ENDODONTIC
`THERAPY
`
`FRANKLIN S. WEINE, BS, DDS, MSD, FACD, FICD
`Professor Emeritus, Loyola University (Chicago);
`Formerly Professor and Director, Post-Graduate Endodontics,
`Loyola University School of Dentistry,
`Maywood, Illinois;
`Visiting Professor of Endodontics, Osaka Dental University,
`Osaka, Japan
`
`SIXTH EDITION
`
`Selected artwork by: Sandy Cello Lang and Don O'Connor
`Photography by: Oscar Izquierdo and Al Hayashi
`
`~..,.~Mosby
`
`An Affiliate of Elsevier
`
`GOLD STANDARD EXHIBIT 2033
`US ENDODONTICS v. GOLD STANDARD
`CASE PGR2015-00019
`
`

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`
`ENDODONTIC THERAPY
`Copyright© 2004, Mosby, Inc. All rights reserved.
`
`ISBN 0-323-01943-9
`
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`NOTICE
`
`Dentistry is an ever-changing field. Standard safety precautions must be followed, but as new research and
`clinical experience broaden our knowledge, changes in treatment and drug therapy may become
`necessary or appropriate. Readers are advised to check the most current product information provided by
`the manufacturer of each drug to be administered to verify the recommended dose, the method and
`duration of administration, and contraindications. It is the responsibility of the licensed prescriber,
`relying on experience and knowledge of the patient, to determine dosages and the best treatment for each
`individual patient. Neither the publisher nor the author assumes any liability for any injury and/or
`damage to persons or property arising from this publication.
`
`The Publisher
`
`Previous editions copyrighted 1996, 1989, 1982, 1976, 1972
`
`Library of Congress Cataloging-in-Publication Data
`Weine, Franklin S.
`Endodontic therapy/Franklin S. Weine.-6th ed.
`p. ; em.
`Includes bibliographical references and index.
`ISBN 0-323-01943-9
`1. Endodontics. I. Title.
`[DNLM: 1. Endodontics. WU 230 W423e2004]
`RK351.W44 2004
`617.6'342-dc22
`
`2003059284
`
`Publishing Director: Linda L. Duncan
`Executive Editor: Penny Rudolph
`Senior Developmental Editor: Kimberly Alvis
`Publishing Services Manager: Linda McKinley
`Designer: Gail Hudson
`
`Last digit is the print number: 9 8 7 6 5 4 3 2
`
`

`
`CHAPTER 5
`
`TREATMENT
`BASIC AND
`
`'
`
`CHAPTER OUTLINE
`Basic Intracanal Instruments
`Broaches
`Methods for using reamers and files
`Reamers
`Files
`Styles of instruments
`Standardization
`Rules for Canal Preparation
`Determination of Correct Width for Canal
`Preparation
`Minimal instrumentation at any appointment-to
`reach size 25
`Determination of apical width
`Gaining sufficient enlargement for using gutta(cid:173)
`percha-the flared preparation
`Canal enlargement in moderately wide and/or
`straight canals
`Canal enlargement in smaller, relatively straight,
`canals
`Importance of using MAF as final instrument after
`using flaring files short of the working length
`Overuse and abuse of flaring
`Final test for completion of canal preparation(cid:173)
`placement of the finger spreader
`Aids for Preparing Difficult Canals
`Problems encountered in canal preparation
`Precurving of files
`Incremental instrumentation
`New instruments with intermediate sizes
`Need for remeasurement when preparing curved
`canals
`Preparation in Extremely Curved Canals
`Determination of canal curvature
`Observations that canal shape changes
`Plastic block studies
`Standard preparation in the sharply curved canal
`Applications on extracted teeth
`Avoiding the apical zip and the elbow
`Application to clinical cases by using customized
`files
`
`164
`
`1
`
`1
`
`Theories for flaring in complex cases versus crown-
`down preparation
`Rules governing the use of non-ISO tapered
`instruments
