The aim of the study is to evaluate the most efficient product for the cleaning of Invisalign® clear aligners (Align Technology Inc., San Jose, CA, USA) through objective and subjective assessments after the use of 5 different products. For each aligner, one product is used for 2 weeks until all of them are used, therefore 5 different aligners are required for the study. A periodontal evaluation is conducted to assess variations during the time frame of the study.

This randomized clinical trial aims to evaluate the efficacy of 5 different products for the cleansing of Invisalign® clear aligners among the followings:

1. drinking water;
2. dish soap Svelto (Unilever Italia Mkt operations S.r.l.; Roma, IT);
3. Polident Antibacterial Denture Cleaner (GlaxoSmithKline; Philadelphia, Pa, USA);
4. Cleaning Crystals Invisalign® (Align Technology, Inc.; San Jose, CA, USA);
5. Geldis (Kalipharm S.r.l., Alba, IT).

Patients that will sign the informed consent will be enrolled for the study; parents will sign the consent for underage patients.

2 week before the beginning of the orthodontic treatment with Invisalign clear aligners, a professional manual and mechanical removal of supragingival and subgingival deposits of both arches will be performed. At the baseline (T0), the first aligner will be delivered to the patient, that must wear it for 22/24 h except for meals and oral hygiene procedures. One of the 5 cleaning product will be randomly assigned to the patient and toothbrush with silicone bristles (Kalipharm S.r.l., Alba, IT) will be given the cleaning procedures. Patients will be asked to fill in a questionnaire for the subjective appreciation on the cleaning material: the questionnaire presents 19 items evaluating organoleptic and visual characteristics of the aligners and the ease of use of the cleaning method after the first use, after 1 and after 2 weeks. After 2 weeks (T1), patient will be visited again: the questionnaire will be collected, together with the aligner, and a periodontal evaluation on the Ramfjiord teeth will be performed using the following indices: Plaque Index (PI), Bleeding on Probing (BoP), Probing Pocket Depth (PPD), (Gingival Index), BEWE (Basic Erosive Wear Examination), Schiff Air Index. After that, another questionnaire and the following aligner will be given to the patient, another cleaning product will be randomly assigned and another toothbrush will be given. The procedure will be repeated for the following 2 (T2), 4 (T3), 6 (T4) and 8 weeks (T5) until all the cleaning products are tested. All the products will be masked.

JASCO V-750 spectrophotometer (Jasco Corporation, Tokyo, Japan) will be used to evaluate adsorbance for each aligner after the application of the cleaning products. A control value will be calculated using a new clean aligner. The spectrophotometer calculates reflectance values that will be converted in adsorbance values.

Sample size

Sample size was calculated with the following assumptions: ability to detect a clinically relevant difference of 0.0265 in the adsorbance of the clear aligner (primary outcome) of the five groups with an alfa = 0.05 and power = 80%. The assumptions were based on findings of a previous study, with an expected value of 0.190 and a standard deviation of 0.03 for the first group after 2 weeks. Therefore, 20 aligners per each cleaning method were required for the study.

Statistical analysis Statistical analysis will be conducted with R software (R version 3.1.3, R Development Core Team, R Foundation for Statistical Computing, Wien, Austria).

For each variable, Significance for all statistical tests will be predetermined at P<0.05.

Inclusion Criteria:

• Patients undergoing orthodontic treatment with Invisalign® clear aligners.

Exclusion Criteria:

• Failing to follow cleaning method instructions
• Failing to fill in the questionnaires

Data will be available upon motivated request to the Principal Investigator.