Mini-implants in orthodontics, also known as temporary anchorage devices, are small screws widely used in orthodontic treatment today. This tool has become popular because it provides a suitable anchor for orthodontics, as it fixes to the bone and then attaches to a tooth or several teeth to pull them in a certain direction during treatment.
Anchorage is a fixed base that provides the force needed to pull a tooth. Before mini-implants in orthodontics and the invention of this method, posterior teeth or external orthodontic instruments were used to create anchors. But the previous anchors had the following limitations:
- Ideally, the anchor should be in place and not move at all. If the pressure increases, the posterior tooth might also move.
- External devices such as retainers also disrupted the patient’s routine life and were not desirable in appearance.
Traditional anchors still work well with dentist management and supervision, but mini-implants in orthodontics can produce more lasting and better results.
Mini-Implant or Mini-Screw in Orthodontics (Anchorage)
Orthodontic appliances, commonly known as braces, are small brackets placed on the tooth using small flexible wires. These small wires put little force on the teeth; Due to their natural nature, wires tend to flatten, and as a result, the teeth move with them. When a low force is applied to the tooth, new bone, ligament, and cementum form at the point of tension or where the tooth is pulled in the pressure section, the cells remove the bone and ligament and allow the tooth to move. Anchorage orthodontics can be a barrier to tooth movement, just like an anchor used to stop a boat from moving. Anchorage consists of teeth or groups of teeth that are fixed to exert forces against other teeth, thereby correcting the movement of teeth that are in an awkward position. The problem is that the anchorage units must always be prevented from moving. If the anchorage units are fixed, the situation becomes much easier. TADS, or Temporary Anchorage Devices, are immovable devices that can be precisely placed in specific locations so that forces can move teeth that need to be moved without moving teeth that do not need to be moved.
What Is Anchorage?
The basis of orthodontic treatment, as you know, is the movement of the teeth. You may think that teeth are strong and immovable pillars, but this is not the case. With orthodontics, many disorders and dislocations and compactions of the teeth are treated. But the point of this treatment is the movement of the teeth that do not need to be replaced. In these cases, a method called anchorage is used. Anchorage can be considered a fixed point in orthodontics. Anchorage means anchor, which is quite similar to the anchorage of a ship and resists movement.
Anchorage Methods in Orthodontics
One of the easiest ways to anchor teeth is to increase the number of teeth and close them in the shape of the English number 8. The contact surface and the number of roots of the teeth affect the size of the anchorage. The amount of anchorage varies with the displacement of single-rooted teeth. It can be said that the force exerted on the teeth is more important than the number of roots of the teeth. The result is that the anchorage size of a single-rooted tooth is smaller than that of three roots.
Extraoral or intraoral devices can be used to control unwanted tooth movement, which may have disadvantages such as patient non-cooperation and anchorage inefficiency. The location of these devices is considered according to the periodontal and biomechanical condition of the teeth.
Temporary Anchor Devices (TADS)
Small screws called mini-screws are inserted into the jawbone and used as a fixed point. They are steel and can be easily removed from the mouth after finishing work. Because these screws are so small, they can only be inserted into the bone by injection.
Up Righting Springs
These springs are used for anchoring in the area of the first premolars with Coil Spring and Nance device to retract the molars. In addition to the resistance of the premolar tooth to mesial forces, they will cause clockwise torque and distal movement of the premolar crown. After placing in the Vertical SLOT, the premolar bracket is activated and causes the root torque to move.
This device, which is used for anchoring teeth, has an acrylic button located in the deepest part of the palette. Its two arcuate sections are welded to the palatal portion of the maxillary molars or inserted into the palatal tubes. It should be noted that the depth and shape of the palette play an important role. If the palette is in the anterior part of the palatal tubes, the Nance device may slip, which is used to maintain deep and narrow palettes. This device should be wide to cover the front of the palette. It may cause perforation of the palate mucosa, in which case sufficient anchorage will not occur. The mucous membrane of the palette is resistant to the Nance device, has a thick keratinized tissue, and is not resistant to high continuous forces. For this reason, there is a possibility of inflammation due to irritation and not observing hygiene.
This device is used with inter-jaw or intra-jaw elastics and is a combination of 0.7 mm wire with a hook that moves along the main wire and transmits the Cl II elastic force directly to the molar tooth.
Cortical anchorage: Teeth are easier to move in the trabecular bone than in the cortex. If the roots of the anchor teeth are in front of the cortical bone, they increase their resistance to movement. Also, the movement of the Lingual Root Torque in the mandibular canine teeth makes it easier to move backward.
Extraoral devices are also very suitable for this purpose. Approximately 300 to 350 grams of force is required to prevent movement to the front of the posterior teeth. Cervical retainers and High Pull retainers are extra-oral devices that are used when necessary. The retainer strap is placed on the patient’s chin or forehead and should be used for 12 hours daily. The blockers have the problem that they are very dependent on the patient’s cooperation. If the patient does not have the necessary cooperation, the treatment will not be successful.