Maxilla maxilla, steam room, located in the center of the face and connects with all its bones, as well as with ethmoid, frontal and sphenoid bones. The upper jaw participates in the formation of the walls of the orbit, the nasal and oral cavities, the pterygium and the inferior fossa. It distinguishes the body and the four processes, of which the frontal is directed upwards, the alveolar – downwards, the palatal is medially reversed, and the zygomatic – laterally. Despite the considerable volume, the upper jaw is very light, since in its body there is a cavity – sinus, sinus maxillaris (volume 4-6 cm3). This is the largest sinus among those in the bones of the skull (Fig. 1-8,1-9, 1-10).
Fig. 1-8. Topography of the upper jaw:
1 – frontal process, processus frontalis; 2 – front face, facies anterior
Fig. 1-9. The structure of the right upper jaw, maxilla (view from the lateral side): 1 – frontal process, processus frontalis; 2 – infraorbital margin; 3 – infraorbital foramen, foramen infraorbitale; 4 – nasal notch, incisura nasalis; 5 – canine fossa, fossa canina; 6 – anterior nasal spine, spina nasalis anterior; 7 – alveolar elevations, juga alveolaria; 8 – incisors; 9 – fang; 10 – premolars; 11 – molars; 12 – alveolar process, processus alveolaria; 13 – malar process, processus zygomaticus; 14 – alveolar foramen, foramina alveolaria; 15 – maxillary tuber, tuber maxillare; 16 – infraorbital groove; 17 – orbital surface of the body of the maxilla, facies orbitalis; 18 – lacrimal groove, sulcus lacrimalis
Fig. 1-10. The structure of the right upper jaw, maxilla (view from the medial side): 1 – the frontal process of the maxillary bone; 2 – trellised comb, crista ethmoidalis; 3 – lacrimal groove, sulcus lacrimalis; 4 – maxillary sinus, sinus maxillaris; 5 – large palatine furrow; 6 – nasal crest; 7 – palatal sulcus; 8 – alveolar process; 9 – molars; 10 – palatine process, processus palatinus; 11 – premolars; 12 – fang; 13 – incisors; 14 – incisal canal; 15 – anterior nasal spine, spina nasalis anterior; 16 – nasal surface (facies nasalis) of the maxillary bone; 17 – shell crest, crista conchalis
Upper jaw body (corpus maxillae) has 4 surfaces: anterior, infratemporal, orbital, and nasal.
Front surface at the top it is bounded by the infraorbital rim, below which there is a hole of the same name, through which the vessels and nerves exit. This hole 2-6 mm in diameter is located at the level of the 5th or 6th teeth. Under this hole lies the canine fossa (fossa canim), which is the site of the beginning of the muscle, raising the angle of the mouth.
On a free surface there is a tuber of the upper jaw (tuber maxillae), on which there are 3-4 alveolar orifices heading towards the roots of large molars. Through them pass the vessels and nerves.
Orbital surface contains a teardrop, restricts the lower orbital fissure (fissura orbitalis inferior). At the rear edge of this surface is the infraorbital groove (sulcus infraorbitalis), which passes into the channel of the same name.
Nasal surface largely occupied by the maxillary cleft (hiatus maxillaris).
Alveolar process (processus alveolaris). It is like a continuation of the body of the upper jaw downwards and is an arcuately curved bone roller with a bulge facing anteriorly. The greatest degree of curvature of the process is observed at the level of the first molar. The alveolar process joins the maxillary suture with the same process of the opposite jaw, in the back, without visible borders, passes into the tuber, medially into the palatal process of the upper jaw. The outer surface of the appendix, facing the threshold of the mouth, is called the vestibular (facies vestibularis), and the inner, facing the sky, is called the palatine (facies palatinus). The arch of the appendix (arcus alveolaris) has eight dental alveoli (alveoli dentales) for the roots of the teeth. In the alveoli of the upper incisors and canines, the labial and lingual walls are distinguished, and in the alveoli of the premolars and molars, the lingual and cheek walls. On the vestibular surface of the alveolar process, each alveoli correspond to alveolar elevations (juga alveolaria), most pronounced in the alveoli of the medial incisor and canine. The alveoli are separated from each other by bony interalveolar septa (septa interalveolaria). The alveoli of the multi-rooted teeth contain inter-root septa (septa interradicularia), which separate the roots of the tooth from each other. The shape and size of the alveoli correspond to the shape and size of the tooth roots. In the first two alveoli are the roots of the incisors, they are cone-shaped, in the 3rd, 4th and 5th alveoli are the roots of the canine and premolars. They have an oval shape and are squeezed somewhat from front to back. Alveoli canine is the deepest (up to 19 mm). In the first premolar of the alveoli, it is often divided by inter-root partition into lingual and buccal root chambers. In the last three alveoli, small in size, are the roots of molars. These alveoli are divided by inter-root septa into three root chambers, of which two face the vestibular and the third to the palatal surface of the process. The vestibular alveoli are somewhat compressed from the sides, and therefore their size in the anteroposterior direction is smaller than in the palatine-buccal. The lingual alveoli are more rounded. Due to the variable number and shape of the roots of the 3rd molar, its alveoli are varied in shape: it can be single or divided into 2-3 or more root chambers. At the bottom of the alveoli is one or more openings that lead to the corresponding tubules and serve for the passage of blood vessels and nerves. Alveoli adjacent to the thinner outer plate of the alveolar process, which is better expressed in the molars. Behind the 3rd molar, the outer and inner compact plates converge and form an alveolar tubercle (tuberculum alveolare).
The area of the alveolar and palatal processes of the upper jaw, corresponding to the incisors, in the embryo is an independent incisal bone, which is connected to the upper jaw by means of a incisal suture. Part of the incisal suture on the border between the incisal bone and the alveolar process grows before birth. The seam between the incisal bone and the palatal process is present in the newborn, and sometimes it remains in the adult.
The shape of the upper jaw is individually different. There are two extreme forms of its external structure: narrow and high, typical of people with a narrow face, as well as wide and low, usually found in people with a wide face (Fig. 1-11).
Fig. 1-11. Extreme forms of the upper jaw structure, front view: A – narrow and high; B – wide and low
Maxillary sinus – the largest of the paranasal sinuses. The shape of the sinus basically corresponds to the shape of the upper jaw body. The volume of the sinus has age and individual differences. The sinus can continue in the alveolar, zygomatic, frontal and palatine processes. In the sinus distinguish the upper, medial, anterolateral, posterolateral and lower walls.
Materials used: Anatomy, Physiology and Biomechanics of the dental system: Ed.