Khulood Abdulaziz Al-mansour, Anfal Mohammad Al Qussier.
The effect of 10% carbamide peroxide bleaching gel on the microhardness of ips empress direct: an in-vitro study.
Pak Oral Dental J Jan ;35(3):504-8.

The aim of the present in vitro study was to evaluate the effect of 10% carbamide peroxide home bleaching gel on surface microhardness of nanohybrid composite resin restorations (IPS Empress Direct, Dentin A2 and BL shades, Ivoclar-Vivadent, AG, Schaan, Liechtenstein). Forty Specimens of the nanohybrid resin composite were fabricated, cured and polished; 20 for each shade, 10 each for control and bleached groups. The bleaching agent, 10% carbamide peroxide home bleaching gel (NiteWhite®, ACP, Discuss Dental, Culver City, CA, USA) was used for 14 days in the treated groups. The specimens were subjected to Vickers hardness test using Universal testing machine (Micromet® 2100, Buehler, Lake Bluff, IL, USA) with load 300g and for 15 seconds. Statistical analysis conducted at a significance level of P< 0.05 using independent T-test. There was no significance differences between control and bleached groups within the same shade (P=0.302 for A2 shade, and P=0.332 for BL shade). It was concluded that 10% carbamide peroxide home bleaching gel (NiteWhite®, ACP, Discuss Dental, Culver City, CA, USA) has no effect on the surface microhardness of nanohybrid composite (IPS Empress Direct, Dentin A2 and BL shades, Ivoclar-Vivadent, AG, Schaan, Liechtenstein) in both the chosen shades.

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