|Year : 2018 | Volume
| Issue : 5 | Page : 327-333
Effect of Sudarshan Kriya Pranayama on periodontal status and human salivary beta-defensin-2: An interventional study
R Ananthalakshmi1, Jaideep Mahendra2, P Jayamathi3, Little Mahendra4, Nashra Kareem2, S Subramaniam5
1 Department of Oral Pathology and Microbiology, Thai Moogambigai Dental College and Hospital, Chennai, Tamil Nadu, India
2 Department of Periodontology, Meenakshi Ammal Dental College and Hospital, Chennai, Tamil Nadu, India
3 Department of Biochemistry, Meenakshi Ammal Dental College and Hospital, Chennai, Tamil Nadu, India
4 Department of Periodontology, Priyadharshini Dental College and Hospital, Tamil Nadu Dr. MGR University, Chennai, Tamil Nadu, India
5 Regenix Research Centre, Chennai, Tamil Nadu, India
|Date of Web Publication||4-Sep-2018|
Dr. Jaideep Mahendra
Department of Periodontology, Meenakshi Ammal Dental College and Hospital, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Background: Yogic stretching (asana) has been proven to have an effect on salivary human beta-defensin-2 (HBD-2) concentration, which is an antimicrobial peptide and is an inflammatory marker in periodontal disease. Sudarshan Kriya Pranayama (SKP) is a part of yoga which involves rhythmic breathing. Hence, we aim to evaluate the periodontal parameters and to estimate the salivary HBD-2 level before and after SKP program in periodontitis individuals.
Materials and Methods: An interventional study was designed and individuals were divided into three groups: Group I – healthy periodontium, Group II – chronic gingivitis, and Group III – chronic periodontitis. SKP was the interventional tool. The clinical parameters such as plaque index (PI), gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL), and salivary HBD-2 level were analyzed at baseline and 90 days after the SKP practice. Enzyme-linked immunosorbent assay (ELISA) was used to evaluate salivary HBD-2. McNemar's Chi-square, Paired samples t-test, and one-way ANOVA were used to analyze the results. P < 0.05 was considered statistically significant.
Results: Following the SKP intervention, the clinical parameters such as PI and GI improved significantly in all the groups (P < 0.001); however, Group III showed a significant reduction as compared to the other groups. The mean baseline salivary HBD-2 levels of Group I, Group II, and Group III were 91.78 ng/μl, 110.22 ng/μl, and 157.63 ng/μl which was further decreased to 95.22 ng/μl, 98.22 ng/μl, and 132.88 ng/μl, respectively, following SKP intervention (P < 0.001). However, Group III had a higher HBD-2 level at 90th day as compared to other groups.
Conclusion: There was an improvement in PI and GI with a decrease in salivary HBD-2 in chronic periodontitis patients following SKP. Hence, SKP can be considered as an adjunct to treatment modality in patients with periodontal disease.
Keywords: beta-defensins, Human, periodontal disease, yoga
|How to cite this article:|
Ananthalakshmi R, Mahendra J, Jayamathi P, Mahendra L, Kareem N, Subramaniam S. Effect of Sudarshan Kriya Pranayama on periodontal status and human salivary beta-defensin-2: An interventional study. Dent Res J 2018;15:327-33
|How to cite this URL:|
Ananthalakshmi R, Mahendra J, Jayamathi P, Mahendra L, Kareem N, Subramaniam S. Effect of Sudarshan Kriya Pranayama on periodontal status and human salivary beta-defensin-2: An interventional study. Dent Res J [serial online] 2018 [cited 2020 Feb 23];15:327-33. Available from: http://www.drjjournal.net/text.asp?2018/15/5/327/240479
| Introduction|| |
Periodontitis is a group of inflammatory diseases that affect the connective tissue attachment and supporting bone around the teeth. The etiology behind this pathology is multifaceted. Although bacteria play a key role in initiating the disease, the host immune response and environment factors are critical for disease progression. Furthermore, the current research discloses that periodontitis patients are at a high risk of systemic inflammation. Hence, management of oral disease is essential for the maintenance of systemic health.
