Which characteristic helps in determining the bond strength of restorative materials?

The cleanliness of the surface before etching is a crucial factor in determining the bond strength of restorative materials. When bonding agents are applied to the tooth structure, they need a clean and adequately prepared surface to achieve optimal adhesion. Any contaminants, such as saliva, blood, or debris, can interfere with the bonding process by creating a barrier between the bonding agent and the tooth surface.

A clean surface allows for better penetration of the bonding agent into the micro-porosities of the tooth structure, enhancing mechanical retention and facilitating chemical adhesion. Furthermore, effective etching of the enamel or dentin requires a clean surface to expose the necessary bonding sites. If the surface is not clean, the bond strength can be significantly compromised, leading to potential failure of the restoration.

While the other factors mentioned, such as the properties of the bonding agent, duration of acid exposure, and temperature during application, do play roles in bond strength, they are not as foundational as the cleanliness of the surface prior to etching. A strong bond begins with proper surface preparation, making cleanliness paramount for achieving lasting adhesion in dental restorations.