Oral and Maxillofacial Surgery

Christian Lindqvist, M.D., Ph.D., D.D.S.
Professor of Oral and Maxillofacial Surgery, Institute of Dentistry, and Chief Physician, Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital

The main focus of research at the Department of Oral and Maxillofacial Surgery is the clinical use of biodegradable materials. The experimental use of self-reinforced (SR) polylactide devices was initiated during the 1980s in our department. Degradation studies were carried out in vitro and in vivo. Plates and screws were used in the fixation of mandibular osteotomies in sheep. After showing that the devices retain their strength for the osteotomy to consolidate, we continued our studies into more clinically aimed procedures in which SSO of the mandible was fixed with SR PLLA screws. The degradation time of the homopolymers is very long and crystalline remnants could be detected even after five years. We continued our experimental research with the use of copolymers of L- and DL-lactic acid and began clinical operations in 1991 when the first orthognathic procedure was carried out. Since then we have used different types of bioabsorbable devices in the fixation of hundreds of orthognathic and access osteotomies, fractures and reconstructions. Not only clinical and radiological studies but also histological, immunohistochemical, EM and in vitro studies have been performed (51 original publications). Immunohistochemistry showed that different polymers degrade at certain time periods and the mechanism of occasional osteolysis is becoming more clear. The occurrence of extracellular matrix proteins and activated myofibroblasts around PLLA and PGA implants associated with low-grade chronic inflammation and prolonged healing and can explain the complications described in the literature.