There is often an inadequate bone for implant positioning in the posterior maxilla because of either pneumatization of the maxillary sinus or osseous resorption, or both. Osseous resorption that affects edentulous ridges is mainly associated with the presence of previous periodontal or periapical lesions, traumatic extraction, or pressure exerted by dentures. It may even be the result of hypofunction 1. Pneumatization of the maxillary sinus corresponds to the displacement of the sinus floor toward the ridge crest. Thus, there is a resultant decrease in the available bone height, which disfavors prognosis and prevents implant placement 2. In order to overcome this, the use of implants along with sinus lift procedures has been recommended.
Some clinicians recommend placing implants at the time the sinus is augmented 3. They recommend placing the graft through a lateral osseous window in the anterior sinus wall (lateral antrostomy). A lateral access window shows more consolidated outcomes, although it is a very traumatic and complex technique to perform. In contrast, Summers 4 described a simpler and less invasive technique using an osteotome, but it requires at least 5 mm of residual bone height for initial stability and long-term success of the implants. Nevertheless, there is a higher risk of antral membrane rupture from the osteotome pressure 5–9.
In, 2010, Fernando and Partata 10 reported a modification of Summers osteotomy technique by connective tissue graft interposition in order to weaken the impact of sinus cortical fracture, and therefore prevent antral membrane perforations.
Augmentation procedures have been achieved either by placing material in direct contact with the antral membrane or by creating new cavity using a sinus partitioning technique 11. The latter is recommended to create a stable site for grafting. It has the advantage of being safely packed and densified with bone particles and/or biomaterials. It also provides protection for the sinus membrane, which may be perforated by the lifting procedure, and prevents the migration of the grafting material into the sinus. Guillaume 11 used a thin strip of β-tricalcium phosphate (β-TCP) to partition the cavity from the sinus membrane, and called it ‘sinus up’. It is 100% synthetic, rapidly osseointegrated by direct bone apposition 11. He found that the material is well integrated into the maxillary bone, ensuring total rigidity for this synthetic substance.
Aim of the study
Considering such controversy and discussions, this study was carried out in an attempt to evaluate and compare between the modified Summers technique (osteotome technique) and Bernard (sinus up technique) in augmentation of the maxillary posterior region for the placement of dental implants in atrophied ridges.
Twelve patients, 35–45 years old, presented to the clinic for implant rehabilitation in the maxillary premolar–molar region. There were 10 men and two women. Cephalostats showed maxillary sinus pneumatization with remaining bone height of ∼5 mm (Fig. 1a). All patients were in good systemic health and did not smoke. Appropriate oral hygiene was evident and there were no signs of periodontal disease or maxillary sinus infection. Half of the patients were managed by the modified Summers osteotome technique 4 and the remaining by the sinus up technique 11.
Modified Summers osteotome technique
On the day of surgery, after patient evaluation and preparation for surgery as usual, an injection of 2% mepivacaine HCL and adrenaline 1 : 100 000 was administered. An incision was made on the crest of the alveolar ridge with other releasing incisions, after which a full mucoperiosteal flap was reflected beyond the mucogingival junction. The receptor site was initially prepared using a sequence of drills suggested by the manufacturer under copious irrigation with a sterile saline solution. Drilling stopped up to the bounds of the sinus floor bone plate, which was about 4 mm in depth and 3 mm in diameter.
Afterwards, a small fragment of connective tissue was removed from the inner side of the palatal incision and inserted into the prepared receptor site. It functioned as a cushion under the osteotome to avoid sinus floor fracture during osteotome maneuver. The connective tissue graft was left in the sinus. Next, bone from the buccal cortical plate of the alveolar bone was harvested, blended in a 1 : 1 ratio with a Bio-Oss bone substitute (Osteohealth, Shirly, New York, USA), and inserted in small portions into the sinus using a suitable elevator. A 3.5/15 mm implant (Fig. 1b) was then positioned. The flap was repositioned and sutured with 3.0 silk sutures, which were removed 7 days after surgery. A suitable antibiotic such as amoxicilline 500 mg was administered three times a day for 7 days, beginning 1 h before surgery, along with chlorhexidine 0.12% mouth wash to be used for 1 min twice a day. Analgesic was also prescribed in pain or discomfort.
