Computer Guided Low Window Sinus Lift Technique

The study group included 12 patients that were treated using the low window lateral sinus lift technique with simultaneous implant placement. This was facilitated using a CAD-CAM generated surgical guide. Subjective assessment on postoperative pain and swelling as well as objective assessment of implant stability, vertical bone height gained and complications such as Schneiderian membrane perforation rates and bleeding.

Presurgical assessment of each patient was performed. Preoperative impressions were taken and study models were mounted. Orthopantogram (OPG) and cone beam computer tomography (CBCT) of the targeted areas were also done in order to evaluate residual bone height between the alveolar bone crest and the sinus floor, residual ridge width, bone quality and planning the number, size and position the implants.

Designing the surgical guide was performed using In2Guide™ system powered by OnDemand3D™.

The low window design was also planned where the lower osteotomy line will be flushed with the floor of the sinus, the upper line is 6mm of height from the lower line, the mesial line is flushed with the anterior wall and the distal line will correspond to the position of the most distal implant. The final product was fabricated using OnDemand3D™ which was then transferred to the 3d printer machine.

Patients were instructed to rinse with 0.125% chlorhexidine antiseptic mouth-wash for 2 minutes prior to surgery. The surgical area was anesthetized with local anesthesia. Infraorbital and greater palatine nerve blocks and local infiltration were given in order to properly anesthetize the area. A crestal incision was made in the posterior edentulous area followed by a vertical incision made at 45 degrees distal to the most anterior tooth. A full thickness mucoperiosteal flap was elevated at the surgical site enabling the apical osteotomy line to be drawn at a distance of 6mm above the residual bone height from the ridge. The customized surgical guide was secured in its proper position. After drilling, the anchor pin was placed in the prepared place. Using the standardized piezoelectric tip (SL1) with sterile saline irrigation, the outline of the window in the lateral maxillary sinus wall was formed.

The bone window was thinned down using the specialized DASK drill #4 and #5 from the DASK Kit until the grey shadow of the sinus membrane becomes visible. The sinus membrane at the circumference of the bony window was detached using the dome-shaped Sinus Membrane Elevator (XSE1L). Sinus membrane elevators (XSE2L), (XSE3L) and (XSE4L) were used to carefully lift the sinus membrane from the floor and anterior wall of the sinus to create adequate space for graft material (Figure 2-b). The membrane was further elevated to the medial wall in order to provide additional blood supply from that bone. The implants were drilled in the positions indicated by the surgical guide. Half the amount of the xenograft was introduced into the cavity followed by insertion of the dental implants. The dental implants were placed at torque 30\~45N‧cm. Stability of the implants was measured using an implant stability meter.

Filling the cavity with the rest of the xenograft was completed after implant placement(s). The size of the collagen membrane was adjusted to match the size of the lateral bone window and then placed and stabilized by the cover screw. The flap was released by short horizontal cuts in the inner surface of the mucosa to provide a tension free flap. This was followed by closure of the flap with water tight sutures (horizontal mattress with a single interrupted it's centre) using 3/0 silk suture material.

After 6 months from the operation, a small incision was made directly over the implant and the cover screw was removed. Implant stability was measured again using the Osstell device. The abutment was placed at torque 25\~30 N.cm. An impression was taken and sent to the lab for fixed prosthetics construction. The fixed prosthesis was cemented using glass ionomer cement.

Eligibility Criteria:
Inclusion Criteria:

* Patients requiring implant placement in the posterior maxilla (Kennedy Classification: Class 1 and Class 2).
* Age between 20-60 years irrespective of the gender.
* Tooth extractions at the implant sites were performed at least 4 months before surgery.
* Residual bone height between the alveolar bone crest and the sinus floor ranges from 4 to 6 mm.
* Patients who are willing and fully capable to comply with the study protocol.

Exclusion Criteria:

* Maxillary sinus pathologies (sinusitis, long standing nasal obstruction).
* Any disease contraindicating surgery (e.g. uncontrolled diabetes).
* Heavy smokers.
* Acute oral infections.
* Untreated periodontal disease.
* Poor oral hygiene.
* A history of radiotherapy or chemotherapy of the head and neck region.
* Pregnancy.