Evaluation of marginal discrepancy in metal frameworks fabricated by sintering-based computer-aided manufacturing methods

Abstract

The aim of this in vitro study was to evaluate the effect of sintering procedures on marginal discrepancies of fixed partial metal frameworks fabricated using different sintering-based computer-aided design and computer/aided manufacturing (CAD/CAM) techniques. MATERIALS AND METHODS. Forty resin die models of prepared premolar and molar abutment teeth were fabricated using a three-dimensional (3D) printer and divided into four groups (n = 10) according to the fabrication method of metal frameworks used: HM (via hard milling), SM (via soft metal milling), L25 (via direct metal laser melting [DMLM] with a 25 µm layer thickness), and L50 (via direct DMLM with a 50 µm layer thickness). After the metal frameworks were fabricated and cemented, five vertical marginal discrepancy measurements were recorded in each site (i.e., buccal, facing the pontic, lingual, and facing away from the pontic) of both abutment teeth under a stereomicroscope (×40). Data were statistically analyzed at a significance level of 0.05. RESULTS. No statistically significant differences (P>.05) were found among the four axial sites of metal frameworks fabricated by sintering-based CAD/CAM techniques. The HM and L25 groups showed significantly (P<.001) lower marginal discrepancy values than the SM and L50 groups. CONCLUSION. Marginal discrepancy in the sites facing the pontic was not influenced by the type of sintering procedure. All fabrication methods exhibited clinically acceptable results in terms of marginal discrepancies.

Comparison of the Marginal and Internal Discrepancy of Metal-Ceramic Restorations Produced by Milling for Soft Metal, Direct Metal Laser Sintering and Casting Methods: An In Vitro Study

“…9 An excellent marginal adaptation is one of the most significant factors for long-term success. 3,[10][11][12][13][14] McLean and von Fraunhofer 15 reported that a gap of 120 µm is acceptable and marginal discrepancies (MD) of less than 80 µm are too difficult to detect in clinical situations. However, there are studies in the literature reporting that the maximum MD of 100 µm 16 and even 50 µm 17 is ideal for the success and longevity of indirect restorations.…”

“…19 The direct vision technique is one of the most widely used methods. 3,12,[19][20][21] The traditional way of fabricating metal frameworks, the lost wax casting (LW), is a complex and time-consuming technique. However, computer-aided design/computer-aided manufacturing (CAD/CAM) has gained popularity in dental practice.…”

“…Although the DMLS system has advantages that can be listed such as easy manufacturing of complex shapes, elimination of wasted material, less labor time, and low cost, the devices are very expensive and require high technical precision, which has restricted the production only to the large-scale CAD/CAM centers. 5,7,12,24 Subtractive CAD/CAM methods fabricate prostheses by milling block-shaped materials using diamond rotary instruments. Recently, milling for soft metal (MS) has been introduced to fabricate metal frameworks.…”

“…Although the DMLS system has advantages that can be listed such as easy manufacturing of complex shapes, elimination of wasted material, less labor time, and low cost, the devices are very expensive and require high technical precision, which has restricted the production only to the large-scale CAD/CAM centers. 5,7,12,24…”

“…However, MS possesses several advantages like reducing stresses on the milling device and the burrs used and decreasing the amount of time spent on milling. 12,25,26 What is more, the MS can be milled with those milling devices used for milling all ceramic and Zr blocks including the chairside milling devices without a need for large CAD/CAM machines. Therefore, the preference for using MS is gradually increasing and different soft metal blocks have been introduced into the market.…”