BACKGROUND:The thickness of ceramic materials plays a crucial role in the reappearance of veneer restorations. Due to the limited space for the construction of porcelain veneer, it is difficult to cover the abutment tooth color, and the final color after restorations is achieved through the overlapping of prosthetic restorations color and abutment tooth color. In recent years, there is little evidence on the effect of veneer materials on the color. OBJECTIVE:To evaluate the color matching of porcelain veneer restorations with different ceramic materials to shade tab. METHODS:Fifteen veneer restorations were fabricated by three ceramic materials (VITA Mark II, Ivoclar E.max LTCAD and Ivoclar E.max CAD Multi, A2 shade). Veneer restorations were controled at the thickness of 0.6 mm. The color parameters of veneer restorations were measured by Olympus Crystaleye against the natural color shade resin material substrate. The color differences were calculated between veneer restoration and shade tab (A2 shade) at the cervical, central and incisal sections, respectively. The color differences (?E values) were statisticaly analyzed using a one-way analysis of variance. RESULTS AND CONCLUSION:The color value of E.max CAD LT block was the closest one among the three blocks to the standard shade guide. The results of one-way analysis of variance for the ?E values showed that, there were significant differences between the cervical sections of the veneer restorations and the shade guide (P< 0.05). At the cervical sections, the ?E values between three kinds of blocks with the standard shade guide showed significant differences (P < 0.05); the differences were also significant in L values at the central and incisal sections, a values at the incisal sections and b value at the shoulder sections (P < 0.05). Our findings indicate that, there are significant differences in the color of porcelain veneer restorations with different ceramic materials to shade tab. The difference is also found among the three sections of the veneer restorations. In the clinical application, the final prosthesis color effects should be noted, which can change by surface staining and bonding technology.

Objective:To investigate the influence of repeated stain firing on the translucency and the color of all-ceramic CAD/CAM restorations.Methods:16 all-ceramic sample disks, including 8 of A1C and 8 of A3C in the size of 15 mm?10 mm?1 mm were fabricated and fired for 5 times. Color was measured before and after stain firing using a colorimeter.Translucency was evaluated by determining the contrast ratio(CR), and changes in color were evaluated by determining color difference △E*ab,hue angle h_ ab *,chroma C_ ab and brightness L*.Results:The translucency of A3C was greater than that of A1C.More than 4 time firing increased CR value of both A1C and A3C samples(P

Objective: To investigate the translucency parameters (TP) and the color parameters of computer-aided design and computer-aided manufacturing (CAD/CAM) materials for veneer restorations in order to guide clinical practice. Methods: Eleven groups of CAD/CAM materials (A2 shade) were included in this study: IPS e.max CAD HT/LT, IPS Empress CAD HT/LT, Lava^TM Ultimate HT/LT, VITA SUPRINITY HT/T, VITA ENAMIC HT/T, VITABLOCS Mark Ⅱ, and were named as Group A, B, C, D, E, F, G, H, I, J, K. Each material was designed and milled to disk-shaped specimens (10.0 mm×8.0 mm×0.7 mm) (n=6). The specimens were polished with silicon carbide paper and the thickness of specimens were adjusted into (0.60±0.03) mm. The color parameters of specimens were individually measured with the colorimeter against black and white ceramic tiles background to obtain the TP values. The color parameters of the specimens against the composite resin background were also measured and the color differences (ΔE values) between specimens and the A2 shade tab were calculated. Results: One-way ANOVA showed that the translucency parameters of the 11 groups of materials were statistically significant (F=253.69, P<0.05). The ΔE values of CAD/CAM material groups ranged from 1.78 to 4.12 (ΔE values<5.5). Conclusions The microstructure of CAD/CAM materials and the types of material translucency influence the optical properties. The CAD/CAM materials in this experiment have achieved color matching with the A2 shade tab.

Objective To evaluate the effect of bleaching agents on the color of indirect and direct composite resins.Methods Five resin composite materials were tested in this in vitro study.The five composites were as follow:two indirect composite resins (Adoro SR,Ceramage) and three direct composite resins (Filtek Z350,Clearfil Majesty Esthetic,and Gradia Direct Anterior).For each material,twenty disk-shaped specimens were prepared and randomly divided into five groups according to the color parameters of specimens before bleaching treatment.The composite resin specimens were treated by one of five sample solutions which were at-home bleaching agents (10％ and 15％ carbarmide peroxide),in-office bleaching agents (38％ H2O2 and 35％ H2O2) and deionized water (control group).The color parameters of specimens were measured by spectrophotometer at baseline and after bleaching treatments.The color differences (ΔE values) between baseline and post-treatments were calculated.The data of color differences were evaluated statistically using two-way analysis with a significance level of 0.05.Results The color changes of the resin composites were less than 2.0 after bleaching agent treatment,therefore were not perceptible.Slight increase of L* values and decrease of C*ab values in color parameters of specimens were observed.There were statistically significant differences in ΔE values for different bleaching treatments and resin materials(P=0.001).Conclusions The bleaching agents did not affect the color of indirect and direct composite resins tested.

