Analyse the effect of different investment techniques and pattern materials on surface roughness of raw Ni-Cr castings – An In Vitro study

AIMS: This study aimed to analyze the effect of different investment techniques and pattern materials on the surface roughness of raw castings from nickel-chromium alloy. SETTINGS AND DESIGN: This is an experimental in vitro study carried out in Bharati Vidyapeeth Dental College and Hospital, Sangli, Maharastra. MATERIALS AND METHODS: Sixty square-shaped wax patterns, measuring 10 mm × 10 mm × 2 mm, were divided into four groups. A phosphate-bonded investment material (Bellasun, Bego, Germany) was used to invest 15 samples of inlay wax and kept under normal atmospheric pressure and the remaining 15 wax patterns were invested under a pressure of 3 bars for 30 min, and then allowed to bench set for another 30 min. The same investing techniques were carried out for the remaining thirty samples made from pattern resin. STATISTICAL ANALYSIS USED: The surface roughness (μm) of the castings was measured by a profilometer. Student's “unpaired t-test” was used for the statistical analysis. RESULTS: Specimens that were invested at atmospheric pressure had significantly more surface roughness (μm) values than those invested under increased pressure (P < 0.01). CONCLUSIONS: Wax patterns exhibited the least surface roughness when invested under pressure and can be recommended as the material and technique of choice. In addition, resin patterns invested under increased pressure produced smoother casting surface than those invested at atmospheric pressure, and the difference is highly significant.