For our sample size estimation we used a standard deviation of 20 (taking into consideration several previous studies of other investigators), an effect size of 15, a significance level of 0.05, and a power of 0.8. It indicates the need for 58 subjects in total. Based on this, our goal is to include 80 subjects in anticipation of possible drop-outs. Patients will be randomly assigned to one of two groups: a chewing gum group and a control mouthwash group. Study kits will be numbered according to a random number table. Forty kits will contain instructions and supplies for the chewing gum group and forty will contain instructions and supplies for the control group. Assignment is done immediately after orthodontic appliances are placed. Operators will be blinded to the group assignment as it is done by a separate investigator. This investigator will administer to the patients the consent forms and give them instructions according to their group assignment. The investigator will give the participants a pre- randomized study kit containing a VAS booklet and either enough servings of chewing gum and a container of mouthwash or a container of mouthwash only with corresponding verbal and written instructions.