The main action of power best dental ultrasonic scaler is mechanical; the high vibrational energy crushes and removes calculus. Other actions include: creating shockwaves that disrupt bacterial cells, or using turbulence to disrupt biofims, and irrigation — the therapeutic washing and flushing of the periodontal pocket and root surface with cooling water. Both power and hand scaling techniques require an experienced clinician with good tactile sensitivity (sense of touch) to remove deposits effectively and to promote healing.
Pros And Cons Of Power Driven Scalers
Research shows power scaling instruments have advantages:
They are as effective as manual instruments for calculus removal in shallow gum pockets and significantly more effective in pockets greater than 4mm.
They are very effective in disrupting biofilm from root surfaces and from within periodontal pockets making them especially helpful when patients require frequent maintenance (cleanings).
Specially designed tips can penetrate deeper into periodontal pockets than manual instruments and are more effective at cleaning difficult nooks and crannies like furcations, (areas where roots join each other in multi-rooted teeth).
When used correctly they are kinder to tooth structure, which is especially important with repeated cleanings (when used correctly).
Coolant sprays provide irrigation (flushing of the area), which improves healing by removing bacteria and their bi-products as well as the hygienist's ability to see when scaling.
They require less time than manual instruments for the same job.
Their smaller tips cause less tissue distention and require very little pressure — thus making it more comfortable for you, the patient!
Cautions Regarding Power Scalers
Aerosol production (the formation of contaminated “mist”) requires protective equipment; not a problem for experienced dental professionals.
Power scalers may affect certain cardiac (heart) pacemakers! Although most modern pacemakers are shielded, tell your dentist and/or hygienist if you have one.
Ultrasonic power scalers are not recommended for individuals with hypersensitive teeth, which may include primary teeth or newly erupted teeth. Please tell your dentist or hygienist if your teeth are sensitive to temperature change.
Ultrasonic scalers are also not recommended for areas of demineralization (early mineral loss leading to decay), porcelain or composite restorations and titanium implants — unless specially designed tips are used which won't scratch them.
Most periodontal experts today agree that the best results for non-surgical periodontal therapy are achieved by a blended approach; the combined use of power ultrasonic scalers and hand instruments. Rapidly changing technology has revolutionized periodontal therapy with integration of power scaling techniques resulting in improved clinical outcomes, patient comfort, and reduced time and physical demands on clinicians.
See more at: http://www.oyodental.com/
Wednesday, February 10, 2016
Sunday, February 7, 2016
An Overview of Current Technology OF Dental Handpiece
Electric Dental Handpiece are rapidly replacing traditional air-driven, high-speed handpieces in the US market. Industry estimates indicate that only 20% of practices employ an electric handpiece for restorative treatment, whereas in the European market over 80% of restorative practices are employing electric handpieces to prepare teeth for restorations. Practitioners who have tried electric handpieces become quick converts to the benefits of preparing a tooth for a crown with an electric handpiece.
Speed and Torque
Two factors to understand when comparing air-driven vs electric handpieces are speed and torque. Speed is expressed in revolutions per minute (rpm), whereas torque is expressed in watts and is an indication of the tool’s cutting power. Air-driven high-speed handpieces typically will have speeds between 250,000 and 420,000 rpm but the torque is relatively low, whereas an electric handpiece may have speeds around 200,000 rpm but relatively high torque. This implies that air-driven handpieces are faster than electric handpieces. However, when a bur in an air-driven handpiece contacts material to be cut, the speed will drop by as much as 40% or more (depending on the hardness of the material) because as resistance builds during cutting, the air pressure is insufficient to maintain the speed of rotation of the turbine. The harder the material being cut, the more resistance is created and the slower the bur spins. Our instinctive reaction is to place more pressure upon the bur to get it to cut the material, which increases resistance even further, creating a vicious circle.
