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CONTENTS
INTRODUCTION
“ The lack of proper equipment “ is a reason often given by the dentist who do not practice RCT and it well might be not only are special instrument imperative for endodontic therapy. But a special arrangement of these instrument is necessary.
Impractical, inefficient scuring around the office to gather collection of unsterile ill-adapted equipment completely discourages the practitioner from endodontic therapy. These problems may be solved by procuring the correct equipment and supplies; by packaging the hand equipment into sterilized towel kits, into canisters, or on prearranged trays; and finally, by storing the small endodontic instruments in an organized, compartmentalized instrument case.
Endodontic armamentatium
Although most instruments used in general dentition also can be used for endodontic therapy. In addition, many many different types of instrument have been designed for procedures performed inside pulp space.
Preparation for treatment begins with selection of the armamentarium for routine endodontic patient care.
Instruments used for every patient should be assembled and sterilized before use.
list below gives typical armamentarium that can be customized for the individual practitioner
IMS INSTRUMENT CASSET
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Endodontic instruments
Although most instruments used in general dentistry also can be used for endodontic therapy, some handinstruments are designed specifically for endodontic procedures. In addition, many different types of instruments have been designed for procedures performed inside the pulp space. These include manually operated instruments for root canal preparation, engine-driven and energized instruments for root canal preparation, instruments for root canal obturation, and rotary instruments for post space preparation. Standardized specifications have been established to improve instrument quality. For example, the International Standards Organization (ISO) has worked with the Fédération Dentaire Internationale (FDI) through the Technical Committee 106 Joint Working Group (TC-106 JWG-l) to define specifications. These standards are designated with an ISO number. The American Dental Association (ADA) also has been involved in this effort, as has the American National Standards Institute (ANSI); these standards are designated with an ANSI number. However, new instrument designs have resulted in a need for reconsideration of the standards.
Two ISO standards pertain to endodontic instruments. ISO no. 3630-1 deals with K-type files (as does ANSI no. 28), Hedström files (ANSI no. 58), and barbed broaches and rasps (ANSI no. 63). ISO no. 3630-3 deals with condensers, pluggers, and spreaders (ANSI no. 71).
II
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Endodontic engine driven instruments latch and shaft and operative head, all made of a single piece
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Gates glidden
Peeso reamer
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III
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Engine driven instruments
Handle has been replaced by a latch type adaptor for insertion in contra angle hand piece
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Similar to group I instruments
Niti Rotary instruments like Profile
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Hand Instruments
Traditional hand instruments sometimes are modified for endodontic uses. A typical set of endodontic instruments might include a mouth mirror, a D-5 explorer, a D-16 endodontic explorer, cotton pliers, a spoon excavator, a series of pluggers, a plastic instrument, a hemostat, a periodontal probe, and a ruler. The endodontic explorer has two straight, very sharp ends that are angled in two different directions from the long
axis of the instrument. Several types of endodontic spoons are available. These spoons have a much longer offset from the long axis of the instrument (for better reach inside constricted pulp chambers) than regular dental spoons. The spoons are used to remove carious material and to excise pulp tissue; therefore, they should be kept well sharpened
The exact type and number of instruments usually depend on the techniques used and clinician’s preference.
Instruments for Pulp Space Preparation
The purposes of this section are to provide and consolidate the principles the clinician needs both to understand the design of instruments and to choose and use current and future instruments to the greatest effect. Most instructional materials mistakenly attempt to teach step-by-step techniques rather than explain the physics of instruments. However, an increasing number of new products and their advocates has created confusion in the selection process, and products become obsolete before they can be thoroughly evaluated. For these reasons, the clinician must understand the scientific principles of instrumentation. The two primary goals of root canal instrumentation are (1) to provide a biologic environment (infection control) conducive to healing and (2) to develop a canal shape receptive to sealing. Historically most instruments used to shape the canal were designed to be used by hand. Although not universally used, rotary instrumentation has gained considerable interest and most often is used in combination with hand instruments. The information in the following sections should facilitate the most efficient use of rotary instruments, minimizing the chance of failure and allowing the clinician to achieve treatment ideals. An understanding of the physics of rotary technology can provide financial rewards, save time and, most important, enhance the quality of treatment while avoiding inherent risks. However, one point must be strongly emphasized: these improvements are not derived from quickness or ergonomics; rather, they are the result of increased control and of the ability both to anticipate the optimal approach and to eliminate the less-than optimal ,the unnecessary, and the sometimes counterproductive elements of a technique.
