Color stability of denture liners the color change values of all liner materials were multiplied by a factor of 0.92 to obtain the NBS val- ues.22,31 A Kruskal-Wallis, nonparametric one-way analysis of variance (ANOVA) followed by a multiple comparisons test were used to analyze the k-in- dependent group of data from this investigation. In addition, for two-independent samples compari- sons Mann-Whitney U tests were used. All analy- ses were computed with the SPSS for Windows 11.00 (SPSS Inc., Chicago, IL., USA). rEsuLts The mean color measurements (L*, a*, and b*) of five liner materials recorded from the colorim- Table 1. Properties of the liner materials used in this study. Material Code Type Composition Dura-Liner II Tokuso Rebase Ufi Gel Hard DL TR UH Acrylic Based Hard Liner Material Cold curing Acrylic Based Hard Liner Material Cold curing Acrylic Based Hard Liner Material Cold curing P: poly (ethyl methacrylate) L: butylmethacrylate P: poly (ethyl methacrylate) L: α-methacryloyl oxyethyl propionate 1,6-hexanediol dimethacrylate P: poly acrylate L: HEDMA Silicone Based Soft Liner Material Heat curing Paste: gama-methacryloxy propyl trimethoxy silan, polydimethyl siloxane Molloplast B MP Permanent 020525 Ufi Gel Permanent UP Silicone Based Soft Liner Material Cold curing B:modified polydimethylsiloxane C: platinum catalyst Permanent 300.185 146 European Journal of Dentistry eter are given in Table 3. The mean and standard deviation of color change (∆E*) values and their corresponding NBS values after subjecting them to DW and aging are shown in Table 4. The discol- oration occurred after aging was significant when compared to the control samples stored in DW (ex- cept UH). The highest discoloration in all conditions was apparent with DL (∆E*Aging = 16.30) (Change to other color) and the least discoloration was found with UP (∆E*DW = 0.41) (extremely slight change) after immersion in DW. After aging treatment only DL showed color change to other color (Table 4). The liner materials were compared with ANOVA and then pairwise comparisons were done by using Usage Period Permanent Batch No. P: 081100 L: 0102300 Permanent 557561E Permanent 0240.01 Curing Procedure 12 minute at room temperature in teflon mould 8 minute at room temperature in teflon mould 7 min at room temperature in teflon mould 15 minute at 200 kg/cm2 pressure in flask, placed in cold water and then heated slowly to 100°C for 2 hours 12 minute at room temperature in teflon mould Manufacturer Dental Mfg. Co Il- linois, USA Tokuyama Corp. Tokyo, Japan Voco, Cuxhaven, Germany Detax Ettlingen, Germany Voco, Cuxhaven, Germany