How teeth actually move

The periodontal ligament

Between each root and the bone socket around it sits a thin layer of fibres and blood vessels called the periodontal ligament. When steady pressure is applied to the crown of a tooth, that ligament is compressed on one side and stretched on the other. The compressed side signals cells called osteoclasts to dissolve a little bone; the stretched side signals osteoblasts to lay new bone down. The socket effectively migrates, and the tooth travels with it.

This is why orthodontic force must be light and continuous rather than heavy and intermittent. Heavy force crushes the ligament and cuts off its blood supply, which stalls movement rather than speeding it and raises the risk of root resorption. It is one of the genuine differences between orthodontic treatment and simply pushing on teeth.

What the wire is doing

The first archwires placed are usually nickel-titanium, an alloy with a useful property: it can be deflected a long way and still pull back toward its original shape with roughly constant, gentle force. Threaded through crowded brackets, it wants to straighten, and over weeks it drags the teeth into its own curve.

As alignment improves, wires progress to heavier and more rigid rectangular sections. A round wire mostly tips crowns. A rectangular wire engaging a rectangular bracket slot controls the root as well — torque, in orthodontic language — which is how teeth are moved bodily rather than simply leaned into position. That progression is why treatment has a sequence and why the last several months matter as much as the first.

Why it takes months

Bone remodelling has a biological rate of roughly a millimetre per month under favourable conditions, and it is slower through dense cortical bone or in an adult with less cellular turnover. No bracket design changes it. Devices and techniques marketed as halving treatment time have generally not held up when tested properly; the honest levers on duration are case difficulty, whether elastics are worn, whether brackets stay bonded, and whether appointments are kept.

Why it feels sore

The ache after an adjustment is inflammation in the ligament, not damage. It peaks around twenty-four hours after the wire is changed and settles within a few days, and it is milder at each subsequent visit as the tissues adapt. Chewing feels tender because the ligament is already loaded. Soft food for two days handles most of it.