Evaluation of the Absorbance and Transmittance of the Optical Light for Three Different Types of Composite Resin Stored in Artificial Saliva ( in vitro study ) ISSN : 1812 – 1217

Aims: To evaluate the Absorbance and transmittance of the optical light for three different types of light activated dental composite resin stored in artificial saliva. Materials and Methods: 30 specimens were prepared from light activated composite resin and divided in to three groups, G1: 10 specimens prepared from Els, G2: 10 specimens prepared from Tetric n Ceram, G3: 10 specimens prepared from Solitaire2. Absorbance of the optical light measured using spectrophotometer. The specimens were evaluated after (zero,1,7,28) day immersion time in artificial saliva. Results: Statistical analysis shows significant difference at P ≤ 0.05 among tested groups at same immersion time, Solitaire 2 showed highest absorbance means compare to Tetric, Els specially after 1 day immersion in artificial saliva. No significant difference P> 0.05 in absorbance mean at various immersion time in artificial saliva for each group. Els shows low absorbance and highest transmittance percentage T% than Tetric and Solitaire composite resin. Conclusion: The Els extra composite resin has lowest absorbance and highest transmittance means for optical light, Solitaire2 showed more absorbance means with less amount of light transmittance through the composite resin compare to Tetric and Els. The performance of the experimented groups statistically not significant in terms of immersion time in artificial saliva.


INTRODUCTION
Composite resin is a heterogeneous material that is composed of three major component (resin matrix, filler particles and saline coupling agent. Since 1960 dental composite has undergone a lot of changes in order to become a restorative material with acceptable aesthetic properties, recent advancement in direct dental restorative materials is the incorporation of the Evaluation of the Absorbance and Transmittance of the Optical Light for Three Different Types of Composite Resin Stored in Artificial Saliva (in vitro study) nanotechnology which is understanding and control mater at dimension of roughly 1-100nm, also new dental composite formulation reinforced by nano and micro filler dental restorative materials which include nanometric and micrometric inorganic particles as reinforcing fillers (1) .
In recent years resin composite have been used extensively as an alternative to dental amalgam, With this increase in the use has come, the desire to improve the various properties (absorbance, optical, physical mechanical) properties for resin composite (2) . In general, dental composite and other restorative filling materials used in dentistry are required to have long term durability in the oral cavity were the filling materials is in contact with saliva fluid, that contains a variety of inorganic species together with bacterial flora complex (2,3) .    air syringe before taking the reading (6) .

DISCUSIONS
The search for direct restorative material combining excellent esthetic with superlative physical, mechanical and biological properties has driven researches to study various properties of different restorative materials (10) .
For a long time, dental professionals were satisfied with restorations that showed excellent shape and contour, good marginal adaptation considering color and optical properties of secondary importance.
Possibly due to the limited knowledge of dental professionals about optical and physical properties, include absorbance and transmittance for the optical light (10,11) .
UV-Visible light spectrophotometer has been reported as an efficient method to verify the absorbance mean of the optical light for composite resin at wave length 245nm (5,6,10,11) .
The best results were achieved with specimens of composite that received surface finishing and polishing which attributed to the removal of the surface layer of the resin rich inorganic matter which susceptible to staining, also the specimens thickness standardized less then 1mm because increasing the specimens thickness effect on result and lead to increase light absorbance and reduce its light transmittance (5,6) .
Several factors such as polymeric matrix, refraction index, type of monomer, filler type and content can influence the light absorbance, transmittance and opacity of composite resins, these properties must be thoroughly evaluated in order to ensure esthetic longevity of a restoration (12,13 ,14,15) .

Absorbance and transmittance for composite resins stored in artificial saliva
reduce the amount of optical light transmittance increase the absorbance mean through the structure (6,16,17) (12) .
Nakamura etal (18) found that transmittance was not modified over time, in contrast, lambre etal (19) (21) conclude that transmittance parameter tend to varying according to individual brand of composite resin. Some authors state that the transmittance decrease with aging and this should be taken in consideration during shade selection of resin composite, absorbance means not effect on degree of radio opacity of composite resin (22) . The properties was noticeable improved (23) .