CN113384366A

CN113384366A - Dental handpiece and root canal preparation machine thereof

Info

Publication number: CN113384366A
Application number: CN202110642985.8A
Authority: CN
Inventors: 吴坤优; 寺内吉継; 鲁成旺; 陈浩然; 韦锋文; 黄永朝; 徐家振; 龙忠实
Original assignee: Guilin Woodpecker Medical Instruments Co Ltd
Current assignee: Guilin Woodpecker Medical Instruments Co Ltd
Priority date: 2021-06-09
Filing date: 2021-06-09
Publication date: 2021-09-14

Abstract

The embodiment of the invention provides a dental handpiece and a handpiece and root canal preparation machine thereof, relating to the technical field of medical instruments.A handpiece of the dental handpiece comprises a handpiece shell, wherein a core cavity is arranged in the handpiece shell, and a rotatable movement and a driving gear are arranged in the core cavity; the driving gear is sleeved at one end of the machine core, and the machine core can move along the axial direction of the driving gear; the inner cavity of the machine core is also provided with a reciprocating driving mechanism which is used for driving the machine core to reciprocate along the self axial direction. From this, when using the dental handpiece of this embodiment to carry out root canal therapy, through reciprocal actuating mechanism drive root canal file along self axial reciprocating motion, no longer need manual drawing to improve the treatment effeciency that the root canal enlarges, reduced the requirement to patient's cavity space, the operation of the root canal enlargement treatment of also being convenient for has improved the experience sense of patient's treatment.

Description

Dental handpiece and root canal preparation machine thereof

Technical Field

The invention relates to the technical field of medical instruments, in particular to a dental handpiece, a handpiece head and a root canal preparation machine thereof.

Background

The oral root canal therapy comprises root canal length measurement, root canal enlargement and then root canal filling; in the course of the root canal enlargement operation, it is necessary to enlarge the damaged or clogged root canal of the tooth using a root canal preparation machine. The root canal enlarging method is to clamp the root canal file onto the bending machine of the root canal preparation machine and then to dredge and enlarge the root canal with the bending machine.

The inventor researches and discovers that the existing bending mobile phone core is driven by a driving shaft to rotate, so that the bending mobile phone needs to be repeatedly lifted and pulled when the root canal is enlarged and treated, and the operation efficiency is low; and the oral cavity of the patient is small, and particularly when the back teeth are made, the lifting space is small, and the operation is inconvenient.

Disclosure of Invention

The invention aims to provide a handpiece of a dental handpiece, which can drive a machine core to rotate and drive the machine core to reciprocate along the axial direction of the machine core, and does not need to repeatedly lift a curved handpiece during root canal enlargement treatment so as to facilitate root canal enlargement operation and improve the efficiency of the root canal enlargement operation.

The embodiment of the invention is realized by the following steps:

in a first aspect, the invention provides a handpiece of a dental handpiece, which comprises a handpiece shell, wherein a handpiece cavity is arranged in the handpiece shell, and a rotatable movement and a driving gear are arranged in the movement cavity;

the driving gear is sleeved at one end of the machine core, and the machine core can axially move along the driving gear;

and a reciprocating driving mechanism is further arranged in the core cavity and used for driving the core to axially reciprocate along the core.

In an alternative embodiment, the reciprocating drive mechanism is a cam mechanism, and comprises a drive block, a drive protrusion and an elastic piece;

the driving block is positioned at one end of the movement cavity far away from the driving gear, and an annular driving surface coaxial with the movement is arranged on the end surface of the driving block close to the driving gear, wherein the distance between the driving surface and the driving gear gradually changes along the circumferential direction of the driving block;

the driving bulge is arranged on the machine core and points to the driving surface;

the elastic piece is used for enabling the driving protrusion to be always abutted against the driving surface.

In an optional embodiment, the elastic member is sleeved outside the movement and abuts against between the driving gear and the movement.

