(12) United States Patent (cid:9)
`Sachdeva et al. (cid:9)
`
`11111111111111111111111111111100611)11Ifj11111111111111111111111111
`US 6,431,863 Bl
`Aug. 13,2002
`
`(10) Patent No.: (cid:9)
`(45) Date of Patent: (cid:9)
`
`(54) ENDODONTIC INSTRUMENTS HAVING
`IMPROVED PHYSICAL PROPERTIES
`
`(76) Inventors: Rohit Chaman Lal Sachdeva, 2605
`Courtside La., Plano, TX (US) 75093;
`Farrokb Farzin-Nia, 141 W. Fairview
`Blvd., Inglewood, CA (US) 90302
`
`( • ) Notice: (cid:9)
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(3) by 1017 days.
`
`(21) Appl. No.: 08/942,732
`
`(22) Filed: (cid:9)
`
`Oct. 2, 1997
`
`Related U.S. Application Data
`
`(63) Continuation of application No. 08/453,969, filed on May
`30, 1995, now abandoned.
`
`Int. CI.7 (cid:9)
`(51)
`(52) U.S. Cl. (cid:9)
`(58) Field of Search (cid:9)
`
` A61C 5/02
` 433/102; 433/224
` 433/102,224
`
`(56) (cid:9)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,182,040 A (cid:9)
`4,600,391 A (cid:9)
`4,836,780 A (cid:9)
`4,971556 A (cid:9)
`4990,088 A (cid:9)
`
`1/1980 Bechtold, Jr.
`7/1986 Jacob
`6/1989 Buchanan
`11/1990 Blinn°
`2/1991 Weissman (cid:9)
`
`5,066,230 A
`5,125,838 A
`5,389,226 A
`5,464,362 A
`
`11/1991 Weissman
`6/1992 Seigneurin
`2/1995 Scmggs et al. (cid:9)
`11/1995 Heath et al. (cid:9)
`
`OTHER PUBLICATIONS
`
`
`
`
`205/50
`433/102
`
`II. Walia et al., "An Initial Investigation of the Bending and
`Torsional Properties of Nitinol Root Canal Files", Journal of
`Endodontics, vol. 14, No. 7, Jul. 1988, pp. 346-351.
`Croopnick, C.A. et al., "A Low Environmental—Risk
`Replacement for Chromium and Electroless Nickel", Metal
`Finishing, pp. 13-16 (Apr. 1994).
`The Kerr Endo Difference Brochure, Kerr Manufacturing
`Company, Romulus, Michigan 1991.
`
`* cited by examiner
`
`Primary Examiner—Ren Yan
`(74) Attorney. Agent, or Firm—Wcxid, Herron & Evans,
`L L P.
`
`(57) (cid:9)
`
`ABSTRACT
`
`Endodontic instruments, including tiles, reamers, and
`broaches, wherein the working shaft portion has flexibility/
`stiffness properties and hardness properties that may vary
`along its length. These variations in physical properties can
`be accomplished by utilization of specific materials having
`a prescribed amorphous phase content, by application of
`specific coatings or surface treatments, or by selective or
`differential heat treatment.
`
` 433/102
`
`3 Claims, 2 Drawing Sheets
`
`1PR2015-00632 — Ex. 1035
`US ENDODONTICS, LLC, Petitioner
`
`

`
`U.S. Patent (cid:9)
`
`Aug. 13, 2002 (cid:9)
`
`Sheet 1 of 2
`
`US 6,431,863 B1
`
`'6
`
`FIG. 2A (cid:9)
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`FIG. 2B
`
`FIG. 2C
`
`16
`
`

`
`U.S. Patent (cid:9)
`
`Aug. 13, 2002 (cid:9)
`
`Sheet 2 of 2 (cid:9)
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`US 6,431,863 B1
`
`- (cid:9)
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`DEFORMED AT
`37 °C
`
`600 (cid:9)
`
`%. 400 -
`
`200 -
`
`FIG. 4
`
`01• (cid:9)
`50.0 (cid:9)
`
`•
`
`. • I • (cid:9)
`50.5 (cid:9)
`
`I
`51.0
`
`Ni-CONCENTRATION ( AT %)
`
`600 - (cid:9)
`
`DEFORMED AT
`37 °C
`
`400-
`
`200 -
`
`17
`
`FIG.5 (cid:9)
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`.. (cid:9)
`0 """
`50.5 (cid:9)
`50.0
`
`I (cid:9)
`
`• (cid:9)
`
`• (cid:9)
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`Ta (°C)
`350
`
`400
`
`450
`
`500
`
`•
`51.0
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`RECOVERY
`STRESS CURVE
`
`FIG. 6
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`2 (cid:9)
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`4
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`6
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`STRAIN ( % )
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`

`
`US 6,431,863 B1
`
`1 (cid:9)
`ENDODONTIC INSTRUMENTS HAVING (cid:9)
`IMPROVED PHYSICAL PROPERTIES (cid:9)
`
`RELATED APPIICATION (cid:9)
`
`5 (cid:9)
`
`ao
`
`FIELD OF THE INVENTION (cid:9)
`
`The invention relates to endodontic instruments, and more (cid:9)
`particularly to such instruments having improved physical (cid:9)
`properties in the nature of combined flexibility and hardness. (cid:9)
`
`BACKGROUND OF THE INVENTION (cid:9)
`
`This application is a continuation of application Ser. No. (cid:9)
`08/453.969 filed on May 30, 1995, entitled ENDODONT]C (cid:9)
`INSTRUMENTS HAVING IMPROVED PHYSICAL (cid:9)
`PROPERTIES now abandoned. (cid:9)
`
`2
`to be due solely to any variation in dimensions of the
`working shaft; e.g., the variation in flexibility is not due
`solely to a greater diameter at one location relative to
`another location on the working shaft.
