244 Theories and techniques of oral implantology

More than likely, the operator will not interview a prospective candidate suffering from infantile hyperpituitarism or hypopituitarism. However, in later life an overactive pituitary may produce acromegaly, an enlargement of the extremities, jaws, and bones of the skull. Acromegaly occurs in some pregnant women to a slight degree and will regress after the baby is born. Acromegaly can be controlled, but implants are not advised because occlusion can change as the bone changes. Naturally, in pregnant women implantation should be delayed until after delivery for several reasons that will be discussed later.

Cushing's disease, or pituitary basophilism, is a rare disease more common in women than men. It causes bone to become brittle and lose a consider-able amount of its mineral components. Here, as with most other pituitary diseases, implants are not advisable. Many of these diseases can be controlled, but on a touch-and-go basis. Potential imbalance is great, and an implant requires a stable environment to be securely set.

Thyroid disorders. The thyroid gland influences the rate of metabolic activities in all the cells of the body in some as yet not clearly understood manner. There is a great deal of variation in the normal basal metabolic rate (BMR) among individuals, and the BMR rises and falls in an individual according to his activity. As long as the BMR is normal for that patient, whether it is high or low, implants are not contraindicated. However, sudden, prolonged changes in the BMR indicate disease, and implants should be postponed until the patient is restored to good health.

If, for any reason, the thyroid gland is absent or unable to produce adequate amounts of thyroxine, hypothyroidism develops. In its extreme form, myxedema, the tongue greatly enlarges and would constitute a threat to implants.

Adrenal disorders. Hypofunction of the adrenal cortex produces a syndrome known as Addison's disease, which occurs equally in both sexes and at any age. Addison's disease is characterized by a bronzing of the skin or pigmentation of the gingiva.

Parathyroid disorders. The parathyroids secrete a hormone that maintains the calcium-phosphorus equilibrium in the blood. Whenever there is insufficient circulating calcium, calcium is mobilized from the bones through the mediation of the parathyroids. Thus the parathyroids play an important role in calcium metabolism.

In hypoparathyroidism, marked hypocalcernia

with resultant increased excitability of the nervous system occurs. In many patients suffering from this disorder, radiographs show peculiar trabeculation of alveolar bone, with some degree of resorption of the bone and of the roots of the teeth. The enamel and dentin calcification are also disturbed. These symptoms alone should contraindicate the use of implants.

An increase in the parathyroid hormone results in hyperparathyroidism, which is characterized by an immediate rise in serum calcium and an increase in the excretion of calcium. The rise in serum calcium is brought about by the mobilization of calcium from the bones. This is accomplished by direct osteoclastic action and a generalized resorption of bone (osteitis fibrosa generalisata). Osteitis fibrosa cystica results. Generalized and marked osteoclasis occurs at the sites of the most active bone deposition, because it is in these areas that the cellular and vascular elements are most active and abundant. The resorption is therefore localized mostly in the spongy bone trabeculae, including those of the alveolar bone of the jaws (Fig. 6-53). Therefore, again, implants are contraindicated.

Pancreatic disorders. To the implantologist, the most significant "pancreatic" disorder is diabetes mellitus, which was originally thought to result from a hypofunctioning of the islets of Langerhans, which produce insulin. Current evidence, however, indi-

Fig. 6-53. When osteoporosis and granularity are seen, hyperparathyroidism should be suspected. (From Worth, H. M.: Principles and practice of oral radiographic interpretation. Copyright 1963 by Year Book Medical Publishers, Inc. Used by permission.)