for Dentinogenesis Imperfecta
|Evaluating the Patient: The
oral health care provider called upon to manage the patient
with DI should first ascertain which type they are dealing
with. Severe cases of dentin malformation associated osteogenesis
imperfecta or other syndromnes can present significant medical
management problems. Careful review of the patient's medical
history will provide clues as to the severity of bone fragility
based on the number of previous fractures and which bones
were involved. The dentist must be extremely cautious in those
individuals prone to fractures when performing any surgical
procedures or treatment that could involve forces that will
be transmitted to the jaws due to the increased risk of fracturing
the jaw. Physical restraint is contraindicated in those patients
with a predisposition to frequent bone fractures. The presence
of spontaneous cases of DI where there is no family history
is likely the first presenting feature of an autosomal recessive
or new autosomal dominant mutation of OI and requires further
medical and genetic evaluation. Children with unexplained
bone fracturing should be evaluated for DI as a possible indicator
of an undiagnosed case of OI. This can help explain bone fractures
and be important in helping delineate child abuse from mild
or undiagnosed OI .
|Providing optimal oral health treatment for
DI frequently includes preventing severe attrition associated
with enamel loss and rapid wear of the poorly mineralized
dentin, rehabilitating dentitions that have undergone severe
wear, optimizing esthetics,and preventing the common dental
problems associated with caries (which is reportedly low in
people with DI) and periodontal disease. The dental
approach for managing DI will vary depending on the severity
of the clinical expression.
Treatment of mild to moderate DI severity or in those patients
not exhibiting enamel fracturing and rapid wear of the dental
crown, routine restorative techniques can often be used effectively.
Becuase the permanent dentintion is frequently
less severely affected than the primary dentition these
treatments are more commonly applied to the permanent teeth.
For example, intra-coronal restorations (i.e., amalgams
and composites) will typically be adequately retained in
individuals not suffering from enamel fracturing and attrition
but are contraindicated in cases of enamel loss with attrition.
Bonding of veneers can be used to improve the esthetics
and mask the opalescent blue gray discoloration of the anterior
teeth. Bleaching has been reported to lighten the
color of DI teeth with some success, however, becasuse the
tooth discoloration is caused primarily by the yellow-brown
underlying dentin, bleaching alone is unlikley to produce
a normal tooth coloration in cases with significant discoloration.
In more severe cases where there is significant enamel
fracturing and rapid dental wear, the treatment of choice
is full coverage crowns. Intra-coronal restorations, such
as amalgams and composites, are not well retained in patients
having severe attrition. In these individuals the tooth
structure tends to wear and break away from the restoration
ultimately resulting in restorative failure. Stainless steel
crowns will be the treatment of choice for cases in the
primary dentition with excessive tooth wear. Stainless steel
crowns with open face composite restorations or composite
crowns can be used for a more esthetic result when crowning
anterior teeth. Management of permanent DI teeth with fracturing
and excessive wear can be treated with porcelain fused to
Ideally restorative stabilization of the dentition will
be completed before excessive wear and loss of vertical
dimension. Cases with significant loss of vertical dimension
will benefit from re-establishing a more normal vertical
dimension during the restorative treatment. Obtaining an
appropriate vertical dimension and providing soft tissue
support from restoration of the patient's dentition will
return the individual's facial profile to a more normal
appearance. Cases having severe loss of coronal tooth structure
and vertical dimension maybe considered candidates for overdenture
|Some cases of dentinogenesis imperfecta will
suffer from multiple periapicle abscesses apparently resulting
from pulpal strangulation that occurs secondarily to pulpal
obliteration or from pulp exposure due to extensive coronal
wear. The potential for developing periapicle abscesses is
another indication for performing thorough periodic radiographic
surveys on all individuals with DI. Since these cases have
pulpal obliteration and the dentist will rarely be able to
negotiate the canal, apical surgery may be required to maintain
the abscessed teeth. Attempting to negotiate and instrument
obliterated canals in DI teeth can easily result in lateral
perforation due to the poorly mineralized dentin.
Two types of dentin dysplasia are recognized.
Dentin dysplasia type I (OMIM#
125400) is a rare dentin defect that appears to be inherited
as an autosomal dominant condition with a reported frequency
of 1:100,000 persons. Clinically the dental crowns appear
normal while radiographically, the teeth are characterized
by pulpal obliteration and short blunted roots .
The teeth are generally mobile, frequently abscess and can
be lost prematurely. There is no known specific treatment
approach for DD type I although effort to keep occlussal
forces to a minimum and avoiding orthodontic treatment for
the malaligned teeth may increase the longevity of the dentition
. The genetic defect
for DD type I remains unknown.
