This study is aiming in preventing the formation of WSL associated with orthodontic treatment which occurs to more than 50% of orthodontically treated patients through applying CPP-ACP on the enamel surface once every 2 weeks for 3 months.

CPP-ACP will be applied on premolars to be extracted in orthodontic patients whose treatment plan indicates extraction of at least 2 premolaes of the maxillary arch. Application will continue on one premolar either the right or left one once every 2 weeks for the first 3 months of the treatment.

Inclusion Criteria:

• severe crowding
• Increased overjet
• Protruded maxillary base
• Sound maxillary premolars
• medically free
• molar classification class II
• Canine classification class II

Exclusion Criteria:

• spacing of teeth
• Decreased overjet
• Molar classification III Medically compromised patients
• pregnant females
• carious premolars
• hypoplasia