Dental cavities are among the most frequent diseases that affect teeth, particularly in patients who are treated with braces due to the difficulty in maintaining good oral hygiene in the presence of the mouth appliances. The white spot lesion (WSL) is the first clinical sign of cavities that presents itself as a milky-white opacity when located on the front face of the tooth. The aim to manage these early lesions focuses on promoting natural remineralization and preventing further demineralization. Various materials have been introduced for management of WSLs including MI paste and MI paste combined with fluoride (MI paste plus). Recently, a new material called resin infiltration has been found to treat these lesions with high esthetic results and great performance. According to the few numbers of in-vivo studies investigating the effectiveness of remineralization products, the aim of the current study is to clinically compare the outcome of the resin-infiltration and etching + MI paste plus to stop and improve the appearance of the WSL on front teeth in patients after treatment with braces.

White spot lesion (WSL) is the first clinical sign of enamel caries that presents itself as a milky-white opacity non-cavitated when located on smooth surfaces. These surfaces are rougher than sound enamel, and they can be arrested or progressed. WSLs are more commonly seen on the outer surface of teeth after orthodontics treatment. Causing unaesthetic appearance on the anterior teeth and increasing chance of dental caries progression.

Different interventions have been introduced to manage WSL as preventing demineralization and biofilm formation, and promoting remineralization with fluoride varnish, casein phosphopeptides-amorphous calcium phosphate (CPP-ACP)- a nano-complex derived from milk casein that significantly increases salivary calcium and phosphate levels9 .

The remineralization of enamel subsurface lesions by CPP-ACP has been demonstrated in several in vitro studies. The potential of CPP-ACP to prevent enamel demineralization and promote lesion remineralization has also been successfully demonstrated in human in situ models. In the presence of fluoride, CPP-ACP has been shown to promote the formation of fluorapatite-like minerals deep in the subsurface lesion. Clinical studies evaluating the effect of CPP-ACP/ACFP on WSLs after debonding report significant regression of WSL numbers, size, and activity in comparison to fluoride or substances without fluoride. Consequently, CPP-ACP has been incorporated into minimally invasive products for the remineralization of WSLs. Nevertheless, other studies state significant change showing improvements in WSLs with remineralization products but no superiority of CPP-ACP .

Multiple studies have tested the efficacy of CPP-ACP on post-orthodontic WSLs but only a limited number of prospective clinical studies have examined the effect of CPP-ACP and fluoride + etch on WSLs developed during orthodontic treatment. It is during therapy with fixed appliances that patients are most susceptible to forming WSLs and WSLs are most active. Recently, treatment with resin infiltration has been developed by the dentistry equipe at Charité University of Berlin, Germany and was first proposed to halt the interproximal early stage non-cavitated caries lesions. It represents a new concept in dentistry that offers valuable clinical applicability for clinicians and high acceptance by patients and is an alternative method to treat early caries lesions that are not expected to remineralize or arrest by non-invasive measures when the infiltration is performed with low-viscosity light-curing resins.

The refractive index (RI) of enamel lesions is effective in arresting and stabilizing the progress of WSLs. Paris et al noted that lesions infiltrated by resin infiltration took on the appearance of the surrounding sound enamel masking the whitish appearance by filling the lesion's body with resin, which results in a rise of the refractive index (RI) of the lesion from 1-1. to 1.42-1.44 with resin infiltration, which is closer to a healthy enamel (1.62-1.63). Thus, a restoration with enamel-like optical characteristics is obtained. This technique is considered micro-invasive and may bridge the gap between the non-invasive and minimally invasive treatment of WSLs, postponing the need for a restoration as long as possible.

According to few in-vivo studies investigating the effectiveness of remineralization products to address the appearance of WSLs after orthodontic treatment.

The aim of the current study is to assess clinically the change in the WSL appearance of the maxillary incisors in patients treated with resin-infiltration + etch compared with patients treated with CPP-ACFP plus +etch .

Hypothesis: No significant difference will be expected between CPP-ACFP +etch (MI paste plus + etch) and resin infiltration etch in terms of improving the WSL however, the esthetic outcome of resin infiltration + etch will be significantly greater compared to MI paste plus + etch.

Justification: Few studies have evaluated in vivo the WSL change satisfaction of resin infiltration compared to CPP-ACP and fluoride + etch after orthodontic treatment for more than a year for follow ups. In-vitro and in-vivo studies have shown a change in WSLs as a result of the topical use of these materials. However, further studies are needed to prove their role in calcium-based remineralization systems.

Objectives:

Determine the effect of resin infiltration and CPP-ACP in the caries process Determine the effect of resin infiltration and CPP-ACP in incisors aesthetics

Methods:

In this clinical randomized controlled trial study, sixty two subjects in the age range of 12-21 years having at least one post-orthodontic WSL on the upper or lower incisors will be randomly assigned to two groups of 31 samples in each. Participants will be recruited from patients who underwent labial fixed orthodontic treatment with (bracket properties), bonded with light-cured composite resin adhesive (Transbond XT, 3M Unitek, U.S.A) in the Department of Orthodontics, Dental School, University of Alberta. The study period will be from March 2023 and so on with prior approval from IRB (HERB). Informed consents will be obtained from parents/caregivers of the children after explaining the details of the treatment procedure in a designated format in regional and English languages.

