Dental sealants are a thin, protective plastic coating applied to the chewing surfaces (occlusal surfaces) of the back teeth, such as molars and premolars. These surfaces contain natural pits and deep grooves. The primary function of a sealant is to create a smooth barrier, blocking food particles and cavity-causing bacteria from settling into these depressions. This simple, non-invasive procedure significantly reduces the risk of tooth decay in vulnerable areas.
The Primary Ingredients
Dental sealants are predominantly resin-based composites, blending organic polymer matrices and inorganic fillers. The liquid resin matrix forms the backbone of the material and is composed of various methacrylate monomers. Common components include Bisphenol A-glycidyl methacrylate (Bis-GMA), Urethane Dimethacrylate (UDMA), and Triethylene Glycol Dimethacrylate (TEGDMA). These monomers determine the sealant’s flowability and ability to harden.
Inorganic fillers, such as microscopic glass or quartz particles, are incorporated into the resin to enhance the sealant’s strength and resistance to wear from chewing forces. Sealants are classified as either filled or unfilled based on the volume of these particles. Filled sealants have a higher concentration of inorganic material, making them more durable but requiring a minor adjustment after placement to ensure a smooth bite.
Unfilled sealants contain less than 10 percent filler by weight, resulting in lower viscosity and greater fluidity. This allows the material to flow deeply into the narrow pits and fissures. They self-adjust with normal chewing, eliminating the need for mechanical adjustment after hardening.
Glass Ionomer Sealants
An alternative type of sealant is glass ionomer, which is a blend of glass powder and organic acids. This material is valued because it is completely Bisphenol A-free and releases fluoride over time.
Application and Curing Process
The application of a dental sealant is a straightforward process beginning with a thorough cleaning of the tooth surface to remove plaque and debris. The tooth must then be isolated and kept completely dry, as moisture prevents the resin from bonding effectively. Next, a mild acidic solution, typically 38% phosphoric acid, is applied to the chewing surface. This etching step creates microscopic porosities in the tooth enamel necessary for mechanical retention of the sealant material.
The tooth is then thoroughly rinsed and dried again; a properly etched surface will appear chalky white. The liquid sealant material is carefully painted onto the prepared surface, flowing into the etched pits and grooves. Finally, the material is hardened through polymerization, activated by a high-intensity curing light. This process rapidly transforms the liquid resin into a solid, durable plastic barrier firmly bonded to the tooth enamel.
Addressing Material Safety Concerns
A concern often raised about resin-based dental sealants is the potential for trace amounts of Bisphenol A (BPA) to be released. Some methacrylate monomers used in the material, such as Bis-GMA, are derivatives of BPA. Studies confirm that a very small, transient release of BPA can occur, primarily in the hours immediately following placement due to the breakdown of residual components by salivary enzymes.
This minimal exposure is not considered a health risk, as it is significantly lower than established safe daily limits set by major regulatory bodies. For instance, the exposure from a dental sealant application is minute compared to exposure from common environmental sources like food containers and air. Health organizations, including the American Dental Association, conclude that the public health benefit of preventing cavities far outweighs the negligible and temporary exposure to these trace elements.