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Maxillary sinus-floor elevation with nanoporous biphasic bone graft material for early implant placement.

BACKGROUND
Insufficient bone height in the posterior maxilla is caused by bone atrophy after tooth extraction and continued pneumatization of the maxillary sinus. To allow for implant placement in this area, external sinus-floor elevations are performed. For this indication, the application of various bone graft materials can be a reliable alternative to autologous bone.


PURPOSE
The aim of this study was to analyze a nanoporous bone graft material under the condition of early implant treatment in sinus floor elevations.


MATERIALS AND METHODS
Sixty-six patients received 94 individual external sinus-floor elevations as a precondition for implant surgery. As grafting material, a synthetic, nanoporous bone graft material consisting of a mixture of nano-hydroxyapatite and nano-β-tricalciumphosphate crystals, combined with blood from the defect side, was used. Depending on the remaining vertical bone height, implant placement was performed either simultaneously with bone augmentation or consecutively in a delayed approach. After a 4-month healing period, the patients received 218 implants and were followed up clinically, radiographically, and histologically. To quantify the bone situation at implant placement, immunohistochemical analysis using tenascin-C was performed.


RESULTS
We achieved an average vertical bone increase of 8.28 mm (SD, 2.59) for the one-stage approach and 10.99 mm (SD, 1.73) for the two-stage approach after sinus-floor elevation. The augmented areas showed mean resorption rates of 10.32% (one stage) and 10.82% (two stages) of vertical graft during the observation period. Immunohistochemical analysis after 4 months of healing showed high tenascin activity, indicating bone growth. Good primary stability was achieved during implant placement. Mean peri-implant marginal bone loss was 0.45 mm (SD, 0.31).


CONCLUSION
After a mean observation time of 21.45 months, the biomaterial showed good osseointegration and bone stability radiographically. Adding to this the positive histological and immunohistochemical findings, we conclude that, after a relatively short 4-month healing period, the biomaterial showed predictable results.