For maxillary expansion, HYRAX uses a force of:

 # For maxillary expansion, HYRAX uses a force of:

A. 2 to 3 pounds

B. 10 to 20 pounds

C. >25 pounds

D. >50 pounds

The correct answer is B. 10 to 20 pounds.

Hyrax (Hygienic Rapid Expander): 

• It is a fixed tooth borne rapid maxillary expansion appliance. 

• The Hyrax Expander is essentially a non-spring-loaded jackscrew with an all wire frame. The main advantage of this expander is that it does not irritate the palatal mucosa and is easy to keep clean. 

• It is capable of providing sutural separation of 11 mm within a very short period of wear and a maximum of 13 mm can also be achieved. Each activation of the screw produces approximately 0.2 mm of lateral expansion and it is activated from front to back. 

• Fixed appliances like Hyrax or Haas, apply forces about 3 to 10 pounds, which can reach up to 20 pounds in daily activation 

• Rapid maxillary expansion appliances uses 10-20 pounds force, whereas slow arch expansion uses 2-4 pounds.