الفهرس 
Mechanism of hypertrophic scar formationOnly 14 pages are availabe for public view
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Abstract
Hypertrophic scars form in predisposed individuals after skin trauma. They are considered to be a result of altered wound healing with excessive scar tissue formation. Patients complain from pain, pruritis, immobility of joint region, disfigurement and psychological problems. Successful treatment of hypertrophic scars has always been challenging. Although several treatment modalities have been proposed, no consistant modality is available. Besides the intralesional, topical and surgical treatment, lasers including PDL and ablative fractional CO2 laser have become popular therapeutic alternative for the treatment of hypertrophic scars. PDL targets the vascular proliferation using the principles of selective thermolysis leading to selective damage to microcapillaries of HSs coagulating these vessels and turning off some of the inflammatory component. The ablative fractional CO2 laser is used to target water in abnormal collagen, several millimeters below the surface of the skin. When applied in a fractional pattern, columns of abnormal scar are ablated, allowing new collagen to form in a controlled manner, with rapid reepithelialization of surface. The aim of this work was to compare the efficacy and safety of pulsed dye laser versus fractional CO2 laser in treatment of hypertrophic scars. Ten patients complaining of hypertrophic scars were selected from Outpatient Clinics of Dermatology and Plastic surgery Departments at Tanta University Hospital.All patients were subjected to the following: 1) Complete history taking. 2) General and dermatological examination. 3) Evaluation of hypertrophic scar. 4) One half of the scar was treated by of ablative fractional CO2 laser using power 15W, spacing 800μm, dwelling time 600μs and stack 3 while the other half was treated by pulsed dye laser using a handpiece with a 7-mm spot, pulse duration of 1.5ms and fluence of 6 J/cm2 every month for three sessions. Assessment of the efficacy of the therapeutic procedure:(I) Clinical assessment: 1) Digital photograph was taken at the base line and one month after the last session. 2) Evaluation was done by using the Vancouver Scar Scale (VSS), which is based on pigmentation, vascularity, pliability and height of hypertrophic scar before treatment and one month after the last session.111 (II) Safety and tolerability assessment: The patients were informed to report any complications occurred as erythema, edema, pain, infection and postinflammatory hyperpigmentation. (III) Histopathological assessment: A 3mm punch biopsy was taken from five patients from the same lesional site after the end of treatment to detect the histopathological changes. The sections were stained with haematoxylin and eosin (H&E), masson trichrome and orcein stains.