Introduction

It is broadly believed that malocclusion hurts people’s physical, social, and psychological welfare [1, 2]. Patients ask for orthodontic treatment to enhance their appearance, oral function, psychosocial well-being, and quality of life, hence the major motivation for adult patients is mainly to improve their appearance. Current orthodontic appliances include fixed and removable orthodontic appliances. The primary elements of stable devices (brackets, band, ligature, and orthodontic wire) are capable to decrease the physiologic function of self-cleaning by the tongue or cheeks, also establish various plaque cumulation areas interfering with oral hygiene measures, and hence may lead to form white spot lesions, caries, gingival inflammation and/or periodontal diseases  [3]. Moreover, brackets may cause an unpleasant appearance, functional restrictions, and some discomforts. As the need for esthetic dentistry has enlarged in the last few decades, more patients are selecting invisible aligners, lingual brackets, and/or tooth-colored brackets over conventional ones [4]. On the other hand, the application of portable orthodontic appliances is capable to grant a sufficient oral hygiene measure so it can be easily removed for cleaning hence it decreases the risk for such adverse dental and periodontal complications in addition to more esthetic manifestation [5].

Periodontal diagnosis before orthodontic treatment is highly recommended as well as giving instructions to maintain good oral hygiene [6]. The significant key to periodontitis is the taxonomic composition of the microbiome while mutants streptococci are mainly significant in caries stimulation [7, 8]. S. mutans is a powerful acid producer and it is present in early carious lesions [9]. The biologic factors within saliva contribute to protecting the tooth from caries, includes salivary flow rate, antimicrobial activity, microorganism aggregation, and clearance from the oral cavity [10]. PH 6.7 is the average range of saliva but it ranges from 6.2-7.6 [11]. The evidence shows that the pathologically decreased salivary flow rate is regarded as a risk parameter for caries formation [12].

Many studies represent that conventional orthodontic appliances affect oral microbiota [13, 14].

Although various studies have evaluated the oral environment from different perspectives during orthodontic treatment using different protocols, for example, oral microorganism evaluation during active orthodontic phase using clear aligners, fixed appliances also, have assessed the nonmicrobial salivary parameters. However, there are deficient supporting literature in the form of systematic review nor meta-analysis combined all these factors in one study.

Hence, the goal of the present review is to consistently evaluate the literature and statistically summarize the found evidence evaluating the impact of thermoplastic clear aligners as well as fixed orthodontic appliances on oral microbiota and salivary parameters.

Materials and Methods

Search strategy and data sources

The review was registered with registration number FIRP/2020/66/252, and ethical approval has been obtained from the institutional review board IRP of Riyadh Elm (IRB) committee of Riyadh Elm University FIRP/2020/66/252/247.

Focused question

In orthodontic conventional fixed appliances and clear therapeutic aligners, were there a systematic change in oral microbial type and/or concentrations of salivary parameters among non-grower patients?

Data source

This systematic review was done according to PRISMA guideline [15]. and the Cochrane handbook [16]. A search was conducted in PubMed, Google Scholar, The Cochrane library, Saudi digital library, And Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS).

The following keywords were used “((salivary parameter) OR (oral microbiota)) AND (periodontopathic bacteria)) OR (cariogenic bacteria)) AND (fixed orthodontic appliances)) OR (clear aligner).” The search was limited to the last five years from 2015 until 24/6/2020.

Duplicates were removed and articles were screened initially by title and abstract.

Studies were done during the retentive phase for orthodontic patients; articles measured oral health by PI, GI, and PSR only, and the study was done for growing patients, and articles uncorrelated to the aim of the present organized review were excluded. The collected articles were individually strictly applied to clear inclusion and exclusion criteria as shown in Table 1. The procedure of article choosing is shown in Figure 1.

Articles were screened using the Problem, Intervention, Comparator, and Outcome (PICO) approach. Population/Problem was defined as non-grower patients’ orthodontic treatment needs. The intervention was defined as orthodontic treatment during the active phase. Comparator defined as two types of orthodontic appliances (Fixed appliances and clear aligner). The outcome was defined as oral microflora and salivary parameters.

Table 1. Eligibility Criteria

Quality synthesis

One particular reviewer (First Author) assessed the methodological quality of the studies after the final assessment of the full text (n=10) independently. Accordingly, 7 final articles were individually applied for qualitative and quantitative assessments. Quality assessment of the 7 final articles were appraised for risk of bias using a well-formulated quality assessment tool [15, 16]. Sampling bias was appraised by assessing and evaluating the sample selection, performance, detection of outcome assessors, attrition, and reporting. The overall assessment provided ranges from low to moderate risk of bias for the 7 articles; the main methodological points of these studies are summarized in (Table 2). 

Table 2. Risk of Bias Assessment

Criteria for judging the risk of bias in the ‘Risk of bias assessment tool – reproduced from The Cochrane Tool [16]. Criteria of judgment following low, high, or unclear risk was judge based on the following: 1- Random succession creation: election bias (prejudiced allocation to interventions) because of insufficient formation of a randomized succession. 2- Allotment hiding: election bias (biased allotment to interventions) as a result of insufficient hiding of allotments before assignment. 3-Blinding of participants and employees: function bias because of knowledge of the allotted interventions by participants and employees within the research. 4-Blinding of result evaluation: recognition of bias as a result of knowledge of the allotted interventions by result assessors. 5-Defected result data: attrition bias because of amount, nature, or handling of defected result data. 6-Elective reporting: reporting bias as a result of selective result reporting.

Results and Discussion

A total of 4636 were related to this topic. A total of 4626 were excluded by initial screening. There were 10 studies screened for eligibility criteria 7 of them included in qualitative synthesis, while 3 of them were excluded (Table 3).

Table 3. Summary of Excluded Studies

Overall, the bias risk for intended studies ranged from weak to high (Table 2).

Oral microbiota

6 studies evaluated oral microbiota for orthodontic patients during the active phase. Their results were summarized in Table 4.

Table 4. Summary of changing the oral microbiota during orthodontic treatment

Salivary parameters

There were two studies that evaluated salivary parameters for orthodontic patients during the active phase. Their result summarized in Table 5.

Table 5. Summary of salivary parameters assessment during orthodontic treatment