Don't miss a digital issue! Renew/subscribe for FREE today.
×
Compendium
May 2016
Volume 37, Issue 5
Peer-Reviewed

For discs preparation, 40 ETC0 IPS Empress® Esthetic (Ivoclar Vivadent, Brazil, www.ivoclarvivadent.com) ingots were injected to obtain a ceramic block. The blocks were cut using a low-speed saw (IsoMet® 1000, Buehler, www.buehler.com) at 250 rpm to obtain 1-mm thick discs, which were manually polished with wet 800-grit (medium) and 1200-grit (thin) silicon-carbide abrasive paper (3M, Brazil) to a final thickness of 0.6 mm, measured using a Mitutoyo Absolute 500-196-20 digital electronic caliper (Mitutoyo, Brazil, www.mitutoyo.com.br) (Figure 2).

Try-In Application

After preparation, the ceramic discs were placed on the dental substrates using the try-in materials. A pilot study was conducted prior to the present work to standardize the application of the try-in materials.

Samples were distributed in four groups according to the try-in materials used, as follows: group I, water-soluble gel (K-Y® Jelly, Johnson & Johnson, Brazil, www.jnjbrasil.com.br); groups II, III, and IV, try-in paste (Variolink® Veneer Try-in, Ivoclar Vivadent), values 0, -3 (low value), and +3 (high value), respectively (Figure 3). The thickness of the materials was standardized using a special appliance developed in the pilot study for the present work. To standardize the film thickness and ensure that the restoration was fully seated, a pressure of 1 kg was exerted over the ceramic veneer (Figure 4). Although the film thickness was not measured directly, it was assumed to be relatively homogeneous due to the uniform loading conditions.

Cementation

The distribution in groups according to the colors of the resin cement used is described in Figure 3. In groups I and II, Variolink Veneer value 0 was used. In groups III and IV, Variolink Veneer values -3 and +3 were applied, respectively.

The teeth and veneers were cleaned and dried before cementation. Tooth surfaces were etched using 37% phosphoric acid (Total Etch, Ivoclar Vivadent) for 30 seconds, cleaned for 30 seconds, and dried. The bond system (Excite® F, Ivoclar Vivadent) was applied for 10 seconds. The resin cement was cured using a Radii Plus cordless LED curing light (SDI Limited, www.sdi.com.au) for 60 seconds according to the manufacturer’s instructions. The standardization of the resin cement thickness (set tooth–resin cement–ceramic disc) was performed employing the same appliance used for the try-in materials (set tooth–try-in material–ceramic disc).

Color Measurements

Color measurements of the specimens were performed using an Easyshade® spectrophotometer (VITA Zahnfabrik, www.vita-zahnfabrik.com). Data were expressed using the CIE L*a*b* system parameters: L* indicates the lightness; a* and b* indicate the hue (a* = red-green axis, b* = blue-yellow axis).14

Three measurements were performed for each of these coordinates at three different moments, and the mean of each coordinate was considered for statistics: straight in the tooth substrate (L0*, a0*, and b0*); with the ceramic veneer in position over the substrate for the trial, using try-in pastes (L1*, a1*, and b1*); and after cementation (L2*, a2*, and b2*).

Color change (ΔE*) is commonly used to represent the difference in color between two measurements. This parameter can be calculated using the formula:
ΔE* = [(ΔL*)2 + (Δa*)2 + (Δb*)2]0.5
where: ΔL* is the variation of L*, Δa* is the variation of a*, and Δb* is the variation of b*.

For this study, three values of ΔE* were calculated:
1. ΔE1* (in the trial): using L1*, a1*, and b1*, to trial; and L0*, a0*, and b0*, to substrate
2. ΔE2* (after cementation): using L2*, a2*, and b2*, to after cementation; and L0*, a0*, and b0*, to substrate
3. ΔE3* (difference between trial and after cementation): using L2*, a2* and b2*, to after cementation; and L1*, a1*, and b1*, to trial

Statistical Analysis

The statistical analysis was performed using IBM SPSS Statistics for Windows Version 21.0 (IBM Corp., www.ibm.com) and a significance level of 0.05. Shapiro-Wilk test was used to evaluate the normality of data distribution. Kruskall-Wallis test (P < .05) was used to make comparisons of ΔE1* and ΔE2* among groups. Wilcoxon test (P < .05) was applied to compare the values of ΔE1* and ΔE2* for all the groups. To evaluate the variance of the color among groups in the trial and after cementation (ΔE3*), one-way ANOVA (P < .05) was employed.

© 2024 BroadcastMed LLC | Privacy Policy