`
`TRANSMITTAL LETTER TO THE UNITED STATES
`
`aaa aN
`DESIGNATED/ELECTED OFFICE (DO/EO/US)
`CONCERNINGA FILING UNDER 35U.S.C.371
`2 Application
`No.
`
`INTERNATIONAL APPLN. NO.
`INTERNATIONALFILING DATE
`PRIORITY DATE CLAIMED
`
`PCT/B2013/001191 January 30, 2013 June 7, 2013
`
`TITLE OF INVENTION:
`INSTRUMENT FOR DRILLING DENTAL ROOT CANALS
`
`Attorney Docket No.
`
`
`
` Applicant herewith submits to the United States Designated Elected Office (DO/EO/US) the following items and
`
`
`
`okWON>KkKeAOORWWOWOOO’*®R’°*XeRwROW
`
`
`
`APPLICANT(S) FOR DO/EO/US: 1) Gilbert ROTA 2) Paul-Henri VALLOTTON
`
`other information:
`
`This is a FIRST submission of items concerning a filing under 35 U.S.C. 371.
`This is a SECOND or SUBSEQUENT submission of items concerning a filing under 35 U.S.C. 371.
`This is an express request to begin national examination procedures (35 U.S.C. 371 (f)).
`The US has been elected (Article 31).
`A copy of the International Application asfiled (35 U.S.C. 371 (c)(2))
`C1 is attached hereto (required only if not communicated by the International Bureau).
`KX] has been communicated by the International Bureau. See attached PCT/IB/308 (Second Notice).
`C1 is not required, as the application wasfiled in the United States Receiving Office (RO/US)
`An English language translation of the International Application as filed (85 U.S.C. 371 (c)(2))
`IX]
`is attached hereto.
`[1] has been previously submitted under 35 U.S.C. 154(d)(4).
`An oath or declaration of the inventor(s) (35 U.S.C. 371(c)(4)).
`A Declaration of Inventorship for purposesof U.S.A. designation pursuant to rule 4.17(iv).
`Applicant claims small entity status. See 37 CFR 1.27.
`Information Disclosure Statement (IDS) w/PTO-1449 - [X] Copyof IDScitations. - K] PCT/ISA/210
`International Search Report included.
`Assignment Papersfiled via EFS.
`A preliminary amendment.
`An Application Data Sheet under 37 C.F.R. 1.76.
`Abstract.
`
`A substitute specification.
`A computer-readable form of the sequencelisting in accordance with PCT Rule 13ter.2
`and 37 CFR 1.821 - 1.825.
`
`11.
`
`12.
`
`13.
`
`14.
`
`15.
`
`16.
`
`17.
`
`18.
`
`19.
`
`Other items or information: International Publication No. WO 2014/118591 (cover page only)
`The requiredfiling fees are being paid online simultaneously herewith by credit card.
`The Director is hereby authorized in this, concurrent, and future submissions, to charge paymentor credit any
`overpayment to Deposit Account No. 25-0120 for any additional fee required under 37 C.F.R. §§ 1.16, 1.17, or 1.492.
`
`SEND ALL CORRESPONDENCE TO:
`YOUNG & THOMPSON
`209 Madison Street
`Suite 500
`Alexandria, VA 22314
`Telephone:
`(708) 521-2297
`Facsimile:
`(703) 685-0573
`Young &Thompson’s Customer No. 00466
`BC/nmb
`
`/Benoit Castel/
`Signature
`
`Benoit Castel, Reg. No. 35,041
`Name,Registration Number
`
`12 June 2015
`Date
`
`Page 1 of 1
`
`Y &T October 2009
`
`Edge Endo Ex. 1002
`Page 1
`
`Edge Endo Ex. 1002
`Page 1
`
`

