The Treatment of Implant-retained Mandibular Overdentures for Edentulous Patients

Inclusion Criteria: 1. Being edentulous in the upper and lower jaw for at least 1 year 2. Dissatisfied or cannot function with their complete lower denture 3. Age between 40 and 75 4. Suitable bone quality as assessed radiographically (CBCT) according to Zarb's classification。 Exclusion Criteria: 1. Physical and mental disabilities which interfere with the maintenance of implants; 2. Severe skeletal jaw discrepancies (class III) 3. Those who have already received or lost dental implants 4. Those who abuse drugs or alcohol 5. Smoking more than 10 cigarettes a day 6. Having received radiotherapy to the head and neck region for malignancies 7. Undergoing chemotherapy 8. On long-term therapy with steroids 9. immunosuppressants or biphosphonates 10. Insulin-dependent diabetic patients and uncontrolled onset diabetic patients 11. Those affected by chronic renal or liver disease 12. Systemic and local bone disorders and pathology 13. Serious cardiac and pulmonary disorders 14. Haemophilic disorders who are susceptible for increased bleeding and tendency for post-operative infections 15. Those who are at risk of developing bacterial endocarditis 16. Immune system compromised patients, including those with HIV