In an alternative embodiment, the drive surface is a chamfer.

In an alternative embodiment, the reciprocating drive mechanism is a cam mechanism, comprising a drive block and a drive projection;

the two driving blocks are oppositely arranged and are sleeved on the machine core, an annular driving groove is formed between the two driving blocks, and the distance between the driving groove and the driving gear gradually changes along the circumferential direction of the driving blocks;

the driving protrusion is arranged on the movement, at least partially extends into the driving groove, and can move relative to the driving groove.

In an alternative embodiment, the reciprocating drive mechanism is a cam mechanism, and comprises a movement sleeve and a drive protrusion;

the movement sleeve is sleeved on the movement, a driving groove which surrounds the inner wall of the movement sleeve in the circumferential direction is formed in the inner wall of the movement sleeve, and the distance between the driving groove and the driving gear gradually changes along the circumferential direction of the movement sleeve;

the driving bulge is arranged on the movement, at least partially extends into the driving groove, and can move relative to the driving groove.

In an optional embodiment, one end of the driving protrusion, which is positioned in the driving groove, is sleeved with a roller; and/or

The shapes of two opposite side surfaces in the width direction of the driving groove are matched and are inclined planes.

In an alternative embodiment, a pre-tightening spring is arranged in one end of the movement cavity away from the driving gear, and the pre-tightening spring is used for pressing the reciprocating driving mechanism to the driving gear.

In a second aspect, the present invention provides a dental handpiece, a handpiece of a dental handpiece as described in any one of the preceding embodiments.

In a third aspect, the present invention provides a root canal preparation machine comprising a dental handpiece as described in the previous embodiments.

The embodiment of the invention has the beneficial effects that:

the machine core is arranged in the machine core cavity of the machine head shell, and one end of the machine core is provided with the driving gear which is in transmission connection with the transmission shaft, so that the rotary driving torque of the motor is transmitted to the driving gear through the transmission shaft, and the machine core is driven to rotate; the machine core can move along the axial direction of the driving gear, meanwhile, a reciprocating driving mechanism is also arranged in the cavity of the machine core, and the reciprocating driving mechanism drives the machine core to reciprocate along the axial direction of the machine core, so that the machine core does reciprocating movement while rotating. When the movement clamping root canal file, can drive the root canal file rotation and drive the root canal file along root canal file axial reciprocating motion through the movement. Therefore, when the aircraft nose that uses this dental handpiece carries out root canal enlargement, through reciprocal actuating mechanism drive root canal file along root canal file axial reciprocating motion, do not need manual drawing cell-phone to improve the treatment effeciency that the root canal enlarges, reduced the requirement to patient's cavity space, the operation of the root canal enlargement treatment of also being convenient for has improved the experience sense of patient's treatment.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a schematic view of a dental handpiece in accordance with a first embodiment of the present invention;

FIG. 2 is an enlarged view of portion A of FIG. 1;

FIG. 3 is a schematic view of a dental handpiece in accordance with a second embodiment of the present invention;

FIG. 4 is an enlarged view of the portion B of FIG. 3;

FIG. 5 is a schematic view of the section C-C of FIG. 4;

FIG. 6 is a schematic view of a dental handpiece in accordance with a third embodiment of the present invention;

FIG. 7 is an enlarged view of section C of FIG. 6;

fig. 8 is a schematic view of a cartridge barrel according to a third embodiment of the present invention, from a first perspective;

fig. 9 is a schematic view of a cartridge barrel according to a third embodiment of the present invention from a second perspective.

10-handpiece shell; 101-a core cavity; 102-a movement; 103-a drive gear; 104-a drive shaft; 105-a first pole segment; 106-a second pole segment; 107-connecting shaft; 108-a drive block; 1081-a drive slot; 109-a drive projection; 110-an elastic member; 111-pre-tightening the spring; 112-movement sleeve; 1121-piercing; 20-root canal file.

