scholarly journals Lost-wax or laser sintering? Findings on marginal and internal adaptation of metallic copings

2021 ◽  
Vol 10 (17) ◽  
pp. e162101724429
Author(s):  
Lucas José de Azevedo-Silva ◽  
Brunna Mota Ferrairo ◽  
Renato José Berro-Filho ◽  
Fernanda Ferruzzi Lima ◽  
José Henrique Rubo
Keyword(s):  
Laser Sintering ◽  
Internal Space ◽  
Marginal Adaptation ◽  
Direct Metal Laser Sintering ◽  
Cobalt Chromium ◽  
Replica Technique ◽  
Low Viscosity ◽  
Metal Ceramic ◽  
Internal Adaptation ◽  
Ceramic Crown

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.

scholarly journals CLINICAL EVALUATION OF COBALT-CHROMIUM-BASED FIXED DENTURES

2019 ◽  
Vol 15 (3) ◽  
pp. 146-151
Author(s):  
Арзу Керимова ◽  
Arzu Kerimova
Keyword(s):  
Survival Rate ◽  
Laser Sintering ◽  
High Wear Resistance ◽  
Marginal Adaptation ◽  
Direct Metal Laser Sintering ◽  
Cobalt Chromium ◽  
Proximal Caries ◽  
Direct Laser ◽  
Resistance To Deformation ◽  
Regional Adaptation

Subject. Ceramic-metal prostheses are distinguished by high wear resistance, resistance to deformation, and tight fit to the gums. However, there are relatively large differences in determining the success / survival of cobalt chromium based restorations. The article presents the results of a study of cobalt-chromium fixed dentures. Objectives — evaluate the effectiveness of cobalt-chromium fixed dentures made using the direct metal laser sintering (DMLS) technique. Material and methods. 32 patients (mean age 41.8 ± 2.46 years) were found to have 54 fixed cobalt-chromium fixed bridges made using direct laser sintering of metals. Dentures were evaluated between 6, 12, 24, 36 months according to G. Ryge criteria. The survival rate of restorations is calculated according to Kaplan-Meyer. Results. Assessment of fixed prostheses revealed the absence of criteria C and D in all 3 categories. A comparative analysis of prostheses showed no change in the period 6, 12, 24 months. After 36 months, chips that did not violate the function of the prosthesis were revealed in 5.5 % of cases, visible signs of a cleft in the category of “marginal adaptation” in 1.8 % of cases, edge discoloration of the surface in 3.7 % of cases. Radiographically, 1 patient showed signs of incipient proximal caries and periapical changes, respectively. During the study period of 6-24 months. survival rate was 1.0. The survival of the restoration over a 3-year period was 88.9 %. Conclusion. The frequency of cleavage was 5.5 %, which is comparable to the usual performance of ceramic-metal restorations. The visible signs of a cleft in the regional adaptation was 1.8 %, and the regional color mismatch was 3.7 %. 1.8 % of restoration was detected. Signs of incipient proximal caries were 1.8 %, periapical changes — 1.8 %. Survival was 88.9 %.

scholarly journals Effect of Digital Technologies on the Marginal Accuracy of Conventional and Cantilever Co–Cr Posterior-Fixed Partial Dentures Frameworks

2021 ◽  
Vol 11 (7) ◽  
pp. 2988
Author(s):  
Celia Tobar ◽  
Verónica Rodríguez ◽  
Carlos Lopez-Suarez ◽  
Jesús Peláez ◽  
Jorge Cortés-Bretón Brinckmann ◽  
...  
Keyword(s):  
Digital Technologies ◽  
Hard Metal ◽  
Direct Metal Laser Sintering ◽  
Cobalt Chromium ◽  
Metal Ceramic ◽  
Marginal Discrepancy ◽  
Soft Metal ◽  
Manufacturing Techniques ◽  
Ceramic Restorations ◽  
To Receive

The introduction of new digital technologies represents an important advance to fabricate metal–ceramic restorations. However, few studies have evaluated the influence of these technologies on the fit of the restorations. The aim of this study was to evaluate the effect of different manufacturing techniques and pontic design on the vertical marginal fit of cobalt–-chromium (Co–Cr) posterior fixed partial dentures (FPDs) frameworks. Methods: Eighty stainless-steel dies were prepared to receive 3-unit FPDs frameworks with intermediate pontic (n = 40) and cantilever pontic (n = 40). Within each design, the specimens were randomly divided into four groups (n = 10 each) depending on the manufacturing technique: casting (CM), direct metal laser sintering (LS), soft metal milling (SM), and hard metal milling (HM). The frameworks were luted, and the vertical marginal discrepancy was assessed. Data analysis was made using Kruskal–Wallis and Mann–Whitney U tests (α = 0.05). Results: The vertical marginal discrepancy values of all FPDs were below 50 μm. The HM frameworks obtained the lowest misfit values in both designs. However, no differences were found among intermediate pontic groups or cantilevered groups. Likewise, when differences in a marginal discrepancy between both framework designs were analyzed, no differences were observed. Conclusions: The analyzed digital technologies demonstrated high precision of fit on Co–Cr frameworks and on both pontic designs.

