The aim of this study is to evaluate the effectiveness of calcium fluoride nanoparticles containing orthodontic primer in preventing or decreasing the incidence WSLs over a period of 6 months in patients with fixed orthodontic appliances.

This study proposed to be double blinded, split mouth, randomized clinical trial, with equal randomization (1:1 allocation ratio).

The sample was selected and recruited from patients attending two centres (Orthodontic Department at Karbala Governmental Specialized Dental Center and Almina Dental Private Clinics/Karbala), but the bonding and follow up sessions were done in Almina Dental Private Clinics/Karbala. Patient recruitment was done according to specified inclusion and exclusion criteria.

Intervention procedure planned to be by bonding fixed orthodontic appliances to all patients. The four quadrants of the mouth will be divided into two groups (Group 1 and 2), with one group, the upper right and lower left quadrants bonded with nCaF2 resin, while the upper left and lower right quadrants bonded with control resin. For the other group, the reverse will be carried out. Then, by the use of a computer random number generator, the two groups will be randomly allocated, and each number in the random table will be given a study number in order to create the final Allocation Table for the participants in the study (which contained the study number and allocation group). the primary planned to be measured by DIAGNOdent Pen 2190 device to measure enamel demineralization objectively, while the secondary objective planned to be quantitative detection of Streptococcus mutans bacteria by using real-time PCR

Inclusion Criteria:

• Patients have

  1. Fully erupted permanent teeth (regardless the third molar),
  2. Indication to have orthodontic treatment without extraction
  3. Fair or good oral hygiene before or after oral hygiene instruction

Exclusion Criteria:

• Patients will be excluded if they had

  1. Previous orthodontic treatment or extractions
  2. Missing teeth
  3. Active enamel caries determined by clinical examination
  4. Patients with enamel hypoplasia, dental fluorosis or tetracycline pigmentation
  5. Labial restorations
  6. Severe periodontal diseases determined according to PDI index by Sigurd P. Ramfjord (Ramfjord, 1967)
  7. Craniofacial syndromes such as clefts
  8. Xerostomia determined from clinical history of the patient
  9. Severely rotated teeth (limiting the appearance of buccal surfaces)
  10. Heavy smokers determined by accounting the number of cigarettes per day and time to the first cigarette of the day (Heatherton et al., 1989) .

This study proposed to be double blinded (the patients, investigators and the outcome assessors)