"Tunnel" Flap vs Trapezoidal Flap for Lateral Sinus Lift

Participants will record the subjective post-operative pain/discomfort on a daily VAS score (0 to 10) for the first 7 days, at the same time each day, on a specific form. The VAS is a horizontal ruler 10 cm long with the left end (0 cm) indicating "no pain/discomfort at all" and the right limit (10 cm) indicating "the worst pain imaginable. Patients will be also asked to record the need for analgesics (including type and quantity).

Surgical intervention duration (minutes) recorded from incision to the last suture (T1). Times for sinus mucosa elevation (T2) and for sinus filling (T3) will be measured as well.

Soft tissue healing will be evaluated using the scoring reported by Lin SL et al., at two timepoints: at suture removal and at 30 days after suture removal control.

Assessments of wound healing will include 6 scoring categories, namely erythema, exudate, epithelialization, mucosa color, wound contour, and distortion of mucosa. Each category is scored on a 3-point scale (0, 1, or 2) and a total score from 0 to 3 represents good healing, a score from 4 to 6 represents satisfactory healing, a score from 7 to 9 represents disturbance of healing, and a score from 10 to 12 represents poor healing

Possible complications will be evaluated at various timepoints. During the surgical procedure through direct observation (bleeding, sinus membrane perforation, infraorbital nerve injury, perforation of the flap). The day after surgery through a telephone call to the patient (bleeding, flap dehiscence, hematoma, pain). At suture removal control after 10 +/- days after surgery (pain, infections, sinusitis, bone graft displacement, neuropathy, wound dehiscence). At 30 days after suture removal control (pain, infections, sinusitis, bone graft displacement, neuropathy).

A CBCT of the grafted area finalized to implants insertion planning will be taken after 6 months from the sinus lift. The parameters evaluated will be the final alveolar bone graft height calculated in correspondence of a line passing through the centre of the previous bone window; the presence of the contact between the bone graft and the medial or nasal wall of the sinus cavity; the regular distribution of the graft, intended as the presence of voids or displacements. Moreover a biopsy will be taken during implants insertion by means of a trefine.

Bone quality will be evaluated by means of Lekholm Zarb classification, ranging from D1 for dense cortical bone and D4 for fine trabecular bone.

ISQ, ranging from 1 to 100, will be evaluated measuring RFA on two axis (palatal-buccal and mesial-distal) and their mean value will be collected.

Maximum insertion torque will be collected

Peri-implant marginal bone variations (mm) will be measured on Periapical radiograph with a standardized technique will be obtained, using methods already described Marginal bone stability (eg Mameno, Tomoaki, et al. "Risk indicators for marginal bone resorption around implants in function for at least 4 years: A retrospective longitudinal study."Journal of periodontology 91.1 (2020): 37-45.)