Which of the following is not a landmark used for local infiltration?

• A. Lingual frenum
• B. Mucobuccal fold
• C. Crown of tooth
• D. Root contour of tooth

Answer: (A)

The key idea is that infiltration injections are guided by landmarks in the buccal mucosa directly over the tooth’s root, so you can deposit anesthetic near the tooth’s apex. The mucobuccal fold is the actual reference you use to place the needle just above the tooth, giving a reliable path to the target nerves. The crown of the tooth and the root contour are helpful contextual guides: they help you know which tooth is being treated and offer a rough sense of where the root apex sits beneath the surface, aiding you in judging depth and angle.

The lingual frenum, by contrast, lies on the tongue side and is not in the typical buccal injection path. It doesn’t reliably indicate the correct injection site for maxillary local infiltration, so it isn’t used as a standard landmark for this technique.