Main functions of the dentition
Teeth are key structural organs of the human digestive system. Their main, digestive function consists in actively facilitating the act of mastication: they are responsible for efficient biting, crushing, and thorough grinding of food.
In addition to digestion, teeth perform a number of crucial secondary tasks. They directly participate in the act of respiration and play a critical role in proper speech formation, as they contribute to the clear articulation of most sounds. Furthermore, teeth largely determine facial aesthetics by establishing harmonious facial proportions.
Topography of the anterior group of teeth
The roots of the maxillary incisors feature variable topography. They are often located in close proximity to the spongy layer of the bony palate (palatum osseum) and the floor of the nasal cavity (cavitas nasi), separated from the latter by only a very thin bony plate. However, in individuals with a narrow facial type (leptoprosopia) and a high alveolar process, the apices of the incisor roots are situated at a considerable distance from the nasal cavity—this distance can reach 10 mm.
- Lateral incisors: have small roots, so they generally do not approach the nasal cavity closely.
- Vestibular wall: from the side of the oral vestibule (vestibulum oris), the roots of all incisors (especially the lateral ones) are covered by an extremely thin layer of bone forming the dental alveoli.
As for the maxillary canines, their position depends on the skull shape. In patients with a wide face and a flat palate, the apices of the canine roots often reach the level of the nasal cavity floor, locating near the nasal notch (incisura nasalis). There is also a rare anatomical variant: with a combination of a wide nasal cavity and a low extension of the alveolar recess of the maxillary sinus (sinus maxillaris), the canine root may approach directly to the floor of this sinus.
Relationship of the posterior teeth to the maxillary sinus
The roots of the maxillary premolars and molars can have extremely close topographic and anatomical relationships with the maxillary sinus. There are 3 main forms of this interaction for molars:
- In a narrow face and small sinus: the roots of premolars and molars are located at a significant and safe distance from the sinus floor.
- In a large sinus: the roots of the first and second molars (in some cases, the second premolar and third molar) are separated from the sinus cavity exclusively by the mucous membrane and an extremely thin bone plate.
- In a deep alveolar recess of the sinus (rare): the apices of the roots of the second or third molars literally protrude into the sinus cavity. In this situation, they are separated from it solely by the covering mucous membrane.
Considering premolars separately, the root of the first premolar approaches the inferior wall of the maxillary sinus only in cases of its very pronounced development. The root of the second premolar, with a significant alveolar recess, is often separated from the cavity by a bone layer only 2–3 mm thick. There is a clinically significant rare case: if a large sinus has a deep palatine recess, the floor of the second premolar alveolus may project directly into it, and then the root apex is separated from the cavity only by the mucous membrane (tunica mucosa).
Topography of the mandibular teeth: a comparative aspect
Although the main emphasis when studying the upper jaw is placed on the maxillary sinus, it is also important to understand the topography of the opposite jaw. The relationship of the mandibular teeth roots to the mandibular canal also depends on the anatomical structure of the skull. In a short jaw, the root apices of the first mandibular premolar can approach the mandibular canal very closely (projecting below the mylohyoid line). In addition, the roots of the second and third mandibular molars often come into close contact with the wall of this canal.
Characteristics of the temporary (deciduous) dentition
Throughout life, a person undergoes only one physiological change of teeth. The first to appear are the teeth of the temporary, or deciduous, dentition (dentes temporales s. lactei).
Their formation begins very early: tooth germs are laid down as early as the 6th–8th week of embryonic life. The eruption process starts at the age of 5–6 months. All deciduous teeth finally appear in the oral cavity by 2–2.5 years. Normally, the deciduous dentition consists of only 20 teeth. By group affiliation, they are distributed as follows: 8 incisors, 4 canines, and 8 molars. The anatomical formula for one side of the jaw is written as 2.1.2 (i.e., 2 incisors, 1 canine, and 2 molars).
Briefly: answers to topical questions
What are the features of the anatomical structure and topography of the maxillary canines?