INSTRUMENTS FOR ACCESS OPENING
Round burs
• Small standard round bur
• 16 mm bur
– Shank 3mm longer than standard bur
– Long shank round bur (23 mm)
• Goose neck round bur
• Size 2, Size 4 and Size 6 are used to lift the roof of the pulp chamber
GOOSE NECK ROUND BUR
• Used to locate partially Sclerosed/Calcified canal.
• Has the advantage because of its extended narrow shank of not being deflected by the wall of the access cavity
TAPERED DIAMONDS
• Open and flare the orifice.
• Smoothen irregularities in access walls
Penetrators and Metal cutters
• Used for full non precious metal casting and non precious substructures of PFM crowns.
• Round end crosscut design that minimizes chatter
Beaver bur , Great white , Transmetal Bur, Brassler H34L
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Endo Access Bur
• Bur's tip matches round bur sizes for initial penetration
• Diamond shaft flares the pulp chamber.
• Cutting surface 10mm
• Total length is 21mm
Canal orifice flaring instruments
GATES-GLIDDEN BURS
• Side-cutting, safe ended instruments and used to cut dentine as it is withdrawn from the canal.
• Used serially, passively
• Used in 750 to 1000 rpm
• should be used as a brush to carve away restrictive dentin
• Available in 2 lengths :32mm length and 28mm length for posterior teeth
Gates glidden drills has 3 main uses:
1) Flaring of the coronal two thirds of the root canals
2) For removal of gutta –percha from a canal during post space preparation or during retreatment
3) To widen the canal for retrieval of broken instruments
• Most often used in preparing coronal portion of the root canal for receiving a post
• Similar to gates glidden but have parallel cutting sides
• Safe-ended
• Tip – Diameter: 0.7 – 1.7
• Used in a brushing motion
INSTRUMENTS USED IN CLEANING AND SHAPING THE PULP SPACE
BARBED BROACHES AND RASPS
Length of working portion 10mm
Uses –
Gross removal of vital pulp tissue from large canals
Method of use – Inserted in the canal and rotated to engage the tissue.
PRONE TO BREAKAGE -- NEVER FORCE IN CANAL
STANDARDISATION:
Ingle and Levine in 1958 recommended.describes 3 features
a) Diameter and width
b) Length of cutting blade
c) Taper
1958 - Ingle and Levine first proposed standardization of endodontic instruments and suggested guidelines for the same
1) The instruments shall be numbered from 10 to 100, the numbers to advance by 5 units to size 60, and thereby by 10 units to size 100.
2) The instrument number shall be representative of the diameter of the instrument tip in hundredth of a mm (1/100). Eg. No. 20 is 0.20 mm (20/100) at the tip.
3) The working blades (flutes) shall begin at the tip designated site D1 and shall exactly 16 mm up to shaft terminating at designated site D2.
4) The diameter of D2 shall 0.32 mm greater than that of D1. eg: File no.20 shall have a diameter of 0.20 mm at D1 and a diameter of 0.52 (0.20 + 0.32) mm at D2
5) This sizing will ensure a constant increase in taper of 0.02 per mm of every instrument regardless
Modifications from Ingles original proposal are
6) An additional diameter measurement point at D3, 3 mm of from tip of cutting end of instrument at D0
7) Tip angle of an instrument should be 75o ± 15o
COLOUR CODING:
• The International Standards Organisation (ISO) recommended a colour coding system for easier recognition
• consists of 6 colours chosen in ascending order of size from light to dark
• Small sized instruments (06, 08) were also added and colour coded as pink, grey .purple respectively.
