Dental Terminology.

Cusp: a point or peak on the occlusal surface of molar and premolar teeth and on the incisal edges of canines.

Contact: a point or area where one tooth is in contact (touching) another tooth

Cingulum: a bulge or elevation on the lingual surface of incisors or canines. It makes up the bulk of the cervical third of the lingual surface. Its convexity mesiodistally resembles a girdle  encircling the lingual surface at the cervical.

Fissure: A linear fault that sometimes occurs in a developmental groove by incomplete or imperfect joining of the lobes. A pit is usually found at the end of a developmental groove or a place where two fissures intersect.

Lobe: one of the primary centers of formation in the development of the crown of the tooth.

Mamelon: A lobe seen on anterior teeth; any one of three rounded protuberances seen on the unworn surfaces of freshly erupted anterior teeth.

Ridge: Any linear elevation on the surface of a tooth. It is named according to its location or form. Examples are buccal ridges, incisal ridges, marginal ridges, and so on.

Marginal ridges are those rounded borders of enamel which form the margins of the surfaces of premolars and molars, mesially and distally, and the mesial and distal margins of the incisors and canines lingually.

Triangular ridges are those ridges which descend from the tips of the cusps of molars and premolars toward the central part of the occlusal surface. Transverse ridges are created when a buccal and lingual triangular ridge join.

Oblique ridges are seen on maxillary molars and are a companion to the distal oblique groove.

Cervical ridges are the height of contour at the gingival, on certain deciduous and permanent teeth.

Fossa: An irregular, rounded depression or concavity found on the surface of a tooth. A lingual fossa is found on the lingual surface of incisors. A central fossa is found on the occlusal surface of a molar. They are formed by the converging of ridges terminating at a central point in the bottom of a depression where there is a junction of grooves

Pit: A small pinpoint depression located at the junction of developmental grooves or at the terminals of these groops. A central pit is found in the central fossa on the occlusal surfaces of molars where developmental grooves join. A pit is often the site of the onset of Dental  caries

Developmental groove: A sharply defined, narrow and linear depression formed during tooth development and usually separating lobes or major portions of a tooth.

A supplemental groove is also a shallow linear depression but it is usually less distinct and is more variable than a developmental groove and does not mark the junction of primary parts of a tooth.

Buccal and lingual grooves are developmental grooves found on the buccal and lingual surfaces of posterior teeth.

Tubercle: A small elevation produced by an extra formation of enamel. These occur on the marginal ridges of posterior teeth or on the cingulum of anterior teeth. These are deviations from the typical form.

Interproximal space: The triangular space between the adjacent teeth cervical to the contact point. The base of the triangle is the alveolar bone; the sides are the proximal surfaces of the adjacent teeth.

Sulcus:-An elongated valley or depression in the surface of a tooth formed by the inclines of adjacent cusp or ridges.

Embrasures: When two teeth in the same arch are in contact, their curvatures adjacent to the contact areas form spillway spaces called embrasures. There are three embrasures:

(1) Facial (buccal or labial)

(2) Occlusal or incisal

(3) Lingual

(NOTE: there are three embrasures; the fourth potential space is the interproximal space ).

Cap stage

The first signs of an arrangement of cells in the tooth bud occur in the cap stage. A small group of ectomesenchymal cells stops producing extracellular substances, which results in an aggregation of these cells called the dental papilla. At this point, the tooth bud grows around the ectomesenchymal aggregation, taking on the appearance of a cap, and becomes the enamel (or dental) organ. A condensation of ectomesenchymal cells called the dental follicle surrounds the enamel organ and limits the dental papilla. Eventually, the enamel organ will produce enamel, the dental papilla will produce dentin and pulp, and the dental follicle will produce all the supporting structures of a tooth

1. Errors in development. These are usually genetic.

a. Variability of the individual teeth. In general, the teeth most distal in any class are the most variable.

b. Partial or total anodontia. missing teeth in children,

c. Supernumerary teeth.

d. Microdontia

e. Macrodontia

F. Microdontia

2. Errors in skeletal alignment. Malpositioned jaws disrupt normal tooth relationships.

3. Soft tissue problems.

-Ocasionally, the proper eruption of a tooth is prevented by fibrous connective tissue over the crown of the tooth.

-In the mixed dentition, the deciduous second molars have a special importance for the integrity of the permanent dentition. Consider this: The first permanent molars at age six years erupt distal to the second deciduous molars.

