Dental sealants are a protective plastic coating applied to the chewing surfaces of back teeth to prevent decay. These surfaces contain small grooves and pits that can trap food and bacteria, making them highly susceptible to cavities. Applying sealants requires isolation, keeping the prepared tooth surface completely dry and free from contaminants. This dry environment is fundamental for the material to bond effectively.
Why a Dry Field is Essential for Sealants
The necessity for a dry field stems directly from the chemistry of resin-based sealant materials, which are inherently hydrophobic (repel moisture). Before application, the tooth enamel is treated with an acid etchant (typically phosphoric acid) to create microscopic pores and improve mechanical retention. This etching process leaves the enamel surface porous and highly reactive.
The presence of saliva, gingival fluid, or moisture immediately compromises the newly etched surface. Salivary proteins and fluids block the channels created by the acid, preventing the liquid sealant resin from penetrating and forming a strong bond with the enamel. This contamination results in compromised adhesion, leading to microleakage. Microleakage allows oral fluids and bacteria to seep underneath the sealant, potentially causing decay or premature sealant loss. Maintaining dryness is directly linked to the longevity and preventive success of the sealant.
Non-Mechanical Isolation Techniques
Many isolation methods focus on absorption and deflection to manage moisture without using a rigid barrier. The most common technique involves placing highly absorbent cotton rolls into the cheek and tongue folds (buccal and lingual vestibules). For mandibular (lower) teeth, cotton rolls are positioned on the cheek side and under the tongue to absorb the continuous flow of saliva from the major glands.
To enhance the effectiveness of cotton rolls, absorbent pads known as dry angles are often used. These triangular pads cover the opening of the Stensen’s duct, a major source of saliva, while also retracting the cheek for better visibility. A high-volume evacuator (HVE) or a saliva ejector is used continuously to suction away accumulated fluids and control moisture. This combination of absorbent materials and constant suction is a practical and comfortable method, though saturated cotton rolls must be quickly exchanged to prevent recontamination.
The Use of Rubber Dam Isolation
The rubber dam is the most effective method for achieving absolute moisture control during sealant placement. This technique involves a thin sheet (latex or non-latex) that mechanically isolates one or more teeth. A hole is punched for the specific tooth being treated, and the dam is stretched over the tooth. It is held in place by a clamp that fits snugly around the tooth near the gum line.
The sheet is secured and held taut by a frame positioned outside the mouth. This physical barrier prevents contact between the tooth surface and saliva, blood, or oral tissues, creating an uncontaminated work area. The rubber dam also protects the patient from swallowing or aspirating small instruments or the acidic etchant. While placement requires specialized tools and can be time-consuming, the absolute isolation it provides maximizes sealant retention and longevity.
Factors Influencing Method Selection
The choice between a rubber dam and non-mechanical techniques depends on several practical considerations. Patient cooperation and age are primary factors, as rubber dam placement can be challenging for very young or highly anxious children. In these instances, a combination of absorbent materials and high-volume suction is often chosen for a faster, more comfortable procedure.
The location and eruption status of the tooth also play a role, as a rubber dam clamp cannot be securely placed on a partially erupted tooth. Procedures involving multiple teeth may benefit from the efficiency of a quadrant-based cotton roll system. Conversely, a single tooth requiring the highest degree of isolation may warrant the use of a rubber dam. Ultimately, the dental professional weighs the need for absolute dryness against the patient’s tolerance and the risk of salivary contamination.