104 cells/well in the DMEM medium with 1× antibiotic and antimycotic solution and 10% fetal bovine serum at 37°C with 5% CO2 and incubated in a CO2 incubator for 48 h. MTT assay was applied and the absorbance was measured at 570 nm using a microplate reader to assess the in-vitro cytotoxicity. One-way analysis of variance (ANOVA) along with post hoc Scheffe test was used to statistically compare the mean optical density (OD) values and cell survival/viability % amongst the groups.Results:No statistically significant difference was observed in the mean and standard deviation of the optical density and cell viability % of the test groups that were compared.Conclusion:Modification of denture base resin using recycled PMMA does not have a cytotoxic effect on the mouse fibroblast cell line L929.

A comparison study on shear bond strength of 3D printed resin and conventional heat-cured denture base resin to denture relining materials

A comparison study on shear bond strength of 3D printed resin and conventional heat-cured denture base resin to denture relining materials

Comparative Evaluation of Compressive Bond Strength between Acrylic Denture Base and Teeth with Various Combinations of Mechanical and Chemical Treatments

Debonding and detachment of artificial teeth from the denture base is frequently encountered in prosthodontic practice. This study aims to assess the effect of modifications in the ridge-lap surface of denture teeth with various combinations of mechanical and chemical surface treatments with hydrofluoric acid on bond strength with the acrylic denture base resin and to identify the failure modes (adhesive, cohesive, or mixed). Seventy acrylic resin teeth samples were randomly divided into seven groups (n = 10): a control group (unmodified) and six treatment groups, in which various combinations of mechanical and chemical surface treatments were performed. Then, these teeth were attached to a heat-cured denture base resin block at 45° angulation. The acrylized test samples were thermocycled, and the compressive bond strength was evaluated using a universal mechanical testing machine. The results suggest that roughening with diamond burs yields the highest bond strength, whereas etching/grooving and air abrasion result in the lowest bond strength. Acid etching complemented air abrasion to improve bond strength, while negative effects were noted with acid etching in other groups. Furthermore, roughening at the neck portion of the acrylic teeth can be used by the manufacturing companies as a standard to provide higher bond strength while maintaining the esthetics of the anterior teeth.

Effect of Incorporation of Different Concentrations of Silver Nanoparticles as an Antimicrobial Agent on the Flexural and Impact Strength of Heat-Cured Denture Base Resin

Abstract Aim This article evaluates the effect of incorporating different concentrations of silver nanoparticles as an antimicrobial agent on the flexural and impact strength of heat-cured denture base resin. Material and Methods A total of 80 specimens of polymethyl methacrylate resin were fabricated (40 for flexural strength and 40 for impact strength). Specimens were fabricated using stainless steel die of dimension 65 mm × 10 mm × 2.5 mm as per the American Dental Association specification no. 12, and 50 mm × 6 mm × 4 mm as per ISO 1567:1999 for flexural strength and impact strength, respectively, and were divided into four groups (A, B, C, and D) based on the concentrations of silver nanoparticles (0%, 2.5%, 5%, and 10%). The specimens were subjected to three-point bending test and Izod impact tester for testing flexural and impact strength, respectively. Data obtained was compiled and analyzed using one-way analysis of variance and post hoc tests. Results Results showed that for both the properties, maximum strength was observed in group A (control) followed by groups B and C, and minimum was observed in group D. A statistically significant difference in flexural strength was found among all the groups, whereas no statistically significant difference in impact strength was found among any of the groups. Conclusion Within the limitations of this in vitro study, it was concluded that though incorporation of silver nanoparticles exhibited no effect on the impact strength of heat cure denture base resin, it decreased the flexural strength, so it should be used cautiously.

Release and Recharge of Fluoride Ions from Acrylic Resin Modified with Bioactive Glass.

