Dental Anatomy Introduction

Oral Cavity

• Consists of: lips, gingiva, cheek, tongue, floor of mouth, palate (soft and hard), and teeth
• Gingiva: soft tissue covering tooth root, consists of free gingiva and attached gingiva
• Interdental papilla: free gingiva present between teeth

Gingiva

• Alveolar mucosa
• Mucogingival junction
• Attached gingiva
• Free gingival groove
• Free gingiva
• Interdental papilla

Cheeks

• Constute the area of the face below the eyes and between the nose and the left or right ear
• Buccal means relating to the cheek
• Vestibule or buccal pouch or buccal cavity: area between the inside of the cheek and the teeth and gums

Tongue

• Consists of muscle fibers and glands
• Importance: has an important role in speaking, taste, mixing food, swallowing, and teeth cleaning

Macro-anatomy of Tongue

• Anterior two-thirds: papillary part
• Posterior one-third: lymphatic part
• Separated by sulcus terminalis

Floor of Mouth

• Area beneath the tongue containing blood vessels and salivary glands

Palate

• Roof of mouth divided into two parts: hard palate and soft palate
• Hard palate: anterior part, consists of incisive papilla, rugae area, and median palatine raphe
• Soft palate: posterior part, redder than hard palate
• Uvula: small soft structure hanging from the center of the posterior part of the soft palate

Teeth

• Arranged in two arches or two jaws (upper and lower)
• Upper arch: fixed in maxilla, upper teeth called maxillary teeth
• Lower arch: attached to the mandible (movable jaw), lower teeth called mandibular teeth
• Midline: imaginary vertical line dividing the dental arch into two equal halves
• Occlusal plane: imaginary horizontal line where upper teeth occlude with lower teeth
• Each dental arch can be divided into two halves, resulting in four quadrants

Teeth Function

• 1-mastication: incisors cutting food, canine wedge shape for tearing food, premolars and molars grinding food
• 2-appearance
• 3-speech
• 4-growth of jaw: if the child eats on one side, the growth of the jaw will be unilateral

Teeth Types

• Incisors
• Canines
• Premolars
• Molars

Incisors

• Two front teeth in each quadrant
• Central incisor: first tooth next to the midline
• Lateral incisor: second tooth

Canine

• Corner stone and the third tooth from the midline
• One canine in each quadrant

Premolars

• Two premolars in each quadrant
• Fourth and fifth teeth from the midline

Molars

• Three molars in each quadrant
• Sixth, seventh, and eighth teeth from the midline

Types of Dentition

• Primary dentition: 6 months to 6 years, called deciduous dentition, milky teeth, or predecessors
• Mixed dentition: 6 years to 12 years, period with both permanent and deciduous teeth
• Permanent dentition: from 12 years, called permanent or secondary or adult teeth or successors

Primary Dentition

• Begin at 6 months by eruption of lower first deciduous incisor
• Last deciduous tooth erupts at 24 months, upper second deciduous molar
• At 3 years old, all deciduous teeth reach the occlusal plane
• 20 teeth in total, 2 incisors, one canine, 2 molars in each quadrant

Mixed Dentition

• Begins at 6 years by eruption of lower first permanent molar
• Ends at 12 years by shedding of the last deciduous tooth, upper canine
• Shedding: physiological loss of deciduous teeth
• Called "ugly duckling stage" due to space of shedded teeth, teeth of different sizes, and gingivitis

Permanent Dentition

• Begins at 12 years, complete over the life
• 32 teeth in total, 2 incisors, 1 canine, 2 premolars, 3 molars in each quadrant
• Note: permanent molars have no predecessors, permanent premolars are the successors of deciduous molars

Dental Formula

• Used to differentiate between human teeth and teeth of other species
• Indicates the dentition of one side of the mouth only
• Human permanent teeth formula: I 2 C 1 P 2 M 3
• Human deciduous teeth formula: I 2 C 1 M 2

