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What is the specified MD length for a cingulum rest?
1-2mm
2.5-3mm
3-3.5mm
4-5mm
The correct answer is: 2.5-3mm
A cingulum rest is a type of retention for a crown or bridge on a tooth. It is located on the lingual surface of anterior teeth and provides vertical and horizontal stability. The specified MD (mesiodistal) length refers to the distance between the distal and mesial cingulum edges on the tooth. While all the options listed may potentially be used, the best option is 2.5-3mm. This is because it provides enough space for the retention without being too deep, which can potentially weaken the tooth structure or impinge on the pulp. The other options listed have either too small or too large of a MD length, making them unsuitable for use as a cingulum rest.