Oral Findings In Osteogenesis Imperfecta

Stephane Schwartz,
McGill University and the Montreal Children's Hospital, Montreal, Canada

Osteogenesis Imperfecta (OI) is always associated with bone fragility. However, it may or it may not affect other areas, such as the eyes (blue sclerae), audition (hearing loss), joints (hyperextensibility), cardio-vascular system (valves and arteries) or teeth (dentinogenesis imperfecta (DI)).

The abnormal condition of the teeth in some patients with OI has been reported as early as the 20's. Authors were impressed with the unusual color of the dentition, and because the defective tissue was the dentin, the condition became known as dentinogenesis imperfecta. Since then, the syndrome has been well documented both clinically and microscopically. An example of the findings was that if DI affected one member of a family with OI, then all the members of that family were also affected by DI; and likewise that if one member of a family with OI was not affected with DI, then no other member of that family would have DI. This is one of the factors which helped classify the various types of OI.

It was also noted that the severity of the case of DI bore no relation to the severity of the skeletal involvement in the case of OI. However skeletal involvement does affect other parts of the oral cavity, mostly at the level of the patient's occlusion. There is a direct relation between the two. This is why, in oral findings of a patient with OI, we distinguish between the teeth and the rest of the oral cavity.

ORAL FINDINGS

Malocclusions: Malocclusions may be defined for our purposes as an abnormal relationship between the upper and the lower jaw. The skeletal features found in OI are largely responsible for the specific malocclusions of those patients where large head size, frontal and temporal bossing, and exaggerated occiput create a greater percentage of Class III malocclusions. Anterior and posterior cross bites and open bites are also frequent. These conditions seem be caused not so much by an excessive growth of the mandible but rather by a deficiency of the maxilla. Clinical studies have shown a higher number of OI individuals with a Class III malocclusion than with DI. .Malocclusions caused by skeletal discrepancies cannot be corrected by orthodontics alone. Changes in the position of the basal bones also may require orthognatic surgery.

Impactions and ectopic growths: A surprising large number of impactions and ectopic growths have been reported. This occurs when the teeth do not follow the normal path of eruption (ectopic growth) or when they fail to erupt (impaction). OI patients in permanent dentition often have unerupted first and second molars, a condition which is rare in the general population. These abnormalities have no relation to the existence of DI.

Dental findings: DI represents the disturbance in tooth formation associated with OI, and is one of the most significant clinical patterns of OI. It can be the only bone abnormality. Therefore, clinical and radiological evaluations of a dentition may be the only affirmative component in the diagnosis of a questionable case of OI. The DI teeth are affected in their colour, shape, wear and dentinal tissue. The primary dentition is always more affected than the permanent dentition.
- Colour. The colour can be grayish (opalescent) to yellow-brown, and usually intensifies with age. It can become cosmetically questionable. The lower incisors are always more affected. The discolorations are intrinsic, which means they come from within the teeth, and cannot be easily whitened even though some success has been obtained.
- Shape. Radiographically the teeth show bulbous crowns with a constriction at the coronal-radicular junction. The roots are shorter and more slender than normal. The pulpal spaces are narrow or obliterated, and longitudinal observations on radiographs show that the obliteration is progressive.
-Attrition and fractures. All authors have observed the attrition sustained by DI teeth. Fractures en masse are also reported. Both are more severe with yellow-brown discoloured teeth than with opalescent gray ones, and the primary dentition is more severely affected than the permanent.
-Dentinal tissue. Light and scanning electron microscopy (SEM) has been used to examine the dental tissue to determine why DI teeth tend to fracture spontaneously at the level of the enamel or at the level of the crown. A lack of normal scalloping at the interface of the enamel and the dentin has been identified as being responsible for the enamel attrition because it could not provide the mechanical bonding between the two tissues. Therefore, even if the enamel of the teeth with DI is normal anatomically, it may not attach normally to the dentin. Others have found normal scalloping. But even with normal scalloping, the DI teeth tend to fracture en masse through the crown, caused possibly by abnormal dentin. This abnormality in the appearance and organizational pattern of collagen fibers resembles those in the skin of patients with generalized connective tissue disease. Interestingly, it has been recently discovered through SEM and amino-acid analysis, that the dentin of OI patients who had no clinical or radiographic signs of DI in their teeth, may still have clearly-defined microscopic abnormalities. Clearly further research is needed.

Recommendations:

Patients with OI and opalescent teeth should be evaluated as soon as the deciduous teeth erupt. Each case presenting a malocclusion should be considered in consultation with all the health professionals involved in the treatment of that particular patient. Only then can the best treatment for each individual be designed and carried out.

When a child with DI shows a tendency to sustain dental fractures, dental treatment to help prevent such accidents is available, such as ready-made crowns for the primary dentition and tooth-coloured crowns for the permanent dentition. Unaesthetic colours and defects can be masked by veneers, which can cover the labial surfaces of the affected teeth. Porcelaine fused to metal crowns may cover and protect fragile or unaesthetic teeth or replace missing teeth.

There is a need for clear guide lines for the dental management of OI individuals.

Reference: Proceedings of the 7th International Conference on Osteogenesis Imperfecta. Montreal, Canada, 1999.