Comparison of internal fit of metal copings fabricated with laser sintering technique and lostwax technique, pre and post firing: An In Vitro study

Mohammed, A (2014) Comparison of internal fit of metal copings fabricated with laser sintering technique and lostwax technique, pre and post firing: An In Vitro study. Masters thesis, K.S.R. Institute of Dental Science and Research, Tiruchengode.

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Abstract

An in vitro study was conducted to compare the marginal and internal gap of Co-Cr copings fabricated by two methods, (conventional lost wax technique and Direct laser sintering). A total of 30 test samples were fabricated using Co-Cr alloys in two different techniques. All the samples were made by making an impression from a stainless steel master model.15 cast copings were fabricated from patterns obtained by inlay-casting wax for conventional lost wax technique. 15 copings were obtained from 3D printing for fabricating DMLS copings. Patterns made from inlay wax were invested, burnout and casting was done by traditional method with Co-Cr alloy to obtain cast copings. Cast copings were divested, sandblasted, steam cleaned and finished. Copings prepared from DLMS technique were also sandblasted and steam cleaned. The entire copings were then cemented on the stainless steel master model using silicone pressure indicating paste to simulate a coping cemented in the oral condition. The test samples were removed from the master model, and the silicon coping was separated from the inner surface of test samples. The silicon copings thus obtained were evaluated for internal gap using an electronic analytical weighing machine (Schimadzu, Japan). All the measurements were determined in micro grams (μg). Later the test samples were cemented onto their respective dies with GIC type I luting cement (GC, FUJI Japan). These cemented specimens were sectioned mesio-distally. The marginal gap was measured in 2 predetermined reference points using a Scanning electron microscope (Sigma V, Carl Zeiss, Munich, Germany), All the measurements were determined in micrometers (μm). The manufacturing process influences marginal and internal accuracy of the dental restorations. An increase in marginal gap exposes the cement to the oral environment thereby affecting the health of the remaining supporting structures and increase in internal gap can affect the restoration. Hence both are important parameters to be considered for longevity of a restoration. Results of this study showed the marginal gap of Co-Cr copings obtained by two different fabrication techniques were within the clinically acceptable range (10-160μm). The internal gap of Co-Cr copings were obtained from two different techniques were also within the clinically acceptable range (81-136μm) In this study a new fabricating procedure (DMLS) was used for the fabrication of Co-Cr copings. The marginal gap of the Co-Cr coping obtained by this technique was (32μm) least compared to the lost wax technique (112μm). Though results obtained in this in vitro study fell within the clinically acceptable range, the DMLS technique had an advantage over the lost wax technique, as it exhibited minimal gap in the marginal region, an area of chief concern. In terms of marginal fit and internal fit, both the conventional casting technique and DMLS technique have yielded results within clinically acceptable range but the difficulties encountered during conventional casting procedures are being completely eliminated in DMLS technique which seems to yield promising results. The scope of further studies regarding the mechanical properties and biocompatibility of laser sintered Co-Cr would be of great use for their acceptance in dental laboratory and practice. CONCLUSION: This in-vitro study was conducted to compare pre and post-firing of the internal fit of Co-Cr coping fabricated by conventional lost wax technique (LW) and direct metal laser sintering (DMLS) technique. 1. The internal gap of 15 pre-firing Co-Cr copings of the lost wax (G1-LW) showed a mean value of 34μg. 2. The internal gap of 15 post-firing Co-Cr copings of lost wax (G1-LW) showed a mean value of 37μg. 3. The internal gap of 15 pre-firing Co-Cr copings of the DMLS (G2-DMLS) showed a mean value of 23μg. 4. The internal gap of 15 post-firing Co-Cr copings of DMLS (G2-DMLS) showed a mean value of 26μg. 5. The marginal gap of the 15 Co-Cr copings obtained from Lost-wax (G1-LW) technique showed a mean value of 109μm. 6. The marginal gap of the 15 Co-Cr copings obtained from DMLS (G2-DMLS) technique showed a mean value of 46μm. From the above data the study concluded that the mean internal gap between (G1-LW) and (G2-DMLS) for pre and post firing metal ceramic copings show statistically significant difference. Also it was found that the mean marginal gap between (G1-LW) and (G2-DMLS) for post firing metal ceramic copings show very high statistically significant difference. Conventional casting technique and DMLS have yielded results within clinically acceptable range, but compared to conventional casting methods, the technique sensitive procedures are being completely eliminated in the DMLS technique.

Item Type: Thesis (Masters)
Uncontrolled Keywords: internal fit ; metal copings fabricated ; laser sintering technique ; lostwax technique ; pre and post firing.
Subjects: DENTAL > Prosthodontics and Crown and Bridge
Depositing User: Subramani R
Date Deposited: 28 Oct 2018 16:51
Last Modified: 28 Oct 2018 16:51
URI: http://repository-tnmgrmu.ac.in/id/eprint/9999

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