Instrument length:
• Measured from the instrument tip to the end of the shank (l2)
• Manufactured in four lengths
Standard- 25 mm
Long - 28 mm and 30 mm(useful in canines)
Short - 21 mm
• the working end of the instrument (length of the cutting segment, l1) remains constant is 16 mm.
REAMERS
Action:
• cut by being tightly inserted into the canal, twisted clockwise one quarter to one half turn to engage their blades in dentin and then withdrawn –
• Penetration– Rotation-- Retraction.
REAMING
Watch Winding
• Clockwise/anticlockwise rotation of the instrument through an arc of 30-60 degree while advancing in the canal
K- File
- Produced by twisting a 4 sided
pyramidal blank
• Square cross-section
- The file has more flutes per length
unit than the reamer
- Used in push-pull filing motion.
• NON CUTTING TIP/SAFE ENDED OR BATT TIP :
• Helps to pivot the instruments down the canal so that it follows the canal shape.
• the tip will guide the instrument and this reduces apical transportation.
K File K Reamer
Files Reamer
· Square cross section triangular cross section
· Tighter flutes loose spirals
· Resists fracture better Cutting efficiency is 2.5 times
· Maintains keen edge sharpness is lost rapidly
· More number of flutes less number of flutes
· Filing and reaming motion reaming motion
FILING MOTION
– The instrument is placed into the canal at desired length
– pressure exerted against the canal wall
– while this pressure is maintained, the instrument is withdrawn without turning
K-FLEXLES F
Cross section: rhombus or diamond.
• Cutting edges: high flutes (Formed by 2 acute angle) presents increased sharpness and cutting efficiency
• Obtuse Angle provides Alternating low flutes - more area for increased debris remo
HEDSTROEM FILES
• Manufacture: cutting spiral flutes into the shaft of a piece of round tapered stainless steel wire.
• It cuts only in one direction, during retraction because of positive rake of the flute design
• Cross section :single helix or tear drop
Rotating the instrument with a tip of file engaged in dentin is a
common cause of fracture.
They are aggressive cutters.
It resembles ‘Christmas tree’. [cone over cone]
used to remove loose broken instrument.
Disadvantage:
Fracture tendency because of depression between flutes causing narrowness between core material.
Tip Design.
Studies have shown that tip design can affect file control, efficiency, and outcome in the shaping of root canal systems. The tip of the original K-file resembled a pyramid. The file can break if the clinician applies excessive torque while attempting to enlarge a canal with a smaller diameter than the noncutting portion of the file tip. Instrument tips have been described as cutting, noncutting, and partially cutting, although no clear distinction exists among the three typesThe instrument tip has two functions: to enlarge the canal and to guide the file through the canal. A clinician who is unfamiliar with the tip design of a particular instrument is apt to do either of the following: (1) transport the canal (if the tip is capable of enlarging the canal and remains too long in one position) or (2) encounter excessive torsion and break the file (if a noncutting tip is forced into a canal with a smaller diameter than the tip). Transportation of the original axis of the canal can occur by remaining too long in a curved canal with a tip that has efficient cutting ability. On the other hand, with the H-file the clinician need not remain too long in one position, and the instrument’s efficient cutting can facilitate enlargement or negotiation of constricted or blocked canals. The angle and radius of its leading edge and the proximity of the flute to its actual tip end determine the cutting ability of a file tip. Cutting ability and file rigidity determine the propensity to transport the canal. The clinician must keep in mind that as long as the file is engaged 360 degrees, canal transportation cannot occur. Only with overuse does the file begin to cut on one side, resulting in transportation. Most instrumentation occurs when the file tip is loose in the canal, which gives it a propensity to transport the canal.
Metal Alloys.
