Every 6 months. Every 5 years or as indicated. There has never been a single instance reported in the dental or scientific literature of a patient contracting a malignancy because of dental x-rays. The amount of radiation received from dental machines is as little as one twentieth of the power of a medical x-ray machine. Yet, the benefits to be derived from necessary dental x-rays are far greater than the hazards.
Most people feel that such a real saving in health or economic costs is worth it.
Radiation comes to us from natural sources too. We breathe radioactive radon in the atmosphere. We're exposed to cosmic radiation from space and terrestrial radiation from radioactive isotopes in stone and building materials. In addition to natural radiation we get radiation from tobacco smoke, watches with luminous dials, color television sets and computer screens. A complete dental exam gives about one and half day's worth of radiation exposure.