Objective To evaluate the influence of various shades of resin cements on the final color of an improved lithium-disilicate pressed glass ceramic veneers and analyze the agreement of resin cements and corresponding try-in pastes.Methods Forty-eight artificial maxillary central incisor teeth were sequenced according to the measured color parameters and divided at random into 8 groups(n=6).These artificial teeth were prepared following veneer preparation protocol.An improved lithium-disilicate pressed glass ceramic materials(IPS e.max Press,Ivoclar Vivadent) were selected as the veneer material.The shape and curvature of each veneer wax pattern were duplicated with the same impression to guarantee the similarity.The ceramic veneer specimens were delivered on the artificial teeth using the corresponding try-in pastes of 8 shades(Variolink Veneer,shades of LV-3,LV-2,MV,HV+2,HV+3; and 3M RelyXTM Veneer,shades of WO,TR,A3) and bonded with the resin cements.A clinical spectrophotometer was used to measure the color parameters of the ceramic veneers before the try-in,during the try-in procedure,and after cementation.△E values and C*ab values were calculated.Results The result of one-way ANOVA indicated that the color changes of ceramic veneer cementation with resin cements were statistically significantly different in the shades of resin cements(P＜0.001).The △E values of ceramic veneer after cementation ranged from 0.93 to 6.79.The color changes of ceramic veneer specimens using the shades of LV-3,HV+3,WO were 3.31,4.90 and 6.79,respectively(△E＞3.3).The △E values of the ceramic veneer specimens between the resin cements and corresponding try-in pastes were from 0.72 to 1.79(except the shade of HV + 3).Conclusions The LV-3,HV+3,WO shades were able to change the final color of a ceramic veneer.The color of resin cements and corresponding try-in pastes achieved high agreement(except the shade of HV+3).

Objective This study aimed to evaluate the influence of ceramic type and thickness on the masking abili-ty and final aesthetic effects of chairside machinable all-ceramic crowns.Methods Six kinds from three types chairside machinable ceramic materials(IPS e.max CAD HT/MT/LT,IPS Empress LT,and VITA Suprinity HT/T)in shade A2 were fabricated to slice specimens into 1.0,1.5,and 2.0 mm-thick sections(n=10).The color parameters of the speci-mens against black and white tiles and four resin substrates(A2,A4,B3,and C4 shade)were measured with a spectro-photometer.The translucency parameter(TP)was calculated using color parameters measured over standard white and black backgrounds.The color differences(ΔE)were cal-culated between there substrate shades(A4,B3,C4)and A2 shade(control group).Two-way analysis of variance(ANOVA)was performed on the TP values.The two va-riables were ceramic type and ceramic thickness.Three-way ANOVA was used to determine the effects of ceramic materials,ceramic thickness,and substrate shades on the ΔE values,followed by Tukey test for multiple comparisons(α=0.05).Results Ceramic type,ceramic thickness,and sub-strate shade significantly affected the ΔE values(P<0.001).The L* and b* values of the specimens increased with in-creasing ceramic thickness,except in substrate A2,whereas the ΔE values decreased.The color difference of all 1.0 mm-thick specimens or all specimens over the substrates C4 shade exceeded the clinically acceptable threshold(ΔE>3.3).Conclusion The masking ability of chairside machinable all-ceramic crowns is influenced by ceramic type and thick-ness,and ceramic material.The thickness of ceramic less than 2.0 mm cannot mask the gray shade abutment.

Objective: To analyze the effect of ceramic materials thickness and resin cement shades on the final color of ceramic veneers in the discolored teeth, and to investigate the color agreement of try-in pastes to the corresponding resin cements. Methods: Sixty artificial maxillary central incisor teeth (C2 shade) were used to simulate the natural discolored teeth and prepared according to veneer tooth preparation protocol. Veneers of different thickness in the body region (0.50 and 0.75 mm) were fabricated using ceramic materials (LT A2 shade, IPS e.max Press). The ceramic veneer specimens were bonded to the artificial teeth using the 6 shades of resin cements (Variolink Veneer: shades of LV-3, LV-2, HV+3; RelyX™ Veneer: shades of TR, A3, WO) (n=5). A clinical spectrophotometer was used to measure the color parameters of ceramic veneers at the cervical, body and incisal regions. Color changes of veneers before and after cementation were calculated and registered as ΔE1, and the changes between try-in paste and the corresponding resin cements were registered as ΔE2. Results: Three-way ANOVA indicated that ΔE1 and ΔE2 values were significantly affected by the ceramic thickness, resin cement shades and measuring regions (P<0.05). The ΔE1 values of six shades ranged from 0.59-8.27. The ΔE1 values were more than 2.72 when the ceramic veneers were cemented with resin cements in shades of HV+3 and WO. The ΔE2 values of six shades ranged from 0.60-2.56. The shades of HV+3, WO and A3 resin cements were more than 1.60. Conclusions Different thickness of ceramic materials, resin cement shades and measuring regions could affect the final color of ceramic veneers. The color differences of some resin cements and corresponding try-in pastes might be observed in clinical practice.