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ABBREVIATIONS
DFDBA: demineralized freeze-dried bone allograft
ePTFE: expanded polytetrafluorethylene
FDBA: freeze-dried bone allograft
INTRODUCTION
Replacement of missing teeth in the anterior maxilla is challenging from both a surgical and restorative standpoint. Ideal 3-dimensional implant placement, which is dependent on residual ridge dimensions, is critical to provide an acceptable esthetic result.1 Unfortunately, the high resorption rate of the anterior maxilla after extraction can jeopardize the implant position if additional augmentation procedures are not performed.2-5 Occasionally, due to excessive resorption and/or enlargement of the incisive canal, the neurovascular contents of this anatomic structure are in the path of the ideal osteotomy. It is surmised that placement of a titanium fixture in direct contact with the incisive canal can lead to complications such as a nasopalatine duct cyst6,7 or implant failure.
The incisive canal is located in the midline of the maxilla posterior to the central incisors. The nasopalatine nerve and terminal branch of the nasopalatine artery pass through the canal, which provides innervation and vascularization to the palatal region from canine to canine. These structures also form anastomoses with the greater palatine nerve and artery, so there is collateral neurovascular supply. Large variations in the size and shape of this canal have been documented, stressing the need for 3-dimensional imaging in cases in proximity to this structure.8-11 Additionally, studies have shown that the size of the canal increases with ridge atrophy.9
The main concern with removing canal contents is neurosensory disturbances. Magennis et al12 retrospectively evaluated neurosensory disturbance after sectioning of the nasopalatine nerve after elevating a palatal flap. Eighty-five patients were divided into 2 groups: 1 with nerve sectioning and 1 without. None of the patients were aware of altered sensation, but 2 patients in the severed group experienced sensory loss. It appears that due to the additional supply from the greater palatine nerve and artery, there is immediate revascularization and gradual reinnervation of the anterior palate. Moreover, the following reports support this finding (summarized in the Table).
Rosenquist et al13 first described a technique treating 4 patients where the contents of the canal were obliterated and filled with autogenous cancellous bone harvested from the chin. Implants were placed after 6 months of healing, and implant survival at 12-15 months was 100%. No patients...