L'élévation du plancher sinusien externe guidée par microscope (MGES) - une nouvelle technique chirurgicale mini-invasive

Microscope-guided external sinus floor elevation (MGES) – a new minimally invasive surgical Technique

Behnam Shakibaie, Dr. med. dent., MS. Microscope-guided external sinus floor elevation (MGES) – a new minimally invasive surgical technique. Implantologie, Vol.16, p.21-30, mars 2008

Dental authors have considered the accidental perforation of Schneider's membrane the most serious complication of external sinus floor elevation. A sinus lift procedure with concurrent immediate implant placement (single-step procedure) has been judged equally risky in advanced atrophy of the alveolar ridge (categories SA3 and SA4 according to Misch). To reduce the incidence of membrane ruptures and to preserve the local vestibular alveolar bone, alternative surgical techniques have been introduced, notably the internal sinus lift according to Tatum and Summers, the balloon dilatation method according to Benner or the endoscopic technique according to Baumann and Ewers. The need for pressure-guided osteoelevation may diminish patient compliance. Missing or incomplete visual verification of the membrane elevation may reduce the scope of the clinical application of these methods.

Using specially developed microsurgical instruments under optical magnification (surgical microscope or magnifying glass) and optimized illumination, the external access to the maxillary sinus can be kept small while at the same time significantly reducing the membrane perforation rate (1/20, 5%). This protects the vestibular alveolar bone, increasing the primary stability of concurrently placed implants, improving the supply of nutrients to the subantral bone graft, and reducing the postoperative complication rate.

These results were obtained in a prospective in-office study on 17 patients on which 20 microscope-guided single-step external sinus floor elevation procedures were performed.

Between October 2005 and June 2007, 20 sinuses of 17 patients were surgically treated according to the method described here within the framework of an in-office study, and 38 implants were inserted in single-step procedures. The medical history of all patients was without significant findings. The patients were between 32 and 68 years old; all were non-smokers. Out of the seventeen patients, eleven were female and six were male. Eight patients received pre-implantological periodontal treatment. In eleven patients, fresh extraction sockets were treated according to the socket preservation technique using Bio-Oss^® granules (Geistlich, Wolhusen, Switzerland) and Stypro^® resorbable hemostatic sponge material (Curasan, Kleinostheim, Germany).

Radiological diagnostics included OPGs and intraoral radiographs in nine patients and CT scans and OPG in eight patients. The data of patients examined by computed tomography were analyzed three dimensionally using the coDiagnostiX^® implant planning software (IVS Solutions, Chemnitz, Germany). The results of the 3D analyses were used to create intraoperative drilling stents. The baseline bone situation showed advanced atrophies of the alveolar ridge in all cases, with residual crestal bone heights of 0 to 8 mm (categories SA3 and SA4 according to Misch).

All sinus lift operations were performed under the OPMI PROergo^® surgical microscope (ZEISS, Oberkochen, Germany) using newly developed microsurgical sinus lift instruments (Helmut Zepf Medizintechnik/DCV, Seitingen, Germany). The surgical protocol was the same for all patients. Where more than two implants were to be inserted simultaneously, an additional fenestration was made for maximum intraoperative visibility. All patients received Camlog implants (Screw line and Root line; Camlog Biotechnologies, Wimsheim, Germany) with diameters between 3.8 and 5.0 mm and lengths between 9 and 13 mm. No additional lateral augmentation was performed. The bone-augmentation material used was a mixture of autologous bone (Crista zygomaticoalveolaris) and Bio-Oss^® granules.

Once the augmentation was completed, all sinus lift windows were covered with multiple layers of Bio-Gide^® membrane (Geistlich, Wolhusen, Switzerland) to provide for guided bone regeneration (GBR). No additional pin fixation was performed. Patients were concomitantly medicated as follows:

1. Clindamycin 300 mg, three times daily from the first preoperative day to the third post operative day;
2. Prednisolone 10 mg (Acis, Oberhaching, Germany), 20 mg on the first preoperative day and 10 mg daily from day of the operation to the third postoperative day;
3. Novalgin drops (Aventis, Frankfurt, Germany) postoperatively as needed, 15 to 20 drops at eight-hour intervals.

All patients were instructed not to engage in sports and to refrain from wearing their dentures for up to one week postoperatively. The first postoperative control was two days after the procedure; the sutures were removed on the tenth day postoperatively.

By taking measures for socket preservation after tooth extraction as described above, using Bio-Oss^® granulate and Stypro^® resorbable hemostatic sponge material, the three-dimensional morphology of the alveolar limbus could be largely preserved prior to implant placement. The crestal keratinized soft-tissue profile obtained after socket preservation proved particularly useful at the time of implant placement.

General and local postoperative healing was generally uneventful in all patients, both following extraction and socket preservation and following sinus floor augmentation and implant insertion. There was only one case of membrane perforation (1/20, 5%), in the mesiocaudal region of the sinus window; it could be resealed safely by application of a contoured Bio-Gide® membrane. The operation could be continued and completed according to protocol.

Without the concurrent implantation, the sinus lift procedures took between 30 and 60 minutes. The longest operations were those where more than two implants were inserted at the same time, and two sinus windows were prepared. Once the operator has gained a certain routine, one sinus floor elevation (with one window) plus the insertion of one or two implants takes no more than 40 minutes. Primary stability (25 to 35 Ncm) was achieved in all but six implants, where primary stability was 15 to 20 Ncm.

A nine-month healing period was provided for these latter implants, while the healing period for all other implants was five to six months. All implants were allowed to heal subgingivally. There were no significant findings during the radiological controls performed to date – immediately postoperatively, prior to exposure, six weeks after exposure, immediately prior to insertion of the prosthetic superstructure, six months later, and one year later.

Of the 38 implants inserted, 27 have been exposed to date and restored following complete osseointegration. Osseointegration and implant stability were checked by resonance frequency analysis (RSA) using the Osstell^® unit (Integration Diagnostics, Göteborg, Sweden). The osseointegration of the implants was examined radiologically by OPGs or conventional intraoral radiographs at the relevant stages. The remaining implants are still in the healing phase at the time of this writing.