Sinus Lift
Vertical alveolar bone loss in the maxillary sinus floor area (i.e. in the lateral aspect of the jaw), following distant tooth extractions with severe bone loss, is a formidable anatomical obstacle to oral reconstructive treatment with dental implants. This prompts the undertaking of multi-stage restorative treatment. Regardless of the causes and extent of alveolar atrophy,This technique aims to restore chewing function and improve the appearance of the patient.
The maxillary sinus, formerly known as Highmor's cavity, is an even pneumatic space located bilaterally in the maxillary body. The floor of the maxillary sinus (the lower wall) is formed by the palatal process and partly the alveolar process of the maxilla. The bone forming this wall is usually, under normal conditions, very thick for this area and ranges from a few to several millimetres. This is very favourable when reconstruction of lost teeth in this area is required. The lowest point of the maxillary sinus floor corresponds to the position of the first molar (upper sixth). The roots of the molars and premolars can penetrate into the sinus, being a thin bony sheet and mucosa lining the sinus (Schneider's membrane). The volume of the maxillary sinus averages about 24 cm3. When teeth are lost, the alveolar bone atrophies, which is further facilitated by the pneumatic growth of the maxillary sinus. This leads to a clinical situation in which it is not possible to carry out proper reconstruction of missing teeth with implants.
The solution to this situation is a sinus lift procedure, i.e. a planned reduction in the volume of the maxillary sinus, thereby increasing the bone base necessary for the placement of dental implants. This is the most effective treatment method, in the case of alveolar atrophy in the lateral aspect of the jaw. The missing bone is replaced with Bio-Oss or bone chips taken from another area of the patient's (bone grafts).
There are two techniques for lifting the sinus floor (sinus lift):
- Open method- involves surgical, intraoral entry into the maxillary sinus from a lateral access. A piezoelectric bone cutter is always used to open the maxillary sinus, ensuring great precision in the procedure performed, as well as an atraumatic procedure. This is extremely important during the phase of opening the bone window into the maxillary sinus and preparing the Schneider membrane (the delicate mucous membrane lining the sinus). An intact mucosa is one of the prerequisites for a successful post-operative prognosis regarding the restoration of the missing bone tissue necessary for the correct placement of dental implants. In the space obtained in the floor of the maxillary sinus, Bio-Oss bone substitute material or autogenous bone chips are placed between the displaced Schneider membrane and the bone frame. The bone window is closed with a barrier membrane, e.g. Bio-Guide or OsseoGuard, and then covered with the patient's mucosa (gingiva) and tightly sutured. However, a situation in which Schneider's membrane is damaged does not definitively rule out the possibility of continuing with the sinus lift procedure. Unfortunately, the prognosis in such a clinical case is worse and complications are more frequent. The main complication is displacement of the graft material into the maxillary sinus lumen, resulting in volume loss and therefore insufficient bone reconstruction prior to the planned dental implant surgery. However, when perforation occurs, an additional mucosal repair procedure is necessary. The perforation should be covered with a resorbable membrane, shielding the grafted material from the maxillary sinus lumen, or if the Schneider membrane is thick enough, suture the perforation with dissolvable thread. In limited clinical cases, when the vertical thickness of the alveolar bone plate is 4 mm or more, it is possible to place an implant or implants in the reconstructed area at the same time. The prerequisite, however, is that the primary stability of the implant is maintained (implant partially anchored in a stable bone plate and partially in a loose graft material, inserted with significant resistance of own bone, causing sufficient stability for proper healing). The open sinus lift procedure allows for the reconstruction of vertical atrophy of the alveolar process by 5-9 mm.
- Closed method- used in clinical cases requiring an increase in the height of the alveolar process, prior to the planned placement of a dental implant to a small extent, i.e. by approximately 2-3mm. This method does not require additional lateral access to the maxillary sinus. The procedure is carried out through the implant pit (drilled hole for the implant corresponding to the natural alveolus). The drilled hole at the initial stage does not have a length corresponding to the length of the implant planned in this area. The missing distance is obtained using osteotomes (blunt-tipped surgical instruments that are mechanically forced into the implant socket, thickening and stretching the bone, causing an elevation of the bone tissue forming the floor of the maxillary sinus). The disadvantages of this method are the limited scope of bone reconstruction, the need to perform the same procedure with each implant placed, the lack of visual control over the surgical field, which significantly increases the possibility of perforation of the maxillary sinus mucosa.
