Which factor is not used to diagnose the gingiva of a child?

The contour of the Nasmyth membrane is not used in the diagnosis of pediatric gingiva. The Nasmyth membrane, which is a thin layer of tissue that can cover newly erupted teeth, is not a critical factor when evaluating gingival health or conditions in children.

In contrast, the contour of the gingival papilla, sulcus depth, and the tight filling of the gingival collar are all important indicators of oral health. The contour of the gingival papilla helps assess inflammation and the overall health of the gum tissue. Sulcus depth is a primary measurement in periodontal assessments to determine potential disease or gingivitis, and the tight filling of the gingival collar can indicate the presence of proper dental restorations that conform well with the gumline, which is important for preventing gingival irritation and disease.

Thus, the Nasmyth membrane's contour is not relevant for diagnosing gingival conditions, making it the factor that is not used in this context.