`Effect of the non-ISO tapers on canal curvature and
`resultant changes in canal shape
`Typical cases
`New File Systems for Preparation of Curved Canals
`Effects of increased flexibility on final canal shape
`Flexible file systems
`Nickel-titanium files
`Minimizing zipping by flute removal and modificatiom
`of tips
`Disadvantages of flexible files
`Non-ISO taper file for penetration
`Preparation of Type II Canal Systems
`Complete Endodontic Treatment of Primary Teeth
`Ultrasonics
`History of ultrasonics in dentistry
`Method for action
`Techniques for use
`Canal preparation
`Related uses for ultrasonics
`Irrigants and Chelating Agents
`Functions of irrigants
`Useful irrigants
`Method of irrigation
`Recent studies concerning irrigants and their
`implications
`Function of chelating agents
`Intracanal Medicaments
`Function of intracanal medicaments
`Phenol and related volatile compounds
`. . rt,
`Calcium hydroxide as a medicament for "weepUW •
`cases
`Sealing Agents for Intertreatment Dressings
`Need for sealing agents
`Types of available sealing agents
`. . :
`Treatment of Operative Perforations
`General rules for treating operative perforauon5,
`
`~
`
`

`
`INTRACANAL TREATMENT PROCEDURES, BASIC AND ADVANCED TOPICS
`
`165
`
`of furcation perforations by packing the
`
`of perforations by enlargement and filling as
`~nLUUOv»••• canal
`
`Perforations treated surgically or orthodontically
`New materials for perforation repair
`Noninstrumentation Technology (NIT)
`
`major objective of the intracanal treatment pro(cid:173)
`. i5 to remove the contents of the canal and adja(cid:173)
`in such a way that the filling procedures that
`be facilitated. This means not only that the
`.o~o.:>:>uo::., necrotic debris, microorganisms, and affected
`must be removed from the treated tooth, but also
`canal walls must be prepared to receive a filling
`,..._ ____ _
`that will seal the apical foramen.
`this aspect of treatment lucidly, Schilder
`these procedures cleansing and shaping in
`of the need for debridement and development of
`receptacle for the filling material. I prefer the
`v-~<teEm canal preparation but certainly acknowledge that
`\G.!e!!!nsmg and shaping must be performed to reach the
`goal. Canal enlargement should not be used;
`' ,imeiely widening the diameter of the canal may not pro(cid:173)
`. .duc~e·•the correct shape that must be developed, neither
`
`= ~~,it always remove undesired contents from the canal.
`
`· •· illhe importance of canal preparation cannot be over(cid:173)
`~P,_hasized. It is these intracanal procedures that allow
`[Qr . ~e initiation of healing by removing the irritants to
`~n~pical tissue that have been harbored within the canal.
`\Wlien for some reason a longer than routine period of
`~e~has elapsed between the start and the completion of
`rther~py, it is not unusual to note radiographic evidence of
`llea~g of a periapical lesion on an x-ray film before canal
`fillidg (Figure 5-l).
`·~ ~liis chapter will discuss the instruments necessary to
`~,!!£afilplish the desired objective, the procedures designed
`. ta P-roduce results effectively and rapidly, and the adjuncts
`e.eded to retain the tooth in a desirable condition until
`ilic; canals are filled. The treatment of teeth with complex
`)?robletns will also be described.
`· th ~e calculation of working length is often included in
`e c:Uscussion of canal preparation, as it was in the first
`editions of this book. Because of its importance, this
`···.·, •.• c-,c,..L'-''-• now has a chapter of its own, Chapter 6. Working
`calculation may be an object of controversy, and I
`to give sufficient space to each of the several
`Popularity of several types of apex locators
`increased recently.
