Orthodontics · single question
When a tipped second molar is uprighted using a coil spring on an orthodontic wire, what effect is most likely to occur on the second molar?
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Correct answer: B. Supra-eruption and increased bite (increased vertical dimension)
When a mesially tipped second molar is uprighted using a coil spring (open coil) placed between the first and second molars, the mechanics produce extrusive forces on the second molar as it is uprighted. This supra-eruption (excessive eruption) of the second molar will increase the vertical dimension of occlusion (increase the bite) in that area. The anterior teeth may come into infra-occlusion as a result. Intrusion auxiliaries or molar intrusion mechanics may be needed to prevent supra-eruption during uprighting. This is a key consideration in pre-implant orthodontic space development.