The osseous structures that support the teeth are the maxilla and the mandible. The maxilla consists of two bones, right and left maxilla sutured together at the midline. Both maxilla are joined to the base of the skull The mandible, on the other
hand, has no osseous union with the skull and is movable. (Fig.11 and 12)
Each jaw, maxilla and mandible, is formed of alveolar process and basal bone. The alveolar process is that portion of the bone which surrounds the roots of the teeth and give
them their osseous support.
Fig. 11. Maxilla and alveolar process.
1. Palatine process, 3. Premaxilla, 4. Incisive
canal, 5. Incisive suture, 6. Palatine spine, 7. Palatine sulcus, 9. Alveolar process, 10. Dental alveoli, 11. Interdental septa, 12. Interradicular septs, 13. Alveolar juga, 15. Palatine bone - horizontal plate, 21. Pyramidal process - inserted into
the pterygoid notch, 22. Lesser palatine foramen, 31. Posterior nasal spine, 33. palatine crest
Fig. 12. Alveoli of the upper central, lateral and canine (left), upper premolars (middle) and upper molars (lower).
alveoli (Teeth Sockets)
These cavities are formed by the facial and lingual bony plates of the alveolar process and by connecting septa of bone placed between the two plates. The form and depth of each alveolus is regulated by the form and
length of the root it supports.
Central incisor: The periphery of the alveolus is regular and rounded and its interior is evenly cone
Lateral incisor: It is generally cone shaped but it is narrower mesiodistally than labiolingually. It is smaller in cross section but deeper than the alveolus of the central incisor. Sometimes it is curved distally at its upper
Canine: It is much larger and deeper than that of the incisors. The periphery is oval with the labial width greater than the lingual. The socket is flattened mesially and somewhat concave distally. The labial plate of bone is
very thin over the canine eminence. Generally the facial cortical plate of bone over the anterior teeth is thin.
First premolar: The alveolus is kidney shaped with the cavity partially divided by a spine of bone which fits in the mesial
developmental croove of the root. If the root is bifurcated as is often the case, the terminal portion of the cavity is separated into buccal and lingual alveoli. The socket is flattened distally and wider buccolingually than mesiodistally.
premolar: It is also kidney shaped but the curvatures are the reverse of the first premolar alveolus. The septal spine is located at the distal side instead of the mesial. The tooth usually has one broad root with blunt end but occasionally bifurcated at the
First molar: There are three distinct alveoli widely separated. The lingual (palatal) one is the largest and is round, regular and deep. It extends palatally having a lingual plate over it which is very thin. The mesiobuccal
and distobuccal alveoli has no special characteristics except that the buccal plates are thin. The mesiobuccal alveoli is broad buccolingually with the mesial and distal walls flattened. The distobuccal alveoli on the other hand, is rounded and more conical.
Second molar: The alveoli are closer together as the roots of this tooth are not as divergent as those of the first molar.
Third molar: It is similar to that of second molar except that it is somewhat smaller in
all dimensions. Usually the roots are fused. The inter-radicular septum changes accordingly, if the roots are fused a sptal spine will appear in the alveolus at the point of fusion of the roots.
Central incisor: The periphery of the alveolus often dips down labially and lingually making an interdental spine out of the interdental septum separating the alveoli of the mandibular central incisors. The
alveolus is flattened on its mesial surface and is somewhat concave distally to accommodate the developmental groove on the root.
Lateral incisor: Similar to that of central incisor with two variations; the socket is larger, deeper
and its periphery dose not dip down on the lingual but may dip more on the labial. (Fig 12)
Canine: It larger, oval and deeper to accommodate the root of the tooth. The mesial and distal walls are irregular to accommodate developmental
grooves on the root. The lingual plate is stronger and much heavier than over the alveoli of the incisors, but the labial plate is thin.
First and second premolars: Are similar in outline, which is smooth and rounded although greater
buccolingually than mesiodistally. The alveolus of the second premolar is larger than that of the first premolar. The buccal plate is relatively thin but the lingual is heavy.
First molar: The socket is divided by an interradicular
septum which is thick and regular. The alveolus of the mesial root is kidney shaped, much wider buccolingulally than mesiodistally and constricted in the center to accommodate the developmental grooves found mesially and distally on the mesial root. The alveolus
of the distal root is evenly oval with no constriction, confirming to the rounded shape of the distal root.
Second molar: May be divided into two alveoli as that of the first molar or it may appears as one compartment near the
periphery of the alveolus, but divides into two compartments in the deeper portion.
Third molar: Usually the socket of the third molar is irregular in outline. It is much narrower toward the distal than the mesial aspect. In addition
it may have interradicular septa or septal spine to accommodate the irregularity of the root. ■