Single-implant Versus Two-implant Mandibular Overdentures

Exclusion Criteria

• •Uncontrolled systemic disease; neurodegenerative disease; osteoporosis requiring antiresorptives.
• •Chronic systemic antibiotics/steroids; bleeding disorders; active cancer therapy; metabolic bone disease; HIV.
• •Investigational drug use within 30 days.
• •Alcohol dependence/illicit drug use; xerostomia (stimulated flow \<0.7 mL/min).
• •Heavy smoking \>20 cigarettes/day.
• •TMD/orofacial pain; severe bruxism; moderate/severe cognitive impairment.
• •Prior implant therapy.
• •Non-adherence risk or inability to attend longitudinal visits.
• •Insufficient prosthetic space for attachment housing: inter-arch vertical distance \<8.5 mm at parasymphyseal/canine region.
• •Concurrent participation in another interventional study.
• •Erosive lichen planus or other significant oral mucosal disease; head-and-neck irradiation history.
• •Mandibular pathology on CBCT (e.g., cyst, tumor).
• •Ridge dimensions \<6 mm width or \<10 mm height at planned sites.
• •Active intraoral infection.