Distinguishing Traditional and Internal Craze Lines in Human Enamel

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Objectives: This study aims to introduce and differentiate between traditional craze lines and a newly identified type of line in enamel, termed an “internal craze line.” This novel classification enhances diagnostic precision and carries significant clinical implications for treatment strategies. The goal is to provide a clear description of these two types of lines, discuss their unique clinical implications, and highlight their differing appearances and staining characteristics, contributing to improved understanding and management of enamel anomalies. Method and materials: Four extracted teeth exhibiting visible and internal craze lines were selected and examined using a stereo microscope to observe the structural characteristics of the lines. Cross-sections of the coronal parts of the teeth were prepared to document the differences between traditional craze lines (extending from the dentin-enamel junction [DEJ] to the enamel surface) and internal craze lines (originating at the DEJ but terminating midway through the enamel). Additionally, intraoral observations were conducted under high magnification to identify the visual differences between the two types of lines, noting that traditional craze lines can be stained while internal craze lines cannot. Results: Microscopic examination revealed two distinct types of lines: traditional craze lines extending from the DEJ to the enamel surface and internal craze lines terminating within the enamel. Intraoral observations confirmed that these lines could be distinguished under high magnification. Traditional craze lines appear as continuous lines reaching the enamel surface and can be stained, whereas internal craze lines are shorter, do not extend to the surface, and cannot be stained. Conclusion: The identification of internal craze lines presents significant clinical implications. Differentiating between traditional and internal craze lines can enhance diagnostic accuracy and inform treatment decisions. Recognizing internal craze lines might indicate different etiologies or risk profiles compared to traditional craze lines, influencing preventive and therapeutic strategies in dental practice. Further research is needed to explore the prevalence, causes, and long-term impacts of internal craze lines.