Get pit-and-fissure sealants once the permanent molars come in

Moderate value
Evidence A
Buys life
For: Child aged 3–18
Costs a little
Takes minutes
No willpower

In plain words

A pit-and-fissure sealant (窝沟封闭) uses resin to seal the grooves on the chewing surface of the big back teeth, so food debris can't get stuck in them. Two years after it is done, the chance of cavities is about one eighth of that without sealing. Without it, 16% of tooth surfaces get cavities, and with it only about 5%. It is still effective after four years.

Cost: A few dozen to one or two hundred yuan per tooth. No anesthetic and no drilling, and it takes a few minutes. Many places have free programs for children of the right age.
What you get: Cochrane searched systematically and pooled 38 trials with 7924 children aged 5 to 16. They compared resin-based sealants with no sealant. For the first permanent molars of children aged 5 to 10, 24 months after the sealant was placed the OR for developing cavities was 0.12 (95% CI 0.08–0.19), so the chance of cavities was about one eighth of that without sealant. This result comes from 7 trials, with 1548 children randomized and 1322 examined at the end, and the quality of evidence was moderate. If 16% of tooth surfaces in the control group had cavities within 24 months, the figure after sealing was 5.2% (3.13%–7.37%). With 40% in the control group it was 6.25% (3.84%–9.63%). With 70% in the control group it was 19% (12.3%–27.2%). At 48 to 54 months the OR was 0.21 (0.16–0.28), still about one fifth of that without sealant. The authors concluded that at 24 months resin sealants led to 11% to 51% fewer cavities than no sealant. In the 4 trials that recorded adverse effects, none occurred. There is not enough evidence on which of the other sealing materials, such as glass ionomer, is better.
Notes: The first permanent molar (the big tooth that is never replaced) generally comes in at about age 6, and the second at about age 12. Sealing should be done when the tooth has just come in and is not yet decayed; if it has already decayed, all that can be done is a filling. Many areas list sealants for children of the right age as a free service; ask the local Center for Disease Control and Prevention (疾控中心) or community health service center (社区卫生服务中心). This section did not find a national document that could be checked word for word, so it does not state the coverage or age range. Tooth decay is also one of the items emphasized in the school checkup; see §30.7.
Evidence grade: A : Specific numbers from meta-analyses, large cohorts or randomized trials; for law and policy, the statute or official text.
Sources: Ahovuo-Saloranta A, et al. (2017). Pit and fissure sealants for preventing dental decay in permanent teeth. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.CD001830.pub5

Translated from the Chinese original. Original book, section 30, tip 13. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer