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Bone density assessments of dental implant sites: 2. Quantitative cone-beam computerized tomography.

PURPOSE
Bone density was evaluated in designated implant sites using a novel volumetric computerized tomographic device. Those measurements were then compared with traditional quantitative computerized axial tomography and subjective bone density evaluation.


MATERIALS AND METHODS
Sixty-three potential sites for implant placement in jaws from 9 human cadavers were used. Indicator rods 2 mm in diameter were placed in all sites. Radiographic images representing 1-mm buccolingual slices immediately mesial and distal to the rods were selected. Bone density in Hounsfield units was assessed using quantitative cone-beam computerized tomography (QCBCT) and quantitative computerized tomography (QCT) in a standardized implant area superimposed on the images. Bone density was also subjectively evaluated by 2 independent examiners using the Lekholm and Zarb classification.


RESULTS
The QCBCT bone density values were generally found to be higher than the corresponding QCT measurements. The correlations between the QCT and QCBCT values, however, were very high in spite of this systematic difference between the 2 methods. The Lekholm and Zarb ratings for the 2 examiners showed correlation coefficients ranging between 0.46 and 0.60 for the relationships with the QCBCT values. For each of the scores used for the subjective classification, however, a wide range of corresponding QCBCT values was observed.


DISCUSSION
High dosage has been the major impediment to the utilization of CT in implant dentistry. The development of a reliable volumetric CT alternative with reduced radiation should provide an effective method for the assessment of both bone quantity and bone density.


CONCLUSIONS
Access to objective radiographic bone density values should constitute a valuable supplement to subjective bone density evaluations prior to implant placement. QCBCT could be considered an alternative diagnostic tool for preoperative bone density evaluation, especially since the reported radiation dose is minimal.