Thomas Peterson Clinical and Laboratory Procedures for Fixed Margin Implant Abutments

Standard, cylindrical abutments were initially used in the treatment of edentulous and partially edentulous patients. These abutments were not designed to simulate the natural emergence profiles of individual teeth. Custom abutments were often the treatment of choice for partially edentulous patients and were successful in replicating the emergence profiles of missing natural teeth. One of the limitations associated with custom abutments is the expense of producing them. Stock, pre-machined abutments with varying emergence profiles were designed to be used in partially edentulous situations, for significantly less cost. These abutments could be modified by restorative dentists and dental laboratory technicians when indicated in terms of margin placement and location, inter-occlusal distance, and retention/resistance form of the abutment preparation. An additional line of abutments with fixed margins that do not need to be modified has also been introduced. This paper presents a clinical and laboratory protocol for using fixed margin, stock abutments. Introduction Since the concept of osseointegration was introduced approximately 40 years ago, the use of osseointegrated endosseous implants has become increasingly more common.1,2 The initial protocol, called for the treatment of edentulous patients with maxillary complete dentures and fixed hybrid screw-retained mandibular tissue integrated prostheses.3 Single tooth replacements using osseointegrated implants were initially discussed in the late 1980’s.4-6 These initial implant restorations were primarily concerned with masticatory function and not aesthetics (Fig. 1). Clinicians and patients were initially satisfied with the return to normal masticatory function and fixed implant restorations. However, clinicians and patients soon expressed interest in the aesthetic replacement of individual missing teeth with implant restorations.7 Standard abutments with cylindrical, non-anatomic emergence profiles were never aesthetically acceptable; they were indeed quite functional. Anatomic, emergence profiles were considered essential for optimal, peri-implant soft tissue contours. Lazzara8, designed three sizes of anatomic-like healing abutments that guided peri-implant soft tissue healing after implants were placed or uncovered. These healing abutments were available in three diameters and multiple heights. The healing abutments replicated the approximate sizes of the teeth being replaced8,9 and generated reasonable peri-implant soft tissue contours for restorations in the aesthetic zone. (Figs. 2 & 3) During the transition from treating edentulous patients to treating partially edentulous patients, custom abutments were the only realistic alternative to develop aesthetic, anatomic-like implant restorations. Custom abutments were expensive for both clinicians and dental laboratory technicians to use in terms of technique sensitivity, expense and labor. Custom abutments were ideal in following soft tissue contours and also for correcting angulations associated with malposed implants. DDS, MS, American Board of Prosthodontics Director, Dental • Research BIOMET 3i, Adjunct Faculty Department of Prosthodontics, Nova SE University, College of Dental Medicine Clinical Science • Section, Editor / The Journal of Prosthodontics [email protected] CDT, MDT President of the • North Shore Dental Laboratories Inc. Member of the Editorial • Review Board for Quintessence of Dental Technology (Figure 1) Radiograph of a screw-retained implant crown on a standard abutment circa, 1987. Note the lack of anatomic emergence profile.