The estimation of cement film thickness by an in vivo technique.
About: This article is published in British Dental Journal.The article was published on 1971-08-03. It has received 1023 citations till now.
Citations
More filters
••
TL;DR: Although conclusions were based mainly on in vitro studies, the digital impression technique provided better marginal and internal fit of fixed dental restorations than conventional techniques did.
Abstract: Statement of problem Limited evidence is available for the marginal and internal fit of fixed dental restorations fabricated with digital impressions compared with those fabricated with conventional impressions. Purpose The purpose of this systematic review was to compare marginal and internal fit of fixed dental restorations fabricated with digital techniques to those fabricated using conventional impression techniques and to determine the effect of different variables on the accuracy of fit. Material and methods Medline, Cochrane, and EMBASE databases were electronically searched and enriched by hand searches. Studies evaluating the fit of fixed dental restorations fabricated with digital and conventional impression techniques were identified. Pooled data were statistically analyzed, and factors affecting the accuracy of fit were identified, and their impact on accuracy of fit outcomes were assessed. Results Dental restorations fabricated with digital impression techniques exhibited similar marginal misfit to those fabricated with conventional impression techniques (P>.05). Both marginal and internal discrepancies were greater for stone die casts, whereas digital dies produced restorations with the smallest discrepancies ( P P >.05), whereas die and restoration materials were statistically associated ( P Conclusions Although conclusions were based mainly on in vitro studies, the digital impression technique provided better marginal and internal fit of fixed restorations than conventional techniques did.
257 citations
Cites background from "The estimation of cement film thick..."
...L OF PROSTHETIC DENTISTRY mm,(8) and fixed restorations with marginal gaps of less than 120 mm were considered more likely to be successful.(9) The internal fit is also an important criterion and has had an effect on the seating of the crown and consequently the marginal fit....
[...]
••
TL;DR: Findings show that the crowns studied can be prescribed with confidence knowing that the precision of fit will consistently be less than 70 microns, which is well below the industry standard.
Abstract: Statement of problem. Strength, color stability, and precision of fit are requirements for all-ceramic restorations. The Procera AllCeram crown system, composed of a densely sintered high-purity alumina core combined with a low fusing surface porcelain, appears to satisfy most of these requirements. However, evaluation of marginal fit has not been reported. Purpose. This study measured the precision of fit of the Procera AllCeram crown fabricated with Procera CAD/CAM technology for the premolar and molar teeth fit to a die. Material and methods. Five ivorine maxillary first premolars and first molars were prepared for full-coverage crowns. Preparations were standardized with a convergence angle of 10 degrees, chamfer margins of 1.3 to 1.5 mm circumferentially, and occlusal reduction of 2.0 mm. AllCeram crowns were fabricated for the dies, and the fit of the crown to the die was determined by using a standardized procedure with a silicone impression material that served a dual role: (1) as a retrievable luting agent, and (2) to replicate the internal aspects of the crown. Laser videography was used to measure the gap dimension between the crowns and the dies at the marginal opening, the axial wall, the cusp tip, and the occlusal adaptation measurement locations. Mean gap dimensions and standard deviations (SDs) were calculated for marginal opening, internal adaptation, and precision of fit. Results. Mean gap dimensions and standard deviations at the marginal opening for the premolar and molar crowns were 56.0 μm SD ± 21 and 63.0 μm SD ± 13 μm, respectively. The mean gap dimensions and SDs of the internal adaptation were 69.0 μm SD ± 17 μm for axial wall, 48.0 μm SD ± 12 μm for cusp tip, and 36.0 μm SD ± 7 μm for occlusal adaptation for the premolar crowns; and 49.0 μm SD ± 3 μm axial wall, 67.0 μm SD ± 21 μm cusp tip, and 74.0 μm SD ± 29 μm occlusal adaptation for molar crowns. Precision of fit and SDs for premolar and molar crowns were 52.0 μm SD ± 19 μm and 63.0 μm SD ± 20 μm, respectively. Mean marginal openings and precision of fit gap dimensions for the crown groups were not significantly different at the .05 level. However, gap dimensions that defined the internal adaptation at the measurement locations were different ( P ≤.05). Conclusion. Mean gap dimensions for marginal openings, internal adaptation, and precision of fit for the crown groups were below 70 μm. These findings show that the crowns studied can be prescribed with confidence knowing that the precision of fit will consistently be less than 70 μm. (J Prosthet Dent 1998;80:394-404.)
257 citations
••
TL;DR: Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use.
