Volumetry of simulated bone grafts in the edentulous maxilla by computed tomography: an experimental study

OBJECTIVE: To determine the precision of CT for calculating the volume of bone grafts to the maxilla. METHODS: Plaster of Paris was used to simulate bone as onlay and inlay grafts to the maxillary alveolus and sinus in a dry skull. Two mm thick axial CT scans were obtained. The area of the graft on each slice was measured and volumes calculated according to the formula V(graft)=Sigma of areas x the thickness of each section. Scans were repeated with the skull at approximately +5 degrees and -5 degrees to the horizontal plane and the calculations repeated. The real volume was calculated by the displaced water technique. Precision was estimated as reliability coefficient. RESULTS: The reliability coefficients for the right and left inlay and the onlay grafts were 0.97, 0.6 and 0.96 respectively. CONCLUSION: Calculations of the volume of both inlay and onlay grafts to the maxilla from axial CT is precise.