The key to achieving natural-looking dental restorations is mimicking all characteristics of the natural tooth in restorations. For this reason, tooth-colored CAD/CAM dental materials are currently the most popular materials in esthetic dentistry. There are many factors affecting the color match of dental restorations with natural teeth,123 and the optical properties of restoration materials are important factors in the color match.45678 CAD/CAM dental materials also provide a satisfying esthetics if their optical properties meet the optical properties of the natural tooth structure.

The interpretation of light reflectivity, scattering, absorption, and transmittance phenomena also affect an observer's shade perception of restorations.9 Translucency is defined as the ability of a layer of colored substance to allow an underlying background to show through.10 When light encounters translucent substances such as teeth and aesthetic restorative material, there are four phenomena associated with the interaction of the substance and the light flux: (1) specular transmission of the light flux, (2) specular light reflection at the surface, (3) diffuse light reflection at the surface, and (4) absorption and scattering of the light within the substance.1112 Translucency is thus an important factor that determines the behaviour of light in an object, which also determines the color perception of dental materials.

For an esthetic restoration, not only are natural-looking finished restorations required for a successful esthetic prognosis, but the translucency and shade of the finished restorations must remain satisfactory after a long time period. Translucency is the diffused passing of light through a material so that persons or objects on the opposite side are not clearly visible. Permitting light and diffusing properties are two important features when the translucency of materials is determined. However, extrinsic factors or drinks such as coffee and red wine have effects on the translucency of tooth-colored dental restorations.10

The effects of coffee and red wine as staining materials in the translucency of dental materials are reported in the dental literature.10 The translucency of dental restorations is also influenced by the type of dental materials.1314151617181920 Thus, the translucency of ceramics and composites is widely reported in the literature. It has been demonstrated that the translucency parameters of ceramic materials are better than composites.2122 Polymer infiltrated ceramic network (PICN) is a new generation dental material that combines the ideal properties of both composites and ceramics. Since PICN materials combine the features of ceramics and composites together, their effect on extrinsic factors may be different from those on ceramics and composites alone. There is little information about the effects of coffee and red wine in the translucency of PICN in the dental literature, and thus the aim of the present study was to investigate the effects of coffee and red wine on the translucency of PICN material, with two different translucencies and finished with different methods.

2M2 High Translucent (HT) and Translucent (T) VITA Enamic (Vita Zahnfabrik, Cuxhaven, Germany) hybrid ceramic blocks were investigated in this study. For both HT and T groups, 180 rectangular specimens with the dimensions of 12 mm × 14 mm × 2 mm were prepared using a low speed diamond saw (Isomed 1000, Buehler Ltd., Lake Bluff, IL, USA) and water cooling. All of the specimens were ultrasonically cleaned in distilled water, additionally cleaned with isopropanol to remove the grease residue, and dried with compressed air. Both HT and T-group specimens were divided into four groups, and the following different finishing procedures were applied: Control Group - no finishing and polishing performed; Technical Group - Vita Enamic Technical Kit applied; Clinical Group - Vita Enamic Clinical Kit applied; and Glaze Group - Vita Enamic glaze applied. The finishing and polishing of the specimens were performed using the methods described in a previous study.23 The translucency parameters (TP) of the specimens were evaluated using distilled water, coffee, and red wine. Thus, the subgroups (HT Control, HT Technical, HT Clinical, HT Glaze, T Control, T Technical T Clinical, and T Glaze) were further divided into three subgroups (totally 24 subgroups, n = 15) for distilled water, coffee (Nescafe Classic, Nestle) and red wine (DLC Oküzgözü 2011, Doluca, Istanbul, Turkey). Hybrid ceramic-specimens were then exposed to the solutions in an incubator at 37℃. For the preparation of the coffee solution, 15 g of coffee powder was poured into 500 mL of boiled distilled water. After 10 minutes of stirring, the solution was filtered through filter paper. For each specimen, measurements were repeated three times to determine the translucency parameters before immersion, after 24 hours, 7 days, and 28 days. The solutions were renewed daily to prevent plaque accumulation. TP were obtained with a portable spectrophotometer (VITA Easyshade Advance, VITA Zahnfabrik, Cuxhaven, Germany). Before translucency measurements were taken, the specimens were gently washed with distilled water for 5 minutes and then dried with air. The TP of each specimen was then recorded. The calibration of the device was made before each measurement. All of the measurements were taken in tooth single mode, first on a white background (L* = 93.5, a* = 0.2, b* = −1.5) and then on a black background (L* = 0, a* = 0, b* = 0) under the same lightning conditions (D65).

The black background values were subtracted from the white background and values were recorded as a “translucency parameter” (TP). TP was determined as;

These values were calculated for each of the specimens as 24 hours, 7 days, and 28 day measurements. The differences between the groups were then compared. Statistical difference was evaluated using The Kolmogrov-Smirnov normality distribution with the significance set as P < .05. Parametric tests were performed. The differences between the groups were analysed with two-way ANOVA and Tukey HSD. For TP values, repeated measurements and ANOVA analyses were made between TPfirst- TP24h- TP7days- TP28days.

