Baby teeth: eruption and their loss

Milky teeth erupt after birth in a certain sequence.

Teeth come from a double primordium: from the epithelium and the underlying mesenchyme. Enamel develops from the epithelial lining, and dentin from the mesenchyme. The formation of teeth begins at the end of the second month of intrauterine development. After the formation of the dental plate, protuberances appear in it, from which the enamel crowns are formed. The crowns of the baby teeth first (in the 11th week), and later the permanent ones.

The same teeth of the milk on each half of the jaw erupt simultaneously. Lower teeth, as a rule, erupt earlier than the upper ones. The exception is only the lateral incisors - the upper teeth appear before the lower ones.

Milk Bite Formation Stages

Teeth	Calcification		Erection, months		Fallout, years
	Start, months of pregnancy	The end, the months of life	Upper jaw	Lower jaw	Upper jaw	Lower jaw
Incisors
Central	5	18-24	6-8	5-7	7-8	6-7
Lateral	5	18-24	8-11	7-10	8-9	7-8
Fangs	6th	30-36	16-20	16-20	11-12	11-12
Molars:
The first	5	24-30	10-16	10-16	10-11	10-12
The second	6th	36	20-30	20-30	10-12	11-13

Terms for eruption of milk teeth (months) (according to S. Horowitz and E. Hixon, 1966)

Jaw	Teeth	Very early	Early 10%	The usual 30%	The usual 50%	Later 90%
Lower	Cutter central	4	5	6th	7.8	Eleven
Upper	Cutter central	5	6th	8	9.6	12
Upper	Cutter lateral	6th	7th	10	11.5	15
Lower	Cutter lateral	6th	7th	Eleven	12.4	18
Upper	Molyar first	8	10	13	15.1	20
Lower	Molyar first	8	10	14	15.7	20
Lower	Fang	8	Eleven	16	18.2	24
Upper	Fang	8	Eleven	17th	18.3	24
Lower	Molar the second	8	13	24	26.0	31
Upper	Molar the second	8	13	24	26.2	31

[1]

Baby teeth and bite formation

There are at least two periods in the existence of an already established, that is, completed, milk bite. According to AI Betelman, the first period often coincides with age 2 1 / 2-3 1/2 years and is characterized by:

• close standing of teeth with no gaps between them;
• absence of teeth erasure;
• location of the distal surfaces of the upper and lower dentition in one frontal plane;
• orthognathic bite.

The first period can be considered young, or initial, in the biological existence of the milk bite.

The second period is, respectively, the last and comes at an age of 3 1/2 to 6 years. It is characterized by:

• the appearance of interdental spaces, or distances, called diastemes in the stomatology (between incisors) or thromes (between other teeth); their width on the upper jaw is naturally greater than on the lower one;
• clear signs of erasure;
• mismatch in the frontal plane of the teeth of the lower and upper rows;
• transition of an orthognathic occlusion in a straight line.

Differences in the characteristics of the two periods can also be used to judge the biological age of children of early and pre-early age. The second sub-period of the milk bite illustrates the intense preparation of the dentoalveolar complex to the eruption of permanent bite teeth, the width of which is much larger than the teeth of the milk bite. The appearance of three reflects the growth rate of the jaw.

When analyzing the state of milk bite in children, it should be borne in mind that the absence of physiological diastems and three by the age of 6 years signals a lack of growth of the jaws and the child's unreadyness for teething permanent bite. In such cases, the child is counseled by a pediatric orthodontist, in some cases there are indications for prompt treatment.

Under physiological conditions, the erasure of the infant teeth is one of the manifestations of an approaching bite change. It should be ensured by the intensification of the use of teeth during chewing. To do this, children should be fed food such as raw vegetables and fruits, black bread, etc.

The biological role of milk bite is exceptionally high. Thanks to this intermediate stage of dentition, there are ample opportunities for prolonged modeling of the dentoalveolar system, the articulation system and the facial skull as a whole. With the appearance of the milk tooth, the space is fixed and for the subsequent permanent tooth, the active use of milk teeth during chewing gives an incentive for the growth of the jaws, to maximize the duration of the second dentition, which should only occur at a certain stage of growth of the jaws and facial skull. Premature loss of the milk tooth or its removal contributes to the premature eruption of the permanent tooth, desynchronization of the growth of individual parts of the jaw, creates unfavorable conditions for teething of neighbors and, consequently, worsens the conditions for their long healthy functioning. The formation of sound articulation and speech largely depends on the milk bite. With the failure of the malocclusion, the reproduction of 10-18 audio components of speech is disrupted. Milk bite is of great importance for the development of the child's personality, the features of his face. The latter is largely determined by the role of bite and chewing force in the development of tonus and mass of muscles of the facial skull and its ligament apparatus.