`~:~.e.t;calll<:P aspects of working length are necessarily
`in canal preparation, it is my hope that this
`does not become disorienting to the reader, who
`~~~gt!~::·z
`to working length while reading Chapter
`not yet read the basis for its calculation. Perhaps
`h
`5 ould be viewed as are some aspects of intricate spy
`
`. .,, .. ...... n
`
`A
`
`B
`
`FIGURE 5-l A, Preoperative radiograph of maxillary second
`bicuspid with large periapical radiolucency. Patient was a college
`student, home only for school vacations. Canal was debrided
`during Thanksgiving holiday with heavy irrigation of NaOCl,
`and second appointment was scheduled for Christmas recess.
`B, The tooth received no further treatment until five weeks later,
`when radiograph was taken for verification of fit for master cone,
`radiolucency had already healed without canal being filled. Poor
`fixing and scratches on this film have occurred because it is an
`intratreatment film developed ultrafast and generally is dis(cid:173)
`carded at the conclusion of the fill appointment. The signifi(cid:173)
`cance of this radiograph was not realized until later that day.
`
`novels, where characters and events are referred to but
`have not yet been introduced fully in the prose.
`
`BASIC INTRACANAL
`INSTRUMENTS
`The basic endodontic instruments used within the root
`canal are broaches, files (K-type and Hedstrom), and
`reamers. Although many engine-driven handpieces have
`been found to be of dubious value, particularly in the
`
`

`
`166
`
`ENDODONTIC THERAPY
`
`more difficult curved canals, recently the introduction of
`-some rotary instruments have been found to be very use(cid:173)
`fuL Because of their specific use for providing enlarge(cid:173)
`ment in the more coronal portion of the preparation, these
`systems will be reviewed a bit later in this chapter.
`
`Broaches
`Broaches are available in two types: smooth and barbed.
`The smooth broach had been used by some practitioners
`as an initial instrument to explore the patency and the
`walls of the canal. Most practitioners no longer follow this
`procedure, preferring to remove tissue bulk before the
`placement of any instrument near the apex to avoid
`forcing any inflamed or necrotic tissue through the apex.
`Therefore smooth broaches now are rarely used.
`The barbed broach has been used for many years in
`endodontics and was originally used in canal preparation.
`However, because of its ease of breakage, it is confined to
`rl,!moval of soft tissue only. It is a tapered instrument of
`soft steel that is notched by a shredder to produce sharp
`barbs extending outward from the shaft (Figure 5-2).
`This design is responsible for the frequency of breakage
`because the notching weakens the shaft by providing a
`place for fracture if stress or torque is applied. In addition,
`misuse within the canal may lead to disastrous results. If
`the operator attempts to force apically a barbed broach
`within a tightly fitting canal, the barbs will be bent toward
`the shaft, allowing for deeper insertion. However, when
`the instrument is withdrawn, the barbs will extend and
`engage the adjacent dentin. As more force is exerted in
`removal, the barbs will dig deeper, and further fatigue may
`result in snapping of the instruments. Therefore, once the
`hard surface of the dentin walls is felt, the barbed
`broach must not be inserted any farther.
`Correct use of the instrument involves its careful
`insertion through the access cavity until the dentin walls
`are felt or the approximate length of the canal is reached.
`The broach is slightly withdrawn, then rotated a few
`revolutions, and removed. Vital or necrotic pulp tissue
`and debris become ensnared on the barbs and removed so
`that much of the bulky content of the canal is debrided
`before files are placed toward the apical foramen. The
`barbed broach is similarly used to remove the paper points
`or cotton pellets of intertreatment dressings, which may
`defy removal by ex_cavator or explorer.
`
`FIGURE 5-2 Broach has small barbs protruding from shaft
`notched by a shredder, highly susceptible to breakage when
`locked in canal.
`
`The smallest-sized broach available has approximately
`the width of a size 20 instrument. Because broaches
`should not be used until the canal is wide enough for
`comfortable accommodation, they are not used initially in
`narrow buccal canals of maxillary molars and mesial.
