EGYPTIAN DENTAL JOURNAL

Transcription

1 EGYPTIAN DENTAL JOURNAL Vol. 59, 3939:3944, October, 2013 I.S.S.N EFFECT OF ADDING NANOPARTICLES OF SILVER ON COLOR STABILITY OF ACRYLIC RESIN DENTURE BASE MATERIAL Hamada Z Mahrous * and Mohamed I. Ebrahim ** ABSTRACT Objective: The aim of this study was to investigate the effect of adding different concentrations nanoparticles of silver on color stability of acrylic resin denture base material. Materials and Methods: A total of 20 discs were used in this study, divided into 4 groups (5 each) relative to percentage of nanoparticles of silver (NAg) adding (1%, 2%and 5%) and one group without additives (control group). A double beam ultra-violet visible spectrophotometer was used to obtain diffuse reflectance data at every 5nm between nm. An integrating sphere attachment was used for the measurement. The results were recorded using a computer color matching system (CCM) and tabulated for the statistical analysis of the data. Data analysis was performed by one way ANOVA. Post Hoc test (Scheffe) was used for pair-wise comparison between the means when ANOVA test is significant. Results: Heat-cured acrylic resin with 5% nanoparticles of silver (group D) showed significantly highest mean color differences (ΔE) followed by heat-cured acrylic resin with 2% nanoparticles of silver (group C) then heat-cured acrylic resin with 1% nanoparticles of silver (group B). Heat-cured acrylic resin without additives (control group) showed significantly lowest mean color differences (ΔE). The results of color differences (ΔE) showed significant difference (P<0.05) between groups (B, C and D) and group A. Conclusion: All Groups of heat-cured acrylic resin with addition of nanoparticles of silver (NAg) showed color differences (ΔE) values higher than that control group. From a clinical point of view, the silver nanoparticles incorporation within the acrylic denture base material can be improve its color stability. (Jul 2013) INTRODUCTION Almost all complete dentures are fabricated by using an acrylic resin, low cost material that requires relatively ease manipulation and construction methods. However it s not the ideal material in every aspect. The denture base polymers should have a good esthetic and smooth glassy surface and should be capable of matching the natural appearance of the soft tissue but discoloration of acrylic resin results in esthetic problems 1. Acrylic resin is colorless and transparent at a * Lecturer of Removable Prosthodontics, Faculty of Dental Medicine Al Azhar University, Cairo (Boys). ** Lecturer of Dental Biomaterials, Faculty of Dental Medicine Al Azhar University, Cairo (Boys).

2 (3940) E.D.J. Vol. 59, No. 4 Hamada Z Mahrous and Mohamed I. Ebrahim normal temperature/ pressure values. The addition of a silver compound to acrylic resin as a measure against odor and bacterial proliferation in the oral cavity has been studied, but undesirable color changes have tended to occur 2. Color and translucency should be maintained during processing and the resin should not be stained or change color during clinical use. Color stability is an important factor for many dentures dental materials. These dentures should be accurate and fit inside patient mouth which is an important rule 3. The color stability of prosthesis may be the most important factor for determining the patient acceptance 4. The correct imitation of natural colors is a fundamental component to reach satisfactory aesthetic results. The color evaluation of an object can be made based on subjective or objective methods. Subjective methods are based on visual observation, whereas in objective tests color parameters (L*, a*, b*) are quantified. L* represents brightness on vertical axis from black to white. On horizontal planes, a* represents red on the positive side and green on the negative side, whereas b* represents yellow on the positive side and blue on the negative one. Color differences (ΔE) between two objects are evaluated using one object as control while the other is compared to it 5. In acrylic resins, the staining pigment is added to the powder, a fact that may lead to the idea that different powder/liquid ratios may influence the final color. As resins are translucent, thickness may also have influence on color depending of the color of the underlying material and on the powder/ liquid ratio 6. The addition of a silver compound to acrylic resin as a measure against odor and bacterial proliferation in the oral cavity has been studied, but undesirable color changes have tended to occur. Silver methacrylate is marketed overseas and is used as an antibacterial film, etc., but it has not been studied as a dental material because of its high cost, and basic data for clinical application such as those concerning hardness and color change as well as antibacterial activity has not been collected. If this material can be synthesized at a low cost, various experiments including those in the dental field will become possible 2. In order to use nanosilver for different applications, various chemical and physical methods are used to synthesize the nanosilver 7. Chemical methods usually require a silver salt precursor, a reducing agent (formaldehyde, glucose or hydrogen peroxide.), a solvent, a stabilizer and a capping agent. Silver nitrate is a commonly used precursor to produce silver nanoparticles 8. Alternatively, the wet/dry electroplating method, electric spark bombardment and other mechanical techniques (polishing and grinding) are used as physical methods to produce nanoparticles 9. Nanosized silver can be made with different shapes such as particles, wires, and rods. Nanoparticles of silver (NAg) have already been used in everyday consumer products 10. The purpose of this study was to evaluate the effect of adding different concentrations nanoparticles of silver on color stability of acrylic resin denture base material. MATERIALS AND METHODS 1- Materials: Heat-cured acrylic resin was used in this study (Acrostone (A), Anglo-Egyptian Company. Hegaz, Cairo, Egypt, Batch No.505/04). Nanoparticles of silver (NAg) added with concentration (1%, 2%and 5%) to the monomer of heat-cured acrylic resin. 2- Color Stability a) Specimens A total of 20 discs (10±1 mm in diameter and 2± mm in thickness) were used in this study (figure1).