Abstract: Statement Of Problem. Gap measurements along margins are frequently used to assess the quality of single crowns. However, the number of gap measurements required for clinically relevant results in laboratory studies is not known. Purpose. This study estimated the minimum number of gap measurements on margins of single crowns to produce relevant results for gap analysis. Methods And Material. Ten all-ceramic crowns were fabricated on a master steel die. Gaps along crown margins were investigated in a scanning electron microscope on the master steel die without cementation and on replica dies after conventional cementation. Measurements were made in 100 μm steps according to 3 gap definitions. The initial number of measurements per crown (n = 230) was reduced to smaller subsets using both systematic and random approaches to determine the impact on the quality of results. Results. On the data of gap definition 1, reduction from 230 to about 50 measurements caused less than ±5 μm variability for arithmetic means. Analysis of standard errors showed slowly increasing values smaller than 3 μm, both indicating no relevant impact on the quality of results. Smaller data sizes yielded accelerated increase of standard errors and divergent variabilities of mean. The minimum of 50 measurements did not depend on gap definition or on cementation condition. Conclusion. Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use. (J Prosthet Dent 2000;83:40-9.)
251 citations
••
TL;DR: The fully digital fabrication method provided better margin fit than the conventional method, and the overall mean ±SD vertical gap measurement was significantly smaller than that for the conventionally made crowns.
Abstract: Statement of problem Little evidence is available with regard to the marginal fit of crowns fabricated with digital impressions and computer-aided design/computer-aided manufacturing technology in comparison with crowns fabricated from conventional techniques. Purpose The purpose of this study was to determine and compare the marginal fit of crowns fabricated with digital and conventional methods. Material and methods The maxillary right second premolar was prepared for a ceramic crown in a typodont. The typodont was then digitized with a laboratory scanner, and the digital file was used to mill a replica of the maxillary arch from a monolithic block of yttria-stabilized zirconia to serve as the master model. Digital impressions of the prepared maxillary right second premolar were recorded with a scanning unit. Scan files were exported as .STL files and sent by e-mail to a dental laboratory. The files were input into a digital design workflow for digital articulation, digital waxing, and design of the definitive crown. Fifteen crowns were produced by milling computer-aided designed lithium disilicate glass ceramic blocks with a 5-axis milling. Fifteen lithium disilicate glass ceramic crowns were produced with a conventional impression and a laboratory fabrication method. The original zirconia die was removed from the zirconia master model to evaluate the crown margins. Circumferential marginal gap measurements were made at 8 measurement locations: mescal, distal, buccal, palatal and associated line angles (mesiobuccal, mesiolingual, distobuccal, and distolingual). Measurements were made to determine the vertical component of the marginal gap according to the definition of marginal fit. Results A total of 240 images (2 groups, 15 crowns per group, 8 sites per crown) were recorded and measured. The overall mean ±SD vertical gap measurement for the digitally made crowns was 48 ±25 μm, which was significantly smaller than that for the conventionally made crowns (74 ±47 μm). Conclusion The fully digital fabrication method provided better margin fit than the conventional method.
246 citations
••
TL;DR: The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restoration prepared by casting and milling techniques, showing great potential to replace the aforementioned fabrication techniques in the long term.
Abstract: Purpose
The aim of this study was to review the effect of selective laser melting (SLM) procedure on the properties of dental structures made of Co-Cr alloys and to evaluate its quality and compare it to those produced by conventional casting and milling fabrication techniques.
Materials and Methods
A computerized database search using PubMed and Scopus was conducted for peer-reviewed scientific research studies regarding the use of SLM in Co-Cr dental alloys with no restrictions for publication years. The search engines provided hundreds of results, and only 48 scientific research papers, case studies, or literature reviews were considered relevant for this review.
Results
The innovative manufacturing concept of SLM offers many advantages compared with casting and milling fabrication techniques. SLM provides different microstructure from casting and milling with minimal internal porosity and internal fitting, marginal adaptation, and comparable bond strength to porcelain. Mechanical and electrochemical properties of SLM structures are enhanced compared to cast, while clinical longevity of single-metal ceramic crowns is comparable to Au-Pt dental alloy.
Conclusion
The SLM technique provides dental prosthetic restorations more quickly and less expensively without compromising their quality compared with restorations prepared by casting and milling techniques. Clinical significance: The current SLM devices provide metallic restorations made of Co-Cr alloys for removable and fixed partial dentures without compromising the alloy or restoration properties at a fraction of the time and cost, showing great potential to replace the aforementioned fabrication techniques in the long term; however, further clinical studies are essential to increase the acceptance of this technology by the worldwide dental community.
221 citations