Color Stability Of Acrylic Resins Research Articles

Antimicrobial effect of phytosphingosine in acrylic resin.

This study evaluated color stability (CS), anti-adherence effect (AAE), and cell viability of microorganisms on acrylic resin (AR) surface, treated associated or not with sodium percarbonate (SP). AR specimens were prepared, and color analysis was performed before and after the treatments and the CS was calculated. For analysis of AAE, the samples were sterilized by radiation in a microwave oven. Then samples were randomly distributed: phosphate-buffered saline (PBS - control), 0.5% sodium hypochlorite (SH), phytosphingosine (PHS), and phytosphingosine + SP (PHS+Na2CO3). The specimens remained in contact with solutions for 30 minutes and were later contaminated by Candida albicans. Aliquots were seeded in Petri dishes with Sabouraud Dextrose agar and incubated at 37°C for 24 hours. After the incubation, the number of colonies was counted. The cell viability of adhered microorganisms on the AR was evaluated and 20 fields were observed under an epifluorescence microscope, and the percentage of adhered viable cells was calculated. Data were compared (One-way ANOVA, Tukey, p<.05). As for CS, PHS+ Na2CO3 (0.4±0.1) resulted in less change than PBS (0.9±0.2), similar to the other groups (SH [1.0±0.3)]; PHS [0.9±0.2)]). There was no difference for all tested solutions regarding the ability to avoid microorganism adherence (p>0.05), but PHS (11.2±4.1) resulted in a smaller area of adhered viable cells, statistically different from SH (18.2±7.6) and PBS (26.4±10.8). It was concluded that PHS resulted in lower adhered viable cells and when associated with Na2CO3, also shows a lower effect on the CS of AR.

TiO2-Nanofillers Effects on Some Properties of Highly- Impact Resin Using Different Processing Techniques.

Background:The criteria of conventional curing of polymethyl methacrylate do not match the standard properties of the denture base materials.Objectives:This research was conducted to investigate the addition of TiO2 nano practical on impact strength, thermal conductivity and color stability of acrylic resin cured by microwave in comparison to the conventional cured of heat-polymerized acrylic resin.Materials and Methods:120 specimens made of high impact acrylic resin were divided into two main groups according to the type of curing (water bath, microwave), then each group was subdivided into two groups according to the addition of 3% TiO2 nano-fillers and control group (without the addition of TiO2 0%). Each group was subdivided according to the type of test into 3 groups with 10 specimens for each group. Data were statistically analyzed using Student t-test to detect the significant differences between tested and control groups at significance level (P<0.05).Results:According to curing type methods, the results showed that there was a significant decrease in impact strength of microwaved cured resin, but there was no significant difference in the thermal conductivity and color stability of resin. In addition, by using nanofiller, there was a significant increase in the impact strength and color stability with the addition of 3% TiO2 nanofillers, but no significant difference was found in the thermal conductivity of the acrylic resin.Conclusion:The microwave curing of acrylic resin had no change in the color stability and thermal conductivity in comparison to the water bath, but the impact strength was decreased. The addition of 3% TiO2 improved the impact and the color stability, but the thermal conductivity did not change.

Color stability of heat polymerized polymethyl methacrylate resin denture base after addition of high molecular nano chitosan

Background: The addition of other ingredients to maintain color stability of heat polymerized polymethylmethacrylate is being developed. One of them is by adding high molecular nano chitosan. Purpose: This study aimed to determine the color stability of heat polymerized polymethyl methacrylate denture base resin after an addition of high molecular nano chitosan. Method: 30 sample pieces of acrylic plate (40x10x2 mm) were divied into 6 groups: control group and groups with the addition of chitosan nano gel percentages of 0.25, 0.50, 0.75, 1.0 and 1.50%. 2 ml chitosan nano gel was added into the mixture of acrylic resin with 23 g : 10 ml (P : L). After the mixture was inserted into a mold and then pressed and cured at 74oC for 120 minutes and then 100o C for 60 minutes. Acrylic plates were then released from the mold and finished. Color stability of acrylic resin were measured using UV-Vis Spectrophotometer and analyzed with a one way Anova. Result: The results showed significant differences in color stability after the addition of high molecular nano chitosan. The best color stability found in 1.0% the addition of chitosan nano gel group, the value was 0.07589 cm-1. Conclusion: The chitosan nano gel can be used to maintain color stability of heat polymerized polymethyl methacrylate denture base resin.

Effect of denture cleansers on color stability and surface roughness of denture base acrylic resin.

