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Last updated:
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NORD gratefully acknowledges 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.
Summary
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 have 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 changes (variants) in the DSPP gene.
Introduction
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). Genetic research has discovered that variants in DSPP cause dentinogenesis imperfecta (DGI) types II and III as well as dentin dysplasia (DD) type II; however, the types of variants only fall into 2 groups: 1) variants affecting the N-terminus and protein targeting and 2) frameshift variants into the –1 reading frame in the C-terminal repeat sequence region. The recently revised Shields classification is based upon genetic testing. DSPP N-terminal variants are designated as DGI-III, while C-terminal frameshifts as DGI-II. If the dental features (phenotype) is mild, the dentist receiving the genetics report can change the designation to DD-II.
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 and appear 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 people, 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).
Dentin dysplasia type II is caused by variants in the dentin sialophosphoprotein (DSPP) gene. This variant is inherited in an autosomal dominant pattern.
Dominant genetic disorders occur when only a single copy of a disease-causing gene variant is necessary to cause a particular disease. The variant can be inherited from either parent or can be the result of a new variant in the affected individual. The risk of passing the variant from an affected parent to a child is 50% for each pregnancy. The risk is the same for males and females.
Researchers have determined two classes of DSPP variants that cause inherited dentin defects. The first class involves variants that alter the beginning part of the protein (N-terminus) in a way that reduces its ability to be secreted properly and is toxic to the cell that produces it. This first class of DSPP variants causes DGI-II & DGI-III, which are closely related to DD-II, only more severe. The second class of variants (-1 frameshifts) cause the second (C-terminal) half of the DSPP protein to change from being very acidic in character to very hydrophobic and is also toxic to the cell that produces it. This second class of DSPP variants can cause DD-II, as well as DGI-II & III. It is not understood why this second class of DSPP variants sometimes result in the more minor dentin phenotype (DD-II), and sometimes the more severe phenotypes of DGI-II and DGI-III. Deletion of single copy of the DSPP gene when the person has a normal copy of the DSPP gene does not cause a dental phenotype, but a person with a missing copy of DSPP is predicted to be a carrier of the recessive form of DGI-III.
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.
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 unusual 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.
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
Some current clinical trials also are posted on the following page on the NORD website: https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
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
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
Simmer JP, Zhang H, Moon SJH, et al. The modified shields classification and 12 families with defined DSPP mutations. Genes (Basel). 2022;13(5):858. Published 2022 May 12. doi:10.3390/genes13050858
Yang J, Kawasaki K, Lee M, et al. The dentin phosphoprotein repeat region and inherited defects of dentin. Mol Genet Genomic Med. 2016;4:28-38.
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.
Barron MJ, McDonnell ST, Mackie I, Dixon MJ. Hereditary dentine disorders: dentinogenesis imperfecta and dentine dysplasia. Orphanet J Rare Dis. 2008;3:31. Published 2008 Nov 20. doi:10.1186/1750-1172-3-31
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.
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
Dentin Dysplasia Type II. McKusick VA., ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:125420; Last Update: 12/15/2022. Available at: http://www.ncbi.nlm.nih.gov/omim/125420 Accessed Feb 13, 2024.
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