Tight lip syndrome
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Tight lip syndrome is a congenital disorder observed in some Shar Pei puppies where the lower lip curls over the mandibular teeth, particularly affecting the canine and incisor teeth. This abnormal lip positioning causes the mandibular teeth to be pushed inward, disrupting normal jaw alignment and growth. As puppies grow, the maxilla typically expands before the mandible. The interference caused by the curled lip can prevent the mandible from growing properly and can lead to a misalignment of the teeth.[1]
In the 1990s, selective breeding resulted in Shar Pei dogs with an increased amount of facial flesh, leading to a range of health problems, including small external auditory canals, edematous facial features, and traumatic occlusions. Breeding for heavier, smushier faces in particular led to the condition referred to as "tight lip syndrome," in which the lower lip may cover the mandibular incisor teeth, causing lingual tipping of these teeth and impeding normal bite alignment, leading to an underbite.[2][3]
Clinical presentation
Affected dogs often exhibit a lower lip that covers the incisal edges of the mandibular incisor teeth, as well as secondary trauma from the maxillary incisor teeth. This can result in a shallow vestibule, making eating and oral comfort challenging. Early signs include sloppiness while eating and frequent biting of the lip, which indicates discomfort.[2]