|Year : 2021 | Volume
| Issue : 5 | Page : 432-437
Effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students
Diego Dantas Lopes dos Santos1, João Felipe Besegato2, Sâmmea Martins Vieira1, Andrea Abi Rached Dantas2, Aryvelto Miranda Silva2, Alexandre Monteiro da Silva1
1 Department of Dentistry, Faculdade Integral Diferencial – FACID/Wyden, Teresina, PI, Brazil
2 Department of Restorative Dentistry, School of Dentistry, Araraquara, São Paulo State University – UNESP, Araraquara, SP, Brazil
|Date of Submission||06-May-2020|
|Date of Decision||11-Oct-2020|
|Date of Acceptance||12-Dec-2020|
|Date of Web Publication||01-Sep-2021|
Aryvelto Miranda Silva
Department of Restorative Dentistry, São Paulo State University (UNESP), School of Dentistry, Araraquara, Rua Humaitá, 1680 – Centro, Araraquara 14801-903, São Paulo
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: The effects of fixed orthodontic therapy on the occurrence of halitosis are not yet fully understood. This study aimed to evaluate the effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students. Materials and Methods: Sixty-two undergraduate dental students were included in this cross-sectional study. Two groups (n = 31 per group) were composed of participants with (study group) or without (control group) fixed orthodontic appliance. Halitosis self-assessment and clinical diagnosis were assessed using a visual analogic scale (VAS) and sulfur volatile compounds (SVCs) assessment, respectively. The subjective (VAS) and objective (SVC) malodor assessments were classified in absence, light, moderate, or severe malodor. Chi-square Pearson test and Spearman's correlation were applied for data analysis, with a significance level of 5%. Results: The use of fixed orthodontic appliances had no effect on self-assessment (P = 0.490) or clinical diagnosis (P = 0.610) of halitosis. Self-assessment was not significantly associated with the diagnosis of halitosis regardless the use of fixed orthodontic appliance (P ≥ 0.737). Male participants showed higher diagnosis of halitosis (P = 0.007). SVC measurements showed the absence of halitosis in 51.6% and 58.1% of participants with or without orthodontic appliances, respectively. Conclusion: The use of fixed orthodontic appliances affected the self-assessment of halitosis but no SVC measurements. It was not verified a correlation between subjective and objective methods to diagnose halitosis in dental students.
Keywords: Dental students, diagnosis, halitosis, orthodontic appliances, self-assessment
|How to cite this article:|
Santos DD, Besegato JF, Vieira SM, Rached Dantas AA, Silva AM, da Silva AM. Effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students. J Indian Soc Periodontol 2021;25:432-7
|How to cite this URL:|
Santos DD, Besegato JF, Vieira SM, Rached Dantas AA, Silva AM, da Silva AM. Effect of fixed orthodontic appliances on self-assessment and diagnosis of halitosis in undergraduate dental students. J Indian Soc Periodontol [serial online] 2021 [cited 2021 Sep 19];25:432-7. Available from: https://www.jisponline.com/text.asp?2021/25/5/432/324995
| Introduction|| |
Halitosis is an unpleasant change in the odor of the oral cavity which is originated from oral and nonoral sources., This alteration interferes with the quality of life and interpersonal relationships and can lead to social withdrawal., Moreover, halitosis is a clinical sign that some disorder is occurring and needs to be properly treated., In this way, dental clinicians are the first-line professionals who must be able to identify this alteration., Therefore, halitosis must be a concern during anamnesis and clinical examination since its complication and high prevalence (around 30%).,,
Some clinical conditions can facilitate halitosis onset. Although halitosis may have a multifactorial source, orthodontic brackets can play an important role in oral malodor appearance, in patients under fixed orthodontic therapy., The placement of orthodontic devices leads to plaque accumulation and hinder access to good oral hygiene practices., Thus, one of the major clinical challenges during orthodontic treatment is to improve the periodontal tissue condition and manage plaque accumulation and halitosis of the patients.