An electric handpiece offers smooth, constant torque that does not vary as the bur meets resistance. With electric handpieces, the bur is connected through gears in the head of the handpiece to a central drive shaft that is physically turned by the motor. Because of the absence of air, these handpieces are quieter and the chance of air embolism in a surgical site is eliminated. Thus, the power output with electric handpieces is greater than with air-driven handpieces, offering 33 to 45 watts of cutting power. Because the speed and torque are constant, removing difficult crowns, bridges, and restorations becomes easier. Electric motors also offer accuracy by enabling the end user to set precise speeds for procedures, rather than the conventional “feathering” of the rheostat. Another difference between air and electric handpieces to consider is that in electric handpieces, power output is not dependent on head size. Some manufacturers offer smaller-head handpieces that may be beneficial in pedodontic applications or when operating in the posterior in confined spaces (Figure 1).
Cutting efficiency is actually a balance between the speed and torque delivered to the bur. A good way to demonstrate this is the “penny test.” Take a penny and grasp one end with a pair of locking hemostats to stabilize the penny. Next, using a carbide bur in the handpiece, cut a slot in the penny. Typically, the air-driven handpiece will bog down as it attempts to cut the slot and may stall as increasing pressure is placed on the bur. The electric handpiece will demonstrate smooth, even cutting without bogging down. This test is a good demonstration of how the handpiece may act clinically when preparing a tooth with an amalgam core or cutting a slot in a nonprecious crown to aid in its removal.
Understanding Gear Ratios
Electric handpieces will have a gear ratio imprinted on the handpiece which helps identify what procedures are best performed with that particular gear ratio. The ratio is expressed as X:Y, with a high-speed handpiece having a 1:5 ratio, and those intended for slow-speed procedures having a ratio expressed as 1:1. Some companies also offer handpieces for “ultra” slow-speed procedures such as pin placement or endodontics with a gear ratio of 10:1 or 16:1.
Typical procedures done with a high-speed (1:5) handpiece would be cavity preparation, crown preparation, and sectioning existing fixed prosthetics. These high-speed handpieces accept standard friction-grip burs or diamonds and push-button bur chucks. Slow-speed (1:1) handpieces would be indicated for caries removal, preparation refinement, and adjustment of ceramics. Depending on the manufacturer, slow-speed heads are available in either a friction-grip or latch-grip. The benefit of a friction-grip slow-speed head is any bur that can be used in a high-speed can be alternatively used in a slow-speed. Additionally, friction-grip burs typically retail for less than half the cost of latch-grip burs and diamonds are only offered in friction-grip applications.
Couplings and Connectors
Currently, all electric handpieces offer the standardized ISO coupling between motor and attachment (also called electric or universal coupling). The abbreviation for this universal electric connector is termed an “E” connector. The benefit of this is that most electric handpieces will fit any manufacturer’s motor. The exception is the Star Dental (Lancaster, PA) connector, which has a variation on the aligning tab used to line up the fiber optics that differs from the standard alignment tab. This variation presents as a round tab on the motor end and a corresponding round dimple on the handpiece. The standardized E connector that is used by other manufacturers presents with a rectangular depression on the motor with a corresponding tab on the handpiece. But before switching to a different brand of handpiece than the motor’s manufacturer, make sure that if the handpiece is lighted that the optics connection in the coupling will work with your current motor cable (Figure 2).
Sirona also offers a propriety connector in addition to its standard E connector. This connector places the motor deeper within the handpiece. Practitioners with smaller hands may find the balance more efficient (china dental supplier).
Warranties
Warranties can be confusing in terms of understanding what exactly is covered and for what period of time. Most handpiece companies will warrant the handpiece for at least 1 year. Warranties may be extended and the manufacturer should be contacted for further information on the details. Extended warranties often require use of that company’s lubricant and some require use of their particular lubricating unit.
One aspect to understand is the warranty on the handpieces optics. Current glass-rod technology (fused bundle) is very durable. Most manufacturers provide a 5-year warranty on the optics. Glass rods basically do not deteriorate under repeated sterilization cycles. However, if you drop the handpiece and the rod breaks, typically manufacturers will consider this a void in the warranty and the owner of the handpiece will need to cover any repair costs. Therefore, extended warranties on the glass rods is more or less a marketing tool.
