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

STATEMENT OF PROBLEM: Casting relief is required for proper seating of castings 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 film thicknesses that are outside the ideal range of 25 to 40 microm can cause clinical problems. Thickness can be affected by the separation of die spacer constituents, which may not be reconstituted by mixing, in the bottle and by the evaporation of volatile components while the bottle is open. PURPOSE: The purpose of this study was to determine the effects of component evaporation and die spacer mixing technique on applied die spacer thickness. MATERIAL AND METHODS: Bottles of Gold Tru-fit die spacer were left open for 0, 1, 4, 8, and 24 hours at 22 degrees C. Spacer solutions were shaken either 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 technique. Eighteen thickness measurements per sample at various sites were recorded 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 evaporation caused higher film thickness.