The modern dentistry is sound enough and is coming out with emerging trends in early diagnosis and treatment of periodontitis. Nevertheless, integrative medicinal approach that combines the conventional medicinal practices and traditional medicines is gaining interest among population worldwide. One of the reasons could be that it is cost-effective and also emphasis on prevention of disease. Till date, few researches in the past have been attempted to evaluate the effect of complementary and alternative medicine (CAM) in the management of periodontitis.
Defensins are cationic peptides produced by epithelia at mucosal surfaces. The role of salivary human beta-defensin-2 (HBD-2) in various oral pathologies such as microbial infections, periodontal inflammation, and oral cancers are being scientifically documented.,, Therapeutic effect of synthetic forms of HBD-2 is stated in literature. After numerous research works on HBD-2 in periodontal health, it is considered that severity of periodontal inflammation could influence the salivary concentration of HBD-2.
Yoga is a time-tested mind–body medicine which originated from India 5000 years ago. This traditional medicine has been a nondrug treatment in preventing and curing various psychological and physiologic diseases involving various systems such as cardiovascular system, respiratory system, and central nervous system. Literature review shows the efficiency of SKP, a form of yoga in improving the quality of life in cancer patients. In addition, SKP has a beneficiary effect on the modifiable and nonmodifiable risk factors of periodontitis.,, To our knowledge, there is no work done so far in exploring the effect of SKP on periodontal health. Hence, we aim to assess the periodontal parameters such as plaque index (PI), gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL), and salivary HBD-2 in periodontitis patients at baseline and at 90th day following Sudarshan Kriya Pranayama (SKP) practice.
| Materials and Methods|| |
For this interventional study, one hundred and ten males of age between 18 and 35 years with the presence of at least 24 teeth were recruited for the study from the Art of Living Centers in Chennai, Tamil Nadu, India. Of 110 individuals, 10 refused to participate in the study, two 2 were diabetic, 1 was hypertensive, 4 were smokers, 2 underwent periodontal therapy in the last 6 months, and 1 individual was currently under antibiotics and hence twenty males were excluded from the study. Females were also excluded from the study since their periodontal health maybe influenced by hormones. Finally, inclusion criteria included 90 males who were systemically healthy. They were also screened for periodontal disease and divided into three groups: Group I – 30 individuals (volunteers) who were systemically and periodontally healthy, Group II – 30 individuals with chronic gingivitis, and Group III – 30 individuals with chronic periodontitis. Patients who showed the GI index score of 2 and 3 were considered as gingivitis patients. Patients with >30% of sites showing >5 mm of PPD or 3–4 mm of CAL were considered as chronic periodontitis patients. The study was approved by the Institutional Ethics Committee and Institutional Review Board, MAHER University, Chennai (MAHER-MU-002-IEC/2016), following the Declaration of Helsinki. All individuals were explained about the study, and written informed consent was obtained.
Clinical data collection
All individuals were seated comfortably in an upright position and underwent a full-mouth periodontal examination. The periodontal examination included PI, GI, PPD, and CAL. PI (Silness and Loe 1964) was recorded at 4 sites (mesiobuccal, midbuccal, distobuccal, and midpalatal sites) around each tooth: 0 = no plaque, 1 = a film of plaque, 2 = moderate accumulation of deposit, and 3 = abundance of soft matter. GI (Silness and Loe 1963) was recorded at (facial, mesial, distal, and lingual) four gingival areas: 0 = no inflammation, 1 = mild inflammation, 2 = moderate inflammation, and 3 = severe inflammation (0.1–1 = mild gingivitis, 1.1–2 = moderate gingivitis, and 2.1–3 = severe gingivitis). PPD and CAL were recorded at six sites of each tooth and measured in millimeters. PPD was measured from gingival margin to the base of periodontal pocket, and CAL was measured as the distance from the cementoenamel junction to the base of the periodontal pocket.
The participants were requested to take only water 2 h before pranayama session. 5 ml of unstimulated saliva was collected at baseline before SKP session and at 90th day. Saliva was processed for HBD-2 by enzyme-linked immunosorbent assay kit (Qayee bio-technology Cat. No. 100–250-BD2).
SKP was used as the intervention tool. Pranayama was taught and monitored by a certified yoga teacher for 90 days. SKP is a unique yogic breathing, with several types of cyclical breathing pattern ranging from slow and calming to rapid and stimulating breath. The 4 stages of SKY are as follows: (1) ujjayi/victorious breath – 2–4 breaths/min, (2) bhastrika/bellows breath – 30 breaths/min, (3) Om chanting – three times, and (4) Sudarshan Kriya – normal breathing with slow, medium, and fast cycles followed by rest.
