Welcome to the two-part lecture on clinical anatomy. In this series, we will discuss about the important structures of the maxilla and the mandible, with respect to implant surgery. Michael, first of all, why learning anatomy is important? Anatomy is taught in the early stage of one’s career. Therefore, we tend to forget the details. Even if we remember some anatomy, no pathology is involved in our education and the clinical relevance is only appreciated after practicing for some time. Besides, the way by which the cadavers are dissected is from the outer layer towards inner layers, or the specimens are cut in ideal planes such as sagittal section. The approach in surgery is in contrast, not necessarily following the same manner. Learning surgical anatomy can help the surgeons appreciate the structures being cut and improve their confidence in doing surgery. Another point is that a good knowledge of anatomy can help us recognize anatomical variations before doing the surgery, for example, a bifid of the mandibular canal. Nowadays, with newer technologies such as CT-Scan and 3D printing, surgeons can practice the procedures in models before the actual surgery, and the relevant anatomy can be appreciated more. The maxilla is formed by two maxillae bone joining at the center, and they form part of the orbital floors, nasal cavities, hard palate and the alveolar process. The maxillary sinuses are contained in the body. The relevant openings in the maxilla where the blood vessels and nerves travel through include the infra-orbital foramen, posterior superior alveolar foramina, and incisive foramen. The greater and lesser palatine foramen of the palatine bones are located posteriorly. Following teeth loss in the upper jaw, the alveolar process of the maxilla resorbs mainly at labial and buccal aspects, and finally in a superior direction, which results in a smaller alveolar ridge. If bone quantity is inadequate, we need to consider various bone grafting techniques as adjunctive procedures. For the quality of bone, the maxilla usually consists of type III or type IV bones, which indicates a thinner outer cortex with larger cancellous space. When placing implants in soft bones, we need to modify the drilling protocol in order to achieve a better primary stability of the implant fixture. - Division of the trigeminal nerve contributes to the general sense of the maxilla. Three cutaneous branches help to supply the skin of the face. The maxillary division emerges from the cranium through the foramen rotundum. The main trunk travels forward and emerges between the eye and the maxillary sinus to end as the infraorbital nerve. Along its course, three alveolar branches emerge to supply the sinus and the upper teeth. The posterior superior alveolar nerves supplies the molars. The anterior superior alveolar nerve that supply the front teeth emerges from the main trunk a short distance before it exits the maxilla. There may be a third branch that supplies the premolars, which is called the middle superior alveolar nerve. At the pterygopalatine fossa, the maxillary division branches off to the pterygopalatine ganglion. Here it supplies the palate below through the greater and lesser and palatine nerves. It also has a medial branch that supplies the nasal cavity and its glands. The lateral wall of the nose receives the posterior lateral nasal branches while nasal septum receives the nasopalatine nerve that emerges as the incisive nerve that supplies the mucosa of the premaxilla. The blood supply of the maxilla is derived from the branches of the external carotid arteries. The most important one is the maxillary artery, which gives rise to many branches in the infra-temporal fossa and pterygopalatine fossa. The veins of the maxilla drains posteriorly to the pterygoid plexus in the infratemporal fossa. It then joins the retromandibular vein and finally drains to the external jugular vein. There are certain adjunctive surgical procedures at the maxilla that may cause damage of the maxillary artery. For example, during harvesting of a connective tissue graft from the palate, the greater palatine arteries could be ruptured by blade if the graft is taken too deeply. Another procedure that may be associated with bleeding is the external sinus lift operation. Extra-osseous and intra-osseous anastomosis between the posterior superior alveolar artery and the infra-orbital artery could be formed. In this situation, the blood vessels could be damaged during flap elevation or preparation of the bony window. Maxillary sinus is an air-filled space in the face that is covered with a respiratory mucosa. It is pyramidal in shape with a size of a pea at birth but grows continuously in life. The maxillary sinus has a base at the lateral wall of the nose and an apex pointing at the zygomatic bone. The roof is formed by the orbit, and posteriorly, it extends to the infratemporal fossa and pterygopalatine fossa. Anteriorly, it is formed by the facial surface of the maxilla. The covering membrane is called Schneiderian membrane. The cilia present on the surface of this membrane beat in a synchronized manner to drain the mucous layer towards the ostium of the sinus. In infection, debris and pus has to travel against the gravity to be successfully removed. Therefore, it is a site prone to infection. Underwood described the presence of a septum separating the sinus into two compartments. Two types of septa are present. One is a sagittal septum. The other is a transverse septum. Special attention should be paid to these structures to avoid complications during sinus surgery. That’s all we want to discuss for the maxilla. In the second part we will talk about the mandible. See you in the next video.
