Degradable poly(anhydride ester) implants: effects of localized salicylic acid release on bone

Degradable poly(anhydride ester) implants in which the polymer backbone bre aks down into salicylic acid (SA) were investigated. In this preliminary wo rk, local release of SA from the poly(anhydride esters), thus classified as 'active polymers', on healthy bone and tissue was evaluated in vivo using a mouse model. Degradable polyanhydrides that break down into inactive by-p roducts were used as control membranes because of their chemical similarity to the active polymers. Small polymer squares were inserted over the expos ed palatal bone adjacent to the maxillary first molars. Active polymer memb ranes were placed on one side of the mouth, control polymers placed on the contralateral side. Intraoral clinical examination showed that active polym er sites were less swollen and inflamed than control polymer sites. Histopa thological examination at day 1 showed essentially no difference between co ntrol and active polymers. After 4 days, active polymer sites showed epithe lial proliferation to a greater extent than the polyanhydride controls. Aft er 20 days, active polymer sites showed greater thickness of new palatal bo ne and no resorptive areas, while control polymer sites showed less bone th ickness as well as resorption including lacunae involving cementum and dent ine. From these preliminary studies, we conclude that active polymers, name ly poly(anhydride esters), stimulated new bone formation. (C) 2000 Elsevier Science Ltd. All rights reserved.