Systematic Review

Changes in the pH and the Flow Rate of Saliva During Orthodontic Treatment with Fixed Orthodontic Appliances: A Systematic Review


  • Reda Jakavičė
  • Alvyda Žarovienė

Received Date: 21.04.2022 Accepted Date: 09.10.2022 Turk J Orthod 2023;36(3):199-207 PMID: 37782023

This systematic review aimed to assess salivary flow and pH changes at various stages of orthodontic treatment with fixed appliances. A comprehensive searches in electronic databases, including Medline, ResearchGate, Web of Science, SAGE Journals, Cochrane Oral Health Group’s Trials Register, and ScienceDirect, without any publication date restrictions until January 2022 was conducted. The Pre-ferred Reporting Items for Reporting Systematic Reviews and Meta Analyses (PRISMA 2020 version) protocol was adopted and the risk of bias assessments were performed using the Cochrane ROBINS-I tool for non-randomized studies. Out of 4902 articles, 25 were fully evaluated, and seven studies that met the inclusion criteria were included in the review. The results showed that orthodontic treatment with fixed orthodontic appliances increased the stimulated salivary flow rate during various stages of treatment. However, the unstimulated salivary flow rate showed different changes. Furthermore, stimulated salivary pH increased, whereas unstimulated salivary pH significantly decreased, depending on the specific period of orthodontic treatment. Overall, fixed orthodontic appliances have an impact on salivary flow rate and pH during different stages of treatment. Nevertheless, the current literature is insufficient to draw definitive conclusions. More well-designedrandomized studies with larger sample sizes are necessary to confirm these findings.

Keywords: Saliva, fixed orthodontic treatment, fixed orthodontic appliances, dental brackets

Main Points

• The aim of the study was to evaluate changes in salivary flow and pH in different periods of orthodontic treatment with fixed appliances.

• Most studies have stated that stimulated salivary flow rate and pH tend to increase.

• According to the data, unstimulated salivary flow rate changes, while unstimulated saliva pH decreases.


Orthodontic treatment effectively improves people’s quality of life by restoring regular and stable occlusion, optimal chewing function, and dentofacial aesthetics.1 However, the use of fixed orthodontic devices can have adverse effects on soft tissues, teeth, and saliva.2 Nowadays, ensuring good oral hygiene with fixed orthodontic appliances remains a significant challenge, as the areas around brackets are difficult to clean and prolonged plaque retention, which may cause white enamel spot lesions and gingivitis.3,4 Saliva typically consist of water (99%), and organic and non-organic elements (1%).5 During orthodontic treatment, plaque stagnation can lead to changes in the qualitative and quantitative indicators of saliva. The concentration of cariogenic bacteria, such as Streptococcus mutans and Lactobacillus, may increase due to the increased plaque retention, which promotes the development of active tooth decay.6,7 Changes in the quality of saliva are often observed in its pH, buffer capacity and the viscosity of saliva.8 Saliva pH, as a qualitative indicator of saliva, is particularly important for oral and dental health. The optimal saliva pH in healthy individuals typically ranges from 6.7 to 7.3.9 However, in some cases, orthodontic treatment can lead to a decrease in salivary pH with changes in oral microbes.10 A decreased saliva pH can increase the risk of demineralization of dental hard tissues and inflammation of the gums.11

During orthodontic treatment with fixed orthodontic devices, the quantitative indicator of saliva, i.e., which is the amount of saliva excreted, also undergoes changes. The statistical mean of average unstimulated saliva output is typically between 0.25-0.35 mL/min, while the non-pathological mean volume of stimulated saliva output ranges from 1-3 mL/min.12 A decrease in saliva secretion, can lead to dry mouth, known as xerostomia. Decreased salivation may be associated with tooth decay, demineralization of dental hard tissues, and gingival inflammation. Fiyaz et al.13 found that the saliva flow of selected patients with tooth decay was almost twice that of the control group, without caries.

