Sinus Lift with Collagenated Porcine Xenograft in Severely Atrophic Posterior Maxillae: Case Series with Histologic Correlation and Long-Term Outcomes

<b>Background:</b> Maxillary sinus floor augmentation is widely used to enable implant placement in the atrophic posterior maxilla, yet comparative data for porcine-derived xenografts remain limited. <b>Objective:</b> To evaluate long-term bone regeneration and implant outcomes following sinus augmentation using a collagenated porcine xenograft. <b>Methods:</b> This paper reports a retrospective case series of three partially edentulous patients (aged 46-56 years) who underwent lateral sinus augmentation with a small-particle collagenated porcine xenograft (THE Graft™, Purgo Biologics, Gyeonggi-do, Republic of Korea) and staged implant placement. In one case, a controlled perforation of the Schneiderian membrane was performed to access and remove a sinus mucocele, followed by repair using a resorbable collagen membrane. Core biopsies were harvested at implant placement for histology (hematoxylin-eosin, Masson-Goldner) and tartrate-resistant acid phosphatase (TRAP) staining. Clinical outcomes included surgical events, vertical bone gain, marginal bone levels, and implant survival at long-term follow-up. <b>Results:</b> Healing was uneventful in all cases. Mean vertical bone gain was 12.0 mm (baseline 1.33 mm to 13.33 mm final). At a mean 46.8-month follow-up (range 38.3-52.2 months), 100% of implants were functional without failure; marginal bone loss remained < 1 mm during the first year and was stable thereafter. Histology at 3.7, 4.7, and 7.5 months showed vascularized new trabecular bone intimately contacting residual xenograft particles (new bone 20-30%, residual biomaterial 30-40%, connective tissue 30-50%). TRAP-positive multinucleated giant cells at 7.5 months indicated ongoing biomaterial degradation without severe inflammatory reactions. <b>Conclusions:</b> Within the limits of a small case series, collagenated porcine xenograft supported predictable bone regeneration and stable long-term implant function after sinus floor elevation, with favorable histologic integration and gradual resorption.