IE980671A1 - A root-former for a dental implant - Google Patents

Abstract

When replacing a tooth, which has had to be extracted, or has been lost by mishap, one of the options is to implant the socket with a titanium, cylinder implant; Lazzara [1990]. That part of the implant called the fixture is then, frequently, surrounded by natural human bone chips or by artificial bone granules, based on the mineral calcium hydroxyapatite. Granules of one of the bioactive glasses can be used also, to make up the deficiency of alveolar bone. The fixture is covered with a hood of a biocompatible membrane like P.T.F.E. or poly glycolic acid to prevent the ingression of scar fibrous tissue into the wound. Healing by osseointegration i.e. by the laying down of new bone around the fixture to secure it in position, takes place in about three to six months. After this time, the coronal end of the fixture is exposed surgically and a titanium abutment is secured to it by a screw.

Description

A Patent Specification of William Thomson MacCulloch A Root-former for a Dental Implant” Filed on August 1998.

Wm.T.MacCulloch, Springmount Road, Glanmire, Co. Cork, Ireland.

OPEN jo pi vr INSPECTION SSC·*·?. T- .o aiw RULE 23 Phone .+353.21.821699 ' -2The abutment protrudes through the whole thickness of the mucoperiosteum which covers the dental alveolar ridge, to exteriorise the implant into the mouth. A porcelain-to-metal dental crown is made to an impression of the abutment and is fixed by a screw or by · cementation to the abutment, to complete the prosthesis.

A few clinicians prefer to extract a tooth which cannot be saved and to allow the socket to heal, before implanting the new bone with an implant fixture. The demerits of this procedure are that the time taken for final healing is doubled. The labial plate of the alveolar bone will still resorb unimpeded. Alveolar bone, which supports the teeth, is under no obligation to retain its original shape or size when the teeth are lost. The bony palisade which is formed on immediate healing after tooth loss, diminishes with time to produce the ditching, which is commonly seen adjacent to the artificial teeth of dental bridges.

When a tooth socket is implanted, it is suggested, that the implant should retain all the contours of the intact alveolar bone in breadth, width and even in depth. Only then, will the correct gingival roll of gum be restored to normal, around an artificial crown.

An article by Lazzara [1993] suggested that loss of gingival contour could be delayed by using special tooth-form abutments during the osseointegration phase of implantation. The contour of the gum is,nevertheless, eventually under the control of the alveolar bone, to which it is attached; when the bone resorbs, what was once the gingival margin of the natural tooth will retract to re-establish , equilibrium. -3Object of the Invention It is the object of the invention to overcome the aforesaid disadvantage and to provide a device and method by means of which the resorption of the dental alveolar bone associated with tooth loss, can be controlled and prevented.

Summary of the Invention A root-former for a dental implant comprises a manufactured analogue of the root of a tooth through which is placed a self-tapping dental cylinder implant and when both of them are secured in an extraction tooth socket, they replace the total volume of the original root.

In the preferred embodiment, six tooth root-formers of graduated sizes can be produced to fit all sockets of human incisors, canines and premolar teeth.

Manufactured metal guides of sizes, exactly the same as the rootformers are used along with them to adjust the tooth sockets to the appropriate size of the root-former and to guide the drill to the correct alignment of the implant fixture.

After a healing period of three to six months, when the combined root-former and implant fixture are invested within the tissues of the jaw, they become integrated in new bone within the former tooth socket. An near-exact artificial replica of the original crown of the tooth is secured by a screw to the fixture. The crown is,at the same time, cemented with a silicone adhesive to the roof of the root-, former, to prevent the invasion of bacteria at the root-to-crown interface. -4By incorporating a root-former, a separate abutment need not be used, to complete the prosthesis.

The combination of root-former, cylinder implant and artificial crown constitute a near replica of the original tooth.

Brief Description of the Drawings Some embodiments of the invention are hereinafter described with reference to the accompanying, wherein: Figure 1 is an oblique elevation view of a root-former for a single rooted tooth.

Figure 2 is an elevation view of a root-former guide of the toothsocket's dimensions. The correct alignment of the drill, which would be appropriate for the root-former of Figure 1 is provided by the guide .

Figure 3 is an elevation view of a typical manufactured, threaded, and self-tapping, cylinder implant, which is made of titanium metal.