Background: Oral hygiene is essential for maintaining residual dentition of partial denture wearers. The dental material should positively affect the oral environment. Fluoride-releasing dental materials help to inhibit microbial colonization and formation of plaque as well as to initiate the remineralization process in the early cavity area. Aim: To evaluate fluoride ion release and recharge capacity, sorption, and solubility of polymethyl methacrylate (PMMA) dental resin modified with bioactive glass addition. Materials and methods: Two bioactive glass materials (5 wt% Kavitan, 10 wt% Kavitan, and 10 wt% Fritex) and pure 10 wt% NaF were added to dental acrylic resin. After polymerization of the modified resins, the release levels of fluoride anions were measured based on color complex formation by using a spectrophotometer after 7, 14, 28, and 35 days of storage in distilled water at 37 °C. Subsequently, specimens were brushed with a fluoride-containing tooth paste on each side for 30 s, and the fluoride recharge and release potential was investigated after 1, 7, and 14 days. Sorption and solubility after 7 days of storage in distilled water was also investigated. Results: The acrylic resins with addition of 10% bioactive glass materials released fluoride ions for over 4 weeks (from 0.14 to 2.27 µg/cm2). The amount of fluoride ions released from the PMMA resin with addition of 10 wt% Fritex glass was higher than that from the resin with addition of 10 wt% Kavitan. The acrylic resin containing 10 wt% NaF released a high amount of ions over a period of 1 week (1.58 µg/cm2), but the amount of released ions decreased rapidly after 14 days of storage. For specimens containing 5 wt% Kavitan glass, the ion-releasing capacity also lasted only for 14 days. Fluoride ion rechargeable properties were observed for the PMMA resin modified with addition of 10 wt% Fritex glass. The ion release levels after recharge ranged from 0.32 to 0.48 µg/cm2. Sorption values ranged from 10.23 μm/mm3 for unmodified PMMA resin to 12.11 μm/mm3 for specimens modified with 10 wt% Kavitan glass. No significant differences were found regarding solubility levels after 7 days. Conclusions: The addition of 10 wt% Fritex and 10 wt% Kavitan bioactive glass materials to heat-cured acrylic resin may improve its material properties, with bioactive fluoride ion release ability lasting for over 4 weeks. The resin modified with 10 wt% Fritex glass could absorb fluoride ions from the toothpaste solution and then effectively release them. Addition of fluoride releasing fillers have a small effect on sorption and solubility increase of the modified PMMA resin. Clinical significance: The addition of bioactive glass may be promising in the development of the novel bioactive heat-cured denture base resin.

Assessment of Flexural Strength and Cytotoxicity of Heat Cure Denture Base Resin Modified with Titanium Dioxide Nanoparticles: An In Vitro Study

To assess the effect of titanium dioxide nanoparticles (NPs) on flexural strength and cytotoxicity of heat-cured polymethyl methacrylate (PMMA) resins. Sixty-four rectangular and 12 circular specimens were fabricated from metal dies to test flexural strength and cytotoxicity, respectively. The rectangular specimens were grouped into four (16 specimens each)-control group (Group 1), Group 2 with 3% TiO2, Group 3 with 5% TiO2, and Group 4 with 7% TiO2. They were tested for flexural strength using universal testing machine. The circular specimens were grouped into two (six specimens each)-control group and the test group which included the group which showed a highest flexural strength. They were tested for cytotoxicity using MTT assay. The analysis of variance (ANOVA) test was used to analyze the mean flexural strength of each group and Tukey's post hoc test, for pairwise group comparison (p <0.05). An independent sample t-test was used to analyze the cytotoxicity between the groups (p <0.05). The study showed that there was a significant decrease in the flexural strength from the control group (mean: 298.95), which reduced as the concentration of TiO2 increased. However, the toxicity reduced considerably from 24 hours to 7 days in both groups while the test group showed better cell viability (%) than the control group. The flexural strength of heat cure acrylic resin (modified and unmodified) was much higher than the recommended flexural strength for these resins. On adding TiO2 NPs, flexural strength decreased when compared to the control group. However, with 3% TiO2 NPs, there was no significant decrease in flexural strength as compared to conventional resins. TiO2 NP-modified heat cure acrylic resin showed less toxicity on day 1 and even lesser toxicity after 7 days indicating that it is biocompatible. TiO2 NPs incorporated at 3% concentration in denture base resin had less cytotoxicity and adequate flexural strength, to be used as a promising alternative to conventional denture base resin.

Evaluation of Effect of Aluminum Oxide on Flexural Strength and Surface Roughness of Conventional Heat-Cure Denture Base Resin.

