scholarly journals Marginal and internal fit of CAD CAM system: A literature review

2019 ◽  
Vol 31 ◽  
pp. S21
Author(s):  
Ahad Al-shalan ◽  
Arwa A-lmutair ◽  
Diaa Aldin ◽  
Shahad Bin-Abbas ◽  
Mlaa Al-shmlani ◽  
...  
Keyword(s):  
Literature Review ◽  
System A ◽  
Cad Cam ◽  
Internal Fit

scholarly journals Effect of Luting Cement and Convergence Angle of the Preparation on the Internal Fit of Zirconia Restorations

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7858
Author(s):  
Andrés Sánchez-Monescillo ◽  
Carlos González-Serrano ◽  
José González-Serrano ◽  
João Malta Barbosa ◽  
Carlos López-Suárez ◽  
...  
Keyword(s):  
Glass Ionomer Cement ◽  
Resin Cement ◽  
Convergence Angle ◽  
System A ◽  
Luting Agents ◽  
Luting Cement ◽  
Cad Cam ◽  
And Coping ◽  
Internal Fit ◽  
Preparation Design

The objective was to evaluate the effect of luting agents and the preparation design on the internal fit of zirconia restorations. Sixty dies were prepared and divided in occlusal convergence angle of 6° (OC6) and 12° (OC12). CAD/CAM zirconia copings were fabricated (Lava All-Ceramic System). A zinc phosphate cement (ZPC); a glass ionomer cement (GIC); and a resin cement (RC) were studied. Specimens were sectioned and coping/die discrepancies were evaluated through Stereoscopic Microscopy. A closer fit was observed in OC12 when compared to OC6 (p < 0.001). For OC6 no significant differences were observed in between ZPC, GIC, and RC (p > 0.05). For OC12, a significantly closer fit was recorded on the ZPC subgroup when compared to the GIC subgroup (p < 0.001). Preparations of 12 degrees demonstrated a closer internal fit when compared to 6 degrees. Preparations of 12 degrees achieved better internal fit values with ZPC (Fortex) followed by RC (RelyX Unicem), and GIC (Ketac Cem). No differences were found when comparing different luting agents over 6° degrees preparations.

scholarly journals Marginal and Internal Precision of Zirconia Four-Unit Fixed Partial Denture Frameworks Produced Using Four Milling Systems

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2663
Author(s):  
Karl Martin Lehmann ◽  
Michael Weyhrauch ◽  
Monika Bjelepavlovic ◽  
Herbert Scheller ◽  
Henning Staedt ◽  
...  
Keyword(s):  
Marginal Gap ◽  
Partial Denture ◽  
System A ◽  
Fixed Partial Denture ◽  
Bonferroni Adjustment ◽  
Cad Cam ◽  
Level Of Significance ◽  
Internal Fit ◽  
Cam Systems ◽  
Marginal Region

Background: CAD/CAM systems enable the production of fixed partial dentures with small and reproducible internal and marginal gaps. Purpose: The purpose of this study was to evaluate the reproducibility of the marginal and internal adaptations of four-unit fixed partial denture frameworks produced using four CAD/CAM systems. Materials and Methods: Prepared dies of a master model that simulated the loss of the first left molar were measured. Fifteen frameworks were manufactured using four CAD/CAM systems (A–D). The internal fit was determined by the replica technique, and the marginal gap was determined by microscopy. ANOVA was carried out to detect significant differences, and the Bonferroni adjustment was performed. The global level of significance was set at 5%. Results: The mean gap size ranged from 84 to 132 µm (SD 43–71 µm). The CAD/CAM systems showed significant variance (p < 0.001), and system A (VHF) showed the smallest gaps. The smallest gaps for each system were in the molar part and in the marginal region of the frameworks (p < 0.001). Conclusions: The CAD/CAM systems showed significantly different gap sizes, particularly between premolars and molars and among the marginal, axial and occlusal regions. All of the systems are suitable for clinical application.

scholarly journals Librarians’ Perceptions of the Challenges for Researchers in Rwanda and the Potential of Open Scholarship

Libri ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Andrew Cox ◽  
Pamela Abbott
Keyword(s):  
Literature Review ◽  
Reform Movement ◽  
Limited Access ◽  
System A ◽  
Scholarly Communications ◽  
Major Reform ◽  
Global North ◽  
Communications System ◽  
Poor Infrastructure

Abstract Open scholarship is a major reform movement within research. This paper seeks to understand how open scholarship might address the challenges faced by research in Africa, through a study based on a participatory collaborative workshop to create a partnership with librarians in Rwanda. The literature review identifies three broad perspectives on the apparent under-performance of Rwandan research: one locating the issue in the unequal scholarly communications system, a second pointing to a country deficit and a third blaming cognitive injustices. The Rwandan librarians see researchers as challenged through the pressures on them to publish, the costs of research, poor infrastructure, lack of skills and limited access to literature. Collectively these challenges constitute a critical barrier to research. These limits fit largely the country deficit perspective. Open scholarship as conceived in the Global North is only a small part of the answer to the challenges faced by Rwandan scholars. To promote equity, notions of open scholarship need to take into account the conditions under which research is conducted in less privileged contexts such as Rwanda.

scholarly journals Marginal and Internal Fit of Ceramic Prostheses Fabricated from Different Chairside CAD/CAM Systems: An In Vitro Study

2021 ◽  
Vol 11 (2) ◽  
pp. 857
Author(s):  
Keunbada Son ◽  
Kyu-Bok Lee
Keyword(s):  
Computer Aided Design ◽  
In Vitro Study ◽  
Vitro Study ◽  
Marginal Gap ◽  
Significant Difference ◽  
Cad Cam ◽  
Ceramic Crowns ◽  
Internal Fit ◽  
Cam Systems

The purpose of this in vitro study was to evaluate marginal and internal fits of ceramic crowns fabricated with chairside computer-aided design and manufacturing (CAD/CAM) systems. An experimental model based on ISO 12836:2015 was digitally scanned with different intraoral scanners (Omnicam (CEREC), EZIS PO (DDS), and CS3500 (Carestream)). Ceramic crowns were fabricated using the CAD/CAM process recommended by each system (CEREC, EZIS, and Carestream systems; N = 15). The 3-dimensional (3D) marginal and internal fit of each ceramic crown was measured using a 3D inspection software (Geomagic control X). Differences among the systems and various measurements were evaluated using the Kruskal–Wallis test. Statistically significant differences were validated using pairwise comparisons (α = 0.05). Occlusal gaps in the CEREC, EZIS, and Carestream groups were 113.0, 161.3, and 438.2 µm, respectively (p < 0.001). The axial gaps were 83.4, 78.0, and 107.9 µm, respectively. The marginal gaps were 77.8, 99.3, and 60.6 µm, respectively, and the whole gaps were 85.9, 107.3, and 214.0 µm, respectively. Significant differences were observed with the EZIS system compared with the other two systems in terms of the marginal gap sizes. The CEREC system showed no significant differences among the four measured regions. However, the EZIS and Carestream systems did show a statistically significant difference (p < 0.05). All three systems were judged to be capable of fabricating clinically acceptable prostheses, because the marginal gap, which is the most important factor in the marginal fit of prostheses, was recorded to be below 100 µm in all three systems.

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