Abstract
Orthodontic treatment is often mandatory to improve the patient’s health condition. However, the fixed appliance can create additional plaque retention areas, which can increase the risk of caries development. Clinically, one can observe various effects of fixed appliance treatment on caries prevalence. This study aims to analyze to what extent orthodontic therapy with fixed appliances is a risk factor for developing caries in pediatric and adult patients. The keywords used in the search strategy were as follows: (“caries” AND “caries risk” AND “caries experience” AND” “orthodontic treatment” OR “fixed appliance” “) and (“caries experience” AND “orthodontic treatment”).
From 808 potential articles, 15 were included in the review. In individuals undergoing fixed orthodontic therapy, several factors can increase the risk of caries during fixed orthodontic treatment, such as salivary composition, oral dysbiosis and plaque accumulation. On the other hand, factors that reduce caries risk are, i.e., oral hygiene self-awareness and previous orthodontic treatment. In most studies which used the Decayed, Missing, and Filled Teeth (DMFT) index, there were no significant differences between the values obtained before orthodontic treatment and after the treatment. Moreover, it is easier for a patient with aligned teeth to remove plaque.
In the young population, fixed orthodontic treatment appears to reduce the incidence of caries. In the adult population, fixed orthodontic treatment increases the risk of dental caries. However, education on proper oral hygiene during orthodontic treatment can reduce the risk of dental caries. The study protocol was registered in the PROSPERO database (PROSPERO CRD42022356628).
Key words: risk factor, prophylaxis, orthodontics, caries, fixed appliances
Introduction
Caries is a multifactorial disease affecting the tooth’s hard tissues, resulting from the demineralization of enamel and dentin. Even today, it is one of the most common diseases, especially in the pediatric population.1 In addition to the well-known factors that can affect the promotion of demineralization of the tooth’s hard tissues, such as the presence of bacteria,2 the presence of a substrate for bacterial metabolism (carbohydrates),3 host susceptibility,3, 4 and time,2, 3 many patients undertake orthodontic treatment, especially to resolve functional and/or cosmetic problems, which can cause psychosocial distress and affect their quality of life and self-esteem.5, 6 Therefore, orthodontic treatment is often mandatory to improve the patient’s health condition. However, fixed appliances can create additional plaque retention areas, which can cause various spots of demineralization around the bracket.7 Initially, the carious lesion is reversible, without loss of substance, devoid of painful symptomatology, and presents clinically on the enamel as a chalky-white area of decalcification called a white spot. Although it is a non-cavitated lesion, if not diagnosed and treated with an appropriate prevention plan, it can further progress and turn into an irreversible cavitated lesion, which requires invasive treatment.8 Clinically, one can observe various effects of fixed appliance treatment on the prevalence of caries. The factors that may influence the occurrence and progression of caries are: patient’s hygiene and dietary habits, patient’s cooperation with both the orthodontist and dental hygienist, and self-awareness.9 Therefore, an interesting question arises: How does orthodontic treatment affects the prevalence of caries?
Objectives
This study aims to analyze to what extent orthodontic therapy with fixed appliances is a risk factor for developing caries in growing and adult patients.
Materials and methods
Search strategy
The study protocol was registered after the screening phase in the PROSPERO database (PROSPERO CRD42022356628). The review process was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) statement10, 11 and PRISMA reporting guidelines.10, 11 Literature searches of free text and MeSH terms were conducted using MEDLINE (PubMed) and Google Scholar (2000 to 2022). All searches were conducted using a combination of thematic titles and accessible text terms. The final search strategy was determined through several pre-selections. The keywords used in the search strategy were as follows: (“caries” AND “caries risk” AND “caries experience” AND” “orthodontic treatment” OR “fixed appliance” “) and (“caries experience” AND “orthodontic treatment”). The search string presented here refers to the MEDLINE (PubMed) search engine. The search strings associated with the search engines used in this systematic review are shown in Figure 1. The PICO (Problem/Population, Intervention, Comparison, Outcome) question was: How does orthodontic treatment with fixed appliances influence the risk of caries?12
Inclusion criteria
The following inclusion criteria were applied for this systematic review: clinical studies on growing and adult subjects with fixed orthodontic therapy. The following were the exclusion criteria: 1) in vitro studies, 2) animal studies, 3) randomized clinical trials (RCTs), and 4) case-control studies. There was no language restriction applied.
Data extraction
After retrieving the results from the search engines to create a database, the duplicates were removed. Literature was selected following the inclusion criteria by reading the titles and abstracts by 2 authors (SP and MM). The full text of each identified article was then read to determine if it was suitable for inclusion. Whenever a disagreement occurred, it was resolved by the study supervisor (AN). Data were sought regarding the changes in care experience before and after therapy with fixed orthodontic appliances. The authors extracted the values regarding caries severity and dental hygiene from the papers included to find the ones that were used in most of the studies and thus could be compared. The Cohen’s K coefficient for the agreement between the authors in study selections indicates a high agreement between the authors, as it was equal to 0.98. Authorship, year of publication, type of each eligible study, and the main results regarding the caries occurrence were extracted by one author (SP) and examined by another author (MM). The data sought were different oral hygiene and caries prevalence indices which reflect changes that would promote the development of caries.
