Free radicals and side products released during methylmethacrylate polymerization are cytotoxic for osteoblastic cells

Abstract

Polymerization of orthopedic cements makes use of a peroxide initiator which is decomposed by an accelerator to provide free radicals. Free radicals which act on the monomer molecules are also known to induce cell lesions and cell death. We used an in vitro model of cement polymerization to study the effects of free radicals release on osteoblast-like cells. Initiation of methylmethacrylate was done with benzoyl peroxide and acceleration by N,N-dimethylaniline. Bulk polymerization was done in calibrated test tubes which were left aging until use. Polymers (aged from J1 to J31 days after completion of the polymerization process) were sawed to produce slices. Slices were rinsed in distilled water and free radical release was measured by spectrophotometric titration with p-iodonitrotetrazolium. Saos-2 osteoblast-like cells were cultured in parallel on the slices. Cells appeared to be round and were altered when grown on slices prepared freshly after polymerization. Cytomorphometric analysis of the cell shape (surface area and form-factor polyethylene confirmed that they spread and flatten on slices prepared a long time after polymerization. Free radical release from polymethylmethacrylate cements is a long-lasting event that can induce bone cells alterations in their neighborhood. Two cytotoxic mechanisms were evidenced: (a) polymer slices released a stable toxic component which could be removed by extensive washing; (b) they released free radicals which were still detectable several days after the end of polymerization. The titration curve was a negative exponential.

Vertebroplasty in the management of painful bony metastases

“…This may be enhanced by free oxygen radical production and heating during cement polymerization [26,27].…”

Apototic and Necrotic Influence of Dental Resin Polymerization Initiators in Human Gingival Fibroblast Cultures

“…It has been found that resin monomers from dental restorative materials are released into the saliva and diffuse into the tooth pulp, gingiva, mucosa, and circulating blood, where they have potentially toxic effects [4][5][6][7] . Moreover, the polymerization initiators, which are present in smaller amounts than the monomers, are harmful because they generate radicals [8][9][10] . Polymerization initiators used for visible light (VL)-cured resins usually consist of a photosensitizer (primarily camphorquinone (CQ)) and a reducing agent (which is often a tertiary amine such as dimethyl-para-toluidine (DMPT) or dimethylaminoethyl methacrylate (DMAEMA)), as well as benzoyl peroxide (BPO) and DMPT for self-curing resins 11,12) .…”

Abrasion of 6 dentifrices measured by vertical scanning interference microscopy

“…The accelerated and initiated mixture was poured in Peel-a-way embedding molds (25 ml/mold - Polyscience Inc., Warrington, PA, USA) and polymerization took place in a cold environment (+4ºC in a refrigerator with a water bath to limit the temperature peak). Because polymerization is not completed when the blocks have hardened, a one month period separated their preparation from further use 17 . Blocks were then ground on an automatic plane grinding machine Tegramin-30 (Struers, Copenhagen, Denmark) using ascending grads of polishing paper (1200, 2000 and 4000 during 2 min each).…”