This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Gjessing canine is made up of 
Select and explain. 
A. 0.18 x 0.25 stainless steel rectangular wire, B. 0.16 x 0.22 stainless steel rectangular wire, C. 0.17 x 0.25 TMA wire, D. 0.15 x 0.22 TMA wire
B: 0.16 x 0.22 stainless steel rectangular wire
Answer: B: 0.16 x 0.22 stainless steel rectangular wire 
Explanation: The PG spring is made in 0.016″x.022″ stainless steel rectangular wire. It has gingivally directed overlapping double helices, ovoid in shape, 10 mm in height and 5.5 mm at its widest part. It also has a small occlusal helix 2 mm in diameter.
The spring induces bodily movement of teeth and anchorage, reinforcement by a Nance button or headgear is needed in moderate to high anchorage cases. A prerequisite before placing this spring is good rotational correction as well as leveling and alignment of the three teeth involved.
PG canine retraction spring was introduced to the orthodontic profession way back in 1985 by Poul Gjessing, hence also known as Gjessing Canine.