The development of nitinol, an equiatomic alloy composed of nickel and titanium, has proved a significant advancement in the manufacture of endodontic instruments. Nickel-titanium is called an exotic metal because it does not conform to the normal rules of metallurgy. Because it is a superelastic metal, the application of stress does not result in the usual proportional strain seen in other metals. When stress is initially applied to nickel-titanium, the result is proportional strain; however, the strain remains essentially the same as the application of additional stress reaches a specific level, forming what is called a loading plateau. Eventually, of course, application of more stress results in more strain, which increases until the file breaks. This unusual property is the result of a molecular crystalline phase transformation. External stresses transform the austenitic crystalline form of nickel-titanium into a martensitic crystalline structure that can accommodate greater stress without increasing the strain. As a result of its unique crystalline structure, a nickel-titanium file has shape memory, or the ability to return to its original shape after being deformed. Simply stated, nickeltitanium alloys currently are the only readily available, affordable materials with the flexibility and toughness for routine use as effective rotary endodontic files in curved canals. One study reported that stainless steel was more resistant to fracture than nickel-titanium when angular deflection (fracture by twisting) was measured. Attempts to improve the nickel-titanium alloy continue, and it has been shown that the surface characteristics can be greatly improved by treating instrument surfaces.
Electropolishing, surface coatings, and surface implantation have been used for this purpose
Rotary Instruments for Canal Preparation
Components of a File.
To make the best use of files, the clinician should know the parts of each file and understand how variations in design affect instrumentation. The taper usually is expressed as the amount the file
diameter increases each millimeter along its working surface from the tip toward the file handle. For example, a size #25 file with a #.02 taper would have a 0.27 mm diameter 1 mm from the tip, a 0.29 mm diameter 2 mm from the tip, and a 0.31 mm diameter 3 mm from the tip. Some manufacturers express the taper in terms of percentage (e.g., a #.02 taper is a 2% taper). Historically, as an ISO standard, a file was fluted and tapered at 2% for 16 mm, but now files incorporate a wide variation of lengths and tapers of working surfaces. The ability to determine cross-sectional diameter at a given point on a file can help the clinician determine the file size in the point of curvature and the relative stress being placed on the instrument.
The flute of the file is the groove in the working surface used to collect soft tissue and dentin chips removed Peeso reamer (Union Broach). Note the safety tip and guiding marginal lands on the machining surfaces. Rotary ProFile NiTi instruments, sizes #3, #5, and #6 (Tulsa Dental Products). The instruments have marginal lands that guide the instrument in the center of the canals and around curvatures. Components of an endodontic rotary instrument. from the wall of the canal. The effectiveness of the flute depends on its depth, width, configuration, and surface finish. The surface with the greatest diameter that follows the groove (where the flute and land intersect) as it rotates forms the leading (cutting) edge, or the blade of the file. The cutting edge forms and deflects chips from the wall of the canal and severs or snags soft tissue. Its effectiveness depends on its angle of incidence and sharpness. If a surface projects axially from the central axis as far as the cutting edge between flutes, this surface is called the land (or sometimes the marginal width). The land reduces the tendency of the file to screw into the canal, reduces transportation of the canal, reduces the propagation of microcracks on its circumference, supports the cutting edge, and limits the depth of cut. Its position relative to the opposing cutting edge and its width determine its effectiveness. To reduce frictional resistance, some of the surface area of the land that rotates against the canal wall may be reduced to form the relief. The angle the cutting edge forms with the long axis of the file, called the helix angle, augers debris collected in the flute from the canal. This angle is important for determining which file technique to use
a file is sectioned perpendicular to its long axis, the rake angle is the angle formed by the leading edge and the radius of the file. If the angle formed by the leading edge and the surface to be cut (its tangent) is obtuse, the rake angle is said to be positive or cutting. If the angle formed by the leading edge and the surface to be cut is acute, the rake angle is said to be negative or scraping . However, the rake angle may not be the same as the cutting angle. The cutting angle, or the effective rake angle, is a better indication of a file’s cutting ability and is determined by measuring the angle formed by the cutting (leading) edge and the radius when the file is sectioned perpendicular to the cutting edge. If the flutes of the file are symmetric, the rake angle and the cutting angle are essentially the same.
