This randomized clinical trial and laboratory study was conducted to:

Compare the effectiveness of zinc-carbonated nano-hydroxyapatite, arginine, and fluoride-containing toothpastes for treating white spot lesions associated with orthodontically treated teeth by using:

• Computerized image software analysis.
• Energy dispersive X-ray analysis.

White spot lesions (WSLs), defined as "white opacity," occur as a result of subsurface enamel demineralization that is located on smooth surfaces of teeth. The reason for the white appearance is the changes in light-scattering optical properties of the decalcified enamel. The aim of the current study is to compare the effectiveness of zinc-carbonated nano-hydroxyapatite, arginine, and fluoride-containing toothpastes for treating white spot lesions.

A) Primary Objective

Assessment of:

size and color change measurements of the WSLs through digital photography and computerized image software analysis.

B) Secondary Objectives

Assessment of:

• Degree of remineralization using Energy dispersive X-ray analysis

PICOTS:

• P - Participants: patients in the age group of 12-18 years having post orthodontic white spot lesions (WSLs).

I - Intervention:

• zinc-carbonated nano-hydroxyapatite-containing toothpaste.
• 8% arginine and calcium carbonate-containing toothpaste (Pro-Argin technology)

C- Comparison:

fluoride-containing toothpaste.

O -Outcomes:

• Reduction in WSLs size and color improvement
• remineralization of WSLs by regaining Ca and P ions.

T- Time: study period will be over 6 months.

S- Study design: Randomized Controlled Trial (RCT) and in vitro study

This study will consist of two parts: in vivo part (Randomized Controlled Trial) and in vitro part:

In vivo part:

• Study design: Randomized controlled trial (RCT)
• Grouping:

Patients will be randomly allocated into one of the three groups (7/each):

Group 1: zinc-carbonated nano-hydroxyapatite containing toothpaste (study group) Group 2: 8% arginine and calcium carbonate (Pro-Argin) containing toothpaste (study group) Group 3: fluoride containing toothpaste (positive control group)

Materials used in the study:

1. zinc-carbonated nano-hydroxyapatite containing toothpaste.

2. 8% arginine and calcium carbonate (Pro-Argin) containing toothpaste

3. fluoride containing toothpaste

   - Clinical procedures:

All interventions will be performed by the primary investigator as follows:

The dental plaque deposit will to be removed before the assessment. Dental prophylaxis will be performed with a bristle brush and non-fluoridated prophylactic paste during the initial clinical examination and before any examination.

photographic assessment by digital camera will be performed at 0 , 3 months, and 6 months throughout the study period for all the patients. During the photographic assessment, all the photographs will be taken under fixed conditions using a digital camera with lens equipped with external ring flash with 1:1 shooting power. the image quality will be set as RAW format, the shutter speed will set to 1/125 sec, F22 aperture value, auto white balance, and ISO 200. All images will be saved as Joint Photographic Experts Group (JPEG) files suitable for manipulation with the image analysis software.

At the baseline of the study, all participants will be provided with instructions to adhere to strict oral hygiene practices. These instructions included brushing their teeth twice a day using the allocated toothpaste and a soft-bristle toothbrush, employing the Bass Technique for a duration of 1 to 2 minutes.Participants will be instructed to spit out the excess toothpaste rather than rinse their mouths with water after brushing with toothpaste.

Patient's confidentiality will be respected through the photographic technique.

After digital images captured, they will be downloaded and stored as JPEG. Then the size of each WSL will be analyzed, and compared with baseline lesions by using Abode Photoshop and ImageJ analysis softwares.

The enamel color of each WSL will be measured using the Standardized CIE Lab* system (Commission International de l'Eclairage) within Adobe Photoshop software.

All measurements will be performed under standardized ambient conditions to ensure accuracy and reproducibility.

- Follow up

Patients will be recalled after 1, 3, and 6 months for clinical examinations and photographic assessments and oral hygiene instructions will be further provided.

- Outcome measurement:

Photographic assessment for size and color change reading outcomes will be assessed by one calibrated examiners at the following periods:

1) Baseline 2) 3-month evaluation 3) 6-month evaluation

Photographic assessment:

The following will be determined from photographs of all the patients in relation to WSLs:

• Size readings The area of the labial surface of the tooth WSL area The area of WSL to area of the labial surface of the tooth ratio percent (Percent of WSL) The percentage of decrease in WSL ratio due to time (Percent Decrease)
• Color change readings The values of L* (differences in lightness ranging from O (black) to 100 (white)), a* (green-red coordinate), and b* (blue yellow coordinate) will be recorded for the WSL and the adjacent sound enamel.

Color change will be calculated as the color difference between the treated and untreated enamel, as well as the color difference between the WSL at baseline and at the different follow-up intervals.

- Degree of WSL masking after the treatment will be measured.

14 image will be re-examined after 1 weeks for intra-examiner reliability

in-vitro part: experimental study where a total of 36 sound premolars will be randomly allocated according to the assigned toothpaste into four groups: G1: zinc-carbonated nano-hydroxyapatite; G2: arginine; G3: positive control (fluoride toothpaste); and G4: negative control (artificial saliva). A scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis will be conducted at the baseline to assess the calcium (Ca) and phosphorus (P) content. Following the induction of white spot lesions, a pH cycle will be implemented, involving a 7-day application of the toothpastes. Readings will be taken both after demineralization and subsequent remineralization phases.

Inclusion Criteria:

• Completion of fixed appliance therapy within the past 1 week.
• Presence of at least one post-orthodontic white spot lesion on the labial surfaces of the six maxillary anterior teeth with a score of 1 or 2 on International Caries Detection and Assessment System (ICDAS II).

Exclusion Criteria:

• Previous or planned treatment of WSLs.
• Cavitated enamel surface.
• Teeth with any composite restorations, veneers, crowns.
• Surface defects (developmental defects, fluorosis, intrinsic and extrinsic discolorations, etc.).
• Smoking habits.

The toothpastes are sourced from international markets, and both the participants and the outcome assessor will remain unaware of the active remineralizing agent in the toothpaste. This ensures that neither the participants nor the outcome assessor will be informed about the assigned intervention, preventing their expectations from influencing the study results.

The examiner was blinded to participants' codes and previous WSL scores during dental assessments. However, blinding to the type of toothpaste used was not possible. Blinding during image analysis was also unfeasible, but this limitation was deemed manageable since the outcome relied on objective computer-based data, minimizing potential bias