Endoscopic Assessment of Schneiderian Membrane Perforation During Osseodensification-mediated Transcrestal Sinus Floor Elevation With Graftless Immediate Implant Placement in Subsinus Bone Height of 4-6 mm: A Pilot Study, Performed by an Inexperienced OD-surgeon

Inclusion Criteria: * males and females over 21 years of age; * partial edentulism in the posterior maxilla involving 2 or more adjacent teeth in the premolar-molar area; * teeth at the intended implant sites must have been extracted or lost at least 9 months before the date of implant surgery; * sinus floor with a relatively flat contour confirmed on baseline CBCT; * bucco-palatal sinus width (distance between the buccal and palatal walls at 10-mm apical level comprising the residual alveolar crest ) 8-12 mm confirmed on baseline CBCT to minimize the risk of SMP during surgery (Stacchi et al. 2022); * sinus membrane thickness ≤ 2 mm; * subsinus residual bone height (RBH) 4-6 mm at the intended implant sites and bucco-palatal bone width allowing implant placement without bone augmentation procedures. Exclusion Criteria: * systemic conditions contraindicating implant surgery; * pregnancy or lactation; * ongoing or history of pathologies or medications affecting bone metabolism; * ongoing or history of head and neck irradiation; * oral inflammatory and autoimmune diseases; * presence of osseous lesions or persistent infections in the planned implant sites; * previous bone augmentation surgery; * uncontrolled periodontal diseases; * heavy smoking (\> 10 cigarettes/day); * history of sinus surgery; * presence of intrasinus bony septa that could affect membrane elevation and distention; and * ongoing or history of rhinitis or sinusitis.