There are three main methods for diagnosis of halitosis: self-assessment, organoleptic assessment, and sulfur volatile compound (SVC) level measurement. While the organoleptic and SVC measurements are objective methods and demand a trained operator and appropriate device, the self-assessment is time saving and cost-effective.,
It is important to note that patients' self-assessment of oral malodor is a complex issue that involves cognitive, emotional, and physiological factors., Taking that into account, most patients complaining of oral malodor may not exhibit a clinical diagnosis of halitosis., Besides, these patients tend to overestimate their oral malodor compared with an odor judgment from others.,,
The self-assessment of halitosis is limited since it is an evaluation only based on the perception of the individual. However, it is still clinically relevant since takes into account any malodor that exerts a negative effect on the quality of life. Previous studies have shown divergent findings regarding self-assessment of halitosis in dental students and the factors related to halitosis, as well as their impact on the quality of life., However, the role of the higher knowledge and concern about oral conditions by dental students than the general population on self-assessment of halitosis was not fully investigated.
Pseudo-halitosis can be observed in many cases since halitosis is a complex disease affected by psychosomatic factors, such as those situations where the individuals are exposed to risk factors of halitosis. The fixed orthodontic appliance provides an increased number of subgingival periodontitis-related pathogens. Moreover, patients with periodontitis are more susceptible to have halitosis (three times higher odds).
Thus, this study aimed to evaluate whether the self-assessment is clinically confirmed among dental students under fixed orthodontic treatment. The null hypotheses tested were that fixed orthodontic appliances do not affect (1) the self-assessment of halitosis; (2) the diagnosis of halitosis by SVC measurements; and (3) there is no correlation between self-assessment and clinical confirmation of halitosis in dental students.
| Materials and Methods|| |
This study followed the ethical recommendations of the Declaration of Helsinki. It was submitted and approved by an institutional review board. The participants previously agree to participate and signed a free and informed consent form. Furthermore, the article was written according to the recommendations of the Strengthening the Reporting of Observational Studies in Epidemiology.
Study design and sample
A comparative cross-sectional study was carried out in a higher educational institution in Teresina, Piauí, Brazil. For the sample size calculation, malodor prevalence of 65% and 30% in the patients with and without orthodontic appliance were, respectively, considered.,, Significance level at 5% and test power of 80% were used. After calculation, 62 participants were necessary for the study.
A nonprobabilistic sample was obtained among all undergraduate dental students enrolled in the institution. For the study group (SG), eligibility criteria for the participants included the following: under orthodontic treatment for 6 months or more; at age 18 or older. The exclusion criteria were participants using systemic antimicrobial medications; smokers; with fixed and/or removable prostheses; undergone dental and/or oral surgery in the last 6 months; and absence of periodontal disease, which was confirmed by clinical examination. For the control group (CG), participants without orthodontic treatment and that never had submitted to orthodontic therapy before were considered eligible.
To prevent that odor by dietary and cosmetic sources that influence the halitosis self-assessment, the participants were instructed to refrain the use of scented personal products and tooth brushing on the morning of the appointment. They were also instructed to do not to eat spicy foods or onion/garlic-contained foods 48 h before the appointment. Refrain from eating at least 8 h and from drinking 3 h before the evaluation was requested. In addition, they avoided the use of chewing gum and oral rinsing at least 12 h before the appointment.
The self-assessment of halitosis was carried out as previously described by Rosenberg et al. The participants were asked to smell the odor emanating from their mouth by cupping their hands over mouth and nose, exhaling through the mouth, and breathing in through the nose. After that, the odor self-assessment was recorded by the participant using a visual analogic scale (VAS). After to smell the odor, each participant marked the value corresponding to their self-assessment of the odor on a scale from 0 (no bad breath) to 10 (strong bad breath).
The odor self-assessment was classified in levels, corresponding to the points observed in the VAS. Thus, for point 0, the absence of odor was considered. Points between 1–3, 4–7, and 8–10 were considered as slight, moderate, and severe odor, respectively.
Sulfur volatile compounds assessment
For the diagnosis of halitosis, the SVCs and hydrocarbon gases from participants were detected using a portable device (Breath Checker Model HC-212SF, Tanita Corp, Inc, Japan), which is commonly used for objective diagnosis of halitosis,, by semiconductor measurement technology. In this device, sulfur gases and hydrocarbons present in the breath are detected for a small electrical current through the sensor in a fast, simple, and reliable way.
For the SVC assessment, the participants were instructed to remain with their mouth closed, performing only nasal breathing for 3 min before the measurement. The diagnosis was performed bringing the sensor closer to participants' open mouth for 5 s. At the end of this time, the measurement was recorded and observed on the display. For each participant, the measurement was performed three consecutive times with no time interval. The highest obtained value was registered.
