Dental caries is a decay process that breaks down the tooth. The earliest clinical signs of active dental caries is seen as 'white spot lesions' (WSLs). WSLs causes porosity below the tooth surface as a result of demineralization that gives the lesion a milky white appearance.

Many WSLs persevere even a decade after orthodontic appliance removal and remain a cosmetic problem. After removal of fixed appliances, a considerable improvement of WSLs can be seen during the first 6-24 months, but the degree of improvement varies between individuals.

Two common bacteria in dental plaque causes caries: Streptococcus mutans (SM) and Lactobacillus acidophilus (LA) in the plaque contributes to the initiation and progression of caries, respectively.

A major strategy suggested to deal with existing WSL after debond is to facilitate remineralisation using remineralising agents that contain fluoride. This can be from daily use of fluoridated toothpastes or having additional dose of fluoride application. Certain agents also contain casein phosphopeptide-stabilize amorphous calcium phosphate (CPP-ACP) that is believed to have an antibacterial and buffering effect on plaque and interfere the growth and adherence of bacteria.

Rationale of the study :

Currently there is insufficient evidence on the most effective regime of fluoride application to regress post orthodontic WSLs and how it affects the quality and quantity of oral microbial flora.

The study aims to determine the effect of different remineralizing agents on white spot lesions and dental plaque of post-orthodontic treatment patients.

The objectives are:

1. To compare the tooth surface changes (based on ICDAS, optical changes and patient perception) of white spot lesion treated with different remineralizing agents during orthodontic retention
2. To compare the bacterial count (including streptococcus and lactobacillus) in subjects with white spot lesions treated with different remineralizing agents during orthodontic retention
3. To compare the salivary profile (flow rate, Ph, buffering capacity) in subjects with white spot lesion treated with different remineralizing agents during orthodontic retention

Sample size calculation :

Sample size was calculated using G-power. Given an effect size of 0.49 (Jung et al., 2014), 80% power of study, alpha of 5% and 7 measurements, the sample size required was 27. With a 10% dropout, the final sample size is 30.

Methodology :

A. Subjects screening and preparation

Orthodontic patients treated with at least fixed appliances on the maxillary arch at the Faculty of Dentistry, University of Malaya whom are scheduled for debond, are invited to participate in this study. Participants will be screened for white spot lesions based on the inclusion and exclusion criteria. Participants will be randomly allocated to 3 groups that will receive remineralizing applications according to their allocated groups:

Group 1 The participants in group 1 will act as control group as they will be advised in using fluoridated toothpaste to brush twice daily during the follow up periods. No other fluorides supplements will be allowed to use.

Group 2 The participants in this group will received fluoride varnish (5% sodium fluoride) treatment. The labial surface of each tooth will be polished with non-fluoridated pumice powder and will be rinsed and dried thoroughly. Approximately 0.5-1.0ml fluoride varnish will be applied on the tooth surface (labially) with the paint-on method from canines to canines. After varnish application, patients will be advised not to drink for at least 30 minutes and not to brush teeth or eat food for the next 4 hours after application. Participants can brush teeth the night after application. The participants will be advised to brush their teeth daily with fluoridated toothpaste. Fluoride varnish application will be on 3 months intervals from first review visit (T1). No other fluorides supplements will be allowed to use.

Group 3 The participants will be advised to use pea size CPP-ACP plus crème on the tooth surfaces using a clean fingers twice daily following brushing their teeth with fluoridated toothpaste. The participants will be taught to keep the CPP-ACP plus crème on the tooth surface for at least 3 minutes before rinsing the mouth. After application of CPP-ACP plus crème, participants will be advised not to drink or eat for at least 30 minutes. No other fluoride supplements will be allowed to use.

During the first appointment (T0),

1. Debond procedure will be done according to the standard protocol.
2. Two sets of impression will be taken for the construction of study model, construction of the standard retainers and also for the research purpose.
3. Participants will be screen for white spot lesion by using the Optical Coherence Tomography (Santec) . A jig will be constructed for reproducible positioning of the probe. Two maxillary teeth with the worst WSL will be selected for each patient to measure the lesion depth and integrated refractivity. The intraoral photos of the maxillary teeth will be taken.
4. The salivary profile (flow rate, Ph, buffering capacity) will be measured using Saliva- Check BUFFER (GC America) according to the manufacturer's instruction.
5. Plaque samples will be collected with sterile swabs from the enamel surface of each tooth with the identified WSL to measure the bacterial count.

1 day after T0,

1. Participants will receive pressure formed or thermoplastic retainer in upper arch and instructed to wear their retainers all day (for at least 8 hours) and wear them after toothbrushing.
2. ICDAS score and optical changes (lesion depth and integrated refractivity) of the white spot lesion will be measured.
3. Participants will be given a set of questionnaires to assess the compliance to the remineralizing agent application and perception on the WSL.

Treatment follow up

1. The participants will be coordinated for follow up after 3 months (T1), 6 months (T2), 9 months (T3), 12 months (T4), and 18 months (T5)

2. During the follow up visit , each participant will be subjected to the measurement of :

   • tooth surface changes
   • bacterial count
   • salivary profile
   • intraoral photos of maxillary teeth

3. Participants will be given a set of questionnaires at every follow up visit to assess the compliance to the application of remineralizing agent and perception of the WSLs

Statistical Analysis

Data analysis will be done using the SPSS version 22. Descriptive date will be expressed as mean ± standard deviation (SD) unless otherwise stated. Repeated measurement ANOVA will be used for analysis of normally distributed variables. Kruskal-Wallis ANOVA will be used for non-normally distributed data. A value of P < 0.05 is considered statistically significant. The data collected will be analyzed using an intention-to-treat basis.

Inclusion Criteria:

• Subjects on multibracket fixed appliance treatment
• Subjects with 2 or more bracketed surfaces with labial subsurface WSLs from
• upper right permanent canine (13) to upper left permanent canine (23) with an ICDAS II score of 1 and 2 will be selected.
• Indicated for thermoform or vacuum formed retainers on the upper arch.

Exclusion Criteria:

• Systemic diseases or any physical anomalies.
• Subjects with intention to move out from Klang Valley area for the next 1.5 years.
• Periodontal diseases (pocket depth of more than 3mm).
• Smoker.
• Severe fluorosis or any enamel abnormalities.
• Antimicrobial agents or antibiotic therapy within the past 3 months.
• Orthognathic surgery cases, cleft lip and palate.
• Single arched lower fixed orthodontic treatment.
• Milk protein and benzoate preservatives (a common preservatives) allergies.