Browsing by Author "Hamdy, Ahmed"

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EFFECT OF SURFACE TREATMENT AND ARTIFICIAL AGING ON MICROTENSILE BOND STRENGTH OF ZIRCONIA TO RESIN
(EDJ, 2017-07) Hamdy, Ahmed; Hashem, Abou Bakr Hossam
Statement of problem: Reliable bond to zirconia based materials has proven to be difficult which is the major limitation against luting zirconia restorations. Purpose: This in vitro study compared effect of selective infiltration etching (SIE) and tribo- chemical silica sandblasting (TSS) on microtensile bond strength to zirconia based material before and after different artificial aging intervals. Materials and methods: Twenty Lava plus high translucency zirconia disks (3 M, ESPE) were randomly divided into two study groups according to their surface treatment: (a) selective infiltration etching (SIE) and (b) tribo-chemical silica sandblasting (TSS). Zirconia disks were bonded to composite resin specimens using Panavia F2.0 resin cement. Zirconia resin bond strength was evaluated using the microtensile bond strength test (MTBS) and the test was repeated before and after the following intervals of accelerated artificial aging; 1 week, 2 weeks, 3 weeks and 4 weeks of water storage (37°C). A repeated measures ANOVA and Bonferroni post-hoc tests were used to analyze the data. Results: The interaction between surface treatments and storage times were statistically significant. Data analysis revealed significant differences between the two surface treatments (P<0.05).Selective infiltration etched specimens demonstrated relatively higher MTBS values than TSS (48.5 and 24.8 MPa).SEM examination of broken microbars revealed more interfacial failure type for TSS than SIE specimens that showed a predominantly cohesive failure type. Conclusions: Selective infiltration etching provided superior micro-tensile bond strength results compared to tribo-chemical silica sandblasting. Established bond strength by selective infiltration etching was not affected by artificial aging as tribo-chemical silica sandblasting.
ESTHETICS REHABILITATION OF SEVERELY DECAYED UPPER ANTERIOR TEETH
(October University of Modern Sciences and Arts, 2018) Said, Amira; Hamdy, Ahmed; Taher, Heba; ElFadaly, Lamyaa; Abou Heikal, Mohamed; ElMaghraby, Ihab; Al Afify, Reham; Badawi, Ahmed
Nowadays, smile enhancement is considered a high demand to fulfill patient’s smile fantasy. A 30 year old male patient presented to MSA clinics complaining from life time problem of anterior teeth. Clinical examination revealed multiple decayed teeth with old composite restorations, in addition to several missing teeth and remaining roots. Restoration of badly destructed upper anterior teeth was performed by root canal treatment, fiber post, composite core then all ceramic crowns. Upon radiographic examination using panorama and cone beam CT, implant were excluded as a treatment modality to restore posterior teeth so flexible denture was the treatment of choice.
Industrial Upper Limb Exoskeleton
(MILITARY TECHNICAL COLLEGE, 2019-08) Badawy, Ahmed; Hamdy, Ahmed; Zakaria, Yehia Mohamed
The aim of this paper is to develop an arm exoskeleton for workers at factories to help manipulate objects easily from one place to another. The arm is controlled by the worker using a joystick, as he moves the stick the internal resistance in the stick for up and down directions is connected to the arm exoskeleton, whereas the resistance directions for left and right is connected to the shoulder exoskeleton. The microcontroller receives any change in this resistance, and then translates it to the motor via the motor driver. It activates the motors to move the arm to the required position. The motor is attached to a power screw which transmits the torque of the motor to the elbow or shoulder joint. The function of the power screw is to decrease the rotational speed transmitted to the joint allowing the user to control the angle of the joint. The power screw also adds the privilege of locking the angle while holding heavy items. Limit switches have been added to prevent the worker from moving the exoskeleton out of bounds and to prevent the workers from injuring themselves.
Push-Out Bond Strength of Different Esthetic Post: An In-Vitro Study
(SAODS, 2019-01) Hamdy, Ahmed
Purpose: This in-vitro study measured push-out bond strength of different posts as function of radicular regions. Statement of Problem: In non-circular or excessively flared root canals, prefabricated posts may not fit well, increasing cement thickness and bubbles at coronal level which may alter its mechanical performance causing impaired post retention. Push-out bond strength test in different radicular thirds of posts will detect location of failure in bonded esthetic posts. Methods: 40 sound extracted human central incisors were used in this study. All teeth were endodontically treated and decoronated 2 mm above CEJ. Then were randomly divided into 4 groups of 10 each regarding type of post used: group 1 (PD): Polymer infiltrated ceramic, Paradigm MZ 100 (3M-ESPE); group 2 (FRC) Fiber post, Postec Plus (Ivoclar Vivadent); group 3 (ZR): Lava Zirconium diox- ide blocks (3M-ESPE); group 4 (CP): Cosmo Post, Zirconium dioxide (Ivoclar Vivadent). All posts were luted with Panavia 21 (Kuraray Noritake, Japan). Push-out tests were performed to evaluate the bond strength of different posts at different radicular regions. Data were statistically analyzed using one way (ANOVA)and Scheffe test made pairwise comparison (α = 0.05). Partially yttrium-stabilized zirconium-oxide post systems were introduced in mid 1990s by various researchers [1,2]. Pure zir- conia material shows polymorphic phase transformation from a cubic, to tetragonal, to monoclinic phase, accompanied by a high volume change when cooling down after sintering, which makes the sintered body unstable. Therefore, dental zirconia material contains 3 to 6 weight % Yttria-stabilized zirconia as an additive to stabilize the ceramic in the tetragonal phase which is usually Different resin luting agents and corresponding bonding sys- tems have been proposed for cementing tooth-colored posts and Results: FRC group recorded the highest mean bond strength value (11.78 ± 0.79MPa). PD group showed higher results (10.10 ± 1.12MPa) than ZR (9.56 ± 0.85 MPa) and CP (7.93 ± 0.89 MPa) and the 2 latter groups were not significantly different from each other p ≤ 0.05. Regardless to post type, it was found that middle region recorded highest bond strength means value, then apical region, meanwhile the lowest mean bond strength values were recorded at cervical regions p ≤ 0.05. Conclusions: Within limitations of this study the following can be drawn: 1- Push-out mean bond strength of different esthetic posts are significantly affected by the type of its materials and manufacturing; FRC recorded the highest bond strength values, ZR and CP showed the least values (P ≤ 0.05). 2- Regardless type of the post, the middle radicular region (as Fiber Reinforced Composite) recorded the highest bond strength then the apical region, meanwhile the cervical region (as Cosmo Post) showed the lowest bond strength values P ≤ 0.05.