- See more at: http://www.chinadentalsupplier.com/
Speed and Torque
Two factors to understand when comparing air-driven vs electric handpieces are speed and torque. Speed is expressed in revolutions per minute (rpm), whereas torque is expressed in watts and is an indication of the tool’s cutting power. Air-driven high-speed handpieces typically will have speeds between 250,000 and 420,000 rpm but the torque is relatively low, whereas an electric handpiece may have speeds around 200,000 rpm but relatively high torque. This implies that air-driven handpieces are faster than electric handpieces. However, when a bur in an air-driven handpiece contacts material to be cut, the speed will drop by as much as 40% or more (depending on the hardness of the material) because as resistance builds during cutting, the air pressure is insufficient to maintain the speed of rotation of the turbine. The harder the material being cut, the more resistance is created and the slower the bur spins. Our instinctive reaction is to place more pressure upon the bur to get it to cut the material, which increases resistance even further, creating a vicious circle.
An electric handpiece offers smooth, constant torque that does not vary as the bur meets resistance. With electric handpieces, the bur is connected through gears in the head of the handpiece to a central drive shaft that is physically turned by the motor. Because of the absence of air, these handpieces are quieter and the chance of air embolism in a surgical site is eliminated. Thus, the power output with electric handpieces is greater than with air-driven handpieces, offering 33 to 45 watts of cutting power. Because the speed and torque are constant, removing difficult crowns, bridges, and restorations becomes easier. Electric motors also offer accuracy by enabling the end user to set precise speeds for procedures, rather than the conventional “feathering” of the rheostat. Another difference between air and electric handpieces to consider is that in electric handpieces, power output is not dependent on head size. Some manufacturers offer smaller-head handpieces that may be beneficial in pedodontic applications or when operating in the posterior in confined spaces (Figure 1).
Cutting efficiency is actually a balance between the speed and torque delivered to the bur. A good way to demonstrate this is the “penny test.” Take a penny and grasp one end with a pair of locking hemostats to stabilize the penny. Next, using a carbide bur in the handpiece, cut a slot in the penny. Typically, the air-driven handpiece will bog down as it attempts to cut the slot and may stall as increasing pressure is placed on the bur. The electric handpiece will demonstrate smooth, even cutting without bogging down. This test is a good demonstration of how the handpiece may act clinically when preparing a tooth with an amalgam core or cutting a slot in a nonprecious crown to aid in its removal.
Understanding Gear Ratios
Electric handpieces will have a gear ratio imprinted on the handpiece which helps identify what procedures are best performed with that particular gear ratio. The ratio is expressed as X:Y, with a high-speed handpiece having a 1:5 ratio, and those intended for slow-speed procedures having a ratio expressed as 1:1. Some companies also offer handpieces for “ultra” slow-speed procedures such as pin placement or endodontics with a gear ratio of 10:1 or 16:1.
Typical procedures done with a high-speed (1:5) handpiece would be cavity preparation, crown preparation, and sectioning existing fixed prosthetics. These high-speed handpieces accept standard friction-grip burs or diamonds and push-button bur chucks. Slow-speed (1:1) handpieces would be indicated for caries removal, preparation refinement, and adjustment of ceramics. Depending on the manufacturer, slow-speed heads are available in either a friction-grip or latch-grip. The benefit of a friction-grip slow-speed head is any bur that can be used in a high-speed can be alternatively used in a slow-speed. Additionally, friction-grip burs typically retail for less than half the cost of latch-grip burs and diamonds are only offered in friction-grip applications.
Couplings and Connectors
Currently, all electric handpieces offer the standardized ISO coupling between motor and attachment (also called electric or universal coupling). The abbreviation for this universal electric connector is termed an “E” connector. The benefit of this is that most electric handpieces will fit any manufacturer’s motor. The exception is the Star Dental (Lancaster, PA) connector, which has a variation on the aligning tab used to line up the fiber optics that differs from the standard alignment tab. This variation presents as a round tab on the motor end and a corresponding round dimple on the handpiece. The standardized E connector that is used by other manufacturers presents with a rectangular depression on the motor with a corresponding tab on the handpiece. But before switching to a different brand of handpiece than the motor’s manufacturer, make sure that if the handpiece is lighted that the optics connection in the coupling will work with your current motor cable (Figure 2).
Sirona also offers a propriety connector in addition to its standard E connector. This connector places the motor deeper within the handpiece. Practitioners with smaller hands may find the balance more efficient (china dental supplier).
