Endodontics. Definition. Clinical and anatomical structure of teeth’ cavities and root canals of teeth. Endodontic instruments. Basic endodontic manipulation: trepanation of tooth cavity, amputation, extirpation of the pulp. Methods of medical and instrumental treatment of root canals ("Step-Back", "Crown-down" technique). Medicines. Mistakes and complications.

Lecturer: Levkiv Mariana O.Department of Therapeutic DentistryTSMU

• Endodontics is the science that study anatomy, pathology, and treatment of tooth cavity and root canals.

• Under endodontic intervention it should be understand any interference with the purpose of treatment, carried out through the cavity of the tooth.

• Under root canal treatment should be understood odonto-surgical intervention inside the tooth in order of its preservation with the subsequent restoration of its form and function with the help of therapeutic or prosthetic methods.

• In endodontic practice the knowledge of topographical anatomy of dental cavities of different groups of teeth is necessary.

• The root canal is divided into crown, middle and apical parts.

• The crown part is the widest and adjacent directly to canal orifices.

• Most canals are flattened mesio-distally, but become more rounded in the apical 1/3. Lateral canals are branches of the main canal and occur in 17-30% of teeth.

• In the apical part near the dentinal-cement border root canal ends with a constriction (physiological apical hole), which is usually placed at a distance of 0.5-1.0 mm from the radiological apex.

• Some authors identify anatomical apical hole - a place of transition the dentin into cement, and physiological hole - the border between pulp and periodontium, placed 1 mm away from the X-ray hole.

• The apical foramina are usually sited 0.5-0.7 mm away from the anatomical and radiographic apex.

• The apical constriction usually occurs 0.5-0.7 mm short of the foramina. These distances with age due to ⇑deposition of secondary cementum. Root-filling to the constriction provides a natural stop to instrumentation, thus the working length should be established 1-2 mm from the radiographic apex.

• The dentist who conducts endodontic manipulations before the start of treatment should identify options for topographic and anatomical structure of the tooth.

Topographical and anatomical features of teeth cavities of different group of teeth.

Endodontic instruments• According to ISO endodontic instruments are classified:

• Hand instruments: files(K and H), barbed broaches, spreader and plugger (vertical and lateral gutta percha condensors ).

• Rotary instruments: H-files and K-reamers for slow handpiece, lentulo spiral filler/rotary paste filler.

• Rotary instruments: Gates Glidden drills, Peeso reamer drills.

• Pins: gutta percha pins, silver pins.

• But its more convenient to use classification by Curson(1996) that is based on clinical usage of endodontic instruments.

• - diagnostic instruments: root needles(Miller needles)

• - instruments for removing the soft teeth’ tissues: barbed broaches

• - instruments for passing and enlargement of root canals

• (K-reamers, K- files, H-files)

The main endodontic instruments and their useBarbed broaches

•Functions and precautions

•• Finger instruments

•• Disposed of in the sharps’ container

••Used to remove the intact pulp

•• ‘Barbs’ on the broach snag the pulp

• to facilitate removal

•• They need to be used cautiously as

•they can bind and break in the canal

•Varieties

•Available in different sizes and widths

• Gates Glidden drills• Function, features and precautions

• •To enlarge the coronal third of the canal during endodontic treatment

• • Small flame-shaped cutting instrument used in the

conventional handpiece

• • Different sizes – coded by rings or coloured

bands on shank

• •Are slightly flexible and will follow the canal

shape but can perforate the canal if used too deeply

• • Dispose of in sharps’ container

• • Should be used only in the straight sections of

• the canal

• Peeso reamer drillsFunction, features and precautions

• •To remove gutta percha during post preparation

• • Small flame-shaped cutting instrument used in the conventional handpiece

• • Different sizes – coded by rings or coloured

bands on shank

• • Peeso reamers are not flexible or adaptable,

if not used with care can perforate canal

• • Dispose of in sharps’ container

• Reamers Rarely used or indicated. Disadvantages of reamers include their inflexibility with size, which can result in a wider canal being cut ⇑apically. Have now been replaced by files.

•

• Files These are used either with a longitudinal rasping or a rotary action (e.g. clockwise direction).

• The main types of file available are:

•

• K-type-file Made by twisting a square metal blank.

• Hedstroem file Made by machining a continuous groove into a metal blank. More aggressive than K-file. Must never be used with a rotary action as liable to fracture.

•

• K-flex file Similar to K-file but made by twisting a rhomboid shape blank alternating blades with acute and obtuse angles. More flexible than K-file but becomes blunt more quickly.

•

• Flex-o-file Looks similar to a K-type-file but is made from a triangular blank of a more flexible steel. The file also has a blunt tip, which means that it is unlikely to create a false canal. This file is more flexible than K-types and is now becoming a popular replacement.

• Gretaer taper (GT) Hand files made from nickel titanium (NiTi). They have increasing tapers (0.06-0.12) with matched GP cones.

• Files have traditionally been made from steel, but newer varieties made of NiTi are gaining popularity as they are much more flexible. Larger-sized files can be sterilized and re-used more than the smaller sizes. All instruments should be examined regularly, and discarded if there are any signs of damage. It is good practice to dispose of smaller files after one use. In future files may all be single use (disposable).

• NiTi rotary instruments (Profile) reduce creation of blocks, ledges, transportations and perforations by remaining centred within the natural path of the canal. Useful for curved canals but risk of fracture. Prior to use ⇑check for patency/ glide-path up to the full working length with a size 10 file.  