However, some patients may experience an increase in saliva output during orthodontic treatment, and hypersalivation is diagnosed when saliva levels rise above the reference range.14 Meanwhile, increased but non-pathological salivation can have benefits, such as improving mouth cleansing and enhancing the antimicrobial properties of saliva, leading to better anti-caries resistance. The study suggests that hypersalivation during orthodontic treatment may be associated with increased patient sensitivity due to the presence of fixed orthodontic devices.11 Therefore, understanding how the qualitative and quantitative parameters of excreted saliva may change during the duration of orthodontic treatment is crucial. Numerous studies with diverse patient samples have explored the relationship between the use of fixed orthodontic appliances and alterations in salivary parameters, yielding different conclusions.2,11,15,16,17,18,19 The primary objective of this systematic review was to assess the methodological quality, analyse and summarize the currently available information on changes in salivary flow and pH in different periods of orthodontic treatment with fixed appliances. The null hypothesis tested was that there would be no significant difference between baseline and during orthodontic treatment regarding these salivary parameters.


Protocol and Registration

A systematic review was conducted in line with the PRISMA 2020 version statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), as illustrated in Figure 1. The protocol was registered with PROSPERO (registration number CRD42022300434).

Eligibility Criteria

According to the Participants Intervention Comparison Outcome Study design schema (PICOS), the study included prospective trials (S) on patients undergoing orthodontic treatment (P) with fixed orthodontic appliances (I). In these studies, changes in quantitative and qualitative indices of saliva were observed at different times of treatment (C). The outcome of this systematic review included changes in salivary flow and pH at different time points during long-term orthodontic treatment (O).

The criteria for the study inclusion were full-text studies, clinical studies with humans, patients treated with fixed orthodontic appliances, and stimulated and unstimulated saliva samples collected before orthodontic treatment, and at different time points during orthodontic treatment. Additionally, the studies needed to present the exact mean values of salivary flow rate and pH were presented in the studies. Exclusion criteria were all case reports, case series, systematic reviews, and animal and in vitro studies. Furthermore, studies comparing saliva parameters between different orthodontic appliances or studies involving patients treated with orthodontic removable appliances were also excluded. The number of sample sizes was not a criterion for exclusion.

Search Strategy

The systematic search was conducted in six electronic databases, which included Medline, ResearchGate, Web of Science, SAGE Journals, Cochrane Oral Health Group’s Trials Register, and ScienceDirect. The databases were searched using the specified keywords both separately and in different combinations. The search strategy used for PubMed was as follows: (saliva OR salivary) AND (fixed orthodontic appliances OR fixed orthodontic treatment OR orthodontic braces OR orthodontic brackets OR dental braces OR dental brackets OR brackets OR braces). This search strategy was appropriately adapted for ResearchGate, SAGE Journals, Web of Science, Cochrane Oral Health, and ScienceDirect electronic databases. The selection of studies was carried out independently by two investigators. Any discrepancies between the investigators were resolved through discussion. It’s important to note that the librarian was not consulted during this process.

Study Selection

Before beginning the search in the selected databases, the search strategy was discussed and developed by two analyzers, and thereafter the study selection was carried out by two researchers. Search filters were applied to refine the results and duplicates entries were removed. Initially, the titles and abstracts of the identified studies were analyzed. Following this initial screening, complete articles were selected for a more comprehensive review and analysis, based on the predefined eligibility criteria. If the articles met the inclusion criteria for the review, the entire content of those articles was read to make the final decision regarding their suitability for inclusion in the systematic review.

Data Extraction

The characteristics and data of the included studies that met the eligibility criteria were extracted by two reviewers. Two independent reviewers performed data extraction using spreadsheets (Microsoft Excel Version 16.49, Redmond, WA, USA). The following variables were recorded for each reviewed article: author, country, year of publication, type of study, characteristics of study participants such as sample size, sex, age, intervention type (fixed orthodontic appliances), type of saliva samples, evaluation methods (methods of saliva measurements and timing on evaluation), and treatment outcomes (changes in salivary flow rate and pH in different time points). To assess the agreement between the two reviewers’ data extraction, Kappa statistics were utilized after the initial selection of articles.


Study Characteristics

The characteristics of the included studies are summarized in Table 1.

