Short answer: Teeth are not directly fused to the bone; between the root and the bone there is a thin connective tissue called the periodontal ligament. When orthodontic force is applied, bone is broken down on one side of the tooth and new bone is formed on the opposite side. Because this bone remodeling takes time, gentle and continuous forces are used and a retainer is needed after treatment.
It is only natural to wonder how braces or clear aligners "push" the teeth, because to the eye teeth look firmly seated in the bone. In reality, the answer to how teeth move lies in the body's ability to renew bone continuously. In this article we explain the biology of orthodontic tooth movement without drowning in technical terms.
Are teeth fixed to the bone?
No; the root of a tooth does not fuse directly with the bone, and between them there is a thin layer of connective tissue called the periodontal ligament. This tissue works like a kind of buffer: it absorbs chewing forces, gives the tooth a sensitive sense of touch and allows the position of the tooth in the bone to be adjusted slightly.
The bone surrounding the tooth is not a static structure either. Throughout life, bone is constantly renewed by cells that break down old tissue and build new tissue. Orthodontics is the work of directing this natural renewal mechanism in a particular direction with a controlled force. For this reason, structures that fuse with the bone, such as implants, cannot be moved orthodontically; natural teeth, which have their own ligament, are the ones that move.
What happens around the tooth when force is applied?
When a tooth is pushed in a particular direction, one side of the root compresses the ligament while the other side stretches it. Dentists call these the pressure zone and the tension zone.
- Pressure zone: The ligament is compressed and cells in the area produce chemical signals. These signals call in osteoclasts, the cells responsible for breaking down bone. Osteoclasts slowly dissolve the bone in the direction the tooth will move and make room for the tooth.
- Tension zone: The ligament is stretched and osteoblasts, the cells responsible for building bone, are activated. The space the tooth leaves behind is filled with newly formed bone.
As a result, while the tooth "slides" from one place to another within the bone, bone is actually being broken down in front of it and built up behind it. Because this cycle works at the cellular level, it takes days to weeks; it is not possible to move teeth all at once.
Why are gentle and continuous forces used?
Gentle and continuous force is used because the tissue responds in the most balanced way to it. A very large force can restrict blood flow in the ligament excessively; in this case the tissue is strained instead of remodeling in a healthy way, movement may slow down, and structures such as the root surface can be loaded unnecessarily. A very weak force, on the other hand, may not create a sufficient biological signal.
For this reason, the type and amount of force needed differs for each tooth. Aligning a small front tooth does not require the same force as repositioning a large molar. The size of the tooth, its root structure and its direction of movement are taken into account in the dentist's planning. Rotating a tooth, moving it forward or back, extruding it and intruding it each call for different mechanical approaches.
In the clear aligner system, this principle is applied by having the aligner guide the teeth in very small steps at each stage. The planning software divides the movement into successive small stages; each new aligner is slightly different from the one before. Small tooth-colored bumps called attachments may be used to grip some teeth and direct the force in the right direction. For an overview of the process, you can take a look at our clear aligner treatment page.
Why does the speed of movement vary from person to person?
Because the speed of tooth movement varies from person to person, it would not be right to give an exact schedule. Age, bone structure, metabolism, gum health, systemic diseases, medications taken and the type of movement can affect the speed. In young people bone renewal is in most cases more active; in adults the process may proceed at a more measured pace, but when there is healthy gum and bone support, treatment is carried out successfully in adults as well.
Patient compliance is also an important factor. Wearing the aligners for the recommended time, using elastics or similar aids as instructed and not missing appointments keep the tissues stimulated continuously and regularly. If the aligners are left out for long periods during the day, the force is interrupted and the process can be prolonged. For the factors that affect the duration, you can look at our article on treatment time.
For this reason, statements such as "it finishes in so many months" that you hear on the internet or around you may give a general idea, but they may not apply to you. The dentist's estimate, based on the exam and records, can also be updated throughout treatment.
What factors support and what factors make tooth movement harder?
The element that most supports tooth movement is healthy gum and ligament tissue. Regular oral care keeps the gums free of inflammation; on an inflamed foundation, managing orthodontic force becomes harder. Because smoking and uncontrolled systemic diseases can affect the healing capacity of the tissue, dentists ask about these as well.
Conditions that make movement harder include dense bone structure, very long or very short roots, previous dental injuries and ankylosis, the condition in which a tooth is fused to the bone. The direction of the tooth and the position it needs to reach also matter: rotating a tooth around its own axis presents a different difficulty than moving it forward as a whole. For this reason, the dentist also looks separately at the root structure and bone condition in the records.
Teeth that are removed during treatment, or planned extractions, also change the mechanics of movement. When closing a space, teeth are slid sideways; this movement can take longer than turning a tooth on its own. Because all of this is taken into account at the planning stage, it is not right to say "a tooth will settle into place in so much time".
Is the tenderness felt during treatment normal?
Short-term tenderness or a feeling of pressure in the teeth is common after a new wire adjustment or a new aligner stage, and it mostly eases within a few days. This sensation is a usual sign that the tissues are responding to the force. With severe, steadily increasing pain, gum swelling, a loose tooth or sores, however, you should let your dentist know. Pain threshold varies greatly from person to person; instead of making your own interpretation, share what you experience with your dentist.
Why do the teeth try to go back after treatment?
Because settling into their new positions requires the neighboring tissues to adapt as well, the teeth tend to return to their old positions after treatment. The newly formed bone is not fully mature at first; the ligament fibers and the fibrous structures around the gum adapt to the tooth's new position more slowly. These tissues carry a certain "memory" and can pull the teeth back toward their old places. In addition, with age the teeth can show a tendency to drift slightly forward.
This is exactly why a retainer is indispensable. A retainer is a retention appliance that holds the teeth in their new positions while the tissue matures and afterward. How it is used and for how long is determined by the dentist according to the individual. For details, you can look at our page on retainers after clear aligners and our article on why teeth shift again after treatment.
When should you seek an evaluation in Ankara?
If you notice crowding, gaps or a bite problem in your teeth, or if you had treatment in the past and think your teeth have shifted again, a records-based evaluation can be carried out at our clinic in Çankaya, Ankara. To make an appointment, you can use our contact page.
Frequently asked questions
Does bone really dissolve during tooth movement?
It is a process of remodeling, not of bone loss. While bone is broken down on the side the tooth is moving toward, new bone is built on the other side. Under healthy conditions, the total bone support is maintained.
If I apply more force, will the teeth move faster?
No. Excessive force can strain the tissues and slow down movement. For this reason, controlled, gentle and continuous force is preferred.
Can implants be moved orthodontically?
No. Because an implant is fused to the bone and has no periodontal ligament around it, it does not move with orthodontic force. For this reason, the position of the implant is taken into account during planning.
Do I have to wear a retainer for life?
The duration and manner of use are determined by the dentist according to the individual. To maintain the new position of the teeth in the long term, long-term use that decreases over time is generally recommended.