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Dentin Dysplasia Type II

NORD is very grateful to James P. Simmer, DDS, PhD, Professor, Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, for assistance in the preparation of this report.

Synonyms of Dentin Dysplasia Type II

  • coronal dentin dysplasia
  • DD-II

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Dentin dysplasia type II, also known as coronal dentin dysplasia, is a rare genetic disorder that affects the teeth. It is characterized by abnormal development (dysplasia) of dentin. Dentin is the hard tissue found beneath the enamel that surrounds and protects the pulp and forms the major part of teeth. Affected children may exhibit brownish-blue discoloration of baby teeth (primary or deciduous teeth) and obliteration of the pulp chambers. Permanent teeth are usually unaffected or only mildly affected. Dentin dysplasia type II only affects the teeth. The disorder is caused by mutations of the DSPP gene.

Dentin dysplasia type II belongs to a group of disorders known as the hereditary dentin disorders. In 1973, a physician and his colleagues defined five disorders characterized by inherited dentin defects (Shields classification). Many physicians have noted that the Shields classification is out of date. As new research reveals genetic mutations and better defines these disorders, a new classification system will be warranted. Unfortunately, the current understanding of these disorders is insufficient to allow the creation of this updated classification.

Symptoms

Dentin dysplasia type II is a dental abnormality characterized by abnormal development (dysplasia) of dentin. Within the interior of a tooth is pulp - a specialized tissue that contains nerves, blood vessels, and lymphatic vessels. Pulp is surrounded by a hard dental tissue known as dentin, which forms the primary material of the tooth. The exposed region of the tooth above the gum (also known as the crown or "coronal region") is covered by enamel, which is harder than dentin, while the root is covered by a bone-like rigid connective tissue known as cementum. Dentin protects the pulp chamber and provides support for enamel and cementum.

In individuals with dentin dysplasia type II, the baby teeth may be discolored appearing to be yellow, brown, grey-amber, or a brownish-blue color. The teeth are sometimes described as having a translucent "opalescence". (Opalescence refers to a milky, opal-like display of colors in reflected light.) In most cases, the permanent (secondary) teeth have a normal color.

When the dentin layer beneath the enamel crown is too weak to support it, the enamel will tend to wear away (abrade) and fall out prematurely.

In addition to being normal in color, permanent teeth are also normal in shape and size. However, they also have characteristic abnormalities of the pulp chambers. More specifically, on dental x-rays, pulp chambers appear unusually "flame shaped" and often have abnormal extensions toward the roots (i.e., "thistle-tube" shaped pulp chambers). In addition, the pulp chambers often contain numerous pulp stones, which are abnormal deposits of calcium salts (calcifications). With age, the pulp chambers of the permanent teeth may become partially obliterated. Evidence suggests that root formation in the permanent teeth is usually normal.

In rare cases, some individuals with dentin dysplasia type II may develop mild tooth discoloration or abnormally rounded (bulbous) crowns. If these abnormalities are pronounced in the permanent teeth, then the diagnosis changes to dentinogenesis imperfecta type II (DGI-II).

Causes

Dentin dysplasia type II is caused by mutations of the dentin sialophosphoprotein (DSPP) gene. This mutation is inherited as an autosomal dominant trait.

Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.

Investigators have determined that the DSPP gene is located on the long arm (q) of chromosome 4 (4q21.3). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered. For example, "chromosome 4q21.3" refers to band 21.3 on the short arm of chromosome 4. The numbered bands specify the location of the thousands of genes that are present on each chromosome.

Researchers have determined two classes of mutations that cause dentin dysplasia type II (and curiously, DGI-II & III). The first class involves missense mutations (i.e. changing one amino acid for another) in some of the first 18 amino acids of the DSPP gene (including the skipping of exon 3). The second class of mutations cause the amino acid repeat found in the second half of this large protein to change from being very acidic in character to very hydrophobic. Both classes apparently cause dentin dysplasia type II (as well as DGI-II & III) by disrupting the cell's ability to make and/or mineralize the dentin matrix in as yet unknown ways. To date, the best evidence suggests that complete loss of a single copy of DSPP is unlikely to cause dentin dysplasia type II (or DGI) phenotypes although such a loss is predicted to cause some recessive forms of dentin diseases.

Affected Populations

Dentin dysplasia type II affects males and females in equal numbers. The exact incidence and prevalence of dentin dysplasia type II is unknown. It occurs more frequently than dentin dysplasia type I, which is estimated to affect 1 in 100,000 people in the general population.

Abnormalities of dentin dysplasia have been known by many other names in the medical literature including rootless teeth, anomalous dysplasia of dentin, opalescent dentin, pulpless teeth, and thistle-tube teeth.

Related Disorders

Symptoms of the following disorders can be similar to those of dentin dysplasia type II. Comparisons may be useful for a differential diagnosis.

