The days of filling some type of tray with a fluoride gel or foam, placing it in the mouth of a patient, and allowing it to dwell intraorally for four minutes or so seem to be at an end. And it is unlikely that many professionals as well as patients will grieve over this demise as this entire process is quite unpleasant, especially for gaggers.
Replacing the gels and foams are fluoride varnishes, which now seem to be the standard in office-based caries prevention.
The varnishes typically contain 5% sodium fluoride in some sort of resin/alcohol vehicle. After they are applied to teeth, they deliver a powerful booster of fluoride and keep it there longer than other types. Estimates of varnish efficacy range from 1-7 days compared to the 10-15 minutes of gels or foams.
However, what is interesting about the products in this category is that none of them include caries prevention as an indication. All of them list desensitization as an indication, while two also mention being used as a cavity varnish (only one of these two limits this specific use to under amalgams).
Not mentioning caries prevention as an indication is curious since there is substantial research validating this use, but the FDA is evidently unimpressed. Instead, they are being promoted off-label, which is the FDA terminology that states, in essence, that you (a dentist) can use a product in a way that is not approved if you base your action on firm scientific rationale.
While twice-a-year application seems to be effective in low-medium risk patients, a quarterly schedule appears to be more applicable for high risk children. And starting this application in high risk patients as young as one year old seems prudent. Note that the risk of fluorosis is highly unlikely even if a quarterly application regimen is employed.
As far as safety is concerned, the manufacturers of the three products in this section recommend that patients restrict using other types of fluoride supplements for up to four days to prevent any possibility of an overdose, although no cases of toxicity have been reported. Nevertheless, it has been suggested that extra care be taken when you apply a varnish in an infant or toddler.
Since all of the products virtually set instantly on teeth as soon as they are exposed to saliva, questions about how excess ingestion could occur pop up. According to information from DMG America, excess varnish could be ingested if it was applied accidentally to soft tissue to which it will not adhere, if it was applied too thickly and flaked off, and/or if a patient was too aggressive and ate hard foods the day it was applied (causing the varnish to dislodge).
These products should be applied to teeth that are reasonably clean. This does not mean that it is essential that they need to be applied immediately after a prophy, but that is obviously the most optimal time. Otherwise, wipe the teeth with a 2x2 or something similar to remove any visible plaque and excess saliva. Although they do not require a completely dry field, too much saliva can dilute their efficacy and interfere with their application.
While the three products in this section contain the same basic formula to protect teeth, including being white instead of the old, yellow color of previous generations, they have enough differences to make it an interesting comparison.