IADR Abstract Archives
Transition Temperatures and Mechanical Behavior of Variable Force Nickel-titanium Wires
Objectives: Variable force nickel-titanium (NiTi) orthodontic archwires were designed to deliver lighter forces to the anterior teeth and greater force toward the premolar and molar region. The manufacturers use different processing variables for each of the segments of the wires during manufacturing, thus optimizing the force levels.
To characterize the phase transformation and load-deflection behavior of the anterior, premolar, and molar segments of two different variable-force archwires and compare them with a non-variable force NiTi archwire.
Methods: Archwires of two variable force brands, BioForceTM (Dentsply GAC International) and TriTaniumTM (American Orthodontics), were tested. For each wire, three separate subgroups–Anterior, Premolar, and Molar-were evaluated and compared respectively to NeoSentalloyTM (Dentsply GAC) as a non-variable force control. Sections (4mm) representing the central region of each segment were analyzed with differential scanning calorimetry (n=10/segment/wire) from -100↔150oC at 10oC/min to determine austenite-finish (Af) transformation temperatures. Sections (20mm) were deflected to 3.1 mm at 37oC in a 3-point bending test (n=20/segment/wire) to determine activation/deactivation forces. Data were analyzed using two-way ANOVA (p<0.05).
Results: The austenite-finish temperature and load-deflection values obtained are given below:
A significant interaction (p<0.05) was found between wire and segment. The variable force wires exhibited differences in Af and deactivation forces among the different segments, but the values were not consistent between manufacturers. As expected, the non-variable wire exhibited near constant values.
Conclusions: The variable force orthodontic wires demonstrated higher segmental austenite-finish temperature and lower load-deflection in the anterior segments than in premolar and molar segments.
To characterize the phase transformation and load-deflection behavior of the anterior, premolar, and molar segments of two different variable-force archwires and compare them with a non-variable force NiTi archwire.
Methods: Archwires of two variable force brands, BioForceTM (Dentsply GAC International) and TriTaniumTM (American Orthodontics), were tested. For each wire, three separate subgroups–Anterior, Premolar, and Molar-were evaluated and compared respectively to NeoSentalloyTM (Dentsply GAC) as a non-variable force control. Sections (4mm) representing the central region of each segment were analyzed with differential scanning calorimetry (n=10/segment/wire) from -100↔150oC at 10oC/min to determine austenite-finish (Af) transformation temperatures. Sections (20mm) were deflected to 3.1 mm at 37oC in a 3-point bending test (n=20/segment/wire) to determine activation/deactivation forces. Data were analyzed using two-way ANOVA (p<0.05).
Results: The austenite-finish temperature and load-deflection values obtained are given below:
A significant interaction (p<0.05) was found between wire and segment. The variable force wires exhibited differences in Af and deactivation forces among the different segments, but the values were not consistent between manufacturers. As expected, the non-variable wire exhibited near constant values.
Conclusions: The variable force orthodontic wires demonstrated higher segmental austenite-finish temperature and lower load-deflection in the anterior segments than in premolar and molar segments.
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