This study aims to compare mandibular overdentures retained either by mini or standard size implants as a treatment for edentulous adults, in terms of patient-reported satisfaction and oral health-related quality of life. We will also evaluate post surgical discomfort, the success rate of prostheses and implants in the long term, denture quality and costs.

Inclusion Criteria:

• Complete edentulism;
• Request of implant stabilization of the existing lower conventional denture;
• Clinically acceptable maxillary and mandibular complete dentures;
• Adequate space in the anterior mandible for the placement of four mini implants and two conventional implants (regular diameter);
• Ability to maintain adequate oral hygiene and clean dentures;
• Systemic health status that permits minor surgical procedures;
• Adequate understanding of written and spoken Portuguese;
• Capacity of giving written informed consent.

Exclusion Criteria:

• Lack of minimum vertical mandibular bone height of 11mm in the interforaminal region;
• Acute or chronic symptoms of parafunctional disorders;
• History of radiation therapy to the orofacial region;
• Specific conditions that may jeopardize the treatment, i.e. alcoholism and smoking;
• Severe/serious illness that requires frequent hospitalization;
• Impaired cognitive function;
• Impossibility to return for evaluations/study recalls.