Use and description of endodontic instruments

Transcription

1 Use and description of endodontic instruments Today s lecture is on the endodontic tools that we re going to use in the root canal therapy. As we already know all of the steps of root canal therapy beginning in the examination and diagnosis and ending with the obturation. This examination occurs with aid of the set of endo instruments. 1. Instruments used for access cavity preparation: **Basic instrument pack: 1.Front surface mirror; this one makes images more clearer than any other type of dental mirrors. 2.Endodontic locking tweezer 3.DG16 endodontic explorer (this one differs from that used in the cons) 4.Briault probe 5.Long shank excavator (long shank for the access cavity as to make it reach the full length of the canal/ in cons it s a short-shank) and is used for removing deep caries that have reached the pulp and caused the necrosis, plus removing that dead pulpal tissue as well. 6.Surgical hemostat 7.Millimeter ruler 8.Amalgam plugger 9.Flat plastic 1

2 2. Burs used in the access cavity: -High speed burs for perforation of pulp chamber by entering the enamel and dentine / first stage -Low speed burs: for the unroofing of the pulp chamber because these are less traumatic on the pulp chamber floor that we want to keep it intact and safe, and especially as not to perforate the furcation area in the molars because the high speed burs cut in a quicker way. If we damage the floor we change its anatomical structure which contains the grooves that are important in locating the orifices. *Low speed burs are divided into Normal and Extra-long. -Safe-ended burs -Gates-Glidden burs *recall the 3 main objectives of access cavity; and one of these in the complete unroofing. Because, if we don t completely unroof the chamber discoloration of the teeth (especially anterior teeth) will occur because of the pulpal tissue that will remain uncleaned then. And this isn t preferable at all especially with the anteriors for esthetical reasons. *note that when we become experts in this with training we ll only be using one type of burs all steps of access cavity could be done in high speed. *types of burs differ according to the tooth position and type; for example anterior teeth need round and straight fissure, and molars need the Endo-Z because their canals extend more. * Endo-Z: has a long cutting segment and this is beneficial for avoiding the undercuts, And making the walls in the molars Divergent toward the occlusal surface. A: B: C: D: 3. Gates-Glidden: (low speed burs) Used for: 1.Preparation/expansion of the coronal two-thirds of molar canals 2.Removing gutta percha from a canal 3.Retrieval of broken instrument *gates-glidden have several sizes; we differentiate the sizes by the number of (stripes) \\\ on its shaft. (black arrows) (sizes from 1 to 6 in an order of increasing in the size of the tip and strength of cutting but decreasing in fragility) \ = size of tip diameter 50; 0.5 mm, 2

3 \\ = 70; 0.7 mm \\\ = 90; 0.9 mm \\\\ = 110, 1 mm Please refer to slide 43 and this slide is to be memorized. *gates-glidden are very fragile especially size one; they could easily get broken if not well handled. However, this isn t a big deal because if it got broken this will happen at the point of the red arrow(which is the weakest point) so a considerable part will still be showing out of the cavity; and thus we will be able to easily pull it out without causing any problems to the patient himself. * used for the straight part of the canal (the coronal) because it is not flexible and doesn t follow the curvature of the canal (very good in removing the dentinal shoulder after the drop in ) *we usually use sizes number 2,3, and 4. Because 1 has a small tip and is so fragile and 5&6 somehow have a large tip-head and this will cause an aggressive cutting, which we want to avoid (especially in molars) for several reasons; conserving the tooth structure, controlling the removal of dentine as not to exceed or be less than a certain limit. *The smaller the size the deeper you can go inside of the canal: Size 2 can go 6 mm below the orifice Size 3 can go 4 mm below the level of the orifice Size 4 can go only 2 mm below the level of the orifice. And that has an advantage for sure which is the avoidance of excessive cutting. *they don t depend on the tooth but only on the size of the canal. * they may be very aggressive especially type 6; because we always need to control the canal as not to hurt the tooth structure and this isn t achieved by using the G-G especially type 6. 3

