What is the most appropriate action if a dental hygienist discovers a bubble in the cured sealant material?

When a dental hygienist discovers a bubble in the cured sealant material, the most appropriate action is to reetch, wash and dry the tooth, and apply additional material. This approach addresses the potential issue that the bubble may create by compromising the sealant's integrity and effectiveness.

Bubbles in sealant can create an area where bacteria might accumulate, potentially leading to decay underneath the sealant since the material may not properly bond to the tooth surface. Reetching helps to refresh the enamel's surface and improve the bonding conditions, while washing and drying ensures that the area is clean and free from moisture, which is critical for the proper adherence of the new layer of sealant. Applying additional material over the original sealant will seal any gaps created by the bubble, ensuring effective protection against caries.

This method is more comprehensive and effective than simply applying a surface sealant or leaving the bubble as is, as both alternatives do not address the underlying problem effectively. Additionally, removing the sealant entirely may be unnecessary and would create additional work and potential discomfort for the patient.