Abstract

Objective: This work analyzed the influence of dynamic load in temporary orthodontic screws stability. Materials and methods: Self-drilling titanium (Ti6Al4V) screws (6 × 1.5 mm) for orthodontic anchorage were inserted and removed from pig ribs. Screws were loaded by a static load of 2 N for 5 weeks. Dynamic force was applied during 56,000 cycles for simulations of a patient’s opening-closing mouth movements. The dynamic applied load ranged from 2-5 N under a frequency of 1 Hz. Vertical (pull out) and horizontal (pulling) components of the dynamic load was 15-25% and 96-98% higher than static load, respectively. The insertion and removal torques were measured before and after static and dynamic cycles. Results: No significant (p = 0.2165) difference was observed between insertion and removal torque in the static load (11.51 ± 2.11 N cm vs. 11.37 ± 4.02 N cm). Statistical analysis (p = 0.0026) showed that after dynamic cycles the removal torque (4.2 ± 2.8 N cm) was lower than insertion torque (10.18 ± 1.17 N cm). Conclusions: Dynamic loads demonstrated detrimental effects onto stability of screws, showing that the currently intermittent force usually used by intermaxillary biomechanics might be applied wisely to not lost temporary screws during clinical procedures.

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