Microgravity led to increased dental plaque, tartar formation, and gingival inflammation, complicating oral hygiene practices for astronauts during space missions.
A recent review explored the impact of space travel on astronauts' oral health, emphasizing the unique challenges posed by microgravity and radiation exposure. The study examined how these factors influenced saliva production, microbial balance, and overall oral hygiene.
Prolonged space missions were associated with an increased risk of dental issues such as caries, periodontal diseases, and discomfort among astronauts. Increased levels of oral bacteria and delayed wound healing were observed, indicating the need for comprehensive dental care in space.
The review, published in the Journal of Applied Dental and Medical Sciences, evaluated current dental practices and strategies for maintaining oral health during space missions. Effective countermeasures were necessary to address the physiological effects of microgravity, including fluid redistribution, musculoskeletal alterations, and changes in the vestibular and sensorimotor systems. These physiological changes impacted the oro-facial region, contributing to dental fractures, sensory abnormalities, and potentially increasing the risk of oral cancer.
Barodontalgia, or tooth pain caused by pressure changes, and odontocrexis, or tooth fractures due to barometric pressure changes, presented concerns. These conditions resulted from new or recurrent caries, pulpitis, and periodontal abscesses. Historical data from the Apollo-17 mission and subsequent studies estimated a potential risk of in-flight dental events that could affect crew productivity.
To mitigate these risks, the review suggested the inclusion of a dentist and a laboratory physician on extended missions. Preventive measures included using a zinc oxide-eugenol base to prevent barodontalgia in cases of reversible pulpitis and avoiding procedures like pulp capping before significant pressure changes.
The review also noted that space travel induced significant physical and physiological changes due to microgravity, altered radiation, atmospheric pressure changes, temperature fluctuations, and density variations. These factors caused fluid redistribution and musculoskeletal alterations, necessitating adaptations in astronauts' vestibular and sensorimotor systems. Additionally, astronauts faced psychological effects, changes in microbial flora, and immunological alterations. The oral and maxillofacial region was also impacted, leading to dental issues such as caries, periodontal diseases, fractures, pain, sensory abnormalities, and oral cancer.
Adaptation strategies were crucial, prompting scientists to develop methods for managing oral health. The emerging field of aeronautical dentistry focused on dental care in space, and strategies to maintain dental health during prolonged missions were discussed.
The review noted that while dental emergencies were rare during short missions, they posed significant risks during extended ones. Historical accounts, such as the 1972 Apollo-17 mission, had an incidence rate of 0.01% per 100 days. In 1977, Brown et al. estimated a 0.92% risk of an in-flight dental event affecting crew productivity. The Integrated Medical Model identified several dental conditions, such as cavities, abscesses, pulpal exposure, tooth avulsion, and the need for replacing dental crowns and fillings, as potential reasons for evacuating astronauts from the International Space Station.
Advances in space medicine revealed parallels with aging physiology, affecting multiple systems and necessitating alternative treatments like transcranial magnetic stimulation (TMS) for conditions such as dysphagia and burning mouth syndrome. Space travel elevated bacterial activity due to confined conditions, increasing rates of periodontitis and caries. Spaceflight induced immune challenges, with reactivation of dormant herpes viruses due to microgravity, stress, and radiation. Alterations in white blood cells, reduced T cell effectiveness, and changes in cytokine secretion were observed. Salivary gland gene expression underwent significant changes influenced by various factors, including functional activity and neurohormonal stimulation.
Microgravity-induced fluid redistribution reduced saliva flow, causing xerostomia, while increased bone resorption elevated salivary calcium salt saturation, raising the risk of calculi formation. Environmental and dietary factors also worsened the situation. Prolonged missions heightened cancer risk and induced muscle wasting. Pre-breathing oxygen prevented decompression sickness during spacewalks, but radiation exposure on the International Space Station surpassed Earth's levels, elevating cancer risk. Interplanetary travel exacerbated this risk due to the absence of Earth's protective magnetosphere.
Microgravity reduced drug effectiveness, and barometric pressure changes could cause dental injuries. Osteoblast activity decreased, leading to monthly bone density loss of 1-2%. Traumatic injuries during space exploration raised the risk of jaw and dental injuries. Disrupted cortisol and melatonin regulation could lead to temporomandibular joint discomfort. Persistent stress triggered bruxism and raised infection risks, while safety protocols targeted mortality rates below 3%. Decreased medication effectiveness led to crew dissatisfaction, and altered drug absorption affected treatment outcomes.
To address these challenges, astronauts received education on healthy diets and were encouraged to maintain scrupulous oral hygiene practices. Regular checkups were conducted, and the National Aeronautics and Space Administration had stringent criteria for selecting, retaining, and evaluating crew members' oral health. Comprehensive clinical protocols involved annual oral examinations, with astronauts classified into three groups based on their oral health status. Overall, emphasizing prevention and maintaining oral health were vital for the success of space missions.
Future research directions and prospects in aerospace dentistry depended on technological breakthroughs and comprehending space's influence on oral health. Prominent advancements included 3D printing for personalized dental prostheses, nanotechnology for radiation-resistant dental materials, and tele-dentistry leveraging artificial intelligence and wearable devices for continuous astronaut monitoring. Investigating personalized medicine and integrating artificial gravity held significant promise. Long-term research on microgravity's effects on orthodontic tooth movement was imperative, necessitating extended space missions to monitor changes and evaluate the effectiveness of proposed solutions.
The authors reported no conflict of interest.