Statistical analysis was performed using SPSS software version 16 (IBM Corporation, Chicago IL USA). McNemar's Chi-square test was used to compare the clinical parameters at baseline and 90th day in all the groups following SKP. Paired samples t-test was used to compare the pre- and postintervention mean values of salivary HBD-2. One-way ANOVA was used to compare the mean salivary HBD-2 values between groups at 90th day. P <0.05 was considered statistically significant.
| Results|| |
On comparing the effect of SKP on PI from baseline to 90th day within the groups, 88.9% of Group I individuals were improved in PI score from score 1 to score 0. Similarly, 77.8% individuals in Group II had improved in PI score from score 3 and 2 to score 1 and 0, respectively, after intervention. In Group III, 87.5% individuals improved in PI score from score 3 to score 2 and 1 (P < 0.001) [Table 1].
|Table 1: Group wise comparison of plaque index before and after Sudarshan Kriya Pranayama|
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On comparing the GI score from baseline to 90th day in Group II and Group III, 88.8% of Group II individuals showed improvement in GI score from score 3 and 2 to score 1 and 0, respectively. Similarly, GI in the Group III individuals had a significant change from score 3 to score 2 and 1 (P < 0.001). Group I individuals had the same GI score 0 before and at 90th day following SKP [Table 2].
|Table 2: Group wise comparison of gingival index before and after Sudarshan Kriya Pranayama|
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When the clinical parameters such as PPD and CAL were compared from baseline to 90th day following SKP, Group III had no significant changes stating that there was no improvement in PPD and CAL (P < 0.001) [Table 3] and [Table 4].
|Table 3: Comparison of probing pocket depth before and after Sudarshan Kriya Pranayama in Group III|
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|Table 4: Comparison of clinical attachment level before and after Sudarshan Kriya Pranayama in Group III|
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The mean salivary HBD-2 levels in Group I, Group II, and Group III were found to be 91.78 ng/μl, 110.22 ng/μl, and 157.63 ng/μl which decreased to 95.22 ng/μl, 98.22 ng/μl, and 132.88 ng/μl, respectively, following SKP. HBD-2 level when compared at 90th day among three groups was statistically significant (P < 0.001) [Table 5].
|Table 5: Group wise comparison of salivary human beta-defensin-2 level before and after Sudarshan Kriya Pranayama|
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Group III had a higher HBD-2 level when compared to Group II and Group I. Although the HBD-2 levels were reduced following SKP in all three groups, Group III showed higher level at 90th day as compared to other groups [Table 6].
| Discussion|| |
Periodontal disease is the most common chronic bacterial infection of the supporting structures of the teeth which are predominantly associated with Gram-negative microorganisms that exist in subgingival biofilm. To identify individuals with periodontitis, new diagnostic tools have been developed. However, saliva is one of the most common tools to identify the various markers of periodontal inflammation. HBD-2 is one such marker which shows high sensitivity and specificity in saliva. Salivary HBD-2, an inflammatory marker of periodontal disease, is inducible in response to physical exercise.
One of the treatment modalities for periodontal disease is scaling and root planing followed by complex surgical procedures. The use of CAM and practices, such as pranayama and yoga, can further reduce the risk of periodontitis and improve the immune system. SKP is one novel type of yoga that influences the mind–body system, by extending its positive effects on humoral factors, nervous system, and immune system. Unlike medicines, pranayama strengthens the healing ability of an individual from inside. In addition, yoga is also an anti-inflammatory tool. Low-intensity yogasana has also been proven to affect salivary HBD-2 with salivary flow rate which is essential for oral hygiene. Various studies in the past have evaluated HBD-2 level in periodontal disease. However, to the best of our knowledge, this is the first study to evaluate the level of HBD-2 in individuals with periodontal disease following SKP intervention. Hence, we aimed to assess the clinical parameters such as PI, GI, PPD, CAL, and salivary HBD-2 level in individuals with gingivitis and periodontitis, compared with healthy controls with SKP as intervention.
