BACKGROUND: Rotation of recently emerged or an emerging tooth before the supracrestal fibres have become established may result in less rotational relapse. AIM: To compare the orientations of the supracrestal fibres attached to recently emerged teeth that have been rotated and retained with the orientation of the fibres attached to teeth that have been rotated and released. METHODS: A customised fixed appliance was constructed to rotate both lower first premolars in four dogs. The teeth were rotated at least 40 degrees as soon as the cusp tips had emerged sufficiently to bond attachments on the teeth. Upon completion of rotation, both teeth were held in the rotated positions and allowed to erupt at the normal rate. When the teeth were fully erupted (approximately 12 weeks) one premolar in each dog was released while the contralateral tooth was held in the rotated position. Eight weeks later, the dogs were sacrificed and the orientations of the supracrestal fibres were measured on projected images of standardised histological sections. RESULTS: The premolar teeth were rotated an average of 56 +/- 13 degrees, and the released teeth relapsed by an average of 12 +/- 4 degrees in eight weeks (i.e. 24 +/- 4 per cent). No statistically significant difference was detected in the orientations of the supracrestal fibres attached to the retained and released teeth, which remained distorted in the direction of rotation (p > 0.05). CONCLUSIONS: The findings suggest that factors other than straightening of the supracrestal fibres may be responsible for relapse of rotated teeth.
BACKGROUND: Rotation of recently emerged or an emerging tooth before the supracrestal fibres have become established may result in less rotational relapse. AIM: To compare the orientations of the supracrestal fibres attached to recently emerged teeth that have been rotated and retained with the orientation of the fibres attached to teeth that have been rotated and released. METHODS: A customised fixed appliance was constructed to rotate both lower first premolars in four dogs. The teeth were rotated at least 40 degrees as soon as the cusp tips had emerged sufficiently to bond attachments on the teeth. Upon completion of rotation, both teeth were held in the rotated positions and allowed to erupt at the normal rate. When the teeth were fully erupted (approximately 12 weeks) one premolar in each dog was released while the contralateral tooth was held in the rotated position. Eight weeks later, the dogs were sacrificed and the orientations of the supracrestal fibres were measured on projected images of standardised histological sections. RESULTS: The premolar teeth were rotated an average of 56 +/- 13 degrees, and the released teeth relapsed by an average of 12 +/- 4 degrees in eight weeks (i.e. 24 +/- 4 per cent). No statistically significant difference was detected in the orientations of the supracrestal fibres attached to the retained and released teeth, which remained distorted in the direction of rotation (p > 0.05). CONCLUSIONS: The findings suggest that factors other than straightening of the supracrestal fibres may be responsible for relapse of rotated teeth.