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Objective To study the damage propagation and evolution mechanism of cartilage under compressive load. Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method, and the process of damage evolution under compressive load was simulated and analyzed with parameters. The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stage were obtained. Results The strain in surface and the forefront of cartilage damage increased significantly with the increase of compression displacement, and they were obviously in positive correlation; in the process of damage evolution, there was a trend that cartilage extended to the deep and both sides simultaneously; cracks and damage in cartilage extended preferentially along the fiber tangent direction. With the aggravation of cartilage damage, the lateral extension speed was significantly faster than the longitudinal extension speed. Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers. And the damage in matrix and fiber promote each other. The evolution speed and degree of cartilage vary constantly in different layers and at different stages. These results can provide the qualitative reference for prediction and repair of cartilage damage, as well as the theoretical basis for explaining clinical pathological phenomena of damage degeneration and treatment.
ABSTRACT
Objective To study the damage propagation and evolution mechanism of cartilage under compressive loads.Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method,and the process of damage evolution under compressive loads was simulated and analyzed with parameters.The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stages were obtained.Results The strain in the surface and forefront of cartilage damage increased significantly with the increase of compression displacement,and they were obviously in positive correlation;in the process of damage evolution,there was a trend that cartilage extended to the deep and both sides simultaneously;cracks and damage in cartilage extended preferentially along the fiber tangent direction.With the aggravation of cartilage damage,the lateral extension speed was significantly faster than the longitudinal extension speed.Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers.The damages in matrix and fiber promote each other.The evolution speed and degree of cartilage vary constantly in different layers and at different stages.These results can provide the qualitative reference for prediction and repair of cartilage damage,as well as the theoretical basis for explaining pathological phenomena of damage degeneration and its clinic treatment.
ABSTRACT
Objective To study the damage propagation and evolution mechanism of cartilage under compressive loads.Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method,and the process of damage evolution under compressive loads was simulated and analyzed with parameters.The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stages were obtained.Results The strain in the surface and forefront of cartilage damage increased significantly with the increase of compression displacement,and they were obviously in positive correlation;in the process of damage evolution,there was a trend that cartilage extended to the deep and both sides simultaneously;cracks and damage in cartilage extended preferentially along the fiber tangent direction.With the aggravation of cartilage damage,the lateral extension speed was significantly faster than the longitudinal extension speed.Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers.The damages in matrix and fiber promote each other.The evolution speed and degree of cartilage vary constantly in different layers and at different stages.These results can provide the qualitative reference for prediction and repair of cartilage damage,as well as the theoretical basis for explaining pathological phenomena of damage degeneration and its clinic treatment.
ABSTRACT
Objective To study the damage propagation and evolution mechanism of cartilage under compressive loads.Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method,and the process of damage evolution under compressive loads was simulated and analyzed with parameters.The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stages were obtained.Results The strain in the surface and forefront of cartilage damage increased significantly with the increase of compression displacement,and they were obviously in positive correlation;in the process of damage evolution,there was a trend that cartilage extended to the deep and both sides simultaneously;cracks and damage in cartilage extended preferentially along the fiber tangent direction.With the aggravation of cartilage damage,the lateral extension speed was significantly faster than the longitudinal extension speed.Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers.The damages in matrix and fiber promote each other.The evolution speed and degree of cartilage vary constantly in different layers and at different stages.These results can provide the qualitative reference for prediction and repair of cartilage damage,as well as the theoretical basis for explaining pathological phenomena of damage degeneration and its clinic treatment.
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PURPOSE: The use of temporary or permanent cements in fixed implant-supported prostheses is under discussion. The objective was to compare the retentiveness of one temporary and two permanent cements after cyclic compressive loading. MATERIALS AND METHODS: The working model was five solid abutments screwed to five implant analogs. Thirty Cr-Ni alloy copings were randomized and cemented to the abutments with one temporary (resin urethane-based) or two permanent (resin-modified glass ionomer, resin-composite) cements. The retention strength was measured twice: once after the copings were cemented and again after a compressive cyclic loading of 100 N at 0.72 Hz (100,000 cycles). RESULTS: Before loading, the retention strength of resin composite was 75% higher than the resin-modified glass ionomer and 2.5 times higher than resin urethane-based cement. After loading, the retentiveness of the three cements decreased in a non-uniform manner. The greatest percentage of retention loss was shown by the temporary cement and the lowest by the permanent resin composite. However, the two permanent cements consistently show high retention values. CONCLUSION: The higher the initial retention of each cement, the lower the percentage of retention loss after compressive cyclic loading. After loading, the resin urethane-based cement was the most favourable cement for retrieving the crowns and resin composite was the most favourable cement to keep them in place.
