Abstract
Marginal and internal adaptation are parameters of crucial importance to the success of prosthetic crowns. Automatized process creates an expectative of superior or equivalent results compared to restorations manufactured by conventional lost-wax technique. The purpose of this study was to evaluate the marginal adaptation and internal adaptation (cement space) of metal-ceramic crown copings produced by lost-wax (LW) and direct metal laser sintering (DMLS) techniques. An artificial lower first molar was prepared for a full crown, duplicated in plaster and scanned. Twenty metal-ceramic crown copings were fabricated in cobalt-chromium by the two techniques (n=10). The copings were filled with low viscosity silicone and seated on the prepared tooth, resulting in a replica of the internal space. The pellicle formed was embedded in heavy body silicone, sectioned and captured by means of a stereomicroscope at 50x magnification, according to replica technique (RT). Shapiro-Wilk test followed by Holm-Sidak test were used for statistical analysis (α=.05). Marginal adaptation presented no difference between LW (101.5 ± 41.6) and DMLS (86.3 ± 39.9) groups (p=0.24). Conventional LW technique showed significantly lower occlusal (p<0.008) and axial spaces (p<0.03). Measurements of all regions showed numerically larger adaptation values than that defined during design for DMLS group. Both the LW technique and the DMLS technique are within the clinically acceptable.
Highlights
For over 40 years, metal-ceramic crowns remain the gold standard of prosthetic dentistry (Pjetursson et al 2007) and are widely used despite the metal-free trend
Direct metal laser sintering (DMLS) technique is responsible for producing metal prosthetic parts in automatized additive method, mostly using cobalt-chromium (CoCr) alloy powder that are sintered by a laser (Santos et al 2019)
Considered a simple technique, currently studies have shown that the results of this technique are similar to those found in more advanced and expensive techniques (Hamza et al 2013; Mai et al 2017). The purpose of this in vitro study was to elucidate the questionable association of automation with precision, comparing the marginal adaptation and internal fit of metal-ceramic crown copings produced by lost-wax technique (LW) and DMLS, using replica technique
Summary
For over 40 years, metal-ceramic crowns remain the gold standard of prosthetic dentistry (Pjetursson et al 2007) and are widely used despite the metal-free trend. New methods have been developed to improve their manufacture technique and minimalize those complications. Computer-aided design (CAD) and manufacturing (CAM) was developed in order to provide restorations with higher resistance, aesthetic and accuracy using a cheapest, fastest and easiest method (Belli et al 2017) by additive or subtractive methods (Quante et al, 2008). Direct metal laser sintering (DMLS) technique is responsible for producing metal prosthetic parts in automatized additive method, mostly using cobalt-chromium (CoCr) alloy powder that are sintered by a laser (Santos et al 2019). The milling process is a method where design-guided drills subtractively carve the material, e.g. dental ceramic, resin, metal or wax, which will be conventionally cast later (Park et al 2017; Hamza et al 2013)
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