National Dental Assisting Examining Board (NDAEB) Practice Exam

Why should the acid etchant be applied for a shorter time on dentin compared to enamel during cavity preparation for composite resin restoration?

1. To avoid opening the dentinal tubules too much

2. To enhance the bond strength

3. To prevent patient discomfort

4. To save time in the procedure

The correct answer is: To avoid opening the dentinal tubules too much

The application of acid etchant for a shorter duration on dentin compared to enamel is primarily to avoid excessive opening of the dentinal tubules. Dentin is more porous than enamel and contains microscopic channels known as dentinal tubules that lead to the pulp of the tooth. When acid etchant is applied, it removes the smear layer and opens these tubules to facilitate bonding with the composite resin. If the etchant is left on the dentin for too long, it can over-etch the surface, leading to an excessive number of open tubules. This can increase sensitivity for the patient and may compromise the bond strength because it can disrupt the delicate adhesion process that takes place between the dentin and the adhesive materials. Thus, controlling the etching time on dentin is crucial for maintaining tubule integrity and achieving an effective bond without causing unnecessary pulp irritation or sensitivity issues. While enhancing bond strength is important, the key aspect here is the delicate balance in managing the exposure of dentinal tubules to the etchant. Similarly, patient comfort and the efficiency of the procedure are considerations, but they are secondary to maintaining the structural integrity of the dentin during the etching process.