Preventive Effects of Silver Diamine Fluoride on Early Enamel Caries

Fixed orthodontic patients are at risk of developing dental caries. Topical application of fluoride varnish (FV) around the orthodontic brackets and using fluoridated mouth rinses have been suggested to prevent the formation of white spot lesions (WSLs) on enamel. Recent studies have shown that silver diamine fluoride (SDF) demonstrated better outcomes in dental caries prevention as compared to FV. However, the caries preventive effects of SDF application around the orthodontic brackets have not been established yet.

This study will be conducted to evaluate the effectiveness of SDF in preventing WSLs formation in patients undergoing fixed orthodontic treatment. This study will use a randomised-controlled double-blinded design with three parallel arms. Ninety-nine eligible participants will be recruited. Using their registration number, a random list of patients will be generated using computer software. Each patient will be assigned randomly to three groups: SDF, FV, or placebo. Digital photographs of upper anterior teeth (frontal view) will be taken as a baseline and repeated at every review appointment. The materials will be applied around the orthodontic bracket of upper incisors and canines every 6 months. The formation of WSLs around the bracket will be evaluated at 1, 3, 6, and 12 months using three parameters: the ICDAS scoring system, the laser fluorescence caries detector, and digital photographic analysis using the Gorelick score. The patients' perception of the colour changes of the enamel will be evaluated through patient-reported outcomes. The difference in ICDAS and Gorelick scores and the patients' perceptions will be reported through descriptive statistics. The Kruskal-Wallis or one-way ANOVA statistical test will be used to compare the changes in fluorescence intensity between treatment groups.

The investigators believe that the results of this study will provide insight into the caries preventive protocol among fixed orthodontics patients and subsequently reduce the incidence of WSLs during orthodontic treatment.

Fixed orthodontic appliances are commonly used to correct malocclusions and align teeth in orthodontic treatment. Fixed orthodontic appliances consist of several components, each serving a specific function in the orthodontic treatment process. These components typically include brackets, arch wires, ligatures (or ties), and occasionally auxiliary components such as springs or elastics. It involves the placement of orthodontic brackets, secured to the teeth surface with a composite resin material. Slots on the brackets are used to hold the orthodontic wires, which act as a means of transmitting forces to the teeth for their movement during orthodontic treatment.

The direct bonding of orthodontic devices to teeth has had a profound impact on orthodontic practices. In the early days of orthodontic treatment, brackets were attached to gold or stainless-steel bands. This process was time-consuming and uncomfortable for patients, often causing gingival trauma and decalcification. In the mid-1960s, researchers pioneered the bonding of brackets directly to enamel. Since then, there have been numerous advancements in adhesives, base designs, bracket materials, curing methods, primers, fluoride-releasing agents, and sealants. Nevertheless, the incidence and severity of white spot lesions caused by enamel decalcification are increasing among those receiving orthodontic treatment. Surprisingly, these lesions can appear as early as one month after the placement of orthodontic brackets. Prolonged treatment, lasting over a year, increases this risk due to the presence of fixed appliances, creating areas for plaque accumulation. This plaque may rapidly modify the composition of bacteria, particularly acid-producing bacteria, leading to enamel erosion and the formation of white spot lesions (WSLs).

White spot lesions are rapidly forming, prompting clinicians to explore solutions for orthodontic-associated demineralization. Factors such as food debris, diet, fluoride availability, mineral crystal composition, and salivary content can influence demineralization periods. Studies have shown that preventive strategies, such as application of topical fluorides, reduce the incidence of WSLs formation. A systematic review has demonstrated the effectiveness of topical sodium fluoride varnishes (FV) in preventing enamel decalcification during orthodontic treatment with fixed appliances. However, the reported preventive fraction is wide, ranging from 12 to 55%. This shows that the preventive effects of FV are not consistent and vary between individuals. The range of results seen may also be attributed to the bioavailability of fluoride in saliva, which is regulated by variables including salivary secretion rate, dietary fluoride consumption, and the usage of fluoridated products. While traditional fluorides like sodium fluoride support remineralization following topical application, they exhibit shorter persistence in saliva compared to SDF's 38% retention. This is due to the stable silver halide compound that forms in saliva, which helps sustain SDF over an extended period of time, and the high fluoride content of SDF, which renders it a great potential for remineralization. Further, the remineralisation and antibacterial effects of fluoride are slow and highly dependent on factors such as patients brushing efficacy and the stability of the fluoride ion in the saliva. This might explain why the WSLs are still occur and present around the orthodontic brackets even though the preventive measures have been implemented.

Recently, the use of silver diamine fluoride (SDF) has gained much attention in caries management strategy, especially on cavitated lesions. SDF was introduced into the dental field by Nishiino, Yamaga and their colleagues in the 1960s available at 38% concentration. SDF is a colourless and odorless solution which consists of silver, fluoride, and ammonia ion. The presence of the silver component in the SDF formulation helps in stimulating dentine sclerosis and provides antibacterial activity by causing immediate bacterial death through inhibition of bacterial DNA replication and blocking the formation of proteolytic enzymes. Fluoride on the other hand act as a remineralising agent and presents at a high concentration of 44,800 ppm.

The combined effects of remineralising and antibacterial properties make SDF an effective cariostatic agent. A systematic review showed that SDF effectively arrests decay in primary teeth in children, with a proportion of 66%-81% with annual or biannual application, while it was reported that the preventive fraction of SDF is as high as 61% and 72%, respectively. In comparison to fluoride varnish, SDF has a better caries arrest ability on both primary and permanent teeth, where the effectiveness is almost doubled than the effects of sodium fluoride varnish at 30 months.

The only drawback of SDF application is the formation of black staining on the cavitated lesion due to the formation of silver phosphate precipitate when hydroxyapatite crystals react with the SDF solution. However, the addition of potassium iodide managed to reduce the staining effects, leading to a yellow-brown rather than a black discoloration. In addition, SDF will not stain sound enamel suggesting its promising role in the prevention of dental caries.

However, based on our knowledge, the effects of SDF in preventing WSLs formation in patients with fixed orthodontics has not been established yet. Therefore, the investigators would like to take this opportunity and conduct a clinical trial with the aim to investigate the effectiveness of Silver Diamine Fluoride (SDF) in caries prevention among patients with fixed orthodontic appliances.

Eligibility Criteria:
Inclusion Criteria:

* Subjects about to undergo fixed orthodontic treatment at the Faculty of Dentistry, UKM.
* Subjects must be aged 18 years and above.
* Consented for treatment. Patients will be informed of the risk and benefit of the study for each treatment group through the patient information sheet given to them before obtaining their consent.
* Orthodontic brackets placed at least on the upper incisors.
* Patients undergoing orthodontic treatment with conventional orthodontic brackets placed on the labial surface.
* Any degree of malocclusion
* Fit and healthy patient
* Non-smoker
* Subjects can understand and possessed basic command in English

Exclusion Criteria:

* History of fixed orthodontic treatment
* Presence of any dental anomalies or developmental defects of enamel (DDE) on labial surfaces of teeth, such as preexisting fluorosis or enamel hypoplasia.
* Presence of any or direct/indirect restorations on the labial surface of teeth
* History of long-term antibiotic usage
* Presence of untreated cavitated lesions, especially on upper and lower incisors and canines
* Plaque levels \>30%.
* Patient allergic to any of the content of the intervention material (sodium fluoride, silver diamine fluoride, potassium iodide).
* Patients with lingual brackets.