The maxillary canine (dens caninus superior) has a massive cone-shaped crown tapering toward the cutting edge and ending in a single pointed cusp, with the crown slightly deflected vestibularly.
- Vestibular surface — convex, with a longitudinal ridge dividing it into a medial (smaller) and a lateral (larger) facet
- Palatal surface — narrow, convex, with a ridge passing into a developed dental tubercle
- Root — single, cone-shaped, slightly compressed laterally; the signs of the angle, curvature, and root are well pronounced
- Topography — with a wide face and a flat palate, the root apex often reaches the floor of the nasal cavity at the nasal notch; with a wide nasal cavity and a low alveolar recess of the sinus, the apex may approach the floor of the maxillary sinus
Which branches of the maxillary nerve innervate the maxillary teeth?
The maxillary teeth are supplied by branches of the infraorbital nerve (a continuation of n. maxillaris) and the posterior superior alveolar nerves.
- Posterior superior alveolar nerves (nn. alveolares superiores posteriores) — arise from the maxillary nerve in the pterygopalatine fossa, innervating the molars
- Middle superior alveolar branch (ramus alveolaris superior medius) — branches off from the infraorbital nerve, innervating the premolars (frequently absent)
- Anterior superior alveolar branches (rami alveolares superiores anteriores) — 1–3 branches from the infraorbital nerve, innervating the incisors and canines
All branches participate in the formation of the superior dental plexus (plexus dentalis).
From which arteries is the blood supply to the maxillary teeth carried out?
The blood supply to the maxillary teeth is provided by branches of the maxillary artery (a. maxillaris), which reaches the pterygopalatine fossa and divides there into terminal branches.
- Infraorbital artery (a. infraorbitalis) — gives off the anterior superior alveolar arteries (aa. alveolares superiores anteriores) to the anterior upper teeth
- Descending palatine artery (a. palatina descendens) — passes into the greater palatine canal and gives off the greater and lesser palatine arteries; the greater palatine artery supplies the hard palate
How many roots does the maxillary first molar normally have?
The maxillary first molar normally has three roots.
- Buccal roots (radix buccalis) — two roots, laterally compressed, shorter and thinner than the palatal root
- Palatal root — massive, cone-shaped; in the first molar, the roots are longer and diverge more widely
The upper part of the roots may be slightly curved.
What anatomical structures pass through the incisive canal?
The nasopalatine neurovascular bundle passes through the incisive canal (canalis incisivus).
- Nasopalatine nerve (n. nasopalatinus) is a branch of n. maxillaris (the maxillary branch of the trigeminal nerve), runs along the nasal septum, and emerges through the incisive foramen
- Nasopalatine artery and vein (a., v. nasopalatini) — accompany the nerve in the canal
The sphenopalatine artery anastomoses with a. palatina major precisely through the incisive canal.
The deciduous dental formula for one half of the jaw (2.1.2) is easy to remember by group affiliation: 2 incisors, 1 canine, 2 molars.
Class and exam questions
Can the roots of maxillary teeth penetrate the maxillary sinus?
Yes, in rare cases of a deep alveolar recess, the root apices of the 2nd or 3rd molars may protrude into the sinus cavity, separated from it only by the mucous membrane (tunica mucosa).
When does the eruption of deciduous teeth begin and end?
The first deciduous teeth begin to erupt at the age of 5–6 months, and the entire temporary dentition (20 teeth) is fully formed by 2–2.5 years of age.
Which teeth can lie directly adjacent to the mandibular canal?
The roots of the 2nd and 3rd mandibular molars can lie directly against the wall of the mandibular canal, and in cases of a short jaw, the 1st mandibular premolar as well.
What else to study on this topic
- Anatomical structure of the spongy layer of the palatine bone (palatum osseum)
- Variations in the structure of the alveolar recess of the maxillary sinus
- The process of tooth bud formation in early embryogenesis
- Clinical significance of the thickness of the vestibular wall of dental alveoli
- The relationship between leptoprosopia (narrow face) and the topography of tooth roots
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Other topics in the section "Chapter 4. Structure of the Dentoalveolar System"
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