Clinical Investigation of Mandibular Implant Overdenture

Inclusion: * Adult patient; * Male or female; * At least one year of previous conventional complete denture treatment history; * Willing to accept the conditions of the study and informed consent freely given; * Ability to participate for 6 years; * Able to understand and respond to self-reporting measurement scales used in the study; * Minimum 20-mm interarch distance at the estimated vertical dimension of occlusion; * Adequate bone quality; * Adequate bone quantity to accommodate minimally four 3.75-mm diameter by 7-mm long Brånemark implants. Exclusion: * Administrative or physical considerations which would seriously affect the surgical procedure or construe a hindrance for a six-year involvement; * History of drug or alcohol abuse; * Excessive smoking (1+ pack/day); * Uncontrolled systemic disease; * Inability to undergo minor oral surgery because of health or personal reasons; * Irradiated surgical site; * Unrealistic expectations of the prosthodontic treatment outcome; * Psychological or psychiatric conditions that could influence the subject's reaction to treatment; * Acute or chronic TMD problems; * pregnancy; * Class II jaw relationship; * Conventional dental treatment the treatment of choice.