How do braces move teeth?
Modern orthodontics solves even the most difficult clinical cases: braces move teeth to correct severe crowding, put dystopic teeth in one row, and pull out unerupted canines.
How do such significant changes occur if healthy teeth without braces are absolutely motionless?
The main paradigm of the braces system is a mechanical device capable of developing mechanical forces and, through them, moving teeth in predetermined directions. In addition to dental locks (brackets) and a wire arch (the main elements of the system), such a medical device can include any elements or devices that can be fixed to the main elements or combined with them.
The bracket system consists of two elements - arch and locks (braces), which are fixed on the teeth and hold the arch. The orthodontic arch is made of metal with shape memory. When installed in a bracket system on an uneven dentition, it tends to return to the original “correct” position and pulls the teeth along with it. At the initial stage of treatment, it is important to correctly position each lock on the tooth so that the archwire works in the correct direction.
To create the correct dentition and correct bite, the orthodontist calculates the types of arches, their number and duration of wearing before starting treatment. It is impossible to immediately put one correct arch, which will create an ideal dentition, since the movement should be gradual and not injure the ligamentous apparatus and bone tissue.
Correction of bite is based on the mechanism of action of weak forces and movement of teeth in accordance with the bends and shape of the archwire (Metal wire made of NITI). The metal arch has a "shape memory": it straightens, pulls the braces and moves the teeth in the desired direction.
The formation and destruction of bone tissue is part of the natural movement of teeth. The principle of operation of braces allows you to achieve the goal of orthodontic treatment - to create the best balance of occlusion(the way teeth meet during bite), aesthetics of the face and dentition.
In order to understand how braces move t teeth, you need to start with the structure of the tooth-jaw system. The roots of the teeth are located in the holes (socket) in the bone tissue of the alveolar processes of the upper and lower jaw. Between the root of the tooth and the bone is the ligamentous apparatus of the tooth - the connective fibers that fix the tooth in the bone tissue. When braces move teeth, not only the visible coronal part moves, also the root inside bone socket moves along with.
The roots of the teeth under the influence of braces stretch the ligaments, and the bone tissue under pressure slowly decreases on one side and grows naturally on the other. With the help of braces, the tooth moves in the bone tissue gradually and safely - still reliably held by the ligaments.
Biomechanics of teeth movement with braces
To understand how braces move teeth, let us turn to the biological and physiological processes that occur during the movement of teeth. The teeth are located in the alveoli - natural cavity in the jaw bones of the skull. The root of each tooth is surrounded by periodontal fibers holding the tooth in the socket.
The fibers also have a shock-absorbing function: they allow the tooth to make micromotions in all directions. After fixing the bracket and placing the archwire, force begins to act on the tooth root. For a slow and least painful movement of the teeth, a weak and prolonged force is produced.
Due to the movement of the tooth root, it becomes necessary to free up space in the alveolus. For this, osteoclasts begin to destroy the bone at the point where the root touches the wall of the alveoli. Osteoclasts are special cells that remove bone tissue. On the opposite side, osteoblasts produce new bone to fill the vacated space. Under the influence of osteoclasts and osteoblasts, the balance of the formation and destruction of bone tissue ensures the translational movement of the teeth.
The periodontal ligament is a very important structure in the movement of teeth in orthodontics and the stability of teeth in general.
(A) It contains fibers that attach the root of the teeth to the alveolar bone that surrounds it. The ligament space between the tooth and the root (0.25 mm) allows slight movements of the teeth when force or pressure is applied to the teeth (chewing, teeth clenching, etc.).
(B) Small blood vessels (capillaries) irrigate and nourish the bone and ligament. Specialized cells will remove bone in some places and deposit it in other places, allowing orthodontic teeth to be moved over distances of several millimeters. ((B) Capillaries of the periodontal ligament of a young rabbit - Kronka 2001)
How implants help the braces to move teeth
An orthodontic microimplant is an absolute support. They are used when it is necessary to move the tooth in the exact direction without changing the position of others. The fact is that when elastic traction is used from tooth to tooth, both the supporting group of the teeth and the tooth that needs to be moved are involved in the movement.
