Braces "start to work" almost immediately - just a few hours after they are placed. Arch wires are the mechanism exerting force upon teeth and are actually responsible for their alignment. After tightening the arches, the patient begins to feel numbness and pain, which are strongest after the first 24-48 hours, can last from 2-3 days up to a week and gradually begin to reduce. The discomfort is strongest in the area of the front teeth (compared to the back) and in the lower jaw (compared to the upper). It is rarely necessary to take painkillers, but still pain is a subjective concept.
Feeding during the initial period of orthodontic treatment can be challenging. However, I have to reassure you that with the right selection of nutrition, the unpleasant feeling during eating will be soon brought to minimal. It is good to start with softer foods (liquids, creams, soups, purees, etc.) and over time you will return to your normal diet.
Crunchy food: popcorn, ice, chips;
Sticky food:caramel products (candies, snickers), chewing gum;
Solids: nuts, candies, toasts, baked rolls, cubes, pitted olives, cherries, etc.;
Snacks: corn, apples, carrots (I recommend cutting them in wedges);
*Chewing on hard objects such as pens and pencils and biting nails.
All of these can damage or rip off the braces. Damaged braces will prolong treatment.