From Surface to Subsurface
Insights into surface-level and internal enamel craze lines
Craze lines in dental enamel, especially in anterior teeth, are commonly regarded as benign age-related features. Typically, these lines are classified as superficial cracks that have a minimal impact on tooth structure because they extend out from the dentinoenamel junction (DEJ) and do not involve the dentin. However, with the increased use of high magnification in dental practice, a more nuanced picture has been revealed, showing that not all craze lines are created equally. This article discusses a distinct type of craze line within enamel-the "internal craze line"- and explores its significance in clinical practice.
Traditionally, all craze lines have been perceived as superficial, nonthreatening cracks that are confined to the enamel. These lines extend from the DEJ to the surface and are usually regarded only as cosmetic concerns. Although they are considered nonstructural, the use of enhanced magnification has raised awareness of their potential to signal deeper structural issues. When imaging reveals that larger and longer craze lines that extend from the incisal edge almost to the cervical region are associated with smaller, shorter lines branching around them, it may indicate potential risk for progression into a structural crack under future functional stress.
In vitro observations have revealed that there are two distinct types of craze lines: surface level and internal. Surface-level craze lines span the full thickness of the enamel, running from the DEJ to the outer surface. In contrast, internal craze lines are confined to the inner enamel, originating at the DEJ but stopping before they reach the surface. Cross-sectional stereo microscope imaging with filters has shown that internal craze lines are subtler and more difficult to detect. These findings highlight the importance of distinguishing between the two types of craze lines during diagnosis because each type requires a different approach when treatment planning.
The recognition of internal craze lines introduces new challenges in clinical practice. These lines, which are shorter and located deeper within the enamel, can be harder to detect without magnification. Unlike surface-level craze lines, they often appear white under certain lighting conditions and angles and may seem thicker than they actually are as a result of light reflection. The use of transillumination reveals all surface-level and most internal craze lines, making it an effective method for diagnosis. However, it can also be misleading because it may exaggerate the depth and width of craze lines. Other technological advancements in dentistry, particularly the use of operating microscopes and high-resolution cameras, have significantly improved our ability to detect these fine enamel structures. Magnification has become essential for identifying internal craze lines, allowing for more detailed examinations and providing better guidance for clinical decisions. This technology is rapidly becoming indispensable for enhancing diagnostic precision and improving treatment outcomes.
From a clinical perspective, the ability to distinguish between surface-level and internal craze lines is essential to providing the most appropriate treatment. Surface-level craze lines can often be treated cosmetically with particle air abrasion or resin applications. In contrast, internal craze lines, being located deeper within the enamel, require a more invasive approach to mask. Efforts to remove them may involve removing a significantly greater portion of the outer enamel, which can compromise the tooth's structure. This underscores the need for accurate diagnosis before pursuing any esthetic or restorative procedures. Moreover, the recognition of internal craze lines dictates the need for further research into their etiology, prevalence, and long-term effects. Understanding how internal craze lines form and their relationship to factors such as age and parafunctional habits could lead to better preventive care and treatment strategies.
In conclusion, improving diagnostic accuracy in distinguishing between surface-level and internal craze lines is critical for informing treatment decisions. As dental professionals, recognizing these subtle differences can significantly impact clinical outcomes and patient care, particularly as magnification technology continues to advance.
About the Author
Masoud Hassan Zadeh, DDS, is a biomimetic restorative dentist with a private practice in Drachten, Friesland, in the Netherlands.