Participants in the included studies consisted of a total of 242 patients treated with fixed orthodontic appliances. The sample sizes of the studies varied, ranging from 21 to 60 patients. Additionally, the age of the participants in the studies ranged from 10 to 34 years, with male patients being 84 and female 98. in the study conducted by Alshahrani et al.11, the gender of 60 patients was not separated or specified in the data.

Intervention: Most studies did not indicate which bracket systems were used; only two studies identified Edgewise braces2,19 and one study utilized self-ligating braces.17 In all studies, the most popular method of saliva collection was the spitting method into a sterile tube. The samples were collected at different times of the day between 8 am and 3.30 pm.2,15,16,17,18,19 However, one study did not specify the exact time of day for sample collection.11 Out of the included studies, four studies, collected, unstimulated saliva samples,2,11,15,16 while the other three studies used stimulated saliva obtained through paraffin wax or orthodontic elastic bands.17,18,19

Quality Assessment

To assess the quality of studies, the ROBINS-I tool for non-randomized studies was used, and the data are summarized in Table 2.20 The risk of bias within the non-randomized studies from the two trials was evaluated to have an overall moderate bias due to certain discrepancies in confounding and measurement of outcome domains.2,17 Three additional non-randomized studies11,15,19 were found to have an overall serious risk of bias. The other two studies16,18 were determined to present a critical risk of bias. The most problematic domains associated with bias were the lack of blinding, inadequate assessment of confounding factors, and imprecise outcome measurements.

Study Selection

The protocol for this systematic review followed the guidelines presented in the PRISMA 2020 version statement (Figure 1). For reference management, Mendeley Desktop 1.19.8 software (Mendeley Ltd, London, UK) was used. The electronic database search initially identified 5009 records. After duplicate removal, 4902 records remained, which were then screened for relevance. Screening of titles and abstracts resulted in the exclusion of 3504 studies. Additionally, 1373 full-text reports were not accessible among the 25 full-text articles we assessed for eligibility, 18 studies were subsequently excluded.3,6,8,10,12,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43 Finally, 7 studies were included in a systematic review.2,11,15,16,17,18,19 An overview of the search results and the screening process is summarized in the study flow chart (Figure 1).

Results of Individual Studies

The results of the seven included studies are summarized and presented in Table 3Figure 2 demonstrates changes in the stimulated and unstimulated salivary flow rate during orthodontic treatment periods, while Figure 3 demonstrates changes in the stimulated and unstimulated salivary pH.

Unstimulated Salivary Flow Rate

Three of the included studies analyzed the unstimulated salivary flow rate.11,15,16 Due to the observed different in age groups and the fact that saliva production decreases with age, the results of unstimulated salivary flow rate were separated into two groups. The first age group included participants aged 16-32 years.11,16 Alshahrani et al.11 reported that the unstimulated salivary flow rate was significantly higher one week before orthodontic treatment than after 2 months of orthodontic treatment (p<0.05). According to the results, the mean unstimulated saliva flow rate before treatment was 184.57±53.41 μL/min, compared to 149.12±50.57 μL/min of flow rate after 2 months of treatment.11 In contrast, Altaee et al.16 stated that the unstimulated saliva flow rate of participants increased significantly during the 1-month orthodontic treatment period, from 0.52±0.1 mL/min to 0.83±0.16 mL/min (p<0.05). The second age group included participants aged 12-18 years.15 Arab et al.15 analyzed younger patients before orthodontic treatment and at 6, 12, 18 weeks of orthodontic treatment with fixed appliances and revealed that the unstimulated salivary flow rate increased significantly after every 6 weeks of treatment (p<0.05). In detail, the salivary flow rate before starting fixed orthodontic treatment (1.13±0.42 mL/min) had a significantly lower mean than after 18 weeks of treatment (1.22±0.42 mL/min).15 Evaluating the unstimulated salivary flow rate of these three studies, a general conclusion cannot be drawn due to the different results observed between the studies.

