Elastomeric chains were introduced to the orthodontic profession in the 1960s and have since become an integral part of everyday practice. They are used to generate light, continuous forces for correcting rotations, consolidating spaces, and retracting canines. They are inexpensive, easy to apply, relatively hygienic, and require little or no patient cooperation.

Elastomeric chain, however, are not without their disadvantages:

• They absorb water

• Stain

• Undergo Rapid Force decay

• Plaque retentive

How much Force decay happens with elastomeric chains ?

With regard to force decay, it is believed that 50 to 70% of the initial force is lost in the first 24 hours, with most of the loss within the first hour and a steady decline over 3 to 4 weeks ( Mirhashemi et al.)

Therfore it is recommended to change the power chain every 4 weeks (Dixon)

What causes Rapid force decay ?

• Stress relaxation

• Increased temperature (Sulaiman et al.)

• Acidic environment (Nattrass et al)

• Water absorption (cheng et al.)

• fluoridated and whitening mouthwash might produce force degradation, with a stronger effect for the whitening mouthwash (Benhaz et al.)

• Manufacturing: die-cut stamped elastomers maintained higher levels of force than the injection-molded ones. (Hershey and Reynolds)

How to intercept this force decay ?

• Pre stretching (Kim) (Fattahi et al)

• Over stretching to compensate for the force decay (Anderson & Bishara)

• Replace with Niti Coil springs, Less force degradation (Dixon et al)

Effectiveness of nickel-titanium springs vs elastomeric chains in orthodontic space closure: A systematic review and meta-analysis

• Suggeseted there is a moderate quality of evidence suggesting a faster orthodontic space closure with the NiTi-CS when compared to EPC.

There are four types depending on the distance between the elastic rings.

• Closed/continuous.

• Short.

• Long.

• Extra-long.

Long and extra-long EPC are used in the upper arch while closed and continuous EPC are mainly used in lower arch, due to interbracket distance.

Advantages: Cheap , efficient, Versatile, Available in multiple configurations and colors

Clinical variables affecting performance of elastomeric power chains:

• Interbracket distance

• Degree of stretch

• Chain design (closed vs open/short/long)

• Oral environment factors

Despite their limitations, elastomeric chains remain a cornerstone of orthodontic mechanics due to their versatility , cheap cost and efficiency but with an understanding of their force characteristics and biological limitations.

References:

• Surface Treatment on Physical Properties and Biocompatibility of Orthodontic Power Chains (Cheng et al)

• Effectiveness of nickel-titanium springs vs elastomeric chains in orthodontic space closure: A systematic review and meta-analysis (Mohammed et al)

• Force degradation of orthodontic elastomeric chains: A literature review (Ali Rahman issa and Ammar Salim)

• Planets of Orthodontics (Almuzian, Khan, Ahmed, Jaffery)