Objectives: Daily dental practice presents a definitive need for repairing and resurfacing previously placed composite restorations. This study evaluates two adhesives designed for addition of composite material to aged composite

Methods: 112 matrices were placed into 1inch methylmethacrylate cylinders and filled with composite. 56 filled with Amazon™ (Medidenta Inc),56 filled with Vit-l-escence™ (Ultradent). Each was light polymerized for 30 Seconds with LED - (Flashlite tm; 1001- Discus Dental). Test samples were ground flat & polished with 320 grit wet-dry emery cloth. Samples were aged in water at 37 degrees C for 2 months prior to testing. Adhesives selected for testing - Add&Bond tm; (Parkell inc) and Simplicity tm; (Apex Dental).

Upon removal from water, samples were dried and treated with 50µ Al2O3 spray - 80 PSI, - 5 seconds. Adhesives were applied as instructed and 2.38mm diameter X 1.5mm high composite posts of the same composite as the base were place and polymerized. Test samples were separated into 4 testing categories of 28 samples each. Add&Bond/Amazon; Add&Bond/Vit-l-escence; Simplicity/Amazon; Simplicity/Vit-l-escence. Using a Universal Testing machine notched blade apparatus with a crosshead speed of 1mm per minute, 14 samples of each category were stressed to fracture immediately and 14 of each were fractured following 4 month aging in water at 37 degrees C.

Results: Averaged (std dev)
Immediate
Add&Bond/Amazon		= 15.04mPa	(3.38)
Add&Bond/Vit-l-escence		= 14.86mPa	(3.24)
Simplicity/Amazon		= 25.64mPa	(2.70)
Simplicity/Vit-l-escence		= 25.69mPa	(3.36)
Four Months
Add&Bond/Amazon		=27.72mPa	(2.92)
Add&Bond/Vit-l-escence		=26.85mPa	(5.59)
Simplicity/Amazon		=37.15mPa	(4.82)
Simplicity/Vit-l-escencs		=32.36mPa	(4.98)

Conclusions: In-vitro testing indicates the ability of bonding to aged composite using contemporary adhesives. Immediate bond strengths were considerably lower than those after four months. Simplicity produced significantly greater bond strengths than Add & Bond. It should be noted that in several instances the composite substrates cohesively failed prior to adhesive failure.

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