In a patient with bulimia nervosa, which surface is LEAST likely to show acid erosion?

In bulimia nervosa, repeated self-induced vomiting exposes teeth to gastric acid. The acid follows the path of the vomit, which primarily affects the palatal (lingual) surfaces of the maxillary anterior teeth — this is called 'perimylolysis.' The lingual surfaces of mandibular anterior teeth are protected by the tongue, which shields them from the acidic vomit, making them least likely to show erosion. Additionally, saliva pools in the floor of the mouth, providing buffering protection to mandibular lingual surfaces. The palatal surfaces of maxillary teeth are directly exposed to the acid stream during vomiting.