HESI General Chairside Assisting Practice Exam

Which cement is no longer visible when it becomes stringy or begins to cobweb?

1. Glass ionomer

2. Zinc phosphate

3. Zinc polycarboxylate

4. Resin cements

The correct answer is: Zinc polycarboxylate

The cement that becomes no longer visible when it turns stringy or begins to cobweb is zinc polycarboxylate. This material has a unique property in its setting phase, where it exhibits a characteristic viscosity and consistency that allows it to form a stringy, cobweb-like appearance as it transitions from a workable state to a final set. Zinc polycarboxylate is known for its excellent adhesion to both dentin and enamel, which contributes to its effectiveness in dental procedures. When it sets and starts to show this stringy nature, it indicates its transition from a pliable material to a fully set state, effectively bonding to the tooth structure and becoming secure in place. At this point, the cement is often considered to be well-established, and its visibility diminishes as it integrates with the surrounding dental anatomy. In contrast, glass ionomer, zinc phosphate, and resin cements each have differing properties and setting behaviors that do not typically include this specific stringy or cobweb-like transition. They may remain more visibly intact or present specific characteristics during their setting processes that don’t align with the unique transition seen with zinc polycarboxylate.