Guillaume technique (sinus up technique)
Lateral osseous window sinus augmentation was achieved by creating a new cavity between the antral floor and the remaining alveolar bone using a sinus partitioning with sinus up material (Fig. 2). This cavity was filled with high-porosity β-TCP synthetic granules (Fig. 3). With this partition, when the membrane is damaged, filler material cannot migrate into the sinus. Sinus up material is also made from β-TCP in its β form, currently used for orthopedic maxillofacial surgery. It has an osteocompatible nature that allows it to be entirely integrated into the buccal wall without inducing any inflammatory reaction in the elevated sinus membrane. It is supplied in sterile packaging, in 40 mm×25 mm×2 mm thick rectangular strips, with solid edges and a perforated central area (Fig. 4), and can be sculpted to the exact dimensions of the sinus cavity 12.
Depending on the height of residual bone, implants are placed immediately or delayed for a few months. In the present study, all implants were stabilized in concomitance with the augmentation procedure. Precise sinus computed tomography (CT) scan data were used to identify and trace the exact perimeter of the new floor and to precisely measure the residual bone height. Sinus up strips were grinded and fitted to the exact shape of the sinus walls with the aid of a suitable ancillary for gentle grinding (Fig. 5). The material was inserted horizontally at the appropriate sinus height, generally 15 mm from the sinus floor, which is a suitable position for secondary implant placement. It was stabilized so that it formed a new floor. The flap was repositioned and sutured, and patients were given instructions and medicines as usual.
Modified Summers osteotome technique
Good bone filling was assured immediately after surgery, with maxillary sinus floor elevation without membrane rupture (Fig. 1a). Bone increase was further observed around the dental implant (Fig. 1c) during the 1- and 2-year follow-ups after the initial operation. No signs or symptoms of infection were observed during the 2-year follow-up. There were no failures of implants. The success rate of this method was 100%.
Guillaume sinus up technique
CT scan checks (Fig. 6) confirmed the complete absence of a membrane inflammatory reaction to the sinus up material. Clinical examination showed that sinus up was well integrated into the maxillary bone, ensuring total rigidity of this synthetic graft (Fig. 7). No failures of cases were noted during the 2-year follow-up period.
The maxillary posterior region is often a problem area for the placement of implants. The advanced resorption of the alveolar bone is combined with an increase in pneumatization of the maxillary sinus because of the higher air pressure in the pneumatized sinus cavities. Furthermore, the spongy nature, of the bone found in the posterior maxilla covered with thin cortical rim, makes the use of short implants in this poor bone quality region difficult and does not seem to be advisable. Therefore, the elevation of the Schneiderian membrane for augmentation of the maxillary sinus as a possible way of restoring this problematic region was described 3.
The purpose of this clinical study was to compare two different methods of sinus elevation with respect to possible bone increase and resulting final bone heights: the Summers osteotome technique 4 and the Guillaume sinus up technique 11.
The success rate of the osteotome technique is comparable to that reported for implants placed in a conventional manner. It is even better than the success rate for implants placed in type IV bone quality 13. This may be attributed to the favorable influence of the osteotome technique with respect to implant bed preparation, in as much as the medullary compartments are compressed. This provides better initial stability and perhaps a greater implant-to-bone contact area.
The advantages of this method are that it is less invasive and that it has a shorter healing period. With the osteotome technique, even though we started with minimal residual bone height (4 mm), the final bone in the vertical dimension had a median height of 13 mm, compared with 15 mm when we used the Guillaume sinus up technique. This may be because of the small area of the sinus membrane affected by the crestally positioned osteotomes.