According to the manufacturer, the device classifies the odor in levels from 0 to 5. In this study, the odor was classified as the following: absence of odor (level 0); slight odor (levels 1 and 2); moderate odor (level 3); and severe odor (levels 4 and 5).
Data analysis was carried out using the Statistical Package for the Social Sciences (SPSS® for Windows® version 22.0 Inc., IL, Chicago, USA), with a significance level of 5%. A descriptive analysis of data was presented as frequency and percentage. Chi-square Pearson test was used to associate self-assessment and diagnosis of halitosis with independent variables (fixed orthodontic appliance use, sex, and age group) and to compare the levels of self-assessment and diagnosis of halitosis between the groups. Spearman's correlation was applied to associate self-assessment and diagnosis.
| Results|| |
Data of 62 participants with (SG) or without (CG) fixed orthodontic appliances were obtained (n = 31/group). Most of the participants were female and the groups were paired by sex. The greater proportion of participants was in the 22–24 age group, with an average of 23.1 (±3.3) years old [Table 1].
[Table 2] shows the association between self-assessment and clinical diagnosis of halitosis with independent variables. Although with a similar frequency (n = 14) for both sexes, a greater proportion of male participants (70%) exhibited a clinical diagnosis of halitosis (P = 0.007). The use of fixed orthodontic appliance (P ≥ 0.490) or age group (P ≥ 0.176) was not associated with the presence of halitosis, either by self-assessment or by clinical diagnosis.
|Table 2: Association between independent variables with self-assessment and clinical diagnosis of halitosis in undergraduate dental students|
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Most undergraduate dental students reported malodor. However, the use of fixed orthodontic appliance exhibited no effect on the levels of odor classification by self-assessment (P = 0.606). Similarly, the clinical diagnosis was not associated with the orthodontic appliance (P = 0.521). The absence of halitosis was clinically diagnosed for 51.6% and 58.1% of the participants with and without orthodontic appliances, respectively [Table 3].
|Table 3: Level analysis of self-assessment and diagnosis of halitosis in undergraduate dental students with or without fixed orthodontic appliance|
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Spearman's correlation coefficients showed that self-assessment was not significantly associated with the halitosis diagnosis. This was seen in participants with (r = 0.016, P = 0.933) and without (r = 0.063, P = 0.737) fixed orthodontic appliance [Figure 1].
|Figure 1: Correlation between self-assessment and clinical diagnosis of halitosis among undergraduate dental students with fixed orthodontic appliance. *SVC - Sulfur volatile compounds|
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| Discussion|| |
This study evaluated the effect of fixed orthodontic treatment on self-assessment and clinical diagnosis of halitosis in undergraduate dental students. The participants exhibited high self-reported halitosis and low clinical confirmation. Besides, self-assessment and halitosis diagnosis were not associated with the use of fixed orthodontic appliances, and the correlation between self-assessment and clinical diagnosis was not confirmed. Thus, only the first null hypothesis was rejected.
Self-assessment of halitosis is a psychophysiological response with a multifactorial etiology and associated with the psychopathological profile of each individual. In this study, a high rate of self-reported malodor was observed among undergraduate dental students (83.3% for females and 85% for males). This perception did not differ between sexes, age groups, or the use of fixed orthodontic appliances. These results suggest that dental students are possibly more sensitive to their oral odors and tend to even classify physiological odors as halitosis. Besides, the prevalence of self-reported malodor was higher than a previous study with dental students. The differences in rates of malodor perception may be possibly associated with the method adopted. In the present study, a VAS was used, while in the study by Ashwath et al., the perception data were obtained through a questionnaire.
Our results suggest that the use of a fixed orthodontic appliance does not interfere with self-perception and clinical diagnosis of halitosis among undergraduate dental students. This finding can be explained because dental hygiene guidance is often provided to individuals undergoing orthodontic treatment since they present a higher number of visits to dental offices than those who are not under orthodontic therapy. Besides, theoretically, before patients are submitted to the placement of orthodontic devices, they should be aware of the risks of this treatment, which involves halitosis. Thus, it can be inferred that these patients appear to be more cautious concerning halitosis. Moreover, the majority of people seeking orthodontic treatment are looking for increasing the esthetics of their teeth, which may show a patient profile concerned with oral hygiene practices. In addition, our results were obtained from a sample of dental students, who have great knowledge and work directly in oral health promotion and hygiene measures guidelines, which can lead them to have a greater awareness of their oral health.