`canals of mandibular molars. Once these canals have been(cid:173)
`enlarged to size 20 or larger, broaches should be used to
`remove the bulky tissue that has been packed into the (cid:173)
`apical portion of the preparation.
`
`Methods for Using Reamers and Files
`Some confusion exists as to the actions for using enlarging
`instruments and the instruments themselves. Botn
`reamers and files may be·used with either a reaming or a
`filing motion.
`
`Reaming. Reaming involves placement of the instru.: ·
`ment toward the apex until some binding is felt and then·
`turning the handle more than a full revolution. Clockwise
`turning will remove material from the canal by way of the
`flutes' revolution, whereas counterclockwise turning wilL
`force material apically. The major effectiveness of hard
`tissue removal by reaming is in the insertion of the
`instrument by shaving the dentin walls.
`
`Filing. Filing involves placement of the instrument
`toward the apex until some binding is felt and then
`removing the instrument by scraping against a side of the
`dentin wall with little or no revolution of the handle. Thlt
`dragging against the side of the wall is also referred to as
`rasping action. The major effectiveness of hard tissue
`removal by filing is in the outstroke or withdrawal of the
`instrument by dragging the flutes on the dentin walls.
`Considerable difference exists between using
`action and pistoning the canaL Pistoning involves
`up and down forcefully. This push/pull motion tends
`pack dentinal filings at the apex and alter canal shape
`small, curved canals to create ledges and short fills.
`involves a passive placement of the instrument to
`working length and a heavier drag motion against
`canal walL
`
`Circumferential Filing. Circumferential filing is
`method of filing whereby the instrument is moved
`toward the buccal (or the labial) side of the canal,
`reinserted and removed slightly mesially. This
`around the preparation to the lingual aspect and
`the distal until all the dentin walls have received
`(Figure 5-3). This technique enhances preparation
`flaring method is used by widening the orifice of the
`considerably, whereas the apical portion is kept
`small.
`Most roots are oval in cross section and are
`buccolingually than mesiodistally (the sole
`.
`being the palatal root of the maxillary molar) . If
`root contains only one canal, which many but not
`
`

`
`rm
`I I
`
`I
`
`INTRACANAL TREATMENT PROCEDURES, BASIC AND ADVANCED TOPICS
`
`167
`
`is irregular, usually increasing any eccentricities in the
`original canal shape.
`
`Reamers
`Reamers were the original intracanal instruments, used
`since the nineteenth century for removal of the contents
`of the pulp canal and for widening and smoothing the
`canal walls. They are manufactured by twisting triangular
`blanks (Figure 5-4, A) to produce cutting edges (Figure
`5-5, A). Because each angle of the blank is approximately
`60 degrees, a sharp knifelike edge is available to shave and
`reduce canal walls. The cross-sectional area of the blank is
`not excessively wide, so the instrument has a high degree
`of flexibility.
`
`A
`
`B
`
`c
`
`FIGURE 5-4 Shapes of blanks for basic instmment
`systems, which are twisted to give a different type of
`instrument. A, Triangular blank, as classically used for the
`reamer but now used in some files, has three angles of 60° each
`to provide cutting efficiency and a moderate cross-sectional
`diameter for flexibility. B, Square blank, as classically used for
`the file, has four angles of goo each, not as sharp as those of the
`triangular blank, with a wide cross-sectional diameter that
`decreases flexibility. C, Diamond blank, as used for the K-Flex
`file, has opposite angles equal. Angle a is less than goo, sharper
`than those of the square blank, but these are the only two cutting
`angles. The cross-sectional diameter is narrower than the square
`blanks of the same size, so this instrument has greater flexibility.
`Angle a plus angle b always equals 180°.