In our study, 88.9% of Group 1, 77.8% Group II, and 87.5% of Group III individuals showed improvement in PI score from poor to better. This is in accordance with Farsi et al. who compared saliva and periodontal health and stated that plaque score is directly proportional to the severity of periodontal disease. The statistically significant improvement of PI in our study could be attributed to the fact that there would have been an increase in salivary flow rate following SKP intervention. In healthy gingiva where there is no periodontal disease, there is an increase in saliva flow rate, thereby preventing the accumulation of plaque. Hence, our observation is also in accordance with previous work done by Eda et al. where there was an increase in the salivary flow rate following yogic stretching (asana). This observation is irrespective of the patients oral hygiene and food habits. Although food and brushing habit is said to have an impact on plaque deposition, physical and chemical properties of saliva play an incredible role. Hence, it is suggested that SKP can improve the salivary flow, which in turn can decrease plaque deposition and enhance oral hygiene.
Group II individuals had a significant decrease in gingival inflammation. 88.8% of individuals of Group II were recovered from severe and moderate gingivitis to mild gingivitis after SKP intervention, which was statistically significant. Similarly, individuals in Group III had 100% improvement from moderate and severe gingivitis to mild and moderate gingivitis, respectively. When PPD and CAL were measured in Group II and Group III individuals, from baseline to 90th day, no change was seen in their scores. The increases in pocket depth and clinical attachment loss are the burden of past gingival inflammation that remains irreversible unless intervened surgically. The normal depth of gingival sulcus is 0–3 mm and worsens when PPD progresses. In our study, the PPD and clinical attachment loss in Group III individuals did not show any clinically significant difference. There was neither improvement nor worsening. To our knowledge, there are no similar studies to compare the results. Nevertheless, it is shown that the practice of SKP increases antioxidant defense and cytotoxic function of natural killer cells and inhibits apoptosis., It is suggested that this cumulative effect of SKP would have modulated the immune response, thereby reducing the inflammation and further preventing the disease progression.
In our study, the salivary HBD-2 level decreased significantly from baseline to 90th day following SKP in all the three groups. This finding is in concurrence with Ebrahem who also documented decreased level of gingival crevicular fluid-HBD-2 in the periodontitis patients with nonsurgical periodontal therapy, indicating the downregulation of inflammation. In our study, SKP was used as an intervention. SKP directly influences the autonomic nervous system, stimulates vagus nerve, and energizes the endocrine and immune system which in turn balances inflammatory response. It is likely that the SKP practice would have shown a direct impact on immune mechanism in all individuals.
In our study, the salivary HBD-2 level was higher in Group III than Group II and Group I at 90th day practice of SKP. Based on this observation, it can be suggested that salivary HBD-2 level increases with inflammation. This observation is in accordance with the work of Pereira et al. and Aas et al. who also found that HBD-2 levels were similar in healthy and gingivitis individuals but higher in periodontitis. Kuula et al. in their study found an increased level of HBD-2 in inflamed periodontal individuals, suggesting that the response was due to increased bacterial burden in periodontitis patients than healthy controls. Similarly, Hosokawa et al. recorded higher HBD-2 concentration in chronic periodontitis group followed by gingivitis patients and healthy controls. Studies on chronic periodontitis and periopathogens such as Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Fusobacterium nucleatum suggest that bacteria can induce the upregulation of HBD-2. This observation abides with our study, suggesting that Group III individuals have deeper periodontal pockets with more bacterial colonization and hence have higher levels of salivary HBD-2.
Davison et al. and Usui et al. worked on the effect of strenuous physical exercise and sports activity on salivary antimicrobial peptides and recorded increased levels of cathelicidin, human alpha-defensin, and cortisol with a decrease in salivary flow and IgA level., Yogic practice is considered superior to traditional exercise for the fact that results obtained after high-intensity workouts are quantitative at the muscular level when compared with qualitative output of yoga practice. The oxygen and nutrition consumption is at the organ level in yoga practice which energizes the chakras (energy centers) of the body.
Yoga plays a positive effect on periodontitis by decreasing the stress level. It is known that stress can influence factors such as endocrine system. It has also shown an impact on poor oral hygiene, dietary intake, smoking, change in salivary flow, and components, thereby decreasing the risk for periodontal disease. Yoga has proven to have a beneficial effect on stress by decreasing the cortisol level, a stress marker. Yoga stimulates phagocytosis and regulates the formation of fibroblasts and epithelial cells, thereby enhancing the periodontal health.