The pitch of the file is the distance between a point on the leading edge and the corresponding point on the adjacent leading edge; or, it may be the distance between corresponding points within which the pattern is not repeated. The smaller the pitch or the shorter the distance between corresponding points, the more spirals the file has and the greater the helix angle. Most files have a variable pitch, one that changes along the working surface. Because the diameter increases from the file tip toward the handle, the flute becomes proportionately deeper, resulting in a core taper that is different from the external taper. The cutting angles, helix angles, and external and core tapers may vary along the working surface of the file, and the ratios of these quantities can vary between instruments of the same series.
A change in any of these features can influence the file’s effectiveness or its propensity for breakage as it progresses into the canal space and can explain why some files act uncharacteristically compared with other files in the same series. In one study, investigators using electric and air-driven handpieces with rotary nickel-titanium instruments found no significant difference in file distortion or breakage between the two handpieces at 150 revolutions per minute (rpm).[38] Other researchers have shown that the ability to select precise rpm[68] and torque[95] settings affects the efficiency and durability of instruments. Determining a file’s rpm level is more difficult with an air handpiece than with an electric handpiece .
For this reason the clinician would be wise to use an electric handpiece when instrumenting with rotary files. The popularity of electric handpieces among clinicians appears to support the conclusion that regardless of the design used for rotary nickel-titanium instruments, an electric handpiece, rather than an air-driven handpiece, should be used because it allows precise speed control.
A high-torque, low-rpm electric handpiece.
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Instrument Designs
The following design components can be used to prevent excess stress on instruments. 1. The difference between the file’s minimum and maximum diameters can be reduced so that the
torque required for rotating the larger diameter does not exceed the plastic limit of the smaller
diameter.
2. The space between the tip and the maximum diameter can be reduced so that the required torque
does not exceed the ultimate strength of any part of the file.
3. A zero taper or nearly parallel and fluted working portion of the file can be provided for curved canals
so that the apical portion of the canal can be enlarged without undue file stress and compression of
debris.
4. The continuity of the blade engagement can be interrupted.
5. The number of flute spirals can be eliminated or reduced to the smallest number necessary to prevent
excessive torque, which results from the accumulation of debris.
6. A means can be provided to complete the file function before the flutes fill with debris.
7. Any land width can be minimized to reduce abrasion on the canal surface.
8. The file can be given an asymmetric cross section to help maintain the central axis of the canal.
9. The number of flutes with similar helix angles can be reduced. When helix angles are dissimilar,
screwing-in forces are reduced; when flutes have no helix angles, screwing-in forces are eliminated.
10. Positive cutting angles can be incorporated to enhance the efficiency of canal enlargement.
11. Blades can be made appendages or projections from the file shaft rather than ground into the shaft.
12. Channels can be cut along the long axis of the file to facilitate its removal if it breaks.
ProFile and ProFile GT.
ProFile rotary nickel-titanium instruments (Dentsply–Tulsa Dental, Tulsa, OK) are available in sizes with a #.02, #.04, #.06, or #.08 taper. These instruments are distinguished by their trihelical, symmetric
U-shaped flutes separated by lands. The blades have slightly negative
rake angles. The ProFile and ProFile GT have essentially the same cross-sectional configuration. The ProFile has a 16 mm working length; in contrast, the length of each taper of the ProFile GT varies as a result of
having the same tip sizes and maximum diameters. The ProFile GT has slightly more spirals at the tip portion of the instrument and slightly fewer at the handle portion. The ProFile GT series does not include #.02 tapers. As with most systems using a large taper, the instrument becomes rather stiff before the apical preparation has been sufficiently enlarged.[96][150] This puts limitations on the use of this instrument in narrow, curved root canals. ProFile GT instruments are divided into three primary size families (#20, #30, and #40) based on the tip size. Each series has four tapers (#.04, #.06, #.08, and #.10. The largest taper is also available in sizes #35, #50, and #70.
Rotary ProFile NiTi instruments
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LightSpeed.