`
`' j'i'GW 5-3 Many roots are oval in cross section, and yet may
`~e:a single oval canal. If the dentist attempts to prepare such a
`2anat.with reaming action (top left), the result will be a canal
`mth··a keyhole shape (bottom left). This canal is overprepared in
`lOnt;>segment (the upper pole) and hardly prepared through the
`· der of the canal-an undesirable situation. However,
`erential filing (top right) involves placement of the file
`dragging it out against peripheral walls, emphasizing
`-~~~¢.o~~~al directions. The result (bottom right) is a wider oval
`enlarged in all dimensions and may be filled with
`materials. This method also enhances making the
`as wide as possible without gutting the crown.
`lffil~;Irulerential filing
`is modified
`in some canals by
`filing (see Figure 5-14, E).
`
`wider buccolingually as well. In these cases the
`filing is emphasized in the buccolingual
`ml1nt .. ·M-
`The oval canal is made into a wider and larger
`This permits easier placement of precurved
`gutta-percha cones, and finger spreaders.
`~Cllltnter,ent:ial filing is modified by anticurvature
`Figure 5-14, E) when flaring the mesial canals
`........... rv and mandibular molars and some other
`canals. This alteration will be addressed later in
`fi~~:~~ll>tl~r in response to avoiding strip perforations.
`have shown that the action of using the
`rather than the instrument used, determines
`_
`general. shape of the canal preparation. Therefore
`Thctlon produces a canal that is relatively round in
`e use of filing action develops a preparation that
`
`

`
`168
`
`ENDODONTIC THERAPY
`
`A
`
`B
`
`c
`
`fiGURE 5-5 A, Instruments are manufactured in different
`lengths as well as widths. From top, File, 21 mm; reamer, 21 mm;
`two files, 25 and 31 mm; and reamer, 31 mm. B, Different types
`of handles are available. From top, Short plastic handle,
`measurement control (or test) handle, long metal handle (very
`rarely used now). C, Measurement control handle (top) is
`adjustable to allow for varying canal working lengths. Assembly
`consists of a file shaft (middle) placed in a handle and bolt
`(bottom) . D, Once correct working length is set, bulky handle
`prevents overinstrumentation of apex by being physically
`stopped by incisal-edge of tooth.
`
`Reamers are used during canal preparation to shave
`dentin. When used with a rasping action, they are less
`efficient- than a file. They remove intracanal debris with
`clockwise reaming action and are used in this manner to
`remove old gutta-percha canal fillings that have been
`softened with chloroform or xylene. By turning reamers
`counterclockwise, the dentist can place materials such as
`root canal sealer and creamy medicaments in the apical
`portion of the canal.
`
`Files
`Files are useful instruments in endodontics for the
`removal of hard tissue during canal enlargement.
`Whereas the reamer was the original endodontic in- -
`strument, the file was developed by changing some of the
`principles of design in an effort to make a more efficient
`instrument, one that would remove tooth structure faster.
`A square blank (see Figure 5-4, B) was substituted for the
`triangular blank and was twisted more to give greater (cid:173)
`numbers of cutting edges (see Figure 5-5, B). Because the
`Kerr Manufacturing Company was the first to adopt this(cid:173)
`method, these files were called K-type for many years. The
`square blank had angles of 90 degrees, which did not cut (cid:173)
`as well as the 60-degree angle of the reamer. However
`reamers had a half to one flute per millimeter, wher~
`files were given one and a half to two and a half flutes per
`millimeter (see Figure 5-5, A) and thus had many more
`cutting edges. The cross-sectional area of the file (from
`angle to opposite angle in the blank) was greater than that!
`of the reamer, making it less susceptible to breakage,
`which was considered a very valuable property in the day/
`of the weaker carbon steel instruments. However, the
`tighter wind of the file and its greater cross-sectional
`diameter decreased its flexibility.
`The action of the file is to scrape the flutes against the
`canal walls to gouge a portion of the dentin and pull it
`from the canal. This action requires periodic cleaning of
`the instrument by the operator so the dentin shavings do
`not clog the flutes.
