The two major risks to the developing fetus caused by excessive exposure to radiation are development of cancer and mental retardation. It appears that 10 microsieverts (µSv) of radiation is the level required for either effect to occur.22 With proper radiographic techniques and precautions, the amount of radiation exposure from dental x rays ranges for bitewing radiographs from 26 µSv (skin dose) 0 µSv (thyroid dose), and for full mouth series from 90-122 µSv (skin dose) to 117-550 µSv (thyroid dose). To put these values in perspective, background radiation from natural occurring sources is approximately 3,100 µSv annually.23 The fetus is most sensitive to the effects of radiation between the eighth and 15th weeks after conception, a period of major neuronal and organ development.24 Proper radiographic techniques, such as rectangular collimation, lead shielding (abdominal and thyroid), use of the fastest available films (E/F speed film or digital), use of a long cone and avoidance of retakes, ensure that radiation exposure to the pregnant patient and fetus is minimized. However, even with observance of these precautions, the dental x-ray beam may pass through or near the thyroid gland. The juvenile thyroid is very sensitive to radiation induced tumors, both benign and malignant. In addition, thyroid radiation exposure during pregnancy is associated with infant low birth weight. If dental treatment will be deferred until after delivery, so should dental radiographs.25,26
Patients who are reluctant to accept necessary radiographs should be explained the risk of complications is so low it is impossible to measure. There is more risk to the fetus associated with lack of dental care than in providing treatment that includes dental radiographs. Lack of radiographs allows for inaccurate diagnosis which may lead to pain and infection, which could ultimately harm the fetus. Providing treatment, such as endodontic therapy or extractions without radiographs, may be considered substandard treatment. Dental radiographs are an integral part of any dental examination or treatment.27
The following points should be discussed with the pregnant patient (adolescent and adult) as part of the consultation.