Al. Soderholm et al., FIXATION WITH RECONSTRUCTION PLATES UNDER CRITICAL CONDITIONS - THE ROLE OF SCREW CHARACTERISTICS, International journal of oral and maxillofacial surgery, 25(6), 1996, pp. 469-473
Mandibular angular ostectomy defects in 12 sheep were bridged with a t
itanium plate system (THORP), designed according to the screw-plate-lo
cking principle. Two screw designs (hollow and solid) and two rough (p
lasma-coated, sandblasted)-surface and one smooth (anodized)-surface s
tructure 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 i
dentical surface structure. In the successful cases, the bone-screw co
ntact was maintained continuously over a period of 8 weeks, and anchor
age was even enhanced by reinforcement of the cancellous structures. I
n the unsuccessful cases, peri-implant bone resorption seemed to be re
lated to jeopardized bone perfusion in the vicinity of the implants. I
t is presumed that a plating system with locked screws has the advanta
ge 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 temporomandi
bular joint, an attempt to salvage the articular portion may still be
justified in selected cases, even if the chance of success is as low a
s 30%.