The abutment teeth also move and the effectiveness of the rods becomes much less than when using an absolute fixed support. Miniscrews are screwed into the bone tissue under local anesthesia and are easily removed after completion of orthodontic treatment.
Periodontium health and tooth movement with braces
The periodontium includes the supporting tissues of the teeth; the alveolar bone, the gum and the periodontal ligament between the root of the teeth and the bone.
A healthy periodontium is essential for normal tooth movement in orthodontics… and for the survival of teeth in general.
The cells in the ligament space around the root of the tooth must be healthy to allow resorption and bone formation necessary for normal movement of the teeth.
The structures of the periodontium are fragile. If too much force is applied, they can damage these fragile tissues and slow or prevent orthodontic movement of the teeth.
On the other hand, if the force used is not sufficient, the specialized cells will not be stimulated to perform their action on the bone, which is essential for moving the teeth.
In orthodontics, this force comes from different components (wires, springs, etc.) but mainly elastics which must be worn as prescribed in order to get the most out of the physiological reactions of the periodontium and promote optimal movement of the teeth.
Poor oral hygiene causes plaque buildup which will cause inflammation. In the long term, the latter damages the periodontium and destroys it, which interferes with or prevents orthodontic movement of the teeth. To learn more about the importance of oral hygiene in orthodontics.
How much force is enough for brace to move teeth
There is an optimal physiological force to move teeth well in orthodontics. The periodontium is sensitive to the application of this force and will react according to the force applied to the teeth to move them.
An ideal force will maximize tooth movement while too little force will not allow the teeth to move. In contrast, and contrary to what one might instinctively believe, too much force will not only not speed up the movement of the teeth but may even prevent it from occurring or significantly slow it down!
Moving teeth in orthodontics does not happen like when you press the accelerator in a car; more “force” = more speed. To understand this complex phenomenon that manages the movement of teeth.
Movement of devitalized(RCT treated) teeth possible with braces
When a tooth “dies” or becomes non-vital, it is necessary to remove the contents of the pulp chamber and root canals (nerve, blood vessels) and replace them with inert material. This procedure is called a " root canal treatment " and is performed by a general dentist or an endodontist (a specialist in this type of treatment).
This may be necessary as a result of infection (e.g. progression of decay which can lead to the formation of an abscess), trauma that fractured a tooth, change in internal tooth color, etc.
A tooth having a root canal can be moved orthodontically as well as a normal tooth if the root and periodontium are intact and healthy. The important element in the movement of teeth is the periphery of the root and the cells therein. The interior of the root has no influence on a tooth's ability to move through bone when subjected to orthodontic forces.
Does braces move all teeth at same time
When applying forces to teeth, it is difficult, if not impossible, to determine exactly which tooth will move in which sequence and at what rate relative to other teeth. Side effects occur on adjacent teeth when a tooth is subjected to force. Thus, it is possible that some teeth move faster than others and show different mobility and sensitivity. If a tooth has the space to be moved, the more easily and quickly it can be moved than a tooth that is lacking space, is crowded or severely overlapped.
It is therefore not abnormal to have different sensitivity or mobility on various teeth in the mouth during orthodontic treatment. The forces are not always applied exactly evenly and at the same time to all teeth. Significant pain that persists, however, may indicate a problem such as occlusal trauma , periodontal problem, decay, etc., but not necessarily. Clear aligner techniques like Invisalign / ClearCorrect can better control and predict the application of forces to teeth. Thus, it is possible to immobilize certain teeth completely while moving one or more others, which is more difficult to do with fixed multi-ring devices (“pins”). Regardless of the technique used, different mobilities, sensitivities and movements can be observed for different teeth.
