Root fracture

Plants exert additional effects on weathering. The presence of forest trees tends to lower soil surface temperatures by shading the soil surface and reducing surface albedo (Kelly et al., 1998). Also, roots fracture mineral grains and increase soil porosity and permeability, which allows greater contact between soil solutions and minerals (April and Keller, 1990 Colin et al., 1992). 

Fig. 13.13a-c. Image a and b mandibular fracture image C dental root fracture... 

The stress values at the core region of the traditional core crown post were two and three times greater than non split-shank and split-shank post respectively. Therefore, the structure of core crown post could induce stress concentration in the root around the end of the post. In addition, the Co-Cr crown base margin of buccal side of the traditional core crown post was demonstrated a stress concentration by pressing contact on the dentin margin of the root (Fig. 5). This also meant enlarged possibility of root fracture. 

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]. 

Barkhordar RA, Ryle R, Jan A. (1989) Effect of metal collars on resistance of endodontically treated teeth to root fracture. J Prosthet Dent 61 676-678... 

Milot P, Stein RS. (1992) Root fracture in endodontically treated teeth related to post selection and crown design. J Prosthet Dent 68, 428-35... 

Tjan AH, Whang SB (1985) Resistance to root fracture of dowel channels with various thicknesses of buccal dentin walls. J Prosthet Dent 53 496-500... 

Substantial work on the appHcation of fracture mechanics techniques to plastics has occurred siace the 1970s (215—222). This is based on earlier work on inorganic glasses, which showed that failure stress is proportional to the square root of the energy required to create the new surfaces as a crack grows and iaversely with the square root of the crack size (223). For the use of linear elastic fracture mechanics ia plastics, certaia assumptioas must be met (224) (/) the material is linearly elastic (2) the flaws within the material are sharp and (J) plane strain conditions apply ia the crack froat regioa. 

This equation predicts that the fracture stress increases with the square root of the number of bonds to be broken and is inversely proportional to M. The percolation parameter p is in effect, the normalized bond density such that for a perfect net without defects, p = 1 and for a net that is damaged or contains missing bonds. 

Root, R.L. "Method for Decreasing Friction Loss in a Well Fracturing Process," US patent No. 3,254,719(1966). 

In China, the bark and leaves are used for the treatment of fractures. The roots are used in Malaysia to recover from childbirth and exhaustion, and a paste of the plant is used to treat orchitis. The plant contains indole alkaloids such as conodurinine, 19 (S) hydroxyconoduramin, 19 (S)-hydroxyervahanine A, and related iboga alkaloid congeners, and like the species mentioned earlier, and in fact the genera Ervatamia, in general, would be worth investigating for serotoninergic activities (17). 

The process of infection of lupine nodule cells by Rhizobia was examined by the thin-section electron microscopic technique, as well as the freeze-fracture technique. Different membranes such as infection thread membranes, peribacterioid membranes, plasma membranes, membranes of cytoplasmic vesicles, and membranes of the Golgi bodies and ER were stained with uranium-lead, silver, phosphotungstic acid, and ZIO (31). ZIO stained the membranes of the proximal face of the Golgi bodies and endoplasmic reticulum. ZIO staining has given good contrast in thick sections such as a cotyledon cell, a root cell, and an aleurone layer for ER, dictyosomes cisternae, mitochondria, and nuclear envelopes (17,32-37). 

Outlined in this section will be the method of Maruyama et al. (12), who were successful in observing metaphase chromosomes inmeristem-atic cells of Vida faba when the fixation of freeze-fractured roots was performed after incubation in buffer solutions. The method allows for experimental studies on chromosome morphology. In fact, the published report also gives the effects of divalent cations on chromosome morphology. 

Phyllanthus virgatus, is rubbed around the ear for ear infections. Extract of different dried parts of the palm are taken orally for filari-asis. A water solution of the cmshed dried bark or husk and grated bark of Hibiscus tiliaceus is used externally to soak fractures and sprains. Crushed aerial root tips of Ficus prolixa are fried with coconut cream made of fresh endosperm, and the resulting oil is taken orally as a laxative in treating serious diseases " . 

Tooth fracture may involve the crown, root or both and with or without the exposure of the pulp. Fracture exposing the... 

If wetting is instantaneous and the instantaneous wetting load at initial time is negligible, then the autohesive bond fracture stress, cr, is proportional to the fourth root of contact time and the fracture energy, GIC, is proportional to the square root of contact time as shown in the following equations ... 

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