Computer-aided evaluation of preparations for CAD/CAM-fabricated all-ceramic crowns

SUMMARY Objective: To evaluate the significance of reduced axial wall height on retention of adhesively luted, all-ceramic, lithium disilicate premolar computer-aided design/computer-aided manufacturing (CAD/CAM) crowns based on preparations with a near ideal total occlusal convergence of 10°. Methods: Forty-eight recently extracted premolars were randomly divided into four groups (n=12). Each group received all-ceramic CAD/CAM crown preparations featuring axial wall heights of 0, 1, 2, and 3 mm, respectively, all with a 10° total occlusal convergence. Scanned preparations were fitted with lithium disilicate all-ceramic crowns that were luted with a self-etching resin cement. Specimens were tested to failure at a 45° angle to the tooth long axis with failure load converted to megapascals (MPa) based on the measured bonding surface area. Mean data were analyzed using analysis of variance/Tukey's post hoc test (α=0.05). Results: Lithium disilicate crowns adhesively luted on preparations with 0 axial wall height demonstrated significantly less failure resistance compared with the crowns luted on preparations with axial wall heights of 1 to 3 mm. There was no failure stress difference between preparations with 1 to 3 mm axial wall height. Conclusions: Under conditions of this study, adhesively luted lithium disilicate bicuspid crowns with a total occlusal convergence of 10° demonstrated similar failure resistance independent of axial wall height of 1 to 3 mm. This study provides some evidence that adhesion combined with an ideal total occlusal convergence may compensate for reduced axial wall height.

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Accuracy of Ceramic Restorations Made Using an In-office Optical Scanning Technique: An In Vitro Study

Operative Dentistry ◽

10.2341/12-309-l ◽

2014 ◽

Vol 39 (3) ◽

pp. 308-316 ◽

Cited By ~ 24

Author(s):

P Tidehag ◽

K Ottosson ◽

G Sjögren

Keyword(s):

Glass Ceramic ◽

In Vitro Study ◽

Vitro Study ◽

Digital Impression ◽

All Ceramic ◽

Computer Aided ◽

Cad Cam ◽

Ceramic Crowns ◽

Ceramic Crown

SUMMARY The present in vitro study concerns determination of the pre-cementation gap width of all-ceramic crowns made using an in-office digital-impression technique and subsequent computer-aided design/computer-aided manufacturing (CAD/CAM) production. Two chairside video camera systems were used: the Lava Oral scanner and Cadent's iTero scanner. Digital scans were made of a first molar typodont tooth that was suitably prepared for an all-ceramic crown. The digital impressions were sent via the Internet to commercial dental laboratories, where the crowns were made. Also, an impression of the typodont tooth was made, poured, and scanned in order to evaluate the pre-cementation gap of crowns produced from scanning stone dies. These methods and systems were evaluated by creating replicas of the intermediate space using an addition-cured silicone, and the gap widths were determined using a measuring microscope. Hot-pressed leucite-reinforced glass-ceramic crowns were selected as a reference. The mean value for the marginal measuring points of the control was 170 μm, and the values for all the evaluated crowns ranged from 107 to 128 μm. Corresponding figures for the internal measuring points were 141-210 μm and 115-237 μm, respectively. Based on the findings in the present study, an in-office digital-impression technique can be used to fabricate CAD/CAM ceramic single crowns with a marginal and internal accuracy that is on the same level as that of a conventional hot-pressed glass-ceramic crown. In the present study, however, slight differences could be seen between the two types of ceramic crowns studied with respect to the internal fit obtained.

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Dual-scan technique for the customization of zirconia computer-aided design/computer-aided manufacturing frameworks

European Journal of Dentistry ◽

10.4103/1305-7456.119088 ◽

2013 ◽

Vol 07 (S 01) ◽

pp. S115-S118 ◽

Cited By ~ 2

Author(s):

Rafael Ferrone Andreiuolo ◽

Carlos Eduardo Sabrosa ◽

Katia Regina H. Cervantes Dias

Keyword(s):

Computer Aided Design ◽

Uniform Thickness ◽

Simple Manner ◽

Computer Aided Manufacturing ◽

All Ceramic ◽

Computer Aided ◽

Cad Cam ◽

Ceramic Crowns ◽

Tooth Preparation ◽

Aided Design

ABSTRACTThe use of bi-layered all-ceramic crowns has continuously grown since the introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia cores. Unfortunately, despite the outstanding mechanical properties of zirconia, problems related to porcelain cracking or chipping remain. One of the reasons for this is that ceramic copings are usually milled to uniform thicknesses of 0.3-0.6 mm around the whole tooth preparation. This may not provide uniform thickness or appropriate support for the veneering porcelain. To prevent these problems, the dual-scan technique demonstrates an alternative that allows the restorative team to customize zirconia CAD/CAM frameworks with adequate porcelain thickness and support in a simple manner.

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Marginal fit of all-ceramic crowns fabricated using two extraoral CAD/CAM systems in comparison with the conventional technique

Clinical Cosmetic and Investigational Dentistry ◽

10.2147/ccide.s130856 ◽

2017 ◽

Vol Volume 9 ◽

pp. 13-18 ◽

Cited By ~ 11

Author(s):

Fawaz Alqahtani

Keyword(s):

Conventional Technique ◽

Marginal Fit ◽

All Ceramic ◽

Cad Cam ◽

Ceramic Crowns ◽

Cam Systems

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The Tooth as a Basis for Biomimetic Design

10.1115/imece2000-2663 ◽

2000 ◽

Author(s):

Van P. Thompson ◽

Stephen Kao ◽

Ivory Kirkpatrick

Keyword(s):

High Cycle Fatigue ◽

Critical Role ◽

Contact Loads ◽

All Ceramic ◽

Cad Cam ◽

Molar Teeth ◽

Natural Teeth ◽

Wide Transition ◽

Ceramic Crowns ◽

Improved Performance

Abstract Teeth are uniquely capable of withstanding high forces (>200 N) with small contact area (< 0.5 mm2) and a high number of fatigue cycles (> 107) with little evidence of damage. Yet the tooth is comprised of an outer very brittle, anisotropic, highly crystalline enamel layer supported by an inner soft, but tough dentin. These structures are joined by a small (appoximately 30 microns wide) transition zone called the dento-enamel junction (DEJ). The DEJ plays a critical role in transfer of stress across the layers of the tooth. How the enamel-dentin complex (EDC) comprised of these layers and the DEJ is able to withstand the high contact loads and high cycle fatigue is not well understood. An understanding of the interplay of the various components would serve as the basis for design of dental ceramic or resin based composite crowns capable of service lives approaching those on natural teeth. Current all ceramic crowns have high failure rates (1–5% per yr) on molar teeth and improved performance is required before CAD-CAM restorations can be successful.

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