Stimulated Salivary Flow Rate

Three studies evaluated the status of stimulated salivary flow rate parameters.17,18,19 In the study by Sánchez and Honores18 the average stimulated salivary flow rate changed significantly from 1.12 mL/min to 1.36 mL/min after a month of bracket placement. However, these results should be interpreted with caution due to the wide range of age groups involved (10-34 years). Nonetheless, similar results were reported by researchers in two other studies over time.17,19 Kouvelis et al.17 showed a significantly greater stimulated salivary flow rate after 12 weeks (1.67 mL/min) of treatment compared to before treatment (1.42 mL/min). Peros et al.19 also showed a significant increase in stimulated salivary flow rate with values increasing from 1.12 mL/min before treatment to 1.33 mL/min after 18 weeks of treatment. Regarding changes between the genders, it was noticeable that the stimulated salivary flow rate of females increased by 0.22 from baseline to 1 month (from 1.16 mL/min to 1.38 mL/min), while that of men increased by 0.25 (from 1.06 mL/min to 1.31 mL/min) during the same period of treatment.18 Concerning the status of stimulated salivary flow rate, the results of the studies showed a significant increase during different periods of long-term orthodontic treatment.

Unstimulated Salivary pH

Four of the included studies analyzed the unstimulated salivary pH in different periods of treatment with fixed orthodontic appliances.2,11,15,16 Evaluating the records of patients who underwent such treatment revealed that unstimulated salivary pH significantly decreased after various periods of orthodontic treatment.11,15,16 Alshahrani et al.11 reported a decrease in salivary pH by 0.39±0.29 during a 2- month period (p<0.05), while Altaee et al.16 showed a decrease in pH by 0.21±0.13 during a 1-month period (p<0.05). The findings from the study by Arab et al.15 also showed a significant reduction in unstimulated salivary pH from 7.18±0.35 to 6.76±0.28 during a 12-week period; however, from 12 to 18 weeks, salivary pH increased to 6.8±0.3.15 In the study conducted by Zogakis et al.2, the reduction in unstimulated salivary pH was 0.07, but it was not significant compared to the values before and 4-6 weeks of orthodontic treatment (p>0.05). Regarding the status of unstimulated salivary pH , the results of three studies revealed a significant decrease during different periods of orthodontic treatment, while in one study, the decrease in salivary pH was not significant.

Stimulated Salivary pH

Two authors investigated stimulated salivary pH.17,19 Kouvelis et al.17 and Peros et al.19 published results of stimulated salivary pH. Kouvelis et al.17 studied stimulated salivary pH at different time points: before treatment - 7.63, 4 weeks of treatment - 7.67, and 12 weeks of treatment - 7.78. The salivary pH of stimulated saliva increased by 0.15 during the 12-week period, but the difference was not statistically significant (p>0.05).17 On the other hand, Peros et al.19 reported that the measurements of stimulated salivary pH increased significantly compared the initial examination (7.18) during the 12-week period of treatment (7.42). However, there was a reduction of stimulated salivary pH by 0.12 during the 12- to 18-week period.


Salivary Flow Rate

No single conclusion was reached when evaluating the unstimulated salivary flow rate.11,15,16 Other authors have also obtained variable results. Li et al.33 found an increase in the non-stimulated salivary flow rate during the first month, followed by a return to the norm after 3 months. Three other authors10,21,34 presented one month and half-year results of unstimulated salivary flow, where a significant increase was observed; however, in one study, the authors did not provide accurate measurements of salivary flow, and results were presented in the ranges (<3.5 mL, 3.5-5 mL., >5 mL).21 Considering an even longer treatment period, such as one year, Alessandri Bonetti et al.8 found an increased salivary flow rate, but these results were not statistically significant. Different results may have been obtained because most study groups were not divided into smaller age groups, and adults were not separated from children. It is known that children’s saliva secretion is more intensive compared to adults and decreases over time.35,36 Another important factor that may affect the results is the evaluation of salivation over a long period of time,since orthodontic treatment itself takes an average of about 19.9 months.37 Therefore, it is essential to evaluate the salivary flow rate over a long period, and the results may change over time due to adaptive processes happening in the human body.

Some authors compared changes between genders. Females’ unstimulated salivary flow rate increased during 1 month of treatment by 0.13 (from 0.51 mL/min to 0.64 mL/min), while men’s salivary flow rate increased by 0.2 (from 0.51 mL/min to 0.71 mL/min) during the same period of treatment. Thus, the unstimulated salivary flow rate was greater in males than females as shown in a study by Altaee et al.16 However, Alessandri Bonetti et al.8 found no significant difference between the sexes over a period of one year.