The limitation of the study was that salivary HBD-2 was only quantitatively analyzed. The mechanism and role of HBD-2 in periodontal disease is yet to be explored. This study provides a base for the CAM, mainly SKP and yoga in dentistry. Further, extensive evidence-based research should be performed with larger sample size and long-term follow-up to power the current study. Research in combination with the mainstream periotherapy must be performed to highlight the complementary and alternative effect of SKP on periodontal diseases.
| Conclusion|| |
SKP effectively decreased the periodontal inflammation in periodontitis individuals. This study paves a way for future research in the field of pranayama against various oral pathogenic bacteria.
We acknowledge our statistician Mr. Boopathy, Indian Council of Medical Research and the Art of Living Foundation, Chennai. India.
Financial support and sponsorship
Conflicts of interest
The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or non-financial in this article.
| References|| |
Taba M Jr., Kinney J, Kim AS, Giannobile WV. Diagnostic biomarkers for oral and periodontal diseases. Dent Clin North Am 2005;49:551-71, vi.
Kochupillai V, Kumar P, Singh D, Aggarwal D, Bhardwaj N, Bhutani M, et al.
Effect of rhythmic breathing (Sudarshan Kriya and Pranayam) on immune functions and tobacco addiction. Ann N
Y Acad Sci 2005;1056:242-52.
Jurczak A, Kościelniak D, Papież M, Vyhouskaya P, Krzyściak W. A study on β-defensin-2 and histatin-5 as a diagnostic marker of early childhood caries progression. Biol Res 2015;48:61.
Li X, Duan D, Yang J, Wang P, Han B, Zhao L, et al.
The expression of human β-defensins (hBD-1, hBD-2, hBD-3, hBD-4) in gingival epithelia. Arch Oral Biol 2016;66:15-21.
Meyer JE, Harder J, Görögh T, Weise JB, Schubert S, Janssen D, et al.
Human beta-defensin-2 in oral cancer with opportunistic Candida infection. Anticancer Res 2004;24:1025-30.
Gordon YJ, Romanowski EG, McDermott AM. A review of antimicrobial peptides and their therapeutic potential as anti-infective drugs. Curr Eye Res 2005;30:505-15.
Tabish SA. Complementary and alternative healthcare: Is it evidence-based? Int J Health Sci (Qassim) 2008;2:5-9.
Côté A, Daneault S. Effect of yoga on patients with cancer: Our current understanding. Can Fam Physician 2012;58:e475-9.
Dhananjai S, Sadashiv J, Tiwari S, Dutt K, Kumar R. Reducing psychological distress and obesity through yoga practice. Int J Yoga 2013;6:66-70.
] [Full text]
Bock BC, Fava JL, Gaskins R, Morrow KM, Williams DM, Jennings E, et al.
Yoga as a complementary treatment for smoking cessation in women. J Womens Health (Larchmt) 2012;21:240-8.
Vaze N, Joshi S. Yoga and menopausal transition. J Midlife Health 2010;1:56-8.
Suchdeva S, Gupta R. Evaluation of commercially available biodegradable tetracycline fibrous therapy in chronic periodontitis. Indian J Dent Sci 2009;1:12-7.
Silness J, Loe H. Periodontal disease in pregnancy. II. Correlation between oral hygiene and periodontal condtion. Acta Odontol Scand 1964;22:121-35.
Ainamo J, Bay I. Problems and proposals for recording gingivitis and plaque. Int Dent J 1975;25:229-35.
Balasubramanian S, Janech MG, Warren GW. Alterations in salivary proteome following single twenty-minute session of yogic breathing. Evid Based Complement Alternat Med 2015;2015:376029.
Zope SA, Zope RA. Sudarshan kriya yoga: Breathing for health. Int J Yoga 2013;6:4-10.
] [Full text]
Usui T, Yoshikawa T, Orita K, Ueda SY, Katsura Y, Fujimoto S, et al.
Changes in salivary antimicrobial peptides, immunoglobulin A and cortisol after prolonged strenuous exercise. Eur J Appl Physiol 2011;111:2005-14.
