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Cutting Efficiency (cutting + efficiency)

Distribution by Scientific Domains
Medical Sciences75%

Selected Abstracts

Harvesting of intraoral autogenous block grafts from the chin and ramus region: Preliminary results with a variable square pulse Er:YAG laser

LASERS IN SURGERY AND MEDICINE, Issue 5 2008
Stefan Stübinger DDS
Abstract Background and Objectives It was the aim of this pilot study to evaluate the feasibility, benefits and limitations of a variable square pulse (VSP) Er:YAG laser for harvesting intraoral bone grafts from either the chin or ramus region. Materials and Methods In 12 patients (5 female, 7 male) a VSP Er:YAG laser was used to harvest bone grafts either from the ramus (3) or the symphyseal area (9). For the osteotomies, the Er:YAG laser was applied with a pulse energy of 1,000 mJ, a pulse duration of 300 microseconds, and a frequency of 12 Hz (energy density 157 J/cm2). The spot size was 0.9 mm and the handpiece was kept at a distance of about 10 mm from the bone surface. Results There was no visible carbonization or osseous debris on the surface of the osteotomy gap. Damage of adjacent soft tissue structures by mechanical or thermal trauma was minimal. Cutting efficiency was excellent and the overall time required for the procedure was not increased. However, due to a free manual positioning of the laser beam in the non-contact mode, it was difficult to get a well defined osteotomy line without irregularities on the surface. Slight deviations of the original angulation of the laser beam led to considerable bone loss which restricted osteotomy of ramus grafts to three cases. Depth control was limited to visual inspection. Conclusion The bone ablation technique using a (VSP) Er:YAG laser yielded superior clinical results without impairment of wound healing and in comparison to other laser systems, no significant time loss occurred. Yet, the missing depth control and the necessity of carefully handling the laser beam position and its angulation limit the use of a (VSP) Er:YAG laser to regions where a safe and fixed guidance of the laser beam is feasible. Lesers Surg. Med. 40:312,318, 2008. © 2008 Wiley-Liss, Inc. [source]

Numerical simulation of the fracture process in cutting heterogeneous brittle material

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2002
H. Y. Liu
Abstract The process of cutting homogeneous soft material has been investigated extensively. However, there are not so many studies on cutting heterogeneous brittle material. In this paper, R-T2D (Rock and Tool interaction), based on the rock failure process analysis model, is developed to simulate the fracture process in cutting heterogeneous brittle material. The simulated results reproduce the process involved in the fragmentation of rock or rock-like material under mechanical tools: the build-up of the stress field, the formation of the crushed zone, surface chipping, and the formation of the crater and subsurface cracks. Due to the inclusion of heterogeneity in the model, some new features in cutting brittle material are revealed. Firstly, macroscopic cracks sprout at the two edges of the cutter in a tensile mode. Then with the tensile cracks releasing the confining pressure, the rock in the initially high confining pressure zone is compressed into failure and the crushed zone gradually comes into being. The cracked zone near the crushed zone is always available, which makes the boundary of the crushed zone vague. Some cracks propagate to form chipping cracks and some dip into the rock to form subsurface cracks. The chipping cracks are mainly driven to propagate in a tensile mode or a mixed tensile and shear mode, following curvilinear paths, and finally intersect with the free surface to form chips. According to the simulated results, some qualitative and quantitative analyses are performed. It is found that the back rake angle of the cutter has an important effect on the cutting efficiency. Although the quantitative analysis needs more research work, it is not difficult to see the promise that the numerical method holds. It can be utilized to improve our understanding of tool,rock interaction and rock failure mechanisms under the action of mechanical tools, which, in turn, will be useful in assisting the design of fragmentation equipment and fragmentation operations. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Tooth Preparation: A Study on the Effect of Different Variables and a Comparison Between Conventional and Channeled Diamond Burs

JOURNAL OF PROSTHODONTICS, Issue 1 2004
Daniel F. Galindo DDS
Purpose: The purpose of this study was to evaluate the different variables involved in tooth cutting to characterize intrapulpal temperature generation, cutting efficiency, and bur durability when using conventional and channeled diamond burs. Materials and Methods: Forty premolars and 60 molars were selected for the study. Four diamond burs were paired according to grit size: 125- ,m grit: Brasseler Coarse (Control 1) and TDA System (Test 1) burs; and 180- ,m grit: Brasseler CRF (Control 2) and NTI Turbo Diamond (Test 2) burs. Each bur was used twice when cutting the premolar teeth, whereas it was used for 60 cuts when cutting the molar teeth. The data were analyzed to compare the correlation of bur design, grit and wear, amount of pressure, advancement rate, revolutions per minute, cutting time and rate, and proximity to the pulp chamber with intrapulpal temperature generation, cutting efficiency, and bur longevity. The mean values of test and control burs in each group were compared using an ANOVA (p < 0.05 for significant differences) for temperature generation and an ANOVA and the Tukey multiple range test (p, 0.05) for cutting efficiency and bur longevity. Results: No significant difference was found in intrapulpal temperature generation while cutting premolar and molar teeth with conventional and channeled diamond burs. In both groups, the mean temperature recorded during and after the cutting procedure was lower than the baseline temperature. For premolar teeth, no significant difference was established for control and test burs for the load required to cut into the tooth and the cutting rate. However, both test burs showed significantly fewer revolutions per minute when compared to their control counterparts. For the molar teeth, the Brasseler CRF bur required a significantly lower cutting load when compared to the NTI bur, whereas no difference was noted between the other pair of burs. The cutting rate was significantly higher for both control burs, whereas revolutions per minute (rpm) were greater for control coarser burs only. Overall, channeled burs showed a significantly lower cutting efficiency when compared to conventionally designed burs. Conclusion: Within the limitations of this study, channeled burs showed no significant advantage over conventional diamond burs when evaluating temperature generation and bur durability. Moreover, the cutting efficiency of conventional burs was greater than that of channeled burs. [source]