Leveling of the second molar with a superelastic spring.
BACKGROUND
Second permanent molars often erupt during fixed appliance treatment. When they are to be incorporated into the fixed appliance, it is often not possible to bond the buccal tube in the correct position.


METHODS
We describe herein a method for aligning second permanent molars by means of a superelastic segmental archwire. This involves the application of a rigid steel archwire extending from the right first molar to the left first molar for anchorage. This method was investigated in-vitro and in its clinical application. The in-vitro test was carried out with a hexapode simulating the vertical deviation of the second molar.


RESULTS
A .016'' x .022'' stainless steel archwire achieved forces of 13 N; a TMA archwire attained 5 N (both with a deflection of 2 mm), and the superelastic late-leveler achieved a maximum force of 1.3 N with a 5 mm deflection. The maximum uprighting torquing moments were 55 Nmm with the stainless steel archwire, 25 Nmm with the TMA archwire and 2 mm deflection, and 4 Nmm with the late-leveler and 5 mm deflection.


CONCLUSIONS
The forces and moments of stainless-steel and TMA archwires are too high for the alignment of second permanent molars. The moderate forces and moments occurring with the superelastic late-leveler are capable of intruding, derotating and uprighting the second molar. The vertical component prevents artificial opening of the bite.
Sander
Christian
C
University of Ulm, Department of Orthodontics, Oberer Eselsberg, 89081, Ulm, Germany. guenter.sander@uni-ulm.de
Sander
Franz Martin
FM
Sander
Franz Günter
FG
D000497:Alloys; D001696:Biomechanical Phenomena; D004548:Elasticity; D006801:Humans; D008963:Molar; D052280:Orthodontic Anchorage Procedures; D016382:Orthodontic Appliance Design; D009969:Orthodontic Wires; D014087:Tooth Movement Techniques / Q000295:instrumentation; D019415:Torque
D000497:Alloys; C013616:nitinol