Vijayaraghava A, Doreswamy V, Narasipur OS, Kunnavil R, Srinivasamurthy N. Effect of yoga practice on levels of inflammatory markers after moderate and strenuous exercise. J Clin Diagn Res 2015;9:CC08-12.
Eda N, Shimizu K, Suzuki S, Tanabe Y, Lee E, Akama T, et al.
Effects of yoga exercise on salivary beta-defensin 2. Eur J Appl Physiol 2013;113:2621-7.
Farsi N, Al Amoudi N, Farsi J, Bokhary S, Sonbul H. Periodontal health and its relationship with salivary factors among different age groups in a Saudi population. Oral Health Prev Dent 2008;6:147-54.
Suresh S, Mahendra J, Sudhakar U, Pradeep AR, Singh G. Evaluation of plasma reactive oxygen metabolites levels in obese subjects with periodontal disease. Indian J Dent Res 2016;27:155-9.
] [Full text]
Agte VV. Sudarshan Kriya Yoga for improving antioxidant status and reducing anxiety in adults. Altern Complement Ther 2008;14:96-100.
Qu S, Olafsrud SM, Meza-Zepeda LA, Saatcioglu F. Rapid gene expression changes in peripheral blood lymphocytes upon practice of a comprehensive yoga program. PLoS One 2013;8:e61910.
Ebrahem MA. Expression of human beta defensins (HBDs) 1, 2 and 3 in gingival crevicular fluid of patients affected by localized aggressive periodontitis. Saudi Dent J 2013;25:75-82.
Pan NL, Liao CF, Jiang MJ, HP Lu, Wang CL, Huang AM. Proceedings World Conference Expanding Paradigms: Science, Consciousness and Spirituality. New Delhi, India: All India Institute of Medical Sciences. Serum levels of brain derived neurotrophic factor before and after the practice of Sudarshan Kriya; 2006. p. 156-60.
Pereira AL, Franco GC, Cortelli SC, Aquino DR, Costa FO, Raslan SA, et al.
Influence of periodontal status and periodontopathogens on levels of oral human β-defensin-2 in saliva. J Periodontol 2013;84:1445-53.
Aas JA, Paster BJ, Stokes LN, Olsen I, Dewhirst FE. Defining the normal bacterial flora of the oral cavity. J Clin Microbiol 2005;43:5721-32.
Kuula H, Salo T, Pirilä E, Hagström J, Luomanen M, Gutierrez-Fernandez A, et al.
Human beta-defensin-1 and -2 and matrix metalloproteinase-25 and -26 expression in chronic and aggressive periodontitis and in peri-implantitis. Arch Oral Biol 2008;53:175-86.
Hosokawa I, Hosokawa Y, Komatsuzawa H, Goncalves RB, Karimbux N, Napimoga MH, et al.
Innate immune peptide LL-37 displays distinct expression pattern from beta-defensins in inflamed gingival tissue. Clin Exp Immunol 2006;146:218-25.
Vankeerberghen A, Nuytten H, Dierickx K, Quirynen M, Cassiman JJ, Cuppens H, et al.
Differential induction of human beta-defensin expression by periodontal commensals and pathogens in periodontal pocket epithelial cells. J Periodontol 2005;76:1293-303.
Davison G, Allgrove J, Gleeson M. Salivary antimicrobial peptides (LL-37 and alpha-defensins HNP1-3), antimicrobial and IgA responses to prolonged exercise. Eur J Appl Physiol 2009;106:277-84.
Govindaraj R, Karmani S, Varambally S, Gangadhar BN. Yoga and physical exercise – A review and comparison. Int Rev Psychiatry 2016;28:242-53.
Peruzzo DC, Benatti BB, Ambrosano GM, Nogueira-Filho GR, Sallum EA, Casati MZ, et al.
A systematic review of stress and psychological factors as possible risk factors for periodontal disease. J Periodontol 2007;78:1491-504.
McCall T. Yoga as Medicine. New York: Bantam Dell a division of Random House Inc.; 2007.
Rozlog LA, Kiecolt-Glaser JK, Marucha PT, Sheridan JF, Glaser R. Stress and immunity: Implications for viral disease and wound healing. J Periodontol 1999;70:786-92.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]