Warranties
Warranties can be confusing in terms of understanding what exactly is covered and for what period of time. Most handpiece companies will warrant the handpiece for at least 1 year. Warranties may be extended and the manufacturer should be contacted for further information on the details. Extended warranties often require use of that company’s lubricant and some require use of their particular lubricating unit.
One aspect to understand is the warranty on the handpieces optics. Current glass-rod technology (fused bundle) is very durable. Most manufacturers provide a 5-year warranty on the optics. Glass rods basically do not deteriorate under repeated sterilization cycles. However, if you drop the handpiece and the rod breaks, typically manufacturers will consider this a void in the warranty and the owner of the handpiece will need to cover any repair costs. Therefore, extended warranties on the glass rods is more or less a marketing tool.
- See more at: http://www.chinadentalsupplier.com/
Friday, February 5, 2016
The difference between a DC micro motor and servo micro motor
A DC motor has a two wire connection. All drive power is supplied over these two wires—think of a light bulb. When you turn on a DC motor, it just starts spinning round and round. Most DC motors are pretty fast, about 5000 RPM (revolutions per minute).
With the DC marathon micro motor, its speed (or more accurately, its power level) is controlled using a technique named pulse width modulation, or simply PWM. This is idea of controlling the motor’s power level by strobing the power on and off. The key concept here is duty cycle—the percentage of “on time” versus“off time.” If the power is on only 1/2 of the time, the motor runs with 1/2 the power of its full-on operation.
If you switch the power on and off fast enough, then it just seems like the motor is running weaker—there’s no stuttering. This is what PWM means when referring to DC motors. The Handy Board’s DC motor power drive circuits simply switch on and off, and the motor runs more slowly because it’s only receiving power for 25%, 50%, or some other fractional percentage of the time.
A servo motor is an entirely different story. The servo motor is actually an assembly of four things: a normal DC motor, a gear reduction unit, a position-sensing device (usually a potentiometer—a volume control knob), and a control circuit.
The function of the servo is to receive a control signal that represents a desired output position of the servo shaft, and apply power to its DC motor until its shaft turns to that position. It uses the position-sensing device to determine the rotational position of the shaft, so it knows which way the motor must turn to move the shaft to the commanded position. The shaft typically does not rotate freely round and round like a DC motor, but rather can only turn 200 degrees or so back and forth.
The servo has a 3 wire connection: power, ground, and control. The power source must be constantly applied; the servo has its own drive electronics that draw current from the power lead to drive the motor.
The control signal is pulse width modulated (PWM), but here the duration of the positive-going pulse determines the position of the servo shaft. For instance, a 1.520 millisecond pulse is the center position for a Futaba S148 servo. A longer pulse makes the servo turn to a clockwise-from-center position, and a shorter pulse makes the servo turn to a counter-clockwise-from-center position.
The servo control pulse is repeated every 20 milliseconds. In essence, every 20 milliseconds you are telling the servo, “go here.”
To recap, there are two important differences between the control pulse of the servo motor versus the DC motor. First, on the servo motor, duty cycle (on-time vs. off-time) has no meaning whatsoever—all that matters is the absolute duration of the positive-going pulse, which corresponds to a commanded output position of the servo shaft. Second, the servo has its own power electronics, so very little power flows over the control signal. All power is draw from its power lead, which must be simply hooked up to a high-current source of 5 volts.
Contrast this to the DC brushless micro motor. On the Handy Board, there are specific motor driver circuits for four DC motors. Remember, a DC motor is like a light bulb; it has no electronics of its own and it requires a large amount of drive current to be supplied to it. This is the function of the L293D chips on the Handy Board, to act as large current switches for operating DC motors.
Plans and software drivers are given to operate two servo motors from the HB. This is done simply by taking spare digital outputs, which are used to generate the precise timing waveform that the servo uses as a control input. Very little current flows over these servo control signals, because the servo has its own internal drive electronics for running its built-in motors.
With the DC marathon micro motor, its speed (or more accurately, its power level) is controlled using a technique named pulse width modulation, or simply PWM. This is idea of controlling the motor’s power level by strobing the power on and off. The key concept here is duty cycle—the percentage of “on time” versus“off time.” If the power is on only 1/2 of the time, the motor runs with 1/2 the power of its full-on operation.
