Bone mineral density, bone mineral content, gingival crevicular fluid (matrix metalloproteinases, cathepsin K, osteocalcin), and salivary and serum osteocalcin levels in human mandible and alveolar bone under conditions of simulated microgravity

The Anti-Inflammatory Effect of Nigella sativa Toothpaste on Porphyromonas gingivalis Bacteria Through Decreased TNF-α, MMP-9, PGE-2 Expression in Wistar Rats

OBJECTIVE

 The main principle in preventing periodontal disease is to improve oral hygiene. The bacteria that cause the onset of periodontal disease, one of which is the Porphyromonas gingivalis bacterium, causes inflammation. Persistent inflammation causes tissue damage and alveolar bone resorption by secreting proinflammatory cytokines, matrix metalloproteinase-9 (MMP-9), prostaglandin E2 (PGE-2), and anti-inflammatory cytokines. In this case, preventive treatment is needed, such as using toothpaste that contains anti-inflammatories so that the progression of the disease does not get worse. The traditional ingredient currently being developed is Nigella sativa, which has anti-inflammatory properties. Therefore, this study analyzes the potential of toothpaste containing Nigella sativa on the expression of tumor necrosis factor-α (TNF-α), MMP-9, and PGE-2 in the Wistar rat model induced by Porphyromonas gingivalis bacteria. This study aims to prove the potential of Nigella sativa toothpaste to decrease the expression of PGE-2, TNF-α, and MMP-9 in the gingiva of rats induced by Porphyromonas gingivalis bacteria.

MATERIALS AND METHODS

 Forty-five healthy male Wistar rats were used, consisting of the negative control group, which was only injected with Porphyromonas gingivalis bacteria ATCC3322. The positive control group was given enzyme toothpaste, and the treatment group was assigned 1 mg of Nigella sativa paste using a microbrush for 30 seconds on the gingiva incisors mandibular with a circular motion, given two times a day for a week. Immunohistochemical to see the expression of TNF-α, PGE-2, and MMP-9. Parametric comparative analysis using a one-way analysis of variance test was performed to analyze differences between groups.

RESULTS AND DISCUSSION

 Nigella sativa toothpaste significantly reduced proinflammatory cytokines, as seen through the expression of TNF-α, PGE-2, and MMP-9 on days 3, 5, and 7 (p <0.05).

CONCLUSION

 In the limit of studied animal model, this trial indicates that giving toothpaste with black seed extract (Nigella sativa) could inhibit inflammatory mediators, as seen from the decreased expression of MMP-9, TNF-α, and PGE-2 seen from the 3rd, 5th, and 7th days.

Oral Health in Zero Gravity: A Comprehensive Review of Orofacial Effects and Countermeasures in Spaceflights

Space is a complex and challenging setting encompassing the region beyond Earth's atmosphere where astronauts and spacecraft operate. The unique conditions of spaceflights, particularly microgravity and radiation, pose significant challenges to astronaut health, including the orofacial region. It has effects on saliva production, microbial composition, and oral hygiene practices, which influence oral health status, such as increased risk of dental caries, gum diseases, oral discomfort, temporomandibular joint dysfunctions, sialoliths, pain and dysesthesia in the teeth and oral mucosa, masticatory muscle atrophy, and oral cancer which can be detrimental during prolonged missions. Hence, a comprehensive approach to dental care in space is imperative to ensure astronauts' well-being and overall health as we strive to extend our presence beyond Earth. This literature review paper sheds light on the intricate effects of space on the orofacial region and delves into the unique challenges astronauts face in upholding optimal oral health while in space. It explores the current state of dentistry in space and discusses advancements and strategies that aim to maintain optimal oral health for astronauts during extended space missions.

Impacts of microgravity on amino acid metabolism during spaceflight

Spaceflight exerts an extreme and unique influence on human physiology as astronauts are subjected to long-term or short-term exposure to microgravity. During spaceflight, a multitude of physiological changes, including the loss of skeletal muscle mass, bone resorption, oxidative stress, and impaired blood flow, occur, which can affect astronaut health and the likelihood of mission success. In vivo and in vitro metabolite studies suggest that amino acids are among the most affected nutrients and metabolites by microgravity (a weightless condition due to very weak gravitational forces). Moreover, exposure to microgravity alters gut microbial composition, immune function, musculoskeletal health, and consequently amino acid metabolism. Appropriate knowledge of daily protein consumption, with a focus on specific functional amino acids, may offer insight into potential combative and/or therapeutic effects of amino acid consumption in astronauts and space travelers. This will further aid in the successful development of long-term manned space mission and permanent space habitats.

