Practical Procedures in Implant Dentistry. Группа авторов
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The pyramidal shape of the maxillary sinus may be further complicated or compartmentalised by the presence of bony septa, which can cause partial division of the sinus. These septa are very common and may be found in 25–33% of sinuses [16, 17]. Although numerous variations, shapes, sizes, and locations [18] may be encountered, septa tend to have a wider base inferiorly and converge to a sharp edge superiorly.
The maxillary sinus derives its sensory innervation from branches of the maxillary nerve (CN V2) via the anterior, middle, and posterior superior alveolar nerve branches as well as the infraorbital nerve. Blood supply to the sinus stems from branches of the maxillary artery, namely the infraorbital and posterior superior alveolar arteries with some contribution additionally from the sphenopalatine and posterior lateral nasal arteries. Venous drainage of the maxillary sinus occurs via the facial vein, the pterygoid plexus, and the sphenopalatine vein.
The lining of the maxillary sinus consists of a specialised pseudostratified ciliated columnar epithelium and is called the Schneiderian membrane, which in health is usually less than 1 mm thick [19]. This complex respiratory mucosa contains specialised beaker (goblet) cells that produce mucus. The mucus traps inhaled particles, keeps the surface of the membrane moist, and serves to humidify inhaled air. The ciliated columnar epithelium provide a means of transport for the produced mucus. As a functional unit, the muco‐ciliary escalator lifts the mucus secretions and small particles up to the ostium and out to the nose.
7.5.1 Importance in Oral Implantology
A frequently encountered challenge when treating the edentulous posterior maxilla with dental implants is insufficient bone volume in an area with poor bone quality [20]. The bone volume of the residual alveolar ridge available for implant placement in this region may be limited by the presence of the maxillary sinus with or without pneumatisation, the loss of alveolar bone height following tooth loss, or a combination of both [21]. Bone volume may be increased via augmentation procedures of the maxillary sinus utilising a variety of surgical techniques and grafting materials in a predictable fashion [22–24].
Current evidence suggests that both lateral sinus floor elevation (SFE) and crestal SFE techniques are both predictably successful and safe, resulting in good long‐term implant survival rates [25, 26]. Examples of lateral sinus floor elevation are depicted in Figure 7.4. The clinician may utilise parameters including residual bone height, residual bone width, length of edentulous span, and residual bone quality to help guide the selection of a lateral versus crestal SFE, as well as determining whether a simultaneous or delayed implant placement is indicated. Future research on the long‐term viability of short implants (4–6 mm) may show a decrease in the need for SFE altogether [27].
Figure 7.4 Implant placement following maxillary sinus augmentation in a staged approach. Sinus floor elevation (SFE) via a lateral window approach was performed on both the right and left posterior edentulous segments, as the bone quality and residual bone height as shown in the panoramic radiograph (a) were not favourable for a simultaneous implant placement in conjunction with the grafting procedure. Following sinus graft consolidation over a period of six months, implants were placed in the posterior segments uneventfully as shown in the panoramic radiograph (b).
7.6 Greater Palatine Artery and Nerve
Upon exiting the greater palatine foramen located medial and slightly distal to the maxillary third molar, the greater palatine artery and nerve run anterior along the hard palate to the incisive foramen as described earlier. The greater palatine neurovascular bundle is typically located at the junction of the vertical and horizontal palatal walls of the palatal vault (Figure 7.5).
Figure 7.5 Position of the greater palatine artery and nerve. The greater palatine neurovascular bundle is outlined in purple in the frontal section of the skull at the level of the premolars. Individuals with higher palatal vaults exhibit greater distances from the lingual gingival margin to the neurovascular bundle than lower palatal vaults.
7.6.1 Importance in Oral Implantology
When creating an incision in the region of the greater palatine artery a zone of safety should be maintained to avoid injury to the artery with potential resulting bleeding and soft tissue necrosis. This zone of safety will often depend on the anatomical variation of the individual patient. Although the greater palatine neurovascular bundle is typically located at the junction of the vertical and horizontal palatal walls, significant variations in palatal vault depth mean the neurovascular bundle could be as close as 7 mm from the lingual gingival margin at the first molar site in low palatal vault phenotypes to as much as 17 mm in high palatal vault phenotypes [28]. The harvest of connective tissue grafts and free gingival grafts is routinely performed in the maxillary posterior palatal tissues from the first molar site forward to the canine. In most dentate patients without significant periodontal disease it is possible to harvest connective tissue and free gingival grafts up to 8 mm in height without injury to the neurovascular bundle [29].
References
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