`

`
`
`TRANSMITTAL LETTER TO THE UNITED STATES
`
`aaa aN
`DESIGNATED/ELECTED OFFICE (DO/EO/US)
`CONCERNINGA FILING UNDER 35U.S.C.371
`2 Application
`No.
`
`INTERNATIONAL APPLN. NO.
`INTERNATIONALFILING DATE
`PRIORITY DATE CLAIMED
`
`PCT/B2013/001191 January 30, 2013 June 7, 2013
`
`TITLE OF INVENTION:
`INSTRUMENT FOR DRILLING DENTAL ROOT CANALS
`
`Attorney Docket No.
`
`
`
` Applicant herewith submits to the United States Designated Elected Office (DO/EO/US) the following items and
`
`
`
`okWON>KkKeAOORWWOWOOO’*®R’°*XeRwROW
`
`
`
`APPLICANT(S) FOR DO/EO/US: 1) Gilbert ROTA 2) Paul-Henri VALLOTTON
`
`other information:
`
`This is a FIRST submission of items concerning a filing under 35 U.S.C. 371.
`This is a SECOND or SUBSEQUENT submission of items concerning a filing under 35 U.S.C. 371.
`This is an express request to begin national examination procedures (35 U.S.C. 371 (f)).
`The US has been elected (Article 31).
`A copy of the International Application asfiled (35 U.S.C. 371 (c)(2))
`C1 is attached hereto (required only if not communicated by the International Bureau).
`KX] has been communicated by the International Bureau. See attached PCT/IB/308 (Second Notice).
`C1 is not required, as the application wasfiled in the United States Receiving Office (RO/US)
`An English language translation of the International Application as filed (85 U.S.C. 371 (c)(2))
`IX]
`is attached hereto.
`[1] has been previously submitted under 35 U.S.C. 154(d)(4).
`An oath or declaration of the inventor(s) (35 U.S.C. 371(c)(4)).
`A Declaration of Inventorship for purposesof U.S.A. designation pursuant to rule 4.17(iv).
`Applicant claims small entity status. See 37 CFR 1.27.
`Information Disclosure Statement (IDS) w/PTO-1449 - [X] Copyof IDScitations. - K] PCT/ISA/210
`International Search Report included.
`Assignment Papersfiled via EFS.
`A preliminary amendment.
`An Application Data Sheet under 37 C.F.R. 1.76.
`Abstract.
`
`A substitute specification.
`A computer-readable form of the sequencelisting in accordance with PCT Rule 13ter.2
`and 37 CFR 1.821 - 1.825.
`
`11.
`
`12.
`
`13.
`
`14.
`
`15.
`
`16.
`
`17.
`
`18.
`
`19.
`
`Other items or information: International Publication No. WO 2014/118591 (cover page only)
`The requiredfiling fees are being paid online simultaneously herewith by credit card.
`The Director is hereby authorized in this, concurrent, and future submissions, to charge paymentor credit any
`overpayment to Deposit Account No. 25-0120 for any additional fee required under 37 C.F.R. §§ 1.16, 1.17, or 1.492.
`
`SEND ALL CORRESPONDENCE TO:
`YOUNG & THOMPSON
`209 Madison Street
`Suite 500
`Alexandria, VA 22314
`Telephone:
`(708) 521-2297
`Facsimile:
`(703) 685-0573
`Young &Thompson’s Customer No. 00466
`BC/nmb
`
`/Benoit Castel/
`Signature
`
`Benoit Castel, Reg. No. 35,041
`Name,Registration Number
`
`12 June 2015
`Date
`
`Page 1 of 1
`
`Y &T October 2009
`
`Edge Endo Ex. 1002
`Page 2
`
`Edge Endo Ex. 1002
`Page 2
`
`