Diagnostic potential and future directions of matrix metalloproteinases as biomarkers in gingival crevicular fluid of oral and systemic diseases

Gingival crevicular fluid (GCF) is a physiological fluid and an inflammatory serum exudate derived from the gingival plexus of blood vessels and mixed with host tissues and subgingival plaque flows. In addition to proteins, GCF contains a diverse population of cells, including desquamated epithelial cells, cytokines, electrolytes, and bacteria from adjacent plaques. Recently, matrix metalloproteinases(MMPs), which are endopeptidases that are active against extracellular macromolecules, in GCF have been revealed as potential utility biomarkers for the diagnosis and follow-up of oral and systemic diseases, thereby facilitating the early evaluation of malignancy risk and the monitoring of disease progression and treatment response. Tissue inhibitors of metalloproteinases (TIMPs) are specific inhibitors of matrixins that participate in the regulation of local activities of MMPs in tissues. This review provides an overview of the latest findings on the diagnostic and prognostic values of MMPs and TIMPs in GCF of oral and systemic diseases, including periodontal disease, pulpitis, peri-implantitis and cardiovascular disease as well as the extraction, detection and analytical methods for GCF.

A temporal study on musculoskeletal morphology and metabolism in hibernating Daurian ground squirrels (Spermophilus dauricus)

Hibernators provide a natural model to study the mechanisms underlying the prevention of disuse-induced musculoskeletal deterioration. Currently, however, these mechanisms remain poorly understood. Here, we investigated changes in morphology and metabolic indices in the hindlimb skeletal muscle and bone of Daurian ground squirrels (Spermophilus dauricus) during different periods of hibernation, and further explored the possible mechanisms involved in the musculoskeletal maintenance of hibernators after prolonged inactivity. Results showed that, compared with levels in the summer active group (SA), almost all morphological indices of skeletal muscle and bone, including muscle mass, muscle fiber cross-sectional area, bone mass, bone length, and bone mechanical properties, were unchanged in the different periods of hibernation. Only a few microstructural parameters of bone showed deterioration in the post-hibernation group (POST), including increased specific bone surface (+71%), decreased trabecular thickness (-43%), and decreased average cortical thickness (-51%) in the tibia, and increased trabecular separation (+60%) in the femur. Furthermore, most examined metabolic indices involved in muscle protein turnover and bone remodeling were unchanged, except for several indices in the inter-bout arousal group (IBA), i.e., increase in the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1) (IBA vs. SA, +80%) in the vastus medialis muscle, increase in chymotrypsin-like activity (IBA vs. SA, +62%) in the tibialis anterior muscle, increase in osteoblast number (IBA vs. SA, +110%; IBA vs. torpor (TOR), +68%) and osteoclast number (IBA vs. TOR, +105%) per bone surface in the tibia, and increase in osteoclast surface per bone surface (IBA vs. TOR, +128%) in the femur. The above evidence demonstrates that the musculoskeletal morphology of squirrels was largely preserved, and musculoskeletal metabolism was generally maintained after prolonged hibernation inactivity. These findings suggest that the well-maintained musculoskeletal metabolism may be a vital mechanism underlying the preservation of the musculoskeletal system during hibernation. The coincident up-regulation of several metabolic indicators during IBA indicates that musculoskeletal metabolism may be relatively active during this period; however, its role in musculoskeletal maintenance during hibernation needs further clarification.

The effects of microgravity on the digestive system and the new insights it brings to the life sciences

BACKGROUND

Weightlessness is a component of the complex space environment. It exerts adverse effects on the human body, and may pose unknown challenges to the implementation of space missions. The regular function of the digestive system is an important checkpoint for astronauts to conduct missions. Simulated microgravity can recreate the changes experienced by the human body in a weightless environment in space to a certain extent, providing technical support for the exploration of its mechanism and a practical method for other scientific research.

METHODS AND MATERIALS

In the present study, we reviewed and discussed the latest research on the effects of weightlessness or simulated microgravity on the digestive system, as well as the current challenges and future expectations for progress in medical science and further space exploration.

