Treatment of Amelogenesis lmperfecta vvith Gnathological Procedures

INTRODUCTION

Thomas G. Brown, D.D.S. La Jolla, Calif. U.S.A.

Amelogenesis lmperfecta is a unique disease which affects the enamel of both primary and secondary dentition. The condition has been described as enamel aplasia, enamel dysplasia, brown hypoplastic enamel, or just "brown teeth", often with "hereditary" added.3 Surveys in the United States have shown the occurrance of one case of amelogenesis imperfecta for fourteen to sixteen in-dividuals. 1 These teeth have a tendancy for impaction, have normal dentin structure, and show resistance to caries. The tendancy to multiple impaction is explained by the fact the reduced enamel epithelium appears to be defective and, therefore, is not able to contribute to eruption in the normal way. It has been reported, in 1956, that tetracycline may give rise to enamel hypoplasia.2

Tetracycline reacts with calcium to form a tetracycline calcium or-thophosphate complex, therefore, any tissue undergoing mineralization when the drug is given has not only calcium deposits, but also the tetracycline molecule in it. This condition is generally noted in the administration of moderate to heavy doses of tetracycline before the age of sixty-six days.

Clinical signs are generally recognized at an early age. The cause of the disorder is unknown and in its familial pattern behaves as a dominant mendelian defect with sex-linked characteristics.

The matrix of the enamel organ contains about 65% organic material and water and about 35% inorganic elements. During the second phase of development, the organic material and water are removed and replaced with mineral salts, which eventually con-stitute about 95% of the enamel. 4 A disturbance in the primary state of tooth development results in hypoplasia with definite alterations in the shape of the tooth. The small amount of formed enamel is fully calcified so that the tooth is as hard as a normal tooth. A disturbance during the second phase results in hypocalcification. Here, the matrix deposited is normal in quantity and quality, but calcification is not complete. Because of the poor quality of the enamel, it is readily worn away, leaving the exposed dentin. In either instance, the poorly formed enamel leads to trauma to the underlying dentin and hence, sclerosed dentin is a common microscopic finding.

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At least six conditions have been described under the term amelogenesis imperfecta and appear to be distinct entities. 5 Pro-bably more exist, but descriptions given in the literature are not sufficient to differentiate the conditions clinically, or the family kin-dreds are not sufficiently extensive to determine the mode of in-heritance. In the case in which I was involved, I was unable to demonstrate any hereditary incidence in the family. However, they were of a lower middle class background and were hesitant to discuss the family or child other than they could not remember anyone else within the family possessing such dental characteristics.

TYPES OF AMELOGENESIS IMPERFECTA

Types of amelogenesis imperfecta most commonly seen are hypoplastic, hypocalcified, local hypoplastic, hypomaturation, and pigmented hypomaturation.

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Hypoplastic Type In this type, both primary and secondary dentition ar~ involved. The enamel fails to develop a normal thickness and on newly erupted teeth may be from 1 /8 to 1 I 4 the thickness of normal enamel. The teeth may appear small and usually do not meet at the contact areas. The surface of the enamel may be hard, rough and granular, or globulated with regular enamel clumps. Some areas of enamel may be white, but generally vary from yellow to yellow-brown in color. When the teeth have been within the environment of the oral cavity for some time, areas of exposed dentin may be seen on the occlusal surfaces, incisal edges and any surface receiv-ing tooth brushing. There may be sensitivity to varying degrees of

Fig. 1. Kindred of hereditary hypoplastic type of amelogenesis imperfecta. The affected father transmitted the trait to all of his daughters but to none of his sons, compatible with a sex-linked dominant mode of inheritance. [Haldane, J.B.$.; probable new sex link dominant in man, J. heredity, 28:58, 1937.J

Treatment of Amelogenesis lmperfecta with Gnathological Procedures

hot or cold, but this complaint may not be shared with other relatives not possessing the defect. Radiographically, the only in-dication may be a radiopaque tracing of the crown. The mor-phology of the roots, periodontal membrane and pulp chamber ap-pear to be normal. The condition appears to be inherited as a sex-linked dominant trait (Fig. 1).

Hypocalcified Type This is the most common type of primary amelogenesis imperfecta, affecting both the primary and secondary dentition and is characterized by a soft friable type of enamel that can be removed from newly erupted teeth with a sharp instrument. The teeth will vary from brown to dull yellow in color, however, the soft enamel may become darkly stained shortly after eruption. In the adult, the enamel may be completely worn away. Radiographically, the crowns may have a moth-eaten appearance. Roots, periodontal membrane and pulp chambers appear to be normal (Fig. 3,4). It has been estimated the organic content of this type of enamel is 8.66%, as compared with normal enamel of 4.88%. Figure 2 demonstrates a kindred of hereditary hypocalcified type amelogenesis imperfecta demonstrating an autosomal dominant mode of inh~ritance.