Subject(s)
Alloys , Crowns , Dental Cements , Glass , Patient Selection , Prostheses and ImplantsABSTRACT
STATEMENT OF PROBLEM: Fracture of the tooth-colored superstructure material is one of the main prosthetic complications in implant-supported prostheses. PURPOSE: The purpose of this in vitro study was to compare the fracture strength between the cement-retained implant-supported metal-ceramic crowns and the indirect composite resinveneered metal crowns under the vertical compressive load. MATERIAL AND METHODS: Standard implants of external type (AVANA IFR 415 Pre-mount; Osstem Co., Busan, Korea) were embedded in stainless steel blocks perpendicular to their long axis. Customized abutments were fabricated using plastic UCLA abutments (Esthetic plastic cylinder; Osstem Co., Busan, Korea). Thirty standardized copings were cast with non-precious metal (Rexillium III, Pentron, Walling ford, Conn., USA). Copings were divided into two groups of 15 specimens each (n = 15). For Group I specimens, metal-ceramic crowns were fabricated. For Group II specimens, composite resin-veneered (Sinfony, 3M-ESPE, St. Paul, MN, USA) metal crowns (Sinfony-veneered crowns) were fabricated according to manufacturer's instructions. All crowns were temporary cemented and vertically loaded with an Instron universal testing machine (Instron 3366, Instron Corp., Norwood, MA, USA). The maximum load value (N) at the moment of complete failure was recorded and all data were statistically analyzed by independent sample t-test at the significance level of 0.05. The modes of failure were also investigated with visual analysis. RESULTS: The fracture strength of Sinfony-veneered crowns (2292.7 +/- 576.0 N) was significantly greater than that of metal-ceramic crowns (1150.6 +/- 268.2 N) (P < 0.05). With regard to the failure mode, Sinfony-veneered crowns exhibited adhesive failure, while metal-ceramic crowns tended to fracture in a manner that resulted in combined failure. CONCLUSION: Sinfony-veneered crowns demonstrated a significantly higher fracture strength than that of metal-ceramic crowns in cement-retained implant-supported prostheses.
Subject(s)
Adhesives , Axis, Cervical Vertebra , Crowns , Plastics , Prostheses and Implants , Stainless SteelABSTRACT
Objective: To determine the failure mode of depressive osteochondral fracture under the maximum compressive load. Design: An experimental cadaveric study. A compressive load was applied through an indenter on a femoral condyle to create a depressive osteochondral fracture until the maximum load was reached. Background: Most depressive osteochondral fractures occur without a gross articular cartilage injury because a large amount of load is reabsorbed by the surrounding tissues, especially the subchondral bone under the cartilage. We asked what the mode of depressive osteochondral fracture is. It might function as a load adsorber from the articular cartilage. Methods: Three groups of depressive osteochondral fractures were studied. Croup 1 consisted of 12 pieces of middle third of normal median and lateral femoral condyles. Groups 2 and 3 consisted of 12 pieces of osteoporotic and osteosclerotic middle of both femoral condyles. Using a universal testing machine, a depressive osteochondral fracture was created by applying a uniaxial compressive load through an indenter until the load rose to the maximum level. At that point, the load applied was stopped in order to minimize the extent of subchondral trabeculae fracture. Maximum load was recorded. Pressure and stiffness were calculated. The pattern of depressive fracture was studied histologically. Results: The failure mode of depressive osteochondral fracture wan such that the bone under the articular cartilage had a subchondral plate fracture, an interlacing of bone trabeculae under the plate, and a few fractures of the bone trabeculae. The interlacing of subchondral bone trabeculae was most evident in the normal bone as compared with the osteoporotic and osteosclerotic bones. The osteosclerotic bone failed at the highest load, while the osteoporotic bone failed at the lowest. Conclusion: The subchondral plate fracture and the interlacing of subchondral bone trabeculae under the plate are the characteristics of the failure mode of depressive ostechondral fracture. This failure mode occurs before there is a discernible fracture of the subchondral bone trabeculae. The amount of load causing fracture depends on the quality of the bone. Relevance: The failure mode, especially the interlacing of subchondral bone trabeculae, night function as a load absorber from the articular cartilage. Therefore, the quality of subchondral bone is important for protection of the articular cartilage from compressive load injury.