If you switch the power on and off fast enough, then it just seems like the motor is running weaker—there’s no stuttering. This is what PWM means when referring to DC motors. The Handy Board’s DC motor power drive circuits simply switch on and off, and the motor runs more slowly because it’s only receiving power for 25%, 50%, or some other fractional percentage of the time.
A servo motor is an entirely different story. The servo motor is actually an assembly of four things: a normal DC motor, a gear reduction unit, a position-sensing device (usually a potentiometer—a volume control knob), and a control circuit.
The function of the servo is to receive a control signal that represents a desired output position of the servo shaft, and apply power to its DC motor until its shaft turns to that position. It uses the position-sensing device to determine the rotational position of the shaft, so it knows which way the motor must turn to move the shaft to the commanded position. The shaft typically does not rotate freely round and round like a DC motor, but rather can only turn 200 degrees or so back and forth.
The servo has a 3 wire connection: power, ground, and control. The power source must be constantly applied; the servo has its own drive electronics that draw current from the power lead to drive the motor.
The control signal is pulse width modulated (PWM), but here the duration of the positive-going pulse determines the position of the servo shaft. For instance, a 1.520 millisecond pulse is the center position for a Futaba S148 servo. A longer pulse makes the servo turn to a clockwise-from-center position, and a shorter pulse makes the servo turn to a counter-clockwise-from-center position.
The servo control pulse is repeated every 20 milliseconds. In essence, every 20 milliseconds you are telling the servo, “go here.”
To recap, there are two important differences between the control pulse of the servo motor versus the DC motor. First, on the servo motor, duty cycle (on-time vs. off-time) has no meaning whatsoever—all that matters is the absolute duration of the positive-going pulse, which corresponds to a commanded output position of the servo shaft. Second, the servo has its own power electronics, so very little power flows over the control signal. All power is draw from its power lead, which must be simply hooked up to a high-current source of 5 volts.
Contrast this to the DC brushless micro motor. On the Handy Board, there are specific motor driver circuits for four DC motors. Remember, a DC motor is like a light bulb; it has no electronics of its own and it requires a large amount of drive current to be supplied to it. This is the function of the L293D chips on the Handy Board, to act as large current switches for operating DC motors.
Plans and software drivers are given to operate two servo motors from the HB. This is done simply by taking spare digital outputs, which are used to generate the precise timing waveform that the servo uses as a control input. Very little current flows over these servo control signals, because the servo has its own internal drive electronics for running its built-in motors.
Monday, February 1, 2016
Form des Arbeitsteils, Anwendungsgebiete und Drehzahlen
Stahl und Hartmetall
Nahezu alle Instrumentenformen stehen in unterschiedlichen Größen zur Verfügung, die nach ISO 2157 klassifiziert sind.
Eines der meisteingesetzten und vielseitigsten Instrumente ist der Rundbohrer, der auch als Rosenbohrer bezeichnet wird. Dieser sowie der Radbohrer, der umgekehrte Kegel, die Fissurenbohrer und weitere hier nicht abgebildete Stahl- oder Hartmetallbohrer werden zum Exkavieren (Entfernen oder „Ausbohren“ kariöser Zahnhartsubstanzen) eingesetzt, wobei Radbohrer und umgekehrte Kegel insbesondere dazu dienen, Unterschnitte zur Verankerung plastischen Füllungsmaterials zu präparieren. Aber auch Metalle und Kunststoffe können damit bearbeitet werden.
Diamanten
Diamanten sind dazu geeignet, auch den sehr harten Zahnschmelz zu bearbeiten. Sie dienen deshalb vor allem der Präparation von Füllungskavitäten und Zähnen zur Aufnahme von Kronen. Es sind Diamanten unterschiedlicher Körnung auf dem Markt. Damit kann z.B. ein Zahnstumpf vor der Abformung geglättet werden können. Viele Hersteller markieren die Körnung mit Farbringen.
