GB1580356A

GB1580356A - Dental pin

Info

Publication number: GB1580356A
Application number: GB38296/77A
Authority: GB
Original assignee: FILHOL S
Current assignee: FILHOL S
Priority date: 1977-09-14
Filing date: 1977-12-13
Publication date: 1980-12-03

Description

(54) DENTAL PIN (71) I, STUART JULIAN FILHOL, a British Subject, of Castlefreke, County Cork, Irish Republic, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to screw pins for use in dentistry particularly, but not exclusively, for location in teeth to provide a means whereby fillings can be firmly attached to the teeth.

It has already been proposed to provide small, screw-threaded pins which are screwed into pre-formed bores formed in a tooth so that fillings may be more firmly attached to the tooth when repairing cavities or the like. The pins are generally in the form of self-tapping screws having an external diameter of the order of 0 7 mm and various means are used in order to screw such pins into the tooth. Such means may be in the the form of a tool having a slot at one end which engages a correspond- ingly shaped end of the pin. Alternatively the pin may be formed integrally with a tool which is detached from the pin after insertion in the tooth. However the present invention is not limited to use with any particular fixing means although the latter means is preferred.

An object of the invention is to provide an improved screw form for dental pins, the screw form being arranged to provide a better performance than known pins, particularly when applied to relatively small pins.

According to the invention a dental screw pin comprises a body which is cylindrical over at least part of its length and over which is formed a self-tapping screw thread of which the thread form is such that the ratio of outside diameter to core diameter is in the range 1-15 to 14 and the included angle at the point of the thread is in the range 40 to 50". Preferably the thread pitch is in the range 015 to 0 20 mm for a pin having an outside thread diameter of 060 mm.

Conveniently the thread has a BA thread form and the radius at the point of the thread is between zero and 002 mm.

The preferred dimensions of the thread form are 060 mm outside diameter, 049 mm core diameter, included angle of thread 47.50, radius at the point of the thread 0 01 mm and pitch of thread 019 mm. Such a pin will be screwed into a cylindrical bore having a preferred diameter of 0 53 mm.

Preferably the leading end of the pin is cone shaped and the cone angle is 90 , The screw thread over the leading end of the pin may have an outer diameter which increases in the direction away from said leading end until a maximum and, thereafter, constant outer diameter is reached.

The portion of the thread with increasing outer diameter may be formed over a body of cylindrical form so that the depth of thread increases from said leading end, or said portion is formed over a portion of the body having increasing diameter so that the depth of thread remains substantially constant along the pin.

Further features of the invention will become apparent from the following description of two embodiments of the invention given by way of example only and with reference to the drawings in which: Fig. 1 is a side elevation of a dental pin and associated means for screwing the pin into a tooth, Fig. 2 is a sectional view of part of the pin to a larger scale, and Fig. 3 is a sectional view, corresponding to Fig. 2, of another form of pin.

Referring to Fig. 1 a screw-threaded pin 10 is formed integral with an adaptor 11 which fits into a dental drill to be driven thereby. The pin and adaptor are connected by an integral joining piece 12 which is arranged to part from the pin 10 when the torque on the drill reaches a predetermined level, all in known manner.

The pin 10 is arranged to be inserted into a preformed bore in the tooth by a selftapping screw action, the bore having a size intermediate that of the core diameter of the screw threaded portion, and the outer diameter of the thread.

Fig. 2 shows the screw pin to a larger scale to enable the dimensions of the thread form of the screw to be explained but it will be appreciated that the illustrated pin is not to scale.

The pin has a cylindrical core 15 which has a diameter D and around the core and integral therewith is a thread 16 the tips 17 of which are at a diameter d. The thread subtends an angle a at the tip and the line 18 denotes the walls of a bore in which the pin is located, the bore having a diameter b. The thread has a pitch p.

The thread form of the pin is arranged so that the ratio of outside diameter to core diameter, i.e. the ration d: D is relatively low and in the range 1 15 to 14. For example with the outside diameter d at 060 mm the core diameter may be between 0 43 and 052 mm, preferably 049 mm.With the dimensions given the thread pitch p is between 015 and 020 mm preferably 019 mm, and the included angle a is between 40 and 50 , preferably 47 5 . As indicated by the included angle, it is important that the tip of the thread is relatively sharply pointed as on BA form threads, and in this connection the radius of each of the tips 17 may be between zero and 0 02 mm preferably 0 01 mm. With such a pin the bore diameter b is preferably 053 mm to provide only a small air gap or void between the core 15 and the wall 18 of the bore.

Essentially the thread form aims to pro vide a relatively sharply pointed thread 16 with a minimum difference between the core diameter D and the thread diameter d and a relatively long pitch of thread compared to the core diameter. This is achieved while the pin still has sufficient retaining characteristics when screwed into a tooth.

In particular the pin, even though of small size, has sufficient strength for its purpose due to its relatively large core diameter.

The free end of the pin which is the end which first enters a preformed bore 18 in a tooth during use of the pin, is formed as a cone 20 instead of the pin having a flat end. The sides of the cone make an angle of about 45" with a notional line at a right angle to the longitudinal axis of the pin which which means that the nominal cone angle is 90". However it will be appreciated that these angles can be varied provided that the angle is not such that the length of the cone is too long or too short. In the former case the cone would occupy too great a proportion of the length of the pin and reduce the effective length of the bore and in the latter case it would not adequately serve to assist in entering the pin in the bore.

In practice the cone 20 may have a slightly rounded profile at its end.

The outer diameter of the thread 16 is progressively decreased at the leading end in the Fig. 2 embodiment by retaining a constant core diameter D and reducing the thread depth over the portion 16a so that the thread depth is nil when the thread reaches the cone portion 20 of the pin.

