Hydrocolloid Techniques in the Fabrication of Inlays by the Indirect Method: Update on Alternative Delivery Systems

Abstract

Clinical success with the hydrocolloids depends on careful control of the many manipulative variables. With intelligent manipulation, the exactness of duplication of cavities allows multiple restorations to be coordinated one with the other on hydrocal models without the necessity of checking or fitting in the mouth. The main factors are: 1. Reversible hydrocolloid must be boiled for a minimum of 10 minutes and stored at a temperature of 145° or 155° F. 2. Various tempering procedures can be employed, but the degree of gelation and the working consistency will depend on batch composition, tempering temperature and time. 3. The cavity margin must be exposed, since neither agar nor alginate hydrocolloids will displace tissue or heavy fluids. Retraction of tissue should be by means of conservative methods in order to minimize trauma. 4. The impression must be held in the patient’s mouth for a minimum of 5 minutes and removed with a sharp thrust in one direction parallel to the long axis of the tooth. 5. For indirect techniques, most alginates require a higher water-powder ratio and the use of ice water for proper control of the setting time. 6. Either premature removal or a prolonged period in the mouth will influence the accuracy of alginate impressions. 7. Both agar and alginate impressions must be poured within 15 minutes. 8. The water-powder ratio, the amount of vibration during pouring and the length of time before removal of the die will influence the character of the stone surface. 9. The working dies show no discrepancies when the fractured parts are trimmed and the metal strips are not too thick or pushed too far into the impression.