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ABSTRACT Introduction: currently, talking about highly resistant aesthetic dental restorations implies talking of yttrium-stabilized zirconium dioxide (Y-TZP) ceramic systems, which have become important due to their good mechanical and physical properties and high biocompatibility. One of the main complications of such restorations nowadays is ceramic coating delamination. It has been shown that the interface of both materials is the origin of failure because of poor bonding strength, mainly due to excessive internal tension in the coating material caused by a difference in the thermal expansion coefficients of both materials. Methods: 15 zirconium blocks were randomly sorted out into 3 groups: one control group and two groups were the surface of bonding to the ceramic coating was modified by grinding with rounded diagonal and squared burs respectively. Once the samples were sintered, the ceramic coating was applied and shear bond strength tests were performed. A one-way analysis of variance (ANOVA) was conducted. The Tukey′s range test was used to compare the difference in results among groups. Results: the results in this study were very heterogeneous. The average shear bond strength values were 20.2 MPa ± 6.8 MPa for Group A; 5.87 MPa ± 4.87 Mpa for Group B, and 3.69 ± 2.68 MPa for Group C. Conclusions: it is not necessary to prepare the zirconium surface with mechanical grinding in order to improve shear bond strength in ceramic coatings.
RESUMEN Introducción: hoy en día, hablar de restauraciones odontológicas estéticas de alta resistencia implica hablar de sistemas cerámicos de dióxido de zirconio estabilizados con itrio (Y-TZP), los cuales han cobrado importancia por sus buenas propiedades mecánicas y físicas y por su buena biocompatibilidad. Una de las principales complicaciones que están sufriendo hoy en día dichas restauraciones es la delaminación de la porcelana de recubrimiento. Se ha determinado que la interface de los dos materiales es el origen de la falla a causa de una deficiente resistencia de unión, debido principalmente a una tensión interna excesiva en el material de recubrimiento, por una diferencia entre los coeficientes de expansión térmica de ambos materiales. Métodos: se tomaron 15 bloques de zirconio y fueron divididos aleatoriamente en 3 grupos: un grupo control y los otros dos con modificación en la superficie de unión a la cerámica de recubrimiento por medio de una rallado con fresa redonda de forma diagonal y cuadrangular respectivamente. Una vez fueron zinterizados, se puso la cerámica de recubrimiento y finalmente se les realizó pruebas de cizallamiento. Se llevó a cabo un análisis de varianza de una vía (ANOVA). Se usó la prueba de Tukey múltiple para comparar la diferencia de los resultados entre los grupos. Resultados: los resultados arrojados en el estudio fueron muy heterogéneos. Los valores promedio de resistencia de unión al cizallamiento arrojados fueron 20,2 MPa ± 6,8 MPa para el grupo A; 5,87 MPa ± 4,87 Mpa para el grupo B, y 3,69 ± 2,68 MPa para el grupo C. Conclusiones: no es necesario preparar la superficie de zirconio con trabas mecánicas por medio de un fresado para mejorar la resistencia de unión con la cerámica de recubrimiento.
Subject(s)
Esthetics, Dental , Zirconium , CeramicsABSTRACT
BACKGROUND: The purpose of the study was to compare the degree of degeneration of the articular and bursal layers of delaminated supraspinatus tendons based on histological examination. METHODS: Fifty-four patients with a full-thickness rotator cuff tear were included in the study. Tendon specimens were harvested during arthroscopic rotator cuff repair from the lateral torn edges of the articular and bursal layers of the delaminated tear. Harvested samples were stained with H&E dye and evaluated based on a semi-quantitative grading scale. RESULTS: There were no significant differences in the seven histological characteristics of tendon degeneration: fiber structure, fiber arrangement, round nuclei, regional variations in cellularity, vascularity, collagen stainability, and hyalinization between the articular and bursal layers of the delaminated rotator cuff tear (all p>0.05). Total degeneration scores of articular and bursal sides were 13.1 ± 3.85 points and 13.2 ± 3.42 points, respectively, and were not significantly different (p=0.958). CONCLUSIONS: The study demonstrates that tendon degeneration was similar in the articular and bursal sides of the delaminated fullthickness rotator cuff tear, suggesting that degeneration would be a main etiology for the rotator cuff tear not only in the articular side but also in the bursal side. Considering potential disadvantages of subacromial decompression, this study tentatively suggests routine use of subacromial decompression as well as the need for halting or recovery from rotator cuff degeneration for better rotator cuff repair.