`Files are efficient removers of tooth structure in any
`one of three techniques because of the multiplicity of
`cutting edges. They may be used with rasping or pure
`filing action only, in which they are placed in the apicil
`portion of the canal carefully and dragged against one will
`of the canal during removal. They may be used wi~
`quarter-tum filing, in which the instrument is carefull:w
`placed, rotated 90 degrees, and dragged out at the sam~
`time. They also may be used with pure reaming action and
`turned as they enter the canal.
`Files alone may be adequately used in canal prepara(cid:173)
`tion. Some techniques suggest the use of reamers first
`then files of the same size before going to the next grea~ef.
`width. The rationale for such a method is that the
`used clockwise removes debris remaining within the
`and that, because reamers may be slightly smaller
`files, enlargement is facilitated. I have not found
`necessary. Heavy and frequent canal irrigation
`-···~,-nv,_-
`aspiration of excess lavage fluid will satisfactorily
`canal debris and dentin filings. Also, some coxnpiHJJl~
`manufacture reamers larger than files, or this clifteri~J!1ij
`may occur because of inaccu~ate quality
`instrument width.
`Virtually no innovations in instrument design
`since Kerr began making files early in the 1900s.
`suddenly; in a year's time, several startling
`occurred in instrument manufacturing that .,.Pmeu""'"-r-
`
`

`
`INTRACANAL TREATMENT PROCEDURES, BASIC AND ADVANCED TOPICS
`
`169
`
`1 the choices available. This is an extremely
`situation and verifies the important position
`.tildlon1uc~ has gained with the general public and
`community.
`
`for Flexible Fiies. From the start of this cen-
`the 1970s, molar teeth and teeth with sharply
`were rarely treated. When they were, a high
`of failures resulted. In fact, Grossman wrote in
`as late as 1967 that teeth with canal curva-
`i!it~ll:w'uu•"'
`45 degrees and greater could not be treated
`without surgery. Although this was not
`that time, the reason was that most endodontic
`llfitl;'S,;_used then were rather inflexible.
`ijfJ.;_1n11ertucme.a in the discussion of files, increasing
`;~se:cuomu diameter decreases instrument flexibility.
`the triangular blank, used for the reamer (see
`5-4, A), has a narrower cross-sectional diameter
`~Wlllll,u1.:; square blank, used for the file (see Figure 5-4, B),
`has greater flexibility than the file in similar
`However, files became the dominant instrument
`preparation, and as such, a total decrease in
`of intracanal instruments resulted. Smaller
`such as sizes 10, 15, and 20, have narrow diameters
`5-1) and thus have sufficient flexibility to retain
`shape. However, in larger sizes, such as 30, 35, and
`the files lose their flexibility very quickly, and
`of canal shape may be devastating (see
`5-23).
`
`Standardized
`Instruments
`
`Diameter (mm) at
`D0 (original D1)
`D16 (original D,)
`
`.04D16
`
`0.08
`0.10
`0.15
`0.20
`0.25
`0.30
`0.35
`0.40
`0.45
`0.50
`0.55
`0.60
`0.70
`0.80
`0.90
`1.00
`1.10
`1.20
`1.30
`1.40
`
`0.40
`0.42
`0.47
`0.52
`0.57
`0.62
`0.67
`0.72
`0.77
`0.82
`0.87
`0.92
`1.02
`1.12
`1.22
`1.32
`1.42
`1.52
`1.62
`1.72
`
`NA
`0.74
`0.79
`0.84
`0.89
`0.94
`0.99
`1.04
`1.09
`1.14
`1.19
`1.24
`1.34
`1.44
`1.54
`1.64
`NA
`NA
`NA
`NA
`
`To maintain shape in these curved systems, operators
`decided to keep canal preparation minimal, which may
`not have allowed for sufficient cleaning. Also, it was
`difficult to use a good condensation system to fill these
`minimally enlarged canals, so failures from inadequate
`filling were common. The result was that as an im:reased
`demand for treatment of these more complicated teeth
`occurred, it was necessary to develop new file systems.
