Effect of Thermocycling on Colour Stability of Alkasite Restorative Material (Cention N)-An In Vitro Study

Introduction: Cention N is an alkasite based dental restorative material, it is far less expensive unlike composite materials, it has fluoride releasing property and the strength of cention N is comparable to that of dental amalgam restorations. Colour stability is one of the major and important characteristics in dentistry, dental restoration and esthetics. The aim of the study is to evaluate the colour stability of alkasite restorative material (Cention N) before and after thermocycling. Materials and Methods: Eight disc shaped samples of alkasite restorative material Cention N with 2 mm of thickness were prepared using a customised mould. After the disc sample preparation, they were numbered for identification and color stability was measured by using Vita easy shade advance spectrophotometer. L, a and b values were obtained before the thermocycling procedure. 1000 cycles of thermocycling was done which is equal to 6 months. The thermocycler used was TC Original Research Article Kishore et al.; JPRI, 34(6B): 52-57, 2022; Article no.JPRI.79238 53 4 SD Mechatronik. The colour stability value after thermocycling was again determined using the vita easy shade spectrophotometer. Control group samples were not subjected to thermocycling. The colour stability values prior and after thermocycling were obtained and tabulated. Results: Thermocycled cention N samples had low delta E values when compared to that of non thermocycled samples. Statistical analysis was done using spss software and independent t test was done. P value was found to be 0.616, showing that it is statistically insignificant. Conclusion: From this research we can conclude that thermocycling procedure has an effect on the colour stability of the cention N material. Thermocycled cention N samples had better color stability when compared to non thermocycled cention N samples.


INTRODUCTION
Composite resin materials are extensively used for dental restoration these days [1]. They contain mineral, glass and resin filler particles [2]. The conventional composite material contain large component of amorphous silica or quartz. Composite materials are classified as two types such as chemically and photochemically activated resin material. In dentistry, aesthetics plays a major role [3]. Many materials have come into dentistry for restoration material which have a good esthetic such that of the natural tooth and compressive stability of that of amalgam restoration [4,5]. Cention N is one such new product which is an alkasite based dental restorative material a resin-based self-curing powder liquid restorative material and it has the fluoride releasing ability which helps in the release of the hydroxyapatite in the tooth and helps in in the repair and remineralisation of the enamel, thus helping to prevent tooth sensitivity [6,7]. Cention-N is a novel bulk fill dental restorative material which can be used as self and light cure material. It has got sustained release of hydroxyl and fluoride ions in various conditions [8].
Thermocycling is also known as thermal cycling, a process in which the required substance is processed through a number of cycles between 2 extreme temperatures simultaneously [9][10][11]. Thermocycling is a test done to evaluate the product reliability and strength. In order to maintain a constant temperature, a water bath is needed for thermocycling. Particular standards, universal immersion time and temperature protocol is required for the test [12][13][14].
Thermocycling is most efficacious technique in the ageing process. The cycle holds alternate high and low temperatures [15].
Colour stability is a significant property of dental resin based materials. Composite resins contains few organic compounds which may lead to internal discoloration [16]. Compounds including amines and benzoyl peroxide which are required for the polymerization reaction, and the use of hydroquinone monomethyl ether as an inhibitor in the reaction [17]. A spectrophotometer is used to measure colour changes based on the Commission Internationale de l'Eclairage lab (CIELAB) system in 1976. L stands for perceptual lightness and the values will range from zero to hundred. A value means greenness to redness and b represents blueness to yellowness [18]. The human oral cavity is subjected to temperature stress [19]. The clinical success of dental restorative materials is related to colour stability. Thermal shocks in the oral environment can induce material degradation as well as colour shifts in dental materials. As a result, it's crucial to understand how thermocycling affects the colour stability of commonly used dental restorative materials. The aim of the study is to evaluate the colour stability of alkasite restorative material (Cention N) before and after thermocycling.

Sample Preparation
The research was done at White Lab, Saveetha Dental College and Hospital, Chennai, India. For this study, cention N restorative material was taken. Eight disc shaped samples of alkasite restorative material Cention N with 2 mm of thickness were prepared using a customised mould. 4 samples in test and 4 samples in control group. Random sampling method was followed and three investigators were involved,

Pre Thermocycling Color Stability Testing
After discs preparation, they were numbered and colour stability was tested using a Vita easy shade advance spectrophotometer, and the precolor value was measured. Prior to thermocycling, the L, a, and b values were determined.

Thermocycling
The samples were placed in a thermocycler and subjected to 1000 cycles, which equated to 6 months. When it was cold, it was 10°C, and when it was hot, it was 60°C. The draining time was determined to be 10 seconds and the dwelling time was determined to be 30 seconds. The thermocycler used in this experiment was the CS 4.2-SD Mechatronik. The samples in the control group were not subjected to thermocycling.

Post Thermocycling Color Stability Testing
The colour stability value after thermocycling was again determined using the vita easy shade spectrophotometer. Then the pre and post thermocycling values were compared and delta E values was analysed using the formula: ΔE( L* a* b* ) = [(ΔL*)2 + (Δa)2 + (Δb)2].

Statistical Analysis
The delta E values were obtained and the values were tabulated, with the tabulated values "Independent sample t test" was performed using the statistical software "SPSS version 23". P value less than or equal to 0.05 is considered to be significant. The result of the analysis carried out was depicted in the form of bar graphs and tables.

RESULTS AND DISCUSSION
The primary outcome of study is the color stability evaluation of cention N material and effects of thermocycling on the material. From Cention N is an alkasite based dental restorative material, it is far less expensive unlike composite materials, it has fluoride releasing property and the strength of cention N is comparable to that of dental amalgam restorations. Thermocycling is one of the procedures used to calculate a variety of factors such as age, colour, and so on [20]. The colour of the composite before and after thermocycling was the main focus of this research. A Arikan et al did a study on pink and white acetal resin with one ordinary polyresin to investigate the colour stability of the resin material after thermocycling. The mean value of the materials was calculated based on the results. On long exposure to 100 hours of simultaneous thermocycling, conventional poly resin exhibited 0.69, white acetal resin showed 0.74, and pink acetal resin showed 0.77. [21].
Arregui et al presented a study to explain the colour stability of two self-adhesive composites. After immersing the composites for ten days, the delta E values were recorded. Water had no effect on the colour shift, according to the findings [22].
Bhattacharya conducted another in vitro study on the impact of thermocycling on the colour stability of aesthetic materials. The colour stability of cention N, Fuji IX GP Extra, and Fuji IX GP after thermocycling was compared in this study. A spectrophotometer was used to determine the colour characteristics of the discs. The materials were separated into three categories. From the result he concluded that Cention N had superior color stability when compared to glass ionomer cement material [23]. Similarly, our study had better color stability in thermocycled cention N samples.

CONCLUSION
From this research we can conclude that thermocycling procedure has an effect on the colour stability of the cention N material. Thermocycled cention N samples had better color stability when compared to non thermocycled cention N samples. Thus, thermal stresses in oral cavity may have an influence in the color stability of restorative material such as cention N, because we observed an increased color stability in thermocycled restorative material group.

CONSENT
It is not applicable.

ETHICAL APPROVAL
It is not applicable.