GB2140308A - Dental apparatus - Google Patents

Abstract

An intra oral dental parallelometer comprising a mechanical linkage having at one end portion a clamp (34) by means of which a dental handpiece (35), in which a tooth cutting tool is supported, can be clamped to one end portion of the linkage, and having at the other end portion remote from the clamp (34) an anchorage means (26) adapted to be held in use between the upper and lower jaws of a patient, the linkage comprising mutually pivoted parts (36, 38: 52, 54) which permit clamp movement with respect to the anchorage means (26) in two planes. <IMAGE>

Description

SPECIFICATION Dental apparatus This invention relates to dental apparatus and more especially it relates to intra oral dental parallelometers.

For dental crown and bridge work, it is necessary to effect precision cutting of tooth material in order accurately to define anchoring points for crown or bridge inserts. In order to provide for precision control of a dental handpiece in which a cutting tool is mounted, it is known to provide an intra oral parallelometer, one end of which is arranged to be anchored palatally on a specially made acrylic base plate and the other end of which comprises means for attaching a dental handpiece.

The anchoring arrangement for this known kind of parallelometer has a number of disadvantages including the disadvantage that it is time consuming to make and essentially requires a patient to attend for at least one parallelometer fitting visit before dental work on a crown or bridge can begin.

It is an object of the present invention to provide an intra oral dental parallelometer in which the disadvantage just before outlined is substantially obviated.

According to the present invention an intra oral dental parallelometer comprises a mechanical linkage having at one end portion a clamp by means of which a dental handpiece, in which a tooth cutting tool is supported, can be clamped to one end portion of the linkage, and having at the other end portion remote from the clamp an anchorage means adapted to be held in use between the upper and lower jaws of a patient, the linkage comprising mutually pivoted parts which permit clamp movement with respect to the anchorage means in two planes.

The anchorage means may comprise a generally wedge-shaped structure adapted to be held firmly between the upper and lower jaws, the linkage being secured to the wider end of the wedge-shaped structure thereby to project away from the jaws.

The linkage may be adjustably secured to the wider end of the wedge by means of a screw and lock nut.

The wedge-shaped structure may comprise two troughs arranged on opposing sides of the structure which taper away from each other and which are adapted to receive a setable medium, so that impressions of opposing upper and lower teeth are made in respective troughs when the structure is held between the upper and lower jaws.

The pivoted parts of the linkage may comprise first pivoted links which permit clamp movement in one of the two planes and second pivoted links which permit clamp movement in the other of the two planes.

The first pivoted links may comprise two links pivotally coupled in series by means of pivot pins so as to be relatively moveable in the said one plane only.

The second pivoted links may comprise two links pivotally coupled in parallel so as to define a parallelogram linkage which affords movement in the other of the two planes only.

The two links may be coupled to the screw and lock nut by means of a lockable elbow joint which permits movement of the two links in the said other of the two planes, whereby the said two links can be moved to a preset position, the elbow joint including a locking screw for locking the joint in a selected preset position.

The clamp may be coupled to the parallelogram linkage by means of a pivoted joint which permits movement in the said one plane only, the parallelogram linkage being coupled to the clamp through the two links which are coupled in turn to the screw and lock nut.

The said two planes may be mutally orthogonal.

Embodiments of the invention will now be described solely by way of example with reference to the accompanying drawings in which: Figures 1, 2 and 3 are somewhat schematic sectional perspective views showing upper teeth prepared for crowns; Figure 4 is a somewhat schematic front view illustrating the manner in which a tooth is prepared to receive a crown; Figure 5 is a side view of a dental parallelometer clamped between upper and lower jaws; Figure 6 is a front perspective view of the dental parallelometer shown in Fig. 5; Figure 7 is a plan view of the dental parallelometer shown in Figs. 5 and 6; Figures 8 and 9 are front and side views respectively of the dental parallelometer shown in Fig. 7; and Figures 10 and 11 are side and plan views of alternative anchorage means.

Referring now to Fig. 1, in order to prepare an upper tooth 2 to receive a crown 3, the upper tooth 2 is carefully ground as shown in Fig. 1 so as to have a slight taper away from the gum 4. The crown 3 to be fitted to the prepared tooth 2 is formed so as to have a complementary recess 6 into which the tooth 2 is fitted and secured with dental adhesive.