The affected dentin has a unique cascading waterfall appearance
apparently due to a cyclical developmental process of premature
odontoblast death, new odontoblast recruitment, dentin deposition
and odontoblast death. The molecular defect in DD type I
Dentin Dysplasia Type 1
|Dentin dysplasia type II (OMIM#
125420) is also inherited as an autosomal dominant trait.
Dentin dysplasia type II appears virtually identical to dentinogenesis
imperfecta (DI) type II in the primary dentition with yellow-brown
to blue-gray discoloration of the teeth and pulpal obliteration.
However, in DD II the permanent dentition is normal in color
or minimally discolored, but displays abnormal pulpal morphology
that can appear shaped like a thistle tube in the anterior
teeth . Pulp stones also
are common in the permanent teeth. Due to the similar phenotype
of the primary teeth and known similar gene loci DD type II
and DI type II it was speculated that DD type II could be
an allelic mutation of the gene responsible for DI type II
. Indeed studies now show
that in at least some families DD type II is caused by mutations
in the DSPP gene which is associated with DI type II.
and Dentin Formation
|Dentin is the most abundant dental tissue and
largely determines the size and shape of teeth. Dentin is
formed by odontoblast cells. The unique structure and composition
of dentin allow it to function as the substructure for the
rigid enamel tissue, thereby imparting teeth with the ability
to flex and absorb tremendous functional loads without fracturing.
Dentin contains about 60% mineral by weight and, unlike enamel,
has a substantial organic component (20%). Dentin contains
a complex organization of tubules (Figure 22) that are approximately
1um in diameter, filled with fluid and/or the cellular processes
of the odontoblasts and are thought to play a role in the
neurosensory function of teeth .
Additional dentin can be deposited along the tubule (sclerotic
dentin) or the pulpal wall in a reparative or protective mode
in response to environmental stimuli such as trauma, tooth
wear, or dental caries.
Dentin formation involves numeorus genes
that produce a complex extracellular matrix that is highly
organized, is processed, sand that eventually mineralizes
in a highly controlled fashion. Type I collagen (product
of COL1A1 and COL1A2 genes) is the most
abundant dentin protein .
This complex molecule has the structure of a heterotrimer
and forms the foundation for several mineralized tissues
including bone and dentin. The collagen molecules interact
with a variety of non-collagenous proteins to help initiate
and regulate the mineralization process in these tissues.
Interestingly, mutations in either type I collagen or proteins
that interact with it can cause the DI dental phenotype.
There are known to be hundreds of different mutations
in these two genes that are associated with osteogenesis
imperfecta, a group of hereditary defects associated with
bone fragility. Interestingly only some of the collagen
mutations result in the dental manifestations of dentinogenesis
There are numerous non-collagenous proteins present in
dentin, some of which interact with collagen to initiate
and/or regulate mineralization .
The most abundant non-collagenous protein, dentin sialophosphoprotein
(product of DSPP gene) is a highly phosphorylated
protein. That attaches to the type 1 collagen fibril
helping regulate mineralization at specific sites within
the collagen. Mutations in either type 1 collagen
or DSPP can alter this interaction resulting in abnormal
mineralization and a DI dental phenotype.
For additional information on dentinogenesis see the following
reviews: [58, 59]
The dental pulp is a specialized tissue comprised of a layer
of odontoblasts, fibroblasts, blood vessels, nerves and
a complex extracellular matrix. The pulp provides the reparative
potential of teeth and neurosensory function.
The dental pulp can increase production of dentin (reparative
dentin) in an attempt to protect and wall off the vital
pulp tissue from the injury or noxious stimuli.
Prompt treatment of dental trauma and dental caries are
critical steps towards maintaining a healthy vital pulp
and allowing an injured or diseased tooth to retain a vital
pulp. The pulp will continue to lay down small amounts of
dentin throughout the life of a tooth as part of the normal
pulp physiology. This
process ultimately results in a smaller pulp chamber in
people as they age and is part of the reason teeth continue
to become more yellow in color with age. It is especially
critical to maintain a healthy dental pulp until the root
is fully formed and its walls are of adequate thickness
to maintain the tremendous forces transmitted from the crown
during function. If the pulp becomes non-vital in a young
tooth that lacks complete root formation, it is much more
difficult to complete endodontic treatment successfully
and the prognosis for retaining the tooth is diminished.
For more information on genes in teeth link to http://bite-it.helsinki.fi/.