Dental caries and gingivitis are classified by the World Health Organization (WHO) as an important public health problem due to their high prevalence and incidence worldwide despite the development of public policies to combat them. They are chronic diseases that have a severe impact in terms of pain and suffering, impairment of function and effect on quality of life. During orthodontic treatments, the most common adverse event is the appearance of dental caries lesions and gingivitis due to increased retention and change of dental biofilm composition or difficulty of removal with conventional oral hygiene techniques. Efforts to implement various conventional preventive interventions of self-care and education have not decreased their incidence, so it is necessary to implement motivational interventions to help adolescents and young adults to make positive changes in their oral health habits, which are constant and lasting and prevent and control gingivitis and caries.

Dental caries and gingivitis are multifactorial diseases, however the only necessary factor, although insufficient for their development, is bacterial biofilm; brackets significantly increase its retention and limit self- cleaning mechanisms, representing a challenge in clinical practice. Motivational interventions in oral health could be an alternative to generate behavioral changes in oral health and daily self-care routines that are more sustainable over time compared to conventional education models in patients with fixed orthodontic appliances. A randomized controlled clinical trial open to subjects and single-blinded (investigators) of parallel groups is proposed for the evaluation of the effect of motivational interviewing combined with conventional oral health education (OHEc) versus OHEc, in the prevention of dental caries lesions and gingivitis. A sample size of 94 patients in total is proposed, distributed 47 in each arm of the study, with a follow-up of the cohort for six months. The baseline risk will be established before the placement of fixed appliances (T0), and a follow-up will be carried out during six months, with assessments in one (T1), three(T2) and six months (T3) after cementation, where the presence of gingivitis, caries and changes in risk variables, adverse events and adherence to conventional and motivational interventions, will be measured.

Inclusion Criteria:

• Patients enrolled in the different orthodontic postgraduate clinics of the National University of Colombia who requires treatment with fixed orthodontic appliances
• 13 years old up to 28 years of age.
• Willingness to participate in the study and signature of the informed consent form.

Exclusion Criteria:

• Patients with untreated caries lesions
• Patients with periodontal diseases or experience
• Previous orthodontics treatments
• Severe fluorosis or enamel abnormalities.
• Medical compromise or treatments generating hyposalivation or gingival enlargement
• Craniomaxillary anomalies
• Cognitive or motor disability
• Pregnancy.
• Dependence to alcohol, nicotine or psychoactive substances

The randomization tool of the RedCap (Research Electronic Data Capture) platform will be used. The randomizing will be performed by an independent investigator who has no contact or access to the information of the subjects, ensuring that the allocation will be blinded for the rest of the investigators. The patient will know the assigned group when he or she is scheduled to the motivational intervention, thus the study will be open to the subjects.

The investigator who performs motivational and usual intervention is not blinded because once the patient is summoned for the application of motivational intervention, he/she will know the assigned group. Investigators who perform clinical measurements and indexes will remain blinded throughout the study by means of restricted access to the randomization instrument and general data recording of the study. The statistical data evaluator will be unaware of the allocation of the interventions.