In this study, a higher occurrence of halitosis was observed in male participants. This result agrees with other reports among dental students, and can be justified by the fact that female students show more suitable oral hygiene practices. Although oral health conditions and oral hygiene practices were not evaluated in this study, Almas et al. claimed that the lower self-assessment of oral malodor among females was associated with better oral hygiene practices, less self-reported malodor, and smoking habits than males. Similar results were observed by Setia et al. where the lower prevalence of halitosis in female students was also justified by the best oral hygiene practices concerning their male peers.
The data observed for self-assessment were not clinically confirmed. Although the majority of participants self-reported halitosis, the clinical diagnosis confirmed the absence of halitosis in 51.6% and 58.1% of participants with and without orthodontic appliances, respectively. Besides, the occurrence of halitosis also did not differ between age groups and there was no correlation between self-perception and clinical diagnosis, regardless of the use or not of fixed orthodontic appliance. These results are similar to other studies in the literature., Individuals exposed for long periods to some odor can adapt to it and become desensitized, which may explain why there is no correlation between subjective and objective assessment of halitosis. Patients may not notice their oral odor after being desensitized by an adaptation process. Besides, our study included dental students, who have more information about dental diseases and changes concerning the general population. This profile may justify that the participants overestimated the presence of oral malodor.
Although with a smaller proportion, a significant rate of participants with halitosis was observed. Humagain et al. observed in a study among undergraduate students in different areas that most of the individuals (43.8%) reported that halitosis negatively impacted their social relationships. Moreover, oral hygiene instructions provided by professionals appear to positively affect the oral health-related quality of life in individuals with halitosis. Thus, our findings point out the need for adopting oral hygiene measures and oral health promotion guidelines to the perception and occurrence of halitosis, regardless of other associated covariables.
The etiology of halitosis is multifactorial and remains unclear., Recent studies have claimed the association of halitosis occurrence with high levels of anxiety and stress., The theory so-called microbial endocrinology states that the microorganisms responsible for malodor can interact with substances related to stress and/or anxiety and change their metabolism, virulence, and growth profile., It is known that dental students may have a high level of anxiety due to the phase of life they are going through, the workload of classes and disciplines, and the responsibility for starting to deal with patients can trigger peaks of stress. Thus, these findings and our results highlight the importance to develop longitudinal studies that evaluate and clarify the role of several covariables commonly associated with the etiology of halitosis.
Fixed orthodontic appliances can affect the microbial diversity in the oral cavity since braces can promote bacterial adhesion, biofilm formation, and accumulation of anaerobic microorganisms. SVCs, such as hydrogen sulfide (H2S) and methyl mercaptan (CH3SH), are the main components of oral malodor and are produced as end-products of the proteolytic processes of oral microorganisms. Gram-negative anaerobic bacteria are the predominant producers of H2S and CH3SH since they are the main pathway of proteolysis through the metabolism of sulfur-containing amino acids. Thus, Gram-negative anaerobic bacteria play a crucial role in halitosis. In addition, the type of bracket used appears to not influence microbial colonization and the occurrence of halitosis under orthodontic treatment., These previous findings corroborate with our results and suggest that dental students are very sensitive to oral odors which do not match with halitosis.
Our findings have some limitations and a careful analysis of the results is strongly recommended. It was not possible to recruit an equal proportion of participants regarding their sexes since dentistry courses in Brazil traditionally have a larger female audience. Another limitation remains on the fact that only a specific population was investigated (dental students). Previous studies have demonstrated that self-assessment of halitosis can underestimate the prevalence of this condition.,,, However, these findings are based on the investigation of nondental students. Thus, our hypothesis was that dental students appear to have higher knowledge regarding oral conditions and familiarization of oral malodors than nondental students which could result in more accuracy of self-assessment of halitosis. However, further studies are needed to confirm the results and to investigate the correlation between self-assessment and diagnosis of halitosis among the general population.
| Conclusion|| |
The use of fixed orthodontic appliances affected the self-assessment of halitosis which was not clinically confirmed by the SVC measurements. It was not verified a correlation between subjective and objective methods to diagnose halitosis in dental students. Moreover, dental students appear to overestimate their oral malodor.
