Developmental Defects of Teeth

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developmental defects of teeth
with recent genetic concepts

INTRODUCTION:
Disorders of development of teeth may be prenatal or postnatal in origin and may be inherited or acquired. Their recognition and evaluation requires a thorough knowledge and evaluation of the normal chronology of the human dentition and of the normal development and structure of the teeth.

Disorders of development of teeth of teeth may be due to abnormalities in the differentiation of the dental lamina and the tooth germs, causing anomalies in the number, size and form of teeth (abnormalities of morphodifferentiation) or to abnormalities in the formation of the dental hard tissues resulting in disturbances in tooth structure (abnormalities of histodifferentiation).

Abnormalities of histodifferentiation occur at a later stage in development than abnormalities of morphodifferentiation; in some disorders both stages are abnormal. Histophysiology of tooth development:

A number of physiologic growth processes participate in the progressive development of the teeth. These are –
1. Initiation
The dental lamina and associated tooth buds represent those parts of the oral epithelium that have the potential for tooth development. Different teeth are initiated at different times. Initiation induction requires ectomesenchymal epithelial interaction. A lack of initiation results in the absence of either a single or multiple teeth or complete lack of teeth. Abnormal initiation may result in the development of single or multiple supernumerary teeth. 2. Proliferation

Enhanced proliferative activity after initiation results successively in the bud, cap and bell stages of the odontogenic organ. Proliferative growth causes regular changes in the size and proportions of the growing tooth germ. A disturbance has entirely different effects according to the time of occurrence and the stage of development that it affects. Tooth anomalies may include disturbances in the size, proportion or number of teeth 3. Histodifferentiation

It succeeds the proliferative stage. The formative cells of the tooth germ developing during the proliferative stage undergo definite morphologic as well as functional assignment. Differentiation of odontoblasts and ameloblasts takes place resulting the formation and apposition of enamel and dentin. Disturbance is the stage results in defects in the structure of tooth like amelogensis imperfecta type 1 and 4. 4. Morphodifferentiation

The morphologic pattern or basic form and relative size of the future tooth are established by morphodifferentiation that is by differential growth. Dentinoenamel junction and dentinocemental junctions are established. Disturbances in morphodifferentiation may affect the form and size of the tooth without impairing the function of the ameloblasts or odontoblasts.

5. Appposition
It is the deposition of the matrix of the hard dental structures. Defects in apposition results in anomalies like amelogenesis imperfecta type 2, dentin dysplasia. 6. Mineralization and Maturation

After matrix formation full mineralization and dental hard tissue maturation. Anomalies like amelogensis imperfecta type 3, fluorosis and interglobular dentin.

CLASSIFICATION OF DEVELOPMENTAL DEFECTS OF TEETH
1. Anomalies of initiation and proliferation
- anomalies of number
hypodontia and anodontia
hyperdontia
- anomalies of size
Microdontia
Macrodontia
- anomalies of shape
Germination
Fusion
Concrescence
2. Anomalies of morphodifferentiation
- anomalies of size and shape
Dilacerations
Dens invaginatus
Dens evaginatus
Taurodontism
Talon cusp
3. Anomalies of...
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