When first starting probing, where should you insert your probe in Zone 1?

• A. Distofacial line angle
• B. Mesiofacial line angle
• C. Midline on facial
• D. Distolingual line angle

Answer: (A)

When you begin probing a zone on the facial/buccal aspect, choose a starting point that gives easy, stable access into the sulcus. The distofacial line angle of the first posterior tooth in that zone is the natural entry because it sits at the outer, most accessible edge of the buccal sulcus. Placing the probe there allows you to insert parallel to the tooth’s axis and follow the gingival margin into the sulcus, enabling an accurate depth reading while minimizing contact with the tooth surface or papilla. Starting at other line angles tends to place the probe at less favorable angles or closer to the contact area, making it harder to obtain a clean, consistent measurement.