Fixation with reconstruction plates under critical conditions: the role of screw characteristics

• Published in: International journal of oral and maxillofacial surgery 1996-12, Vol.25 (6), p.469-473
• Main Authors: Söderholm, Anna-Lisa, Rann, Berton A., Skutnabb, Kai, Lindqvist, Christian
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Bone Plates; Bone Resorption - etiology; Bone Screws - adverse effects; Dentistry; Equipment Design; fixation; Head and neck surgery. Maxillofacial surgery. Dental surgery. Orthodontics; mandible; Mandible - surgery; Mandibular Condyle; Mandibular Prosthesis; Maxillofacial surgery. Dental surgery. Orthodontics; Medical sciences; Osteonecrosis - etiology; Prosthesis Failure; reconstruction plate; screw characteristics; Sheep; Surface Properties; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Temporomandibular Joint
• ISSN: 0901-5027; 1399-0020
• DOI: 10.1016/S0901-5027(96)80086-5

Mandibular angular ostectomy defects in 12 sheep were bridged with a titanium plate system (THORP), designed according to the screw-plate-locking principle. Two screw designs (hollow and solid) and two rough (plasma-coated, sandblasted)-surface and one smooth (anodized)-surface structure were tested in a critical two-screw anchorage model. Fixation with two screws only per fragment was successful in only one-third of the cases. The fixation results were superior for screws with a rough surface, either sandblasted or plasma-coated. The hollow-screw design did not seem to offer special advantages over the solid screws with identical surface structure. In the successful cases, the bone-screw contact was maintained continuously over a period of 8 weeks, and anchorage was even enhanced by reinforcement of the cancellous structures. In the unsuccessful cases, peri-implant bone resorption seemed to be related to jeopardized bone perfusion in the vicinity of the implants. It is presumed that a plating system with locked screws has the advantage that only two screws will hold a relatively short condylar process. This study proved the assumption to be questionable. However, in view of the problems related to prosthetic replacement of the temporomandibular joint, an attempt to salvage the articular portion may still be justified in selected cases, even if the chance of success is as low as 30%.