Amelogenesis imperfecta

Classification according to ICD-10
K00. 5	Amelogenesis imperfecta
ICD-10 online (WHO version 2019)

The Amelogenesis imperfecta (from Old English : Amel "melting" and Ancient Greek : γένεσις (genesis) "development" and lat. : Imperfectus "unfinished"), even innate Zahnschmelzhypoplasie called, is a genetically determined disease, which is a disturbance of enamel formationcomes. Tooth enamel mainly consists of minerals, the structure and structure of which is regulated in the tooth by protein components. Amelogenesis imperfecta is based on a malfunction of the proteins in the tooth enamel. Mainly the four proteins ameloblastin, enamelin, tuftelin and amelogenin are involved. Those affected have a yellowish to gray-brown discoloration of the teeth. The teeth have an increased risk of caries formation and are particularly sensitive to temperature. Any tooth can be affected. Enamel hypoplasia is more common in people with Williams-Beuren syndrome .

genetics

Amelogenesis imperfecta

To date, mutations in four different genes have been found in the disease: AMELX , ENAM , MMP20 and KLK-4 . These genes are involved in the development of the teeth and are obviously responsible for the formation of the protective, calcium-rich outer tooth layer, the so-called enamel. The mutations observed so far change the structure of the proteins or disrupt their formation. The consequences are usually abnormally soft tooth enamel, which shows a yellowish-brown color, and a significantly increased vulnerability of the teeth.

Tooth enamel is a highly mineralized tissue in which more than 95% of the volume is in the form of hydroxyapatite crystals. It is believed that the structure is regulated by ameloblasts in interaction with many types of organic molecules, including enamelin (ENAM; 4q21, OMIM * 606585), amelogenin (AMELX; Xp22. 3-p22. 1, OMIM * 300391), ameloblastin (AMBN; 4q21, OMIM * 601259), tuftelin (TUFT1; 1q21, OMIM * 600087), amelotin (AMELOTIN 4q13) [14], dentin sialophosphoprotein (DSPP; 4q21. 3, OMIM * 125485) and numerous enzymes such as kallikrein 4 ( KLK4; 19q13.3 - q13.4, OMIM * 603767) and matrix metalloproteinase 20 (MMP20; 11q22.3 - q23, OMIM * 604629). Mutations in one of these genes lead to the protein phenotype of amelogenesis imperfecta.

There is a connection between amelotin (AMTN) and tooth enamel defects and their development. In the absence of AMTN, weak spots appear on the tooth edges that are more easily broken or splintered. In this case, the mineralization of the tooth enamel takes place more slowly. In the ripening stage, the crystallites' volume growth is restricted, which in turn leads to hypomineralization.

Types

Type	OMIM	gene	protein	Gene locus
AIH1 (Amelogenesis imperfecta, X-linked 1)	OMIM 301200		Amelogenin	X p22. 3-p22. 1
AIH2 (Amelogenesis imperfecta 2, hypocalcification type)	OMIM 104500	ENAM	Enamelin	4 q21
AIH3 (Amelogenesis imperfecta, hypoplastic type / hypomaturation, X-linked 2)	OMIM 301201			Xq22-q28
AI1G (amelogenesis imperfecta, hypoplastic type, 1G) nephrocalcinosis	OMIM 204690
Amelogenesis imperfecta, hypoplastic type with open bite, autosomal recessive	OMIM 204650	ENAM	Enamelin	4q21
CRDAI amelogenesis imperfecta and cone-rod dystrophy, Jalili syndrome	OMIM 217080			2 q11. 2
AIHHT Amelogenesis imperfecta, hypomaturation, hypoplastic type, with taurodontism	OMIM 104510	DLX3	.	17 q21. 3-q22
Amelogenesis imperfecta, hypoplastic type microdontics	OMIM 104530
Kohlschütter-Tönz syndrome	OMIM 226750			16 p13. 3
Brachyolmia and Amelogenesis imperfecta (Platyspondyly and Amelogenesis imperfecta)	OMIM 601216
Amelogenesis imperfecta, pigmented hypomaturation type IIA1; AI2A1	OMIM 204700	MMP20 , KLK-4		19 q13. 41, 11 q22. 3-q23
Amelogenesis imperfecta type IC; AI1C, local hypoplastic type, autosomal recessive	OMIM 204650			4 q13. 3
Amelogenesis imperfecta type III; AI3 hypocalcification type, autosomal dominant	OMIM 130900	FAM83H		8 q24. 3

Amelogenesis imperfecta can occur with different inheritance patterns, depending on which gene is affected. In most cases, the ENAM gene is affected and the disease is inherited as an autosomal dominant trait. This means that in such cases a defective copy of the gene is sufficient for the disorder to develop.

Amelogenesis imperfecta can also be inherited as an autosomal recessive trait. The ENAM or the MMP20 gene can be mutated here. In the autosomal recessive mode of inheritance, both gene copies must be mutated on the respective alleles.

In about 5% of the cases the disease is caused by a mutation of the AMELX gene and then an X-linked dominant inheritance is found. In this mode of inheritance, the affected gene is on the X chromosome, one of the two sex chromosomes. As a result, male sufferers are usually more seriously ill.