Permanent Maxillary Molars

Maxillary First Molar

• The crown of the maxillary first molar is wider buccolingually than mesiodistally and has four well-developed functioning cusps (mesiobuccal, distobuccal, mesiolingual, and distolingual) and one supplemental cusp (Cusp of Carabelli).
• The mesiobuccal cusp is broader than the distobuccal cusp, and its mesial slope meets its distal slope at an obtuse angle.
• The mesial outline of the crown is straight downward and mesially, until it reaches the crest of contour at the contact area.
• The distal outline of the crown is convex until it reaches the distal contact area.
• All three roots may be seen from the buccal aspect, with the lingual root being the longest, and the two buccal roots being approximately equal in length.
• The roots are not straight, although the buccal roots show an inclination to curvature halfway between the point of bifurcation and the apices.

Lingual Aspect

• The lingual cusps are the only ones to be seen from the lingual aspect.
• The mesiolingual cusp is much larger, with a mesiodistal width of about three-fifths of the mesiodistal crown diameter.

Mesial Aspect

• The only cusps seen from this aspect are the mesiobuccal, mesiolingual, and the fifth cusps.
• The buccal outline of the crown curves outward and buccally, making a short arc.

Distal Aspect

• The outline of the distal aspect is similar to that of the mesial aspect.
• The distal marginal ridge dips sharply in a cervical direction, exposing the distal portion of the occlusal surface of the crown.

Occlusal Aspect

• The occlusal aspect of the maxillary first molar is somewhat rhomboidal.
• The four major cusps are well developed, with the small minor, or fifth, cusp appearing on the lingual surface of the mesiolingual cusp near the mesiolingual line angle of the crown.

Pulp Cavity

• The mesiobuccal root is often very wide buccolingually and usually possesses an accessory canal (MB2).
• The pulp horns are usually prominent, and the palatal root usually has the largest canal.

Cervical Cross Section

• The cervical outline form of the maxillary first molar is rhomboidal with rounded corners.

Maxillary Second Molar

• The crown of the maxillary second molar is a little shorter cervico-occlusally and narrower mesiodistally than the maxillary first molar.
• The distobuccal cusp is smaller, allowing part of the distal marginal ridge and part of the distolingual cusp to be seen.
• The buccal roots are about the same length, and they are more nearly parallel and inclined distally more than those of the maxillary first molar.

Maxillary Third Molar

• The maxillary third molar often appears as a developmental anomaly.
• The crown is smaller, and the roots are shorter, with a tendency toward fusion with the resultant anchorage of one tapered root.
• The occlusal surface may present a heart-shaped outline, with a large lingual cusp and a small or absent distolingual cusp.

Questions

• The three grooves that radiate out from the central fossa in a maxillary first molar are the central, transverse groove of the oblique ridge, and buccal.

• The mesiolingual cusp on a maxillary first molar has two ridges: one that forms part of a transverse ridge and the other that forms part of an oblique ridge.

• The largest cusp on a maxillary second molar is the mesiolingual.

• The distolingual cusp is most likely to be absent on a maxillary second molar.

• The central circular fossa is the largest of the four fossae on a maxillary first molar.### Dental Anatomy References

• Several authors have contributed to the study of dental anatomy, including Ash, Black, Carabelli, Carbonell, Carlsen, Diamond, Hopewell-Smith, Kraus, Jordan, Abrams, Tomes, and Woelfel.

• The publications span from 1842 (Carabelli's "Anatomie des Mundes") to 1997 (Woelfel and Scheid's "Dental anatomy: its relevance to dentistry").

• The references cover various aspects of dental anatomy, including tooth form, descriptive anatomy, morphology, and occlusion.

• Some authors have specifically studied the tubercle of Carabelli, an anomaly of the maxillary molar teeth.

Notable Works

• Wheeler's Atlas of Tooth Form (ed 5, 1984) by Ash MM
• Descriptive Anatomy of the Human Teeth (ed 4, 1897) by Black GV
• Anatomie des Mundes (1842) by Carabelli G
• Dental Anatomy (1929) by Diamond M
• A Manual of Dental Anatomy (1894) by Tomes CS