Scientific study

Microscope-Controlled Internal Sinus Floor Elevation (MCI-SFE): A new technique to evaluate the sinus membrane during transcrestal lifting

2 June 2023 · 15 min read
Author Behnam Shakibaie, Dr. med. dent., MS Tehran, Iran

Original Title

Microscope-Controlled Internal Sinus Floor Elevation (MCI-SFE): A new technique to evaluate the sinus membrane during transcrestal lifting


Behnam Shakibaie DDS, MSc, OMFS. Microscope-Controlled Internal Sinus Floor Elevation (MCI-SFE): A new technique to evaluate the sinus membrane during transcrestal lifting. The international journal of Microdentistry, 2013


Transcrestal (or “internal”) sinus floor elevation (SFE) can be performed when the residual alveolar ridge has adequate vertical (≥6 mm; sa1 and sa3 as classified by Misch) and horizontal dimensions. although this surgical technique is currently established, it has two shortcomings. first, internal SFE is considered a “blind” approach as far as verification of the elevated osteomucosal layer on the sinus floor is concerned. also, no guidelines supported by scientific evidence are currently available as to the vertical dimension that can be attained by elevation and grafting without injuring this osteomucosal layer.

The present investigation explains a new visual controlling method during evaluation of the osteomucosal layer on the sinus floor, which is based on the use of high-powered optical magnification and accordingly has been termed “microscope-controlled internal” SFE (MCI-SFE), and also examines the influence of elevation heights on the frequency of perforation and other complications during and after SFE.

Fifty-nine internal SFE procedures were verified with this technique in 43 patients, who were divided into three study groups depending on the planned height of elevation and they received a total of 60 implants.

The clinical and radiographic results of this study demonstrated that the risk of injury to the osteomucosal layer and the associated risk of incurring additional complications such as implant loss and sinusitis would increase significantly in the presence of elevation and grafting heights of ≥4 mm.

Whenever possible, therefore, elevation of the sinus floor in internal SFE procedures should be less than 4 mm. using an operating microscope for visual inspection of the osteomucosal layer of the sinus floor improves surgical success and contributes to better outcomes of internal SFE. Int J Microdent 2013;4:**–**

Materials and Methods

From December 2006 through April 2009, 43 patients underwent surgery within the scope of an in-house investigation into microscope-controlled internal SFE (MCI-SFE) performed at a private clinic in Germany. The mean age of these 43 patients was 39 years (17 men, 26 women). Only 6 smokers were included in this sample, all of whom reported that they smoked ≤10 cigarettes a day. Their distribution across the three study groups was 3/2/1 (groups 1/2/3). All patients presented with a health status not including any systemic or local contraindications to oral surgery.

Periapical radiographs using the right-angle technique and cone-beam computed tomography (CBCT) scans were obtained for preoperative assessment. The surgical procedures were planned with three-dimensional planning software (coDiagnostiX; IVS-Solutions, Chemnitz, Germany). Baseline findings at the surgical sites ranged from 5.3 to 8.2 mm in the transversal plane. Residual ridge heights were found to vary between 4.3 and 10. 4 mm (SA1 andSA3 as classified by Misch). All procedures were conducted with an operating microscope (OPMI PROergo®; ZEISS, Oberkochen, Germany) for visual inspection of the Schneiderian membrane.

Elevation of the sinus floor was accomplished with osteotomes (Camlog; Altatec, Wimsheim, Germany). Group 1 included cases of elevation ≤2 mm, group 2 cases ranging from 2 to 4 mm, and group 3 cases exceeding 4 mm of elevation. Group 1 included 16 patients with 21 MCI-SFE procedures and simultaneous placement of 21 implants 3.8−5.0 mm in diameter and 9−11 mm in length (Camlog Screw-Line; Altatec, Wimsheim, Germany). Group 2 included 14 patients with 20 MCISFE procedures and simultaneous placement of 20 implants. Group 3 included 13 patients with 18 MCISFE procedures and simultaneous placement of 19 implants.

Following the introduction of xenogeneic matrix (Bio-Oss; Geistlich, Wolhusen, Switzerland) and rinsing with isotonic saline, the osteomucosal layer was visually inspected using the operating microscope at a magnification of ×5 to ×15. Once the site was verified, the implants were immediately placed. Radiographic verification (via periapical films using the right-angle technique) was obtained immediately after the procedure and 3 to 5 months postoperatively (i.e., before the restorative phase was started). For implants exhibiting a primary stability of >25 Ncm, a non-submerged integration protocol was adopted, while in cases of <25Ncm a submerged protocol was used. Implants left to integrate under the submerged protocol were surgically exposed after 2 to 3 months. Implants were evaluated by resonance frequency analysis (Osstell; Integration Diagnostics AB, Göteborg, Sweden) for osseointegration 3 to 5 months after placement. At this point, the restorative treatment phase was finalized by delivering single-tooth restorations. Follow-up examinations were generally performed around 4 and 8 months after prosthetic delivery.


Microscopically visible perforations of the osteomucosal layer were exclusively noted in groups 2 and 3. No perforations were observed in group 1, which involved elevation of the sinus floor by no more than 2 mm. The postoperative radiographs in groups 1 and 2 revealed subantral grafting heights of 0.5−1.5 mm above the implant apex, based on all patients and implants that were not associated with perforations. Judging from the postoperative radiographs, no augmentation above the implant apex was observed when a perforation had occurred. Some of the postoperative images showed a mucosal layer above the implant apex within the sinus cavity, and some revealed no tissue structure in this area. Interesting and unexpected findings with regard to the height and shape of subantral augmentation were notably seen in group 3, which involved elevation of the sinus floor by ≥4 mm up to a maximum of 8 mm.

In group 1, all implants placed simultaneously with the MCI-SFE procedure easily achieved osseointegration and could be loaded after 3 to 5 months as scheduled. Also, the clinical follow-up examinations performed 4 and 8 months after delivery of the prosthetic restorations did not reveal any abnormalities among the patients in this group.

Group 2 revealed a total of 2 (10%) microscopically visible perforations of the osteomucosal layer based on 20 MCI-SFE procedures and implants. Two patients in this group were affected: one woman reported a sensation of pressure on the treated side of the alveolar ridge 4 days postoperatively, associated with persistent pain radiating up to the orbit. Her symptoms gradually improved after 2 weeks of analgesic and antibiotic treatment using ibuprofen 800 mg (Ratiopharm, Ulm, Germany) and amoxicillin 1500 mg (Ratiopharm). However, the implant was found to lack osseointegration 3 months after the procedure (during second-stage surgery for implant exposure) and had to be removed. The second perforation, observed in a male patient, was not associated with any sequelae by the end of the study. Likewise, the clinical course also remained uneventful in all other patients of this group right down to the second follow up examination after prosthetic delivery.

Group 3 revealed 5 microscopically visible perforations of the osteomucosal layer in 4 patients. Three of these patients developed symptoms similar to the ones experienced by the patient in group 2. Two of them, however, additionally showed nasal secretion with pus in the wake of perforation, which resolved under antibiotic treatment with amoxicillin 1500 mg (Ratiopharm). In addition, the same patients presented with postoperative nasal bleeding on the treated side, which could be arrested by tamponade of the nasal meatus affected. Two of the patients who revealed symptoms of sinusitis lost their implants within 3 days of the procedure. One of these implants was removed during the second-stage procedure scheduled for implant exposure, while the second implant was explanted because of mobility after 1 month of transmucosal healing. The remaining case of implant removal during second-stage surgery in group 3 had not been pre-ceded by an intraoperative finding of osteomucosal layer perforation.

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