3 EFFECT OF ADDING NANOPARTICLES OF SILVER ON COLOR STABILITY (3941) They were divided into 4 groups (5 each) relative to percentage of nanoparticles of silver (NAg) adding (1%, 2%and 5%) and one group without additives (control group) which are shown in table 1. FIG. (1) FIG. (2) TABLE (1) Heat-cured acrylic resin groups b) Testing methods Color stability evaluation A double beam ultra-violet visible spectrophotometer (U.V-Vis. UV 3101 PC, Shimadzu scanning spectrophotometer) (Figure 2) was used to obtain diffuse reflectance data at every 5nm between nm. An integrating sphere attachment was used for the measurement. The attachment was installed in the spectrophotometer according to the manufacturer s recommendation by using the supplied white calibra tion standard which used in the reference port for calibration of zero and 100% reflectance and to obtain data. A special sample holder was used to hold the sample in the attachment. Tristimulus value (X, Y and Z) was computed relative to the CIE 1931 Commission Interrated L Eclairage and relative to particular light source. The ratios of each tristimulus value of a color to their sum are called chromatically coordinate (x,y,z) i.e.: x= X/ (X+Y+Z) y=y/ (X+Y+Z) z= (1-[X+Y]) A C1E three dimensional L*, a* and b* color order system, provided a useful standardization technique for color difference assessment 11. Difference between two colors was determined from the color difference formula: Groups Group description No. of specimens Group A Heat-cured acrylic resin without additives (control group). 5 specimens Group B Heat-cured acrylic resin with1% nanoparticles of silver. 5 specimens Group C Heat-cured acrylic resin with 2% nanoparticles of silver. 5 specimens Group D Heat-cured acrylic resin with 5% nanoparticles of silver. 5 specimens Total 20 specimens