The period of preservation of milk teeth and the appearance of permanent teeth is called the period of the replacement bite. When you change your milk teeth to permanent (removable bite) after the milk tooth is dropped and before the eruption of the permanent tooth, usually 3-4 months. The first permanent teeth erupt at the age of about 5 years. They are usually the first molars. Then the sequence of appearance of permanent teeth is about the same as when dairy. After the change of milk teeth to permanent at the age of about 11 years there are second molars. Third molars ("wisdom teeth") erupt at the age of 17-25 years, and sometimes later. In girls, teething occurs with some lead in relation to boys. For an approximate estimate of the number of permanent teeth, regardless of sex, you can use formula

X = 4n - 20, where X is the number of permanent teeth; n is the number of years completed by the child.

The formation of both a dairy and permanent bite in children is an important indicator of the level of biological maturation of the child. Therefore, in assessing the biological maturity of children, the term "dental age" is used. Of particular importance is the definition of dental age in assessing the degree of maturity of children of pre-primary and primary school age, when other criteria are more difficult to use.

The normal sequence in the eruption of permanent teeth in children (no R. Lo and R. Moyers, 1953)

Room	Lower jaw	Room	Upper jaw
1	The first molar	2	The first molar
3	Central Cutter	5	Central Cutter
4	Side cutter	6th	Side cutter
7th	Fang	8	First premolar
9	First premolar	10	The second premolar
Eleven	The second premolar	12	Fang
13	The second molar	14	The second molar

Assessment of the level of age development by "dental age". Number of permanent teeth

Age, years	Floor	Slow development	Average rate of development	Accelerated development
5.5	Boys	0	0-3	More than 3
	Girls	0	0-4	More than 4
6th	Boys	0	1-5	More than 5
	Girls	0	1-6	More than 6
6.5	Boys	0-2	3-8	More than 8
	Girls	0-2	3-9	More than 9
7th	Boys	Less than 5	5-10	More than 10
	Girls	Less than 6	6-11	More than 11
7.5	Boys	Less than 8	8-12	More than 12
	Girls	Less than 8	8-13	More than 13

Age patterns of teething. The development of the permanent bite formula in children (permanent bite)

Age, years	Girls	Boys
6th	61 16 61 16 621 126	6 6 61 16 621 126
7th	621 126 621 126	621 126 621 126
8	621 126 65421 12456	621 126 6421 1246
9	64321 12346 654321 123456	64321 12346 654321 123456
10	654321 123456 7654321 1234567	654321 123456 654321 123456
Eleven	7654321 1234567 7654321 1234567	7654321 1234567 7654321 1234567
12	7654321 1234567	7654321 1234567

[2],

Inspection of milk teeth

When examining the facial part of the skull, attention is paid to the peculiarities of the position of the upper and lower jaw, the peculiarities of the occlusion, the number of teeth and their condition. The main pathological signs are changes in bite and teeth:

• hypo- or oligodentium;
• premature eruption or delay in teething;
• protruding diastems;
• dysplasia of the enamel, early caries;
• upper and lower jaws - upper micrognatia, upper protonation; retrognatia, micrognathia or agnathia lower (microgenia), lower prognathia.

Deformation of the bones of the base of the skull leads to the westing of the bridge of the nose and gout, reduction of the transverse dimensions of the upper jaw with the formation of a high Gothic sky. The anterior part of the upper jaw protrudes forward, the lower jaw then retreats, which is called prognathism. This position of the jaws subsequently leads to the formation of an incorrect bite.

When examining the milk teeth it is necessary to determine their number on the upper and lower jaw, the ratio of dairy and permanent teeth, their shape, growth direction, integrity and color of the enamel.

When examining, you can focus on some of the distinctive features of the teeth of a dairy and permanent bite. Milk teeth are characterized by the following properties:

• smaller sizes;
• bluish-white color (for permanent - yellowish color);
• more vertical arrangement;
• sharply expressed sign of curvature;
• clear boundary between the crown and the root of the incisors;
• erasure of cutting and chewing surfaces;
• some shakiness.

Quite big difficulties arise when trying to distinguish the second milk molar from the first permanent molar, but the difference can be facilitated by the fact that the second milk molar is in fifth place and the first permanent molar is the sixth.

Approximately the number of compulsory infant teeth can be determined by the formula n - 4, where n is the age of the child in months. Inconsistency of the timing of teething, usually delay, is most often associated with eating habits, often with rickets.

Diseases of permanent and milk teeth

Premature dentition of the teeth or their presence already from birth is much less common and is not a diagnostic sign of the disease. To the anomalies of the development of milk teeth include supercompleteness (the appearance of extra teeth), congenital absence, wrong direction of growth (teeth can be pushed out of the dental arch, rotated around their axis, significantly moved apart). Barrel-shaped deformation of incisors of the upper jaw with a semilunar incision of the cutting edge (Hitchinson's incisors) are one of the signs of congenital syphilis.