RESULTS

A series of studies have investigated the effects of weightlessness on the human digestive system. On one hand, weightlessness and the changing space environment may exert certain adverse effects on the human body. Studies based on cells or animals have demonstrated the complex effects on the human digestive system in response to weightlessness. On the other hand, a microgravity environment also facilitates the ideation of novel concepts for research in the domain of life science.

CONCLUSION

The effects of weightlessness on the digestive system are considerably complicated. The emergence of methods that help simulate a weightless environment provides a more convenient alternative for assessing the impact and the mechanism underlying the effect of weightlessness on the human body. In addition, the simulated microgravity environment facilitates the ideation of novel concepts for application in regenerative medicine and other fields of life science.

Muscle-Bone Crosstalk in the Masticatory System: From Biomechanical to Molecular Interactions

The masticatory system is a complex and highly organized group of structures, including craniofacial bones (maxillae and mandible), muscles, teeth, joints, and neurovascular elements. While the musculoskeletal structures of the head and neck are known to have a different embryonic origin, morphology, biomechanical demands, and biochemical characteristics than the trunk and limbs, their particular molecular basis and cell biology have been much less explored. In the last decade, the concept of muscle-bone crosstalk has emerged, comprising both the loads generated during muscle contraction and a biochemical component through soluble molecules. Bone cells embedded in the mineralized tissue respond to the biomechanical input by releasing molecular factors that impact the homeostasis of the attaching skeletal muscle. In the same way, muscle-derived factors act as soluble signals that modulate the remodeling process of the underlying bones. This concept of muscle-bone crosstalk at a molecular level is particularly interesting in the mandible, due to its tight anatomical relationship with one of the biggest and strongest masticatory muscles, the masseter. However, despite the close physical and physiological interaction of both tissues for proper functioning, this topic has been poorly addressed. Here we present one of the most detailed reviews of the literature to date regarding the biomechanical and biochemical interaction between muscles and bones of the masticatory system, both during development and in physiological or pathological remodeling processes. Evidence related to how masticatory function shapes the craniofacial bones is discussed, and a proposal presented that the masticatory muscles and craniofacial bones serve as secretory tissues. We furthermore discuss our current findings of myokines-release from masseter muscle in physiological conditions, during functional adaptation or pathology, and their putative role as bone-modulators in the craniofacial system. Finally, we address the physiological implications of the crosstalk between muscles and bones in the masticatory system, analyzing pathologies or clinical procedures in which the alteration of one of them affects the homeostasis of the other. Unveiling the mechanisms of muscle-bone crosstalk in the masticatory system opens broad possibilities for understanding and treating temporomandibular disorders, which severely impair the quality of life, with a high cost for diagnosis and management.

Progress in research of digestive system trauma and stress injury under microgravity environment

The last two decades have witnessed the rapid develop-ment of China's manned spaceflight industry. Studies have showed that the weightlessness environment has a series of adverse effects on the human body. Due to the complexity of the structure and function of the digestive system, the impact of weightlessness on the digestive system has certain particularity. How to ensure the steady state of the digestive system during astronaut's space mission and in the training under simulated weightlessness needs to be studied urgently. This review focuses on the progress in the research of digestive system trauma, stress injury, and repair under microgravity environment.

Insight into Pseudomonas aeruginosa pyocyanin production under low-shear modeled microgravity

Long-term space flight impairs the immune system of astronauts, rendering them vulnerable to opportunistic infections. Pseudomonas aeruginosa causes opportunistic infections, particularly in individuals with a compromised immune system; it can be a major health hazard for astronauts during space flight missions. Hence, the production of the most abundant redox active virulence factor, pyocyanin by P. aeruginosa, was assessed under low-shear modeled microgravity (LSMMG) conditions, simulated using a high aspect ratio vessel. Moreover, we evaluated changes in the expression of genes involved in pyocyanin biosynthesis and genes involved in the MexGHI-OpmD operon quorum sensing. Extracellular DNA and H₂O₂ production were measured, and their correlation with pyocyanin production was examined. Interestingly, the pyocyanin quantity was 2.58-fold lower in the LSMMG conditions compared to the normal gravity. LSMMG caused downregulation of the genes associated with pyocyanin biosynthesis. Interestingly, extracellular DNA and H₂O₂ release were significantly high in the normal gravity environment. Scanning electron microscopy revealed aggregation and elongated cells under LSMMG. Taken together, these findings suggest that LSMMG did not induce pyocyanin secretion in P. aeruginosa.