Figure 4 is of a combination of of Figures 1 and 3 in which the implant fixture secures the root-former in a tooth socket, ready for healing and integration in new bone by osseointegration.

Figure 5 shows the root-former and fixture after osseointegration, with an artificial crown in position. N.B.,the fixing screw for the crown exits through the cingulum of an anterior crown.

Figure 6 shows a root-former with an axially aligned fixture. The screw to retain the crown is accessed through the median fissure of the premolar crown. -5Figure 7 is an oblique view of a root-former with a closed roof which is suitable for osseointegration in a tooth socket,but which is intended for implantation of a fixture at a later date.

Description of the Preferred Embodiment The first embodiment of a root-former for a dental implant in accordance with the invention is shown in Figures 1 to 5 of the accompanying drawings.

The principle of the invention is to replace the space in a bony socket, of an extracted tooth [which is oval in cross-section], adjacent to an implant fixture 12 of round cross-section, with a manufactured titanium root-former 1 and so avoid the need for bone granules .

By restoring all the contours of the tooth socket, bucco-lingually, mesio-distally and even vertically the dental alveolar bone will retain the original gum contour around an artificial crown 11.

The depth of the bone to the extent of the apices of the teeth, especially in the maxilla and also above the inferior dental canal of the lower jaw, are preserved.

Because, human teeth vary in size from tooth to tooth and from individual to individual, it is suggested that a range of root-formers 1 can be designed from a survey of the natural teeth, which were measured by Black G.V. in 1902 and by others subsequently. A range of six root-formers 1 will fit most single rooted teeth and include the premolars 13. -6The design of the root-formers 1 should be: a] vented 2 around the fixture 12, as much as possible, so that new bone growing in from the walls of the socket and around the fixture 12 is not impeded. b] The surface 3 of the root-former 1 should be sandblasted or etched to encourage accretion of bone. Only the roof 4 and two mm. of the collar 5 should be metallographically polished, the intention being to allow for some peri-implant recession. c] The roof 4 of the root-former 1 has a countersunk hole 6 to accept the countersunk head 7 of the fixture 12. d[ A root-former 1 and its appropriate guide 8 will direct the fixture 12 at an angle 9 of ten degrees to the vertical axis of the original tooth, in order to bring the retaining screw 10 through the cingulum 17 of the artificial crown 11. Where the root-former 1 is intended for a posterior tooth [premolars 13 and molars], the guide 8 / and the hole 6 in the root-former 1 for the fixture 12, will follow the vertical axis of the tooth. The hole 6 for the screw 10 to retain the crown 11 will exit through the median fissure 14 of the crown.

From this range of root-formers 1, an appropriate one which either fits or is slightly oversize can be chosen. An estimation of the required size can be made from the extracted tooth, or if this is not available, by using a depth gauge from one of the present cylinder implant systems. -7It is intended to issue root-formers 1 in duplicate, that is along with a guide 8 which is the exact outer dimension of the rootformer 1, but it has a hole 15 down its length, to direct a drill 16 into the bone at the apex of original tooth to prepare it to accept a self-tapping, cylinder implant fixture 12 of a size longer than the root-former 1. The tooth socket may have to be adjusted surgically to accept a root-former 1. Only slight modification should be necessary to make the guide 8 fit accurately and the labial plate of bone should not be adjusted. When the guide 8 is in the socket a drill 16 is directed by the guide 8 at an angle 9 of 10? to the vertical axis of previous tooth to make certain that the screw 10 to retain the artificial crown 11 exits through the cingulum 17 of the crown 11 of an anterior tooth and not through the incisal edge.

The root-former 1 is inserted into the prepared socket, checked for fit and a cylinder implant fixture 12 of at least the same length as the original tooth is self-tapped into the prepared hole. The fixture 12 locates and secures the root-former 1 in position.

A cover of a biocompatible material like P.T.F.E.,and which fits onto the whole surface of root-former 1 and fixture 12 end,is retained in position by a screw 10 into the abutment hole 18 of the fixture 12. Into the mouth of the socket, a piece of freeze-dried skin is stitched to keep the gum margin in the same location, which it had with the original tooth. -8A temporary bridge can be 'attached to the adjacent teeth while osseointegration takes place.