Inherited dentin defects are a group of rare inherited disorders that primarily affect dentin. In addition to dentin dysplasia type II, these disorders included dentin dysplasia type I and dentinogenesis imperfecta (DGI) types I, II and III. These disorders share similar symptoms including tooth discoloration, abnormalities of the pulp chambers, abnormally rounded (bulbous) crowns, and wearing away and premature loss of teeth. These disorders affect both the baby teeth and permanent teeth. Dentin dysplasia type II and dentinogenesis imperfecta types II and III are due to mutations in the DSPP gene (allelic disorders). These disorders of dentin defects are inherited as autosomal dominant traits. (For more information on these disorders, choose the specific disorder name as your search term in the Rare Disease Database.)
Standard Therapies
Diagnosis
A diagnosis of coronal dentin dysplasia is made based upon identification of characteristic symptoms, a detailed patient history, and a thorough clinical evaluation. X-rays may reveal abnormal coronal pulp formation, obliteration of the pulp chambers, pulp stones or thistle-shaped deformity of the pulp chamber.

Treatment
The treatment of coronal dentin dysplasia is directed toward the specific symptoms that are apparent in each individual. Because permanent teeth are often unaffected, no specific or unusually dental therapy is necessary. Recommended treatment may include regular monitoring by dental specialists and ongoing preventive dental care.

Genetic counseling may be of benefit for affected individuals and their families.

Standard Therapies

Diagnosis
A diagnosis of coronal dentin dysplasia is made based upon identification of characteristic symptoms, a detailed patient history, and a thorough clinical evaluation. X-rays may reveal abnormal coronal pulp formation, obliteration of the pulp chambers, pulp stones or thistle-shaped deformity of the pulp chamber.

Treatment
The treatment of coronal dentin dysplasia is directed toward the specific symptoms that are apparent in each individual. Because permanent teeth are often unaffected, no specific or unusually dental therapy is necessary. Recommended treatment may include regular monitoring by dental specialists and ongoing preventive dental care.

Genetic counseling may be of benefit for affected individuals and their families

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: prpl@cc.nih.gov

For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com

For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/

Contact for additional information about dentin dysplasia type II:

James P. Simmer, DDS, PhD
Professor, Dept. of Biologic and Materials Sciences
University of Michigan Dental Research Lab
1210 Eisenhower Place
Ann Arbor, MI 48108
E-mail: jsimmer@umich.edu

Organizations related to Dentin Dysplasia Type II

References

TEXTBOOKS
Stevenson RE, Hall JG, Eds. Human Malformation and Related Anomalies. 2nd ed. Oxford University Press, New York, NY;2006:461-463.

Brenneise CV. Dentin Dysplasia. NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:176-177.

JOURNAL ARTICLES
Wang SK, Chan HC, Rajderkar S, Milkovich RN, Uston KA, Kim JW, Simmer JP, Hu JC. Enamel malformations associated with a defined dentin sialophosphoprotein mutation in two families. Eur J Oral Sci. 2011:119:158-167.
McKnight DA, Hart PS, Hart TC, et al. A comprehensive analysis of normal variation and disease-causing mutations in the human DSPP gene. Hum Mutat. 2008;29:1392-1404.

McKnight DA, Simmer JP, Hart PS, Hart TC, Fisher LW. Overlapping DSPP mutations cause dentin dysplasia and dentinogenesis imperfect. J Dent Res. 2008;87:1108-1111.

Lee SK, Hu JC, Lee KE, Simmer JP, Kim JW. A dentin sialophosphoprotein mutation that partially disrupts a splice acceptor site causes type II dentin dysplasia. J Endod. 2008;34:1470-1473.

Kim JW, Simmer JP. Hereditary dentin defects. J Dent Res. 2007;86:392-399.

Beattie ML, Kim JW, Gong SG, et al. Phenotypic variation in dentinogenesis imperfecta/dentin dysplasia linked to 4q21. J Dent Res. 2006;85:329-333.

MacDougall M. Dental structural diseases mapping to human chromosome 4q21. Connect Tissue Res. 2003;1:285-291.

Brenneise CV, Conway KR. Dentin dysplasia, type II: report of 2 new families and review of the literature. Oral Surg. 1999;87:752-755.

Dean JA, Hartsfield JKJ, Casada JC, Wright JT, Hart TC. Genetic linkage of dentin dysplasia type II to chromosome 4q13. J Craniofac Genet Dev Biol. 1997;17:172-177.

INTERNET
Barron MJ, McDonnell S, MacKie I, Dixon MJ. Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia. Orphanet J Rare Dis. 2008;3:31. Available at: http://www.ojrd.com/content/3/1/31 Accessed Jan 2, 2014.

McKusick VA., ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:125420; Last Update: 10/13/2008. Available at: http://www.ncbi.nlm.nih.gov/omim/125420 Accessed Jan 2, 2014.

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2014/01/28 00:00:00 GMT+0

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