Quality assessment
According to the PRISMA statement,11 the assessment of methodological quality indicates the strength of the evidence provided by the study, as methodological flaws can cause bias. The Newcastle-Ottawa Scale (NOS) has been used for quality assessments of cohort, case-control, and cross-sectional studies. Each study type has its own, specific criteria. This scale has 7 items and a maximum of 10 stars in cases involving cross-sectional studies, and 9 in cases involving cohort studies can be distributed. In the cohort studies spreadsheet, the quality of the selection of groups under study (4 questions), comparability of the groups (1 question) and outcomes of interest (2 questions) are assessed. Up to 5 stars can be given to the selection section, a maximum of 2 for comparability, and 3 stars for the outcome of interest section.13 In the cross-sectional studies spreadsheet, there are 3 main categories: selection (5 questions and 5 stars maximum), comparability (1 question and 2 stars maximum) and outcome (2 questions and 3 stars maximum).14 The Jadad scale was used to assess the quality of RCTs. There are 5 questions, and the first 3 are characterized by a binary response (yes = 1 point; no = 0 points), and cover details on the randomization of subjects, description of patients and operator blinding, and description of the proportion of subjects lost to follow-up. One point will be subtracted or added from the total of the first 3 questions for each of these questions on the appropriateness of randomization and double-blinding. This procedure provides a total score ranging from 0 to 5, where 0 indicates a low-quality study and 5 indicates the highest possible quality. A study is considered good quality when it scores at least 3.15
Results
Search results
A systematic literature review was conducted for studies published from 2010 to 2022. The search strategy identified 808 potential articles from PubMed and Google Scholar. After the removal of duplicates, 538 articles were analyzed.
Afterward, 201 articles were excluded because they were not relevant to the topic, author debates, lack of effective statistical analysis, case reports, incomplete studies, reviews, and in vitro studies. Of the remaining 337 articles, 322 were excluded because they were not relevant to the full-text analysis. The remaining 15 articles were included in the review, and are represented in Table 1. Figure 1 presents the search strategy and the final number of studies included.
Extracted data
The data extracted from the included articles are presented as follows: authors, year, location, study setting, number of subjects studied, duration of therapy, and indices used. Table 1 presents the summary of data provided from the included studies.
The included studies were published between 2010 and 2022 and were conducted in North America (n = 2), South America (n = 1), Asia (n = 7), Europe (n = 4), and Australia and Oceania (n = 1). Thirteen studies were conducted at universities, 3 in hospitals (1 both at a university and in a hospital), and 1 of them was partially conducted in private practice.
The total number of subjects examined was 23,943, with an average of 1,596 subjects per study. The total number of growing subjects was a clear minority of the total, n = 1,633 (6.8%). The total number of adult subjects was 22,310 (93.2%). The average age of the total number of subjects examined was 20.15. The average age of growing subjects was 13.37, while the average age of adult subjects was 33.7. The average duration of orthodontic therapy was approx. 23 months.
The indices used to detect caries were Decayed Teeth (DT), Filled Teeth (FT), Decayed Surfaces (DS), Filled Surfaces (FS), Decayed and Filled Teeth (DFT), Nyvad, Decayed, Missing and Filled Teeth (DMFT), Decayed and Filled Surfaces (DFS), Decayed, Missing and Filled Surfaces (DMFS), and White Spot Lesions (WSL) indices. In addition, periodontal indices such as gingival index (GI) and plaque index (PI) were also used. The main outcomes included in studies were mean DMFT in growing subjects before therapy, mean DMFT in growing subjects after therapy, mean DMFT in adult participants before therapy, and mean DMFT in adult subjects after therapy. In summary, the DMFT index was used on a total of 13,503 patients and in a total of 15 studies.
No specific information was provided regarding the type of brackets used, except for in the study conducted by Sanpei et al.30
Quality assessment
The evaluation of the RCT with the use of the Jadad scale is presented in Table 2. Moreover, the cohort and cross-sectional studies were evaluated with the use of the corresponding type of NOS, as presented in Table 3, Table 4.
From the conducted risk of bias assessment, it could be stated that a RCT is of low quality, while 4 cohort studies are of high quality and 4 others of medium quality. All cross-sectional studies are of high quality.
Discussion
Influence of fixed orthodontic therapy on the prevalence of caries
This systematic review sought to comprehensively show the available evidence on caries risk during fixed orthodontic therapy in the growing and adult population.