Concerning stimulated salivary flow rate, as observed in the results of the present systematic review, all authors reported an increase in stimulated salivary flow rate at different treatment periods compared to baseline, even between different age groups.17,18,19 Similar findings were found by other authors: Lara-Carillo et al.12 found an increased stimulated salivary flow rate in patients after 1 month of orthodontic treatment. Increased rates were also found in patients treated with fixed orthodontic appliances one and three months later.38,39 In one study, a significant increase in the stimulated salivary flow rate was also established even six months after the placement of fixed orthodontic appliances.21 This confirms the statement that bonded brackets create a mechanical stimulus to receptors in the brain, promoting increased salivary secretion.

Comparing changes between genders, an increased stimulated salivary flow rate was obtained with a greater change in males compared to females, where the initial flow rate was higher in the female group.18 These results may be inaccurate due to the inclusion of various age groups (10-34 years). Lara-Carillo et al.12 also compared results between genders and found increased stimulated saliva flow in both gender groups, but with a higher initial flow rate in the male group. On the other hand, Kado et al.40 evaluated stimulated salivary flow between genders of pre-orthodontic patients and found a significantly higher flow rate in males than in females. These results were explained by the smaller size of salivary glands in females compared to males the influence of hormonal patterns.12

Salivary pH

A reduction in unstimulated salivary pH during orthodontic treatment was found in all included studies that evaluated the pH of unstimulated saliva.11,15,16 These results are consistent with those reported by Kanaya et al.39, who found a decreased pH associated with an increased number of acidogenic bacteria, such as Streptococcus mutans, Lactobacilli.39 When the pH decreases sharply and reaches the critical value (pH 5.5), the balance between demineralization and remineralization is pushed toward mineral loss and demineralization. Jurela et al.10 also found a decrease in salivary pH of patients treated with braces and associated this decrease with an increased plaque index. This may be explained by the fact that plaque buildup is a mass of bacteria that produce acid and results in reduction in salivary pH.

Comparing the results of stimulated salivary pH, an increase in pH was observed during the 12-week period.2,17,19 Lara-Carillo et al.12 also showed an increase in pH after one month of orthodontic treatment, while Maret et al.6 demonstrated that 6 months with orthodontic appliances increased salivary pH. Specifically, Maret et al6. compared the salivary pH of children with fixed orthodontic appliances (pH=7.49) to a control group of children (pH=7.37) without orthodontic treatment, showing a statistically significant difference in pH levels. These results agree with the study by Ivanovic et al.30, where the pH of saliva statistically significantly increased 12 weeks after wearing fixed braces compared to the control group of respondents who were not treated orthodontically. A higher pH value indicates higher basicity. However, it is essential to note that fixed appliances remain in the mouth for an extended period, and oral prophylaxis measures, such as oral hygiene practices, diet advice, and topical fluoride application, should be considered to maintain oral health.

Moreover, certain unexplored variables can significantly influence the oral environment. The utilization of probiotics, parabiotics, postbiotics, and natural compounds has demonstrated the ability to modify clinical and microbiological parameters in periodontal patients, a which may also have an impact during orthodontic treatment. All these variables should be considered in future clinical trials.41,42

Study Limitations

This systematic literature review analyzed the currently available information on changes in salivary flow and pH during orthodontic treatment with fixed orthodontic appliances. The quality of the included studies was mainly medium, which means that the results of these studies should be interpreted with caution. Some studies provided limited details of their methods, making quality assessment difficult. The main limitations of the included studies were; blinding, assessment of confounding factors, non-homogeneous study designs, and small sample sizes. Additionally, in some studies, children and adults were not separated into different groups, and the evaluation of salivary parameters was not consistently performed at the same time as orthodontic treatment. Some studies had short follow-up periods, limiting the ability to assess long-term outcomes. The accuracy of saliva parameters might have been influenced by the different collection times of saliva, emphasizing the importance of standardized saliva collection protocols in future research. To gain a more comprehensive understanding of the long-term effects, future research should consider following the participants for extended evaluation periods. The limited number of studies evaluating the same procedures, outcomes, and evaluation periods precluded the performance of meta-analyses. Due to resource limitations, full texts of non-English-language articles identified during the searches were not retrieved, potentially resulting in the omission of relevant evidence. It is important to note that this study was not funded, and the authors declare that there are no conflicts of interest.