Color stability of acrylic resin is one of the most important feature for denture wearers. Many patients use detergent solutions to remove denture stains. The purpose of this study was to evaluate color stability and surface roughness of two common acrylic resins in different detergent and tea solutions. 112 acrylic resin blocks of Meliodent and Acropars (each 56 blocks) were divided into seven groups of different treatment: 1% sodium hypochlorite for 10 min a day for 1 month (H10m), 1% sodium hypochlorite for 8 hours a day for 1 week (H&h), Correga tabs solution for 8 hours a day for 1 month (C&H), tea bag for 2 hours a day for 1 month (T2 h), tea bag for 2 hours a day then 10 min in 1% sodium hypochlorite for 1 month (T-H), tea bag for 2 hours then 8 hours in the Correga tab solution a day for 1 month (T-C), and finally distilled water for 1 month as a control group (con). After specimen's treatment, color (CIE Lab) and surface roughness (Ra, µm) of samples were measured. The results were analyzed by analysis of variance (ANOVA), followed by Tukey's HSD and Dunnett T3. Group T2h exhibited a significant (P<;0.05) color change and control specimens exhibited the lowest color change. Sodium hypochlorite caused a significant (P<0.05) color change in the Acropars group in comparison with the Meliodent group. In the Correga tab solution the difference was not significant (P=0.155). There was a significant (P<0.05) color change in the T-H treatment. The Acropars and Meliodent acrylic resin did not a show significant difference in surface roughness after different treatments. Sodium hypochlorite 1% for 10 minutes a day in a month is the recommended hygiene protocol. The color stability of acryl is brand-type dependent but surface roughness is not.

Effect of intrinsic nanoparticle pigmentation on the color stability of denture base acrylic resins

Intrinsic pigmentation is widely used to improve the esthetic features of denture base acrylic resins. However, acrylic resin may discolor over time. The purpose of this study was to investigate the effect of intrinsic nanoparticle pigmentation on the color stability of acrylic resins. The acrylic resins, Onda Cryl, QC 20, Classico, and Lucitone, were evaluated. Twenty-one disk-shaped specimens (3 × 30 mm) were fabricated from each acrylic resin. Seven were colored with 3% Poli-Cor intrinsic pigment used to color denture base, 7 were colored with 7% pigment, and 7 were not pigmented. In addition, 7 specimens were fabricated containing only pigment. The specimens were thermally cycled 2000 times between 5°C and 55°C with a 30-second dwell time at each temperature. The specimen colors were measured with a spectrophotometer and evaluated with the CIE L*a*b* system before (B) and after thermal cycling (T). The pigment morphology was analyzed by using a scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDS) techniques. The results were analyzed with 2-way nested ANOVA and Tukey HSD tests (α=.05). Classico acrylic resin with and without pigment underwent the least color change, followed in order by Lucitone, Onda Cryl, and QC-20. The presence of pigments reduced the color change of the acrylic resins significantly (P<.05) for the specimens containing 7% pigment (0.32 ±0.18 ΔE). Titanium was the sole metallic component present in the pigment, probably in the oxide form (TiO2). Nanoparticle pigments enhanced the color stability of denture base acrylic resins.

Chromatic stability of acrylic resins of artificial eyes submitted to accelerated aging and polishing

Esthetics and durability of materials used to fabricate artificial eyes has been an important eissue since artificial eyes are essential to restore esthetics and function, protect the remaining tissues and help with patients' psychological therapy. However, these materials are submitted to degrading effects of environmental agents on the physical properties of the acrylic resin.ObjectiveThis study assessed the color stability of acrylic resins used to fabricate sclera in three basic shades (N1, N2 and N3) when subjected to accelerated aging, mechanical and chemical polishing. Material and methodsSpecimens of each resin were fabricated and submitted to mechanical and chemical polishing. Chromatic analysis was performed before and after accelerated aging through ultraviolet reflection spectrophotometry. ResultsAll specimens revealed color alteration following polishing and accelerated aging. The resins presented statistically significant chromatic alteration (p<0.01) between the periods of 252 and 1008 h. ConclusionsBoth polishing methods presented no significant difference between the values of color derivatives of resins.

A Method of Predicting Color Stability of Autopolymerizing Acrylic Resins Using Electron Spin Resonance.

Synopsis. Long periods can be required to determine the color stability of acrylic resins. The concentration of propagating radicals with unpigmented experimental resins (UER) and initiator solution (IS) of two initiator systems (binary and ternary) and five products were measured using electron spin resonance (ESR). The radical concentration was estimated from the area under the integrated ESR spectrum. The discoloration was measured using a color computer. Higher content of benzoylperoxide led to higher radical concentrations. The radical concentration for the ternary system increased slightly with time, but were lower than those of the binary system. Significant positive correlations were found between the radical concentration and delta E*ab for UER (r = 0.900, p < 0.01), IS (r = 0.953, p < 0.001) and the products (r = 0.808, p < 0.05). It was suggested that the color stability of these resins was predictable by measuring the radical concentration using ESR.