Investigation of simulated microgravity effects on Streptococcus mutans physiology and global gene expression

Astronauts have been previously shown to exhibit decreased salivary lysozyme and increased dental calculus and gingival inflammation in response to space flight, host factors that could contribute to oral diseases such as caries and periodontitis. However, the specific physiological response of caries-causing bacteria such as Streptococcus mutans to space flight and/or ground-based simulated microgravity has not been extensively investigated. In this study, high aspect ratio vessel S. mutans simulated microgravity and normal gravity cultures were assessed for changes in metabolite and transcriptome profiles, H₂O₂ resistance, and competence in sucrose-containing biofilm media. Stationary phase S. mutans simulated microgravity cultures displayed increased killing by H₂O₂ compared to normal gravity control cultures, but competence was not affected. RNA-seq analysis revealed that expression of 153 genes was up-regulated ≥2-fold and 94 genes down-regulated ≥2-fold during simulated microgravity high aspect ratio vessel growth. These included a number of genes located on extrachromosomal elements, as well as genes involved in carbohydrate metabolism, translation, and stress responses. Collectively, these results suggest that growth under microgravity analog conditions promotes changes in S. mutans gene expression and physiology that may translate to an altered cariogenic potential of this organism during space flight missions.

The gene expression patterns, metabolism and physiology of tooth cavities-causing microbes change in a space-like gravity environment. These findings could help explain why astronauts are at a greater risk for dental diseases when in space. Kelly Rice and colleagues from the University of Florida, Gainesville, USA, cultured Streptococcus mutans bacteria under simulated microgravity and normal gravity conditions. The bacteria grown in microgravity were more susceptible to killing with hydrogen peroxide, tended to aggregate in more compact cellular structures, showed changes in their metabolite profile and expressed around 250 genes at levels that were either much higher or lower than normal gravity control cultures. These genes included many involved in carbohydrate metabolism, protein production and stress responses. The observed changes collectively suggest that space flight and microgravity could alter the cavities-causing potential of S. mutans.

Wound healing and mucosal immunity during short Mars analog environment mission: salivary biomarkers and its clinical implications

OBJECTIVE

Wound healing in an extreme environment with micro-gravity is not well characterized, despite the likelihood that the increasing use of manned spaceflight as a research and commercial enterprise raises the probability of traumatic injury in this state. Hence, this study was conducted to determine the impact of the isolated environment of the Mars Desert Research Station on mucosal immunity and wound healing.

MATERIALS AND METHODS

Two punch biopsy wounds were placed on the hard palate of two crewmembers. The first wound was made during summer vacation, whereas the second was placed on the contra-lateral side 3 days before the Mars analog mission began. Thus, each crewmember served as his/her own control. Two independent methods were used to assess healing. A ten-item perceived stress scale, salivary cortisol, Immunoglobulin A, IgG and IgM were measured.

RESULTS

There were significant differences in the proportion of the wound size healed between vacation and the mission. Salivary IgA, IgM, IgG and cortisol levels showed significant differences between vacation and mission.

CONCLUSION

These data suggest that stress can have significant consequences for wound healing. The effects of stress on wound repair could have important clinical implications, including for recovery from surgery.

Apoptosis and calcification of vascular endothelial cell under hyperhomocysteinemia

In recent years, it is found that increase in Hcy level in blood can directly or indirectly cause vascular endothelial cell injury and induce vascular calcification. However, the mechanism of vascular endothelial cell injury and vascular calcification has not been studied thoroughly. This paper carried out experiment for research aiming at discussing the effect and action mechanism of Hhcy on endothelial cells and vascular calcification. Firstly, human umbilical vein endothelial cells (HUVECs) were cultured and then intervened by Hcy of different concentrations (0, 0.01, 0.1, 1.0, 3.0, 5.0 mmol/L) and at different action time (3, 6, 12, 24 h). Then apoptosis rate and reactive oxygen were detected by flow cytometry. At the same time, the model for the culture of rat vascular calcification was set up and induced into Hhcy so as to detect the total plasma Hcy level and judge vascular calcification degree. The results showed that with the increase in Hcy concentration and extension of action period, the apoptosis rate and generation of reactive oxygen of HUVECs all significantly increased, and the differences were all statistically significant (P < 0.01). In animal calcification model, mass of black particle deposition was seen after Von Kossa staining of rat vessels in calcification group. Compared with the control group, the vascular calcium content, alkaline phosphatase activity and osteocalcin content in calcification group all increased (P < 0.01). The content of plasma lipid conjugated olefine from highest to lowest wasas follows: calcification plus homoetheionin, homoetheionin, and calcification group. There was no significant difference between the calcification group and control group. All these findings suggested that Hcy could induce the apoptosis of endothelial cells and its effect degree depended on its concentration and action period; Hhcy could promote the calcification of blood vessels, and its mechanism might relate with the strengthening of lipid peroxidation. The above results leave great benefits on clinical prevention works.

