A Survey of Efficacy of QTH Light-curing Units Used in Dental Offices in Toronto -- Relative Hardness of a Resin Composite

*0949 A Survey of Efficacy of QTH Light-curing Units Used in Dental Offices in Toronto -- Relative Hardness of a Resin Composite*
B. SHOKATI¹, W. EL-BADRAWY¹, O. EL-MOWAFY¹, O. SOLIMAN¹, J. KERMALLI¹, R. ZAWI¹, F. RAJWANI¹, A. ENCIOIU¹, and K. SHEIKH², ¹ University of Toronto, Canada, ² New York University Purpose: the aim of this investigation was to determine efficacy of QTH light curing units used in a sample of dental offices in Toronto through measurements of hardness of a resin composite. Methods: following specific criteria for inclusion a total of 50 dental offices were selected and took part in the investigation. Selection criteria included that the dentist routinely placed posterior composite restorations. Two investigators visited each of the 50 offices to prepare specimens for hardness testing. A resin composite (Charisma, A20) was used to prepare disc specimens 2.5 mm thick using a special mold. Two specimens were light cured for 20 s from top surface only. Using a Knoop hardness tester, 4 Knoop Hardness Numbers (KHNs) were obtained from top surface and 4 from bottom surface of each specimen. Mean KHNs were calculated and relative hardness (hardness of bottom/top surface) was determined. Light intensity of each curing unit was measured with a light meter and a correlation was made between light intensity and relative hardness (RH). A total of 100 light curing units were included in the study. Results: A wide range of RH values obtained with the different curing units was found. For units with light intensity values ranging from 200 - 800 mW/cm2 RH values ranged from 10% to 80%. Some units with similar light intensities had RH values that varied considerably. This might be due to variation in wavelength. Conclusions: RH values varied considerably among the curing units with some producing values as low as 10%. A direct correlation was observed between light intensity and RH. Periodic testing for efficacy of light curing units used by dentists should be enforced by regulatory bodies of the dental profession to ensure optimum quality of restorations. Approved by Faculty of Dentistry Research Committee and supported in part by SDS/Kerr.
Seq #106 - Color and Surface Roughness of Restorative Materials 3:45 PM-5:00 PM, Thursday, 26 June 2003 Svenska Massan Exhibition Hall B
Back to the Dental Materials: VIII - Others-Non-metallic Program Back to the 81st General Session of the International Association for Dental Research (June 25-28, 2003)
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