The effect of gas permeability of film dressings on wound environment and healing.

We have determined the effect of oxygen and carbon dioxide permeability of thin film dressings on wound exudate P O2, P CO2, pH, and epithelialization in shallow wounds on domestic pigs. Three kinds of films were compared: polyvinylidine chloride, a low gas permeability film; polyurethane, a medium gas permeability film; and poly(dimethyl silicone), a high gas permeability film. Exudate under the silicone film had the highest P O2 and the lowest P CO2; exudate under the polyurethane had intermediate P O2 and P CO2; and exudate under the polyvinylidine chloride had the lowest P O2 and highest P CO2. Values for pH under the films correlated inversely with P CO2. The gas tensions and pH are a reflection of the ability of the films to control the diffusion of oxygen into and the loss of carbon dioxide from the wound exudate. Mean epithelialization values at 2 and 3 d were not significantly different under polyvinylidine chloride and polyurethane, but both were higher than under the silicone film. We infer from the data that the use of oxygen and carbon dioxide impermeable film dressings do not affect epithelialization in well-perfused, shallow wounds. The use of the silicone film (highly permeable to both oxygen and carbon dioxide) led to a loss of carbon dioxide. The resulting relatively high pH may have been responsible for the reduced rate of epithelialization which occurred beneath the silicone film.

Pulpotomy as an alternative to canine tooth extraction in monkeys [Macaca mulatta].

An effective method for sealing pulp canals after partial removal of canine tooth crowns from adult rhesus monkeys is described.

Histological characterization of a delayed wound healing model in pig.

Chronic wounds, such as venous ulcers and pressure ulcers, frequently remain unresponsive to currently available treatments. Several animal models of wound healing have been published, including models of impaired healing developed to mimic the clinical condition of chronic wounds better. We used a delayed wound healing model in the pig that uses irradiation of the skin prior to creation of the surgical wounds and characterized it histologically. Radiation was used on one side of the back prior to making four full-thickness wounds on each side. Clinical observations were performed to record granulation tissue, reepithelialization, and wound area as a function of time. Histology data were obtained at 1, 2, 3, and 4 weeks, and slides were stained with hematoxylin and eosin for general observations. Immunohistochemistry was performed using laminin as a marker for blood vessels, and the number, size, and circularity of blood vessels found in the granulation tissue were measured. Our results show that this model causes a delay in wound healing that is mostly apparent between days 7 and 15. Granulation tissue took more time to form and fill the wounds on the irradiated side, and blood vessels were slower to develop. Blood vessels were larger and more irregular in shape on the irradiated side than on the control side. After 2 weeks, healing resumed, indicating that the induced damage was not irreversible. These results suggest that this model can be used to test the effects of therapeutic approaches intended to treat chronic wounds.