**Core Concept**
Pit and fissure sealants are a type of dental restorative material used to prevent tooth decay in the occlusal (chewing) surfaces of teeth. The primary mechanism of action involves the physical barrier created by the sealant, which prevents the accumulation of bacteria and plaque in the pits and fissures of the teeth.

**Why the Correct Answer is Right**
Pit and fissure sealants are bound to the tooth surface through a process called micromechanical retention. This involves the creation of micro-retentions between the sealant material and the tooth enamel, which helps to prevent the sealant from coming loose over time. The sealant material, typically a resin-based material, flows into the small pits and fissures of the tooth and polymerizes, creating a strong bond with the tooth surface.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the mechanism of action of pit and fissure sealants. While some dental materials may be bound to the tooth surface through chemical bonds, pit and fissure sealants rely on micromechanical retention for their effectiveness.
**Option B:** This option is incorrect because it refers to a different type of dental material, not pit and fissure sealants. Dental adhesives are used to bond restorative materials to the tooth surface, but they do not provide the same level of protection as pit and fissure sealants.
**Option C:** This option is incorrect because it is too vague and does not accurately describe the mechanism of action of pit and fissure sealants.

**Clinical Pearl / High-Yield Fact**
One key consideration when applying pit and fissure sealants is the importance of proper surface preparation. The tooth surface must be clean and free of plaque and debris before the sealant is applied, in order to ensure a strong bond between the sealant and the tooth.

**Correct Answer:** D. Mechanical retention.