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Assessment of bone density in the posterior maxilla based on Hounsfield units to enhance the initial stability of implants.

PURPOSE
The poor bone quality that exists in the posterior maxilla is associated with lower initial stability and higher failure rates in implants. This study examined the bone densities of edentulous posterior maxillae by computed tomography (CT).


MATERIALS AND METHODS
Based on CT images, the voxel values representing implant replacement in the posterior maxillary regions of 30 patients were calculated in the range from 150 to 2,000 Hounsfield units (HU). The bone densities of these regions were categorized according to Misch's classification and compared among individuals and between sexes.


RESULTS
The average of the median individual CT values was 495 HU (95% confidence interval: 442-547 HU) and was significantly higher in males than in females. Most of the bone in the posterior maxillae was classified as D3 (350-850 HU) or D4 (150-350 HU) according to Misch's classification, comprising 50% and 32% of the entire regions, respectively.


CONCLUSIONS
More than 80% of the edentulous posterior maxillae consisted of porous cortical crest or no cortical bone according to CT, although the bone densities varied markedly among individuals. More detailed assessments of bone density may be useful to enhance initial stability of implants in the posterior maxilla.