When checking the 'F' and 'V' sounds during a complete denture try-in, where should the incisal edges of the maxillary anterior teeth contact?

Correct answer: B. The inner (wet/vermilion) border of the lower lip

• A. The upper lip plays no role in labiodental sounds; it is the LOWER lip that meets the maxillary incisors.
• B. CORRECT. The labiodental fricatives 'F' and 'V' are produced by the maxillary incisal edges contacting the junction of the wet and dry vermilion — the INNER (wet) border of the lower lip. If the teeth are set too far facially or are too long, the incisal edges strike the outer dry vermilion and the patient sounds as if producing a 'V' when saying 'F'. If they are too short or too palatal, the sounds become breathy or 'F' turns into 'V'.
• C. Absence of contact means the teeth are too short or set too far palatally, and the sounds cannot be formed correctly.
• D. Contact on the outer dry vermilion means the anterior teeth are set too long or too far labially.

Note: The phonetic set worth memorising: F/V check incisal edge POSITION and LENGTH (labiodental); S checks the closest speaking space and vertical dimension (a whistle suggests too much space or a narrow arch); D/T check anterior tooth position relative to the palate.