 Astra Tech
BioManagement Complex
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 Surgical techniques
A wide range of different surgical techniques are applied when placing implants under different preconditions. The summaries below show that one- and two-stage surgery, immediate placement in extraction sockets, bone augmentation and sinus lift can be successfully and predictably performed using the Astra Tech Implant System'".
 Bone formation at the maxillary sinus floor following simultaneous elevation of the mucosal lining and implant installation without graft material
Purpose: Traditional sinus lifting techniques have previously been accompanied with various graft materials, however, recent studies indicate that the mere lifting of the sinus membrane in combination with implant placement result in new bone formation. This study aimed to evaluate the bone formation after sinus mucosal lining and simultaneous placement of implants without the use of any graft material.
Materials and methods: Consecutive patient inclusion was performed, and 11 women and 9 men (20 patients, mean age 59 years) fulfilled the criteria of having <,5 mm subantral bone, and were thus treated with the modified sinus lift method. The surgical treatment started in November 2001 and ended in June 2004, at the University hospital Uppsala, Sweden.
Preoperative sedation (when required) and antibiotics were administered prior to surgery which was performed under local anaesthesia. After a mucoperiosteal flap opening, a rectangular osteotomy was made 5-6 mm cranial to the intended implant site in the maxillary sinus wall. An angulation of the bone cut was made to simplify the repositioning of the bony window. The bony window was carefully dissected, removed and kept in a sterile saline compress. The sinus lift was accomplished in all directions from the entrance window prior to placement of longest possible implants (9-15 mm, totally 44 Astra Tech ST implants). In order to allow for adequate clot formation around the implants in the sinus, cooling with saline at placement was not performed. In some cases, the drilling procedure was modified by means of the final drilling step. The conical burr was levelled in to the bone 1-2 mm less than recommended, giving a better primary stability using the effect of the conical neck design and the MicroThread". The establishment of a sufficient blood clot was checked before repositioning the window and suturing of the soft tissue. The patients were given analgesics and antibiotics postoperatively. Additionally, the patients were instructed to use nasal spray saline for 14 days, not to blow their noses, and not to wear the dentures for 7-10 days.
Prosthetic rehabilitation, primarily single crowns, but also a few cases with full arch bridges, was performed by the referring dentist after a mean healing period of 6 months.
Periapical radiographs and orthopantomograms were used for the evaluation of the bone gain around the implants. Necessary adjustments for axial projections were made using the 5.5 mm high MicroThread area as reference.
Result: Perforations of the sinus mucosa at surgery occurred in 11 of the 27 sinus lifts performed. The three largest perforations were sutured while the remaining 8 were so small that further dissection and "tenting" by the implant together with the formation of a blood clot was considered satisfactory. Healing was uneventful in all patients and no infection was observed. Five patients received 1-stage surgery.
One patient lost 1 implant (of 2 inserted) just after abutment placement. No further failures were recorded during the entire follow-up period ranging between 14 and 45 months (mean 27.5 months).
Radiographic evaluation showed a mean gain in bone height of 6.5 mm (SD=2.49 n=44) and a stable marginal bone situation. Two 4.5 mm wide implants in two patients showed a "push out" effect observed already after 3 months. However, the implants remained stable elevated about 2 mm from the mar-ginal bone, throughout the 2 years of follow-up. The regression analysis revealed that longer implants and minimal residual bone resulted in the greatest gain of bone.
Discussion: The approach to restore patients with very thin residual alveolar heights with implants without the addition of graft material have many advantages. No additional graft material is needed, thereby reducing the costs and morbidity possibly associated with harvesting of bone grafts. The technique allows for direct installation of implants avoiding long healing times, which is often the case with grafting techniques. Instead, the new bone is formed simultaneously with the osseointegration process. The TiOblast surface may have properties enhancing the local thrombin and coagulation cascade within the clot (compared to machined titanium) resulting in enhanced revascularization and osseointegration.
In conclusion, the maxillary sinus mucosal lining elevation technique shows an implant survival rate of 97.7%, which is well within accepted survival criteria. Furthermore, the method has profound health-economic advantages including shortened treatment times. As a consequence, the performance of sinus lift with grafting technique has decreased significantly at the mentioned University hospital.
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