Two-Stage Transcrestal Sinus Lift With Osseodensification: Allograft vs Autogenous-Xenograft

Overview

This study is a prospective, randomized, controlled clinical trial comparing two grafting approaches used during two-stage crestal sinus lifting with osseodensification in patients with severely atrophic posterior maxillae (residual bone height ≤ 4 mm). Participants will be randomly allocated in a 1:1 ratio to receive either allograft alone (Group A) or a mixture of autogenous bone and xenograft (Group B). During the first stage, crestal sinus elevation will be performed using osseodensification drills, and the assigned graft material will be placed lncrementally. Cone-beam computed tomography (CBCT) will be performed immediately postoperatively and again after a six-month healing period to assess vertical bone height At the second stage, during implant placement, bone-core biopsies will be harvested for histomorphometric analysis, and implant primary stability will be recorded using insertion torque values.

This randomized controlled trial will be conducted at the Oral and Maxillofacial Surgery (OMFS) Outpatient Clinic, Faculty of Dentistry, Cairo University, Egypt. Eligibility Criteria Inclusion Criteria Participants must: 1. Be 18-70 years old. 2. Have a severely atrophic posterior maxilla with a residual bone height (RBH) of 0-4 mm, confirmed by CBCT. 3. Have an adequate bone width of a minimum of 7 mm. 4. Be in good general health and able to undergo surgery. 5. Provide informed consent and agree to follow the study instructions. Exclusion Criteria Patients with any of the following conditions will be excluded: 1. Uncontrolled systemic diseases, immunosuppression, or a history of head and neck radiotherapy or chemotherapy. 2. Use of bisphosphonates, antiresorptive, or antiangiogenic drugs. 3. Pregnancy. 4. Heavy smoking (\>10 cigarettes/day). 5. Active sinus disease, oral infection, untreated periodontal disease, or severe bruxism. 6. Poor oral hygiene. 7. Anatomical conditions, such as sinus septa or inadequate ridge width, preventing the osseodensification approach. 8. Previous sinus lift or implant failure at the same site. Intervention Preoperative Procedures 1. Patient selection and eligibility confirmation. 2. Screening according to the inclusion and exclusion criteria. 3. Obtaining informed consent from all eligible participants before enrollment. 4. Explaining the study purpose, procedures, risks, and benefits to the patients. 5. Recording the medical and dental history. 6. Clinical and radiographic examination. 7. Randomization of patients into the following groups: Group A: Two-stage crestal sinus lifting with osseodensification using allograft alone. Group B: Two-stage crestal sinus lifting with osseodensification using a combination of autogenous bone and xenograft. Intraoperative Procedures Step 1 A 0.12% chlorhexidine mouth rinse will be used. Local anesthesia will be administered using 4% articaine with epinephrine 1:100,000. A horizontal incision will be made 2-3 mm palatal to the crest, followed by full-thickness flap elevation. The pilot osteotomy will be prepared to the sinus floor using Densah burs at 1000-1100 rpm with copious irrigation. Controlled advancement of 1-2 mm beyond the sinus floor will be performed to elevate the Schneiderian membrane. The graft material will be compacted incrementally (1-mm lifts) using a Densah bur in low-speed counterclockwise (CCW) compaction mode: Group A: Hydrated allograft. Group B: Autogenous bone harvested from an intraoral site (external oblique ridge, chin, or maxillary tuberosity) using an ACM bur and mixed with xenograft. Flap closure will be performed using resorbable 4-0 Vicryl sutures. Immediate postoperative CBCT will be performed to: Confirm membrane integrity. Evaluate graft placement and initial vertical augmentation. Serve as a baseline for subsequent comparison. Step 2 Six-month postoperative CBCT: CBCT will be performed before implant placement to measure: A. The final vertical bone height. B. Graft consolidation and density. C. Implant planning. Bone-core biopsies will be obtained at re-entry using a trephine bur and fixed for histological processing. Histological and histomorphometric analyses will be performed to assess vital bone, residual graft material, marrow tissue, and bone maturation. Implant osteotomy will be performed using osseodensification, followed by implant placement. Primary implant stability will be measured using insertion torque values. Postoperative Care A standard antibiotic and analgesic protocol will be prescribed. Patients will receive instructions regarding oral hygiene and follow-up visits. Outcomes 1. Primary Outcome Vertical bone height after sinus lifting and graft healing, assessed before implant placement. 2. Secondary Outcomes Histomorphometric image analysis of the stained biopsy sections. Implant primary stability at the time of implant placement.