The posterior maxilla: clinical considerations and current concepts using Brånemark System™ implants

Over a period of more than four decades oral implants have gradually become a substantial alternative in routine dental treatment planning and should today be looked upon as an indispensable part of a dentist s everyday life. From being initially an exclusive treatment option for the totally edentulous patient (22), oral implants are today often considered the treatment of choice in partial edentulism, as well (10, 18, 72). For many years, strict standardized treatment protocols on implant site preparation and extension of healing periods were followed meticulously, according to the guidelines described by Adell et al. (3). With special reference to the Brånemark System implants (Nobel Biocare AB, Göteborg, Sweden), the surface was turned and the surgery was a two-stage procedure for all clinical situations. A number of prospective multicenter studies showed the excellent clinical behaviour of these implants (36, 49, 52, 56, 57, 106). Over time, implant components were modified to facilitate and ⁄ or improve their performance. The implant macro-design was altered stepwise from a standard screw shape to a self-tapping and sometimes tapered geometry and the implant micro-design was altered from the turned to an oxidized, moderately rough surface (TiUnite, Nobel Biocare AB). The latter was in line with the findings of Wennerberg (105), who stated that the early bone response was optimized when facing an implant surface roughness (Sa-value) of 1.0–1.5 lm. (Sa is the arithmetic mean of the absolute values of the surface departures from a mean plane within the sampling area.) The surgical technique, especially in the mandible, has gradually become a one-stage procedure with early or immediate loading. The pioneering work in this context was performed by Schnitman et al. (88), who inserted additional implants to be loaded immediately. They used a two-stage procedure for the majority of implants, but to meet the patient demand of an immediate fixed construction, some extra implants were placed to be at service during the healing period. Obviously the authors did not think of these as useful implants in the long term. However, the 10-year report (89) demonstrated an 85% survival rate for the immediately loaded implants. A similar approach was used by Tarnow et al. (94) and Wolfinger et al. (108). Today, a great number of publications demonstrate the 1to 5-year results with Brånemark System implants that have been either early loaded (14, 27, 28, 34, 80) or immediately loaded (1, 20, 26, 47, 67) in fully edentulous mandibles. The clinical outcome is most encouraging for these procedures, which is why other treatment situations have been tested. For the fully edentulous maxilla, reports are showing survival rates of 93–100% during the first year of function for early (75) or immediately loaded implants (13, 68, 76, 98). In partially edentulous patients the corresponding figures are in accordance with those of the fully edentulous maxillae for early loaded (39, 65, 100) and immediately loaded implants (4, 25, 41, 86, 101). In situations where there is a low bone density, i.e. quality 4 bone (59), the primary implant stability may be jeopardized; to overcome this problem various surgical techniques have been proposed, using osteotomes, narrow and ⁄ or half-way implant site preparations (4, 11, 30–33, 37, 66, 91, 93, 102). With the introduction of resonance frequency analysis