Types of habits involving the lips:
(1) repetitive lip wetting
(2) lip sucking
(3) mentalis habit (named for the mentalis muscle)
(4) lip biting
Features of repetitive lip wetting:
(1) The patient frequently passes the tip of the tongue over the upper or lower lip.
(2) Chronic lip wetting can result in chapping of the skin around the lips.
Features of lip sucking:
(1) The upper or lower lip including the entire vermilion surface is sucked into the mouth between the incisors.
(2) Chronic lip sucking can result in chapping of the skin around the lips.
Features of the mentalis habit:
(1) The skin over the chin may be puckered due to contracture of the mentalis muscle.
(2) The lingual aspect of the lower lip is elevated into the mouth while the vermilion surface is everted.
(3) A sublabial contracture line may develop.
(4) The exposed incisors may become chipped due to repeated trauma.
(5) The child may develop dental malalignments (open bite, overbite, lingular deviation of the lower incisors).
Features of lip biting:
(1) A portion of the upper or lower lip is clamped between closed incisors .
(2) Forceful closure can result in injury to the lips.
Differential diagnosis:
(1) seizure activity with lip biting
(2) self-mutilation in the Lesch-Nyhan syndrome
