Hereditary Dentin Defects

Meghan Sullivan Walsh February 15, 2011

Literature Review - St. Joseph/LMC Pediatric Dentistry

Hereditary Dentin Defects

Resident: Meghan Sullivan Walsh

Program: Lutheran Medical Center- Providence

Article Title: Hereditary Dentin Defects

Authors: J.-W. Kim and J.P. Simmer

Journal: Journal of Dental Research

Volume (number), Year, Page #’s; 86 (5), 2007; 392-399

Major Topic: The development of the dentin extracellular matrix, phenotypes and clinical classification of dentin hereditary defects as well as recent genetic data.

Overview of Method of Research: Author’s perspective and review of hereditary defects of tooth dentin that are classified under the designations of dentinogenesis imperfecta and dentin dysplasia.

Findings:

Evolution and Development: The main evolutionary perspective of the dentin extracellular matrix is that the biomineralization of bone and dentin is built on an organic matrix. This matrix is important for proper assembly and function, but not necessarily involved with deposition of this mineral.

Classification of Inherited Dentin Defects: A classification system was conceived which will be discussed next to discriminate various patterns of dentin defects. However, now with advances in genetic findings a comprehensive etiology-based classification system will soon need to be proposed.

Summary of Shields Classification:

DGI-I : dental phenotype associated with OI. Discoloration and attrition of dentition. Pulpal obliteration. OI with DGI is usually associated with collagen-I defects, however the clinical expression and genetic etiology are complex. DGI-I phenotype has also been found in other syndromes such as Ehlers-Danlos syndrome, Goldblatt syndrome and Schimke immuno-osseous dysplasia.

DGI -II : clinical and radiographic similarities associated with DGI-I. One of the most common dominantly inherited disorders (1:8000) Defects in the DSPP gene can cause DGI-II and DD-II. Many persons with DGI-II experience significant dental attrition and loss of vertical dimension. A secondary effect of this disorder may be hearing loss.

DGI-III : Brandywine tri-racial isolate Coloration and shape of teeth are variable however multiple pulp exposures are observed in deciduous teeth. Radiographic variability. Expresses similar phenotype and genotype to DGI-II.

DD-I : clinical crowns normal in shape, form and color. Radiographically teeth have short roots with a cresent-shaped pulpal remnant parallel to CEJ in permanent dentition and total pulpal obliteration in deciduous dentition. Several DD-I patients show an autosomal dominant mode of inheritance but it is not known if it is an allelic disorder of DSPP or a mixed phenotype.

DD-II deciduous teeth appear similar to DGI-II. Permanent teeth are of normal shape, form and color however pulp cavities show a thistle tube deformity and often show pulp stones. A mutation in the DSPP signal peptide codon was identified recently in a DD-II family. Recent studies are showing that DD-II and DGI-II phenotypes are mild and severe forms of the same disease.

Because many of these classifications can show similar clinical observations they also share common genetic etiology. The dental phenotypes are commonly observed in multiple diseases which is leading to much ambiguity when classifying these defects.

Key Points: Summary: There are 27 different types of collagen and 42 types of collagen genes. The elaborate chemistry involved in the synthesis of bone and dentin lead us to a diverse etiology and diverse clinical manifestations of inherited defects. Advances in the understanding of growth factors, tooth development and cell differentiation are being identified and investigated. Genetic etiologies of syndromic and inherited dentin defects are helping with our understanding of these defects and may possibly lead to new classification systems.

Assessment of the Article: My brain hurts and I cannot possibly think of anything more to say.