The thyroid gland is a small endocrine gland, shaped like a butterfly, and positioned in the front of the neck, specifically in front of the windpipe and larynx. It produces T3 (triiodothyronine) and T4 (thyroxine) hormones, which regulate many bodily functions, including growth, metabolism, and energy expenditure. If these hormones are not within the normal range, thyroid problems such as hyperthyroidism and hypothyroidism can develop. When thyroid issues are left untreated or become severe, they can lead to other medical conditions, including infertility, heart disease, and peripheral neuropathy.
Furthermore, the thyroid gland is one of the most radio-sensitive areas of the body, especially in infants and children. Ionizing radiation exposure to the thyroid gland can destroy the thyroid cells that absorb iodine, resulting in goiter. Years later, the exposed individual may develop thyroid cancer. Moreover, radiation exposure increases the risk of hypothyroidism, benign thyroid nodules, and autoimmune thyroid disease. Thankfully, a thyroid lead shield can help protect the thyroid gland from harmful exposure to X-rays and gamma rays.
For dental patients undergoing radiographic exams, such as dental X-rays, the use of a thyroid lead shield or collar is necessary when the thyroid is within the primary beam, often in cases requiring a maxillary anterior occlusal radiograph. The thyroid lead shield is tightly wrapped like a collar around the neck and fitted below the patient’s chin. It is typically made of a sheet of approximately 0.5 mm lead or at least 0.25 mm thick lead-equivalent material. This shield works to block maximal ionizing radiation exposure to the thyroid.
The dose of radiation exposure is typically influenced by the type of dental radiograph being used, which also determines the level of potential damage to the thyroid gland and the need for a thyroid lead shield.
When the radiation exposure is high or prolonged in the upper anterior part of the jaw, it is especially recommended that children, adults up to the age of 50, and pregnant females wear thyroid lead shields, as they are more susceptible to harmful radiation effects. In cases where equipment uses automatic radiation exposure control based on scout images, the thyroid shield must be fitted only after the patient’s scout images are taken. The scout image is a low-resolution X-ray projection taken before a CT or MRI scan to ensure optimal radiation use and accurate imaging of the right anatomical structures.