`

`INSTRUMENT FOR DRILLING DENTAL ROOT CANALS
`
`Docket No. 5001-1489
`
`The object of the present invention is an instrumentfor drilling dental root canals.
`
`The treatment of an infected dental root is carried out by extracting the pulp using
`
`special instruments, then by shaping the root canal using successivedrilling
`
`procedures, traditionally carried out with instruments of varying size and conicity. The
`
`final operation consistsoffilling the root canal.
`
`10
`
`The shaping of the root canal consistsinitially of enlarging the canalin its crown and
`
`medial parts to permit, as a second step, easier treatment of the apical part of the canal
`
`by mechanical cleaning the infected tissues.
`
`An instrument designedfor drilling dental root canals generally has a taperedrodfitted
`
`15
`
`into a handle to permit it to be driven manually or mechanically and comprising, on at
`
`least part of its length, helicoidal flutes with a constant or non-constant pitch, and
`
`having at least one cutting edge.
`
`Used in continuous rotation, this type of instrument may have a tendencyto screwitself
`
`20
`
`into the canal. Apart from the screwing action, another problem occurring in the
`
`production of instrumentsfor drilling root canals is that of the strength andflexibility of
`
`the instruments. Indeed, whenthe instrumentis too flexible it may bend or break before
`
`the practitioner has been able to complete the operation and when the instrument is too
`
`rigid, it follows the curvature of the dental root canal only with difficulty.
`
`25
`
`Numerous instruments have been developedin response to these problems. Document
`
`EP 1 361 831 describes an instrumentfor drilling dental canals comprising a base, a
`
`cutting section and a guiding section, the cutting section being defined by an envelope
`
`of a cylindrical or conical shape, the longitudinal axis of which coincides with the axis of
`
`30
`
`rotation of the instrument. The cutting section has clearance zones disposed set-back
`
`with respect to the envelope, alternating with drilling zones disposed on said envelope.
`
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`

`

`Docket No. 5001-1489
`
`This alternating arrangement of zones on the envelope and set back from the envelope
`
`makesit possible to reduce the risk of screwing the instrumentinto the dental canal.
`
`Furthermore, the axis of the cutting section can be offset with respect to the axis of the
`
`envelope. This makesit possible to deepen the clearance zones and to make the
`
`evacuation of the debris during treatment moreeffective.
`
`Document US 7 955 078 describes an endodontic instrument for preparation of dental
`
`root canals comprising a body shaped to turn about an axis of rotation. The body has a
`
`centre of mass whichis not located on the axis of rotation of the instrument, thus giving
`
`10
`
`the impression that the instrument is undulating ("Swaggering") when it is rotated. An
`
`instrument suchasthis has greaterflexibility and thus makesit possible to follow the
`
`complex curves of a dental root canal mosteffectively.
`
`However, in these two documentsthe axis of the active part is offset with respect to the
`
`15
`
`axis of rotation of the instrument over the whole length of said active part and in
`
`particular the axis of the point of the instrumentis offset. This can generate a beating
`
`motion of the point within the canal. It thus becomesdifficult to ensure optimum
`
`dimensioning of the canal during treatment, in particular in its apical portion. Moreover,
`
`a point with its axis offset also has the disadvantage of pushing the debris back
`
`20
`
`towardsthe apical portion rather than evacuating it towardsthe top of the canal.
`
`The aim of the present invention is to produce an instrumentfor drilling dental root
`
`canals which obviates the stated disadvantages. In particular, one aim of the present
`
`invention is thus to produce an instrument whichis flexible while being strong, reliable
`
`25
`
`and effective and which makesit possible at the same time to respectthe initial path of
`
`the root canal to be treated and to ensure optimum dimensioning of the canalin its
`
`apical portion after treatment.
`
`The object of the present invention is an instrumentfor drilling dental root canals as
`
`30
`
`claimed in claim 1.
`
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`

`

`Docket No. 5001-1489
`
`The drawings schematicallyillustrate by way of example a plurality of embodiments of
`
`the instrument in accordance with the invention.
`
`Figure 1 illustrates a first embodimentof an instrumentfor drilling dental root canals in
`
`accordancewith the invention.
`
`Figure 2 is a cross-sectional view atthe lineII-Il of the instrument shownin figure 1.
`
`Figure 3 is a cross-sectional view atthe lineIII-III of the instrument shownin figure 1.
`
`10
`
`Figure 4 is a cross-sectional view atthe line IV-IV of the instrument shownin figure 1.
`
`Figure5illustrates a second embodimentof an instrumentfor drilling dental root canals
`
`in accordance with the invention.
`
`15
`
`Figure 6 is a cross-sectional view atthe line VI-VI of the instrument shownin figure 5.
`
`Figure 7 is a cross-sectional view atthe line VII-VII of the instrument shownin figure 5.
`
`20
`
`Figure 8 illustrates a third embodimentof an instrumentfor drilling dental root canals in
`
`accordancewith the invention.
`
`Figure 9 is a cross-sectional view at the line A-A of the instrument shownin figure 8.
`
`25
`
`Figure 10 is a cross-sectional view at the line B-B of the instrument shownin figure 8.
`
`Figure 11 is a cross-sectional view at the line C-C of the instrument shownin figure 8.
`
`Figure 12 is a cross-sectional view at the line D-D of the instrument shownin figure 8.
`
`30
`
`Figure 13 is a cross-sectional view at the line E-E of the instrument shownin figure 8.
`
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`