Hypomaturation Type This type affects both primary and secondary dentition, however it is rare and has been reported only in males. Enamel has a ground-glass opaque appearance and is not as hard as normal enamel. Local areas of hypoplasia may be present and the surface of the enamel may be soft enough to allow the tip of a sharp instrument to be forced into it. Radiographically, there is a lack of normal con-trast between the enamel and dentin.

The cervical portion of the crown may be better calcified and the morphology of other dental structures appear to be within normal limits. This condition is inherited as a sex-linked recessive trait.

Pigmented Hypomaturation Type This condition is extremely rare and has been reported in only two families. Both primary and secondary dentition were affected with the enamel possessing a shiny, agar, jelly appearance and softer than normal enamel. The enamel will tend to chip or fracture away from the dentin. There is a lack of contrast between enamel and dentin radiographically, but all other dental structures appear to be normal. There is a heavy brown pigment demonstrated through the enamel and is noticeable in the middle third of the tooth. The pigment appears to be a blood pigment, however, histochemical reactions are negative. Medical history and clinical study of these

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Fig. 2. Kindred of hypocalcified type of amelogenesis imperfecta ii· lustrating an autosomal dominant mode of inheritance [Tiecke, R. W. oral pathology 1965.)

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patients do not reveal any associated hematological or biochemical defect which could be related to the pigment deposition. Both males and females have been affected, but parents and remote relatives are not. The condition can be inherited as an autosomal recessive trait.

Local Hypoplastic Type This type may affect .both primary and secondary dentition or just the primary dentition. The enamel possesses numerous pits, fissures and hypoplastic lines traversing the enamel horizontally around the crowns, resembling the type of hypoplasia seen in severe febrile disease during tooth development. The most fre-quently observed hypoplastic areas of enamel are the incisors and molar teeth in the primary dentition and the incisors, bicuspids and permanent first molars of secondary dentition. Thereby, a pattern not consistent with a febrile etiology. There may be a variation in

REFERENCES

Treatment of Amelogenesis lmperfecta with Gnathological Procedures

imperfecta are within normal limits, this also supports the treat-ment of full mouth reconstruction. Posterior stabilization of occlu-sion is readily obtained if proper gnathological procedures are followed. The cosmetic changes of the anterior teeth will show a marked psychological change in the patients. In late adult cases where extensive loss of tooth structure has occurred, full mouth extraction and full dentures may be preferred by the patient depen-ding upon economic and psychological factors. The complicating factor of a severe open bite reinforced the necessity for extremely accurate restorative procedures. A gnathological system of treat-ment with a fully adjustable articulator helped insure a satisfactory end result. Myofunctional training was a distinct aid in reversing a destructive relapse of restorative procedures. Earlier timing possibly would have supported a more functional end result. This process of swallow retraining is open to much discussion. The methods utilized were successful, dramatically improving the pa-tient's function, appearance and morale.

1. Witkop, C.J.: Genetics and Dentistry: Eugen. Quart.: 1958: 5: 15-21 2. Pinkborg, J.J.: Pathology of the Dental Hard Tissues: Philadelphia, Pennsylvania, 1970:

W.B. Saunders: Chapter 3, pp 171. 3. Pindborg, J.J.: Pathology of the Dental Hard Tissues: Philadelphia, Pennsylvania, 1970:

W.B. Saunders Co.: pp 77 4. Tiecke, R.W.: Oral Pathology: New York, 1965: McGraw-Hill, Inc.: pp 239 5. Tiecke, R.W.: Oral Pathology: New York, 1965: McGraw-Hill, Inc.: pp 801 6. Hoffman, R.W., Regenos, J.W., Taylor, R.R.: Principles of Occlusion Teaching

Manual: Columbus, Ohio, 1969: H&R Press 7. McCollum, 8.8., Stuart, C.E.: A Research Report: Los Angeles, California: 1955: Scien-

tific Press. 8. Garliner, D.: Myofunctional Therapy in Dental Practice: 1st Edition: Brooklyn, New

York, 1971: Bartel Dental Books Company.

Dr. Thomas G. Brown m1 Herschel Ave. La Jolla, Calif. 92037 U.S.A.

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The basic difference between Gnathology and Dentistry in restoring physiology to the mouth is that in Gnathology the entire mouth is treated as a unit instead of one tooth at a time, or in sec-tions. If the entire mouth is not treated as a unit, any existing malocclusion will be perpetuated and amplified.

Filling one cavity, making one crown, or bridge, a Dentist frequently starts the role of mal-mechanics by not properly restoring the elements of occlusion. This leads to destruction of the supporting tissues, wears the teeth, · and strains the jaw joints.

In Gnathology the mechanics of the mouth is organized so that it will not be self destructive. This organization of teeth is named Organic Occlusion and represents the highest mechanical order that can be given to the teeth .

All cusps, ridges, grooves etc ., must be restored and in the correct location and design geared to the three dimensions of measured mandibular movements with the lower jaw correctly related to the cranium.

Gustav Swab, D. D.S .