Some diseases, accompanied by a violation of the mineral and protein metabolism, transferred by the child during the period of calcification of the teeth, can lead to hypoplasia of the enamel. Milk teeth in this case lose their natural shine and are covered with depressions of various sizes and shapes. Unusual color of the enamel (yellow, brown, pink, amber) can be due to hereditary diseases or complications of drug treatment.

To frequent diseases of infant teeth is caries, which has a significant impact on the health of the child. The importance of poor dental hygiene and nutritional deficiencies in the origin of early and advanced caries in children has been confirmed.

The main etiological factor of caries is the interaction between carbohydrates of food and bacteria of the oral mucosa, primarily those located on the surface of the enamel of the teeth Streptococcus mutans. Organic acids arising from the fermentation by microorganisms of food carbohydrates, settled on the surface of the teeth or in the interdental spaces, demineralize the tooth enamel, make the deep tooth structures available for the microbial-inflammatory process with the formation of cavities, destruction of the pulp, and perhaps also for penetration into the alveolar part bones with the formation of an abscess. Caries of the milk tooth is extremely negatively reflected in the formation of a permanent bite. Multiple caries of infant teeth represents a very significant risk for the formation and continued functioning of permanent teeth. In addition, the accumulation of active and virulent bacteria in the foci of caries can lead to lymphogenic infection of the heart membranes and its valvular apparatus. Even focal infection of a limited carious process is a source of bacterial sensitization leading to rheumatic process, systemic vasculitis, glomerulonephritis and other potentially serious diseases.

Distinguish some special forms of caries in children, arising from similar mechanisms, but reinforced, due to special circumstances. These include caries and often altered bite in children who have been given uncontrolled feeding with sweet mixtures, juices or tea. Often this is just a bottle (a horn with a pacifier), left to the child for hours of night or daytime sleep. Here, a constant leakage of the sweet mixture into any part of the oral cavity, a small activity of saliva secretion and swallowing in a dream is triggered. This leads to local lesions of the teeth, more often incisors of the upper jaw, for the same bacterial-acidotic mechanism. A peculiar and often severe clinical picture of caries can be observed in children with gastroesophageal reflux or simply habitual regurgitation. The ingestion of acidified gastric contents into the oral cavity can lead to an independent acid destruction of the enamel, which is later layered by the action of bacteria.

Prevention of early caries of infant teeth is the whole chapter of preventive pediatrics. It includes monitoring the nutrition of a pregnant woman in the period of the laying of teeth. There are recommendations for the additional introduction of fluoride into the baby's nutrition, starting at 6 months of age.

Diagram of the daily dose of fluoride (mg), depending on the fluoride content in drinking water and the age of children (recommendations of the American Academy of Pediatrics)

Age	Concentration of fluorine in water
	Less than 0.3	0.3-0.6	More than 0.6
6 months - 3 years	0.25	0	0
3-6 years old	0.5	0.25	0
6-16 years old	1.0	0.5	0

Widespread propaganda and use of fluoride pastes for the prevention of dental caries in children has its own negative consequences: the lack of a strict technique for cleaning teeth, and the pleasant taste of the paste create conditions for the frequent ingestion of small amounts of children. This amount is quite enough for the widespread spread of fluorosis in recent years - the toxic excess of fluorine, the main negative manifestation of which is tooth decay. Therefore, for infants, it is more rational to use toothpastes that do not contain fluoride.

Prevention of dental caries in children is not limited to the balance of fluoride and calcium. It includes adherence to the principles of a complete nutrition balance across a wide range of vitamins and salts, limiting simple carbohydrates with high cariogenicity (sucrose), the use of fruit juices with the addition of water, limiting carbonated drinks, enriching the diet with complex carbohydrates, and adequate mechanical stress on the jaw.

Common diseases of the gums and teeth are gingivitis and periodontitis. The first are due almost exclusively to the accumulation in the oral cavity of the raids, consisting of pieces of food and bacteria, with poor care of the oral cavity. Clinically, this is expressed by the reddening of the mucous membrane at the edges of the gums and the swelling of the interdental papillae. Alveolar bone structures are never involved in the process.

Periodontitis is recognized by the involvement of connective tissue structures (ligaments) and bones adjacent to the tooth in the infectious process. This process always leads to irreversible changes with the destruction of tissues. In this case, an essential role is attributed to anaerobic streptococci and actinomycetes. Since the destruction of the bone usually occurs below the edge of the gum, it is necessary to use a roentgenologic examination of the jaw in the suspected area of the lesion for diagnosis.

Premature loss of milk teeth can be due to different, but always serious reasons. These include poisoning with salts or mercury vapor, radiation therapy of neoplasms, severe forms of acatalysis, hypophosphatase, diabetes mellitus, leukemia, histiocytosis, immunodeficiency. Milk teeth may fall out at scurvy (hypovitaminosis C).

[3], [4], [5]