Financial support and sponsorship
This study was financed in part by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil – Finance Code 001.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Aimetti M, Perotto S, Castiglione A, Ercoli E, Romano F. Prevalence estimation of halitosis and its association with oral health-related parameters in an adult population of a city in North Italy. J Clin Periodontol 2015;42:1105-14.
Chen X, Zhang Y, Lu HX, Feng XP. Factors associated with halitosis in white-collar employees in shanghai, China. PLoS One 2016;11:e0155592.
Kapoor U, Sharma G, Juneja M, Nagpal A. Halitosis: Current concepts on etiology, diagnosis and management. Eur J Dent 2016;10:292-300. [Full text]
Bollen CM, Beikler T. Halitosis: The multidisciplinary approach. Int J Oral Sci 2012;4:55-63.
Silva MF, Leite FR, Ferreira LB, Pola NM, Scannapieco FA, Demarco FF, et al
. Estimated prevalence of halitosis: A systematic review and meta-regression analysis. Clin Oral Investig 2018;22:47-55.
Sökücü O, Akpınar A, Özdemir H, Birlik M, Çalışır M. The effect of fixed appliances on oral malodor from beginning of treatment till 1 year. BMC Oral Health 2016;16:14.
Kaygisiz E, Uzuner FD, Yuksel S, Taner L, Çulhaoğlu R, Sezgin Y, et al
. Effects of self-ligating and conventional brackets on halitosis and periodontal conditions. Angle Orthod 2015;85:468-73.
Babacan H, Sokucu O, Marakoglu I, Ozdemir H, Nalcaci R. Effect of fixed appliances on oral malodor. Am J Orthod Dentofacial Orthop 2011;139:351-5.
Nalçacı R, Özat Y, Çokakoğlu S, Türkkahraman H, Önal S, Kaya S. Effect of bracket type on halitosis, periodontal status, and microbial colonization. Angle Orthod 2014;84:479-85.
Abdulraheem S, Paulsson L, Petrén S, Sonesson M. Do fixed orthodontic appliances cause halitosis? A systematic review. BMC Oral Health 2019;19:72.
Romano F, Pigella E, Guzzi N, Aimetti M. Patients' self-assessment of oral malodour and its relationship with organoleptic scores and oral conditions. Int J Dent Hyg 2010;8:41-6.
Bensafi M, Rouby C. Individual differences in odor imaging ability reflect differences in olfactory and emotional perception. Chem Senses 2007;32:237-44.
Winkel EG, Roldán S, Van Winkelhoff AJ, Herrera D, Sanz M. Clinical effects of a new mouthrinse containing chlorhexidine, cetylpyridinium chloride and zinc-lactate on oral halitosis. A dual-center, double-blind placebo-controlled study. J Clin Periodontol 2003;30:300-6.
Eli I, Baht R, Koriat H, Rosenberg M. Self-perception of breath odor. J Am Dent Assoc 2001;132:621-6.
Oho T, Yoshida Y, Shimazaki Y, Yamashita Y, Koga T. Characteristics of patients complaining of halitosis and the usefulness of gas chromatography for diagnosing halitosis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;91:531-4.
Iwakura M, Yasuno Y, Shimura M, Sakamoto S. Clinical characteristics of halitosis: Differences in two patient groups with primary and secondary complaints of halitosis. J Dent Res 1994;73:1568-74.
Rosenberg M, Kozlovsky A, Gelernter I, Cherniak O, Gabbay J, Baht R, et al
. Self-estimation of oral malodor. J Dent Res 1995;74:1577-82.
Eli I, Baht R, Kozlovsky A, Rosenberg M. The complaint of oral malodor: Possible psychopathological aspects. Psychosom Med 1996;58:156-9.
Rosenberg M, Kozlovsky A, Wind Y, Mindel E. Self-assessment of oral malodor 1 year following initial consultation. Quintessence Int 1999;30:324-7.
Nakhleh MK, Quatredeniers M, Haick H. Detection of halitosis in breath: Between the past, present, and future. Oral Dis 2018;24:685-95.
Troger B, Almeida HL Jr, Duquia RP. Emotional impact of halitosis. Trends Psychiatr Psychother 2014;36:219-21.
Ashwath B, Vijayalakshmi R, Malini S. Self-perceived halitosis and oral hygiene habits among undergraduate dental students. J Indian Soc Periodontol 2014;18:357-60.
