The bony palate (palatum osseum)forms the roof of the oral cavity and the floor of the nasal cavity (Fig 6-19). It is made up of the palatine processes of the maxillary body; the incisive bone, which forms a bony fusion with the maxilla in adults; and the horizontal plates of the palatine bones, the backward projection of the palatine processes (Fig 6-20).The bony palate is held together by the following sutures:
- Median palatine suture (sutura palatina mediana)
- Transverse palatine suture (sutura palatina trans-versa)
- Incisive suture (sutura incisiva)
The median palatine suture runs exactly in the midline of the skull from the anterior to the posterior nasal spine. In the region of the alveolar processes, the median palatine suture is referred to as the intermaxillary suture—the suture between the maxillae.The median palatine suture joins the palatine processes and the alveolar processes
of the maxilla or the incisive bone and the horizontal plates of the palatine bones to each other. In the dorsal area, the palatine suture may be swollen into a ridge-shaped prominence; if so, it is known as the torus palatinus.The mucosal covering over this torus is very thin and not very soft; a denture may rock back and forth over this torus if the other parts of the palate are more yielding.
The transverse palatine suture crosses the median palatine suture vertically at the level of the interdental spaces between the second and third molars, deviates dorsally before the alveolar process, and then runs around the tuberosity of the maxilla. This suture can continue to be traced as the division between the maxilla and the pterygoid processes of the sphenoid bone.
The incisive suture runs on both sides from the incisive foramen between the lateral incisors and canines through to the nasal cavity. This suture links together the incisive bone and the maxillae.
The openings in the bony palate allow nerves and blood vessels to pass through to supply the palatal mucosa. The incisive foramen is the exit point for the incisive canal. In the mucosal covering, this incisive foramen can be identified as the incisive papilla (papilla incisiva), which often has to be hollowed out on the base of a denture.Third molars are found here as well as one greater palatine foramen (foramen palatinum majus) and, behind that, two or three lesser palatine foramina (foramina palatina minora). The greater palatine foramen is the exit point from the pterygopalatine canal for vessels and the greater palatine nerve (nervus palatinus major, part of the maxillary branch of the trigeminal nerve), which supply the glandular area and the anterior part of the palate. The lesser palatine foramina are secondary openings of the pterygopalatine canal and contain vessels and nerves to supply the posterior part of the palate.
Developmental abnormalities in the formation of the bony palate mainly arise at the sutures between the different parts of the palate. One common abnormality is cleft lip, jaw, and palate (cheilognathouranoschisis; cheilognathopalatos-chisis), which occurs when the incisive suture and the median palatine suture have failed to fuse. As a result, the oral and nasal cavity are not separated so that, when a baby is breastfeeding, the milk is forced back out through the nose or the infant cannot suckle at all because he or she is unable to create negative pressure in the oral cavity by suction. This cleft deformity is often bilateral. A cleft palate is the common name for the condition in which the incisive sutures and the median palatine suture are not fused. A harelip is the term used when only the incisive suture has not fused to the nasal cavity. In both cases, the lip of the maxilla has not grown together so that a cleft up to the nose is visible.
These developmental abnormalities, which are dominant inherited disorders, can be corrected by surgical repair while the child is still an infant. Prosthetic treatment to close the opening to the nasal cavity can be provided with what are known as obturators.