Dental sealants are thin, plastic coatings applied to the chewing surfaces of teeth, primarily the molars and premolars. These surfaces contain deep, narrow depressions called pits and fissures that are difficult to clean with a toothbrush. The sealant material acts as a physical barrier, effectively sealing off these vulnerable grooves from food particles, plaque, and acid-producing bacteria that cause tooth decay. This simple, non-invasive procedure is a highly effective method of preventing cavities, creating a smooth surface that is easy to keep clean.
The Resins and Fillers Used in Sealants
The primary component of most contemporary dental sealants is a polymer-based material, often referred to as a resin. This resin matrix is made up of various monomers, small molecules that link together to form a long, durable plastic chain during the hardening process. Common monomers used include Bisphenol A-Glycidyl Methacrylate (Bis-GMA), Urethane Dimethacrylate (UDMA), and Triethylene Glycol Dimethacrylate (TEGDMA). TEGDMA is often added to reduce viscosity, allowing the sealant to flow easily and penetrate the deepest parts of the fissures. Once placed, a special blue light initiates polymerization, curing and hardening the material in seconds.
Sealants are broadly categorized based on their composition as either filled or unfilled, determined by the inclusion of microscopic filler particles. Filled sealants incorporate materials like glass, quartz, or silica to increase the material’s strength and resistance to abrasive wear from chewing. While these additions enhance durability, the increased viscosity can sometimes slightly hinder the sealant’s ability to flow into the finest crevices. Unfilled sealants flow more readily into the tooth’s anatomy but may not offer the same level of long-term wear resistance.
Understanding Bisphenol A and Related Compounds
Concerns often arise regarding the presence of Bisphenol A (BPA) in dental sealants, given its classification as an endocrine-disrupting compound. Pure BPA is not intentionally added to the final product, but trace amounts can be present as an impurity from the manufacturing of the resin monomers. The most commonly used monomer, Bis-GMA, is a derivative of BPA. Although Bis-GMA is chemically stable, it can potentially degrade into minute amounts of BPA through salivary enzymes or incomplete curing.
Major health and dental organizations, including the American Dental Association (ADA) and the Food and Drug Administration (FDA), have reviewed the scientific evidence extensively. Their consensus is that the exposure to BPA from dental sealants is minimal and poses no known health risk to patients. The amount of BPA released is transient and extremely low, often measured in nanograms, which is far below established safe daily exposure limits. Dental professionals recommend that patients rinse their mouth thoroughly immediately after the sealant is cured to wash away any residual, unreacted monomer.
How Sealants Are Applied
The successful placement of a dental sealant relies on a precise, multi-step application procedure to ensure a strong, long-lasting bond with the tooth enamel. The process begins with a thorough cleaning of the tooth surface to remove any plaque and debris from the pits and fissures. Next, the tooth is completely dried and isolated from saliva using cotton rolls or a rubber dam, as moisture interferes with the bonding process.
A mild acidic solution, typically phosphoric acid, is then applied to the chewing surface for a short period, a step known as etching. This etchant creates microscopic pores and a rough surface texture on the enamel, which is necessary for the mechanical retention of the liquid sealant. After the etching solution is rinsed off and the tooth is re-dried, the flowable resin is carefully painted onto the prepared grooves.
The liquid sealant flows into the newly created micro-porosities and anatomical grooves, forming mechanical tags that anchor the material to the tooth. Finally, a specialized curing light, often a blue LED light, is directed at the tooth to rapidly polymerize and harden the liquid resin. The entire process is quick, painless, and does not require drilling or anesthesia.