4 4. Endo-Z bur: (carbide) Cutting segment is tall = 9 mm. this and the shoulder bur have tall segments that taper toward the occlusal surface. It has a non-cutting tip. Uses and advantages: - makes a certain shape; the walls straight (for the straight line access) and divergent toward the occlusal surface for more visibility of the orifices. No undercuts as well. (this compared to the cavity prep of the cons; the walls need to be convergent toward the occlusal surface for more retention of the filling material; however, in the endo treatment if the cavity walls were convergent toward the occlusal surface there will be no retention and resistance form, any pressure or occlusal force on the filling with a wider base will cause dislodgement of the filling and that s why we need the surface to be wider more fixation, more visibility, more resistance form, good seal between the visit, no coronal leakage, and infection control preventing microorganism from escaping those visits to the pulp canals) 5. rubber-dam: we use the rubber dam - although many dentist skip it- for several reasons including the fact that the filling materials (even the ones of the cons) are sensitive for salivary contamination; this changes the bond strength of the composite for example causing its dislodgment in many cases. Uses: - most importantly and generally isolation and control of infection. - Protects the patient from inhalation or ingestion of instruments, medicaments and debris. - Provides a clean, dry field of operation free of salivary contamination; because we want no microorganisms to reach the root canal even though if we diagnose an already occurring pulp necrosis or apical periodontitis (an already infected root canal) because we want no other types of microorganism to enter or more infection to occur. - Prevents the tongue, lips, and cheeks from obstructing the operating field; especially when working on a lower 7 or 8 or when working with a patient who has an enlarged tongue or muscular cheeks because these will make your difficult without the rubber-dam. - Prevents the patient from rinsing the mouth and interfering with efficiency of treatment. - Time, money, and effort saving; some dentists think that it will cost them time at the beginning when applying the rubber dam unaware that it is absolutely an easy-to-use instrument that provides a clean filed, good vision, and a time saving overall mechanism on the long-term. *note: in root canal treatment the rubber-dam isolation is a must; there is a no case ever that using the rubber-dam isn t a must!! * what if the tooth is almost completely damaged and broken or very restricted that we cant use the rubber-dam isolation upon it? You have to try every way possible and an effort that would help you 4

5 use the rubber dam options or ideas: 1. Surgical lengthening for the crown if broken to make it hold the clamp, 2. Building-up the tooth, 3. Use the aid of the adjacent teeth if the tooth is restorative (multiple rubber-dam isolation; the photo in slide 7). Note that multiple isolation is also used when working on a group on teeth at once (anteriors for example in bleaching), but we usually do a single isolation for each single tooth. Now if all of these ideas didn t work then this means that the tooth isn t restorative at all and should be extracted (then implant it instead) but never think of not using the rubber-dam in that case. *medico-legal aspect: the instruments we use are very fine that there is always a chance of slipping and falling off our hands into the patient s mouth; and then if this happens it either enters the respiratory system or the digestive system. The case of the respiratory system is more critical and dangerous because this may cause suffocation or the need for surgery to get it out. This aspect is so important especially in those places where you are under strict legal observation. - Rubber-dam pieces: 1. Rubber-sheet 2. Puncher that makes a hole in the rubber-sheet 3. Clamps for fixation and proper isolation. 4. Frame: used outside the mouth/ Either metal or plastic and both are autoclavable (however the plastic is more used because in radiographs it doesn t appear but the metal appears radioopaque in radiographs and this may interfere with real teeth) This means that we even take x-rays and radiographs with the rubber dam applied. 5