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Humans , Collagen , Decompression , Hyalin , Rotator Cuff , Tears , TendonsABSTRACT
BACKGROUND: The purpose of the study was to compare the degree of degeneration of the articular and bursal layers of delaminated supraspinatus tendons based on histological examination. METHODS: Fifty-four patients with a full-thickness rotator cuff tear were included in the study. Tendon specimens were harvested during arthroscopic rotator cuff repair from the lateral torn edges of the articular and bursal layers of the delaminated tear. Harvested samples were stained with H&E dye and evaluated based on a semi-quantitative grading scale. RESULTS: There were no significant differences in the seven histological characteristics of tendon degeneration: fiber structure, fiber arrangement, round nuclei, regional variations in cellularity, vascularity, collagen stainability, and hyalinization between the articular and bursal layers of the delaminated rotator cuff tear (all p>0.05). Total degeneration scores of articular and bursal sides were 13.1 ± 3.85 points and 13.2 ± 3.42 points, respectively, and were not significantly different (p=0.958). CONCLUSIONS: The study demonstrates that tendon degeneration was similar in the articular and bursal sides of the delaminated fullthickness rotator cuff tear, suggesting that degeneration would be a main etiology for the rotator cuff tear not only in the articular side but also in the bursal side. Considering potential disadvantages of subacromial decompression, this study tentatively suggests routine use of subacromial decompression as well as the need for halting or recovery from rotator cuff degeneration for better rotator cuff repair.
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Humans , Collagen , Decompression , Hyalin , Rotator Cuff , Tears , TendonsABSTRACT
Introduction: Recurrent Corneal Erosion Syndrome is a resistant condition to treat .Many modalities of treatment is available. Alcohol assisted epithelial delamination is relatively a new procedure and not widely practiced. This study evaluates the efficacy and safety of the procedure. Material & Methods: This is a retrospective study conducted in our hospital .We have enrolled 30 patients who underwent the procedure within last two years. Patients with RCE who remained symptomatic despite topical lubrication was included .Patients were followed up at 1 day, 4 days, 1 week, and 1 month. Success was defined as resolution of symptoms after 1 month of treatment. The preoperative and postoperative data were collected from EMR and analyzed. Results: Twenty nine patients were stable after the procedure. One patient required repeated treatment. There were no post operative complications. No patients lost any line of visual acuity. Conclusion: Alcohol assisted epithelial delamination is a safe and effective procedure for treating patients with recurrent corneal erosion syndrome.
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Objective To investigate the phenomenon of amorphous carbon coating delamination during crimping and expansion of the vascular stent, and study how to avoid such phenomenon from both material selection and dimension design of the stent. Methods Amorphous carbon coatings were deposited onto a bare metal stent by chemical vapor deposition method, and then to simulate the crimping and expansion process of the stent. Coating delamination at different regions of the stent was observed by scanning with electron microscope, and the force mechanism and influencing factors related with amorphous carbon coating delamination during stent crimping and expansion were analyzed by finite element method. Results The finite element results could perfectly agree with the experimental results. The thickness of amorphous carbon coatings determined the complexity, as well as the formation pattern of coating delamination at different regions of the stent. Larger elastic modulus of amorphous carbon coatings could cause the formation of coating delamination much easier to occur. Besides, the stent modulus would also have some impact with different influencing patterns at different regions on coating delamination. Conclusions In order to avoid coating delamination, the thickness of amorphous carbon coatings should be carefully designed, and the elastic modulus of both amorphous carbon coatings and stents should be rationally selected.
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AIM: To investigate the role of N-cadherin in the delamination of neural crest cells. METHODS: The normal expression of N-cadherin in neural tube was identified using in situ hybridization. The cells with N-cadherin over expression were obtained by transfection of wild-type N-cadherin (wt-N-cadherin) ,and the cells with N-cadherin silencing expression were obtained by transfection of dominant-negative N-cadherin (dn-N-cadherin). The migration of cranial neural crest cells was determined by the technique of immunohistochemistry. RESULTS: Either overexpression or down-regulation of N-cadherin significantly affected the migration of cranial neural crest cells. CONCLUSION: Delamination and migration of the cranial neural crest cells rely on the relative N-cadherin expression in the neural tube during neurulation.