Types of teeth movement with braces
The main movements that we perform in orthodontics to move teeth can be categorized as follows: Intrusion or intrusion : moving a tooth vertically towards the bone either upwards for the upper teeth or downwards for the lower teeth. This may be necessary, for example, when anterior teeth overhang excessively such as in Class II division 2 cases . Orthodontic tooth intrusion is vertical movement in the apical direction (towards the root) of the tooth. Examples of dental intrusion to reduce excessive vertical overbite (overbite).
In the following 2 cases, the upper and lower incisors were “intruded” in the direction of the arrows; those at the top have therefore been “raised” and those at the bottom have been “lowered”. Despite several millimeters of vertical movement, the length of the teeth did not decrease, as the teeth were not driven into the bone. Instead, the gum and bone surrounding the teeth followed them in their vertical movement.
Extrusion or extrusion: moving a tooth vertically towards the opposite arch either down for an upper tooth or up for a lower tooth. Orthodontic tooth extrusion is a vertical movement in the coronal direction (towards the crown) of the tooth. This type of orthodontic movement is often used to close certain types of anterior open bite where the anterior teeth are not touching.
The typical example is the closure of anterior or posterior open bite.
Translation or horizontal displacement: in the “front-rear” direction: this movement is indicated for example to close an extraction space or to move back too protruding anterior teeth (excessive overjet).
A) During the horizontal movement of a tooth (translation), one might think that the tooth is moving gradually (A, B and C) staying straight in the bone, but it is not. (B) Because of the bone's resistance to movement, the crown of the tooth (part outside the bone) tilts forward or backward depending on the direction of movement. (C) The tooth must subsequently be straightened so that the crown and root become straight again, but in a new, more advanced position. This phenomenon is one of the reasons why the closing of large spaces by translational movement can be relatively long.
Multiple simultaneous movements The different types of movements described on this page do not occur on an individual basis and it is common for different teeth to require different movements in order to move them towards their ultimate goal of contributing to achieving a normal or ideal bite.
Intrusion and extrusion movements often occur together in the same mouth. (A) This malocclusion presents excessively elongated incisors which will have to be “intruded” in the direction of the arrows. Canines (*) that have not completed their eruption will become longer as they emerge from the gum tissue, which is due to the normal eruption process. (B) After the corrections, the canines are “lowered” to an ideal vertical level. The incisors were moved several mm, but kept the same crown length, because the bone and the gum line followed the movement of the teeth.
Is the movement of the teeth painful?
Now it becomes clear that teeth can move at any time. All you need is an intact tooth root, the holding fibers at the tooth root and a healthy jawbone. In addition, a little pressure from one side over a sufficiently long period of time. Then the tooth moves. At any age! Depending on your metabolism and age, this can happen at different speeds, but it works. “Doesn't that hurt?” Many patients ask.
Yes, sometimes more, sometimes less. But overall, that's not that bad. It is most uncomfortable in the early stages of any movement in particular. Then, depending on the strength of the movement, this tenderness disappears quickly. For most loose, removable braces, this only takes minutes to a few hours. In the case of fixed braces, the sensitivity usually persists for about two to three days, with the first activation even five days. But you gradually get used to it.
Those who suffer more can also take a light pain reliever. However, it should not have anti-inflammatory effects at the same time, as this impairs the remodeling processes of the jawbones. This means that the pressure of the tooth to be moved remains, the bone does not remodel sufficiently and the tooth movement slows down or stops completely. Smoking also worsens tooth movement. In addition, there are certain diseases or drugs that are unfavorable for tooth movement. In these rare cases, your orthodontist will discuss this issue with you and suggest alternative solutions.
Accelerated orthodontic tooth movement: molecular mechanisms
Hechang Huang, Ray Williams, Stephanos)
Biological Events in Periodontal Ligament and Alveolar Bone Associated with Application of Orthodontic Forces L Feller, R A G Khammissa, I Schechter, G Thomadakis, J Fourie, J Lemmer)
Corticotomy for orthodontic tooth movement (Won Lee)