EFFECT OF REPEATED FIRING OF PORCELAIN FUSED TO METAL ON PORCELAIN COLOR CHANGE

Background: The color of the porcelain surface is the main criterion for achieving perfect aesthetics. A factor that influences the color is the amount of firing of the porcelain. Purpose: To determine the color change of porcelain after repeated firing four times. Method: The research specimens consisted of 6 metals coated with Classic porcelain and 6 metals coated with Noritake porcelain and were subjected to four firing stages, then each stage was fired four times. The color change value was measured using VITA Easyshade. Statistical analysis using ANOVA. Result: The Classic and Noritake groups experienced a significant increase in color change from 1^st to 2^nd burning and from 1^st to 3^rd burning with a p-value < 0.05. There is a significant difference in the color change value based on the repetition of porcelain firing with a significance value of 0.000 < 0.05. There is a significant difference in the color change value based on porcelain products with a significant value of 0.020 < 0.05. There is no significant effect between repeated firing on porcelain and porcelain products in affecting the color change value with a significance value of 0.143 > 0.05. Conclusion: Both product groups experienced an increase in color change from firing 1^st to 2^nd and from firing 1^st to 3^rd. There was no increase in color change from firing 2^nd to firing 3^rd. There are significant differences in color change values based on porcelain products and there is no significant effect between repeated firing on porcelain and porcelain products on affecting color change values.

Introduction

A beautiful smile will look perfect if the teeth look neat, clean, aligned and as one of the most important aspects in communicating(Demirel & Tunçdemir, 2023). Teeth are an important organ in the body that has a chewing function that people use every day(Nuraeni & Fitriyani, 2023). Loss or damaged teeth will have an impact to the aesthetics, and it will affect the confidence aspect and social activities. Furthermore, teeth have function to masticate the food, maintain the perfect shape of the face, and also help pronunciation aspects in speaking(Afkhami et al., 2019),(Alfarisa, 2020). Loss of teeth can also occur, this causes the chewing process to become imperfect, which has an impact on digestive health(Siagian, 2016). Fixed restorations are one of the various types of restoration that can be an alternative replacement for missing teeth(Laoh et al., 2016). Fixed restoration can replace part or all of the tooth surface that has a problem or is damaged, one important factor that can affect the aesthetics of artificial teeth is the color of the material used(Amir Rad et al., 2015),(Demirel & Tunçdemir, 2023).

One of the materials to make fixed restorations is porcelain(Hidayatin et al., 2019). Fixed restoration made from porcelain material looks more natural and has superior biomechanics(Swapna et al., 2018),(Mohamed et al., 2020). Porcelain is a material made from kaolin, feldspar, silica and various pigments(Warreth & Elkareimi, 2020). Porcelain fused to metal restorations has a higher strength and hardness compared to all other porcelain restorations and the color is easily matched to the color of natural teeth(Gunawan et al., 2017),(Rosenstiel et al., 2006). The color of porcelain restoration is greatly influenced by the manufacturing process, expertise in combining porcelain core materials and firing temperature are the main factors to create aesthetic restorations(Kumar et al., 2017).

The process of making fixed restoration involves duplicating the morphological appearance of the natural teeth and is a complex process that requires careful control of shape, surface texture, and color(Swapna et al., 2018). The making of porcelain fused to metal restoration has many procedures and it can cause some errors, one of the procedures that must be carried out is building up with porcelain powder and firing(Manappallil, 2015). The firing process during the build-up process will affect the color change because repeated firing has a negative impact on the surface structure of the porcelain and causes discoloration(Yılmaz et al., 2014),(Swapna et al., 2018), the occurrence of color change can be influenced by the thickness of the porcelain layer(Elbasuny et al., 2021). One of the successes of dental technicians in making porcelain restoration is the stability of the porcelain color because this is a guarantee for the long term. The porcelain color measurement system can be done in several ways, including visual methods or observing objects directly or by using instruments or tools to measure the color of an object. In Commission Internationale de I'Eclairage L*, a*, b* (CIELab), L* represents value or lightness(Alnassar, 2022).

Based on the results of a preliminary study, porcelain firing was carried out more than five times, 36.4% stated this was done for porcelain color correction. This research is important to determine the color changes of porcelain fused to metal restoration. They are fired repeatedly so that the manufacturing procedure is carried out correctly to prevent correction of anatomical shape and color.

Material and Method

In this research, two types of porcelain were used, IPS Classic metal porcelain and Noritake metal porcelain. Each group consisted of six specimens, so total of 12 specimens were prepared. The shape of the specimen is a disk with 2 mm of thickness and the diameter is 10 mm(Yılmaz et al., 2014). Nickel-chrome (0.5 mm thickness), was used as a coating. The thickness of porcelain veneers was 1.5 mm then fired in an ivoclar programmat P300 furnace ovenFigure 1. Specimens were made from porcelain Classic^®with A3 shade and porcelain Noritake® A3 shade are presented onFigure 2andFigure 3. This sample was made by porcelain fused to metal restoration method. There are two groups, the first uses materials porcelain Classic^®shade A3, with first firing (as a control), the second firing and, the third firing as a treatment group, and the second group used porcelain Noritake®A3 shade with first firing (as control), second firing and third firing as treatment group.

In this research, color testing used VITA Easyshade^®Figure 4and was carried out periodically. After the first stage of firing, color testing was carried out on both groups of porcelain as a control. After the second stage of firing, a second color test was carried out, and after the third stage of firing, a third color test was carried out.

Testing was carried out by placing the specimen in a mini-studio that had been given a white base with room lighting, then the tip was attached to the center of the specimen that had been determined. After that, the L*, a*, b* values that will appear on the tool monitor screen VITA Easyshade^®were recorded. The values obtained were calculated using a Formula 1.

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