Sixty mongrel dogs were divided into three groups of twenty dogs. One group of twenty dogs underwent placement of a rigid reconstruction plate (2.7mm thickness of plates and 3.0mm diameter of screws, Richards plating system, stainless-steel) and labeled normal mandibles stress shielded (NMSS) group. Another group of twenty dogsundeuuent cancellous cellular bone grafts of 3.5cm in length and a rigid reconstruction plate. In this group the plates were left in place until the time of sacrifice(1460 days) The group was labeled as a bone grafted mandibles stress shielded (BGSS). Ten dogs of each group were sacrificed at day 60. Another ten dogs of cach group were sacrificed at day 1460. In addition, all intitial resection specimens were processed for histomorphometry on trabecular bone area(TBA) as a normal non-stress shielded reference value of day-0 control (NMNSS) group. The histomorphometric results are as follows. Average percentage of TBA at day 0 control in NMNSS group was 44+/-5%. Average percentage of TBA in NMNSS group at 60 days was 42+/-6% , and that at 1460days was 42+/-4%. Average percentage of TBA in NMSS group at 60days was 47+/-6%, and that at 1460days was 44+/-4%, while average percentage of TBA at day 0 control was 44+/-5% (pinot available). Average percentage of TBA in BGNSS group at 60 days was 67+/-4, and that at 1460 days was 65+/-4%, while average percentage of TBA in day o control was 44+/-5%. BGNSS group shows, once each mandible was bone grafted at 60 days, that bone density was increased due to the high cellular bone grains. But after 1460 days there are little significant change, and that they are stable for four years(p<.001). Average percentage of TBA in BGSS group at 60 days was O+/-6, and that at 1460 days was 66+/-4% , while average percentage of TBA at day O control was 44+/-5%. BGSS group with the plate left in place for 4 years also shows the enhanced bone trabecular percentage at 60 days due to the high cellular bone grafts, but after 60 days until 4 years still little significant change(p<.001). The result data indicates the stress shielding from the rigid reconstruction plate on the mandible is not valid. It is suggested that clinicians do not need to remove reconstruction plates for fear of stress shielding.
Animals ; Bone Density ; Edible Grain ; Dogs* ; Mandible ; Reference Values ; Transplants*