6 5. Forceps: has 2 peaks that each of them fit into the 2 holes of the clamp. Used in fixing the clamp. single-tooth isolation Clamps : They differ according to the tooth; #1 is used for the premolars, 14 for a small molar, 14a for a bigger molar. 13a/12a for molars 2 types: winged and wingless. Winged is more used because these wings are used for fixing the sheet under the wing and this gives us a better isolation preventing salivary leakage. Butterfly clamp: Note: another type (doesn t appear in this picture) is #9 and called butterfly; used for anterior teeth. It has arms on both side Instruments for root canal preparation: Used for shaping of the canal. *chemomechanical deprivement (shaping and cleaning), this shaping method eases the way down the canal for the irrigants that s why we usually say shaping and cleaning rather than cleaning and shaping because shaping comes first for that reason. *we shape the canal in order to: 1. Widen it and that in return makes it easier for us to do the obturation and filling because canals sometimes could be very fine and thin for the filling to fit inside. 2. allows the irrigant to penetrate deep inside the canal * note that shaping is under the level of the orifices (now that we re totally done of the access cavity to the last step of unroofing) 6

7 *shaping instruments: Shaping has a variety of instruments; Hand-operated instruments. (these that we re going to use and concentrate on in our upcoming 4 th and 5 th years) Engine-driven instruments. Ultrasonic and sonic instruments *all that we need to know on instruments is : their cross-section, cutting edges, manufacturing material, design, shape, and everything that contributes to their efficacy. *it is important to know about each instrument s characteristics and how to deal with it as to beware not to break it down inside of the patient s mouth or root canal. Hand-operated instruments: A large number of root canal instruments available are manufactured from different alloys, cross sectional shape and diameters. Different alloys X Physical properties 1. Carbon steel: is old history now because it is too Brittle to be used anymore. 2. Stainless steel: is better because it is more resilient benefit of this: most of the canals are curved and if it may be straight it is definitely curved at its apical third so let s assume that all canals are curved. 3. Flexible stainless steel: more flexible than the normal stainless steel follows the curvature of the canal. 4. Titanium: more flexible 5. Nickel-titanium: most flexible/ most used nowadays/ last released/ used on the engine-driven instruments/ the best as rotary instruments engine-driven but bad as hand instruments; because of their high flexibility cant do precarving using them (precarving is preparing their shapes according to the expected shape of the canal), unlike the manual flexible stainless steel files on the contrary are more controllable inside the canal. Cross-section of the instrument affects its efficacy and flexibility during working. Cross section X Physical properties: Square: most rigid Triangular: more flexible Rhomboid: most flexible Examples: Square: K-file Triangular: flexofile Rhomboid: K-flex Circular: Hedstrom file S-shaped: Unifile 7

8 The manufacturing ways to make an instrument are either; Twisting Or Machined-cutted (more susceptible to fracture). *note: this is the most important and first category to think of in classification of instruments; we call it the broad classification. *twisted: twisting the cutting edge of a blank in order to create the cutting edges. The more the twisting the more the cutting edges. The two ends of a blank, tapered pyramidal wire are stabilized (top), and then one end is rotated to create a spiral shape on the file's working surface (middle). Multiple rotations produce the final spiral shape (bottom). *so, types of hand instruments according to the cutting edges are wither twisted or machined. *the size of the instrument increases as the diameter increases; the larger the diameter the less the flexibility or the more the rigidity. 8

9 Square small size Triangle large size as a form of compensation. *a note for the clinical use: Files can be both filed and reamed but Reamers can only be reamed Now, reamers and files: Difference: 1. The file is more twisted/ more cutting edges in each mm/ for the reamer because the cutting edges are less they come almost parallel to the long axis of the instrument whereas in the file because of more cutting edges we find them angled with the long axis. 2. Working method/ mechanism or mode of action: The reamer reaming action/ rotation; you keep rotating till it cuts. The file filing action because of that angle of the cutting edges to the long axis we can move it upward and downward within a small distance in order to cut the walls of the canal. 3. Files can be both filed and reamed. Reamers can only be reamed *slide 28: K-flexoreamer means that its manufacturing alloy is stainless steel 9