`

`Docket No. 5001-1489
`
`Figure 14 is a cross-sectional view at the line F-F of the instrument shownin figure 8.
`
`In a first embodiment shownin figure 1 the instrument in accordancewith the invention
`
`comprises a rod 1 fitted at one of its ends 1a in a handle 2 permitting either manual
`
`actuation of the instrument or preferably its engagementin a hand-held part providing
`
`mechanicaldriving of the said instrument. In particular, the instrument 1
`
`is intended to
`
`be driven in rotation about its axis of rotation R.
`
`10
`
`The rod 1 has an active part 1b extending to the other end 3 - the point 3 - of the rod 1.
`
`Said active part 1b is preferably tapered and conical, narrowing to the point 3 of the rod
`
`1. Alternatively, the active part 1b or the whole rod 1 could becylindrical rather than
`
`conical.
`
`15
`
`The active part 1b has a polygonal cross-section (the sides of which are straight or
`
`curved) and comprises cutting edges. More particularly in this first embodiment, the
`
`active part 1b has, overits whole length, a square cross-section 4 forming four cutting
`
`edges 5a, 5b, 5c, 5d defining between them four helicoidal flutes 6, one flute being the
`
`face defined between two successivecutting edges of the active part 1b. The active
`
`20
`
`part 1b is defined by an envelope 7 whichis substantially tapered and hasits
`
`longitudinal axis coinciding with the axis of rotation R of the instrument.
`
`The particular feature of the instrument in accordance with the invention residesin the
`
`fact that the active part 1b hasa first portion 1c extending from the point 3 towards the
`
`25
`
`rear of the active part 1b and of which the centre of massis located on the axis of
`
`rotation R of the instrument and a second portion 1d extending from the endofthe first
`
`portion 1c to the rear of the active part 1b and of which at least one cross-section has a
`
`centre of mass which is not located on the axis of rotation R of the instrument but is
`
`offset with respect to said axis R. In the first embodiment shownin figures 1 to 4, any
`
`30
`
`cross-section of the second portion 1d of the active part 1b of the instrument 1 has a
`
`centre of mass whichis not located on the axis of rotation R but is offset with respectto
`
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`

`

`Docket No. 5001-1489
`
`said axis.
`
`More precisely, and as shownin figure 2, in accordance with the invention any cross-
`
`section 4a of the first portion 1c has its centre of mass ma on the axis of rotation R of
`
`the instrument. Moreover,in this first embodiment the four edges 5a, 5b, 5c, 5d of such
`
`a cross-section 4a are located on the envelope 7. Thus the first portion 1c and in
`
`particular the point 3 are centred with respect to the axis of rotation R of the instrument
`
`or in other wordsthe longitudinal axis of the first portion 1c coincides with said axis of
`
`rotation R.
`
`10
`
`As shownin figures 3 and 4, in the first embodiment, any cross-section 4b of the
`
`second portion 1d of the active part 1b has its centre of mass mb offset with respectto
`
`the axis of rotation R of the instrument and preferably a single cutting edge 5a of such
`
`a cross-section 4b is located on the envelope 7, the other cutting edges 5b, 5c and 5d
`
`15
`
`being disposed inside said envelope 7. Thus in the first embodiment the whole of the
`
`second portion 1d of the active part 1b is off-centre with respect to the axis of rotation R
`
`of the instrument.
`
`Thus an effective instrument is obtained becauseits point 3 is centred, does not
`
`20
`
`generate any beating within the canal and hasfour active cutting edges.
`
`Such an instrument in accordance with the invention can be obtained from a rod with a
`
`circular cross-section, preferably made from a nickel-titanium alloy, by providing therein
`
`helicoidal flutes by machining (milling), these flutes defining cutting edges such that the
`
`25
`
`cross-section of the rod 1
`
`is polygonal over the whole length ofits active part 1b. In
`
`order to achieve the particular geometry of the active part 1b in accordance with the
`
`invention, the flutes 6 of the second portion 1d of the active part 1b are overcut with
`
`respectto the flutes 6 of the first portion 1c in order to obtain at least one cross-section
`
`4b of said secondportion 1d of which at least one cutting edge is set back within the
`
`30
`
`envelope 7 and of which the centre of mass mb is offset with respectto the axis of
`
`rotation R. Thus on the second portion 1d of the active part 1b material is removed
`
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`

