Dowel orienting apparatus useful in dentistry

Jan. 5, 1971 e. η. zahn 3,552,018

DOWEL ORIENTING APPARATUS USEFUL IN DENTISTRY

Filed April 10, 1969 2 Sheets-Sheet 1

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Jan. 5, 1971

E. H. ZAHN 3,552,018

DOWEL ORIENTING APPARATUS USEFUL IN DENTISTRY

Filed April 10, 1969

Sheets-Sheet 3

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United States Patent Office

3,552,018

Patented Jan. 5, 1971

3,552,018

DOWEL ORIENTING APPARATUS USEFUL IN DENTISTRY

Eric H. Zahn, 6401 Lake Washington Blvd., Kirkland, Wash. 98037 5

Filed Apr. 10, 1969, Ser. No. 815,108

Int. Cl. A61c 13/00

U.S. Cl. 32—11 1 Claim

ABSTRACT OF THE DISCLOSURE

To a base member adapted to receive and support an upwardly open dental impression, a carrier member is keyed for separation by relative vertical movement. An arched element has a first leg positioned in de- 15 pending relationship to the dental impression which leg is adapted to separably suspend a dowel oriented relative a tooth axis of said impression. A second leg of the arched element is received and supported in a mass of plastic material on the carrier member. 20

SUMMARY OF THE INVENTION

In the initial stages in the manufacture of dental restorations an impression is taken on the teeth of a patient’s jaw by means of moldable, usually polymerizable, impression material. In general, the impression is a Ushaped negative reproduction of the full jaw and such teeth as it includes. Using the impression as a mold, a cast of plaster is then made to reproduce, in positive form, the patient’s jaw and tooth structure as a model. According to a common technique, it is often desirable that a dowel pin be cast in place within one or more of the teeth of the model to provide means whereby sections or portions of the plaster model may be removed and replaced with accuracy during the waxing-up stages of the technique. In the prior art a variety of apparatuses have been supplied for disposing such a dowel pin in its desired upright relationship with respect to the impression and a tooth cavity. However, it is desirable during production of the model that the dowel pins be displaced from such selected position while the semi-fluid and viscous plaster is being cast in place. The common practice is to fill the impression with semi-fluid plaster and to subject the impression to a vibratory force which works the plaster into all of the quite delicately molded cavities of the impression for the purposes of insuring that the impression be filled and that all entrapped air bubbles are worked out. This having been accomplished, it is then desirable for the technician to replace the dowel pin or pins in the previously oriented relationship with respect to the impression and its cavity. This must be accomplished “blind” since then the cavities are no longer in view. The dowel pin is only partially embedded at this stage. Various means in the prior art have been employed for returning the dowel pin or pins to the same relationship that they previously occupied absent the casting plaster. After the stone has hardened, the partially embedded dowel pin is released from whatever support member may have been employed and the support means is removed. Usually a separating material is applied to the hardened stone particularly in the area around the upward protruding end of the dowel pin. Additional stone plaster is poured on the previous cast to provide a base for the tool model. When this additional stone is hard, the tooth model is usually cut and shaped to remove excess stone and to permit the model to rest on a work surface. The technician then makes thin saw cuts in the model between certain teeth down into the base sufficiently to intersect the parting line. Thereupon a section of the model may be separated and removed by withdrawing the dowel pin from its embedment in the base of the model. Thus the technician may openly work upon the one or two or more teeth, thus separated from the rest of the model. He can always return the same accurately to position on the model by reinserting a protruding end of the dowel pin into the sockets formed in the model base.

A primary object of this invention has been the provision of dowel orienting apparatus useful in dentistry in which there are dowel support means permitting accurate, firm and rapid dowel positioning to an infinite number of positions, and which are removable and returnable in such manner as to insure correct reorientation of the dowel pin after the same has been separated from a dental impression with which it was originally oriented.

Another object is the provision in dowel orienting apparatus of means in which the pins can be adjusted and securely held in any of an infinite number axes and aspects. Yet another object of the invention is the provision of a dowel orienting apparatus which is simple and inexpensive to produce and which may be used with but the simplest of tools and requiring a relatively low order of skill to obtain accurate and independent orientation of dowel pins with respect to dental impressions.

These and other objects of the invention will become apparent to those skilled in the art from the following description.

Drawings:

FIG. 1 is a perspective view of a dental impression;

FIG. 2 is a perspective view of a dowel commonly used in dentistry in the manufacture of dental restorations;

FIG. 3 is a perspective view of the components of this dowel orienting apparatus;

FIG. 4 is a plan view in substantially full scale of the assembled dowel orienting apparatus as it appears during use;

FIG. 5 is a vertical section taken in the plane of line 5—5 of FIG. 4; and

FIG. 6 is a perspective view of a dental model produced by the use of this apparatus.

Detailed description

In FIG. 1 is shown an impression tray or holder 10 which is generally horseshoe in plan and is U-shaped in cross section. In short, the holder provides a U-shaped trough into which the dentist places a plastic impression material to be applied to the patient’s jaw to take an impression thereof. In FIG. 1 the impression 12 is a negative of the actual physical conditions of the teeth and jaw of a patient. It includes tooth cavities 14. Usually the material from which the impression 12 is formed is of a resilient nature and has characteristics whereby it sets from its moldable form into a state where it may no longer be caused to permanently change shape while still retaining a degree of resiliency.

