Fissure sealants: the occlusal surface is where caries starts most and the brush reaches least

The occlusal surfaces of the molars are where caries appears most frequently in childhood, and the reason is anatomical before it is behavioural.

Fissures and pits are narrower than the diameter of a toothbrush filament. No brushing technique, however correct, cleans them in depth.

They are also an ideal environment for biofilm: mechanically protected, with food substrate that stagnates there and little salivary turnover.

The sealant resolves the problem by physically closing that space, turning an irregular surface into a smooth and cleanable one.

The best moment is straight after full eruption, when the enamel is still immature and more susceptible, and before a lesion has had time to start.

For the first permanent molars this places the procedure around six or seven years of age, for the second molars around twelve. These are the windows in which sealing pays most.

A partially erupted tooth presents a practical problem: isolation is difficult and salivary contamination compromises adhesion. In that case it is better to wait or to use a material less sensitive to moisture.

Composite resins are the material with the best retention over time, but they require a dry field and correct etching.

Glass ionomers tolerate moisture better and release fluoride, but wear away faster. They are the reasonable choice when isolation cannot be achieved, as a provisional sealant to be reassessed.

Longevity depends almost entirely on the quality of isolation during placement, rather than on the material chosen. A sealant contaminated by saliva detaches within months.

This carries an obligation to review: sealants must be checked at every recall, because a partially detached one is worse than none, creating an enclosed niche.

A sealant replaces neither hygiene nor fluoride, and it does not protect the proximal surfaces. It covers one specific site, and it is on that site that it should be judged.

In summary: fissures are narrower than a filament and cannot be cleaned, the best moment is straight after eruption, resin lasts longer but needs isolation, glass ionomer tolerates moisture, and longevity depends on isolation more than on material.