polyurethane scar dressings

Polyurethane dressings are used in scar treatment. Brands available on the consumer market are Curad Scar Therapy and Cutinova Thin Dressings. Both brands offer self-adhesive, breathable, flexible products in either semi-transparent, skin tone or clear formulations. But do polyurethane dressings really work on scars?

Studies on polyurethane dressings show a positive effect on scar appearance. The dressings are hydroactive which means they maintain a moist environment and prevent bacterial contamination which is useful when the dressings are used as a wound occlusive. (they are used both in wound care as well as scar treatment) There is also some evidence for the prevention of hypertrophic scar formation. Some studies show a slight advantage when these dressings are combined with pressure therapy.

One study of 60 patients noted significant improvements in blood supply (microcirculation) and surface qualities in patients who were treated with polyurethane dressings for 6 weeks after surgical incisions.

A report called ‘Topical Treatments for Hypertrophic Scars‘ by Zurada, Kriegel, and Davis notes that the use of polyurethane dressing in scar therapy has: “unclear effects on the development of new hypertrophic scars but has been shown to improve the prominence and appearance of mature scars in a small randomized trial. Further studies are necessary to elucidate its role in hypertrophic scar treatment.”
Conclusion of this report: There is questionable evidence for the effectiveness of polyurethane scar dressings in preventing hypertrophic scars and some evidence for effective treatment of mature scars.

The same report mentions silicone scar sheets as a more effective product; “the most accepted treatment for old and new hypertrophic scars is silicone gel sheeting”. A score rating the overall efficacy of the two products is given.
Polyurethane dressings: +/-
Silicone sheets: ++

The dressings should be applied daily (most convenient will probably be overnight) for approximately 12 hours. This should be maintained for at least a month or two. One study compared the use of the dressings for 12 hours with 24 hours per day. No relevant differences between the scars appearance (color, softness and elevation) was noted.

Which are better for mature scars, polyurethane dressings or silicone dressings?

In another study four treatments on mature scars (2.5 to 4-year old) were compared. The four therapies were;  polyurethane dressings; polyurethane with compression; silicone sheeting with compression; and compression alone.

“All treatment modalities were found to have significant effects both on tissue function and scar tissue surface structure. The most pronounced effects were achieved with the combination of polyurethane dressing plus compression or silicone sheeting plus compression. The positive effect of the polyurethane dressing alone on scar tissue was even slightly superior to that of compression therapy alone.” Source: Effect of four treatment variants on the functional and cosmetic state of mature scars.

Another report by Dr. Thomas Mustoe states:

We have investigated the effects of silicone gel sheeting (Cica-Care: Smith & Nephew, Largo, FL) in a rabbit model of hypertrophic scarring . As expected, silicone gel sheeting effectively reduced scar hypertrophy in this model system. A polyurethane dressing (Op Site: Smith & Nephew, Largo, FL) [..] did not have similar beneficial effects on scarring.

Since advantages over silicone sheeting in immature scars are unclear or not present and this type of therapy is equally effective on mature scars I would tend to conclude silicone sheets have more evidence behind their overall efficacy.