An improved appliance for use in applying filler material to an endontically prepared root canal

Abstract: An improved appliance for use in applying filler material, such as gutta-percha or the like, to an endodontically prepared root canal of a tooth in the form of an elongated shaft (12) of material having high biological tolerance, the shaft having a handle portion (26) at the proximal end portion (40), the shaft distal end portion (42) having a surface configuration adaptable to retain filler material formed thereon and being positionable in a root canal, the shaft distal and proximal portion being severable from each other whereby the distal portion and filler material therein remain in the root canal. In the preferred arrangement the shaft distal portion surface is defined by a spiral groove (44).

Description: The invention concerns an appliance for applying a filler material to an endodontically prepared root canal as defined in the preamble of Claim 1. Such a device is disclosed in the Journal of Endodontics, Vol. 4, No. 6 June 1978, pages 184-188. The conventional techniques for performing endodontic therapy on teeth are time consuming and often do not adequately ensure that the entire canal system is filled with the repair material. Experience has shown that it is not possible to remove all pulpal remnants and contaminants from a root canal with current preparation techniques. If the said pulpal remnants and contaminants are thoroughly entombed in the repair material, the endodontic thereapy will be successful. If said remnants and contaminants are not thoroughly entombed, there is a high probability of failure of the endodontic therapy. Complete entombment of the remnants and contaminants requires complete obturation of the canal system. Experience has shown failure to completely obturate the canal system to be the primary cause of failure in endodontic therapy. Examples of conventional techniques are shown in FR-A-2163953, CH-A-513640 and FR-A-775073. The appliance of the present disclosure is in the form of a rigid carrier member having a proximal portion and a distal portion with the distal portion coated with gutta-percha or similar filler material. The carrier member is a tapered, slender rod. The carrier member may be constructed of any material which is of sufficient rigidity and non-toxic when left in the root canal. One material that has been employed successfully is stainless steel. A highly biocompatible plastic or metal carrier member also works successfully. According to the present invention an appliance for applying a filler material, such as gutta-percha, to an endodontically prepared root canal of a tooth, comprising an elongate shaft having a distal and proximal portion, the distal portion having a length positionable in at least substantially the full length of the root canal, being of a material of high biological tolerance, being slightly tapered in diameter towards its distal end and being adapted to receive filler material thereon and a handle formed at the shaft proximal portion, is characterized in that the distal shaft portion has a cylindrical cross-sectional configuration without auger means. In another embodiment the distal and proximal portions do not have a defined point of severance and the dentist severs the tool after the distal portion has been fully seated in a root canal. A disc-shaped washer is incorporated on the shaft of the carrier member and serves to act as a stopping plug at the coronal opening of the canal and thus to prevent viscous flow of the gutta-percha out of the said canal during the insertion process. The disc-shaped washer is also used for distance measurement. The filler material is molded to the carrier member in a tapered or conically-shaped manner so as to facilitate the introduction into the typical canal taper with sufficient material to ensure complete filling of the said canal and thereby complete obturation of the canal. The devices may be manufactured in a variety of sizes to correspond to standard endodontic files. In using the appliance of this invention the root canal is first prepared in the standard manner by broaching with endodontic files. An appliance of proper size is prepared with filler material which then may be heated over a flame so that the filler material becomes thermoplasticized. The heated appliance is then inserted into the root canal with firm apical force. The proximal of the appliance is then separated from the distal portion to leave the distal portion with the filler material thereon in the root canal. The proximal portion is then removed while holding the stopping plug or washer against the tooth and the remainder of the endodontic therapy is completed using conventional procedures. In another arrangement of the appliance, the shaft may be without a defined means of severing the proximal portion from the distal portion. In this arrangement the distal portion with filler material thereon is inserted in the root canal to the full depth. The dentist then using a rotating burr or cutter pliers severs the proximal portion from the distal portion; or the dentist may form a point of weakness by forming a notch in the shaft with a rotating burr or cutting pliers and then finish separating the distal portion from the proximal portion by bending the shaft back and forth at the point of weakness. In this manner, the appliance can be used in any depth of root canal without consideration of matching the length of the distal portion to the depth of the root canal. One of the advantages of leaving the distal portion of the carrier in the tooth, according to the principals of this invention, is that it greatly reduces the volume of filler material employed and therefor the effect of shrinkage of the filler material. For more information as to background material relating to the present invention, reference may be had to pages 184 through 188 of the Journal of Endodontics , Volume 4, No. 6, June 1978 which describes a new gutta-percha technique in which the gutta-percha is formed around an endodontic file. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which:- Fig.1 is an enlarged elevational view of the appliance or carrier member of the present invention. The appliance includes a slidable stopper or washer which is shown in cross-section. Fig.2 is an elevation as in Fig.1 showing the lower portion of the appliance as encapsulated in a conically-shaped quantity of filler material such as gutta-percha. As shown in Fig.2, the apparatus is ready for use in filling an endodontically prepared root canal. Fig.3 shows a tooth in cross-section with the root canal having been endodontically prepared and showing the appliance of this invention, in reduced scale, as being employed to apply filler material to one of the endodontically prepared roots. Fig.4 is a cross-sectional view of the tooth as in Fig.3 showing the appliance inserted into the root canal. Fig.5 shows the next step in a sequence of applying filler material to the root canal wherein the tool has been rotated to sever the proximal portion from the distal portion. Fig.6 shows the removal of the proximal portion of the appliance with the distal portion being retained in the root canal with the filler material. Fig.7 is an elevation of the appliance in which the distal portion is provided with integral projections which serve to augment retention of the filler material. Fig.8 is an embodiment of the appliance in which the distal portion has a non-circular cross-sectional configuration. Fig.9 is an elevation of the appliance showing the arrangement wherein the distal portion is severable from the proximal portion by a telescopic inner connection between the two portions and showing filler material secured on the distal portion. Fig.10 is an elevation showing the arrangement wherein the distal portion is secured to the proximal portion by means of a bonding cement. Fig.11 is a cross-sectional view of Fig.8 in which the distal portion is oval. Referring to the drawings and first to Fig .1, the appliance which is a carrier member is generally indicated by numeral 10 and is formed of an elongated shaft 12 having a proximal end 14 and distal end 16. While the shaft may be of a variety of cross-sectional configurations, the preferred and simplest shape is that of a circular cross-sectional configuration so that when the shaft is positioned in a root canal of a tooth, as will be hereinafter more specifically described, the flared end portion 18 resists rotation of the shaft. Integrally formed on the shaft are a plurality (three being shown) of spaced apart enlarged cross-sectional dimensioned portions 20A through 20C. When the shaft is circularly cross-sectional as preferred, the enlarged diameter portion 20A, 20B and 20C are also preferably an enlarged circular cross-sectional configuration. Positioned between the enlarged diameter portion 20A, and the proximal end 14 is a reduced torque resistance area 22. This is in the form, as shown, of a groove formed around the shaft. Between groove 22 and the proximal end 14 is a sliding stopper or washer 24 having an opening 24A therein which slidably receives shaft 12. Affixed to the shaft at the proximal end 14 is a handle portion 26. Handle 26 is of a diameter larger than that of a shaft 12 and may be integral with the shaft or secured to the shaft and made of a material such as plastic. Fig.2 shows the appliance ready for use in inserting a filler material into the root canal of an endodontically prepared tooth. Fig.2 shows, in cross-section, filler material 28 formed on the appliance 10. The filler material 28 may be such as gutta-percha which can be formed by hand onto appliance 10. After forming, the gutta-percha may be warmed in a flame to the proper stage. Fig.3 shows a tooth 30 having root canal 32 and 34 therein. A canal 32 has been endodontically prepared in the standard technique such as by the use of files to remove the root pulp and to prepare, as well as possible, a clean canal. Appliance 10, with the filler material 28 molded thereon, is ready for use for filling the root canal 32. The apex of the root canal is indicated at 36 with the tooth crown or coronal portion being indicated by numeral 38. Figs.4 through 6 show the continuation of the step of filling root canal 32. Fig.4 shows the appliance inserted into the canal 32. The filler material 28 is forced by the insertion of the appliance to fill the canal to the apical area 36 of the tooth. After full insertion of the appliance as shown in Fig.4, rotational torque is applied to handle 26 severing the shaft at the reduced torque resistance area 22 as shown in Fig.5. This is possible since the flared distal end 18 of the shaft resists rotation relative to tooth 30. After the shaft has been severed into two portions, the proximal portion is withdrawn. The sliding washer 24 is used to retain the filling material 28 in the canal by holding the washer downwardly as the proximal end portion of the shaft 12 is withdrawn. Fig.6 shows the proximal portion of the appliance being withdrawn. Washer 24 is then removed leaving the distal portion of the shaft in place within the root canal 32. The root canal 32 can be more completely filled by applying additional filler material and by applying mechanical or hydraulic pressure to the filler material to force it into the root canal. The coronal area of the tooth can be filled in the usual way. The depiction of the tooth 30 in Fig. 3 through 6 is merely exemplary as teeth are individualistic and the drawings are intended to exemplify the steps involved rather than to accurately pictorially represent the appearance of the tooth or root canal therein. The appliance of this disclosure thus provides a unique and very effective way of conveying filler material, such as gutta-percha, into an endodontically prepared root canal. The prior art teaches the use of a file as a carrier of filler material, however, this known method, while functioning successfuly for its intended purpose, nevertheless has limitations and problems which are overcome by the present invention. Fig.7 shows a still alternate embodiment of the invention which includes a severance point 22 which is optional as any of the embodiments can be utilized either with or without a severance means. The distal portion 