Table 1 shows the TP of the HT and T blocks kept in distilled water. At the end of 28 days, there was no statistically significant difference between the T Groups. Furthermore, no statistically significant difference was found at the end of 28 days between HT Technical, HT Clinical, and HT Glaze groups, but these three groups were statistically different from the Control Group. Table 2 shows the TP of specimens exposed to red wine. There was no statistically significant difference between the HT Technical Kit, HT Clinical Kit, and HT Glaze at the end of 28 days. However, these three groups were statistically different from the HT Control Group. There was no statistically significant difference between the T Control, T Technical, and T Clinical Kit groups. Table 3 shows the TP of the specimens exposed to coffee. The HT Technical Group showed a statistically significant difference from both the HT Control and HT Glaze Groups at the 7 day measurements. For the coffee groups, there was statistically significant difference before the 28 day measurements, but at the 28 day measurement, there was no statistically significant difference among the HT and T Groups. Table 4 shows the time-dependent TP of all the HT and T Groups, finished and polished with different methods.

Red wine and coffee consumption are daily routines for most people in our era. There have been a number of dental studies aiming to determine the effects of these drinks on dental restorative materials.2425 It has been shown that the dental materials most resistant to extrinsic factors are dental ceramics, and the least resistant are composites.2526 There have also been studies in the dental literature evaluating the effects of different drinks on the translucency of ceramics and composites; however, there is limited knowledge about the effects of coffee and wine on the optical properties of hybrid ceramics, with only discoloration having been investigated.27

The translucency of the dental materials affects an observer's perception of the color of dental restorations. Most of the translucency and staining studies reported in the literature have evaluated ideally polished dental materials, but non-polished specimens and specimens finished with different methods were also evaluated in this study. In the present study, the specimens were prepared using a slow speed diamond saw and water cooling since the preparation of the specimens with CAD/CAM caused too much block materials wasted. According to the results, the period of exposure to coffee or red wine combined with different finishing methods influenced the translucency of the hybrid ceramic material evaluated in the present study. The results of the study also showed that the specimens finished with different methods and immersed in red wine all showed higher translucency parameters than the control group; however, there was only a significant difference between the 7 day HT and T Groups and the 28 day HT Group. In the red wine groups there was no statistically significant difference between the HT Control, HT Technical Kit, and HT Glaze Groups and these three groups were all statistically significant different from the control group at the 28 day measurements. It was observed that there was no statistically significant difference between the T Groups kept in red wine at 28 days. In the coffee group, the translucency parameters of the HT and T Groups finished with the Technical Kit showed the highest TP; however, TP values only reached statistically significant differences between the 7 day HT Groups. A previous study also showed that the smoothest specimen surface was obtained by finishing and polishing the hybrid ceramic with Technical Kit.22 This implies that finishing methods and the surface features of the material may be important for the translucency of the material affected by coffee and wine. The results suggest that the translucency of the HT hybrid blocks was affected more than that of the T hybrid blocks after exposure to coffee.

The color perception of a dental restoration by an observer is a complex process influenced by the illuminant and material characteristics of the restorations. The constituents of dental materials such as composite resin or ceramic within the material will absorb various wavelengths of light, allowing other wavelengths to scatter from the restoration.28 The basis of the dental material used for restorations is therefore important since the light transmission and reflection of every material are different from those of others. In the present study, both high translucent and translucent Vita Enamic blocks were evaluated because the illuminant characteristics of material translucency may also affect the translucency of materials after exposure to coffee and wine.

Knowledge of the response of hybrid ceramics with different translucencies to coffee and wine consumption may help clinicians when choosing the translucency of dental materials for restorations. In the present study, periods of 7 and 28 days were chosen due to the effects of coffee and wine on translucency. It has been reported in the dental literature that 24 hours exposure to drinks in vitro corresponds to 1 month in vivo.29 In the present study, specimens were kept in coffee and wine for 24 hours, 7 days, and 28 days, which correspond to 1 month, 7 months, and 28 months in vivo, respectively. According to the results of the present study, the translucency level of the chosen hybrid block for the restoration may not be important regarding the effects of coffee on the translucency change for a heavy coffee consumer because specimens with different translucencies and finishing methods exposed to coffee had similar TP at the end of 28 days. For a wine consumer, however, the translucency of the hybrid ceramic may be important since the results of the present study showed that HT restorations exposed to wine might demonstrate better TP then restorations made from T blocks after of 1 month. Although the values did not reach statistically significant levels, finishing the restorations with a Technical Kit may also result in better TP when the material is exposed to coffee and wine. Since the present study only evaluated the effects of coffee and wine on the translucency of hybrid blocks in vitro, it is necessary to investigate the coffee and wine exposure of the same materials clinically, or in vivo.

According to the results of the present study, the translucency of the chosen hybrid block for a restoration may not be important regarding the effects of coffee on translucency change because specimens with different translucencies and finishing methods exposed to coffee had similar translucency parameters at the end of 28 days. However, for a red wine consumer, the translucency of the hybrid ceramic may be important since the results of the present study showed that highly translucent specimens exposed to red wine demonstrated better translucency parameters than the specimens made from translucent blocks at the end of 28 days.