Fissure and sealant treatment is considered part of primary preventive care when:

Sealants are an effective preventive measure against dental caries, especially in children and adolescents who are at a higher risk of developing cavities. The correct choice highlights that sealants are most beneficial when applied to newly erupted teeth, as these teeth are particularly vulnerable before they have fully matured or developed protective enamel.

Newly erupted teeth have deep pits and fissures that are difficult to clean and more susceptible to plaque accumulation and decay. By placing sealants on these teeth shortly after their eruption, dental professionals can effectively provide a barrier that helps prevent caries from forming in these vulnerable areas.

The other choices reflect aspects of sealant application that do not specifically align with the most effective timing for prevention. For instance, while placing sealants on teeth at high caries risk is important, the timing of application on newly erupted teeth is critical for maximally effective prevention. Sealants applied to all molars or as soon as the patient arrives may not consider the individual risk factors or the importance of applying them at the right moment for optimal protection, which primarily targets newly erupted surfaces.