`

`Docket No. 5001-1489
`
`from the instrument in accordance with the invention, which makesit moreflexible on
`
`this second portion than a traditional instrument which would have, over its whole
`
`active part, a cross-section with its centre of mass centred on the axis of rotation and
`
`all its edges inscribed on the envelope. Byvirtue of the present invention, an instrument
`
`is obtained whichis effective at its point 3 while being flexible.
`
`Preferably,in the first embodiment, the second portion 1d has a progressive offset with
`
`respectto the axis of rotation R in the direction of the rear of the instrument: i.e. a
`
`cross-section of the second portion 1d closeto the point has its centre of mass less
`
`10
`
`offset proportionally to the surface of the cross-section with respectto said axis of
`
`rotation R than a cross-section of the second portion 1d closer to the rear of the
`
`instrument. In terms of machining the instrument, this producesflutes 6 which are
`
`overcut proportionally more and more along the secondportion 1d of the active part 1b
`
`with respectto the flutes of the first portion 1c. Thus in this first embodiment the
`
`15
`
`flexibility of the instrumentis adjustable and in particular increases progressively
`
`towards the rear of the active part 1b.
`
`Preferably, the first portion 1c of the active part extends over a length of 3 millimetres
`
`starting from the point 3 of the active part 1b. In a still more preferred manner, saidfirst
`
`20
`
`portion 1c has a length of 1 millimetre.
`
`Figures 5 to 7 show a second embodimentof an instrument in accordancewith the
`
`invention in which the active part 1b has, over its whole length, a rectangular cross-
`
`section 4' forming four cutting edges 5a, 5b, 5c, 5d defining four helicoidal flutes 6, one
`
`25
`
`flute being the face defined between two successive cutting edges of the active part 1b.
`
`Asin the first embodiment, the active part 1b is defined by an envelope 7 whichis
`
`substantially tapered and has the axis of rotation R of the instrumentasits longitudinal
`
`axis.
`
`The active part 1b also hasafirst portion 1c extending from the point 3 towards the
`30
`
`rear of the active part 1b and having its centre of mass located on the axis of rotation R
`
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`

