Idiopathic resorption.

We have been following 13 year-old Jessica since she was 9 years old because of an arch length discrepancy with an Angle Class I relationship, on a thin periodontal biotype. Because of the severity of her mandibular crowding, we had discussed beginning a program of serial extractions (fig. 1 a and b). Jessica demonstrated no particular signs of previous malfunctions, her breathing was uniquely nasal, her swallowing was mature, and the absence of muscular signs and dental wear facets indicated there had never been periods of bruxism, nor were there any signs of pencil chewing or nail biting. Her lingual frenum was short, which tended to keep her tongue in a low posture and her upper labial frenum was also in a low position causing a midline diastema. When we took an occlusal photograph, the