Three-dimensional comparison of the effects of sliding mechanics in labial and lingual orthodontics using the finite element method.

INTRODUCTION: The extraction of maxillary first premolars is usually the treatment of choice to resolve crowding, alveolar protrusion, or Class II malocclusion. The demand for a lingual orthodontic treatment is increasing because of its esthetic value; therefore, understanding lingual biomechanics is essential to every clinician. This study compared the 3-dimensional (3D) effects of sliding mechanics in labial and lingual orthodontics using the finite element method. METHODS: Twelve 3D finite element models were created with different power arm heights and miniscrew positions. A 150 g of retraction force was applied from the head of the miniscrew to the power arm. The 3D displacement of the original nodes was measured, and the stress distribution on defined element zones of the periodontal ligament. RESULTS: Different force directions led to different movement patterns and stress distribution. The lingual models showed a more important lingual crown tipping, extrusion, and higher stress values than the labial models. Results were not affected by the vertical position of the miniscrew. CONCLUSIONS: Bodily en-masse retraction was not achieved in all models. Adding extra torque to the archwires is essential to prevent excessive lingual crown tipping. The lingual appliance induced more lingual tipping and extrusion of the anterior teeth. Expanding the archwire is important to minimize the risk of intercanine width reduction. The vertical position of the miniscrew does not affect the results of en-masse retraction.

Hepatic infantile hemangiomas treated with oral propranolol--a case series.

Hepatic infantile hemangiomas may be associated with morbidity and mortality, and traditional therapies may be associated with significant side effects. Since propranolol has been recently used successfully to treat cutaneous infantile hemangiomas, we decided to use it in three patients who presented with hepatic and skin hemangiomatosis. Three patients with skin and hepatic infantile hemangiomas, two of whom had evidence of cardiovascular compromise and one of whom had extensive liver involvement and hypothyroidism, were treated with oral propranolol. Regression of both skin and hepatic hemangiomas was noted in all patients, as was resolution of the cardiac symptoms and decreased thyroid requirement in two patients each. Propranolol was well tolerated without any adverse effects. Propranolol should be considered as a potential first-line therapy in patients with symptomatic hepatic hemangiomatosis.