Crestal Hydraulic Sinus Lift with Simultaneous Implant Insertion: A Retrospective Case Series

<b>Objectives</b>: This retrospective study aimed to evaluate the increase in vertical bone height following sinus lift procedures using the CAS (Crestal Approach Sinus) kit technique in combination with tissue-level implants. Additionally, the quantity of bone between the implant apex and the Schneiderian membrane was assessed to determine the effectiveness and safety of this minimally invasive approach. <b>Methods</b>: The study included 15 patients (20 implants) who underwent sinus lift procedures with the CAS kit technique and tissue-level implants in the posterior maxilla between September 2021 and October 2024. Inclusion criteria required a minimum residual bone height (RBH) of 2 mm. Cone-beam computed tomography (CBCT) scans were used for initial screening, and panoramic radiography evaluated outcomes at implant placement and nine months postoperatively. Primary outcomes included implant and prosthetic survival rates, as well as biological and technical complications. Secondary outcomes were vertical bone height and the amount of bone above the implant tip. Statistical analyses were conducted using the Wilcoxon signed-rank test with a significance level of 0.05. <b>Results</b>: All implants achieved successful osseointegration, with no implant or prosthetic failures and no biological or technical complications reported. The mean RBH at implant placement was 4.2 ± 1.4 mm, which increased to an overall membrane elevation of 13.8 ± 1.8 mm. At the 9-month follow-up, the overall membrane elevation was slightly reduced to 13.0 ± 1.6 mm (<i>p</i> = 0.000), with a mean bone gain of 9.6 ± 2.4 mm. The amount of bone above the implant tip was 3.4 ± 1.7 mm at placement, decreasing to 3.0 ± 1.2 mm at follow-up (<i>p</i> = 0.007). <b>Conclusions</b>: The CAS kit technique combined with tissue-level implants demonstrated significant vertical bone gain and high implant survival rates without complications. This minimally invasive approach proved effective and safe for sinus augmentation in patients with limited residual bone height. The findings support the CAS kit's potential as a preferred technique for maxillary sinus elevation. Further research with larger cohorts and long-term follow-up is needed to validate these results.