Australian Dental Council (ADC) Practice Test

After etched composite resins set, they can experience a process of contraction. This contraction typically occurs as the resin undergoes a polymerization reaction, where the monomers in the composite resin join together to form a solid structure. During this reaction, the material can shrink slightly due to the loss of volatile components and the inherent nature of polymer formation.

The contraction is important for dental applications because it can affect the bond strength between the composite and the tooth structure. If the contraction is significant, it may lead to gaps or microleakage, which can compromise the durability of the restoration and the health of the surrounding tooth structure.

The other options—remaining the same size, expanding, or breaking apart—do not accurately describe the behavior of composite resins upon setting. While some materials may expand during the curing process under specific conditions, typical behavior for composite resins after they have set is to contract. Understanding this contraction is essential for predicting the behavior of composite materials in clinical settings.