descriptive, title. The condition is an autosomal dominant trait with both dentitions
being affected. The teeth may be clinically normal but root formation is abnormal to
varying degrees. Some teeth may have extremely short blunt roots, others taper
markedly towards the apex (867HFig. 13.42). The pulp is partially obliterated, appearing in
the molar teeth as a small demilune. Under the microscope the coronal dentine is
normal but the root dentine is not, with masses of abnormal dentine obliterating the
pulp space. The microscopic appearance has been likened to boulders in a flowing
stream. The short roots may cause problems because of mobility and this may lead to
the condition being identified.
The above condition is often referred to as dentinal dysplasia type I to distinguish it
from a condition referred to by some as dentinal dysplasia type II (coronal dentinal
dysplasia). The latter is most likely to represent an allelic variant of dentinogenesis
imperfecta as genetic linkage studies have shown it to map to the same region of
chromosome 4 as dentinogenesis imperfecta and a mutation in the DSPP gene has
also been identified in one family diagnosed as having dentinal dysplasia type II.
It remains to be seen whether dentinal dysplasia (type I) is also allelic to
dentinogenesis imperfecta.
VITAMIN D-RESISTANT RICKETS
Vitamin D-resistant rickets is an X-linked inherited condition. Affected males tend to
be short in stature with bowed legs and other skeletal changes. They may present
dentally with abscesses forming in the absence of caries. Of the dental hard tissues,
the dentine is most markedly affected with interglobular dentine being the chief
histopathological finding. Radiographically the pulp spaces are larger than normal and
pulpal extensions of the pulp horns may be exposed as a result of attrition of the teeth
(868HFig. 13.43) Heterozygous females tend to be more mildly affected and may not
exhibit any dental manifestations.
'Environmentally determined' dentine defects
Local trauma may interfere with dentine formation. This may be permanently
recorded in the dentine as a prominent incremental line. Systemic influences including
nutritional deficiencies, tetracycline administration, and chemotherapeutic agents such
as anti-cancer therapy involving cytotoxic drugs can also affect the formation of
dentine.
Treatment
As with enamel defects there may be severe psycho-social problems as a result of the
appearance of the teeth. Many of the arguments presented in the consideration of
enamel conditions will apply to dentine also. In dentinogenesis imperfecta,
management is focused on the prevention of tooth wear, the maintenance of the
vertical dimension and improvement of the appearance (869HChapter 10). In rickets, the
treatment should be similarly directed but cases presenting late may require acute
management of dental abscesses on the teeth as a result of pulp death.