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Aim: Polymethylmethacrylate (PMMA) resin is the most by and large used denture base material. Denture fractures are sequential to the flexure or impacting forces. Different nanoparticles such as titanium dioxide and silver nanoparticles have been used to improve its antimicrobial properties. There are limited data on their effect on flexural strength. The aim of the study was to assess the effect of silver nanoparticles and titanium dioxide nanoparticles addition on flexural strength of PMMA resins. Settings and Design: One hundred and thirty specimens divided into four groups: Control Group A, TiO2-reinforced Group B, silver nanoparticles reinforced Group C, and mixture of TiO2 and silver nanoparticle reinforced Group D. Each reinforced group further divided based on concentrations -0.5%, 1%, 2%, and 3%. Materials and Methods: Rectangular metal models of the American Dental Association (ADA)- specified dimensions: 65 mm x 10 mm x 3 mm were used to form a mold space for the fabrication of specimens. Three-point bend test was used to determine the flexural strength of the samples after immersion in distilled water for 2 weeks. Statistical Analysis: The data collected were subjected to analysis of variance followed by post hoc Tukey's test. Results: The comparison of the mean flexural strengths showed a statistically significant gradual decrease on increasing the concentrations of nanoparticles. Maximal flexural strength was seen in the control group and least with 3% Ag + TiO2 Nps. The modified specimen also showed color changes. Conclusions: In an in vitro environment, addition of TiO2 and silver decreases the flexural strength of the PMMA. It also causes visible color changes. [ABSTRACT FROM AUTHOR]

The aim is to evaluate the mechanical, physical, and microbiological properties of a denture base resin (Onda‐Cryl, microwave‐polymerized), after the incorporation of cellulose nanocrystals (CNC). Mixtures of CNC and the resin are prepared at 0% (control group), 0.25%, 0.5%, 0.75% and 1% for the flexural strength (FS) and Vickers hardness (VH) tests. Due to the VH results, surface roughness (SR), surface free energy (SFE), and the single‐ and dual‐species biofilm formation of Candida albicans and methicillin‐susceptible Staphylococcus aureus (MSSA) for metabolic activity (XTT assay), antimicrobial activity (CFU mL−1) and confocal laser microscopy tests are performed for the groups 0% and 0.75% CNC. Data are statistically analyzed (α =.05). For FS, CNC at 0.25%, 0.5% and 0.75% are similar to the control. A significant increase of VH is observed at 0.75% and 1%. The 0.75% CNC group is similar to the control for the SFE and SR tests. There is no significant difference between control group and 0.75% CNC group for adhesion and biofilm formation of different microorganisms analyzed for XTT and CFU mL−1. These results are corroborated by confocal microscopy images. The incorporation of CNC at 0.75% into a microwave‐polymerized denture base resin provides promising results regarding VH and does not influence the physical, mechanical, and microbiological properties evaluated. These results suggest that the addition of CNC in the resin does not display surface alterations capable of increasing adhesion or biofilm formation of C. albicans or S. aureus. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the influence of food‐simulating agents on the shear bond strength between direct hard liners and denture base acrylic resin. In addition, mode of failure was evaluated. Materials and Methods: One hundred fifty cylindrical columns of denture base resin were fabricated and bonded to three types of hard reline materials (Hard GC Reline, Tokuyama Rebase II Fast, TDV Cold Liner Rebase). Specimens of each reline material were divided into five groups (n = 10) to undergo 12‐day immersion in distilled water, 0.02 N citric acid aqueous solution, heptane, and 40% ethanol/water solution at 37°C. The control group was not immersed in any solution. The shear bond strength test was performed, and the failure mode was determined. Statistics were analyzed with two‐way ANOVA and chi‐square test (α = 0.05). Results: Significant interaction was found between the hard liners and food simulating agents (p < 0.001). The shear bond strength of Tokuyama in 40% ethanol and TDV in heptane decreased significantly (p = 0.001, p < 0.001 respectively); however, none of the solutions could significantly affect the shear bond strength of Hard GC Reline (p = 0.208). The mixed failure mode occurred more frequently in Hard GC Reline compared with the other liners (p < 0.001) and was predominant in specimens with higher bond strength values (p = 0.012). Conclusions: Food simulating agents did not adversely affect the shear bond strength of Hard GC Reline; however, ethanol and heptane decreased the bond strength of Tokuyama and TDV, respectively. These findings may provide support to dentists to recommend restricted consumption of some foods and beverages for patients who have to use dentures relined with certain hard liners. [ABSTRACT FROM AUTHOR]

Marked bactericidal activity of the electrolyzed acid water (EAW) and its less undesirable effects on biological tissues and the environment has been successfully utilized in dental practice. A review of literature reveals that not many studies have been performed to determine the disinfection effect of EAW on heat cured acrylic denture bases. The objective of the study is to determine the efficacy of EAW in disinfecting heat cured acrylic resin specimens as compared to the efficacy of disinfecting the specimens using 2% glutaraldehyde. Heat cured acrylic resin plates were immersed in Bacteria suspensions of Staphylococcus aureus and later disinfected using EAW which was produced using a custom made electrolyzing apparatus and 2% glutaraldehyde for different time intervals. The numbers of surviving bacteria were counted. As the control, the bacteria attached on the specimens were counted with out any disinfection treatment. The results obtained were statistically analyzed using ANOVA and post-hoc test. The disinfection potential of 2% glutaraldehyde was better than EAW when the specimens were disinfected for 1 and 3 min. Where as when the disinfection time was increased to 5 min there was no difference between EAW and 2% glutaraldehyde. However considering that the disinfecting time can be easily extended to 5 min, EAW can be effectively used for disinfecting the acrylic denture. [ABSTRACT FROM AUTHOR]