`

`Docket No. 5001-1489
`
`of the instrument and a second portion 1d extending from the endofthe first portion 1c
`
`to the rear of the active part 1b and of which at least one cross-section has a centre of
`
`massoffset with respect to the axis of rotation R of the instrument. Preferably, and as
`
`in the first embodiment, any cross-section of the second portion 1d of the instrumentin
`
`accordancewith the second embodiment has a centre of mass offset with respect to
`
`the axis of rotation R.
`
`In this second embodiment, and as shownin figure 6, any cross-section 4'a of the first
`
`portion 1c is square and hasits centre of mass m’a on the axis of rotation R of the
`
`10
`
`instrument. Furthermore, the four edges 5a, 5b, 5c, 5d of such a cross-section 4'a are
`
`located on the envelope7 of the instrument. As shownin figure 7, any cross-section 4'b
`
`of the second portion 1d of the active part 1b hasits centre of mass m'b offset with
`
`respectto the axis of rotation R of the instrument. In contrast to the first embodiment,
`
`for each cross-section 4'b of the second portion 1d of the active part 1c of the
`
`15
`
`instrument in accordance with the second embodiment, two cutting edges 5a and 5b
`
`are on the envelope7, the two other cutting edges 5c and 5d being disposedinside
`
`said envelope 7.
`
`The other considerations relating to the first embodiment remain valid for this second
`
`20
`
`embodiment.
`
`As shownin figures 6 and 7, the cross-sections 4'a and 4'b of the first and second
`
`portions 1c, 1d are not necessarily symmetrical, the cross-section 4'a preferably being
`
`square, while the cross-section 4'b may be rectangular.
`
`25
`
`Figures 8 to 14 showathird embodimentof an instrument in accordance with the
`
`invention, in which the active part 1b of the instrument has, overits whole length, a
`
`polygonal cross-section 40 of a parallelogram shape, forming four cutting edges 51, 52,
`
`53, 54 defining four helicoidal flutes 6, one flute being the face defined between two
`
`30
`
`successive cutting edges of the active part 1b. As in the previous embodiments, the
`
`active part 1b is defined by an envelope7 which is substantially tapered and has the
`
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`

`

`Docket No. 5001-1489
`
`axis of rotation R of the instrumentasits longitudinal axis.
`
`In accordancewith the invention, the active part 1b hasa first portion 1c extending from
`
`the point 3 towardsthe rearof the active part 1b and having its centre of mass located
`
`on the axis of rotation R of the instrument. In this third embodiment, and as shownin
`
`figure 9, any cross-section 40aofthe first portion 1c is in the form of a parallelogram
`
`and hasits centre of mass moa on the axis of rotation R of the instrument. Moreover,
`
`in this embodiment, two diagonally opposed cutting edges 52, 54 of such a cross-
`
`section 40a are located on the envelope7 of the instrument, while the other pair of
`
`10
`
`diagonally opposed cutting edges 51, 53 is located set back within the envelope7.
`
`In accordancewith the invention, the active part 1b also has a second portion 1d
`
`extending from the endofthe first portion 1c to the rear of the active part 1b, of which
`
`at least one cross-section has a centre of mass which is not located on the axis of
`
`15
`
`rotation R of the instrument but whichis offset with respect to said axis R. In the third
`
`embodimentof the invention, and as shownin figures 8 and 10 to 14, the second
`
`portion 1d has an alternating arrangementoffirst zones - off-centre zones 11 - in which
`
`any cross-section 401b has a centre of mass m.o1b offset with respectto the axis of
`
`rotation R of the instrument and second zones- centred zones 12 - in which any cross-
`
`20
`
`section 402b has a centre of mass Moab located on the axis of rotation R of the
`
`instrument. The zone of the second portion 1d directly adjacent to thefirst portion 1c of
`
`the active part 1b of the instrumentis an off-centre zone 11 (see figure 8).
`
`Figures 11 and 13 each showacross-section 402b of a centred zone 12 located along
`
`25
`
`the secondportion 1d of the active part 1b of the instrument, while figures 10, 12 and
`
`14 each show a cross-section 401b of an off-centre zone 11 located along said second
`
`portion 1d.
`
`Preferably, and as shownin figures 11 and 13, for each cross-section 402b of a
`
`30
`
`centred zone 12, two diagonally opposed cutting edges 52, 54 are located on the
`
`envelope7 of the instrument, while the other pair of diagonally opposed cutting edges
`
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`
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`
`