Purpose:Acrylic denture base tends to fracture frequently during their service due to poor strength. The surface roughness of denture base is a critical property because denture base with rough surface will cause accumulation of food particles ,thereby leading plaque retention . Microbes such as candida albicans are seen inhabitating the surface.Materials and Methods:Conventional heat cure denture base reins(DPI) and heat cure denture base resin with incorporation of 15wt% aluminium oxide was studied in two groups with 20 samples each. A mold of size 65 mm × 10 mm × 3 mm (ISO Standard) was obtained by investing brass rectangles. About forty specimens were prepared. Specimens were divided into two groups (n = 20) coded A and B. Group A was the control group (n = 20) without addition of aluminum oxide. Group B was the experimental group (n = 20) with addition of 15 wt % aluminum oxide. All the specimens were stored in distilled water for 14 days. The flexural strength was measured using a three-point bending test in a universal testing machine, and the surface roughness was measured using contact-type profilometer.Results:Incorporation of 15wt% aluminum oxide leads to a significant increase in flexural strength and surface roughness of conventional heat-cure denture base resin.

An in vitro evaluation of tensile bond strength of soft liners bonded to different denture base resins.

Background:Clinically, adhesion failure is the most critical problem because of the failure of the optimal bond between denture base and the soft liner.Objectives:This study was performed to assess the tensile bond strength of two temporary soft liners to different denture base resins.Materials and Methods:Forty-eight blocks with 16 samples each of heat-cured denture base resin of three different types were fabricated from custom-made stainless steel die after de-waxing mold space. Surface roughening of each acrylic resin specimens which bonds with soft liners was done by abrading the surface and to this temporary soft liners (Perma soft denture liner and Pro soft denture liner) were bonded. The universal testing machine was used to test the tensile strength of bonded space. The results were statistically analyzed using the Statistical Software IBM SPSS Statistics for Windows, version 20.0. (Armonk, NY, USA: IBM Corp.) using the Chi-square test, Post hoc Tukey's HSD, and two way ANOVA tests.Results:It was observed that Perma soft was prevalent over Pro-soft denture liner on the basis of tensile bond strength with all three different types of denture base resins. Trevalon HI and acrylic composite exhibited better bond strength results with both Perma soft and GC Pro-soft denture liner as compared to other types of denture base resins.Conclusion:Perma soft had a better bond strength compared to Pro-soft denture liner in bonding modified denture base and conventional resins.

Adhesion of Denture Characterizing Composites to Heat-Cured, CAD/CAM and 3D Printed Denture Base Resins.

To measure the adhesion of the denture characterizing composite to heat-cured, CAD/CAM and 3D printed denture base resins. Two different denture characterizing composites with different viscosities (SR Nexco; high viscosity (SR) and Kulzer Cre-active; low viscosity (K)) and three denture base resins (Heat cure, CAD-milled and 3D printed) were investigated. 60 beams (25 × 4 × 3 mm) were fabricated for each denture base resin; 30 were bonded to SR and 30 to K to form a beam 50 × 4 × 3 mm. These were further divided (n = 10/group) to simulate the effects of 0, 6, and 12 months intraorally via thermocycling. The beams were subjected to a 4-point bend test using the chevron-notched beam method. Fracture toughness K1C (MPa ·m1/2 ) and flexural bond strength (MPa) were calculated. All specimens were analyzed for the mode of failure under the light microscope and selected specimens under scanning electron microscope. Results were statistically analyzed using ANOVA (SPSS Ver 25). The mean K1C was highest for the SR composite bonded to the heat-cured denture resin group (0.28 ± 0.11), followed by CAD/CAM (0.18 ± 0.04) and 3D printed groups (0.23 ± 0.16). Differences were not statistically significant (p = 0.268). Within each group, aging showed no statistical significance between the mean K1C and flexural bond strength (p = 0.209). The mean K1C for the K composites bonded to the three different denture bases were significantly lower compared to the SR group (p < 0.001). The mean K1C for the heat-cured denture resin group was (0.21 ± 0.1), followed by CAD/CAM (0.13 ± 0.04) and 3D printed groups (0.03 ± 0.02). Within each of the K group, aging showed a statistical significance for both the mean K1C and flexural bond strength (p = 0.002). The high viscosity SR showed significantly higher K1C and flexural bond strength to the lower viscosity K when bonded to heat-cured, CAD-milled and 3D printed denture base resins. Heat-cured denture base resins produced the highest K1C and flexural bond strength when bonded to two different types of characterizing composites.

Effect of novel cycloaliphatic comonomer on the flexural and impact strength of heat-cure denture base resin.