Human Factor Studies on a Mars Analogue During Crew 100b International Lunar Exploration Working Group EuroMoonMars Crew: Proposed New Approaches for Future Human Space and Interplanetary Missions

Knowing the risks, costs, and complexities associated with human missions to Mars, analogue research can be a great (low-risk) tool for exploring the challenges associated with the preparation for living, operating, and undertaking research in interplanetary missions. Short-duration analogue studies, such as those being accomplished at the Mars Desert Research Station (MDRS), offer the chance to study mission operations and human factors in a simulated environment, and therefore contribute to exploration of the Moon and Mars in planned future missions. This article is based upon previously published articles, abstracts, and presentations by a series of independent authors, human factor studies performed on mars analogue station by Crew 100B. The MDRS Crew 100B performed studies over 15 days providing a unique insight into human factor issues in simulated short-duration Mars mission. In this study, 15 human factors were evaluated and analyzed by subjective and objective means, and from the summary of results it was concluded that optimum health of an individual and the crew as a whole is a necessity in order to encourage and maintain high performance and the satisfaction of project goals.

Evaluation by an aeronautic dentist on the adverse effects of a six-week period of microgravity on the oral cavity

Objective. HDT bed rest condition is a simulated microgravity condition in which subject lies on bed inclined −6 degree feet up. To determine the influence of a simulated microgravity (HDT bed rest) on oral cavity, 10 healthy male volunteers were studied before, during, just after, and after 6 weeks of the simulated microgravity condition of −6° head-down-tilt (HDT) bed rest. Materials and Methods. Facial nerve function, facial sensation, chemosensory system, salivary biomarkers were measured. Results. Lactate dehydrogenase, MIP 1 alpha, malonaldehyde, 8-hydroxydeoxyguanosine, and thiocyanate were found to increase significantly, while flow rate, sodium, potassium, calcium, phosphate, protein, amylase activity, vitamin E and C, and mouth opening were decreased in simulation environments in contradiction to normal. The threshold for monosodium glutamate (MSG) and capsaicin increased during microgravity as compared to normal conditions. Moderate pain of teeth, facial oedema, mild pain, loss of sensation of pain and temperature, decreased tongue, and mandibular movement in simulation microgravity environments were observed. Conclusions. These results suggest that reversible effect of microgravity is oedema of face, change in taste, abnormal expression of face, teeth pain, and xerostomia. Further study will be required on large scale on long-term effects of microgravity on oral cavity to prevent the adverse effects.

Histomorphometrical and molecular evaluation of endosseous dental implants sites in humans: correlation with clinical and radiographic aspects

OBJECTIVE

To evaluate the correlations between clinical-radiographical aspects and histomorphometric-molecular parameters of endosseous dental implant sites in humans.

MATERIAL AND METHODS

The study sample consisted of bone implant sites from the jawbones of 32 volunteers, which were classified according to two different systems: (1) based only on periapical and panoramic images (PP); (2) as proposed by Lekholm & Zarb (L&Z). Bone biopsies were removed using trephine during the first drilling for implant placement. Samples were stained with haematoxylin-eosin (HE), and histomorphometric analysis was performed to obtain the following parameters: trabecular thickness (Tb.Th), trabecular number, bone volume density (BV/TV), bone specific surface (BS/BV), bone surface density and trabecular separation (Tb.Sp). In addition, immunohistochemistry analysis was performed on bone tissue samples for the proteins, Receptor activator of nuclear factor kappa-B (RANK), RANK ligand (RANKL), osteoprotegerin (OPG) and Osteocalcin (OC). Also, the determination of the relative levels of gene expression was performed using Reverse transcription-real-time Polymerase Chain Reaction (RT-PCR).