Detailed Description

In the dental operation, the mode of root canal expansion is with the root canal file clamping on the bending machine of root canal preparation machine, and current bending machine core is rotary motion through the drive shaft drive, consequently uses the bending machine can dredge the expansion to the root canal.

The research of the inventor finds that the operation efficiency is low because the bending mobile phone needs to be repeatedly lifted and pulled during the root canal enlargement treatment; and the oral cavity of the patient is small, and particularly when the back teeth are made, the lifting space is small, and the operation is inconvenient.

The application provides a dental handpiece's aircraft nose still is provided with reciprocal actuating mechanism in current core intracavity, and reciprocal actuating mechanism drive core need not repeatedly carry and draw the curette along core axial reciprocating motion when the root canal enlarges the treatment to in the root canal enlarge the operation and improve root canal and enlarge operating efficiency.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships that the products of the present invention are conventionally placed in use, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal", "vertical" and the like do not imply that the components are required to be absolutely horizontal or pendant, but rather may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

First embodiment

This embodiment provides a root canal preparation machine, this root canal preparation machine includes dental handpiece, operating handle and main control system, and the main control system is connected with operating handle, and operating handle embeds there is the motor, connects the back when dental handpiece and operating handle, makes the motor start through the start button on the operating handle to dental handpiece just can normally work, in order to realize the treatment purpose.

Referring to fig. 1 and 2, the dental handpiece is generally an elbow, and includes a handpiece, a first shaft section 105 and a second shaft section 106 connected in series, wherein the included angle between the length direction of the first shaft section 105 and the length direction of the second shaft section 106 is an obtuse angle, so as to facilitate the root canal enlargement treatment. The handpiece is arranged at one end of the first pole section 105 far away from the second pole section 106, and one end of the second pole section 106 far away from the first pole section 105 is connected with the operating handle.

A transmission shaft 104 is arranged in the first rod section 105, the transmission shaft 104 can be rotatably arranged in the first rod section 105 along the axis of the transmission shaft, and a connecting shaft 107 capable of rotating along the axis of the transmission shaft is arranged in the second rod section 106; a first end of the connecting shaft 107 is in driving connection with the motor in the operating handle, and a second end of the connecting shaft 107 is in driving connection with a first end of the driving shaft 104.

The handpiece of the dental handpiece of the embodiment comprises a handpiece shell 10, wherein a handpiece cavity 101 is arranged in the handpiece shell 10, and a rotatable handpiece 102 and a driving gear 103 are arranged in the handpiece cavity 101; the driving gear 103 is sleeved at one end of the movement 102, and the movement 102 can move along the axial direction of the driving gear 103; a reciprocating driving mechanism is further arranged in the movement cavity 101 and used for driving the movement 102 to reciprocate along the axial direction of the movement 102.

Therefore, the movement 102 is arranged in the movement cavity 101 of the handpiece shell 10, one end of the movement 102 is provided with the driving gear 103, and the driving gear 103 is used for being in transmission connection with the transmission shaft 104, such as meshing transmission, so that the rotary driving torque of the motor is transmitted to the driving gear through the transmission shaft 104, and the movement 102 is driven to rotate; the movement 102 can move axially along the driving gear 103, and meanwhile, a reciprocating driving mechanism is also arranged in the movement cavity 101 and drives the movement 102 to move axially in a reciprocating manner along the self-axial direction, so that the movement 102 does axial reciprocating movement while rotating. When core 102 clamping root canal file 20, can drive root canal file 20 through core 102 rotatory and drive root canal file 20 along self axial reciprocating motion. Therefore, when using the dental handpiece of this embodiment to carry out root canal therapy, through reciprocal actuating mechanism drive root canal file 20 along self axial reciprocating motion, no longer need manually carry and draw to improve the treatment effeciency of root canal enlargement, reduced the requirement to patient's cavity space, the operation of the root canal enlargement treatment of also being convenient for has improved the experience sense of patient's treatment.

