Instrumentos Rotatorios

Currently, there are devices, such as dental turbines or contra-angles, that are essential elements within the equipment that makes up a dental clinic's instrumentation. There are two types of systems for propelling the bur with which work is performed using these types of instruments:

• By electricity, through a micromotor, with different speeds (which can be up to 200,000 r.p.m.) that make this a very versatile instrument depending on the procedure, being constant, without decreasing resistance, with which great performance and flexibility in work are achieved, since precision is much higher. One of the main advantages of devices with this system is that the head diameter is slightly smaller, a better viewing angle is achieved, and as a result, a better preparation area. In addition, they tend to be quieter, with a lower sensation of vibration, which reduces patient stress. These types of devices are currently equipped with LED light, which provides an additional advantage. Among the disadvantages of this system are that the head of the instruments can become excessively overheated, and they tend to be heavier instruments with a risk of applying excessive pressure on the tooth (although there are cases in which this is beneficial for the dentist, as it allows for a much firmer and more secure grip of the device).
• By compressed air, through a micromotor with which a speed of around 400,000 r.p.m. is reached, which translates into faster cuts and a considerable reduction in work time, but which considerably decreases the performance of the bur's use. Another advantage to highlight of this system is the improvement in its design, as they are lighter, and the smaller the head size, the easier its handling is and the better accessibility is achieved. They also have a lower probability of being damaged, and in case this happens, the cost of repairs is lower than that of electric devices. Conversely, many models of devices emit much greater noise and vibrations, which makes them more annoying and uncomfortable for the patient.

Dental Turbines

Dental turbines are the rotary instruments that reach the highest speed. This can even exceed 400,000 r.p.m. (although it should be noted that working speeds are usually lower, and do not exceed 300,000 r.p.m.), but with a torque that, in addition to being stable, is easy to control.

Due to the high speed reached by the rotors of the heads in this type of instrument, high heat is generated by friction, which must be controlled through cooling and air and water irrigation systems.

Turbines are usually used especially for performing any type of treatment that is more rigorous, such as the removal of the most resistant tissue in teeth, carving and removals in restoration, or cavity preparations. Other uses for turbines can be crown preparation, polishing excess composite, or removing carious materials from the tooth.

Parts of a turbine:

• The head is the area where the bur is placed, with different types of clamping (depending on the manufacturer). The smaller the turbine head, the better access and visualization are achieved, at the expense of lower power. It has a propeller inside (in some cases there can be up to two propellers, in order to achieve more power). In order to avoid possible contamination of the air that is absorbed by the rotor, there are currently turbines that already incorporate a hygienic type head, with ducts that divert the entry of that air coming from the outside.
• The bodies of these instruments, whose design is angled to achieve easier access to the patient's mouth, are areas with rough surfaces, which facilitates their grip. In their lower part are the devices that join the equipment hose, in order to receive the connection and return of air (which is captured by the impeller -a part of the rotor, which is included in the head- to make the turbine spin when it comes out compressed) and water. In case both parts are different, the use of an adapter is necessary.

For this reason, when choosing a turbine, it is very important to take into account its type of connection, both for compatibility with dental chairs and for its characteristics, among which two main types of connections can be distinguished:

Integrated or direct type to the dental chair hose, and which, therefore, does not need couplings. However, they require that they be completely disconnected to be able to perform their sterilization or be replaced, and furthermore, they do not allow the 360º free rotation of the turbine. Its great advantage is that air loss in the adapters is non-existent.

Quick adapters have the advantage that the turbines can be connected and disconnected instantly, without having to unscrew the entire instrument from the hose. They are available with and without LED light. Almost any brand of dental turbine currently has quick adapters compatible with its models on the market, but the most widespread adapters compatible with the rest are the Multiflex Couplings (from Kavo).

Turbine connections to the hose usually use mainly two systems:

• Midwest, which has four holes or 6 holes if the hose has light
• or Borden, with two holes or 3 holes if the hose has light.

In both cases, the holes serve as outlets for air and water (there are also adapters for the dental chair hose terminals that are not identical to the one available).

Dental Contra-angles

These are rotary instruments focused on performing surface cleaning in prophylaxis, for excavating deep caries, or for polishing and finishing any type of restoration. For this and other reasons, the speeds of contra-angles are usually quite more moderate than those of turbines, but the torque (and therefore the force generated) is more controlled.

Their characteristic angulation makes it much more favorable to access the patient's mouth.

Contra-angles have two main parts: the head, where the bur is placed and held (which is usually made of steel or tungsten carbide, as they are less abrasive and have less cutting power compared to diamond ones) and the handle, which incorporates a micromotor, responsible for the movement.

Depending on the transmission power of the micromotor to the head, contra-angles are usually classified, for their distinction, with a colored ring that identifies them:

• Blue: These are direct transmission instruments (1:1) in which the speed generated by the micromotors is identical to that received by the bur (around 20,000 r.p.m.). Among other uses, they stand out for caries removal, polishing at reduced and controlled speed, and placing root posts.
• Red: These are multiplier type instruments (1:5) in which the speed received by the bur is higher than that generated by the micromotor (around 20,000 r.p.m. generated, which are increased about five times more, to about 100,000 r.p.m.). These contra-angles are usually used for metal carving (since turbine burs are usually used), for performing polishing at high speed, any cavity conformation work,...
• Green: These are reduction or de-multiplier instruments, in which the speed is reduced from the micromotor to the bur:
• Around five times less (5:1) and they usually go from generating about 20,000 r.p.m. to about 4,000 r.p.m. output, which is ideal for performing any type of more precise work in cases of conservative dentistry and endodontics.
• Around twenty times less (20:1) and they usually go from generating about 40,000 r.p.m. to about 2,000 r.p.m. output, which means a great reduction in generated heat, which is ideal for very precise work such as placing dental implants or certain surgical practices.