The optional apex sites for quad zygomatic implant placement in edentulous patients with severe alveolar bone resorption: a CBCT anatomical analysis.

Objective: To investigate the difference in bone-implant contact (BIC) and the rate of infratemporal fossa intrusion among different apex sites for quad zygomatic implants (ZIs) design in edentulous patients with severe alveolar bone resorption.

Methods: Patients with maxillary edentulism were evaluated. Alveolar bone resorption was assessed using the Cawood and Howell classification. Participants with Class IV or Class V/VI bone resorption were selected. The zygomatic bone was devided into upper, middle and lower thirds, with four potential implant apex locations identified in each third. Virtual planning for quad ZIs, along with measurements of BIC were performed. Additionally, the occurrence of ZIs intrusion into the infratemporal fossa was examined, and the distance between ZI and orbital cavity was measured.

Results: A total of 28 CBCT scans of edentulous patients, encompassing 56 zygomas, were analyzed. Thirty-nine single lateral posterior edentulous jaws were classified into Class IV subgroup, while 17 into Class V/IV subgroup. Among all patients and patients in subgroups, the anterior and posterior ZI exhibited the highest BIC at points A3 and B2, respectively. The average zygomatic BIC at A3 apex point was 18.3 ± 3.9 mm, and that at the B2 apex point was 16.3 ± 5.3 mm. Quad ZIs risk intrusion into the infratemporal fossa when positioned at B2, B3, and at all apex points of the lower zygoma segment. Three anterior ZIs at A3 point show less than 1 mm distance to orbital cavity. Overall, A3 and B1 apex points showed high BIC and low infratemporal intrusion rate for quad ZIs, irrespective of patient's alveolar bone resorption status.

Conclusions: The optional apex point for anterior and posterior quad ZIs is A3 and B1, respectively, regardless of the patients's alveolar bone resorption level. Alveolar bone resorption does not affect the BIC for quad ZIs. Anterior ZI positioned at A3 point may present high risk for orbital penetration and may not be reccomended in a Quad ZI approach.

Trial registration: The clinical research is registered under the number ChiCTR2100044472.