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
Frontal resorption is caused due to: 
Select and explain. 
A. Light continuous force, B. Heavy continuous force, C. Heavy interrupted force, D. Light interrupted force
A: Light continuous force
Answer: A: Light continuous force 
Explanation: Frontal resorption (direct/periosteal/forward resorption)

With light continuous forces, the bone is resorbed directly by a frontal osteoclastic attack. 
The first step in orthodontic tooth movement is the activation of osteoclasts.
In frontal resorption, resorption is initiated from the PDL side of the alveolar bone. It usually takes place after 2 days.