Ferrule effect

Keywords— Ferrule effect. Post, Finite Element Analysis, Endodontically treated teeth, root fracture. 

A dental ferrule is an encircling band of cast metal around the coronal surface of the tooth. It has been proposed that the use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing endodontically treated teeth [8]. Ferrule effect is defined by a 360-degree metal crown collar surrounding parallel walls of dentine and extending coronal to the shoulder of the preparation [9]. Several studies have shown the ferrule design affects the pattern of root fracture in restored teeth and improve fracture resistance [10, 11, 12, 13, 14, 15] and ferrule height is critical factor to mechanical resistance [9, 16]. 

The cause of the weaker G dependence must be ascribed to some particular feature of geometry, although exactly what it is has not been found. All of the three bundles involved had their rods supported and correctly positioned by wires wrapped helically around certain of the rods, and it is possible that the wires caused an unfavorable distribution of steam and water. However, it is doubtful that the wire wraps were themselves responsible, since several of the bundles conforming to Eq. (28) were also wire wrapped. (Other devices used for rod supports are suitably spaced grids and ferrules.) The explanation most probably lies in a combination of the effects of the wire wraps with the effects of given rod diameters and rod spacings. For ease of identification, the data that conform with Eq. (28) are hereafter called normal data. 

The Council recommends that industry not use any printing on the cap and ferrule of injectables except to convey warnings. The Council encourages industry to employ failure mode and effects analysis in its design of devices, and the packaging and labeling of medications and related devices. 

The metering valve in an MDI is the critical component in the design of an effective delivery system. The main function of the metering valve is to reproducibly deliver a portion of the liquid phase of the formulation in which the medication is either dissolved or dispersed. The valve also forms the seal atop the canister to prevent loss of the pressurized contents. The valves generally comprise at least seven components that are constructed from a variety of inert materials. Typical materials of construction are acetal or polyester for the valve body, stainless steel or acetal for the valve stem, generally anodized aluminum for the ferrule, and butyl, nitrile, or neoprene for the elastomers used in the seals and gaskets [43],... 

Fipve 17.1 Effect of the critical distance between the tip of the fenule and the tip of the tubing. If the tip is too short for the type of fitting us a dead volume results that causes band q>reading. If the tip is too long, the ferrule will not seat and the connection will leak. 

Fig. 8. Schematic of a typical fiber-optic probe. SST a matching piece of cylindrical stainless steel SML SELFOC microlens SSF a stainless steel or ceramic ferrule used for mounting the bare optical fibre F epoxy used for holding fibre in ferrule HT heat shrink tubing FC fibre cable CT SMA t)q)e II male connector. Da and (AO) are the effective detector aperture and divergence angle, respectively.

Slide the retaining fitting or nut over the end of a new column and then the ferrule, and position them at least 6 in. away from the column end. It will be necessary to cut several inches from the end of the column because ferrule particles may have entered the column and can cause tailing and adverse adsorptive effects. 

The purposes of this study were to reconstruct the maxilla and an endodontically treated maxillary incisor tooth from Computed Tomography (CT) scan images of a real patient and investigate the effect of ferrule height on mechanical crown resistance and the stress distribution on the root and luting cement by Finite Element Analysis (FEA). 

Ng CC, Al-Bayat MI, Dumbrigue HB et al. (2004) Effect of no ferrule on failure of teeth restored with bonded posts and cores. Gen Dent 52 143-6... 

Pereira JR, Ornelas FD, Conti PCR et al. (2006) Effect of a crown ferrule on the fracture resistance of endodontically teeth restored with prefabricated posts. J Prosthet Dent 95 50-54... 

A4.1 The cup thermometer, which conforms also to the specifications for the low-range thermometer used in the Pensky-Martens flash tester, Test Method D 93, is fi equently supplied by the thermometer manufacturer with a metal or polytetrafluoroefii ene ferrule intended to fit the collar on the lid of the flash tester. This f ule is firequently suiqrle-mented by an adapter which is used in the laiger-diameter collar of the Pensky-Martens q>paiatus. Differences in dimensions of these collars, wbidi are immaterial in their effect on the result of te are a source of considerable... 

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