In growing patients undergoing fixed orthodontic treatment, Cardoso et al.17 showed that salivary composition plays an essential role in the development of active carious lesions, and with proper composition monitoring, it is possible to accurately assess the risk of caries development. Moreover, results from the by Morgenstern et al.24 showed that fixed orthodontic appliances could lead to dysbiosis, and those alterations in the oral microbiome are correlated with the development of caries. This relates directly to the results of the research by Lucchese et al.27 and Tufekci et al.29 Both of them found that fixed orthodontic appliances are a risk factor for plaque accumulation and the development of white spots. Both studies also proved that white spot lesions form primarily at the beginning of treatment (in the first 6 months), and their formation rate significantly decreases after this time. The distribution of white spot lesions is not equal, and a small percentage of patients in the study groups suffered from a large number of them on many teeth.
The study conducted by Enerbäck et al.22 shows that the risk of caries during orthodontic treatment is significantly increased due to the increased number of cariogenic bacteria. However, the regular use of toothpaste with a high fluoride content (5000 ppm F) or a mouth rinse containing 0.2% NaF together with standard toothpaste (1450 ppm) on a daily basis significantly reduces the risk of caries development. What is more, a study by Zabokova-Bilbilova et al.19 found that the introduction of professional fluoride-containing prophylaxis, as the only additional fluoride agent besides standard toothbrushing, did not cause a significant protective effect in subjected patients. Thus, professional application of fluoride, during follow-up visits only, does not protect the patient from lesion formation.
Another important factor is the type of orthodontic equipment applied by the clinician. Elastic ligatures showed a significantly lower susceptibility to plaque adhesion, in comparison to the stainless steel in the metallic ligatures.31 Elastic ligatures, on the other hand, occupy more space around the bracket, therefore requiring the patient to cooperate reasonably and not avoid follow-up visits. For this reason, in a number of studies, greater amounts of microorganisms are found in patients with elastic ligatures than in those who have arches fixed with metal ligatures.32 Therefore, it can be deduced that the type of ligature applied should be appropriately selected for patients according to their compliance. In addition, it is important to note that an orthodontic band would hold bacterial plaque more quickly than a bracket, which should also be taken into account when planning the placement of the appliance.33
Phenomena observed in growing patients
The clinical outcomes of the experience of caries in the growing patient are not unequivocal; in fact, Chen and Zhou26 observed a decrease in interproximal caries in patients undergoing fixed orthodontic treatment. However, Sanpei et al.30 did not find a significant change in DMFT during the treatment, but an accumulation of lactobacilli, which is considered a risk factor for caries. In both cases, there was a lack of analysis of potential confounding factors, such as the degree of crowding prior to orthodontic fixed treatment, or subjective factors, such as individual caries risk assessment on a genetic and exposomal basis. Therefore, it is not possible to draw a definitive conclusion on the relationship between fixed appliances and variation in caries experience in growing patients.
Phenomena observed in adult patients
In the study carried out by Choi,18 it was shown that orthodontic treatment is considered a risk factor for dental caries since fixed orthodontic appliances increase the surface area on which plaque can adhere. Moreover, the irregular shape of the brackets makes it almost impossible to remove the plaque altogether. Thus, oral hygiene education during orthodontic treatment is vital to reduce the risk of caries. According to Doğramacı et al.,21 orthodontic treatment is not considered a risk factor for dental caries in the long term. Furthermore, a relationship between DMFT and orthodontic treatment has not been found. The study by Alsulaiman and Brennann16 found that patients who have already undergone orthodontic treatment have better hygiene habits, which reduces the risk of caries. What is more, it is easier to remove plaque with properly aligned teeth.
Limitations
From the risk of bias assessment, it can be stated that the results from the studies included are more than likely to translate into actual clinical conditions. The limitation of this study is the fact that there was a limited number of RCTs and time restriction for article search. The other problem is the fact that factors that appear to be most important – patient cooperation and hygiene – are purely behavioral. Therefore, it should be underlined that the patients included in this study may behave differently than the ones clinicians are cooperating with on an everyday basis.
Summary
The studies included convey a distinct message. In most studies in which DMFT was used to assess caries risk, there were no significant differences between the value obtained before orthodontic treatment and the post-treatment value. Although orthodontic therapy with fixed appliances is commonly associated with the incidence of caries, the crucial factor is proper dental hygiene, which, when adequately maintained by the patient, can exclude the formation of any carious lesions during that time. Doctors and hygienists must constantly support, remind, and encourage proper hygiene practices so that the patient gets through the orthodontic treatment unaffected. From the recent study on the hygiene status of patients undergoing orthodontic treatment, it is known that this applies to all kinds of orthodontic therapy and removable appliances, e.g., aligners.34
Conclusions
Based on the results of this systematic review, it can be concluded that several factors can increase the risk of caries during fixed orthodontic treatment, such as salivary composition, oral dysbiosis and plaque accumulation. It was not possible to establish a direct correlation between the fixed multi-bracket appliance and caries experience in the developmental patient, whereas this is confirmed in the adult patient. Therefore, both age groups need to be addressed to reduce the causative factors of caries risk during treatment, with the benefit of making patients more aware of the importance of biofilm removal, even after the conclusion of fixed therapy.
Data availability
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Consent for publication
Not applicable.