In the embodiment, the movement 102 is rotatably arranged in the movement cavity 101, and a cavity for clamping the head of the root canal file 20 is arranged in the movement 102; one end of the movement 102 extends out of the movement cavity 101 so as to insert the head of the file 20 into the movement 102.

With reference to fig. 2, for the connection between the driving gear 103 and the movement 102, a mode of coaxially arranging a spline in the middle of the driving gear 103 and arranging a spline groove on the outer wall of the movement 102, or a mode of coaxially arranging a flat hole in the middle of the driving wheel and arranging a flat wire on the outer wall of the movement 102, or a mode of arranging a through hole in the middle of the driving gear 103 and arranging a limiting protrusion on the side wall of the through hole, and arranging a sliding groove matched with the limiting protrusion on the outer wall of the movement 102, etc. may be adopted; it is only necessary that the movement 102 can synchronously rotate along with the driving gear 103 and the movement 102 can slide relative to the driving gear 103 along the length direction of the movement 102. The drive gear 103 is typically a bevel gear, but may be a gear with teeth arranged vertically along the circumference.

For the reciprocating driving mechanism in the movement cavity 101, it is only necessary to drive the movement 102 to reciprocate along the length direction of the movement 102 without affecting the rotation of the movement 102, such as an electromagnet mechanism, a voice coil motor mechanism, a cam mechanism, etc. which are driven in a contactless manner. Specifically, in conjunction with fig. 2, the double drive mechanism in this embodiment is a cam mechanism including a drive block 108, a drive protrusion 109, and an elastic member 110.

Wherein, drive block 108 is located at one end of movement cavity 101 far away from drive gear 103, and the end surface of drive block 108 close to drive gear 103 has an annular drive surface coaxial with movement 102. The driving block 108 may be a ring-shaped member, such as a bearing, surrounding the end of the movement 102, or a plate-shaped member provided with a ring-shaped rib. The distance from the driving surface to the driving gear 103 fluctuates along the circumferential direction of the driving surface, that is, the distance from the driving surface to the driving gear 103 alternately increases and decreases along the circumferential direction of the driving block 108, and the driving surface may be an inclined slope directly. The driving surface may be an end surface of the driving block 108 close to the driving gear 103, or may be a part of the end surface of the driving block 108 close to the driving gear 103.

The drive boss 109 is provided on the movement 102 and is directed to hibernation removal. The driving protrusion 109 may be integrally formed with the movement 102, or may be provided separately from the movement 102; for ease of manufacture, in this embodiment, drive boss 109 is a pin inserted at the end of cartridge 102. The length of the pin may also be at an angle to the length of the movement 102, or parallel or perpendicular to the length of the movement 102.

The elastic member 110 may be a coil spring, or a tubular elastic element such as a bellows, and the elastic member 110 is sleeved outside the movement 102 and abuts against between the driving gear 103 and the movement 102. A first limiting part for limiting the elastic piece 110 to move towards the movable driving gear 103 is arranged at one end, opposite to the elastic piece 110, of the driving gear 103; the first limiting part may be a stepped surface provided at an end of the driving gear 103, or may be a stepped hole recessed inward from an end of the driving gear 103.

Meanwhile, a second limiting part for limiting the elastic part 110 to move towards the driving block 108 is further arranged on the outer side wall of the movement 102, and the second limiting part can be a bulge arranged outside the movement 102 or a shoulder arranged around the movement 102; or the movement 102 is made into a step shaft shape, and the limiting part is a step surface of the movement 102. Thus, the elastic member 110 can abut the end of the driving protrusion 109 on the outer wall of the movement 102 against the driving surface.

In addition, a pre-tightening spring 111 is arranged in one end of the movement cavity 101, which is far away from the driving gear 103, one end of the pre-tightening spring 111 abuts against the side wall of the movement cavity 101, which faces the driving block 108, and the other end of the pre-tightening spring 111 abuts against the driving block 108, so as to press the reciprocating driving mechanism to the driving gear 103, and enable the driving block 108 to abut against the driving protrusion 109.

