There are plenty of braces to put the teeth in the right proportions next to each other and to get the lower and upper jaw together. The different types of equipment are described below.
Plate equipment is suitable for moving one tooth or a group of teeth. A plate consists of a number of parts:
- Base plate. This is a synthetic resin plate that lies against the palate.
- Anchors are installed in the base plate (for example Adam anchors, button anchors or three-quarter anchors) that hold the plate in place and absorb the reaction force of the active parts.
- Active wires (for example, protusion springs or hunting horn feathers). These are bent metal wires that, after being tightened, can move the elements with a tipping motion.
- In addition, there are whole or shared labial arches, which give the plate strength and with which, for example, an upper front can be raised.
Elements can be moved with a tipping motion with plate equipment. This means that the crown moves under pressure from the respective spring or wire, but that the root remains largely in place (see image below).
The synthetic resin plate can still be provided with a bite. A deep bite in the front can be lifted with the help of a bite. A bite is a synthetic resin thickening on the plate, which usually lies palatally from the front elements. As a result, the front teeth in the lower jaw occlude prematurely on the bite. The molars and premolars will therefore not come together and grow out. A too large vertical overbite becomes less as a result. The bite can also be applied to molars. In this way the approaching is temporarily prevented. For example, with a reverse bite, the front elements can be pushed forward using a protrusion spring (see image below).
The synthetic resin plate with extendable screw is used to widen (expand) the upper tooth arch. The plate is sawn through in the median line and provided with a rotating screw. If the upper jaw needs to be wider, the screw is regularly turned one turn (see image below).
Treatment with an activator is usually chosen for a receding lower jaw. This is a palate plate with a resin extension behind the lower teeth. This device forces the patient to move the lower jaw forward when close (and swallow). This stimulates the growth of the lower jaw and inhibits the forward growth of the upper jaw (see image below).
Extraoral traction is also popularly referred to as “outboard braces”. This includes an internal part (headgear). A headgear consists of an inner bow and an outer bow. The inner arch is in the mouth and is fixed in tubes that are attached to the molars with bands. The outer arch runs outside the mouth along the cheeks. A headcap or neckband is attached to this. This headcap is on top of the head (high-pull headgear) or with a band in the neck (cervical headgear). The location of the extraoral traction (head or neck) and the length of the outer arch determine the direction of pulling on the molars and the rest of the dentition. A headgear inhibits the growth of the upper jaw and moves the molars to distal. This creates more space in the jaw for the teeth (see images below).
A resin plate is more difficult to tolerate in the lower jaw. That is why a lingual arch is often used here. The lingual arch is a thick metal wire, which is attached linguistically to the first permanent under molars. On the first molars, orthodontic bands are cemented with tubes of linguistic. By activating the loops in the thread, the lower molars become distal and the lower front is pushed forward. In this way crowding in the front can be solved and lack of space for the premolars and cuspidate can be eliminated. The lingual arch is not removable for the patient.
Sometimes a lingual arch is placed passively, so without tension, with the aim of retaining the location of the first molars and the space in the dental arch (see image below).
For the same purpose, a stiff metal wire is sometimes applied to the upper jaw, which runs over the palate and is attached to the palatal side of the first remaining molars in orthodontic bands. A palatal bar is also used to move the first molars further to the vestibular.
A lip bumper is a thick metal wire that runs buccally from the lower or upper dental arch and is provided with a synthetic “cushion” at the lip. The arc is mounted on the first remaining molars, which for this purpose are provided with bands with tubes on the buccal surface. The first molars are moved distally by the lip pressure against the cushion. Due to the loss of lip pressure on the front, the front teeth can protrude slightly spontaneously. This creates more room for the premolars and the cuspidate (see image below).
The most commonly used orthodontic equipment is “fixed equipment”. A bracket is cemented on all elements. This bracket is popularly called a block bracket or lock bracket. Around the year 1900 this method of treatment was invented by Edward Angle. He developed a technique that controlled the position of the teeth in all three dimensions with the help of wires (arcs) and clasps on the teeth and molars. This technique has been further developed to this day. A major advantage is that tooth position displacements are therefore much more accurate than with removable equipment. With removable equipment, an element can only be moved by tilting the crown (the root remains practically in place). With fixed equipment it is possible to move an element in its entirety along the wire (bodily movement).