RESULTS

PP and L&Z classification systems revealed a moderate correlation with BV/TV, BS/BV, Tb.Th and Tb.Sp. L&Z's system identified differences among bone types when BV/TV, BS/BV, Tb.Th and Tb.Sp were compared. A weak correlation between PP/L&Z classifications and the expression of bone metabolism regulators (RANK, RANKL, OPG e OC) was found. The analysis of mRNA expression showed no difference between the bone types evaluated.

CONCLUSIONS

Our results suggest that PP and L&Z subjective bone-type classification systems are related to histomorphometric aspects. These data may contribute to the validation of these classifications. Bone remodelling regulatory molecules do not seem to influence morphological aspects of the jawbone .

Effect of simulated weightlessness on the healing of experimental gastric ulcer in rats

AIM: To investigate the effect of simulated weightlessness on the healing of acetic acid-induced experimental gastric ulcer in rats and to explore the potential mechanisms involved.

METHODS: Thirty-two SD rats were randomly and equally divided into four groups: 7 d tail suspension group, 7 d control group,14 d tail suspension, and 14 d control group. Gastric ulcer was induced in rats with acetic acid. Tail suspension was used to simulate the weightlessness condition 3 days after ulcer induction. The gastric ulcer area was measured with a vernier caliper. The ultrastructure of regenerative mucosa was observed by electronic microscopy. Epidermal growth factor (EGF) level in gastric juice was determined by radioimmunoassay (RIA). The staging of ulcer healing was performed.

RESULTS: Compared to the 7 d control group, the ulcer area significantly increased (6.0 mm² ± 1.7 mm² vs 2.2 mm² ± 0.7 mm², t = 5.661, P < 0.01) and the stage of ulcer significantly decreased (χ² = 12.771, P < 0.01) in the 7d suspension group. Compared to the 14 d control group, the ulcer area and EGF level increased (3.0 mm² ± 1.2 mm² vs 1.1 mm² ± 0.4 mm², t = 4.233, P < 0.01; 0.155 ng/mL ± 0.052 ng/mL vs 0.103 ng/mL ± 0.019 ng/mL, t = 2.635, P < 0.05) in the 14 d suspension group. Compared to the 7 d suspension group, the ulcer area, EGF level and stage of ulcer significantly decreased (3.0 mm² ± 1.2 mm² vs 6.0 mm² ± 1.7 mm², t = 3.805, P < 0.01; 0.155 ng/mL ± 0.052 ng/mL vs 0.434 ng/mL ± 0.137 ng/mL, t = 5.657, P < 0.01; χ² = 12.953, P < 0.01) in the 14 d suspension group. The ultrastructural restoration and histological maturity of healed ulcer in the 7 d and 14 d suspension groups were inferior to those in the 7 d and 14 d control groups.

CONCLUSION: Simulated weightlessness may depress the structure of regenerative gastric mucosa, delay the healing of ulcer, and increase EGF level in gastric juice.

Effect of simulated microgravity on salivary and serum oxidants, antioxidants, and periodontal status

BACKGROUND

Microgravity is associated with an increase in peroxidative damage. The effect is more pronounced after long-duration space flights and can even last for several weeks after landing. The objective of the study is to determine the influence of simulated microgravity on the periodontal status and salivary and serum oxidant/antioxidant status of the body in simulated microgravity (-6° head-down-tilt [HDT) bed rest).

METHODS

Twenty healthy male volunteers were studied before and after 60 days of simulated microgravity (-6° HDT bed rest). We measured salivary and serum oxidative markers, such as malondialdehyde (MDA), 8-oxo-7,8 dihydro-2 deoxyguanosine (8-OHdG), and vitamins C and E, and clinical periodontal parameters (probing depth [PD] and clinical attachment level [CAL]).

RESULTS

Serum and salivary vitamin C and E concentrations were significantly decreased, whereas MDA and 8-OHdG levels were significantly increased after 60 days of simulated microgravity. Serum and salivary markers showed a strong and significant correlation. CAL and PD were higher but not statistically significant in simulated microgravity.

CONCLUSIONS

This study suggests that oxidative stress in the microgravity environment was increased but did not significantly influence periodontal parameters after 2 months. Also, this study indicates the possibility that the findings may have a broader clinical relevance to patients on bed rest or who are physically inactive. Studies on larger patient samples and follow-up for a longer time are required to verify the relationship between antioxidant status in the space microgravity condition and periodontal health.