Unpolymerized Surface Layers on Sealants

Abstract

Oxygen inhibits radical polymerization, and for the present investigation, the thickness of the resulting unpolymerized surface layer on various proprietary dental polymers was measured by a microscopic technique. The inhibition depth of the polymerized resins varied from 7 to 84 μm. Resin systems with the tertiary aromatic amine 3, 4-xylyldiethanolamine as the activator had a thinner unpolymerized layer than those with p-tolyldiethanolamine. Increased viscosity also resulted in reduced thickness of the unpolymerized films. UV-light cured resins had thinner inhibited layers than those of comparable viscosity with a peroxide-amine initiator system. However, the thinnest unpolymerized film was seen with a chemically activated resin system containing acetone.

This investigation has shown that the thickness of the unpolymerized film on cured dental resins is related to the composition and the initiating system.

Key Words:

• Dental polymers
• oxygen inhibition
• substituent constants
• microscopy