The purpose of this study is to compare the effect of two different implant abutment designs on gum tissue volume changes over time after implant placement.

This is a randomized, prospective, controlled clinical trial comparing the facial gingival profiles around Atlantis™ abutments that have either a linear "divergent" or "concave" transitional profile on the facial and proximal aspect of the abutments.

Sixty study subjects requiring replacement of a single-rooted tooth with an implant-supported restoration will be recruited.

The Osseospeed™ Plus implant will be placed for all 60 subjects, with the use of Uni healing abutments to minimize lateral tissue displacement during healing. After implant placement, but before final impressions are obtained (8 weeks post-placement), subjects will be randomized to either a "divergent" or a "concave" transmucosal abutment design. For fabrication of the experimental abutment, Atlantis™ engineers will initially design a control "divergent" prototype that will be modified with a concavity on the facial and proximal transition zones to obtain an abutment that will otherwise retain all the features of the control abutment. Engineers will measure the linear topographical changes (ΔL=Lc-Ld) of the transition zone, as well as the volumetric change (x) on the mid-facial aspect of the abutment induced by the formation of a submucosal concavity. The primary outcome of the study will be the apico-coronal change of the peri-implant mucosal zenith from prosthesis delivery to one year.

Inclusion Criteria:

• 18 years of age or greater
• Subjects requiring replacement of a single-rooted tooth in the maxillary arch from first premolar to first premolar with an implant-supported restoration
• Teeth adjacent (mesial and distal) to study site must consist of two stable, natural teeth without signs of periodontal bone loss (<2.0mm) and/or significant soft tissue loss
• An opposing dentition with teeth, implants, or fixed prosthesis
• Subjects must be willing to follow instructions related to the study procedures
• Subjects must have read, understood, and signed the informed consent document

Exclusion Criteria:

Exclusion Criteria:

• Insufficient interocclusal space for implant placement and/or restoration at study site
• More than 2.0mm vertical bone loss at study site as measured from the mid-buccal crest of the bone on the adjacent teeth
• Untreated rampant caries
• Tobacco use free for ≤ 6 months
• Liver or kidney disfunction/failure
• Active severe infectious diseases that may affect normal healing and/or bone metabolism (e.g. AIDS)
• Uncontrolled diabetes
• Current alcohol or drug abuse
• Need for systemic corticosteroids or any other medication that would influence post-operative healing and/or osseointegration
• History of relevant head/neck cancer and/or radiation of the head/neck
• Subjects who currently use bisphosphonates or have a history of bisphosphonate use
• Subjects with metabolic bone diseases such as osteoporosis or Paget's disease of bone
• Known pregnancy or nursing mothers
• Unable or unwilling to return for follow-up visits for a period of 1 year
• Unlikely to be able to comply with study procedures according to investigators judgement

The baseline analysis population differs from the final results (i.e., 12 months after baseline), because 7 subjects were lost to follow-up over the course of the study, specifically 4 from the Divergent Allocation and 3 from the Concave Allocation.

1 year