The taper formed on the prepared tooth 2 shown in Fig. 1 is ideal and will facilitate a good bond between the tooth 2 and the crown 3. If however, as shown in Fig. 2, a tooth 8 is tapered towards a gum 10 during preparation it clearly will not fit into a recess 1 2 in a crown 14. Conversely if as shown in Fig. 3, a tooth 1 6 is tapered away from a gum 1 8 but too sharply, then the prepared tooth 1 6 will not satisfactorily adhere to a complementary recess 20 formed in a crown 21, since known dental adhesives will not provide sufficient adhesion between sharply tapered surfaces.

As shown in Fig. 4, preparation of a tooth 24 is effected with a slightly tapered dental cutting too or burr 22 which is supported in the chuck 23 of a dental handpiece. It is necessary carefully to control the cutting operations required to form the tooth 24 as shown in Fig. 4 so to define the required angle of taper. In order to facilitate dental cutting operations, it is known to use a dental parallelometer which is anchored palatally at one end portion and which at the other end portion is adapted to support a dental cutting tool in such a way as to permit movements of the cutting tool only in predetermined planes.

As hereinbefore mentioned however, such known palatally anchored parallelometers have the disadvantage that they are time consuming to make and require at least one parallelometer fitting visit before dental work on a crown or bridge can begin. Moreover with known parallelometer devices working is limited to the upper jaw only.

In order to overcome the aforementioned disadvantages, an improved dental parallelometer has been designed which will now be described in detail with reference to Figs. 5 to 9.

Referring now to Figs. 5 to 9, wherein corresponding parts of the various Figures bear the same numerical designations, a dental parallelometer comprises an anchor structure 26 which is clamped between the teeth of an upper jaw 28 and a lower jaw 30. The anchor structure 26 is arranged to support a mechanical linkage 32 to one end of which a clamp 34 is secured which serves to support a dental handpiece 35 in which a cutting tool or burr is mounted. The mechanical linkage 32 comprises pivoted parts which permit movement of the clamp 34 with respect to the anchor structure 26 in two planes only.

The pivoted parts of the mechanical linkage comprise two links 36 and 38 which are serially coupled by means of a pivot pin 40 so as to be relatively moveable in one plane only.

The link 38 is coupled by means of a pivot pin 42 to a lockable elbow joint 44, the angle of which can be selected and then locked by means of a locking screw 46. The elbow joint 44 extends to define a screw 48 which is screwed into the anchor structure 26 and locked in position by means of a lock nut 50.

In order to provide pivotable movement in a plane orthogonal to the plane in which the links 36 and 38 permit movement of the handpiece 35, two pivoted links 52 are provided which are secured at one end to a link 54 which is pivoted to the link 36 by means of a pivot pin 56 and which at the other end are pivoted on a link 58 which in turn is pivoted on the clamp 34 by means of a pin 60. The links 52 are connected in parallel and operate after the manner of a parallelogram to afford movement in the plane orthorgonal to the plane in which movement is permitted by the links 36 and 38.

The anchor structure 26 is arranged to be generally wedge-shaped so that it can easily be clamped between the teeth of the upper jaw 28 and the lower jaw 30 and in order to facilitate accurate re-positioning of the anchor structure 26 in a patient's mouth, the anchor structure is provided with a pair of opposed troughts 62 and 64 which in use are packed with a settable dental impression material, which a patient is required to bite into so as to define therein teeth impressions of the opposing molars of the upper and lower jaws.

Having set, the dental impression material which is keyed into the troughs by means of grooves 66 formed in the troughs, affords defined locations which enable the parallelometer to be firmly held between a patient's teeth without risk of movement.

As can be seen most clearly in Fig. 6, the handpiece will in use be required to support a tapered generally alongate burr 68 which is permitted to move parallel with the longitudinal axis 70 of a tooth 72 which is being cut and also in a generally orthogonal occlusal plane 74 as shown in Fig. 5. Movement along the axis 70 of the tooth is permitted by the parallelogram linkage comprising the links 52 and movement of the burr 68 in the occlusal plane 74 is permitted by the links 36 and 38.

Preset adjustment by means of the screw 46 permits tilt of the parallelometer in a saggital plane through an angle as defined by arrows 76 in Fig. 9. Preset coronal tilt may be affected by adjustment of the screw 48 which is lockable by means of the nut 50. The angle of coronal tilt is indicated in Fig. 8 by means of an arrow 78.

