Sealers are protective materials applied to surfaces to block out moisture, bacteria, or other unwanted substances. In medicine and dentistry, the term covers several distinct products: dental sealants that coat teeth to prevent cavities, endodontic sealers used inside root canals, and surgical sealants that stop fluid leaks during operations. Each type works differently, but they share the same core idea of creating a barrier where one is needed.
Dental Sealants: The Most Common Type
Dental sealants are thin coatings painted onto the chewing surfaces of back teeth (molars and premolars) to prevent cavities. They fill in the tiny grooves and pits where food particles and bacteria tend to collect, places a toothbrush can’t always reach. The CDC reports that dental sealants prevent 80% of cavities over two years in back teeth, where 9 out of 10 cavities occur. School-age children without sealants have nearly three times as many cavities in their first molars as children who have them.
Sealants are most commonly placed on children’s permanent molars shortly after they come in, typically around ages 6 and 12. But adults with deep grooves in their teeth can benefit from them too. With proper care, dental sealants can protect teeth for up to 10 years, according to the American Dental Association.
What Dental Sealants Are Made Of
There are three main categories. Resin-based sealants are the most widely used and contain an organic resin matrix, often built around a compound called Bis-GMA. Some versions include fluoride particles that slowly release fluoride into the tooth over time. Glass ionomer sealants are made from a powdered glass mixed with an acidic liquid, and they also release fluoride. Hybrid sealants combine elements of both, mixing resin with glass ionomer components to get the benefits of each.
Resin sealants tend to be more durable, while glass ionomer versions release more fluoride but wear down faster. Your dentist will choose based on the tooth’s location and how cooperative the patient is during placement, since resin sealants require the tooth to stay completely dry during application.
How Dental Sealants Are Applied
The process is painless and takes only a few minutes per tooth. First, the tooth is cleaned, sometimes with just a toothbrush. The tooth is then isolated with cotton rolls or other barriers to keep it dry. Next comes acid etching: a mild acid solution sits on the tooth surface for 15 to 20 seconds, creating a slightly rough texture so the sealant can grip. After rinsing and drying (the enamel should look frosty white), the liquid sealant is flowed into the grooves from one end of the fissure to the other, avoiding air bubbles. Finally, a curing light hardens the material in seconds.
If saliva touches the etched tooth before the sealant is placed, the process has to restart with re-etching. This is why keeping the tooth dry is the single most important step for long-term success.
Cost, Safety, and Longevity
Dental sealants typically cost $40 to $70 per tooth without insurance. Many dental plans cover them as preventive care, especially for children, though coverage varies. If cost is a concern, school-based sealant programs offer them free in many areas.
Some parents worry about BPA exposure, since the resin in sealants is manufactured using a BPA-related compound. Research modeling BPA exposure from dental sealants found that the amounts are negligible. The median exposure is under 10 nanograms per treatment, which is less than 3% of the BPA a person already encounters from everyday sources like food packaging. These levels pose no meaningful health risk.
Several factors affect how long sealants last. Hard or sticky foods can chip them. Teeth grinding wears them down faster. Acidic foods and drinks speed erosion. Regular dental checkups let your dentist spot worn areas and reapply sealant before the protection is lost.
Sealants vs. Fluoride Varnish
These two preventive treatments work in completely different ways. Sealants create a physical barrier over the tooth surface, blocking bacteria from settling into grooves where they’d otherwise feed and produce acid. Fluoride varnish, on the other hand, is a chemical treatment. It strengthens the mineral structure of enamel, making it more resistant to acid attack, and can even reverse very early decay. Sealants are best for the pitted chewing surfaces of molars, while fluoride varnish protects all tooth surfaces, including the smooth sides between teeth. Many dentists recommend both.
Endodontic Sealers: Inside Root Canals
Endodontic sealers are a different product entirely. During a root canal, the dentist removes infected tissue from inside the tooth and fills the empty canals with a solid material. The sealer is a cement-like paste that fills microscopic gaps between the filling material and the canal walls, creating an airtight seal that prevents bacteria from re-entering.
These sealers come in several formulations. Zinc oxide eugenol sealers have been used for decades and are among the oldest options. Resin-based sealers offer strong bonding to the canal walls. Bioceramic sealers are the newest category and have gained popularity because their chemical structure closely mimics natural tooth and bone mineral, which promotes better bonding and is well tolerated by surrounding tissues.
Bioceramic sealers have one notable drawback: once they harden, they’re very difficult to remove. If the tooth ever needs retreatment or a post placed inside the canal, removing a set bioceramic sealer is significantly more challenging than removing older types.
Surgical Sealants: Stopping Leaks During Operations
In surgery, sealants serve as barriers to prevent leaks of blood, air, or other body fluids. They’re distinct from sutures or staples, which hold tissue together mechanically. Sealants fill gaps, patch punctures, and control bleeding in places where stitching alone isn’t enough.
The two broadest categories are biological and synthetic. Fibrin glue, derived from blood plasma proteins, was first used for nerve repair in 1940 and remains the only material with FDA approval for use as an adhesive, sealant, and blood-stopping agent all in one. Products like Tisseel are used across a wide range of surgeries, from hernia repair to thoracic procedures, to prevent leaks at connection points between tissues.
Cyanoacrylate-based sealants, synthetic “super glue” relatives, were first used for wound closure in 1959. They provide tensile strength comparable to absorbable sutures and also act as a microbial barrier during healing. On the skin, products like Dermabond and LiquiBand are commonly used in emergency rooms to close cuts without stitches. One cyanoacrylate product, Omnex, became the first of its kind approved by the FDA for internal use, specifically for sealing blood vessels to block the passage of blood, body fluids, and air. Cyanoacrylates are generally limited to topical use because they can cause irritation inside the body.
Hydrogel Sealants in Eye and Joint Surgery
Hydrogel sealants are a newer class made from water-absorbing polymers that can hold over 90% water within their structure. In 2014, the FDA approved a hydrogel sealant (ReSure) specifically for sealing incisions after cataract surgery. These gels form in place after being injected as a liquid, conforming to irregular wound shapes and sealing corneal wounds without sutures. Researchers are also investigating hydrogels as substitutes for the vitreous humor, the clear gel that fills the eye, after retinal detachment surgery. Beyond ophthalmology, injectable hydrogels are being studied and used in orthopedics, neurology, and other fields where a flexible, biocompatible seal is needed in hard-to-reach tissue.