Purpose of the sinus lifting
The reason for a sinus lifting operation lies in the insufficient vertical dimension of the upper jaw in the posterior area. This anatomic region is particularly critical for an implant insertion due to the rather improper bone structure, as the bone consists mainly of spongiosa.

After loss of teeth the bone gets resorbed in coronary-apical direction. From the direction of the maxillary sinus, a reduction of the vertical bone offer results from the life-long continuing pneumatization. At the same time, however, the functional demands during the chewing cycle are very high in the posterior area.
Sinus lifting is a treatment option in the posterior upper jaw. By means of sinus lifting, a sufficient vertical height for the implant insertion can be achieved. For this purpose, filling material is inserted underneath the mucosa of the maxillary sinus into the area of the bony bottom of the latter.

Diagnostic methods
For diagnostics in the sinus area, the radiograph of the paranasal sinuses and the orthopantograph are used in most cases. The X-ray of the paranasal sinuses is suitable for showing radioopacities while the orthopantograph is suitable for analysing the bone offer and anatomic aberrations such as septa or cyst-like pathologies. Computed tomography (CT) delivers pictures in all dimensions, with the help of which bony structures as well as the thickness of the mucosa of the maxillary sinus can be determined. CT pictures are not mandatory before a sinus lifting intervention, but they are advisable in case further information is required because of the patient’s history or because of the radiological examination. Moreover, they give an inexperienced surgeon a better idea of the preoperative situation.

Surgical method
During a collateral access according to a modified Caldwell-Luc method, the access is carried out on the untoothed jaw ridge or palatinal of it. A vertical relief cut can be made in the anterior fossa canina. The periost is detached from the posterior upper jaw. An osteotomy in the size of the planned window is constructed with a bud bur. An oval osteotomy is preferred to rectangular or to trapezium shape in order to avoid sharp edges which could injure the mucosa of the maxillary sinus. During preparation, one has to pay attention to protecting the neurovascular bundle during the exit from the infraorbital foramen.
The mucosa of the maxillary sinus is carefully lifted along the edge of the opening. The open bone is rotated horizontally in the maxillary sinus and serves as a cover for the bone transplant. The filling material is inserted and the mucoperiost flap is repositioned. The insertion of the implant is carried out either simultaneously during the sinus augmentation or about 6 months after the implant healing. After the augmentation, the window can be closed with a membrane. As a cover, polyactid membranes and unresorbing ePTFE membranes are eligible.
The so-called internal sinus lifting according to Summers refers to situations with a height of the remaining ridge of 4-6 mm and with a sufficient width. A trepanation just until beneath the mucosa of the maxillary sinus is carried out and shifted cranially with the help of osteotomies in such a way that a sufficient vertical implant position is created. As an alternative to the own bone, particulate bone replacement material can be used. The method is not suitable for higher degrees of jaw ridge atrophy.
According to the Sinus Consensus Conference, the simultaneous as well as the late insertion of implants can be successfully carried out with autogeneous and non-autogeneous bone material . A critical factor for the decision of when the implant is to be inserted is the primary stability. This increases with a rising height of the residual alveolar ridge. Normally, a sufficient primary stability at a bone height of 5 mm or less is rather doubtful. Misch (Misch, 1999) suggests a minimum limit of 10 mm for a simultaneous insertion of an implant in order to avoid complications.

Augmentation material
Besides autogeneous bone material, allografts, xenografts and alloplastic materials were used for the sinus augmentation. The result to be expected depends on the regenerative characteristics of the augmentation material.
Autogeneous bone material is considered the gold standard because of the osteogenetic, osteoinductive and osteoconductive characteristics. It can be extracted intraorally or, for example, from the iliac crest. Allografts in the form of demineralised or mineralised freeze-dried bones lack the osteogenetic characteristics. Xenografts are osteoconductive and have the advantage of quick availability. Alloplastic materials have mainly osteoconductive characteristics. Their advantage is that a transmittal of infectious particles can be excluded.
During the Sinus Consensus Conference of 1996, 38 surgeons pooled their data of 2997 implants in retrospect. The evaluation showed all types of augmentation materials to be equally successful. The total success rate was 90.0 % after 3 years, which corresponds quite well to the results of longitudinal analyses.
The survival statistics showed that implants with a coarse surface had significantly less failures than those with a smooth surface.
Despite of the limited amount of data it is shown that the residual height of the alveolar ridge has an important influence on the success rate. Smoking seems to influence the implant healing as well, which results in a 7 % higher failure rate in comparison to non-smokers.

Complications
General contraindications for a sinus lifting intervention are acute sinusitis, cysts and tumours.
In case of inflammations in the area of the filling, the latter has to be removed and antibiotic therapy has to be carried out at the same time. The healing process has to be finished before the area can be newly filled up again. Secondary healing in the area of the incision was often observed when tension-free wound closure was not achieved at the mucosa of the maxillary sinus.
Perforations of the mucosa of the maxillary sinus are the most frequent complications. In this connection, the augmentation is exposed and a bacterial infection of the maxillary sinus and adjoining sinuses can result from this.
Another possible complication is sinusitis, i. e. pathological changes of the mucosa of the maxillary sinus. The frequency was indicated to be between 0 and 20 % by Jensen et al. Sinusitis can appear, clinically and radiologically, as a swelling of the mucosa of the maxillary sinus. The clinical symptoms include constrained nasal breathing, secretion and headaches.
Postoperative bleedings are also a complication. They appear in the form of nosebleed or bleedings from the pharynx. Heavy bleedings require a nose tamponade.

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