The thread 16a retains its sharp profile over its tapered end portion and the tapered portion extends over one to three turns of the thread.

Referring to Fig. 3, a pin having a different form at its leading end is shown, the pin otherwise being the same as in the Fig.

1 and 2 embodiment. The leading end is cone-shaped over the portion 20, the sides of the cone making an angle of about 45" with a notional line at a right angle to the axis of the pin, and the screw thread 16 over most of the length of the pin is of the form described in relation to Fig. 2 but over that portion 16a of the thread nearest the free or leading end of the pin the core diameter D of the pin is tapered so that the outer diameter of the thread 16a is correspondingly tapered, that is, the outer diameter of the thread progressively decreases towards the leading end of the pin. The tapering extends from a core diameter x at the leading end over one to three turns of the thread about the pin until the core diameter reaches the full outer diameter D and the thread reaches its maximum diameter d; the pin thereafter having a constant core diameter D.Over the tapered portion the thread remains of constant depth and it retains its sharp profile, as seen in the drawing, so that the self-tapping characteristic of the pin is retained and improved over that of prior dental pins, particularly at its leading end.

Due to the tapering of the threads 16a of Figs. 2 and 3 a minimum of axial end pressure on the pin is required after entry of the pin in the bore for the pin to be screwed into the bore. Prior tapered threads have thread forms which are flattened in producing the taper thereby reducing their self-tapping characteristics.

The pin may have a multiple or single start thread form.

The use of a pointed thread with a low included angle means that less pressure is exerted on the dentine of the tooth in which the pin is inserted, for the same depth of penetration. Furthermore the invention makes possible the use of a smaller pin having similar strength to a larger pin used hitherto which eases the problem of locating the pin in the tooth. Moreover more pins can be fixed to a tooth than might be possible with larger pins.

WHAT I CLAIM IS: - 1. A dental screw pin comprising a body which is cylindrical over at least part of its length and over which is formed a self

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. scale to enable the dimensions of the thread form of the screw to be explained but it will be appreciated that the illustrated pin is not to scale. The pin has a cylindrical core 15 which has a diameter D and around the core and integral therewith is a thread 16 the tips 17 of which are at a diameter d. The thread subtends an angle a at the tip and the line 18 denotes the walls of a bore in which the pin is located, the bore having a diameter b. The thread has a pitch p. The thread form of the pin is arranged so that the ratio of outside diameter to core diameter, i.e. the ration d: D is relatively low and in the range 1 15 to 14. For example with the outside diameter d at 060 mm the core diameter may be between 0 43 and 052 mm, preferably 049 mm.With the dimensions given the thread pitch p is between 015 and 020 mm preferably 019 mm, and the included angle a is between 40 and 50 , preferably 47 5 . As indicated by the included angle, it is important that the tip of the thread is relatively sharply pointed as on BA form threads, and in this connection the radius of each of the tips 17 may be between zero and 0 02 mm preferably 0 01 mm. With such a pin the bore diameter b is preferably 053 mm to provide only a small air gap or void between the core 15 and the wall 18 of the bore. Essentially the thread form aims to pro vide a relatively sharply pointed thread 16 with a minimum difference between the core diameter D and the thread diameter d and a relatively long pitch of thread compared to the core diameter. This is achieved while the pin still has sufficient retaining characteristics when screwed into a tooth. In particular the pin, even though of small size, has sufficient strength for its purpose due to its relatively large core diameter. The free end of the pin which is the end which first enters a preformed bore 18 in a tooth during use of the pin, is formed as a cone 20 instead of the pin having a flat end. The sides of the cone make an angle of about 45" with a notional line at a right angle to the longitudinal axis of the pin which which means that the nominal cone angle is 90". However it will be appreciated that these angles can be varied provided that the angle is not such that the length of the cone is too long or too short. In the former case the cone would occupy too great a proportion of the length of the pin and reduce the effective length of the bore and in the latter case it would not adequately serve to assist in entering the pin in the bore. In practice the cone 20 may have a slightly rounded profile at its end. The outer diameter of the thread 16 is progressively decreased at the leading end in the Fig. 2 embodiment by retaining a constant core diameter D and reducing the thread depth over the portion 16a so that the thread depth is nil when the thread reaches the cone portion 20 of the pin. The thread 16a retains its sharp profile over its tapered end portion and the tapered portion extends over one to three turns of the thread. Referring to Fig. 3, a pin having a different form at its leading end is shown, the pin otherwise being the same as in the Fig.

The pin may have a multiple or single start thread form.

tapping screw thread of which the thread form is such that the ratio of outside diameter to core diameter is in the range of 1-15 to 1-4 and the included angle at the point of the thread is in the range 40 to 50".

2. A dental pin according to claim 1 wherein the thread pitch is in the range 0 15 to 0 20 mm for a pin having an outside diameter of 0 60 mm.

3. A dental pin according to claim 1 or 2 wherein the thread is of BA thread form and the radius at the point of the thread is between zero and 0 02 mm.

4. A dental pin according to any one of the preceding claims wherein the leading end of the pin is cone shaped.

5. A dental pin according to claim 4 wherein the cone angle is 90".

6. A dental pin according to any one of the preceding claims wherein the screw thread over the leading end of the pin has an outer diameter which increases in the direction away from said leading end until a maximum and, thereafter, constant outer diameter is reached.

7. A dental pin according to claim 6 wherein the portion of the thread with increasing outer diameter is formed over a body of cylindrical form so that the depth of thread increases from said leading end.

8. A dental pin according to claim 6 wherein the portion of the thread with increasing outer diameter is formed over a portion of the body having increasing diameter so that the depth of thread remains substantially constant along the pin.

9. A dental screw pin substantially as described with reference to Fig. 1 and 2.

10. A dental screw pin substantially as described with reference to Fig. 3.