4 (3942) E.D.J. Vol. 59, No. 4 Hamada Z Mahrous and Mohamed I. Ebrahim ΔE (L*, a* and b*) = (ΔL) 2+ (Δa) 2+ (Δb) 2 Where L*, a* and b* depended on tristimulus values (X,Y,Z) of the specimens and a perfectly white object where L* corresponds to the value in the Munsell system which represents the lightness coordinate, while a* is the red-green co ordinates and b* is the yellow-blue coordinate. The color of each opposing pair is indicated by [he positive and negative values of a* and b* (+a*= redness, -a*=greenness, +b*=yellowness, -b*=blueness). The tristimulus values (X+Y+Z), the chromatically coordinate (x,y,z). The L*, a* and b*, ΔE, ΔL, Δa, and Δb were automatically calculated. The results were recorded using a computer color matching system (CCM) and tabulated for the statistical analysis of the data. Data analysis was performed by one way ANOVA. Post Hoc test (Scheffe) was used for pair-wise comparison between the means when ANOVA test is significant. RESULTS Table (2) shows the comparison between mean color differences (ΔE) of heat-cured acrylic resin groups. All Groups of heat-cured acrylic resin (B, C and D) with addition of nanoparticles of silver (NAg) showed color differences (ΔE) values higher than that control group (A). Heat-cured acrylic resin with 5% nanoparticles of silver (group D) showed significantly highest mean color differences (ΔE) followed by heatcured acrylic resin with 2% nanoparticles of silver (group C) then heat-cured acrylic resin with 1% nanoparticles of silver (group B). Heat-cured acrylic resin without additives (control group) showed significantly lowest mean color differences (ΔE). The results of color differences (ΔE) showed significant difference (P<0.05) between groups (B, Cand D) and group A. TABLE (2) Comparison between mean color differences (ΔE) of heat-cured acrylic resin groups with different interaction: Heat cured acrylic Heat cured specimens resin (control group) (A) With 1% Nanosilver. (B) With 2% Nanosilver. (C) With 5% Nanosilver. (D) p Mean value of ΔE Min. Max Mean ± SD ± ± ± ± 0.20 <0.001* Median p * <0.001* <0.001* p <0.001* p * p: p value for F test (ANOVA) for comparing between the different studied group. p1 : p value for Post Hoc test (Scheffe) for comparing between group A and each other group. p2 : p value for Post Hoc test (Scheffe) for comparing between group Band each other group. p3 : p value for Post Hoc test (Scheffe) for comparing between group C and group D. *: Statistically significant at p 0.05.

5 EFFECT OF ADDING NANOPARTICLES OF SILVER ON COLOR STABILITY (3943) materials after treatment or between time periods. Thus, ΔE is more meaningful than the individual L*, a* and b*values Previous reports related a range of values of ΔE to perceptible color difference 19,20 : Values of ΔE between 0 and 2 represent imperceptible color differences, whereas value in the range of 2 to 3 represent just perceptible color differences. Fig (3) Bar chart of mean ΔE of the tested heat-cured acrylic resin groups DISCUSSION Colorimetry is a brunch of the science of color based on the digital expression of the color perceived from an object. In assessing chromatic difference, generally two color systems are used, namely: Munsell color system and Standard Commission international de L Eclairage (CIE L*, a* and b*) color system. The American Dental Association recommends the used of CIE L*, a* and b* color differential system 12. The CIE L*, a* and b* color system uses the three parameters L*, a* and b* to define color and show the color difference quantitatively 13. ΔE value which represents overall color difference between the two measurements in CIE L*, a* and b* color space is considered to be better indicator for evaluating the color stability of dental materials 14. Although the clinical perceptibility and acceptability of color difference may vary, the inter ception of color difference in this study would be ΔE values of less than 2 units is clinically accept able, a value of ΔE in the range of 2-3 is just per ceivable and ΔE values of approximately 3.3 and above indicates an appreciable difference 15. The value of ΔE represents relative color changes that an observer might report for the The present study used nanoparticles of silver (NAg) % in monomer because NAg was shown to possess potent antibacterial properties 21. NAg was recently incorporated into dental resins 22. Their small particle size and large surface area could enable them to release more Ag ions at a low filler level, thereby reducing Ag particle concentration necessary for efficacy 23. The Ag ions in the resin agglomerated to form nanoparticles that became part of the resin 24. CONCLUSION Based on the results obtained in this study, it can be concluded that: - All Groups of heat-cured acrylic resin with addition of nanoparticles of silver (NAg) showed color differences (ΔE) values higher than that control group. - From a clinical point of view, the silver nanoparticles incorporation within the acrylic denture base material can be improve its color stability. - The 5% nanoparticles of silver have significantly highest mean color differences followed by 2% nanoparticles of silver then with 1% nanoparticles of silver contained heat-cured acrylic resin. - Heat-cured acrylic resin without additives (control group) showed significantly lowest mean color differences (ΔE).

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