The Effect of Cooling Times on the Bonding Between Porcelain and Metal Alloys Fabricated by Different Techniques: In Vitro Study

2021 ◽  
pp. 232020682110371
Author(s):  
Emine Ünal ◽  
Faik Tugut
Keyword(s):  
Bond Strength ◽  
Shear Bond Strength ◽  
Laser Sintering ◽  
Cobalt Chromium ◽  
Slow Cooling ◽  
Ceramic Samples ◽  
Metal Framework ◽  
Metal Ceramic ◽  
Bond Strengths ◽  
Fast Cooling

Aim: The aim of this study was to evaluate the effect of different cooling times on shear bond strength between cobalt–chromium metal frameworks fabricated by different techniques and veneering porcelain. Materials and Methods: One hundred twenty cobalt–chromium metal ceramic samples were obtained by three different techniques (casting, milling, and laser sintering). During the porcelain firing, fast and slow cooling protocols were applied. Ten specimens from each group were determined for all groups. The shear bond strength of the metal ceramic samples was measured by a universal testing machine with a constant crosshead speed of 0.5 mm/min. One sample from each group was evaluated by the scanning electron microscopy analysis in terms of surface change and fracture morphology. Variance analysis and Tukey test were used to analyze statistically significant differences between groups. Results: It was seen that the difference between the bond strengths of the metal frameworks obtained by different techniques was statistically significant ( P < .05). All groups except for difference between the bond strengths of all the frameworks metal groups with G-Ceram porcelain were statistically significant ( P < .05). The best bond strengths that were statistically significant were fast cooling G-Ceram (19.65 ± 2.65 MPa) with metal frameworks fabricated by laser sintering, fast cooling with metal framework fabricated by milling Noritake (19.17 ± 2.91 MPa), and the metal framework fabricated by casting was found to be slow cooling Noritake (12.99 ± 2.08 MPa) were seen. Conclusion: The porcelain cooling times had significant effect on the shear bond strength of porcelain to casting, milling and laser sintering alloys.

scholarly journals Comparison of Marginal and Internal Adaptation in Endocrowns Milled from Translucent Zirconia and Zirconium Lithium Silicate

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Amirhesam Amini ◽  
Somayeh Zeighami ◽  
Safoura Ghodsi
Keyword(s):  
Intraclass Correlation ◽  
Acrylic Resin ◽  
Lithium Silicate ◽  
Marginal Adaptation ◽  
Negative Effects ◽  
Marginal Gap ◽  
Replica Technique ◽  
Direct View ◽  
Cad Cam ◽  
Internal Adaptation

Purpose. This study aimed to compare marginal and internal adaptation in endocrowns made from translucent zirconia and zirconium lithium silicate using CAD-CAM technology. Materials and Methods. Twenty-eight freshly extracted upper molars were mounted in acrylic resin and underwent root canal therapy and endocrown preparation up to 2 mm above the cementoenamel junction. Endocrowns were CAD-CAM milled from zirconium lithium silicate (ZLS) and translucent zirconia (Zr). Internal and marginal adaptation was assessed by the replica technique before cementation. Marginal adaptation was evaluated by a stereomicroscope (×32) before and after cementation and also after thermomechanical aging. Results. The ZLS group showed significantly higher internal adaptation compared to the Zr group ( P  = 0.028), while the marginal adaptation differences, at different times with different methods, were not statistically significant ( P  > 0.05). Axiomarginal angle had the highest and axiopulpal angle showed the lowest adaptation in both groups. The cementation process and thermomechanical aging increased the marginal gap in both groups significantly ( P  < 0.001). The marginal gap assessed by the replica technique before cementation was 7.11 µm higher than direct view under a stereomicroscope with intraclass correlation coefficient of 0.797. Conclusion. Zirconia seems to be an acceptable material for endocrown with comparable internal and marginal adaptation to ZLS. Cementation and thermomechanical aging had significantly negative effects on marginal gap. The marginal gap assessed by the replica technique was higher than direct view under the stereomicroscope technique.

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