The 8 mm increase in bone height achieved in this study with the osteotome method is, however, considerably higher than the values reported by Fernando and Partata 9, who reported a bone increase of 5.3 mm, although it was found to be in agreement with the results of Summers 14. In the present clinical study, the osteotomy technique was used even in residual ridges with heights of 4–5 mm if primary stability had been achieved. This was in agreement with Li 15, who showed that the osteotomy technique can be used even in residual ridges with heights of 3–4 mm. However, it is in contrast to other studies 6,8,16 that have reported that the failure rate is higher when the bone crest height is less than 5 mm, a situation that did not occur in our study. This might be explained on the basis of the excellent initial stability of the implant during its placement.
However, it was found that the osteotome technique can be recommended when residual bone height is minimal and aimed at less bone height gain if minimal increase of bone is expected. It is a significant finding that the residual bone height has no bearing on the planned and inserted implant length, provided that excellent initial stability was achieved during implant placement. Although several investigators 5,6,8,9,17–20 have reported a high success rates (90–100%) when there is an appropriate initial bone height (7 mm) and described residual bone height a relevant factor for an appropriate response to the treatment, we used the osteotome technique in this study even in residual ridges with heights of 3–4 mm. This again may be because of the ensured and good initial stability of the implant placement.
However, the success rate of the implants placed after a lateral antrostomy (Guillaume sinus up technique) indicates that the use of β-TCP sinus up strips and granules leads to a stable bony configuration that allows implants of appropriate length to be inserted. When carrying out extensive augmentations in the severely resorbed maxilla, one cannot dispense with a lateral antrostomy approach for sinus elevation. Because of the least adequate host bone remaining for implant stabilization, the Guillaume lateral antrostomy sinus up technique was applied more often. Although this method is more technically demanding, it can be advantageous to place implants with the Schniederian membrane visible.
The results of this study show that the β-TCP strips and granules are a useful scaffold for bone regeneration when sinus elevation is required. It has the advantages of being stable and having an osseoconductive property that allows for direct contact with newly formed bone. The resorptive process appears to proceed slowly enough to provide sufficient time for bone maturation. It provides protection for the sinus membrane that may have been partially damaged by the lifting procedures. The new sinus floor or partition made up of a β-TCP strip also effectively prevents the migration of filler particles into the upper sinus. The material has many advantages: precision fit of the synthetic graft to the exact shape of the new sinus, biointegration of the material, firm fixture of a new floor, protection if the membrane is punctured, tight barrier against subjacent filler biomaterial migration, densification of bone fill, no inflammatory membrane reactions, elimination of postoperative graft morbidity, and shorter surgical procedure.
One might question the risk of infection that may arise from connective tissue left into the sinus or from either implants used. In the present study, no signs or symptoms of infection were observed during the entire postoperative period. This is may be attributed to the strict aseptic conditions intraoperatively and to the good selection of cases preoperatively. However, it is well known that not only autogenous materials such as bone or connective tissue but also allografts and alloplasts may be prone to infection. It seems that the occurrence of infection and/or sinusitis would be more related to predisposing factors of the patient and aseptic conditions before or during surgery than to the kind of graft used 21.
The osteotome technique was found to be suitable for elevating the antral membrane when an average increase of 3–4 mm bone was needed and with at least 4 mm remaining. Its high successful rate shows an image of long-term bone formation.
Where ridge resorption is more advanced, and at least 4 mm remaining, a lateral antrostomy is required in order to achieve sufficient bone height for adequate implant length.
The different sinus elevation techniques did not seem to affect the implant success rate. Using β-TCP in the strip form opens up new possibilities for sinus lift procedures as it simplifies this surgical technique and eliminates morbidity because of autogenic grafts.
Although clinical and radiographic analysis showed a 100% success rate and successful use of techniques, re-evaluation will have to be carried out after a longer period of functional loading. Furthermore, an additional study with histological evaluation of the area should be carried out in an animal model to clarify the postoperative aspect inside the sinus.
For exact calculation of the residual bone height, correct implant position, and the choice of an adequate method for sinus floor elevation, the establishment of an ideal setup and a CT scan with the radiologic template are recommended.
Conflicts of interest
There are no conflicts of interest.
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