A potential complicating factor affecting implants is crestal bone loss. The causes of crestal bone loss are attributed to several factors. Among those hypothesized, proof for one or another cause remains obscure. Clinical documentation suggests that implant design may be a key factor. While the evidence is inconclusive, various authors suggest that it is a result of a combination of effects including (1) limited drilling procedure and restricted second-stage surgery 2, (2) rough implant surface in crestal bone 3, (3) microthread design for implant stiffness 4, (4) loading along a conus versus a flat interface 5, and (5) the absence of a significant microgap 6.

The practice of platform switching (e.g. placing a 4 mm diameter abutment on a 5 mm implant seating surface physically moves the inflammatory cell infiltrate zone away from the crestal bone). The growing body of anecdotal platform switch evidence supports this biological width hypothesis. Here the biological width refers to the height of the dento-gingival attachment apparatus around a normal tooth and is defined as the distance necessary for a healthy existence of bone and soft tissue from the most apical extent of a dental restoration.

To formally test this hypothesis the current study has been designed. The Prevail implant has been made with an integrated medialized seating surface that establishes a platform switching function. This implant moves the implant/abutment interface away from the crestal bone and may therefore reduce the amount of bone loss observed in the standard (non-medialized) Osseotite implant design. The objective of this study is to evaluate crestal bone levels adjacent to the implant reference point from the time of implant placement to a period of two years after loading.

Inclusion Criteria:

• Patients of either sex and any race greater than 18 years of age
• Patients for whom a decision has already been made to use dental implants for the restoration of existing edentulism in the mandible or maxilla.
• Patients must be physically able to tolerate conventional surgical and restorative procedures.
• Patients must agree to be evaluated for each study visit, especially the yearly follow-up visits.

Exclusion Criteria:

• Patients with active infection or severe inflammation in the areas intended for implant placement.
• Patients with a > 10 cigarette per day smoking habit.
• Patients with uncontrolled diabetes mellitus.
• Patients with uncontrolled metabolic bone disease where there is a diagnosis of the following: Osteomalacia, primary or secondary hyperparathyroidism, renal osteodystrophy, or Paget's disease of bone.
• Patients with a history of therapeutic radiation to the head
• Patients in need of bone grafting at the site of the intended study implant for augmentation purposes.
• Patients who are known to be pregnant at the screening visit.
• Patients with evidence of severe para-functional habits such as bruxing or clenching