Orthodontic treatment with fixed orthodontic appliances increases the salivary flow rate during various periods of orthodontic treatment. However, the changes in salivary pH differ depending on whether the saliva is stimulated or unstimulated. Stimulated salivary pH tends to increase during orthodontic treatment, while unstimulated salivary pH tends to decrease. Although the published results are promising, they are not sufficient to confirm final changes in quantitative and qualitative indices of saliva during orthodontic treatment with fixed appliances. Further well-conducted multicenter randomized studies with a large sample are needed to confirm this statement to establish more robust evidence.


Peer-review: Externally peer-reviewed.

Author Contributions: Concept - R.J., A.Ž.; Design - R.J., A.Ž.; Supervision - R.J., A.Ž.; Data Collection and/or Processing - R.J., A.Ž.; Analysis and/or Interpretation - R.J., A.Ž.; Writing - R.J., A.Ž.; Critical Review - R.J., A.Ž.

Declaration of Interests: The authors have no conflicts of interest to declare.

Funding: No financial assistance was received to support this study.

  1. Zarzycka-Kogut K, Pucek M, Szymańska J.Orthodontic Treatment – Complications and Preventive Measures. Polish Journal of Public Health. 2014;124(2):103-106.]
  2. Zogakis IP, Koren E, Gorelik S, Ginsburg I, Shalish M. Effect of fixed orthodontic appliances on nonmicrobial salivary parameters. Angle Orthod. 2018;88(6):806-811.]
  3. Mei L, Chieng J, Wong C, Benic G, Farella M. Factors affecting dental biofilm in patients wearing fixed orthodontic appliances. Prog Orthod. 2017;18:4.]
  4. Demling A, Heuer W, Elter C, et al. Analysis of supra- and subgingival long-term biofilm formation on orthodontic bands. Eur J Orthod. 2009;31(2):202-206.]
  5. Llena-Puy C. The rôle of saliva in maintaining oral health and as an aid to diagnosis. Med Oral Patol Oral Cir Bucal. 2006;11(5):E449-E455.]
  6. Maret D, Marchal-Sixou C, Vergnes JN, et al. Effect of fixed orthodontic appliances on salivary microbial parameters at 6 months: a controlled observational study. J Appl Oral Sci. 2014;22(1):38-43.]
  7. Mummolo S, Marchetti E, Giuca MR, et al. In-office bacteria test for a microbial monitoring during the conventional and self-ligating orthodontic treatment. Head Face Med. 2013;9:7.]
  8. Alessandri Bonetti G, Incerti Parenti S, Garulli G, Gatto MR, Checchi L. Effect of fixed orthodontic appliances on salivary properties. Prog Orthod. 2013;14:13.]
  9. Ramya AS, Uppala D, Majumdar S, Surekha Ch, Deepak KG. Are salivary amylase and pH - Prognostic indicators of cancers? J Oral Biol Craniofac Res. 2015;5(2):81-5.]
  10. Jurela A, Sudarević K, Budimir A, Brailo V, Lončar Brzak B, Janković B. Clinical and Salivary Findings in Patients with Metal and Crystalline Conventional and Self-Ligating Orthodontic Brackets. Acta Stomatol Croat. 2019;53(3):224-230.]
  11. Alshahrani I, Hameed MS, Syed S, Amanullah M, Togoo RA, Kaleem S. Changes in essential salivary parameters in patients undergoing fixed orthodontic treatment: A longitudinal study. Niger J Clin Pract. 2019;22(5):707-712.]
  12. Lara-Carrillo E, Montiel-Bastida NM, Sánchez-Pérez L, Alanís-Tavira J. Effect of orthodontic treatment on saliva, plaque and the levels of Streptococcus mutans and Lactobacillus. Med Oral Patol Oral Cir Bucal. 2010;15(6):e924-e929.]
