Effect Of PH Value On Color And Transluence Stability Of Light-cured Composite Resins

Objective:Through soaking experiment and dyeing experiment,the color change and dyeing of light-cured composite resins in solutions with different pH values were compared,and the influence of pH value as a single factor on the color and transluence stability and stain susceptibility of light-cured composite resins was explored,which provided experimental basis for aesthetic repair of clinical light-cured composite resins and the development and improvement of materials.Methods:In this experiment,three light-cured composite resins were selected: Filtek Z250 XT,Filtek Z350 XT,Ceram.X.One Universal,and 50 cylindrical samples with diameter of 8mm and thickness of 2mm were made for each(n=150),They were immersed in solutions of different pH values(pH 3,6,8,9)under the condition of 37°C constant temperature and avoiding light,,with distilled water as the control group,and divided into 5 groups(n=10),The spectrophotometric colorimeter was used to measure the baseline values of the three resins,the chromaticity values CIE L*a*b* after 1w,2w,3w and 4w,and to calculate the value of chromatism ΔE and translucency parameter TP before and after immersion.NBS(National Bureau Standards)system was used for clinical evaluation.The three resin samples soaked for4 w were placed in Nestle coffee for 48 hours,and the above measurement methods was repeated.SPSS 27.0 statistical software was used to analyze the ΔE and ΔTP values of soaking and dyeing experiments,and the influence of pH value on the color and transluence stability of light-cured composite resins was discussed.Results:1.After soaking in different pH values,the three light-cured resins used in this experiment all showed certain color changes,mainly as ΔE increased,translucency parameter TP decreased,and increased with the extension of time.At the fourth week,the change degree of ΔE andΔTP was the largest;But the absolute values of ΔTP in all pH solutions were low(-0.15～-0.85).2.The discoloration of light-cured resins was significant in the solution with pH values of 3 and9(P < 0.01),followed by pH 6 and 8 groups,and not significantly affected by distilled water(P > 0.05).At the fourth week,Z250 XT of pH 3 group showed obvious discoloration(ΔE was 3.64±0.25,NBS > 3).3.The color and transluence stability of Filtek Z250 XT was most affected by pH value,and theΔE and ΔTP of Filtek Z350 XT and Ceram.X.One Universal were significantly different(P <0.01),and the ΔE and ΔTP of Ceram.X were the least.4.The pH value of solution has significant effects on the stain susceptibility of light-cured resins(P<0.05),the dye degree of resin in pH=3,6 groups was the largest;After soaking for four weeks,the staining results showed that Z250 XT had the largest ΔE and ΔTP,Ceram.X the smallest.Conclusions:1.The pH value of solution,action time and resin type all have effects on the color and transluence stability of the light-curing resin.The lower the pH of an acidic solution,the higher the pH of an alkaline solution,the longer the acting time,the greater the effect,which shows that ΔE increases,and the translucency parameter TP decreases;Alkaline solution has less effect than acidic solution;2.Ceram.X had the best color and transluence stability after pH solutions,and Z250 XT had the worst color stability;The higher the translucency parameter is,the easier the resin discoloration is;3.The pH value of the solution has an effect on the dye susceptibility of the light-curing resin.The stronger the acidity,the greater the dye susceptibility is and the smaller the translucency parameter is,Comparison of dyeability of three light-curing resins: Z250 XT >Z350XT > Ceram.X.