الفهرس 
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Abstract
Deformity and destruction of the cartilage in the area of the ear, nose, trachea and larynx resulting from trauma, diseases, or surgery provided a difficult reconstructive challenge for the otolaryringologist. The permanent remodeling of a malformed cartilage was often difficult and traditionally has been reconstructed using grafted autogenous cartilage. Various approaches to reshaping cartilagenous grafts have been undertaken, including morselization, carving, scoring and suturing. These methods each have drawbacks including donor site morbidity, inflammation, necrosis, excessive wasting of harvested tissue, postoperative return of the harvested cartilage to its original shape, lack of precise control over curvilinear shaping, and furthermore, may alter tensile strength and resilience of the cartilage.The appearance of the idea that cartilage could be reshaped into stable new geometries using laser irradiation, when cartilage undergoes accelerated stress relaxation and phase transformation at about 60ºC, provided us with hope that laser reshaping of cartilage may be an alternative to these conventional techniques without the attendant morbidity of surgery. from this point of view the aim of this study was to assess and evaluate experimentally cartilage reshaping after diode laser exposure and to measure its stability, biophysical properties and viability to make a schematic protocol for future cartilage reshaping. In this study cartilage reshaping was conducted on a total number of 326 cartilage specimens dissected from the auricles of Egyptian rabbits (1.5 – 2 kg). One hundred specimens were used in a pilot work to be adapted to the laser cartilage reshaping techniques. To achieve the ideal diode laser parameters required for cartilage reshaping. The remained cartilage specimens (226) were used to complete the study in three stages. First stage (cartilage reshaping): cartilage specimens (192) were divided into 2 groups (A & B) according to the number of laser exposures. Group A including 72 cartilage specimens was used for studying the effect of one laser exposure and group B including 72 cartilage specimens was used for studying the effect of two laser exposures. In addition 48 cartilage specimens (24 for each group) were served as a control group aiming to study the number of laser exposure and its effect on other laser parameters (laser power, exposure time and different bend angles) on the process of cartilage reshaping. Results were evaluated for gross changes and specimens were then prepared for viability assessment through Scanning Electron Microscopy (SEM) examination. Three specimens (A, B and C) were chosen to undergo SEM. A comparison of relative viability was done between one controlled (C) non-irradiated cartilage and two irradiated specimens (A) 10W for 10 sec. & (B) 15W for 15 sec. Second stage (biophysical properties): To study the area of irradiated cartilage and its effect on modulus of elasticity, also the effect of water rehydration on the modulus of elasticity following cartilage irradiation using Instron electronic machine. The target specimens were 27 divided into three groups (A, B &C). Group A (12 specimens, only the center of the specimens was irradiated), group B (12 specimens, the entire surface of the specimens was irradiated) were divided according to the cartilage area of laser exposure and group C (3 specimens) served as a control group. Third stage (implantation and viability): The target specimens were 4 used for short term implantation (45 days) and divided into four groups (A, B, C &D), irradiated as follows; specimen (A) 10W for 5 sec. Specimen (B) 10W for 10 sec. & Specimen (C) 15W for 15 sec. while specimen (D) not irradiated and served as control. Following irradiation the 4 specimens were implanted in the rabbit’s subcutaneous layer of the abdominal wall at 4 different sites.Specimens were evaluated for gross change and then prepared for viability assessment through Transmission Electron Microscopy (TEM) examination. Cartilage specimens (4 mm width by 30 mm length with an average thickness of 1.5-2 mm skin included) were irradiated with a diode laser ( = 980 nm, power 10 & 15W, spot size 4 x 8 mm diameter & continuous wave) at a distance of 25 cm from the laser orifice. The specimens were protected from excessive heating and angled through a handmade water-cooling apparatus to form 3 bend angles (30, 40 &60 degrees). Peak temperature was controlled (50 ºC) through a thermocouple placed in contact with cartilage specimen. Results in the pilot study demonstrated that laser parameter of 5W produced no significant cartilage reshaping. While with 20W shrinkage and deformities were observed. Also cartilage thickness of 3mm or less than 1mm had no effect on cartilage reshaping. The results in the 1st stage demonstrated that, for overall diode laser (980 nm) irradiation the higher the laser power, exposure time and bend angle the better the shape retention was observed. Favorable results (80 degrees shape retention) were achieved when 1 time laser irradiation was used together with 30 degrees bend angle with 15W for 20 sec. laser exposure. While best results (60 degrees shape retention) were achieved when 2 times laser irradiation was used with the same laser parameters. On the other side least results (140 degrees shape retention) was achieved when 1 time laser irradiation was used together with 60 degrees bend angle & 10W for 5 sec. laser exposure. In the 2nd stage: The results in this study found that the modulus of elasticity was independent of the area of cartilage irradiation and the average elastic modulus following a 2-hours immersion in saline solution, returned to approximately 90 % (0.444 Mpa in group A & 0.484 Mpa in group B) of the baseline control value (0.538 Mpa). In the 3rd stage and after specimen’s retrieval (45 days) grossly we found that all the specimens underwent the same changes concerning the tissue integrity and resorbtion with a recognized increase in softness. While Transmission Electron Microscopy (TEM) of the laser-irradiated and the non-irradiated control specimens demonstrated that, chondrocyte and its lacuna was in cartilage together with active nucleus. The study concluded that cartilage reshaping using diode laser (980 nm) with water-cooling was found to be cheap, portable & effective. Results demonstrated that, for overall diode laser irradiation, the higher the laser power (10 & 15W), exposure time (5-20 sec.), bend angle (30, 40, 60 degrees) and the number of laser exposure (1 or 2 times) the better the shape retention observed. Also the laser parameters used for reshaping does not adversely affects the intrinsic mechanical properties of cartilage as evidenced by the return of the modulus to approximately 90 % of the baseline value. The observation that the irradiated cartilage when implanted subcutaneously in the rabbit abdominal wall remains viable without evidence of chondrocyte and nucleus damage after 45 days, demonstrates the potential efficacy of our technique for reconstructive surgery. Our experimental work paves the way for further basic and clinical research to investigate long-term cartilage implantation and viability, using different types of lasers and cartilages.