Influence of two photoactivation modes on the hardness of packable and conventional resin-based composites / 中国组织工程研究

ABSTRACT

BACKGROUND: Soft-start is a newly photoactivation mode, which has certain effect on composite resin. However, previous study mainly concentrated on the conventional resin-based composites, the reports regarding soft-start on packable resin-based composites is poorly understood. OBJECTIVE: It is assumed that soft-start photoactivation had effect on packable resin-based composites, in addition, to investigate its effect on the hardness of packable resin-based composites. DESIGN, TIME AND SETTING: A double factors design. The experiment was performed at the Department of Stomatology, First Affiliated Hospital, Sun Yat-sen University and Chemical Mine Metal Material Test Laboratory, Guangdong Inspection and Quarantine Technology Center in October 2007. MATERIALS Three packable resin-based composites were Ecusphere-Carat (EC, DMG Company, Germany), Filtek P60 (P60, 3M EPSE Company, USA), Tetric Ceram HB (HB, Ivoclar Vivadent Company, Liechtenstein) and a conventional composite FiltekZ250 (Z250, 3M EPSE Company, USA). The color of composites was A3. METHODS: Three packable resin-based composites and a conventional composite were filling in a cylindrical container (7 mm diameter, 4 mm depth), to obtain 80 samples, and then were divided into different groups according to the composite and photoactivation mode (n=10). In the soft-start photoactivation, samples were irradiated by 300 mW/cm~2 for 10 s, and then 600 mW/cm~2 for 30 s. Standard photoactivation was irradiated with 600 mW/cm~2 for 40 s.MAIN OUTCOME MEASURES: The microhardness of the top and bottom of the specimens was determined by Vickers microhardness tester. RESULTS: Three packable composites had higher hardness values than conventional composite. Though soft-start photoactivation could decrease the hardness of packable composites, the difference had no significant difference to standard mode (P > 0.05). There was significant difference on the top hardness and on the bottom hardness of conventional composite between two photoactivation modes (P < 0.05). CONCLUSION: The soft-start mode and resin-based composites should be selected carefully according to different filing areas.