In summary, when the dental preparation machine of the present embodiment is used, the dental handpiece is connected to the operating handle, so that the connecting shaft 107 in the dental handpiece is in transmission connection with the motor in the operating handle, the end of the root canal file 20 is inserted into the movement 102, and the root canal file 20 is held by the movement 102. The start button on the operating handle is activated to operate the motor, so that the rotation torque of the motor is transmitted to the movement 102 through the connecting shaft 107, the transmission shaft 104 and the driving gear 103 again to rotate the movement 102 around the axis of the driving gear 103, and the root canal file 20 is driven to rotate through the movement 102.

In the process of rotation of the movement 102, the elastic member 110 tightly presses the driving protrusion 109 at the end of the movement 102 against the driving surface of the driving block 108, and as the driving surface undulates along the circumferential direction of the driving surface, the driving protrusion 109 also undulates along the circumferential direction of the driving surface under the pressing of the elastic member 110, so that the movement 102 is driven by the elastic member 110 and the driving block 108 to reciprocate along the axial direction of the driving gear 103.

Therefore, when using the root canal preparation machine of this embodiment to carry out root canal enlargement, root canal file 20 need not manual pull-up cell-phone along 20 length direction reciprocating motion of root canal file in rotary motion to improve the treatment effeciency of root canal enlargement, reduced the requirement to patient's cavity space, the operation of the root canal enlargement treatment of also being convenient for has improved the experience sense of patient's treatment.

Second embodiment

Referring to fig. 3, the present embodiment provides a dental preparation machine, which has the same basic structure, operation principle and technical effects as the root canal preparation machine of the first embodiment, and for the sake of brief description, no mention is made in this embodiment, and reference may be made to the corresponding contents in the first embodiment, but the present embodiment is different from the first embodiment in that: the reciprocating drive mechanism is different in structure.

In this embodiment, the reciprocating driver is a cam mechanism that includes a drive block 108 and a drive lobe 109.

Specifically, referring to fig. 4 and 5, the two driving blocks 108 are disposed opposite to each other, and both are sleeved on the movement 102, and an annular driving groove 1081 is formed between the two driving blocks 108, wherein along the circumferential direction of the driving blocks 108, that is, along the length direction of the driving groove 1081, the driving groove 1081 faces two side walls of the driving gear 103 and undulates along the circumferential direction of the driving blocks 108, that is, the distance between the driving groove 1081 and the driving gear 103 gradually changes.

In this embodiment, the driving protrusion 109 is disposed on the movement 102, at least partially protrudes into the driving groove 1081, and is movable relative to the driving groove 1081. One end of the driving protrusion 109 is inserted into the sidewall of the movement 102, and the other end of the driving protrusion 109 is inserted into the driving groove 1081. One end of the driving protrusion 109, which is positioned in the driving groove 1081, is sleeved with a roller, and the roller is positioned in the driving groove 1081; the end of the driving protrusion 109 located at the driving groove 1081 may be spherical or cylindrical. The two opposite side surfaces of the driving groove 1081 in the width direction are both inclined surfaces, that is, the two opposite end surfaces of the driving block 108 are both inclined surfaces and have matching shapes.

When the root canal preparation machine of this embodiment is used, the motor in the operating handle transmits the rotational torque to the movement 102 through the connecting shaft 107, the transmission shaft 104 and the driving gear 103, so that the movement 102 rotates around the axis of the driving gear 103, and the root canal file 20 is driven to rotate by the movement 102. In the process of rotating the movement 102, the movement 102 drives the driving boss 109 to rotate relative to the driving block 108; since both side walls of the driving groove 1081 undulate along the circumferential direction of the driving block 108, and one end of the driving protrusion 109 is located in the driving groove 1081, when the driving protrusion 109 rotates relative to the driving block 108, the side walls of the driving groove 1081 force the driving protrusion 109 to undulate along the length direction of the movement 102, so that the movement 102 is driven to reciprocate along the axial direction of the driving gear 103 through the driving groove 1081 and the driving protrusion 109.

