Effect of light guide tip diameter on the degree of conversion and depth of cure of bulk-fill composites

Abstract

Purpose: This study aimed to evaluate the effects of the light guide tip diameter on the degree of conversion, micro-hardness, and depth of cure of bulk-fill composites compared to a conventional composite. Materials and Methods: Layers of Tetric EvoCeram (2 mm), Tetric EvoCeram Bulk Fill (4 mm), SonicFill 2 (5 mm) were placed in 4 mm diameter molds and were cured with LED light curing unit having 13/8 or 13/4 mm diameter turbo light guide tips for 10 s with a total number of 60 samples (n=5). Then, specimens were stored in a dark and dry environment at 37°C for 24 h, and Vickers micro-hardness values of the top and bottom surfaces of 30 specimens were measured. The other 30 specimens were pulverized, and the degree of conversion values of the specimens was measured with FTIR-ATR. The depth of cure was determined by proportioning the bottom surface's micro hardness value to the top surfaces. Data were analyzed with the Shapiro-Wilks test, Student’s t-test, and Pearson’s correlation analysis (p < 0.05). Results: The degree of conversion and the depth of cure of bulk-fill composites cured with 13/8 mm diameter tip were higher than those cured with 13/4 mm diameter tip (p<0.01). The degree of conversion of the bulk-fill composites applied in the layer thickness recommended by the manufacturer was below the clinically accepted rate of 55%, and the depth of cure remained below 80%. Conclusion: The curing of bulk-fill composites with light guide tips of different diameters affects the degree of conversion and the depth of the cure.

Keywords

• Bulk-fill composite
• degree of conversion
• depth of cure
• light-guide tip diameter
• micro-hardness

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