Referring now to Figs. 10 and 11, there is shown a modified anchor structure 26. In Figs. 10 and 11, similar parts as in the previous figures have been given the same reference numbers. The anchor structure 26 of Figs. 10 and 11 comprises a central metal block 80 which is advantageously made of chromium plated mild steel. Secured to the top and bottom of the block 80 are a pair of trough members 82. The trough members 82 are preferably made of a plastics material such for example as nylon. As shown in Fig. 11 the trough members 82 have side walls 84 and a base wall 86. The base wall 86 is provided with an elongate slot 88 for receiving a screw 90. Each slot 88 permits relative lateral movement between its trough member 82 and the block 80. Thus each trough member 82 can be slid to any desired lateral position to accommodate for example, for small patients' mouths. The slot 88 is counter sunk as shown by the shading lines 92 to accommodate the head of the screw 90 as shown most clearly in Fig. 10. Before the screw 90 is fully tightened, relative twisting movement can also occur between each trough member 82 and the block 90.

By utilising parallelometers as herein before described, accurate dental preparation work, including inlay work, is facilitated as may be required for crowns or bridges. Since the dental handpiece may quite easily be rotated in the clamp 34, which is lockable by means of a clamp screw 94, the parallelometers may be used equally successfully to work on teeth in the upper jaw or in the lower jaw.

The materials from which the parallelometers are constructed should be non-corrosive and non-allergenic, and suitable materials are stainless steel and/or some rigid plastics materials.

It is to be appreciated that the embodiments of the invention described above with reference to the drawings, have been given buy way of example only, and that modifications may be effected. Thus, for example, an anchorage means other than the illustrated anchor structures 26 may be employed. The clamp 34 may have two V-shaped portions instead of the two simi-circular portions shown in Fig. 9. Roller bearings, ball bearings or pins may be employed to enable pivotting os some of the joints of the parallelometer. If desired, the link 36 may be entirely omitted.

The various parts of the parallelometer can be held together with screws and/or rivets as desired.

Claims (11)

1. An intra oral dental parallelometer comprising a mechanical linkage having at one end portion a clamp by means of which a dental handpiece, in which a tooth cutting tool is supported, can be clamped to one end portion of the linkage, and having at the other end portion remote from the clamp an anchorage means adapted to be held in use between the upper and lower jaws of a patient, the linkage comprising mutually pivoted parts which permit clamp movement with respect to the anchorage means in two planes.

2. An intra oral dental parallelometer according to Claim 1 in which the anchorage means comprises a generally wedge-shaped structure adapted to be held firmly between the upper and lower jaws, the linkage being secured to the wider end of the wedge-shaped structure thereby to project away from the jaws.

3. An intral oral dental parallelometer according to Claim 2 in which the linkage is adjustably secured to the wider end of the wedge by means of a screw and lock nut.

4. An intra oral dental parallelometer according to Claim 2 or Claim 3 in which the wedge-shaped structure comprises two troughs arranged on opposing sides of the structure which taper away from each other and which are adapted to receive a setable medium, so that impressions of opposing upper and lower teeth are made in respective troughs when the structure is held between the upper and lower jaws.

5. An intra oral dental parallelometer according to any of the preceding claims in which the pivoted parts of the linkage comprise first pivoted links which permit clamp movement in one of the two planes and second pivoted links which permit clamp movement in the other of the two planes.

6. An intra oral dental parallelometer according to Claim 5 in which the first pivoted links comprise two links pivotally coupled in series by means of pivot pins so as to be relatively moveable in the said one plane only.

7. An intra oral dental parallelometer according to Claim 5 or Claim 6 in which the second pivoted links comprise two links pivotally coupled in parallel so as to define a parallelogram linkage which affords movement in the other of the two planes only.

8. An intra oral dental parallelometer according to Claims 2 and 7 in which the two links are coupled to the screw and lock nut by means of a lockable elbow joint which permits movement of the two links in the said other of the two planes, whereby the said two links can be moved to a preset position, the elbow joint including a locking screw for locking the joint in a selected preset position.

9. An intra oral dental parallelometer according to Claims 2 and 7 in which the clamp is coupled to the parallelogram linkage by means of a pivoted joint which permits movement in the said one plane only, the parallelogram linkage being coupled to the clamp through the two links which are coupled in turn to the screw and lock nut.

10. An intra oral dental parallelometer according to any one of the preceding claims in which the linkage permits clamp movement with respect to the anchorage means in two mutually orthogonal planes.

11. An intra oral dental parallelometer substantially as herein described with reference to Figs. 5 to 9 and 10 to 11 of the accompanying drawings.