Standard Implant placement in the posterior maxilla is often limited by the lack of vertical bone height due to the pneumatization of the sinus cavity. Several techniques have been developed to enter this cavity and elevate the membrane to enable implant placement. These methods may involve the use of bone grafts and membranes, as well as concurrent implant placement. This article reviews the clinical situations in which to apply these sinus lift techniques, complications and success rates.
ANATOMY OF THE MAXILLARY SINUS
The maxillary sinus is the largest paranasal sinus. It is pyramidal, with the base lying vertically on the medical surface of the lateral nasal wall. The sinus floor is 5mm to 12.5mm below the floor of the nasal wall of the nose. The maxillary sinus is surrounded by six bony walls," and its enlargement is termed sinus pneumatiziation. The sinus floor expands with age and is often in close relationship with the apices of the maxillary molars and premolars. With tooth lose, the antrum of further expands and the sinus may join the crest of the residual alveolar" ridge.
The septa may divide the sinus. A variable number of septa, referred to as Underwood's septa, has been reported with a prevalence of 32% in the atrophic/endetulous maxillary segment and 23% in the non-atrophic dentate maxillary segment and 23% in the atrophic/dentate maxillary segment with a mean 7.9 mm. Commonly, the septum is between the second pre-molar and the first molar.
The osteotome technique can help clinicians avoid employing an extensive surgical procedure (autraumatics vs LW or drilling).
This approach can be performed simultaneously with implant placement. The disadvantages are the uncertainty of people with implant placement. The disadvantages are the uncertainty of possible perforation of the sinus membrane, ridge fracture (extremely narrow ridge), and patient discomfort (tapping.)
This approach is indicated for a flat, sinus floor, when residual bone height is at least 5mm, and when crystal bone width is adequate for implant installation. The osteotome technique is contraindicated in patients with a history of inner-ear complications and vertigo for an oblique sinus floor (45? inclination). There is no drilling, and approximately 3 mm to 5 mm of additional bone height can be achieved. The osteotome is pushed apically, laterally displacing the buccal and palatal bones, while the concave tip with a sharp-ended of the osteotome pushes bone apically. The instrument is tampered to allow successive osteotome placement."
Summer describes the ridge expansion osteotomy technique.
Each subsequent osteotome fits into the site prepared by the previous osteotomy technique. Each subsequent osteotome fits into the site prepared by the previous osteotome until lateral ridge expansion is achieved.
A minimum ridge width of 3mm is required for the osteotome technique. The technique allows more implants to be placed in a narrower ridge in anterior and posterior sites. The approach is less invasive and has fewer risks compared to split crest and bone spreading. Summers describes the less inverse methods of elevating sinus floor in which bone is added to the original osteotome sinus floor (OSFE). The osteotomy is prepared to within 1 mm to 2 mm of the sinus floor, then widened with the Nos. 2 and 3 oscotomes. Bone is placed into the osteotomy, and the oestotome is advanced with light malleting (no more than 2 mm). More bone is added and the procedure is repeated at least 3 times. When the sinus floor is displaced and the graft is freely moving, the implant is tapped into place and acts as the final osteotomy. The future site development technique is used when less than 6 mm of bone is between the crest and floor and for augmentation in wider sites. The osteotomes never enter the sinus. A trephine may be used to create a cut in the bone, short of the sinus floor. The tapping of the "bone plug," inward follows. After the bone plug is slightly moveable, the site is "backfilled" with bone graft material and lightly malleted.
BONE GRAFT - IS IT NECESSARY?
In an animal study by Boyne, implants protruding into the maxillary sinus following elevation of the sinus membrane without grafting material exhibited spontaneous bone formation over more than half of the implant's height. The implant design and extent of protrusion influenced the amount of bone formation. Implants with open apieces or deep threads had small amounts of new bone growth. Those with rounded apieces had small amounts of new bone growth. Those with rounded apiece showed spontaneous bone formation extending around the implants if they only penetrated 2mm to 3mm into the maxillary sinus. However, when the same implants penetrated 5 mm into the maxillary sinus, only a partial (50%) growth of new bone was seen toward the implant apex. This is still pertinent today with today with different implant surfaces and designs, available that will continue to evolve.
SINUS FLOOR ELEVATION WITH LATERAL APPROACH
The lateral approach is also used for sinus floor elevation. It is indicated when there is reduced residual bone height, which does not allow standard placement or placement of implants in combination with minor sinus floor elevation using the osteotome technique. Contradictions are: Excessive, interarch distance due to unfavorable crown-to-root ratio, acute or chronic unresolved sinusitis, current sinus pathology (e.g. cysts or tumors),lodged root tips in the sinus, history of heavy smoking, a systemic compromise and psychological problems.
The use of many drug combinations have been reported. Among these are Amoxicillin 1 g or in the case of allergies: Clyindamycin 300 mg, both used 1 hour before surgery. If there is a history of chronic or periodic sinus infections, the use of Augmentin® (GlaxoSmithKline, www.gsk.com), 3 days before surgery and up to 7 to days after surgery is recommended, Glucocorticoids (dexamethasone 8 mg) can be prescribed 1 hour beforehand.
One Stage Or Two Stage?
The decision to use the one-or the two-stage technique is mainly based on the amount of residual bone available and the possibility of achieving primary stability for the inserted implants: one-stage sinus floor elevation with simultaneous implant placement and two-stage sinus elevation (delayed installation of the implant.) The grafted site matures in approximately 6 to 10 months. "The decision to use the one - or the two stage technique is mainly based on the amount of residual bone available and the possibility of achieving primary stability for the inserted implants."
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