`In its first design change in more than 60 years, the
`Kerr Manufacturing Company modified its basic blank to
`develop the K-Flex file (see Figure 5-4, C) . Rather than
`using a square or triangular blank, a diamond-shape blank
`was employed (see Figure 5-4, C) to decrease the cross(cid:173)
`sectional diameter (the distance between the two bs in
`Figure 5-4, C) and impart greater flexibility t~ the instru(cid:173)
`ment. Because of this shape, only two angles of the K-Flex
`would cut into the dentin (angles a in Figure 5-4, C) .
`However, because these working angles were approxi(cid:173)
`mately 80 degrees, sharper than the 90-degree angles of
`the file, their cutting ability was compensated somewhat,
`even though only two angles were present. Once the blank
`was twisted, there was an increased space between the
`working edges so more debris could be removed per
`outstroke.
`The implication of instrument flexibility and other
`designs for flexible file systems will be discussed later in
`this chapter, dealing with preparation of curved canals.
`Because of the improvement in final canal shape provided
`by flexible files, many other manufacturers developed
`their own file systems with these properties.
`
`Hedstrom Files. Hedstrom files have flutes that
`resemble successively smaller triangles set one on another
`(Figure 5-6) . They are manufactured by means of a sharp,
`rotating cutter that gouges triangular segments out of a
`round blank shaft in the same manner that wood screws
`are made. This produces a sharp edge that will cut on the
`removing stroke only. This process differs from that used
`for the standard reamers and files, which are made by
`twisting blades of triangular, square, or other shaped
`blanks. Several new designs have also been made by
`gouging, including the U-file and the Triocut.
`The Hedstrom file, also called the H-file, has two serious
`drawbacks. It is weakened at each position of gouging
`during manufacture, resulting in a place for fracture if the
`flutes bind in dentin and the handle is rotated. Also, if it
`is handled incorrectly and rotated clockwise after binding
`in dentin, its screwlike configuration may further drive
`the instrument apically and crack the weakened and
`stressed root.
`However, the Hedstrom file is an extremely effective
`cutting instrument because of the sharpness of the flutes.
`If used carefully, with filing action only, it will successfully
`plane the dentin walls much faster than the K-type of files
`or reamers. The Hedstrom files are especially indicated in
`the instrumentation of immature teeth, where the walls
`
`

`
`170
`
`ENDODONTIC THERAPY
`
`Cross section of
`double Hedstrom
`
`longitudinal
`configuration
`
`c
`
`A
`
`B
`
`0
`
`FIGURE 5-6 Types of ffie systems that are ground, not made from twisted blanks. A, Top, Hedstrom file (also called the
`and, bottom, double Hedstrom design, originally called "Burns Uni-File," now called 5-File because of cross-sectional
`B, indicating two rake angles for increased cutting ability. Wide cross-sectional diameter results in decreased flexibility for the
`compared with the Hedstrom. C, Longitudinal configuration of the 5-File demonstrates the design that allows it to cut deeply
`outstroke, minimizing packing of dentin into the apical portion of the preparation. D, Cross section of file referred to as U-file,
`of the three U-shaped cuts ground from a circular blank. This shape is used in the .04 tapered instruments lllll:nulacltun:~.
`DentsplyffulSa Dental (see Figure 5-12, A) and Dentsply/Maillefer (see Figure 5-12, B). E, Cross section of file type used in some
`Quantec series now manufactured by Sybron/Kerr. F, Cross section of K-3 file, also manufactured by Sybron!Kerr. This is a
`from most other ground blanks in that the segments of the instrument are asymmetrical. Because of the relatively large rTn,ss-:st:'-'"~
`diameter, this instrument probably is more resistant to fracture but is much less flexible than the other instruments shown.
