Marginal accuracy of nickel chromium copings fabricated by conventional and accelerated casting procedures, produced with ringless and metal ring investment procedures: A comparative in vitro study

Abstract

Background:Conventional investing and casting techniques are time-consuming and usually requires 2–4 h for completion. Accelerated nonstandard, casting techniques have been reported to achieve similar quality results in significantly less time, namely, in 30–40 min. During casting, it is essential to achieve compensation for the shrinkage of solidifying alloy by investment expansion. The metal casting ring restricts the thermal expansion of investment because the thermal expansion of the ring is lesser than that of the investment. The use of casting ring was challenged with the introduction of the ringless technique.Materials and Methods:A total of 40 test samples of nickel chromium (Ni-Cr) cast copings were obtained from the patterns fabricated using inlay casting wax. The 20 wax patterns were invested using metal ring and 20 wax patterns were invested using the ringless investment system. Of both the groups, 10 samples underwent conventional casting, and the other 10 underwent accelerated casting. The patterns were casted using the induction casting technique. All the test samples of cast copings were evaluated for vertical marginal gaps at four points on the die employing a stereo optical microscope.Results:The vertical marginal discrepancy data obtained were tabulated. Mean and standard deviations were obtained. Vertical discrepancies were analyzed using analysis of variance and Tukey honestly significantly different. The data obtained were found to be very highly significant (P < 0.001). Mean vertical gap was the maximum for Group II (53.64 μm) followed by Group IV (47.62 μm), Group I (44.83 μm) and Group III (35.35 μm).Conclusion:The Ni-Cr cast copings fabricated with the conventional casting using ringless investment system showed significantly better marginal fit than that of cast copings fabricated from conventional and accelerated casting with metal ring investment and accelerated casting using ringless investment since those copings had shown the least vertical marginal discrepancies among the four methods evaluated in this study.

Microcomputed tomography a noninvasive method to evaluate the fit of a restoration as compared to conventional replica technique

“…[ 4 12 ] This master die was dipped in an electrically controlled wax bath at a recommended temperature of 60°–110°C. [ 13 ] The wax pattern was modified using an electric wax shaping instrument and GEO medium hard Crowax (Renfert, Germany) to get 0.5 mm thickness of the wax pattern coping which was confirmed using a wax gauge[ 5 14 15 ] [ Figure 2 ]. Twenty wax pattern copings were fabricated and all were invested immediately to avoid any distortion.…”

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

“…The accuracy of the marginal fit of restoration is essential for its longevity and a healthy periodontium. [ 32 ] Surface roughness and accurate fitting are important criteria for clinical longevity of fixed dental prosthesis. Rough surface can indirectly result in marginal gap width and ultimately to microleakage.…”

The effect of casting ring liner length and prewetting on the marginal adaptation and dimensional accuracy of full crown castings

“…Dental laboratory techniques are upgraded constantly to fabricate accurate casting from last wax technique. [ 8 9 ] A precise cervical margin adaptation is critical for biological, aesthetic, and physical requirement of the restorations. Open margins are known to accentuate periodontal diseases and secondary caries.…”