What is the most likely reason for sealant failure?

Sealant failure is often attributed to contamination, which is the correct choice in this scenario. Contamination occurs when foreign substances, such as saliva, blood, or debris, are present on the tooth surface before the sealant application. These contaminants can prevent the sealant from properly adhering to the enamel, leading to a compromised seal that is more susceptible to failure over time.

While inadequate curing, poor material choice, and incorrect application technique can all contribute to issues with sealants, contamination directly affects the bond between the sealant and the tooth structure. Proper isolation of the tooth surface and ensuring it is clean and dry is critical for successful sealant application. Thus, paying close attention to contamination is essential in preventing sealant failure.