  13. Fiyaz M, Ramesh A, Ramalingam K, Thomas B, Shetty S, Prakash P. Association of salivary calcium, phosphate, pH and flow rate on oral health: A study on 90 subjects. J Indian Soc Periodontol. 2013;17:454-460.]
  14. Miranda-Rius J, Brunet-Llobet L, Lahor-Soler E, Farré M. Salivary Secretory Disorders, Inducing Drugs, and Clinical Management. Int J Med Sci. 2015;12(10):811-824.]
  15. Arab S, Nouhzadeh Malekshah S, Abouei Mehrizi E, Ebrahimi Khanghah A, Naseh R, Imani MM. Effect of Fixed Orthodontic Treatment on Salivary Flow, pH and Microbial Count. J Dent (Tehran). 2016;13(1):18-22.]
  16. Altaee ZH, Al-Ajeely MH, Abdulateef YM. Prevalence, Effect of fixed orthodontic appliance on some factors and elements of saliva. Sulaimani Dent J. 2015;2(2):89-93.]
  17. Kouvelis G, Papadimitriou A, Merakou K, Doulis I, Karapsias S, Kloukos D. A Prospective Cohort Study Assessing the Impact of Fixed Orthodontic Appliances on Saliva Properties and Oral Microbial Flora. Oral Health Prev Dent. 2021;19(1):67.]
  18. Sánchez BE, Honores CM. Effect of orthodontic fixed appliances on salivary flow and viscosity. Revista Mexicana de Ortodoncia. 2015;3(3):185-189.]
  19. Peros K, Mestrovic S, Anic-Milosevic S, Slaj M. Salivary microbial and nonmicrobial parameters in children with fixed orthodontic appliances. Angle Orthod. 2011;81(5):901-906.]
  20. Sterne JA, Hernán MA, Reeves BC, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions. BMJ. 2016;355:i4919.]
  21. Anu V, Madan Kumar PD, Shivakumar M. Salivary flow rate, pH and buffering capacity in patients undergoing fixed orthodontic treatment - A prospective study. Indian J Dent Res. 2019;30(4):527-530.]
  22. Papadimitriou A, Kouvelis G, Fanaropoulou T, et al. Effects of Self-ligating Orthodontic Appliances on the Periodontal Health of Adolescents: A Prospective Cohort Study. Oral Health Prev Dent. 2021;19(1):129-135.]
  23. Silva Andrade A, Marcon Szymanski M, Hashizume LN, Santos Mundstock K, Ferraz Goularte J, Hauber Gameiro G. Evaluation of stress biomarkers and electrolytes in saliva of patients undergoing fixed orthodontic treatment. Minerva Stomatol. 2018;67(4):172-178.]
  24. Topaloglu-Ak A, Ertugrul F, Eden E, Ates M, Bulut H. Effect of orthodontic appliances on oral microbiota--6 month follow-up. J Clin Pediatr Dent. 2011;35(4):433-6.]
  25. Pereira IF, Brasileiro CB, Kleperon NP, et al. Comparative study of oral and salivary parameters in patients with and without loss of bone mass. Braz Oral Res. 2018;32:e54.]
  26. Kado I, Hisatsune J, Tsuruda K, Tanimoto K, Sugai M. The impact of fixed orthodontic appliances on oral microbiome dynamics in Japanese patients. Sci Rep. 2020;10(1):21989.]
  27. Jurela A, Repic D, Pejda S, et al. The effect of two different bracket types on the salivary levels of S mutans and S sobrinus in the early phase of orthodontic treatment. Angle Orthod. 2013;83(1):140-5.]
  28. Lombardo L, Ortan YÖ, Gorgun Ö, Panza C, Scuzzo G, Siciliani G. Changes in the oral environment after placement of lingual and labial orthodontic appliances. Prog Orthod. 2013;14:28.]
  29. Mummolo S, Tieri M, Nota A, et al. Salivary concentrations of Streptococcus mutans and Lactobacilli during an orthodontic treatment. An observational study comparing fixed and removable orthodontic appliances. Clin Exp Dent Res. 2020;6(2):181-187.]
