Morphologic changes of the nasopalatine canal related to dental implantation: A radiologic study in different degrees of absorbed maxillae

Background: Implant rehabilitation of the edentulous anterior maxilla remains a complex restorative challenge. Intricate preexisting anatomy dictates meticulous and accurate osteotomy planning. With progressive bone loss, the alveolar crest may approach anatomic structures. The nasopalatine nerve and vessels may ultimately emerge from the ridge crest. The radiologic changes of the nasopalatine canal were evaluated in different resorption phases of the premaxilla alveolus with regard to dental implantation. Methods: The study consisted of 207 subjects who had maxillary computed tomography scans before dental implantation. The Lekholm and Zarb classification was used to divide images according to the residual bony ridge: Class A (control group) and classes B to E (study group). Anatomic mapping of the nasopalatine canal structure was carried out in both groups. Results: The canal diameter was wider along the degree of ridge resorption from classes A to E in all dimensions, mainly in the palatal opening (P < 0.01), middle area (P < 0.001), and nasal area. The mean diameter of the enlargement was 1.8 mm, which reached 5.5 +/- 1.08 mm (P < 0.01) in type E bone. In the severely resorbed ridges (classes C through E), when the palatal opening was situated on the ridge, it occupied a mean of 35.6% (13% to 58%) of the area devoted to implant placement. Tooth loss was the main reason for ridge resorption (P < 0.01). Conclusions: Canal diameter enlargement was greater anteriorly to the ridge and posteriorly to the palatal bone, mainly because of tooth extraction. The atrophy of disuse may influence surrounding structures, similar to the maxillary sinus tendency to expand into surrounding bone mainly after tooth loss.