10 *slide 29: K-flexo file same thing; only different from the k-file in the alloy (stainless steel) *Hedstroem-file or H-file: Machined instrument category (cutting edges made by a machine) Cross-section: Inverted cones (almost circular check slide 32) Cutting edges are perpendicular to the long axis of the instrument and this explains its mechanism of action; it cuts while going upward and not while going downward this is called the pulling stroke mode of action. This instrument is fragile because its cones are small thus, never rotate it inside the canal. K-flex (rhomboid) 10

11 Standardization: Started in the 50s, and means that they found a standard size that defines the tapper, size, length of cutting blade, and tip angle. American National Standards Institute (ANSI) International Organization for Standardization (ISO) And accordingly, our instruments are now classified into: 1. D0 or D1: diameter of the tip (taper) 2. D16 or D2: diameter from the tip to the end of the working segment that is equal to 16 mm in length. *an instrument size 15 D0 of this instrument = 0.15 mm diameter. *tip angle = 75 degrees. * they also standardized the filling ( حشوة العصب ) so that it matches the gutta-percha. Note that Now the upcoming part is all about hand-instruments : The instrument s diameter increases starting from the tip being 0 (D0) till it reaches 16 mm (D16). 02 taper means that the instrument diameter increases by 0.02 mm with each 1 mm back from instrument tip. Also called 20% taper. There are greater tapers than 02 taper (04, 06, 08, 10,.. taper) but this one is that we re going to work on. Color coding: *memorizing the colors is a must. 11

12 All are H-files Color = size Grey: 08 (not showing in this picture) Purple: 010 its D0 = 0.1 mm these two are used in very small canals (forget about them for now) ; however, cleaning and shaping and working length is concerned with sizes 015 and above. White : 015 its D0 = 0.15 mm Yellow: 020 its D0 = 0.20 mm And so on Notice that the colors are repeated after black, but this wont make a problem because two of the same color are easy to identify by the size. Also notice that the size is increasing by 0.05 mm till we reach size 060 it increases by 0.10 mm to 0.70 then another 0.10 mm to 080. Example: cutting segment = 16 mm/ 02 taper = 0.02 mm increase with each 1 mm/ D0 according to the color now we can calculate the D16 Q: what is the D16( diameter at the end of the cutting segment) for file number 015? (0.02 x 16 length ) + initial value (which equals to 0.15 in this Q). now the answer is: 0.47 mm Between 010 and 015 there is a 50% percentage increase in tip diameter but between 015 and % defect in the instrument, and therefore manufacturers have produced an intermediate size; 013 for example between 010 and 015 and 017 between 020 and 015. They also have produced (for marketing purposes) what they called constant increase in the tip diameter between file and file; for example 29%. Now as you know roots differ in length and there is a no way to work on a molar with a restricted area and a restricted mouth opening using a file of 31 mm in length when the root is only 20 mm in length. Also on the other hand, we don t use a file of 10 or 19 mm in length for a 27 mm root of a canine (because in both cases this will cause us difficulties in working), and therefore they invented different lengths as to compatibilitate with the length of the root. 12

13 Barbed broaches: Made from soft steel wire fragile contraindications: very fine canals. And thus used only in anteriors or premolars, but for the rest of the teeth use the files and the irrigation techniques. The barbs are formed by cutting into the metal The tip of the barbs points toward the handle Used to remove pulp tissue or cotton wool dressing Removal of pulp tissue Wide, straight canals only May engage walls of narrow canal and break Use excavator to remove contents of pulp chamber in molars 13

14 Now the doctor went through some notes on the magnificated photos as the following; K-file: Note the clean surface and rounded tip. K-flexfile: This file resembles a classic K-file with its twisted pattern. The cross section of the blank is rhomboid, giving the instrument a small and a large diameter that can be clearly seen. Note the untwisted tip. H-file: The rake angle is close to neutral (arrow), which makes this instrument very efficient for machining strokes Flexofile: a milled K-type file. Note the smooth surface and well-formed tip. Flex-R file (Union Broach): a milled K-type file. The flutes are sharper and have a less negative rake than a traditional twisted K-file. The tip is rounded. 14