`

`Docket No. 5001-1489
`
`51, 53 is located set back within the envelope 7.
`
`In a similar, preferred manner, and as shownin figures 10, 12 and 14, for each cross-
`
`section 401b of an off-centre zone 11, a single cutting edge 52, 54 appertaining to the
`
`pair of diagonally opposed cutting edges 52, 54 located on the envelope along the first
`
`portion 1c of the active part 1b of the instrumentis located on the envelope7 of the
`
`instrument, while the other cutting edges are located set back within the envelope7.
`
`Thus, apart from the alternation between the centred and off-centre zones 12,11 on the
`
`10
`
`second portion 1d of the active part 1b of the instrument, in this third embodiment, said
`
`second portion 1d also has an alternating arrangement between the cutting edges
`
`located on the envelope. The succession of the different zones on the second section
`
`1d of the instrument in accordance with the third embodiment can be described as
`
`follows:
`
`15
`
`e
`
`Thefirst zone of the second portion 1d immediately adjacentto the first
`
`portion 1c of the active part 1b of the instrumentis an off-centre zone 11. For
`
`eachcross-section 401b ofthis off-centre zone 11, only one of the two
`
`diagonally opposed cutting edges 52, 54 located on the envelope7 for any
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`cross-section 40a of the first portion 1c - the first cutting edge 52 - is located
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`20
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`on the envelope 7 of the instrument, the second of these cutting edges 54
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`and the second pair of diagonally opposed cutting edges 51, 53 being set
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`back within the envelope 7 (figure 10);
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`e
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`The second zone is a centred zone 12. For each cross-section 402b ofthis
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`centred zone 12, the first and second diagonally opposed cutting edges 52,
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`25
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`54 are again on the envelope7 of the instrument, the second pair of
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`diagonally opposed edges 51, 53 still being set back within the envelope 7
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`(figure 11);
`
`e
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`The third zone is again an off-centre zone 11. However,in this zone the
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`second cutting edge 54 diagonally opposedto thefirst 52 and which wasset
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`30
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`back within the envelope onthe first zone is now located on the envelope7,
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`while the first cutting edge 52 is then located within the envelope7, the
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`second pair of diagonally opposed cutting edges 51, 53 still being set back
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`within the envelope 7 (figure 12).
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`Docket No. 5001-1489
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`The following zone shownin figure 13 is similar to the first zone and the alternating
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`arrangement thus extends along the second portion 1d of the active part 1b of the
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`instrument.
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`Thus the instrument in accordancewith the third embodiment has twocutting edges 52,
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`54 which are located on the envelope for any cross-section 40aofthe first portion 1c of
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`10
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`the active part 1b and for any cross-section 402b of the centred zones 12 of the second
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`portion 1d of the active part 1b but of which at least one of the twois set back within the
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`envelope 7 for any cross-section 401b of an off-centre zone 11 of the secondportion
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`1d, two off-centre zones 11 separated by a centred zone 12 not having the same
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`cutting edge on the envelope7.
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`15
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`In variations, the second pair of diagonally opposed cutting edges 51, 53 could be
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`located on the envelope7 of the instrument for any cross-section of the active part 1b
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`or for any cross-section of the first portion 1c or for any centred cross-section 12 of the
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`second portion 1d. The second pair of diagonally opposed cutting edges 51, 53 could
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`20
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`also follow the same alternating arrangement described aboveasthe first pair of
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`cutting edges 52, 54 along the second portion 1d of the active part 1b of the instrument.
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`The other considerations relating to the first two embodiments remain valid for this third
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`embodiment.
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`25
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`In particular, the first portion 1c of the active part preferably extends over a length of 3
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`millimetres from the point 3 of the active part 1b. In a still more preferred manner, said
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`first portion 1c has a length of 1 millimetre.
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`30
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`Thus asin the first two embodiments described above, the instrument in accordance
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`with the third embodimentis effective since it has a point 3 which is centred and does
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`10
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`Docket No. 5001-1489
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`not generate beating in the canal and permits precise shaping of said canal. Said
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`instrumentis also flexible at the rear owing to the presenceofthe off-centre zones on
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`the secondportion 1d ofits active part 1b. However, in contrastto thefirst two
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`embodimentsin which the whole of the second portion 1d is off-centre and thus may
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`generate a beating motion at the rear of the instrument, the alternating arrangementof
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`centred and off-centre zones as described in the third embodiment makesit possible to
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`ensurethat the instrumentis flexible while avoiding beating by ensuring the shapeof
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`the envelope generated by the instrument in rotation. Thus the instrument in
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`accordancewith the third embodiment retains all the advantages describedin relation
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`10
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`to the first two embodiments while reducing the beating motion at the rear of the
