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
In orthodontic treatment, in order to avoid injuries to the
tissues, the forces applied generally should not exceed: 
Select and explain. 
A. Capillary blood pressure, B. Diastolic arterial blood pressure, C. Masticatory forces, D. Systolic arterial blood pressure
A: Capillary blood pressure
Answer: A: Capillary blood pressure 
Explanation: It has been stated by Oppenheim and Schwarz, a result of their experiments, that optimum orthodontic force would be equivalent to the capillary pulse pressure or 20–26 g/cm2 of root surface. 
With this light force, tooth movement would be by direct osteoclastic activity in the area of greatest pressure; undermining resorption would not occur. 
The optimum force should be one that moves the tooth most rapidly in the desired attitude and direction with the least tissue damage and the slightest amount of pain.