Dowel pin 16 of FIG. 2 has a tapered end 18 and a knurled end 20 to be embedded in a stone model. Usually the tapered end 18 is fully flat sided and, in some instances, the tapered end is frusto-conical and has a flat or keying side. There are a variety of such dowel pins available and commonly used by dental technicians.

The dowel orienting apparatus of this invention comprises a base member 22, a carrier member 24 and an arched element 26, as shown in FIG. 3.

The preferred form of base member 22 includes a bottom plate 28 of circular shape in the center of which is an upstanding column 30 that receives and supports a derltal impression. Wall 32 upstands from the base 28 and substantially embraces column 30. To provide access to a dental impression on column 30 at one side and for keying purposes, wall 32 is interrupted by slot 34 as best seen in FIG. 3.

3,552,018

Carrier member 24 in the preferred form of this invention fits around or encloses wall 32. Carrier 24 comprises inner wall 36 and outer wall 38, both rising from bottom 40. Walls 36 and 38 are likewise interrupted to form an opening 42 at which are end walls 44 each having instanding flanges 46 thereon. Flanges 46 engage the edges of slot 34. Carrier 24, by vertical movement, may be dropped over or removed from base member 22. The instanding flanges 46, 46 interfit with the edges of wall 32 forming slot 34. In this manner base 22 and carrier member 24 are keyed together for disassembly or reassembly by relative sliding movement of the parts. Carrier 24 in effect is a vessel, the shape of which is defined by walls 36 and 38, bottom wall 40 and end walls 44, 44. This vessel is normally filled with plastic means 58, the preferred form of which is a puttylike material that is relatively easily penetrated, moldable, heavy and non-tacky.

The arched element 26 is usually formed of wire or rod stock and, in the preferred form, is of inverted Ushape comprising a first leg 50, a cross or connector member 52 and a second leg 54. By means of a resilient tubular sleeve 56 on the lower end of leg 50, a dowel pin 16 may be secured in place for positioning during orientation and during casting of the stone model and for separation therefrom once it has been cast in place. The second leg 54 is inserted into the plastic material 58 contained in the reservoir ir vessel 25 of the carrier member 24. Positioning of the arched member is simply accomplished by pressing leg 54 into the plastic claylike material 58 at a location selected by the technician. It is desirable that leg 54 at its bottom or lower end be flared or broadened as at 55 to resist too free rotation of the leg in material 58.

METHOD OF USE

In the initial stages of the use of this apparatus a dental technician will mount the impression holder 10 on post 30 by means of a gobbet 60 of putty-like material which has been manually worked to a fairly soft moldable state and pressed or otherwise caused to adhere to the top of the column 30. The holder 10 is pressed to gobbet 60 and disposed in whatever inclination or disposition is decided upon by the technician. The dental impression 12 therein is usually mounted so that it is upwardly open and generally slanted forward toward slot 34. An arched member 26 having a dowel secured to the first leg 50 thereof, in the manner described, is placed over the dental impression with dowel pin 16 aligned in a selected aspect relative a tooth cavity .14 of the impression 12. Positioning of the arched member is obtained and maintained merely by inserting the second leg thereof into the mass 58 of plastic material in reservoir or chamber 25 of carrier member 24. Anchoring of the arch member 26 to prevent rotation about axis of leg 54 is facilitated by the use of the broadened end 55. Height at which the arched member is disposed and consequently the depth of insertion of the dowel pin 16 is governed by the depth to which second leg 54 is embedded in the material 58.

When the technician has placed the dowel pins and is ready to cast the first increment of plaster, he removes the carrier element 24 by lifting it vertically away from base 28 of member 22. The interfit is such that this is a simple sliding action. Carrier 24 with the properly oriented dowel pins still in place is set aside. The impression holder 10 and its impression 12 is then filled with freshly mixed plaster or stone and is usually placed upon a vibrator mechanism to cause the semi-fluid plas4 ter to work itself into all of the crevices and contours in impression 12. This initial cast 60 usually rises to the dotted line indicated in FIG. 5. Thereupon the technician reassembles the carrier 24 onto the base member 22 by lowering it from above until it again rests on the ^a flange 28 of base 22. In the process the dowel pins on arch elements 26 are inserted into the still soft plaster in the same predetermined orientation with respect to a tooth cavity that the technician had established before i a the plaster was poured.

When the initial cast 61 of plaster has set so that the dowel pins 26 are firmly anchored in the plaster, the apparatus may be disassembled by withdrawing.the sleeves 56 from the tapered ends 18 of the dowel pins and by 15 withdrawing the arched elements 26 from their anchored and supporting positions in the putty-like material 58 of the carrier member. At that time the technician usually applies a separating material on the hardened surface of the cast plaster about the outwardly protruding dowel pin 20 or pins. Then an additional amount of plaster is poured or molded on the initial pour and hardened to form the base 62 for the tooth model. A single tooth model 64 and portion 66 of model 61 is shown in FIG. 6 as separated from the rest of the model. The dowel 16 is with25 drawn from socket 68 and may easily be returned when desired. The utility and mode of use of this apparatus will be readily apparent to those skilled in the art.

Alternatives and modifications will occur to those haying skill in the pertinent art and all such as fall within 30 the scope of the subjoined claim is considered part of this invention.