`In one aspect, the invention contemplates that at least the
`working shaft portion of the endodontic instrument, which
`may be a (cid:9)
`
`reamedle, reaer or broach, or other endodontic
`instrument, is comprised of a titanium-based alloy, or other
`alloy possessing desirable physical characteristics. Suitable
`alloys contemplated are Ni—Ti based alloys; Ni—Ti alloys
`that include Nb or Fe as an additional alloying element; and
`alloys selected from the group consisting of Ti, Zr, Mo, Co,
`and Cr-based alloys. All of the above are suitable materials
`for the endodontic instruments of the present invention so
`15 long as the alloy is at least partially amorphous. Preferably,
`the alloy is structurally greater than about 10% amorphous.
`By selecting and utilizing an appropriate partially amor-
`Endodontic instruments, particularly files, reamers and (cid:9)
`phous alloy from the noted group, the endodontic instrument
`broaches, arc used for both cleaning and shaping root canals (cid:9)
`is provided with the desired flexibility/stiffness and hardness
`during endodontic procedures. There are a variety of factors
`properties for the particular endodontic procedure.
`which dictate the required physical characteristics of such 20
`In an alternative aspect of the invention, the desired
`instruments. These include the desired stillness and/or flex-
`flexibility/stiffness and hardness properties are achieved by
`ability of the instrument, as well as the sharpness of its
`providing a coating or surface treatment on at least a portion
`cutting edges (which relates to the hardness as well as the
`of an exposed surface of the working shaft. The shaft itself
`structure of the material) coupled with certain dimensional
`25 may be a titanium-based alloy, or one of the other types of
`and design limitations for the different root canals.
`alloys noted above, and the coating or surface treatment may
`In the past, endodontic instruments have been made from (cid:9)
`be continuous or discontinuous over the working shaft.
`carbon steels and stainless steels due to the propensity of (cid:9)
`Variations in flexibility and hardness along the length of the
`these materials for maintaining adequate cutting edges, as (cid:9)
`working shaft can be achieved utilizing discontinuous or
`well as the relatively high stiffness thereof. For example, 30 intermittent coatings/surface treatments, or by variations in
`carbon steel and stainless steel endodontic instruments are (cid:9)
`coating thickness. By utilizing continuous coatings of amor-
`available from Kerr Corporation, Romulus, Michigan. (cid:9)
`phous materials, such as Amplate, available from ATI of
`Endodontic instruments constructed of such materials have (cid:9)
`Laguna Niguel, Calif., the stiffness of the tip is improved
`certain drawbacks, however, including flexibility limitations (cid:9)
`while minimizing erosion of the cutting edges. Discontinu-
`which do not allow the instrument to readily conform to the 35 ous TiN or TiAIN coatings can improve the hardness at the
`shape of a curved root canal. This inflexibility can cause (cid:9)
`cutting edges while selectively increasing the stiffness of the
`excessive, unwanted erosion of the root canal. (cid:9)
`instrument along its length.
`Recently, there have been some attempts in the endodon- (cid:9)
`In yet another aspect of the invention, the desired
`tic instrument field to address these problems. More (cid:9)
`flexibility/stiffness and hardness properties can he achieved
`particularly, titanium based alloys and Ni/Ti materials have 40 by selective or preferential heat treatment of the working
`been introduced for use in the manufacture of endodontic (cid:9)
`shaft. Particularly in the embodiment wherein the working
`instruments. For example, Seigneurin U.S. Pat. No. 5,125, (cid:9)
`shaft portion is comprised of Ni—Ti alloy, selective heat
`838 relates to endodontic canal instruments made of tita- (cid:9)
`treatment can be used to achieve the desired physical
`nium or titanium alloys. The use of materials such as (cid:9)
`properties. Additionally, adjustments to the proportions of
`titanium or Ni/Ti have certain advantages in the flexibility of 45 Ni and Ti as well as to the cold work ratio, can be
`the material. However, endodontic instruments of such (cid:9)
`advantageously used to achieve desired physical properties.
