The main stages of intramandibular dental development.

Date: 2015-10-07; view: 778.

Topicality.

Initial knowledge control. The main stages of development of the temporary and permanent teeth. Stages of laying, eruption and formation of the temporary and permanent teeth in children.

The teeth develop in close relation with general development and growth of a child. In the period of laying and formation they develop under the influence of various causative factors of external and internal media which are reflected in the growth speed, mineralization degree and terms of dental eruption. The knowledge of basic stages of development of the temporary and permanent teeth is necessary for the correct choice of methods treatment of caries and its complications, application of sealing and filling materials of various classes according to the teeth development.

AimsToknow the terms of laying, eruption and maturation of the permanent and temporary teeth.

Study material.In the temporary and permanent teeth we determine the stages of intramandibular and extramandibular development.

1 – period of laying of dental germs

2 – period of formation and differentiation of dental germs

3 – histogenesis of dental tissues

4 – period of primary mineraliztion of hard dental tissues.

The period of laying of the germs of temporary teeth starts on the 6^th- 7^th weeks of intrauterine development. At this period a dental plate is formed, on which we may observe the formation of 20 dental papillae, according to the number of temporary teeth. On the 10^th week of embryogenesis the dental germs are formed, and they consist of the enamel organ, dental papilla and dental sac. These structures give beginning to all dental elements:

the enamel organ- to the enamel

the dental papilla- to the dentine and pulp

the dental sac- to the cement and periodntium.

Laying of the permanent teeth begins from the 5^th month of intrauterine development: on the 5^th-6^th month- the 6^th tooth, on the 8^th month- incisors and canines.

A period of differentiation of the dental germs includes their growth and preparation for the dental tissue formation( dentine and enamel). An important moment on the stage of dental germs differentiation is bending of the internal epithelium, and this determines the shape of future dental crown. It is on this stage that the influence of unfavorable factors causes the development of crown defects.

The period of dental tissue formation– is histogenesis. From the dental tissues the first to be produced is the dentine. Laying of the initial dentine layers at the periphery of dental papilla leads to initiation of the enamel formation –amelogenesis. Histogenesis of hard tissues of the temporary teeth begins on the 4^th month of intramaxillary development. The next stage is intramaxillary mineralization. In temporary teeth it begins in the 4^th-5^th months of intrauterine development. As for the permanent teeth the intramaxillary mineralization begins in the 9months of intrauterine development ( the 6^th tooth) and it intensively proceeds after the child'sbirth ( the 1^st year of life). The impairment of histogenesis and intramaxillary mineralization lead to various clinical manifestations – enamel hypoplasia, fluorosis, congenital disordered development of the enamel and dentine.