To preserve biological width, the crown margin must be how many millimeters above the alveolar crest?

• A. 1mm
• B. 1.5mm
• C. 2mm
• D. 2.5mm

Answer: (C)

The requirement for preserving biological width is critical in restorative dentistry, particularly when placing crowns. Biological width is the distance from the alveolar crest to the junction of the epithelium and connective tissue attachment; it usually measures around 2.0 mm to 2.5 mm in healthy gingival tissue.

For proper crown margin placement, it is essential that the margin be positioned at least 2 mm above the alveolar crest. Positioning the crown margin at this distance helps to ensure that the junctional epithelium is not placed under tension or irritation, which could lead to inflammation, pocket formation, and eventual loss of periodontal attachment.

By maintaining a margin that is 2 mm above the alveolar crest, the clinician allows adequate space for the biological width. This practice not only supports periodontal health but also contributes to the long-term success of restorative treatments. Maintaining this distance aids in preventing complications and promotes the stability of the surrounding periodontal structure. Therefore, understanding and adhering to this guideline is essential for effective dental treatment planning and ensuring the health of periodontal tissues around crowns.