David Chan demonstrates a simple solution to the difficult problem of insufficient posterior maxillary bone

We are often presented with patients who meet the criteria for implant treatment, but have insufficient bone, in quantity and quality, in the posterior maxilla. Conventional sinus floor elevation (CSFE) may address the problem but it is often expensive, time-consuming and associated with high morbidity. The internal sinus lift, also known as Summer’s method, or osteotome sinus floor elevation (OSFE), uses a crestal or transalveolar approach to augment the sinus floor rather than the lateral window (Caldwell-Luc) approach used in CSFE (Summers, 1998). Various modifications to the original method have been described in the literature (Chen and Cha, 2005). It is used mainly to locally augment the height of the alveolar bone in the posterior maxilla, so that a single and longer implant can be placed simultaneously. An internal sinus lift is more technique sensitive but it produces less morbidity by avoiding the elevation of a muco-periosteal flap and the cutting of a lateral window. However, conventional and osteotome techniques are only possible without the presence of a vertical sinus septum. In CSFE, the presence of a vertical septum on the lateral wall will either complicate the opening of a lateral window, or make the process almost impossible. In OSFE, impact force from a mallet may break the fragile septum and tear the membrane. This case report intends to introduce a two-stage method of OSFE without the use of impact force or specialised tools, and make the OSFE technique simpler and more predictable, even in difficult anatomical situations.

Method

Cone beam computed tomography (CBCT) imaging is essential for any planned sinus floor elevations. It is also better to take the CBCT volumetric image in a higher resolution. A CBCT image: • Provides a three-dimensional picture of the site • Provides greater appreciation of the local anatomy • Discloses any pathology in the sinus • Provides measurements of • Can be used to produce drilling guides. Although the OSFE technique has been successful in patients with residual alveolar bone height of less than 3mm, 3-6mm is considered to be more appropriate for providing better initial fixation (Emmerich et al, 2005). The presence of any sinus infection is a contra-indication to OSFE and should be treated before this procedure.

Surgical protocol – first stage

1. A crestal incision is made to raise a muco-periosteal flap to expose the crestal alveolar bone 2. The osteotomy site is prepared as normal with the final drill to 1mm short of the sinus floor 3. The final drill is then run at a very slow speed (30-40rpm) to the full thickness of the floor in order to intentionally perforate the floor (Figure 2) 4. The osteotomy is then covered with a resorbable membrane 5. The buccal flap is relieved to allow tension-free suturing and healing by first intention 6. The site is then left to heal over four weeks

Second stage

1. The site is revisited. A partial mucoperiosteal flap is raised again and separated cleanly from the underlying immature bone 2. An osteotome similar in diameter to the last drill is used to push the healing content of the previous osteotomy apically, lifting the Schneiderian membrane from the sinus floor. The osteotome should never poke through the bone or come into contact with the membrane 3. Particulate graft Bio-Oss (Geistlich Biomaterials, 2012) is then introduced into the vacated osteotomy 4. The same osteotome is used again to push the Bio-Oss apically (Figure 3) 5. This process is repeated four or five times, depending on the amount of elevation desired 6. A periapical radiograph is taken after the first load of Bio-Oss to check for the patency of the membrane 7. No drilling is necessary and under-sized site forming with osteotomes is desirable 8. A selected implant is then placed in the osteotomy 9. Submerged healing for eight weeks is advisable before restoration.

Case study

A healthy 44-year-old woman presented, requiring implant placement at the posterior maxilla. Radiographs revealed the presence of a vertical sinus septum at the intended site of placement. Using the above two-stage OSFE technique, an implant was successfully placed at UL6 (Figures 2 and 4-6). No drilling was necessary in the second ‘push up’ stage. A Straumann bone level implant was placed at bone level rather than subcrestally, in case it was lost in the sinus (Figure 5). After three months, healing was complete (Figure 6) and an open tray impression was taken for the fabrication of a fixed prosthesis.

Discussion

Osteotome sinus floor elevation (OSFE) is well documented in literature for increasing the alveolar bone height in the posterior atrophic maxilla. Ideally, the height of the residual ridge should be about 3-6 mm to provide proper fixation for the implant (Greenstein and Cavallaro, 2011, Emmerich et al, 2005). The sinus floor should preferably be flat in the mesio-distal and bucco-lingual directions without an intervening septum. Impact from a mallet on a particulate graft introduced into the osteotomy causes infracture of the sinus floor and lifts the overlying Schneiderian membrane (Buser et al, 2007). The osteotome should never extend beyond the bone or come into contact with the Schneiderian membrane to avoid tearing it. In contrast with the lateral window approach, where more time (four to five months) is required for the osseointegration, the implant inserted by OSFE technique is ready for restoration after eight weeks. This can be explained by the fact that the presence of thicker natural bone is a prerequisite for the osteotome technique, which provides better fixation. Although a greater gain in height is reported in the literature using the OSFE technique, a height of 5-7mm is more practical and can be safely achievable. The success rate of implants placed in the OSFE augmented ridge is comparable to those placed in other part of the mouth. The success rate has been put at 95-96% in a systematic review and meta-analysis by Emmerich et al (2005) and 92.8% by Tan et al (2008). However, statistical analysis is not possible due to the multivariate nature of the techniques, grafting materials and type of implants used. Over the years many modifications to the original OSFE technique such as the hydropneumatic balloon elevation technique, or Dask technique have been proposed. The purchase of additional expensive tools is required and the dentist has to develop new skills for their use. The method described in this case report offers a simple solution to a difficult problem using existing tools available in an average implant practice. The ‘push up’ technique described in this case report makes use of the fact that bone healing always lags behind the healing of the Schneiderian membrane, and that early osteoid tissue is soft and can be manipulated with an osteotome using gentle pushing pressure only. A gentle and apical pressure on this osteoid tissue lifts the overlying membrane easily (Figure 3). Timing is crucial in this technique. In the absent of infection, the Schneiderian membrane heals two weeks after the osteotomy and hard bone is present in the same site after eight weeks. The ideal time for the second ‘push up’ stage is in the fifth week. The immature woven bone eventually calcifies with the rest of the particulate graft (Figure 6). This technique is not affected by the difficult anatomy at the intended site such as sloping sinus floor and the presence of a septum (Ulm et al, 1995; Krennmair et al, 1997, Maestre-Ferrín et al, 2010). Benign paroxysmal positional vertigo (BPPV) has been noted as one of the side effects of the osteotome technique, in addition to other complications such as membrane perforation, or loss of the particulate graft or implant into the sinus (Kim et al, 2010; Di Girolamo et al, 2005). The use of impact force is not necessary with this technique and the incidence of BPPV can be avoided. However, the sinus must be free from infection before using this technique. The deliberate creation of an oro-antral communication (OAC) must be done using aseptic procedures. An extra visit is necessary for this twostage technique and the patient must be able to attend in the specified time period. Membrane binding and tearing is possible during the internal membrane elevation and this should be checked with a postoperative periapical radiograph.

Conclusion

The technique described in this case report offers a new way of elevating the sinus membrane with osteotomes, in difficult anatomical situations such as a sloping sinus floor and the present of a sinus septum. With proper planning, the technique can be incorporated during the extraction stage of the treatment. The use of impact forces is avoided and this modified OSFE technique may be more acceptable to the patients.

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