An In vitro comparative evaluation of load activation rate of a new designed expansion screw

Objective: .Expansion screws show high load-activation rate and force system that is far from ideal
for moving teeth. Hence, activation of the screw produces a heavy force that cause rapid decays and
has the potential for damaging the teeth and periodontium. The purpose of this investigation was to
assess the force – activation curve of a new designed screw compared to the conventional types.
Material and Methods: In this experimental study, a screw was designed and manufactured with
the similar size of other screws with potential of 8 millimeter expansion( 2 activations, 4 millimeter
in each activation). The screw was embedded in acrylic base of a removable appliance and fixed on
its plaster cast. The compression test machine was used to depict its load-activation curve. The curve
was compared with curves of other screws.
Results: The results of this study showed that the new screw had a lower load-deflection . It
generated a light continuous force of 2-3.5 pounds for 4 millimeter activaton.
Conclusion: Compared with other screws which produced heavy and interrupted forces this design
generated a light continuous force.
Key words: Expansion, Screw, Load- Activation