After three to six months, the osseointegrated root-former 1 and fixture 12 are exposed surgically. A porcelain-to-metal crown 11 is produced to the identical size and colour of the original tooth, to fit the root-former 1 and the end of the fixture 12. The crown 11 is secured to the fixture 1 by a screw 10 through the cingulum 17 of the crown 11. A medical grade siloxane cement can be used at the same time, to prevent leakage of saliva into the root-former 1 and crown 11 interface 19 . Both surfaces can be primed e.g. by Silicoating to enhance adhesion and seal. Cementation avoids a focus of infection at the junction 19 below the gum margin.

Description of the Second Embodiment The second embodiment of a root-former 1 for a dental implant in accordance with the invention is, in nearly all respects, identical to that described for the preferred embodiment, but the fixture.is aligned vertically, so that the screw 10 to retain the crown 11 exits through the median fissure 14 of the crown 11 of a premolar 13 or molar replacement. Figure 6.

The guide 8 for such an root-former 1 directs the drill 16 vertically instead of obliquely at 10°.

This embodiment of the invention can, also be used with incisor and canine sockets, if a taper abutment into the fixture 12 is used. With a taper abutment,no fixing screw 10 for the crown 11 is used. The crown 11 is cemented to the abutment. -9Description of the Third Embodiment The third embodiment of a root-former 1 for a dental implant in accordance with the invention, is shown in Figure 7 of the accompanying drawings .

This is a of root-former 1 similar to that described in the preferred embodiment but there is no hole 6 in the roof 4 of the root-former 1. Root-formers 1 of this type are intended for tooth sockets or prepared holes in the dental alveolus. They are implanted and allowed to osseointegrate in their own right. They can have a fixture 12 placed through them at a later date, or they can be left to prevent the bone from resorbing.

Claims (9)

1. Claims:- , '

1. A device known as a root-former, can be made by a manufacturer from a biocompatible material and along with the fixture of a cylinder 5 dental implant of the same material, they can replace, almost totally, the root of a natural tooth.

2. A device or root-former of claim 1 can be made from the metal or alloys of titanium, tantalum, zirconium, niobium, hafnium and gold, as well as from the surgical steels and Stellite alloys. The surfaces 10 of the device can be etched, anodised, enamelled, plasma-sprayed, PV and CV deposited etc., to improve bone accretion or to colour the surface to simulate tooth enamel or dentine. Ceramics can be used.

3. A device of claim 1, can be made by machining a rod, drawn from tube, or swaged from sheet. Casting or sintering can be used. 15

4. A device of claim 1 which is made in different sizes. The sizes of the device can be calculated and the shapes designed geometrically from the dimensions of natural teeth. A range of about six will cover all the anterior and premolar sockets. The one which is used should be slightly larger than the root of the original tooth. 20 5. A device of claim 4, which is issued with a guide to the size of the root-former and which is used to adjust the tooth socket and also to direct a drill into the apical bone for placing the fixture. 6. A device of claim 4, which can be used to accept a dental crown, without an intervening abutment. An abutment can be used, if it is 25 appropriate. 7. A device of claim 6 which can be sealed with a biocompatible adhesive between the root-former and the crown, e.g.a medical grade poly siloxane. -118. A device of claim 4, which can be used alone to obturate a tooth socket or in a prepared hole, cut in the alveolus, or in a ridgesplitting procedure, and which can be allowed to osseointegrate and then be implanted with an implant fixture later; or it can be left,

5. Without a fixture, to retain the bone of the dental alveolar ridge.

6. 9. A device of claim 4, whose principles could be used to advantage on existing implant systems e.g.as described in G.B.Patent Application 2,252,501A 1992. Implants could be made in sizes related to those of human teeth. They could be made oval in cross-section to fit the

7. 10 sockets. Abutments could be placed obliquely in implants for incisor and canine teeth. Refernces:Black G.V. {1902] in An Atlas of Tooth Form, Wheeler R.C.,

8. 15 W.B.Saunders Company, London, 1962. G.B. Patent Application 2,252,501A 1992. Lazzara R.J. [1990] Immediate Implant Placement into Extraction Sites: Surgical and Restorative Analysis, International Congress in Oral, Orthopedic and Maxillo-facial Restoration [2nd 1990 : Mayo

9. 20 Medical Center ], Quintessence Publishing Co., Inc. Chicago. Lazzara R.J. [1993] Managing the Soft Tissue Margin:The Key to mplant Aesthetics, Practical Periodontics and Aesthetic Dentistry Vol 5,No5 1993 .