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STATEMENT OF PROBLEM: Zirconia-based restorations have the common technical complication of delamination, or porcelain chipping, from the zirconia core. Thus the shear bond strength between the zirconia core and the veneering porcelain requires investigation in order to facilitate the material's clinical use. PURPOSE: The purpose of this study was to evaluate the bonding strength of the porcelain veneer to the zirconia core and to other various metal alloys (high noble metal alloy and base metal alloy). MATERIAL AND METHODS: 15 rectangular (4x4x9mm) specimens each of zirconia (Cercon), base metal alloy (Tillite), high noble metal alloy (Degudent H) were fabricated for the shear bond strength test. The veneering porcelain recommended by the manufacturer for each type of material was fired to the core in thickness of 3mm. After firing, the specimens were embedded in the PTFE mold, placed on a mounting jig, and subjected to shear force in a universal testing machine. Load was applied at a crosshead speed of 0.5mm/min until fracture. The average shear strength (MPa) was analyzed with the one-way ANOVA and the Tukey's test (alpha= .05). The fractured specimens were examined using SEM and EDX to determine the failure pattern. RESULTS: The mean shear strength (+/- SD) in MPa was 25.43 (+/- 3.12) in the zirconia group, 35.87 (+/- 4.23) in the base metal group, 38.00 (+/- 5.23) in the high noble metal group. The ANOVA showed a significant difference among groups, and the Tukey's test presented a significant difference between the zirconia group and the metal group. Microscopic examination showed that the failure primarily occurred near the interface with the residual veneering porcelain remaining on the core. CONCLUSION: There was a significant difference between the metal ceramic and zirconia ceramic group in shear bond strength. There was no significant difference between the base metal alloy and the high noble metal alloy.
Subject(s)
Ceramics , Collodion , Dental Porcelain , Fires , Fungi , Polytetrafluoroethylene , Shear Strength , ZirconiumABSTRACT
STATEMENT OF PROBLEM: Interfacial toughness is important in the mechanical property of layered dental ceramics such as core-veneered all-ceramic dental materials. The interfaces between adjacent layers must be strongly bonded to prevent delamination, however the weak interface makes delamination by the growth of lateral cracks along the interface. PURPOSE: The purpose of this study was to determine the effect of the reaction layer on the interfacial fracture toughness of the core/veneer structure according to the five different divesting. MATERIALS AND METHODS: Thirty five heat-pressed Lithia-based ceramic core bars (IPS Empress 2), 20 mm x 3 mm x 2 mm were made following the five different surface divesting conditions. G1 was no dissolution or sandblasting of the interaction layer. G2 and G3 were dissolved layer with 0.2% HF in an ultrasonic unit for 15min and 30 min. G4 and G5 were dissolved layer for 15min and 30min and then same sandblasting for 60s each. We veneered bilayered ceramic bars, 20 mm x 2.8 mm x 3.8 mm (2 mm core and 1.8 mm veneer), according to the manufacturer's instruction. After polishing the specimens through 1 micro m alumina, we induced five cracks for each of five groups within the veneer close to interface under an applied indenter load of 19.6N with a Vickers microhardness indenter. RESULTS: The results from Vickers hardness were the percentage of delamination G1: 55%, G2: 50%, G3: 35%, G4: 0% and G5: 0%. SEM examination showed that the mean thickness of the reaction layer were G1 93.5+/-20.6 micrometer, G2 69.9+/-14.3 micrometer, G3 59.2+/-20.2 micrometer, G4 0.61+/-1.44 micrometer G5 0+/-0 micrometer. The mean interfacial delamination crack lengths were G1 131+/-54.5 micrometer, G2 85.2+/-51.3 micrometer, and G3 94.9+/-81.8 micrometer. One-way ANOVA showed that there was no statistically significant difference in interfacial crack length among G1, G2 and G3(p>0.05). CONCLUSION: The investment reaction layer played important role at the interfacial toughness of body ceramic bonded to Lithia-based ceramic.