In the control group, after cleaning the lesion with tap water and 2% chlorhexidine gluconate, a thin layer of Silver Sulfadiazine Cream 1% was applied and covered with gauze and bandage. The dressing changes occurred every 48 hours. The patients were evaluated every 48 hours for the study parameters.

In the test group, the treatment was Nile Tilapia Fish Skin, which have a patent registered at the National Institute of Industrial Property (INPI) under number BR 10 2015 021435 9. Nile Tilapia Fish Skin was subjected to a rigorous process of chemical sterilization, glycerolization and irradiation, followed by microbiological tests for bacteria and fungi, before storage in sterile refrigerated packaging. Prior to its use in the patient, the skin was washed thrice in sterile 0.9% saline for 5 minutes, in order to remove glycerol. Regarding application in the study patients, after cleaning the lesion with tap water and 2% chlorhexidine gluconate, Nile Tilapia Fish Skin was applied and covered with gauze and bandage. Throughout the treatment, dressings with Nile Tilapia Fish Skin were only changed if the biomaterial was not properly adhered to the wound bed. The patients were evaluated every 48 hours for the study parameters.

In the search of new therapies for burns, the skin of Brazil's most cultivated fish, the Nile tilapia, which was mostly a waste product (although sometimes used as a resistant material for artisanal handicraft), was suggested as a possibility for the development of a low-cost xenograft. Apart from non-infectious microbiota, Nile Tilapia Fish Skin presented histomorphological similarities with human skin in pre-clinical studies. It was shown to have a deep dermis formed by thick collagen fibers organized on parallel/horizontal and transversal/vertical arrangement and composed, in comparison, by larger amounts of type I collagen. Nile Tilapia Fish Skin did not present variations in its microscopic structure and tensile strength after glycerolization, irradiation and posterior rehydration, recovering its natural consistency after glycerol removal.

Number of days until complete reepithelialization of the burn wound, considering application of the first dressing as day zero. Complete reepithelialization was defined as a ≥95% reepithelialization calculated via clinical judgment from the consultant

In the control group, a dressing change was defined as the act of cleaning the wound and reapplying the Silver Sulfadiazine Cream 1%, which was performed every 48 hours. In the test group, a dressing change was defined as the act of replacing the Nile Tilapia Fish Skin which did not adhere properly and/or replacing gauze and bandage that is full of exudate.

In order to audit analgesic intake, apart from the medication prescription (dipyrone and/or tramadol), the patients received a daily record card. They were asked to take the medication only if they felt pain, always respecting instructions in the prescription, and to register the amount of medication taken and the date on the card. Upon returning for medical evaluation, the remaining medication was checked and compared to the daily record card.

Consumption of materials of the burn treatment center was controlled by the completion of a specific form, an activity performed at the end of each patient visit by the nursing staff. The resources consumed were divided into three categories: a) products used for wound management (either Nile Tilapia Fish Skin or Silver Sulfadiazine Cream 1%); (b) hospital material required for dressing preparation (such as sterile gloves, chlorhexidine, gauze, and bandage); and c) analgesic medication required throughout treatment (dipyrone and/or tramadol). Human resources were not evaluated.

Patients were informed that the left end of the 10 cm horizontal line (with a "0") represented "no pain" and that the right end (with a "10") represented the "most severe pain imaginable." They were asked to make a mark on the line that represented their current pain intensity, and the Visual Analogue Scale pain intensity level was scored by measurement of the distance from the mark to the "no pain" end of the line.