-Permanent posterior teeth exhibit physiological mesial drift, the tendency to drift mesially when space is available. If the deciduous second molars are lost prematurely, the first permanent molars drift anteriorly and block out the second premolars.

An incisor diastema may be present. The plural for diastema is diastemata.

-Important: The deciduous anteriors--incisors and canines are narrower than their permanent successors mesiodistally.

-Important: The deciduous molars are wider that their permanent successors mesiodistally.

-This size difference has clinical significance. The difference is called the leeway space.

The leeway space in the lower arch is approximately 3.4 mm.

-The leeway space in the upper arch is approximately 1.8 mm. In normal development, the leeway space is taken up by the mesial migration of the first permanent molars.

Mandibular Second Deciduous Molar.

-This tooth resembles the lower first permanent molar that is d

istal to it in the dental arch.

-There are two roots and five cusps. The three buccal cusps are all about the same size. This is in contrast to the lower first molar where the 'distal' cusp is smaller that the mesiobuccal and distobuccal cusps.

-The distal of the three buccal cusps may be shifted of onto the distal marginal ridge.  

NOTE

-Upper molars have three roots, lowers have two roots.

-Upper and lower second deciduous molars resemble first permanent molars in the same quadrant.

-Upper first deciduous molars vaguely resemble upper premolars. -Lower first deciduous molars are odd and unique unto themselves.

-First deciduous molars (upper and lower) have a prominent bulge of enamel on the buccal at the mesial. These help in determining right and left.

MAXILLARY LATERAL INCISORS

it is shorter, narrower, and thinner.

Facial: The maxillary lateral incisor resembles the central incisor, but is narrower mesio-distally. The mesial outline resembles the adjacent central incisor; the distal outline--and particularly the distal incisal angle is more rounded than the mesial incisal angle (which resembles that of the adjacent central incisor. The distal incisal angle resembling the mesial of the adjacent canine.

Lingual: On the lingual surface, the marginal ridges are usually prominent and terminate into a prominent cingulum. There is often a deep pit where the marginal ridges converge gingivally. A developmental groove often extends across the distal of the cingulum onto the root continuing for part or all of its length.

Proximal: In proximal view, the maxillary lateral incisor resembles the central except that the root appears longer--about 1 1/2 times longer than the crown. A line through the long axis of the tooth bisects the crown.

Incisal: In incisal view, this tooth can resemble either the central or the canine to varying degrees. The tooth is narrower mesiodistally than the upper central incisor; however, it is nearly as thick labiolingually.

Contact Points: The mesial contact is at the junction of the incisal third and the middle third. The distal contact is is located at the center of the middle third of the distal surface.

Root Surface:-The root is conical (cone-shaped) but somewhat flattened mesiodistally.

FORMATION OF THE PERMANENT DENTITION

Twenty deciduous tooth buds are formed initially.
Proliferative activity of the dental lamina during the bell stage that leads to formation of permanent tooth buds (cap stage) lingual of each deciduous tooth germ.
Molars have no predecessors; they are formed by posterior proliferation of the dental lamina.

HARD TISSUE FORMATION

Hard tissue formation starts at the late stages of the bell stage.
Differentiatioin of cells into odontoblasts and ameloblasts.
The cells of the inner dental epithelium will become ameloblasts.
The cells of the dental papilla opposite to the inner dental epithelium will become odontoblasts.
Dentin is formed before enamel.
Dentin initiates the formation of enamel.

ROOT FORMATION

The root of the tooth is composed by dentin and cementum.
Dentinogenesis is initiated by the odontoblasts.
Odontoblasts are formed as epithelial cells continue to proliferate from the cervical loop as a double layer of cells known as Hertwig's root sheath.

TOOTH SHAPE

The shape of the crowns results from the interaction of inner dental epithelium and the dental papilla.
The cells of the inner dental epithelium have a programmed proliferation.
This internal program determines the tooth form.

The fate of the dental lamina

Rests of Serres
The rest of Serres are rests of the dental lamina identified in the gingival soft tissues.
They are round to ovoid aggregates of epithelial cells that have clear cytoplasm (glucogen rich).
They result from early breakup of the dental lamina during bell stage.

Rests of Malassez
The rests of Malassez result from breakup of the Hertwig's root sheath during root formation.
They can be identified in the periodontal ligament and are responsible for the development of radicular cysts.