Table 2.

Characteristics of the studies included in the analysis.

Authors (Year)	Study Design	Materials and Methods	Outcomes
Mario Portelli et al., 2017 [69]	Experimental	Twenty-three 12- to 16-year-old patients receiving multibracket self-ligating vestibular orthodontic appliances participated in the study. Salivary specimens collected at T1, T2, and T3.	-Repeated measures showed no significant time point differences. -No correlation found between dental hygiene and O.S. Orthodontic treatment with multibracket vestibular metallic appliances did not affect O.S. during the first ten weeks.
Vito Kovac et al., 2020 [70]	Experimental study	Compositions of stainless steel, nickel-titanium, cobalt-chromium, and β-titanium orthodontic alloys were simulated with mixtures of Fe, Ni, Cr, Co, Ti, and Mo metal ions to assess cytotoxicity and O.S. in Saccharomyces cerevisiae yeast strains.	-Cobalt-chromium alloy cytotoxic at 100 µM. -Reactive oxygen species and oxidative damage detected in stainless steel and both cobalt-chromium alloys at 1000 µM (wild-type yeast) and 100 µM (ΔSod1 and ΔCtt1 mutants). -In no yeast strain did simulated nickel-titanium or β-titanium alloy cause O.S.
Vito Kovac et al., 2022 [71]	Experimental	Orthodontic materials (archwires, brackets, and molar bands) were incubated in artificial saliva for 90 days. Metal composition and ion release were assessed. Metal ion mixtures were prepared to assess O.S., antioxidant enzyme defense, and protein damage.	-Beta titanium alloy released the fewest metal ions without inducing O.S. or protein damage. -Only at high concentrations could O.S. and protein damage result from stainless steel and cobalt-chromium alloy. -All orthodontic alloys affected antioxidant enzyme activity, but concentrations were below the maximum tolerated dose for oxidative stress.
Piotr Buczko et al., 2017 [72]	Experimental study	Included 37 volunteers, saliva samples collected immediately before, one week after, and twenty-four weeks after appliance insertion.	-Increased nickel concentration in saliva one week after treatment.
Lucía Angeles-Estrada et al., 2023 [73]	Experimental study	Oral epithelial cells from 51 healthy volunteers receiving orthodontic treatment. Sampling: Samples taken before treatment, at 6 months, and at 9 months. OS Assessment: Quantification of 8-hydroxy-2’deoxyguanosine (8-OHdG) levels. Gene Expression: Evaluation of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Genotoxicity Assessment: Multiplex polymerase chain reaction (PCR) and fragment analysis for DNA degradation and instability.	8-OHdG increased during treatment, but the increase was not statistically significant. SOD increased by 2.5-fold at 6 months and 2.6-fold at 9 months. CAT increased by threefold at 6 months and returned to baseline levels at 9 months. DNA degradation found in 8% and 12% of DNA samples at 6 and 9 months, respectively. DNA instability detected in 2% and 8% of DNA samples at 6 and 9 months, respectively.
Cristina Menéndez López-Mateos et al., 2022 [74]	Randomized clinical trial.	Participants: Non-randomized clinical trial with consecutively recruited patients over 18 years of age undergoing orthodontic treatment. Groups: Group A (48 patients) treated with clear aligners (Invisalign®), and Group B (19 patients) treated with Damon System® 0.22″ self-ligating brackets with light forces. Saliva Samples: collected at the beginning of treatment, 30 days later, and 90 days later by a single physician Analyzed Parameters: AOPP, TAC, and MPO levels.	AOPPs levels increased in both groups after the initial 30 days of orthodontic treatment with clear aligners or fixed self-ligating brackets. During the first stages of orthodontic therapy, whether using fixed brackets or clear aligners, there were no appreciable changes in TAC and MPO levels. During the first ninety days of therapy, there were no discernible changes in AOPP levels between self-ligating brackets and transparent aligners. Salivary antioxidant capacity remained similar between the two orthodontic techniques during the initial treatment phases.
