Force decay evaluation of thermoplastic and thermoset elastomeric chains: A mechanical design comparison.
OBJECTIVE
To compare the following over a period of 8 weeks: (1) force decay between thermoplastic (TP) and thermoset (TS) elastomeric chains; (2) force decay between light (200-g) and heavy (350-g) initial forces; and (3) force decay between direct chains and chain loops (stretched from one pin around the second pin and back to the first pin).


METHODS
TP and TS chains were obtained from American Orthodontics™ (AOTP, AOTS) and ORMCO™ (OrTP, OrTS). Each of the four chain groups was subdivided into four subgroups with 10 specimens per subgroup: (1) direct chains light force, (2) direct chains heavy force, (3) chain loops light force, and (4) chain loops heavy force. The experiment was performed in artificial saliva (pH of 6.75) at 37°C.


RESULTS
A significant difference was found between TP and TS chains, with an average mean difference of around 20% more force decay found in the TP chains (P < .001, α  =  .05). There was no significant difference between direct chains and chain loops except in OrTP, in which direct chains showed more force decay. There was also no significant difference in force decay identified when using light vs heavy forces.


CONCLUSIONS
TS chains decayed less than TP chains, and chain loop retraction was beneficial only when using OrTP chains. Contrary to the interchangeable use of TP and TS chains in the published literature and in clinical practice, this study demonstrates that they perform differently under stress and that a clear distinction should be made between the two.
a  Clinical Assistant Professor, Department of Orthodontics, College of Dentistry, University of Illinois at Chicago, Chicago, IL.
Ahmed I
AI
Masoud
T Peter
TP
Tsay
Ellen
E
BeGole
Ana K
AK
Bedran-Russo
D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D020724:Elastomers / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D012464:Saliva, Artificial / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation*
D003764:Dental Materials; D020724:Elastomers; D012464:Saliva, Artificial
Canine retraction; Chain loop; Force decay; Thermoplastic; Thermoset