When treating with fixed equipment, the teeth in question are provided with orthodontic bands with a lock (first molars) or with separate brackets that can be glued. A bracket is a metal tube, hook or gutter that is attached to a metal or synthetic resin plate, which is attached to the element in question using the etching technique. A metal wire is attached to the brackets. The most used method nowadays is the “straight wire” technique. That is, the wire that runs along the teeth is straight and that the forward, backward, tipping or rotation of an element is ingrained in the model of the brackets. Loops can also be bent in the wire, which after activation ensure the desired movement of the elements.
Until the mid-eighties of the last century, a wire with (ligature) rubber bands had to be secured in the brackets. Nowadays it is common to clamp this wire with a clip that is already built into the bracket. This type of brackets is called “self-ligating” brackets (see image below).
The wires used in this equipment can have all kinds of special features. You can roughly classify them into different types of material and thicknesses and cross-sectional shapes.
The two most common types of material are nickel titanium (NiTi) wires and stainless steel (stainless steel) wires.
- Nickel titanium arcs, or memory wire, are difficult to bend. Because it retains its shape, it pulls elements that are not in the ideal position to the correct dental arch.
- Stainless steel arches are easy to bend. By bending small steps in the wire, the orthodontist can decide for himself where he wants to move an element.
Regarding cross-section, a subdivision is possible between round wires and square (or rectangular) wires.
- Most tooth movements can be performed with round wires, with the exception of tipping of elements.
- The channel in a bracket is rectangular. By inserting square and rectangular wires here, elements can also be tilted. Retruded and protruded elements can be tilted in the right position.
The thickness can vary from very thin, for example a circular arc with a diameter of 0.012 inch, to a thickness that hardly fits into the slot of the bracket, for example a square thread of 0.021 x 0.021 inch. The thinnest wires are used at the start of treatment with fixed equipment. Later the wires get thicker.
For a number of years, brackets can no longer only be placed on the outside (buccal side) of the elements, but there are also systems where brackets can be placed on the lingual or palatal side. This technique is called linguistic orthodontics.
Every orthodontic device has its limitations. If it is not a limitation in application or in achieving the intended result, then it is the burden that wearing it brings on the patient. Considering that an average orthodontic treatment lasts about two years, it is clear that motivation and perseverance are very important. In addition to wearing a device consistently, optimum oral hygiene is necessary. Many devices cause greater plaque retention. Fixed equipment must be worn, since it cannot be removed by the patient. In terms of handling, this is an advantage over removable equipment. The requirements for oral hygiene in patients treated with fixed equipment must, however, be even stricter than in the case of removable equipment. Good guidance during orthodontic therapy is of great importance.
The patient must frequently come for a check-up during treatment. Depending on the type of equipment and the stage of treatment, the time varies between checks. Progress is monitored in the audit sessions and the equipment is adjusted (activated). Oral hygiene is also checked. Sometimes extra fluoride is recommended as support, for example in the form of a flushing agent.
After some time of active treatment, new alginate prints are made to accurately record the progress of the treatment. It is therefore possible to switch to other equipment.
After the active orthodontic treatment, it is very important to retain the result achieved. Retention equipment is used for this. With retention equipment, the elements are held in place after treatment.
- The best known is a retention plate. This is very similar to plate equipment, except that there are no active (wire) parts in it. There is again a base plate with anchors in it to hold the plate in place. It usually has a labial arch that holds the elements stably in place. Well-known examples are a Vanderlinden retainer or a Hawley retainer.
- In addition to retention equipment that looks like a plate device, there is retention equipment that is made from deep-drawing plates, an invisible retainer. A deep-drawing plate is hereby pressed over the end model (gypsum model after removing the bracket).
- Finally, there is the very commonly used retention splint. This is a metal wire (whether or not consisting of several braided wires) that is placed behind the top or bottom front (see image below).