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`instrument, a motion which could reduce the precision and speed of treatment of the
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`dental root canal.
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`The embodiments presented above describe polygonal cross-sections with straight
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`15
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`sides. It is clear that said sides could be curved. Consequently, the term "polygonal"
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`should be understoodin its general sense meaning "which hasa plurality of sides" and
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`covering equally a geometric shape with straight or curvedsides.
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`The instrument in accordancewith the invention could obviously have other known
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`20
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`features such as variable conicity. Similarly, the flutes can be oriented equally to the
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`right or left or even have a variable pitch.
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`In a general manner, the active part of an instrument in accordancewith the invention
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`has, over is whole length, a polygonal cross-section forming at least two cutting edges.
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`25
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`The active part is defined by an essentially conical or cylindrical envelope, the
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`longitudinal axis of which coincides with the axis of rotation of the instrument. The
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`active part comprisesa first portion extending from the point of the instrument and
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`which is such that any cross-section of this first portion has its centre of mass on the
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`axis of the envelope and definesat least two cutting edges whichareall located on
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`30
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`said envelope. The active part also comprises a secondportion extending following the
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`first portion towards the rear of the active part and whichis such that at least one cross-
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`11
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`Docket No. 5001-1489
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`section of this second portion has a centre of mass whichis not located on the axis of
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`the envelope but whichis offset with respect to this axis and defines cutting edges, of
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`which at least one is located on the envelope and at least one is located set back within
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`said envelope.
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`The instrument in accordancewith the invention thus has a point which is centred with
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`respectto the axis of rotation of the instrument and a rear part, of which at least one
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`cross-section is off-centre. The centred point makesit possible to follow the initial path
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`of the root canal, to avoid any beating motion within said canalin the vicinity of the
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`10
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`point and to ensure dimensioning in the preparation of the apical part of the canal.
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`Moreover, the centred point avoids debris descending towards said apical part of the
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`canal and contributes to successful evacuation thereof. This evacuation is further
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`facilitated by the fact that at least one cross-section of the rear part is off-centre: the
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`debris in fact has more spaceto be carried out of the canal and the off-centring of at
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`15
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`least one cross-section of the rear part of the instrument creates a dynamic effect
`
`which lifts the debris out of the canal.
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`Moreover, an instrument in accordance with the present invention makesit possible to
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`ensure strength in the part close to the point in order thus to reducethe risk of breaking
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`20
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`the instrumentin its most fragile portion. The flexibility of the instrumentis not thereby
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`reduced, since the second portion having at least one off-centre cross-section of the
`
`instrument makesthe instrumentflexible and this flexibility can even be progressive
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`towardsthe rear of the instrumenteither by adjusting the off-centring of the second
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`portion of the active part of the instrument as described in the caseof thefirst and
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`25
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`second embodiments or by alternating centred cross-section with off-centre cross-
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`section along the second portion of the active part of the instrument as described in the
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`third embodiment. Thus the instrument can be renderedsufficiently flexible to follow the
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`complex contour of a dental root canal.
`
`30
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`Finally, the active cutting edges of the point of the instrument, i.e. those which are
`
`located on the envelope, ensure a goodlevel of efficacy of the instrument. At the rear,
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`12
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`Docket No. 5001-1489
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`the contact zones of the instrument are reduced since some of the edgesare located
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`set back within the envelopeof the instrument, which makesit possible to reduce the
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`screwing effect and superfluous forces on the rear part of the instrument.
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`Thus a high-performanceinstrumentis produced having a good balance between
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`efficacy, flexibility and resistance to breaking and to the screwing effect.
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`13
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`Docket No. 5001-1489
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`Claims
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`Instrumentfor drilling dental root canals comprising a tapered rod (1) having over
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`at least a part of its length - the active part (1b) - a polygonal cross-section (4)
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`forming at least two cutting edges (5a, 5b; 52, 54), said active part (1b)
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`terminating by a point (3) and being defined by an envelope(7) of a cylindrical or
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`conical shape, the longitudinal axis of which coincides with the axis of rotation (R)
`
`of the instrument, charac