  30. Ivanovic T, Stojanovic L, Ivanovic D, Nikolic P, Milosavljevic Z, Milinkovic M. Effects of the fixed orthodontic therapy on biochemical and microbiological parameters of saliva. Srp Arh Celok Lek. 2020;148(5-6):270-274.]
  31. Kukreja P, Hugar SM, Hallikerimath S, Sogi S, Badakar C, Thakkar P. Evaluation of the Effect of Fixed and Removable Appliances on Salivary Parameters (Salivary Flow Rate pH and Buffering Capacity) in Children Aged 5-12 Years: An In Vivo Study. Int J Clin Pediatr Dent. 2021;14(6):774-778. [CrossRef]
  32. Al-Haifi HAA, Ishaq RAA, Al-Hammadi MSA. Salivary pH changes under the effect of stainless steel versus elastomeric ligatures in fixed orthodontic patients: a single-center, randomized controlled clinical trial. BMC Oral Health. 2021;21(1):544. [CrossRef]
  33. Li Y, Hu B, Liu Y, Ding G, Zhang C, Wang S. The effects of fixed orthodontic appliances on saliva flow rate and saliva electrolyte concentrations. J Oral Rehabil. 2009;36(11):781-785.]
  34. Vanishree T, Panchmal GS, Shenoy R, Jodalli P, Sonde L, Kundapur N. Changes in the Oral Environment after Placement of Fixed Orthodontic Appliance for the Treatment of Malocclusion - a Descriptive Longitudinal Study. Oral Health Prev Dent. 2017;15(5):453-459.]
  35. Sonesson M, Eliasson L, Matsson L. Minor salivary gland secretion in children and adults. Arch Oral Biol. 2003;48(7):535-539.]
  36. Kudo F, Sawai A, Kuroyanagi R. Study of the unstimulated salivary flow rates by saliva collected by spitting method in children. Pediatr Otorhinolaryngol Jpn. 2014;35(1):17-20.]
  37. Tsichlaki A, Chin SY, Pandis N, Fleming PS. How long does treatment with fixed orthodontic appliances last? A systematic review. Am J Orthod Dentofacial Orthop. 2016;149(3):308-318.]
  38. Chang HS, Walsh LJ, Freer TJ. The effect of orthodontic treatment on salivary flow, pH, buffer capacity, and levels of mutans streptococci and lactobacilli. Aust Orthod J. 1999;15(4):229-234.]
  39. Kanaya T, Kaneko N, Amaike C, Fukushima M, Morita S, Miyazaki H, et al. The effect of orthodontic appliances on levels of Streptococcus mutans, Streptococcus sobrinus and microbial flora in saliva. Int Congr Ser. 2005;1284:189-190.]
  40. Kado I, Kunimatsu R, Yoshimi Y, Medina CC, Yamada S, Tanimoto K. Surveillance of salivary properties of pre-orthodontic patients in relation to age and sex. Sci Rep. 2021;11(1):6555.]
  41. Butera A, Gallo S, Maiorani C, Preda C, Chiesa A, Esposito F, et al. Pascadopoll M. et al. Manadement of Ginaival Bleedina in Periodontal Patients with Domiciliar Use or loothpastes Containina AvaluronicAcid, Lactoferrin, or Paraprobiotics: A Randomized Controlled Clinical Trial. Applied Sciences. 2021:11(18):8586.]
  42. Butera A, Gallo S, Pascadopoli M, Taccardi D, Scribante A. Home Oral Care of Periodontal Patients Using Antimicrobial Gel with Postbiotics, Lactoferrin, and Aloe Barbadensis Leaf Juice Powder vs. Conventional Chlorhexidine Gel: A Split-Mouth Randomized Clinical Trial. Antibiotics (Basel). 2022;11(1):118.]
  43. Teixeira H, Kaulfuss S, Ribeiro J, Pereira B, Brancher J, Camargo E. Calcium, amylase, glucose, total protein concentrations, flow rate, pH and buffering capacity of saliva in patients undergoing orthodontic treatment with fixed appliances. Dental Press J Orthod. 2012;17(2):157-161.]