Mechanical cleaning of dentures is effective in preventing infections such as aspiration pneumonia and denture stomatitis. For denture wearers with a physical handicap and the elderly, however, mechanical cleaning can present problems. The aim of this study was to investigate the effect of coating denture base acrylic resin with titanium dioxide (TiO2) in the inhibition of oral microbial adhesion. We prepared uniformly sized acrylic resin plates (10 mm × 10 mm × 0·5 mm), which were divided into two groups (a non-coated group and a TiO2-coated group). The plates were immersed in cultured Streptococcus sanguinis or Candida albicans and incubated for 24 h. After incubation, each plate was washed to remove loosely adherent microorganisms, and then incubated for a further 24 h. Adenosine triphosphate (ATP) content of the microorganisms was evaluated using a reagent containing benzalkonium, which extracts intra-cellular ATP. In addition, to determine biofilm formation, we also observed each plate by scanning electron microscopy (SEM). We found that the ATP content of both S. sanguinis and C. albicans was reduced by the TiO2 coating ( P = 0·000). Observation by SEM confirmed that the TiO2 coating inhibited biofilm formation. The results indicate that a TiO2 coating on a denture base acrylic resin inhibits adhesion of S. sanguinis and C. albicans. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Dibenzoyl peroxide (BPO), an initiator in polymethyl methacrylate denture base resins, has been associated with allergic reactions in human patients. This study evaluated the content of BPO in acrylic denture base materials (ADBM) prior and subsequent to recommended and additional post-polymerization, and subsequent to storage in varying solutions. The goal was to determine differences in BPO content in ADBMs, to determine whether differences are seen in BPO release over time and to test different procedures for additional BPO reduction. Methods: Three heat-polymerizing, two auto-polymerizing and a microwave polymerizing “hypoallergic” ADBM were investigated. Five samples (Ø414.57mg) were polymerized according to manufacturers’ instructions from each of the six acrylic resins for each of the variables to be investigated. For each material the BPO content was measured as delivered by the manufacturer and subsequent to recommended and post-polymerization protocols. The BPO content was also evaluated after storage in distilled water (22°C, 192h), in artificial saliva (35°C, 192h), in ethanol, potassium permanganate and ammonium ferric(II) sulfate solutions (22°C, 48h). Results: High performance liquid chromatography (HPLC) and indirect iodometry were used to detect BPO concentrations. Significant differences were noted in BPO concentrations between the polymers as delivered from the manufacturer (0.13–1.20%), subsequent to polymerization (0.05–0.32%) and to the various treatment and storage procedures (H and U-tests, p <0.05). The microwave polymerizing ADBM contained the lowest initial level of BPO. No reduction of BPO content was noted after 8 days of storage in artificial saliva or water. The most notable reduction (63–95%) occurred subsequent to post-polymerization cycles. Significance: BPO was detected in all investigated ADBMs. It is unlikely, under oral conditions, that BPO is released from the investigated ADBMs. The BPO concentration can be reduced effectively by additional post-polymerization. [Copyright &y& Elsevier]

The disinfection of dental prostheses by immersion in a chemical solution should be capable of rapid inactivation of pathogenic microorganisms, without causing any adverse effect on the denture base resins. This study evaluated the effect of disinfection immersion on the transverse strength of two heat-cured resins. The denture base resins (Lucitone 550 and QC 20) were polymerized according to the manufacturers' instructions. After polymerization, the specimens were polished, and then stored in water at 37 °C for 50 ± 2 h prior immersion in one of the following solutions for 10 min: 4% chlorhexidine, 1% sodium hypochlorite and 3·78% sodium perborate. The specimens were submitted to disinfection twice, simulating when dentures come from the patient and before being returned to the patient. Ten specimens were made for each group. The transverse strength was evaluated by a 3-point bend test. The flexural strength of the two denture base acrylic resins evaluated remained unaffected after immersion in the three solutions evaluated. In general, the QC 20 resin specimens exhibited lower transverse strength than the Lucitone 550 resin specimens, regardless of immersion solutions. [ABSTRACT FROM AUTHOR]

summary This investigation evaluated the effectiveness of an infection control protocol for cleansing and disinfecting removable dental prostheses. Sixty-four dentures were rubbed with sterile cotton swab immediately after they had been taken from patients' mouths. Samples were individually placed in the culture medium and immediately incubated at 37 ± 2 °C. The dentures were scrubbed for 1 min with 4% chlorhexidine, rinsed for 1 min in sterile water and placed for 10 min in one of the following immersion solutions: 4% chlorhexidine gluconate, 1% sodium hypochlorite, Biocide (iodophors) and Amosan (alkaline peroxide). After the disinfection procedures, the dentures were immersed in sterile water for 3 min, reswabbed and the samples were incubated. All samples obtained in the initial culture were contaminated with micro-organisms. All the lower dentures immersed in Biocide showed positive growth, and the upper dentures were positive for growth in six of eight dentures. The 4% chlorhexidine gluconate, 1% sodium hypochlorite and Amosan solutions have been proved effective to reduce the growth of the micro-organisms in the 10 min immersion period. The protocol evaluated in this study seems to be a viable method to prevent cross-contamination between dental personnel and patients. [ABSTRACT FROM AUTHOR]