42 includes integral burrs 46 extending from the surface to aid in supporting the filler material on the distal portion. Fig.8 shows the embodiment having the optional severance point 22 and wherein the distal portion 42 is of non-circular cross-section configuration. Fig.11 shows an example of such a non-circular cross-sectional configuration; having an oval cross-sectional configuration. Such a non-circular cross-sectional configuration augments the retention of filler material onto the distal portion. Fig.9 shows another embodiment of the invention which includes a defined point of separation. In Fig.9 the distal portion 42 has, at the upper end 42A thereof, a recess 48 therein. The shaft proximal portion 40 has a reduced external diameter extension portion 50 which is telescopically received within recess 48. In this manner the distal and proximal portions 42 and 40 are retained in axial alignment while the filler material 28 is being secured to the distal portion and while the distal portion with filler material thereon is inserted into the root canal. Thereafter, the proximal portion 40 is easily separable from the distal portion. Fig.10 shows a still different means of achieving separation. In this embodiment the distal upper end 42A is secured to the proximal end 40A by means of an adhesive 52. The adhesive is sufficient to retain the distal and proximal portions 42 and 40 in axial alignment while the filler material 28 is applied and while the distal portion with attached filler material is inserted into a root canal, but allow the portion to be separated by bending the proximal portion relative to the distal portion to break the adhesive 52. Thus, Figs.7 to 10 show first a variety of means of improving the retention of the filler material on the shaft distal portion. In Figs.7 to 10 various types of arrangements are provided for a preselected point of separation. In the arrangments of Figs.7 to 10 the tool is preferably predesigned both to accommodate the diameter of the root canal as well as the depth of the root canal. By //s// reference to accommodation of diameter root canal means that the appliance can be manufactured in a variety of diameters so that the dentist can select the maximum diameter which can be easily accommodated by the endodontically prepared root canal to thereby require a reduced amount of filler material whereas it can been seen; however, that only a limited number of diameters are required since there is no mandatory requirement that the diameter of the appliance distal portion closely match the diameter of the root canal. While Figs. 7 and 8 show appliances 10 with filler material formed on the distal portion 42, it is understood that such appliances may normally be supplied to dentists with the filler material pre-formed on the distal portions as in Figs.9 and 10. As previously mentioned herein, the filler material used for obturating endodontically prepared root canals may be such as gutta-percha. Gutta-percha has been the most commonly used filler material for such purpose since its introduction over 100 years ago. Gutta-percha is obtained from the latex from sapotaceous trees and is a trans-isomer of polyisoprene and differs from natural rubber due to its crystalline structure. Gutta-percha in its material state is in an "alpha" crystalline form, but when heated above 65° it becomes amorphous and melts. When it cools it returns to a "beta" crystalline state, unless cooled at a very slow rate. Thus, it is the "beta" crystalline form which is commonly used in endodontics. Further, commercially prepared gutta-percha material for endodontics is usually a mixture of gutta-percha beta crystalline form with a filler, such as zinc oxide, with other minor ingredients including heavy metal sulphates, waxes or resins to achieve the desired characteristics of the end product. In addition, gutta-percha is sometimes mechanically treated to change its physical characteristic for use in endodontics. U.S. Patent No. 4,632,977 teaches a method of plasticizing thermoplastic polymers, including gutta-percha, to change their physical characteristics. The present invention contemplates the use of filler materials of any composition or formulation which has physical and biological tolerance properties adaptable for use in obdurating root canals. The term "filler material" as used herein includes gutta-percha in either the alpha or beta crystalline state, and including compositions including mixtures of other materials with gutta-percha, or any other filler material having similar properties for use in filling endodontically prepared root canals.

Claims: An appliance for applying a filler material, such as gutta-percha, to an endodontically prepared root canal (32, 34) of a tooth (30), comprising an elongate shaft (12) having a distal (16) and a proximal (14) portion, the distal portion (16) having a length positionable in at least substantially the full length of the root canal, being of a material of high biological tolerance, being slightly tapered in diameter towards its distal end and being adapted to receive filler material (28) thereon and a handle (26) formed at the shaft proximal portion (14), characterized in that the distal shaft portion (16) has a cylindrical cross-sectional configuration without auger means. An appliance according to claim 1, characterized in that the shaft proximal (14) and distal (16) portions are in substantial alignment when the distal portion second end is secured by the bonding material to the proximal portion first end. An appliance according to claim 1, characterized in that the shaft distal portion has a first end and a second end, the shaft proximal portion has a first end and a second end, the shaft distal portion second end and the shaft proximal portion first end being configured for mating engagement with each other, a severable bonding material (22) between the shaft portion's mating surfaces and filler material formed onto the shaft distal portion.

Inventors: JOHNSON WILLIAM B, JOHNSON, WILLIAM B.
Applicants: JOHNSON WILLIAM B, JOHNSON, WILLIAM B.
Application year: 1990
Main classification: A61C5
IPC codes: A61C5