Dental caries is the destruction of the tooth structure in the presence of organic acids produced by cariogenic bacteria located in the dental biofilm (Dowker et al., 1999 and Robinson et al., 2000).Tooth enamel comprises 90% substituted hydroxyapatite (Ca10 (PO4)6(OH) 2), which is subjected to consecutive cycles of demineralization and remineralization. This is an interrupted process, with periods of remineralization and demineralization occurring, depending on the state of the oral environment in terms of the prolonged accumulation and retention of bacterial plaque on the enamel surface (Aoba, 2004).

Oral bacteria ferment carbohydrates to produce organic acids which lower the pH and cause the subsurface dissolution of the hydroxyapatite crystals. Under normal physiological conditions (pH7), saliva is supersaturated with calcium and phosphate ions which diffuse into the vacancies created during acid-mediated demineralization episodes (Dowker et al., 1999 and Robinson et al., 2000). The demineralization of enamel (white spot lesions) is a significant problem during and after orthodontic treatment with prevalence 71.1% and various preventive measures have been suggested to minimize the incidence (Derks et al., 2004 and Al Maaitah et al., 2011).

In orthodontic patients, demineralization usually takes place in the form of white or brown spots on the enamel around the brackets and can lead to cavitation (Al Maaitah et al., 2011). White spot lesions compromise esthetics and can be extremely difficult or even impossible to reverse.

Natural remineralization through saliva involving a mineral gain in the surface layer of white spot lesions has little improvement on the esthetic and structural properties of the deeper lesions (Karlinsey et al., 2009 and Cochrane et al., 2010). Management of white spot lesion should involve methods of both preventing demineralization and encourage the remineralization of existing lesions. In both of these processes, the efficacy of fluoride is well established. Fluoride increases the initial rate of remineralization of early enamel lesions. Consequently, it slows down the caries process and arresting the lesion. Fluoride varnish provides a protective coat over the tooth which adheres longer to the tooth surface (Demito et al., 2004 and Ten Cate et al., 2008).

Inclusion Criteria:

1. Age ranging 11-16 years.
2. Good general health.
3. Exhibiting at least 2 white spot lesion in buccal surface of their teeth.

Exclusion Criteria:

1. Chronic use of medication causing dry mouth.
2. Oral ulcer, ulcerous gingivitis, acute bronchial asthma.
3. History of allergic reaction to fluoride or other ingredients in varnish.
4. Refusal of the patient to participate in the trial.
5. Any previous treatment done for white spot lesion.