A study designed as a randomized controlled trial of parallel group design will be conducted at the Dental clinic of the University of Valencia to evaluate the influence of 2.5 mm high abutments with different shapes (commercially available high abutments vs high abutments with modified shape to imitate short abutments) on peri-implant bone loss around bone level implants with platform switching in partially edentulous patients that require a fixed rehabilitation supported by two implants in the posterior mandible or maxilla and in fixed rehabilitation supported by one implant in the anterior mandible or maxilla.

A study designed as a randomized controlled trial of parallel group design will be conducted at the Dental clinic of the University of Valencia to evaluate the influence of 2.5 mm high abutments with different shapes (commercially available high abutments vs high abutments with modified shape to imitate short abutments) on peri-implant bone loss around bone level implants with platform switching in partially edentulous patients that require a fixed rehabilitation supported by two implants in the posterior mandible or maxilla and in fixed rehabilitation supported by one implant in the anterior mandible or maxilla (from premolar to premolar).

Inclusion Criteria:

• Any subject requiring two implants in the posterior mandible or maxilla, being at least 18 years old and able to sign an informed consent. Final patient inclusion will be made after flap elevation during the implant placement surgery to be able to confirm the presence of a vertical thickness ≥ 3mm of keratinized soft tissues.
• Bone volumes should allow the placement of implants at least 8 mm long (i.e, 10 mm bone height to the inferior alveolar nerve) and 4.2 mm wide (7 mm wide bone crest) without bone regeneration procedures.
• Patients will be grouped into: 1) non smokers; 2) light smokers (≤ 10 cigarettes/day); 3) heavy smokers (≥ 11 cigarettes/day)

Exclusion Criteria:

• Patients unable to commit to follow-up.
• General contraindications to implant surgery.
• Immuno-suppressed/immune-compromised patients.
• Patients irradiated in the head and/or neck.
• Uncontrolled diabetes.
• Pregnancy or lactation.
• Untreated periodontal disease.
• Poor oral hygiene and motivation.
• Addiction to alcohol or drugs.
• Psychiatric problems and/or unrealistic expectations.
• Patients with an acute infection (abscess) or suppuration in the site intended for implant placement.
• Patients treated or under treatment with intravenous amino-bisphosphonates.
• Patients referred only for implant placement if the follow-up cannot be done at the treatment center.
• Patients participating in other studies, if the present protocol could not be fully adhered to.