This study aims to evaluate the impact of adding a novel tricyclodecane dimethanol diacrylate comonomer on the flexural strength (FS) and impact strength (IS) of heat-cure denture base resin at 10% and 20% (v/v) concentrations. To test the FS and IS, a sum total of 150 bar-shaped specimens were prepared according to standard specifications. For the FS, the specimens were subjected to the three-point bend test with a span length of 50 mm. For the IS, Charpy's test was executed with a span length of 60 mm. The FS was measured in MPa, and the IS was measured in kJ/m2. There was a statistically significant difference (P < 0.001) between the control and experimental groups in that both the FS and IS were increased in the experimental groups relative to the control group.

Evaluation of some properties of recycled polymethylmethacrylate incorporated to the acrylic resin

Many attempts have been made enhancing properties of PMMA denture base material. Adding fillers to PMMA was a commonly used method to improve physical and mechanical properties. To estimate the effects of incorporating recycled polymethylmethacrylate with a different percentage with conventional heat-cured acrylic resin on some properties of heat-cured denture base resin. The recycled polymethylmethacrylate (Chaini-HK G) particles dissolved at (5%,10%,15%) was added to heat-cured polymethylmethacrylate (Spofadental, Czech Republic) polymer and mixed with a ratio of 2:1 with the polymethylmethacrylate monomer. A total number of specimens were 80, which divided into three experimental groups (5%, 10%, 15%) and control group. Each group have 20specimens. The surface hardness, water sorption, solubility and residual monomer of test groups measured as well as compared to that of control groups. Fourier transform infrared spectroscopy test (FTIR) was done for three experimental and control group. This study shows a statistically significant difference at (p&lt;0.01) in the hardness of recycled polymethylmethacrylate incorporate material (10 %,15%) groups when compared with a control group; while recycled polymethylmethacrylate incorporated (5%) group show no significant difference, group with 15% shows the highest Vickers hardness value. The mean values of water sorption test solubility test and residual monomer were decreased with the increase of incorporating a percentage of recycled polymethylmethacrylate as compared to the mean value of the control group. The incorporation of recycled polymethylmethacrylate to heat acrylic resin at different percentage improves some of its properties.

Mechanical properties of a polymethyl methacrylate block for CAD/CAM dentures.

This study compared the mechanical properties and molecular distribution of a polymethyl methacrylate (PMMA) block (Dry) with specimens that were fabricated by a conventional method and cured in a wet environment (Control). Two specimen types were fabricated with heat-curing denture base resin. Dry specimens were polymerized at high pressure and in a dry system, while Control specimens were polymerized with a heat-curing method, in accordance with the manufacturer's recommended procedures. Specimens from each group were evaluated for three-point bending, water sorption and solubility, and color change, and by gel permeation chromatography (GPC). Mean values for the flexural strengths and moduli of the Dry specimens were significantly higher than those of the Control specimens (P > 0.05). Water sorption and discoloration values of the Dry group were significantly lower than those of the Control group. Mean weight-average molecular weights of the Dry group were higher than those of the Control group. As compared with the conventional method, the present method of fabricating PMMA blocks under high pressure yields superior mechanical properties for the denture base.

Effect of silver nanoparticles incorporation on microhardness of Heat-cure denture base resins

Background: Poly (Methyl methacrylic acid) based materials are widely used for the fabrication of removable complete and partial denture prosthesis. Regular cleansing of these dentures may abrade the surface due to an inherent lack of adequate surface hardness. This roughness may adhere food to the denture surface, making it dirty and further cause stomatitis. Recently, antimicrobial activity of denture base materials incorporated with silver nanoparticles was studied, that may logically prevent microbial growth on the denture. However, the effect of these nanoparticles on the mechanical properties, which provide longevity to the prosthesis, was not substantiated. Aim: This study was designed to evaluate the effect of incorporating various concentrations of silver nanoparticles into heat-cure denture base resin materials, on their surface hardness. Materials and methods: Silver nanoparticles were incorporated at various concentrations (0.5, 1.0, 2.0 and 5.0 wt%) into three different heat-cure denture base materials. A total of 150 rectangular-shaped specimens (62 x 10 x 2.5), which comprises 50 samples from each of the three heat-cure acrylic resins were made using the compression moulding technique. Ten specimens (n=10) were allocated for each concentration such as control, 0.5wt%, 1.0wt%, 2.0wt% and 5.0wt% concentrations of silver nanoparticles. The microhardness was evaluated using the Vickers micro-hardness tester. The data were subjected to One way ANOVA and Tukey HSD tests for statistical analyses. Results: Significant differences (p=0.000) were observed between the unmodified and modified denture base materials. Conclusion: Silver nanoparticles can be considered as the favourable additives to increase the surface hardness of denture base materials.