In this case, the driving protrusion 109 is provided with a roller structure, so that when the movement 102 rotates relative to the driving block 108, the friction force when the driving protrusion 109 moves fast relative to the driving can be reduced by the rolling of the roller. Compared with the first embodiment, the present embodiment does not need to use the elastic member 110, and has a simpler structure and higher reliability.

Third embodiment

Referring to fig. 6, the present embodiment provides a dental preparation machine, the basic structure, operation principle and technical effects of the root canal preparation machine are substantially the same as those of the second embodiment, and for the sake of brief description, no mention is made to the parts of the present embodiment, and the differences between the present embodiment and the second embodiment are as follows: the reciprocating drive mechanism is different in structure.

In the present embodiment, the reciprocating drive mechanism is a cam mechanism including a movement sleeve 112 and a drive projection 109, and a drive groove 1081 is formed on the inner wall of the movement sleeve 112;

referring to fig. 7 to 9, the movement sleeve 112 is tubular and is sleeved outside the movement 102 and the gear of the movement 102, wherein a through hole 1121 is formed in a side wall of the movement sleeve 112, and the through hole 1121 is used for the transmission shaft 104 to pass through, so that the transmission shaft 104 can be in transmission connection with the driving gear 103 to drive the movement 102 to rotate. An axially surrounding driving groove 1081 is formed in an inner wall of the movement sleeve 112, and a distance between the driving groove 1081 and the driving gear 103 gradually changes along a circumferential direction of the movement sleeve 112, that is, along a length direction of the driving groove 1081.

In this embodiment, the driving protrusion 109 is disposed on the movement 102, at least partially protrudes into the driving groove 1081, and is movable relative to the driving groove 1081. One end of the driving protrusion 109 is inserted into the sidewall of the movement 102, and the other end of the driving protrusion 109 is inserted into the driving groove 1081. One end of the driving protrusion 109, which is positioned in the driving groove 1081, is sleeved with a roller, and the roller is positioned in the driving groove 1081; the end of the driving protrusion 109 located at the driving groove 1081 may be spherical or cylindrical. The driving groove 1081 is adapted to the shape of the two opposite side surfaces of the driving protrusion 109, and is a slope.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A handpiece of a dental handpiece is characterized by comprising a handpiece shell, wherein a handpiece cavity is arranged in the handpiece shell, and a rotatable handpiece and a driving gear are arranged in the handpiece cavity;

the driving gear is sleeved at one end of the machine core, and the machine core can move along the axial direction of the driving gear;

2. The handpiece of claim 1, wherein the reciprocating drive mechanism is a cam mechanism comprising a drive block, a drive protrusion and a resilient member;

3. The handpiece of claim 2, wherein the resilient member is disposed outside the cartridge and abuts between the drive gear and the cartridge.

4. The handpiece of claim 2, wherein the drive surface is a ramp.

5. The handpiece of claim 1, wherein the reciprocating drive mechanism is a cam mechanism comprising a drive block and a drive projection;

6. The handpiece of claim 1, wherein the reciprocating drive mechanism is a cam mechanism comprising a cartridge sleeve and a drive boss;

7. The handpiece of claim 5 or 6, wherein a roller is sleeved on an end of the driving protrusion in the driving groove; and/or

8. A handpiece according to claim 1, wherein a pre-tensioning spring is provided in the end of the handpiece chamber remote from the drive gear, the pre-tensioning spring being adapted to bias the reciprocating drive mechanism towards the drive gear.

9. Dental handpiece comprising a handpiece according to any one of claims 1 to 8.

10. A root canal preparation machine comprising the dental handpiece of claim 9.