Keramische Schleifkörper
Keramische Schleifkörper (rotierende instrumente dental) werden verwendet, um Werkstücke (besonders Modellgussprothesen und andere (Edel-)Metallarbeiten) auszuarbeiten und zu glätten. Sie stehen in unterschiedlicher Körnung zur Verfügung, die durch ihre Farbgebung zu erkennen ist. Auch natürliche Zähne und Zahnersatz lassen sich mit keramischen Schleifkörper gut bearbeiten, um z. B. die Okklusion zu korrigieren.
Elastische Polierer
Elastische Polierer (auch Gummipolierer genannt) werden als letzter Schritt bei der Ausarbeitung vor der Hochglanzpolitur mit Polierpaste eingesetzt. Das Werkstück kann dabei sehr heiß werden.
Ihre optimale Wirkung erzielen sie je nach Körnung und Werkstück bei einer Drehzahl zwischen 5.000 min−1 und 20.000 min−1.
Weitere Formen
Es gibt eine Fülle weiterer Formen für jedweden Zweck zahnärztlichen und zahntechnischen Arbeitens: Scheibenförmig, knospenförmig, birnenförmig, linsenförmig, flammenförmig, kelchförmig etc. Auch Mandrelle als Träger für (diamantierte) Trennscheiben und Schmirgelpapierträger sowie Filzkegel, Ziegenhaarbürsten und Leinenschwabbeln als Träger für Bimspulver und Polierpasten stehen zur Verfügung.
mehr sehen:
http://www.oyodental.de/
Nahezu alle Instrumentenformen stehen in unterschiedlichen Größen zur Verfügung, die nach ISO 2157 klassifiziert sind.
Eines der meisteingesetzten und vielseitigsten Instrumente ist der Rundbohrer, der auch als Rosenbohrer bezeichnet wird. Dieser sowie der Radbohrer, der umgekehrte Kegel, die Fissurenbohrer und weitere hier nicht abgebildete Stahl- oder Hartmetallbohrer werden zum Exkavieren (Entfernen oder „Ausbohren“ kariöser Zahnhartsubstanzen) eingesetzt, wobei Radbohrer und umgekehrte Kegel insbesondere dazu dienen, Unterschnitte zur Verankerung plastischen Füllungsmaterials zu präparieren. Aber auch Metalle und Kunststoffe können damit bearbeitet werden.
Diamanten
Diamanten sind dazu geeignet, auch den sehr harten Zahnschmelz zu bearbeiten. Sie dienen deshalb vor allem der Präparation von Füllungskavitäten und Zähnen zur Aufnahme von Kronen. Es sind Diamanten unterschiedlicher Körnung auf dem Markt. Damit kann z.B. ein Zahnstumpf vor der Abformung geglättet werden können. Viele Hersteller markieren die Körnung mit Farbringen.
Keramische Schleifkörper
Keramische Schleifkörper (rotierende instrumente dental) werden verwendet, um Werkstücke (besonders Modellgussprothesen und andere (Edel-)Metallarbeiten) auszuarbeiten und zu glätten. Sie stehen in unterschiedlicher Körnung zur Verfügung, die durch ihre Farbgebung zu erkennen ist. Auch natürliche Zähne und Zahnersatz lassen sich mit keramischen Schleifkörper gut bearbeiten, um z. B. die Okklusion zu korrigieren.
Elastische Polierer
Elastische Polierer (auch Gummipolierer genannt) werden als letzter Schritt bei der Ausarbeitung vor der Hochglanzpolitur mit Polierpaste eingesetzt. Das Werkstück kann dabei sehr heiß werden.
Ihre optimale Wirkung erzielen sie je nach Körnung und Werkstück bei einer Drehzahl zwischen 5.000 min−1 und 20.000 min−1.
Weitere Formen
Es gibt eine Fülle weiterer Formen für jedweden Zweck zahnärztlichen und zahntechnischen Arbeitens: Scheibenförmig, knospenförmig, birnenförmig, linsenförmig, flammenförmig, kelchförmig etc. Auch Mandrelle als Träger für (diamantierte) Trennscheiben und Schmirgelpapierträger sowie Filzkegel, Ziegenhaarbürsten und Leinenschwabbeln als Träger für Bimspulver und Polierpasten stehen zur Verfügung.
mehr sehen:
http://www.oyodental.de/
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