There are also sporadic forms of the disease. In this case there is a new mutation of one of the affected genes and the patients then have no sick relatives.

Classifications

The different forms of amelogenesis imperfecta have been categorized differently.

Classification according to Weinmann

Weinmann first divided Amelogenesis imperfecta into two categories in 1945. He made the following classification:

• Enamel hypoplasia
• Hypomineralization

Classification according to Darling

Darling refined the categories into six sub-categories in 1956 by dividing Weinmann's two categories into three sub-categories each.

Classification according to Witkop

Witkop initially reduced the categories to five categories in 1957. Similarly, W. Schultze 1970.

Classification according to Witkop and Rao

Most recently, Witkop and Rao presented a further refined classification in 1971, which has eleven forms.

• Six forms of hypoplastic amelogenesis imperfecta ( dominant recessive )
• A form of hypomineralized amelogenesis imperfecta (dominant autosomal )
• Four forms of hypomaturation

Differential diagnosis

• Turner tooth
• Dental fluorosis
• Molar incisor hypomineralization - endogenous structural disorder
• Enamel defects in celiac disease

Enamel hypoplasia can also occur in the context of syndromes such as microdeletion syndrome 17q11.2 .

treatment

To protect teeth that have been damaged in this way, crowns are occasionally incorporated. For children (for reasons of cost) (prefabricated) steel crowns are often used, for adults ceramic or ceramic veneered crowns. If teeth have already been lost, bridges or implants can be the method of choice. In addition, regular professional tooth cleaning with a longer fluoridation interval is recommended, as increased plaque accumulation occurs on the rough tooth surfaces .

Epidemiology

There are no precise figures for the incidence of amelogenesis imperfecta. It is estimated that 1 in 700 people will get the disease in Sweden and 1 in 14,000 in the US.

swell

1. ↑ GEMOLL : Greek-German school and manual dictionary
2. ↑ Der kleine Stowasser : Latin-German school dictionary
3. ^ PJ Crawford, M. Aldred, A. Bloch-Zupan: Amelogenesis imperfecta. In: Orphanet Journal of Rare Diseases. . Volume 2, 2007, p. 17, ISSN  1750-1172 . PMID 17408482 . PMC 1853073 (free full text). (Review).
4. ^ Y. Nakayama, J. Holcroft, B. Ganss: Enamel Hypomineralization and Structural Defects in Amelotin-Deficient Mice. In: Journal of dental research. [Electronic publication before printing] February 2015, ISSN  1544-0591 , doi: 10.1177 / 0022034514566214 , PMID 25715379 .
5. ↑ JP Weinmann, JF Svoboda, RW Woods: Hereditary disturbances of enamel formation and calcification. In: J Am Dent Assoc . 1945; 32, S, pp. 397-418.
6. ^ AI Darling: Some observations on amelogenesis imperfecta and calcification of the dental enamel. In: Proceedings of the Royal Society of Medicine. Volume 49, Number 10, October 1956, pp. 759-765, ISSN  0035-9157 . PMID 13379391 . PMC 1889196 (free full text).
7. ^ CJ Witkop: Hereditary defects of dentin. In: Dental clinics of North America. . Volume 19, Number 1, January 1975, pp. 25-45, ISSN  0011-8532 . PMID 162890 .
8. ^ W. Schultze: Developmental abnormalities of teeth and jaws. In: RJ Gorlin, HM Goldman: C. Thoma's oral pathology. Mosby, St Louis 1970, pp. 130-136.
9. ^ S. Rao, CJ Witkop: Inherited defects in tooth structure. In: Birth defects original article series. . Volume 7, Number 7, June 1971, pp. 153-184, ISSN  0547-6844 . PMID 4375507 . (Review).

Note: The term amelogenesis is an etymological bastard .

credentials

• GB Winter, AH Brook: Enamel hypoplasia and anomalies of the enamel. In: Dent Clin North Am. (1975), pp. 3-24, vol. 19, 1 PMID 162891
• JP Simmer, JC Hu: Dental enamel formation and its impact on clinical dentistry. In: J Dent Educ. (2001), pp. 896-905 vol. 65, 9 PMID 11569606
• MJ Aldred, R. Savarirayan, PJ Crawford: Amelogenesis imperfecta: a classification and catalog for the 21st century. In: Oral Dis . (2003), pp. 19-23 vol. 9, 1 PMID 12617253
• M. Nusier, O. Yassin, TC Hart, A. Samimi, JT Wright: Phenotypic diversity and revision of the nomenclature for autosomal recessive amelogenesis imperfecta. In: Oral Surg Oral Med Oral Pathol Oral Radiol Endod. (2004), pp. 220-230 vol. 97, 2 PMID 14970781
• G. Stephanopoulos, ME Garefalaki, K. Lyroudia: Genes and related proteins involved in amelogenesis imperfecta. In: J Dent Res . (2005), pp. 1117-1126 vol. 84, 2 PMID 16304440

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !