1：Experimental Design and Method Selection:

The study used confocal Raman microscopy to analyze human enamel cross striations, focusing on chemical composition and crystal orientation. Methods included SEM for reference, polarized Raman spectroscopy for orientation assessment, and K‐mean cluster analysis for composition comparison.

2：Sample Selection and Data Sources:

Six sound molars (three primary and three permanent teeth) were extracted for orthodontic treatment, with informed consent and ethical approval. Teeth were sectioned, polished, and cleaned ultrasonically.

3：List of Experimental Equipment and Materials:

High‐speed diamond saw (Isomet 2000, Buehler, USA), polishing machine (Escil, France), SEM (Analytic FEI Quanta FEG 200, FEI, Hillsboro, OR, USA), confocal Raman microscope (Alpha300R, Witec, Ulm, Germany) with 532 nm laser (Newport, Evry, France), air objective ×20 (Nikon, Otawara, Japan), CCD camera (DU 970 N‐BV353, Andor, Hartford, USA), and software (Image Plus 2.08, Witec; Fiji v1.51, National Institutes of Health, USA; Sigmaplot v11.0, Systat Software Inc, San Jose, USA).

4：08, Witec; Fiji v51, National Institutes of Health, USA; Sigmaplot v0, Systat Software Inc, San Jose, USA). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Teeth were sectioned and polished. SEM images were taken. Raman scans were performed with polarized light at 0° and 90° angulations, recording spectra and images. Data analysis included image reconstruction, cross striation spacing calculation, orientation assessment, crystallinity measurement, and statistical tests.

5：Data Analysis Methods:

Peak intensity images were reconstructed using sum function and KMCA. Spacing was calculated from intensity profiles and FFT. Orientation was assessed via OH to PO4 3? peak ratios. Crystallinity was measured via FWHM of phosphate peak. Statistical analysis used ANOVA, t‐test, and Pearson correlation.