A cheek retractor will be placed to ensure consistent isolation throughout the procedure. Dehydration will be assessed at baseline, at the 5th minute, and at the 10th minute using three different evaluation techniques. At each time point, digital photographs will be captured under two distinct fluorescence light sources to document changes visually. In addition, fluorescence images will be obtained using the QLF (Quantitative Light-Induced Fluorescence) device to provide objective, quantitative data. All images will be recorded and analyzed digitally to evaluate dehydration-related changes in fluorescence. The aim of our study is to clinically evaluate the changes in the fluorescence properties of natural tooth following dehydration.

According to the power analysis, the required number of teeth was 69, with 95% statistical power and a 5% alpha error level. The study will be conducted at the Clinic of the Department of Restorative Dentistry, Marmara University Faculty of Dentistry. Individuals with caries-free teeth, no enamel defects, no restorations on tooth surfaces, no visible plaque, and adequate cognitive ability to read and understand the informed consent form will be included in the study. Those with teeth exhibiting discoloration or with systemic conditions or medication use that may cause structural changes on the tooth surfaces will be excluded. Maxillary and mandibular anterior teeth will be evaluated.

A cheek retractor will be placed in the patients' mouths, and baseline, 5th-minute, and 10th-minute dehydration will be evaluated using three different techniques. Digital photographs will be taken at baseline and post-procedure under two different fluorescence light sources (Ashur plaque indicator (405 nm), and Led lights (365 nm)), and the images obtained using the QLF (Quantitative Light-Induced Fluorescence- 405 nm) device will be recorded. Analyses will be carried out digitally. Images will be captured with a Sony Alpha 7iii (Sony, Japan) digital camera equipped with a 90-mm macro lens. Camera settings will be adjusted for the LED lights (1/125, f/22, ISO 8000) and for the Ashur device (1/125, f/22, ISO 25600). To ensure standardization, the LED lights will be stabilized on the flash brackets at a 45° angle on both sides, and all images will be captured in a dark room. QLF images will be obtained with its own camera. The photographs and the QLF images will be analyzed using Adobe Photoshop software, and color changes will be determined based on ∆E values. For each method ∆E values will be calculated individually, there will be 3 different ∆E values (baseline and 5th-minute, baseline and 10th-minute, 5th-minute and 10th-minute). For ∆E calculations, the CIEDE2000 formula will be used, employing the measured L*, a*, b* and L*, c*, h* values obtained from baseline, 5th-minute and 10th-minute images. For the digital measurements, the intraobserver variability will be assessed, and after obtaining a high level of agreement, the study will be initiated. In statistical analyses, normality will be assessed using the Shapiro-Wilk test; repeated-measures ANOVA will be used if normal distribution is present, and the Friedman test will be applied if normality is not observed. A significance level of p<0.05 will be accepted.

The aim of this clinical study is to clinically evaluate the changes in the fluorescence properties of natural teeth following dehydration.

The hypotheses of the study (H1) are as follows:

1. The change in the fluorescence properties of natural teeth after dehydration exceeds clinically acceptable thresholds.
2. There is a significant difference among the various fluorescence evaluation methods used in clinical practice.

Inclusion Criteria:

• Individuals with caries-free teeth, no enamel defects, no restorations on tooth surfaces, no visible plaque, and adequate cognitive ability to read and understand the informed consent form.

Exclusion Criteria:

• Individuals with teeth exhibiting discoloration or with systemic conditions or medication use that may cause structural changes on the tooth surfaces.

Individuals with caries-free teeth, no enamel defects, no restorations on tooth surfaces, no visible plaque, and adequate cognitive ability to read and understand the informed consent form will be included in the study. Those with teeth exhibiting discoloration or with systemic conditions or medication use that may cause structural changes on the tooth surfaces will be excluded. Maxillary and mandibular anterior teeth will be evaluated.

Data may be shared after the publication of the study