`
`

`
`I I
`
`I I
`
`INTRACANAL TREATMENT PROCEDURES, BASIC AND ADVANCED TOPICS
`
`171
`
`and may harbor considerable debris. These
`i!te•lrUl"'' are also useful in removing silver points or
`ohTI"lKt:.u instruments from canals. The file is placed
`the material to be removed, then rotated, and
`~~"--·n•·" the occh,1sal (or incisal) surface. If sue(cid:173)
`file flutes will hook into the point or broken
`break any retention within the canal, and
`When the file is used to remove silver points,
`:::~4n~,r;n,n with chloroform to dissolve the root canal
`,,.,.r,, .. .., ... "- precede an attempt at dislodgement.
`and the other gouged instruments are
`aggressive cutters. As such, they are potentially
`lii~lidc:>us in the medium sizes of the apical portion of
`canals. For the same reason, however, they are
`in widening straight canals or the straight, more
`portion of curved canals. These files are well
`for performing preflaring or early flaring proce(cid:173)
`widening the orifices of any canals for easier
`imllll!•:'¢nllerlt of smaller instruments.
`~ " ~itional Gouged Instruments Recently Devel-
`, gppL Because of the sharpness and the speed afforded by
`~~,Hedstrom file, other gouged blank instruments have
`been introduced in the past 10 years. The U-file is a radial(cid:173)
`~ded instrument with three grooves in a "U" shape, cut
`o~t oJ the blank. The edge where the groove is cut and the
`cin:umference of the file is quite sharp and cu"ts dentin in
`eiUler.direction when the file is rotated (see Figure 5-6, D).
`3If~ shape is used in the .04 and greater tapered instru(cid:173)
`!Bents manufactured by Dentsplyffulsa Dental and
`J?..fnstply/Maillefer (see Table 5-4) and will be discussed
`late~ ip this chapter.
`, :ijle Quantec file system was also created by gouging
`l:!lanlts, but for some of these instruments only two wider
`were cut and raised edges produce sharp cutting
`(see Figure 5-6, E). A very recent entry into this field
`been the K-3 file system that has three radial-landed
`areas, each of a different, or asymmetrical, shape
`5-6, F). This instrument has a wider cross
`"ia"-'"'""v.ll<:U diameter than any of the other ground instru(cid:173)
`so it probably is more resistant to fracture.
`'1<\0·we-vPr this same increase in diameter means that it also
`~exible. Although the asymmetrical shape makes
`mteresting design, it is difficult to see its value
`in a rotating handpiece that delivers the flutes
`around the periphery of its cutting with each
`turn.
`
`of Instruments
`reamers come in different lengths and widths
`. various types of handles (see Figure 5-5). The
`Instruments are excellent for use in posterior
`extremely long teeth, particularly maxillary
`require those with the longest shaft.
`:measurement control handle (or test handle) may
`to be bulky and uncomfortable to use but is
`
`extremely useful for the dentist who confines endodontic
`efforts to single-rooted teeth. The length of instrument is
`governed by the handle, which physically stops the tip
`from penetrating too far past the cusp or incisal edge (see
`Figure 5-5, C and D). Once the working length of the
`tooth is correctly established, the files may be· set and
`instrumentation carried out without fear of unintentional
`overinstrumentation due to misrearung of the stop.
`For many years it was common practice for any dentist,
`even a specialist, to use one type of endodontic file
`system. Whatever type or condition of canal was encoun(cid:173)
`tered, that one system had to do the job. Recent studies
`have indicated that if a large variety of teeth are to be
`treated, several types of file systems will be necessary,
`perhaps even including both hand and mechanical
`instruments. The more flexible files are best used in
`curved canals but take too long for work in wider, straight
`canals. Aggressive files or mechanical instruments are well
`suited for flaring but are dangerous at the tips of curved
`canals.
`
`Standardization
`One of the most significant advances in endodontics has
`been the installation of a standardized system for intra(cid:173)
`canal instruments. As originally suggested by Ingle, this
`logical but long-overlooked development has been one of
`the greatest aids in bringing endodontic procedures
`within the scope and ability of the average den