Sevil Sema Atuğ Özcan et al., 2014 [75]	Experimental Study	Fifty volunteers who needed orthodontic treatment with fixed appliances participated in the trial. Saliva and GCF samples were taken prior to therapy, one month into the regimen, and six months into it. Periodontal clinical parameters were measured, and biochemical parameters (IL-1 β, TNF-α, 8-OHdG, NO, and MDA) were analyzed using ELISA and spectrophotometric methods.	IL-1 β level in GCF at the 6th month was significantly different from the baseline (p < 0.05). However, all other biochemical parameters in both saliva and GCF did not exhibit significant changes at any measurement period.
Vito Kovac et al., 2019 [17]	Experimental Comparative Study	A total of 54 male participants with malocclusion were randomly assigned to either the treatment group (TG; n = 27) or control group (CG; n = 27). Capillary blood was collected at various time points.	Short-term systemic O.S. was brought on by orthodontic treatment with fixed appliances; this stress resolved seven days following the placement of the archwire.
Cigdem Guler et al., 2015 [76]	Experimental study	-Thirty children divided into three groups. -Orthodontic composites: Transbond XT, Kurasper F, and GrenGloo. -Salivary TOS, TAS, and 8-OHdG levels measured at three time points: T1 (before treatment), T2 (1 month after appliance placement), and T3 (3 months after appliance placement).	-There are no appreciable variations in 8-OHdG, TOS, or TAS between the three orthodontic composites. -TAS decreased over time in all composite groups. Significant decreases observed for Kurasper F and GrenGloo. -Salivary cytotoxicity markers were not elevated by fixed orthodontic equipment using evaluated composite materials.
Martin et al., 2016 [77]	Randomized controlled trial	Thirty orthodontic patients were screened for gingivitis and divided into treatment and placebo groups. They underwent periodontal examinations and were instructed to apply a topical gel twice daily, then discontinue use.	Patients with gum disease can successfully reduce inflammation by using an anti-inflammatory gel made of essential oils to their teeth.
Kamath et al., 2023 [78]	Randomized controlled trial	A total of 30 participants with fixed orthodontic treatment, divided into test and control groups. Results were analyzed using Student’s paired and unpaired t-tests, focusing on plaque index, gingival index, and bleeding on probing.	Larger multicentric trials are required; however, aloe vera, the gold standard mouthwash, showed promising effectiveness in lowering plaque and gingivitis scores without harmful consequences.
Lotif et al., 2022 [79]	Double-blind randomized clinical trial	A total of 42 participants randomized into two groups based on dentifrice, recorded saliva, and microbiological analysis identified Lactobacillus spp. isolates, with VPI and CFU/mL values.	The toothpaste containing BRP demonstrated antimicrobial properties against Lactobacillus spp. and reduced the VPI for up to four weeks.
Leiva-Cala et al., 2020 [80]	Randomized clinical trial	A study involving 140 patients aged 12 and older with permanent teeth found that 43.6% of transactions were TOUs. In the CHX arm, 81.4% of patients experienced TOUs, while 5.7% of patients treated with aloe vera gel did not suffer from TOUs.	Administration of aloe vera gel may be essential in shielding patients with permanent orthodontic equipment from traumatic mouth ulcers.
Santamaria et al., 2014 [81]	Comparative Study	A study of 34 volunteers, divided into two groups, monitored their dental hygiene for four weeks. They were given different treatments for plaque index and bacteria count, and after 15 days, they were instructed to return to their usual habits. The data was analyzed statistically with a 5% significance level.	The use of natural products such as melaleuca could be a solution for controlling dental biofilm, especially in orthodontic patients.
Masoud et al., 2015 [82]	Comparative Study	Considered xylitol as a possible natural product for reducing dental plaque, suggests xylitol may not offer significant benefit.	Xylitol may not offer a significant benefit, but it still had no adverse effects.
Goes et al., (2016) [83]	Pilot Study	The study compared the effects of mouthwash with 1% Matricaria chamomilla, with a mouthwash with 0.12% CHX (chlorhexidine) (considered the gold standard).	It was found that both VPI (visible plaque index) and GBI (gingival plaque index) bleeding indexes significantly decreased with MTC at 1%, similar to the effects of CHX at 0.12%, in patients with gingivitis associated with orthodontic appliances.