Justification of the sample size :

Using results from Baffif et al. (2020), sample size is estimated based on the effect size demonstrated from ICON as compared at the 6 month level is a mean difference of 0.8 with a standard deviation of 1.3. Assuming power of 0.8 and alpha of 0.05, the required sample size is 31 per group.The selected samples will be randomly allocated to two groups according to treatment received.

Group I- Resin infiltration -Icon + etch, DMG, Germany, (n=31). Group II- MI paste plus +etch , GC corporation, Germany, Europe, (n=31). Before the application of topical agents on white spot lesions, oral prophylaxis will be carried out and the affected tooth to be treated will be cleaned with a rubber cup with prophylaxis paste (3M, Clinpro, United States of America) in both groups.

Information in regards to the length of orthodontic treatment, date of removal of orthodontic appliances, and oral hygiene status during treatment will be collected from the patients' charts. Patients will randomly receive an 8-week regimen of MI paste plus or resin infiltration. Patients will be followed up at 3,6, 12 and 18 months to evaluate change in appearance of the lesion of both treatments.

Plan for Data Analysis:

Remineralization will be assessed by the enamel decalcification index score (EDI) and International caries detection and assessment system (ICDAS) to evaluate the WSLs change after treatment with the two remineralizing agents. Furthermore, the satisfaction evaluation of the lesion will be assessed by a Visual Analog Scale (VAS) from 0 mm no change to 100 mm WSL completely changed/disappeared. The assessment will be done with photographs. Intraoral frontal views will be taken digitally. These photographs will be obtained at baseline (a few days after debonding to allow resolution of gingival inflammation that might mask WSLs), 3, 6,12 and 18 months after completion of orthodontic treatment. The patients will be asked to tilt up their head approximately 5-10 degrees to limit the flash reflection to the incisal third of the maxillary incisors. The optimal image will be selected among several photographs that will be taken at each time point. The first panel will consist of 3 dental experts (orthodontists and pediatric dentists) while the second panel will consist of three laypersons. Each examiner will perform the assessment independently.

Statistical analysis:

The collected data will be subjected to statistical analysis using SPSS version 22.0 (Armonk, NY, IBM Corp). Demographic variables will be analyzed using proportions. Independent sample 't' test will be used to compare the mean difference in esthetic appearance (VAS) and lesion.

Repeated Measures ANOVA will be used to determine the mean difference in VAS and EDI score, within study groups at various time intervals.

Expected results No significant difference will be expected between MI paste plus+etch and resin infiltration etch in terms of improving the WSL; however, the esthetic outcome of resin infiltration + etch will be significantly greater compared to MI paste plus + etch.

Study significance WSLs are prevalent lesions on the surface of teeth particularly, around the attached brackets, which lead to unaesthetic appearance of teeth after bracket removal and increase the chance of initiation of dental caries. Caries in the anterior teeth compromise the aesthetic enhancement achieved by orthodontic treatment. Thus, introducing a material that changes the WSL while providing the most similar appearance to the tooth enamel will be of great value.

Risks and Discomforts This technique has no risk or discomfort during the research, as both materials have been approved in Canada. Except that the application of CCP-ACP + fluoride may be difficult for some people as they need to use it at home. This material is contraindicated in patients with a proven or suspected milk protein allergy and/or with a sensitivity or allergy to benzoate preservatives. No side effects have been reported so far.

During the study visits, there may be an increased risk of COVID-19 exposure due to the added time spent within our health care facility and possible exposure to others. All AHS Infection Prevention and Control Practices in place during the pandemic (screening for COVID 19 symptoms prior to hospital entry, use of masks, hand sanitizer and physical distancing measure where possible) will also apply during these visits to reduce COVID- 19 risks.

There may be risks in this study that are currently not known. If the investigators find out anything new during the course of this research which may change participants' willingness to be in the study, the investigators will tell participants about these findings.

Inclusion Criteria:

• Individuals in the age range of 12-21 years who had undergone fixed orthodontic appliance therapy for a duration of 12-36 months.
• Should have at least one white spot lesion on the labial surface of either maxillary or mandibular anterior teeth after debonding. Lesion visible with or without drying the lesion surface.
• Patients with mild to moderate plaque accumulation. Fair oral hygiene. With a simplified Oral Hygiene Index of no more than 1.3-3.0

Exclusion Criteria:

• Poor oral hygiene Simplified Oral Hygiene Index of 3.1-6.0 or more
• Patients with hypoplasia or any developmental defects on the buccal of upper or lower incisors
• Patients with any restorations on the buccal of upper or lower incisors
• Patients that have presented WSL on the buccal of upper or lower incisors before orthodontic treatment was initiated.
• Patients that have received any re-mineralizing agent other than regular toothpaste during the last three months
• Patient with allergy to milk or any of their products
• Patient with any medical / oral or mental condition
• Patients or legal guardians that does not speak or read English

Double, Participant and Outcomes Assessor