CLINICAL DISCRIMINATION OF PORCELAIN Indeed, the esthetic result may be superior to the original glazed surface. The decrease in visual discrimination between the two test surfaces evidenced after additional glazing procedures may be attributed to structural changes experienced by the porcelain. 2. Klausner LH, Cartwright CB, Charheneau G’P. Polished versus auto- glazed porcelain surfaces. J PROSTHET DENT 1982;47:157-62. 3. Newitter DA, Schlissel ER, WoltTMS. An evaluation of adjustment and uostadiustment finishing techniques on the surface of porcelain-hond- ed-to-metal crowns. J P~OSTHJ& DENT 1982;483388-95. 4. Bessing C, Wiktorsson A. Comparison of two different methods of pol- ishing porcelain. Stand J Dent Res 1983;91:482-7. REFERENCES Reprint requests to: DR. JANE D. BREWER SCHO~~L OF DENTAL. MEDICINE SUNY AT BUFFALO BUFFALO, NY 14214 1. Sulik WD, Plekavich EJ. Surface finishing of dental porcelain. J PROS- THET DENT 1981:46:217-21. A controlled putty-wash impression technique Barry Marshak, B.D.S.,* David Assif, D.M.D.,** and Raphael Pilo, D.M.D.* Tel Aviv University, Sackler Faculty of Medicine, Tel Aviv, Israel A precise impression is imperative for the construction of an accurately fitting indirect cast restoration. The putty-wash technique is commonly used in making impressions with silicone elastomers. Errors in manipulation may lead to inaccu- rate impressions. A technique is presented ensuring exact reseating of the putty impression tray and creation of a uniform wash space, which are essential for accurate results. (J PROSTAET DENT 1990;64:635-6.) T he putty-wash technique is commonly used in 4. Some manufacturers provide a polyethelene spacer to making impressions with silicone elastomers. This consists be placed over the putty for making the putty impression. of polymerizing a low-viscosity elastomer (light-body or This procedure has the major drawbacks of (1) no land- wash) against a high-viscosity elastomer (putty).’ The marks, guiding planes, or posterior stops left in the putty putty, used in a perforated metal stock tray, simulates a impression, making accurate replacement of the tray dur- custom-made tray. Notwithstanding the properties of poly- ing the wash stage difficult, and (2) an inaccurate or arbi- siloxane materials, the following errors in manipulation trarily repositioned tray that cannot achieve a uniform may lead to an inaccurate impression. wash space. Errors leading to inaccurate impression TECHNIQUE 1. An excess bulk of wash material can result in dimen- sional changes proportional to the thickness of the mate- rial during setting. A consistent layer of 2 mm has been recommended as the optimal thickness for the wash material.2-5 The following technique is suggested to overcome the problems of errors in manipulation: 2. Undercuts or projections into the putty affect the ac- curacy of the impression.6 3. Inaccurately seating the putty tray containing the wash material may lead to an excess bulk of wash material around the abutment teeth, resulting in wash material be- ing forced away from the abutment tooth because of over- seating and a nonuniform layer of wash left around the abutment. 1. The putty impression is made with resin provisional restorations in place on the prepared teeth and allowed to set. The provisionals act as occlusal stops for seating of the impression tray. If the restoration is a fixed partial denture, individual resin restorations made on a stone cast are used so that a uniform impression is made of the edentulous space. 2. When the impression is removed, the provisional res- torations are detached from the set putty. A wash space, equivalent to the dimensions of the provisional restoration, will be created in the putty surrounding the prepared tooth. When design of the finish line is such that an adequate bulk of wash material cannot be achieved because of the thin margins of the provisional restoration, a strip of putty cor- responding to the finish line should be cut away. *In&ructor, Department of Prosthodontics. **Coordinator, Department of Prosthodontics; Senior Clinical Lecturer, Department of Prosthodontics. 10/l/22126 3. To enable accurate reseating of the putty impression and venting away excesswash material, all undercuts, pro- THE JOURNAL OF PROSTHETIC DENTISTRY 635