Structural changes around screws used in the treatment of fractured human mandibles

Abstract

The histological changes associated with the insertion of screws into human mandibles are described from two days to six weeks. The bone dust and haemorrhage produced by the initial tapping of the screw holes are forced into the adjacent marrow spaces together with small fragments of bone when the screws the inserted. At eight days, early organisation of the bone debris and haemorrhage is taking place and this is associated with mild inflammation. If many bone fragments have been produced by the preliminary tapping with a drill, there may be marked acute and chronic inflammatory changes at this time. Following this, resorption of the cortical and cancellous bone trabeculae lining the hole leads to the hole becoming lined by fibrous tissue. The extent and rate of bone resorption around the screws depends on the mechanical forces applied to the screws and the mechanical stability of the screws. When any metallic appliance is implanted in bone, a layer of fibrous tissue will always develop around the appliance which subsequently will never be as secure in the bone as it was at the time it was implanted.