Exposure to microgravity and the space environment during short and long duration space missions has important medical and health implications in astronauts. Numerous counter measures have been developed and tested for moderating these physiological changes. The acclimatisation of astronauts to these conditions is of utmost importance. Aeronautical dentistry is a newly recognized speciality in dentistry concerning the application of dentistry to aeronautical environments. Various orofacial structures are affected in an outer space. An aeronautic dentist has to be prepared to screen and select only those astronauts with optimal oral health. Also, an aeronautic dentist has to be prepared to face any emergencies that may arise due to exposure to microgravity. This article highlights the effects of microgravity on human body with emphasis on orofacial structures.
Human physiological adaptation to the conditions of space is a challenge faced in the development of human spaceflight. Investigating the effects on the human body of such prolonged exposures in space is vital in the preparation for such journeys. Advances in aerospace technology in the twentieth century provided humans with an opportunity to encounter a microgravitational (almost 0 g) environment. Astronauts experience weightlessness during space flight. Because the human body is designed to live in a 1-g environment, as on earth, exposure to microgravity causes significant changes in body functions. Exposure to microgravity and the space environment during short- and long-duration space missions has important medical and health implications in astronauts. These include neurovestibular problems involving space motion sickness and disorientation during flight, as well as impaired balance and neuromuscular coordination after landing; cardiovascular and fluid-related problems of orthostatic hypotension immediately after spaceflight; altered cardiac susceptibility to ventricular arrhythmias; reduced cardiac muscle mass and diminished cardiac function; muscle-related problems of atrophy involving loss of muscle mass, strength, and endurance; decreased bone mineral density (BMD); circadian rhythm-related problems involving sleep and performance; and immune-related problems involving infections and immunodeficiency. Numerous countermeasures have been developed and tested for moderating these physiological changes. These procedures include careful screening and selection of new astronaut candidates and drug and exercise regimens during or after flight, which ensure the prompt return of crew members to flight status [ 1 – 6 ]. With the foray of mankind into outer space, there have been many advances in the field of health sciences related to this rather unseen world. The microgravity experienced in space missions has serious effects on human physiology including the teeth and surrounding orofacial structures. Human physiologic adaptation hence becomes a major challenge faced in the development of human spaceflight. Very few studies have been published on the effects of microgravity on the oral cavity. However, there are reports suggesting that the prevalence of periodontitis, dental caries, bone loss and fractures in the jaw bone, pain and numbness of teeth and oral cavity tissue, salivary duct stones, and oral cancer are more prevalent after exposure to simulated microgravity, as compared with normal 1-g earth environments. Bearing all this in mind, a new field of aeronautic dentistry has been introduced to facilitate dental research and practice in aeronautical environments. Aeronautic dentistry is a specialized branch of dentistry that deals with the study of the application of dentistry in the aeronautical environment. This term was coined by Dr. Balwant Rai in 2007 [ 7 ]. This paper discusses the various physiologic adaptations encountered in astronauts with a special account of changes in orofacial structures along with the modalities practiced in order to compensate for these physiologic changes in astronauts before, during, and after spaceflight.