`materials may have as a drawback the lack of necessary (cid:9)
`Utilizing any one of the above techniques, the flexibility
`stiffness, particularly in small sized (diameter) instruments, (cid:9)
`and hardness of the working shaft portion can be varied
`sufficient to provide guidance in the root canals. (cid:9)
`along the length thereof, or specific hardness and/or flex-
`Furthermore, the sharpness of the cutting edges in such so ibility properties can he imparted at specific locations along
`instruments is compromised due to the lower hardness of the (cid:9)
`its length. For example, it is generally desired to have a
`material. (cid:9)
`stiffer tip in an endodontic instrument so as to provide
`What is needed is an instrument which combines the (cid:9)
`improved cutting ability at the tip and to facilitate directing
`desired stiffness and sharp edge-maintaining characteristics (cid:9)
`the instrument into the canal. Whereas the middle section of
`along with desired enhanced flexibility so as to alleviate 55 the working shaft portion of the instrument may need to be
`canal erosion, (cid:9)
`less stiff so as to improve steerability of the instrument
`through the canal, thereby minimizing erosion of the canal
`SUMMARY OF THE INVENTION (cid:9)
`walls. This minimizing of canal wall erosion is achieved due
`to the fact that as the instrument is inserted through the
`In its broadest aspects, the present invention is directed to (cid:9)
`endodontic instruments which include a working shaft por- 60 canal, the lower modulus of elasticity of the material at the
`flexed or bent portion (e.g., the middle section) produces
`don wherein the shaft portion has a modulus of elasticity that (cid:9)
`smaller forces against the canal walls, thereby minimizing
`provides enhanced flexibility along its length and yet is stiff (cid:9)
`erosion thereof.
`enough to provide the necessary guidance for the instni- (cid:9)
`ment. Furthermore, the working shaft has sufficient hardness (cid:9)
`These and other features and advantages of the present
`so the cutting edges maintain their sharpness. The shaft may 65 invention will become apparent to persons skilled in the art
`have varying flexibility and hardness properties along its (cid:9)
`upon review of the detailed description of the invention,
`length; however, the variation in flexibility (modulus) is not (cid:9)
`taken in conjunction with the drawings.
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`

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`US 6,431,863 B1
`
`5
`instruments of the present invention can be advantageously
`utilized to achieve the desired properties.
`Generally speaking, it is desired that the endodontic
`instruments according to the present invention have a hard-
`ness in the range of 20-60 Rc (Rockwell hardness scale) and
`flexibility/stiffness (as represented by the modulus of
`elasticity) in the range of 4 million to 17 million psi.
`Having now described the invention with respect to
`specific features and embodiments, persons having ordinary
`skill in the art will readily ascertain that various changes and
`modifications may be made without departing from the
`scope of the invention, as defined in the appended claims.
`What is claimed is:
`1. An endodontic instrument including a working shaft
`portion wherein said working shaft portion has varying
`stiffness/flexibility properties along at least a portion of its
`length, said variation in stiffness/flexibility not being due
`solely to any variation in dimensions or cross-sectional
`shape of said working shaft, further comprising a coating on
`at least a portion of an exposed surface of said working shaft
`portion, said coating resulting in said variation in stiffness/
`
`6
`flexibility, and wherein said coating has a thickness gradient
`along the length of said working shaft portion.
`2. An endodontic instrument including a working shaft
`portion wherein said working shaft portion has varying
`5 stiffness/flexibility properties along at least a portion of its
`length, said variation in stiffness/flexibility not being due
`solely to any variation in dimensions or cross-sectional
`shape of said working shaft wherein said variation in
`stiffness/flexibility is due to selective heat treatment of
`in portions of said working shaft portion.
`3. An endodontic instrument including a working shaft
`portion comprising a NiTi-based alloy, said working shalt
`portion having stiffness/flexibility properties that vary along
`at least a portion of its length, said variation in stiffness/
`IS flexibility not being due solely to any variation in dimen-
`sions or cross-sectional shape of said working shaft, wherein
`said alloy further includes Nb or Fe in an amount exceeding
`about 03%, and wherein said variation in stiffness/flexibility
`is due to selective heat treatment of portions of said working
`20 shaft.