] [Full text]
Rani H, Ueno M, Zaitsu T, Furukawa S, Kawaguchi Y. Factors associated with clinical and perceived oral malodor among dental students. J Med Dent Sci 2015;62:33-41.
Lujo M, Meštrović M, Ivanišević Malčić A, Karlović Z, Matijević J, Jukić S. Knowledge, attitudes and habits regarding oral health in first- and final-year dental students. Acta Clin Croat 2016;55:636-43.
Guo R, Lin Y, Zheng Y, Li W. The microbial changes in subgingival plaques of orthodontic patients: A systematic review and meta-analysis of clinical trials. BMC Oral Health 2017;17:90.
Silva MF, Cademartori MG, Leite FRM, López R, Demarco FF, Nascimento GG. Is periodontitis associated with halitosis? A systematic review and meta-regression analysis. J Clin Periodontol 2017;44:1003-9.
von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP, et al
. The strengthening the reporting of observational studies in epidemiology (STROBE) statement: Guidelines for reporting observational studies. J Clin Epidemiol 2008;61:344-9.
Gray D, McIntyre G. Does oral health promotion influence the oral hygiene and gingival health of patients undergoing fixed appliance orthodontic treatment? A systematic literature review. J Orthod 2008;35:262-9.
Pachêco-Pereira C, Pereira JR, Dick BD, Perez A, Flores-Mir C. Factors associated with patient and parent satisfaction after orthodontic treatment: A systematic review. Am J Orthod Dentofacial Orthop 2015;148:652-9.
Almas K, Al-Hawish A, Al-Khamis W. Oral hygiene practices, smoking habit, and self-perceived oral malodor among dental students. J Contemp Dent Pract 2003;4:77-90.
Setia S, Pannu P, Gambhir RS, Galhotra V, Ahluwalia P, Sofat A. Correlation of oral hygiene practices, smoking and oral health conditions with self perceived halitosis amongst undergraduate dental students. J Nat Sci Biol Med 2014;5:67-72.
Pham TA. Comparison between self-estimated and clinical oral malodor. Acta Odontol Scand 2013;71:263-70.
Dudzik A, Gajewska CM, Bartyzel LK. An evaluation of halitosis using oral chroma™ data manager, organoleptic scores and patients' subjective opinions. J Int Oral Health 2015;7:6-11.
Stuck BA, Fadel V, Hummel T, Sommer JU. Subjective olfactory desensitization and recovery in humans. Chem Senses 2014;39:151-7.
Humagain M, Dixit S, Bhandari B, Khanal S, Singh PK. Self-perception of halitosis among undergraduate students of kathmandu university school of medical sciences-A questionnaire based study. Kathmandu Univ Med J 2018;16:89-93.
Buunk-Werkhoven Y, Dijkstra-le Clercq M, Verheggen-Udding E, de Jong N, Spreen M. Halitosis and oral health-related quality of life: A case report. Int J Dent Hyg 2012;10:3-8.
Calil CM, Marcondes FK. Influence of anxiety on the production of oral volatile sulfur compounds. Life Sci 2006;79:660-4.
Nani BD, Lima PO, Marcondes FK, Groppo FC, Rolim GS, Moraes AB, et al
. Changes in salivary microbiota increase volatile sulfur compounds production in healthy male subjects with academic-related chronic stress. PLoS One 2017;12:e0173686.
Alzahem AM, van der Molen HT, Alaujan AH, Schmidt HG, Zamakhshary MH. Stress amongst dental students: A systematic review. Eur J Dent Educ 2011;15:8-18.
Sun F, Ahmed A, Wang L, Dong M, Niu W. Comparison of oral microbiota in orthodontic patients and healthy individuals. Microb Pathog 2018;123:473-7.
Suzuki N, Yoneda M, Takeshita T, Hirofuji T, Hanioka T. Induction and inhibition of oral ma lodor. Mol Oral Microbiol 2019;34:85-96.
Uzuner FD, Kaygisiz E, Cankaya ZT. Effect of the bracket types on microbial colonization and periodontal status. Angle Orthod 2014;84:1062-7.
Bornstein MM, Kislig K, Hoti BB, Seemann R, Lussi A. Prevalence of halitosis in the population of the city of Bern, Switzerland: A study comparing self-reported and clinical data. Eur J Oral Sci 2009;117:261-7.
[Table 1], [Table 2], [Table 3]