The LightSpeed instrument (LightSpeed Technology, San Antonio, TX) has essentially the same crosssectional design as the ProFile and ProFile GT. However, it has a unique, short, flame-shaped working portion and a reduced-diameter shaft similar to that of a Gates-Glidden drill. The long, unspiraled shaft provides good flexibility around canal curves. The minimal working surface requires higher rotation speeds (1000 to 2000 rpm) compared with other files. The tip has a long, noncutting pilot portion . The LightSpeed instrument comes in sizes #020 to #140. It also includes “half” sizes (e.g., #022.5, #027.5) up to #060. In the smaller sizes the head is less well defined ( Fig. 8–43 ). The design has been shown to vary with the instrument size.[180] The manufacturer recently proposed that these instruments be used in a hybrid technique. Other instruments presented in this chapter would be used to shape the coronal segments of the root canal, and a limited number of LightSpeed instruments would be used to enlarge the apical segment. This suggestion is based on reports that larger-than-normal apical preparation sizes can be obtained with these instruments without compromising remaining dentin thickness in the more coronal segments of the canal.This capability takes on greater importance because increasing the size of the apical preparation has been shown to be directly related to the clinician’s ability to disinfect the critical segment of the infected canal. In one study, a combination of tapered rotary and LightSpeed instruments was used in 40 patients; the study showed that instrumentation to apical preparation sizes larger than those typically used (60 for molars and 80 for cuspids and premolars)more effectively removes culturable bacteria from
Sonic and Ultrasonic Instruments
A radically different way of instrumenting root canals was introduced when clinicians became able to activate files by electromagnetic ultrasonic energy.Piezoelectrical ultrasonic units are also available for this Scanning electron microscopic (SEM) image of the Hero 642. Note the positive rake and the similarity to a trihelix
Hedström file. purpose. These units activate an oscillating sinusoidal wave in the file with a frequency of about 30 kHz. Two types of units, ultrasonic and sonic, are primarily available. Ultrasonic devices, which operate at 25 to 30 kHz, include the magnetostrictive Cavi-Endo (Caulk/ Dentsply, Milford, DE), the piezoelectrical ENAC (Osada, Tokyo), and the EMS Piezon Master 400 (Electro Medical Systems [EMS] Vallée de Joux, Switzerland). Sonic devices, which operate at 2 to 3 kHz, include the Sonic Air MM 1500 (Micro Mega, Prodonta, Geneva, Switzerland, the Megasonic 1400 (Megasonic corp, House Springs, MO), and the Endostar (Syntex Dental Products, Valley Forge, PA) . Ultrasonic devices use regular types of instruments (e.g., K-files), whereas sonic devices use special instruments known as Rispi-Sonic, Shaper-Sonic, Trio- Sonic, or Heli-Sonic files. Although similar in function, piezoelectrical units have some advantages over the magnetostrictive systems. For example, piezoelectrical devices generate little heat; therefore, no cooling is needed for the electrical handpiece. The magnetostrictive system generates considerable heat, and a special cooling system is needed in addition to the irrigation system for the root canal. The piezoelectrical transducer transfers more energy to the file than does the magnetostrictive system, making it more powerful. The file in an ultrasonic device vibrates in a sinus wave–like fashion. A standing wave has areas with maximal displacement (i.e., antinodes) and areas with no displacement (i.e., nodes). The tip of the instrument exhibits an antinode. If powered too high, the instrument may break because of the intense vibration. Therefore files must be used only for a short time, and the power must be sent carefully. The frequency of breakage in files used for longer than 10 minutes may be as high as 10%, and the breakage normally occurs at the nodes of vibrations. Ultrasonic devices have proved very efficient for irrigating root canal systems. During free ultrasonic vibration in a fluid, two significant physical effects are observed: cavitation and acoustic streaming. During oscillation in a fluid, a positive pressure is followed by a negative pressure. If the fluid’s tensile strength is exceeded during this oscillation of pressure gradients, a cavity is formed in the fluid in the negative phase. During the next positive pressure phase, the cavity implodes with great force; this is cavitation. Under normal clinical conditions the power of dental ultrasonic units is too low to create significant cavitation effects on the dentin.
ENAC piezoelectrical ultrasonic device
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