placement guided bone regeneration (GBR) techniques may be required to augment the bone volume anterior to the border of the canal to facilitate implant placement in that area. The incisive canal itself can be grafted in a procedure called incisive canal deflation to provide further bone volume for subsequent implant placement. This technique can be performed under local anaesthetic with reflection of a full‐thickness flap raised, permitting access for complete removal of canal contents via rotary curettage. The canal can then be grafted with particulate bone without long‐term ill‐effects to the patient [4, 5]. While a transient loss of sensation in the anterior maxillary palatal area is possible, the revascularisation and reinnervation of the region due to the anastomoses with the greater palatine artery and nerve typically return sensation within several months.
Figure 7.1 Three‐dimensional versus two‐dimensional view of incisive foramen. A CBCT scan can provide invaluable information about the true anatomical relationship between the incisive foramen and the proposed site for a dental implant. The 3D reconstruction from the CBCT scan depicted in (a) and (b) allows for a more accurate assessment of the edentulous site when compared to the 2D periapical radiograph (c). The sagittal slice (d) shows the enlarged foramen.
7.3 Nasal Cavity
The inferior border of the nasal cavity is relevant to oral implantology due to its proximity to the oral cavity and tooth root apices. It consists of the anterior nasal spine and the maxillary alveolar process located anterior to the incisive canal and the hard palate or palatine process of the maxilla and horizontal plate of the palatine bone posterior to the incisive canal, when viewed sagittally through the midline. The nasal cavity provides the superior limit to the volume of the maxillary alveolar process available in the anterior region for implant placement, with the buccal plate providing the anterior limit while the palatal plate or incisive canal provides the posterior limit.
The nasal cavity is very well vascularised, with the sphenopalatine artery, a branch of the internal maxillary artery, providing the largest contribution of arterial supply. It is a branch of the sphenopalatine artery that anastomoses with the greater palatine artery via the incisive canal. The nasopalatine nerve, a branch of the maxillary division of the trigeminal nerve (CN V2), provides sensory input for the nasal cavity and follows the path of the sphenopalatine artery through the incisive canal where it anastomoses with the greater palatine nerve.
7.3.1 Importance in Oral Implantology
Dental implant placement in the anterior maxilla may be limited by the position of the anterior portion of the nasal cavity, particularly when the vertical height of the residual alveolar process is reduced. In such instance, penetration of the inferior border of the nasal cavity may occur. Nasal floor augmentation (NFA) techniques utilising autogenous bone grafts, allografts, xenografts, and combination grafts have been described in the literature [6–9] as methods for managing the atrophic maxilla. Although more clinical research is needed to fully evaluate the predictability of NFA, it may provide a viable and less invasive option than a traditional Le Fort 1 osteotomy [10].
7.4 Infraorbital Foramen
The infraorbital foramen is located immediately below the inferior border of the orbit and contains the infraorbital artery and infraorbital nerve (Figure 7.2). The infraorbital artery originates as a branch of the maxillary artery and anastomoses with the facial artery following its emergence through the infraorbital foramen. The infraorbital nerve is a terminal branch of the maxillary nerve (CN V2). It resides beneath the quadratic labii superioris and provides sensory innervation to the lower portion of the eyelid, the upper lip, and the lateral portion of the nose.
Figure 7.2 Location of the infraorbital foramen. The location of the infraorbital foramen is circled in yellow and can be found far superior to the maxillary occlusal plane.
7.4.1 Importance in Oral Implantology
Due to its superior location relative to the position of the alveolar process, the infraorbital foramen is not typically encountered in the surgical placement of dental implants. The infraorbital nerve can, however, be damaged by flap reflection and the use of retractors when performing a lateral window technique sinus lift and/or in cases of extensive maxillary ridge atrophy. Pulpal and soft tissue anaesthesia of the maxillary premolars, canine, and incisors may be achieved via the infraorbital block, which delivers anaesthetic to the infraorbital foramen as referenced 1 cm below the inferior orbital margin.
7.5 Maxillary Sinus
The maxillary sinuses are among the four pairs of paranasal sinuses (frontal sinuses, sphenoid sinuses, ethmoid sinuses, and maxillary sinuses), and the only sinuses relevant to oral implantology. The maxillary sinus expands throughout childhood, with continued inferior expansion resulting in close approximation of the sinus floor to the root apices of the maxillary premolars and molars [11]. In the event of the loss of a maxillary posterior tooth, continued sinus pneumatisation inferiorly can result in inadequate bone volume for placement of a dental implant in the alveolar process or basal bone (Figure 7.3) [12].
Figure 7.3 Changes in the presentation of the maxillary sinus. (a) In the dentate subject depicted in these panoramic and cross‐sectional CBCT scan views, a significant volume of bone is maintained in the alveolar process buccally, lingually, superiorly, and even inter‐radicularly. (b) In the partially edentulous subject similarly depicted, a marked loss of the alveolar process and pneumatisation of the maxillary sinus can be observed. This has resulted in an almost uniform, eggshell‐thin layer of bone separating the maxillary sinus from the oral cavity.
The maxillary sinus in adults is a hollow pyramidal shaped space in the maxilla approximately 15 mL in volume [13], roughly 3.5 cm high × 2.4 cm wide × 3.5 cm antero‐posteriorly [14]. The sinus communicates with the nasal cavity via an opening high on the medial wall of the sinus called the ostium, which is an opening approximately 3 mm in diameter [15] in the middle meatus or space located just superior to the inferior concha.
The anterior wall of the maxillary sinus is formed by the canine fossa and is close to the infraorbital foramen. The lateral wall of the sinus is formed by the zygoma. The superior wall of the sinus is the orbital floor. The posterior wall of the sinus separates the space from the structures of the infratemporal fossa and the pterygomaxillary fossa. The inferior wall or floor of the sinus is created by the alveolar process and basal bone, as well as the hard palate.
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
