Influence of different recycling protocols on load deflection of nickel titanium orthodontic wire : an in vitro study

الملخص EN

Background: The purpose of this study was to investigate the changes in the load deflection of nickel titanium orthodontic wire after different recycling protocols.

Materials and methods: A spooled 0.014 inch nickel titanium orthodontic wire was separated into 7 groups: as received condition (T0, control group), treated in artificial saliva for 4 weeks (T1), treated in artificial saliva and autoclaved (T2), treated in artificial saliva and dry heated (T3), treated in artificial saliva and disinfected by glutaraldehyde (T4), treated in artificial saliva and disinfected by iodophor (T5) and treated in artificial saliva and disinfected by chlorhexidine(T6).

The changes in the load deflection were observed by special test apparatus based on 3-point bending mechanism.

Results: The findings of the current study showed that there was highly significant difference in mean load deflection of nickel titanium wire between all recycling protocols (P< 0.0001).

The recycling by sterilization of the wire by heat autoclave or disinfection by chlorhexidine both showed high mean load deflection values which were closer to the control, while the disinfection by glutaraldehyde or iodophor showed intermediate load deflection values, and the sterilization by dry heat showed lowest mean load deflection value.

Conclusions: The different recycling protocols could decrease the load deflection value and this could be due to corrosive degenerative changes of the passive TiO2 film on the wire and subsequently detrimental effect on load deflection.

Sterilization by the heat autoclave or disinfection by chlorhexidine both seem to be the best recycling protocols because both showed least detrimental effect on the load deflection because those protocols showed high mean load deflection values which were closer to the control, while the disinfection by glutaraldehyde or iodophor both showed intermediate detrimental effect on the load deflection because those showed intermediate load deflection value, and sterilization by the dry heat seems to be the worst recycling protocols because it showed highest detrimental effect on the load deflection because it showed lowest mean load deflection value among all examined recycling protocols.

Key words: Recycling, load deflection, nickel titanium wire.

(J Bagh Coll Dentistry 2008; 20(1)105-110)