Evaluation of marginal/internal fit of chrome-cobalt crowns: Direct laser metal sintering versus computer-aided design and computer-aided manufacturing

Abstract

DMLS was best fitting fabrication techniques for single crown based on the results.The best fit was found in marginal; the larger gap was found in occlusal.All groups were within the clinically acceptable misfit range.

Influence of Cobalt Chromium Framework Fabrication Techniques on Marginal Accuracy and Fracture Behavior of Implant-Supported Metal Ceramic Bridges

“…(14,27) In this research, to minimize variations inherent to any manual process, the wax patterns for frameworks fabricated by the casting procedure were constructed by the CAD/CAM technology similar to other researches how found that Co-Cr frameworks obtained from milled wax patterns had better marginal and internal fit than those obtained from manually fabricated wax patterns. (7,10) Misfiting implant cemented restorations can lead to biomechanical failure, components fracture or even bone loss. (2,16) Studies evaluating the marginal adaptation of fixed restorations on teeth or implants suggest different methods of measuring marginal discrepancy between the restoration margins and abutment tooth or implant abutment.…”

“…Of these, the direct microscopic, sectioning and replica methods were mostly preferred. (5,7,(10)(11)(12)(13)17,19,21) The direct microscopic method is easier, faster, and can be easily repeated, although the precision of the measurements is lower. Conversely, the sectioning method demonstrates the marginal discrepancy more clearly.…”

“…(17) Few contradicting results were found in the literature concerning the marginal and internal adaptation of Co-Cr frameworks fabricated by the recent techniques, two studies found that direct laser metal sintering group showed the best fit among the tested groups (milling and casting). (7,10) In contrast, Nesse et al (5) reported that the milled Co-Cr group showed the best overall fit followed by the cast one, while the selective laser melting method had the poorest fit. Additionally, Kocaağaoğlu et al (11) reported that metal ceramic restorations produced with hard and soft milling techniques exhibited better marginal adaptations than those produced by laser sintering or casting.…”

“…(3)(4)(5) The CAD/CAM technologies have revolutionized the Co-Cr restorations production either by subtractive or additive manufacturing. (5)(6)(7)(8)(9)(10)(11) CAD/CAM hard milling is one of the subtractive processes for producing Co-Cr restorations (5)(6)(7)(9)(10)(11) , the formation of casting-induced flaws and porosities are minimized by using Co-Cr alloy blanks manufactured under standardized industrial conditions. However, increased tool and machine wear caused by the high rigidity of the "solid" blank and high maintenance costs are the main disadvantages of the technique .…”

“…Additive manufacturing assisted by CAD/CAM technology as selective laser melting (SLM) is an alternative method for producing Co-Cr restorations directly from a three-dimensional CAD model by fusing fine layers of metal powder using a highpower focused laser beam. (5)(6)(7)10,11) However, this method currently requires very expensive equipment and is, thus, restricted to large CAD/ CAM centers in the dental industry. Another recent approach in the production of Co-Cr dental restorations is dry milling of "soft" Co-Cr blanks, in which the alloy powder is finely distributed in a the lowest statistically insignificant vertical marginal gap distance mean value before porcelain application (24.63±4.27µ), while those with cast frameworks recorded the highest statistically insignificant vertical marginal gap distance mean value after porcelain application (25.21±7.08µ).…”