Vertical palatal bone dimensions on lateral cephalometry and cone-beam computed tomography: implications for palatal implant placement.

To evaluate the necessity of three-dimensional imaging (computed tomography [CT]/cone-beam computed tomography [CBCT]) for paramedian insertion of palatal implants. Lateral radiographs and CBCT scans were performed from 18 human skulls. For lateral cephalometry, the nasal floor (right/left) and the oral hard palate of all skulls were lined with a tin foil for contrast enhancement. The quantity of vertical bone as measured on lateral radiographs was compared with CBCT measurements obtained in median and parasagittal planes and at minimum bone height. Spearman's rank correlation coefficients were determined for bivariate correlation analysis. The median palatal bone height on CBCT (mean 8.98 mm; standard deviation [SD] 3.4) was markedly higher than the vertical height seen on lateral radiographs (mean 6.6 mm; SD 3.2). Comparing lateral cephalometry with CBCT, the strongest association was observed at the minimum palatal bone height (r=0.926; P<0.001; Spearman's rank correlation coefficient). Lateral radiographs allow accurate and adequate assessment of vertical bone before paramedian insertion of palatal implants. The vertical bone dimension as displayed on lateral cephalometry reflects the minimum bone height rather than maximum bone in the median plane. Therefore, a preoperative CT or CBCT is only indicated when the lateral cephalometry reveals a marginal quantity of bone.