Effect of evaporation and mixing technique on die spacer thickness: A preliminary study

Statement of problem. Casting relief is required for proper seating of cast ings to allow for luting agent thickness. The application of die spacer to the die is the most common method of obtaining casting relief. Die spacer f ilm thicknesses that are outside the ideal range of 25 to 40 mum call cause clinical problems. Thickness can be affected by the separation of die spac er constituents, which may not be reconstituted by mixing, in the bottle an d by the evaporation of volatile components while the bottle is open. Purpose. The purpose of this study was to determine the effects of componen t evaporation and die spacer mixing technique on applied die spacer thickne ss. Material and methods. Bottles of Gold Tru-fit die spacer were left open for 0, 1, 4, 8, and 24 hours at 22 degreesC. Spacer solutions were shaken eith er by hand per the manufacturer's directions or on a dental vibrator for 1 minute. One even brush stroke of spacer was applied to clean glass slides. Three die spacer films were made for each combination of time and mixing te chnique. Eighteen thickness measurements per sample at various sites were r ecorded with profilometer tracings. Statistical differences were determined with a 2-way ANOVA. Results. Handshaking provided greater die spacer thickness, which increased with the time that the bottle was open. Vibration provided lower thickness with no statistical increase with time. Conclusion. Insufficient agitation caused lower film thickness. Excessive e vaporation caused higher film thickness.