Question

Which of the following orthodontic appliances generates a one-couple system of force?

• A. Cantilever spring
• B. Utility arch wire
• C. Headgear
• D. Transpalatal arch

Hint:

Cantilever → Statically determinate → One force + One couple → One-couple system.

Answer 1

The Correct Option is A

Step 1: Understanding One-Couple System of Force.
In orthodontic biomechanics, a one-couple force system consists of a single force and a single moment (couple) acting on a tooth or segmentThis type of system produces controlled tooth movement with predictable biomechanics
Step 2: Cantilever Mechanics.
A cantilever spring is a statically determinate systemWhen activated, it delivers a single force at one end and a couple at the anchorage unitThis produces a one-couple force systemIt is commonly used for molar uprighting and impacted tooth traction
Step 3: Excluding Other Options.
Utility arch wires often create two-couple systems depending on activation
Headgear primarily applies extraoral force without generating a classic one-couple system
Transpalatal arch mainly provides transverse stabilization and anchorage control rather than a one-couple force system
Step 4: Conclusion.
Since a cantilever spring generates a statically determinate one-couple force system, the correct answer is Cantilever spring