• Endodontic K files. Also called: Root canal hand files• Function, features and precaution

• • Finger instrument

• • Colour coded by size. The 6 colours used most often are: size 15 (white); 20 (yellow); 25 (red); 30 (blue); 35 (green); 40 (black). Also available in size 6 (pink), 8 (grey) and 10 (purple)

• • Operator gradually increases the size of the

• file to smooth, shape and enlarge canal

• • The larger the number of the file, the larger

• the diameter of the working end

• • Disposed of in the sharps’ container

• Varieties

• • Different lengths: 21mm, 25mm and 30mm

• • Hedstrцm files, Flexofiles®

• NiTi (Nickel titanium) rotary instruments• Function, features and directions for use

• • Used to clean and shape the canals

• • Used with endodontic handpiece and motor

• • NiTi is flexible and instruments follow the

• canal outline very well

• • Several varieties of systems with different

• sequences of instruments are used

• • Important to follow the manufacturer’s

• recommended speeds and instructions for use

• Varieties

• Different lengths: 21mm and 25mm

• Lentulo spiral filler/rotary paste filler

• Function and features

• • Small flexible instrument used to place materials into the canal

• • Fits into the conventional handpiece

• • Use with caution as it can be easily broken

• • Different sizes available

Geometric symbols of endodontic instruments

Access to cavity preparations

• The main purpose of root canal treatment is:

• removal of pulp;

• removal of infected dentine from the inner wall of the root canal;

• expansion and forming a root canal for its adequate filling.

This procedure of root canal treatment consists of such stages:

• -disclosure of the tooth cavity;

• - disclosure of the root canal orifices;

• - the root canal passing;

• - the root canal enlargement;

• - the root canal shaping.

Manipulations of root canal treatment(RCT) are carried out manually or with the help of rotary instruments by several treatment methods, the most widespread among them are:

•apical-crown - envisage treatment from the apical hole to canal orifices with gradually increasing of instrument diameter( e.g. from №10 -№ 40)

•crown-apical - envisage root canal

treatment that starts from canal orifices

to apical hole with a gradual decrease

in instrument diameter(e.g. from №40 –

№ 10)

•Combined method of treatment:

Step-back technique The apical part of the root canal is prepared first and the canal is then flared from apex to crown. Blockage of canals may occur using this technique, and irrigation can be difficult.

Crown-down technique This (along with several others) prepares the coronal part of the canal before the apical part. This has advantages and is the preferred technique.

Balanced force technique This involves using blunt-tipped files with an anticlockwise rotation whilst applying an apically directed force. It requires practise to master but is particularly useful when preparing the apical part of severely curved canals.

Anticurvature filing This was developed to minimize the possibility of creating a 'strip' perforation on the inner walls of curved root canals. It is used in conjunction with other techniques or preparation, and the essential principle is the direction of most force away from the curvature.

• Advantages of orifice enlargement • • Effectively, the curvature in the coronal part of the root canal, ⇓

allowing straighter access for files to the apical region. It therefore reduces the likelihood of apical transportation (zipping).

• • It allows improved access for the flow

of irrigant solution within the canal.

• • It reduces the likelihood of apical extrusion

of infected material as most of the canal

debris is removed before apical instrumentation

takes place. This is particularly important

because the majority of bacteria in an infected

root canal are located in the coronal region.

• Passing and enlargment of root canal (especially narrow and sclerosed) is not always possible to implement using only endodontic instruments. In such cases, additional chemical expansion is conducted .Such technique involves the use of different types of acids for decalcification of dentin.

• In root canal treatment is often used products based on EDTA.

• For chemical enlargement of a root canal a small amount of gel product is applied to endodontic instruments and mechanical treatment of root canal is performed. The procedure is repeated several times. After obtaining the required result, canal is washed with solution of sodium hypochlorite or distilled water.

Drugs for chemical enlargement of root canals

Type of active ingredient The product, the manufacturing company

A solution of EDTA Largal ultra (“Septodont”) Edetat solution (“Pierre Roland”)Endofree (“Dencare”)

A solution of citric acid and propionic acid

Verifix (“Spad”)

Gels based on EDTA Canal+ (“Septodont”) HPU15 (“Spad”)RC-prep (“Premier”) Канал Глайд («Радуга-Р»)

Root canal treatment should include thorough mechanical debridement and medication treatment as well (antiseptic solutions), these two procedures should go together.

Irrigants. These are required to flush out debris and lubricate instruments. Dilute sodium hypochlorite is generally considered to be the best irrigant as it is bacteriocidal and dissolves organic debris. The normal concentration is 2.5% available chlorine. Chelating agents which soften dentine by their demineralizing action are particularly helpful when trying to negotiate sclerosed or blocked canals.

Prepared root canal for sealing, regardless of the method of instrumental treatment, must fulfill the following

criteria as: To be sufficiently enlarged;To have a conical shape;To have formed apical ledge;Do not contain a necrotic dentin;Do not have typical smell;To be clean and dry;Do not have a painful reaction to percussion.

• Common errors in canal preparation

• • Incomplete debridement : working length short, missed canals.

• • Lateral perforation : often occurs as a result of poor access.

• • Apical perforation : makes filling difficult.

• • Ledge formation : can be very difficult to bypass.

• Apical transportation (zipping) A file will tend to straighten out when used in a curved canal and straightening can transport the apical part of the preparation away from the curvature. The use of flexible files reduces the likelihood of this happening.

• Elbow formation When apical zipping happens, a narrowing often occurs coronal to this in the canal such that the canal is hourglass in shape. This narrowing is termed an elbow.

• Strip perforation A perforation occurring in the inner or furcal wall of a curved root canal, usually towards the coronal end.

SOME ENDODONTIC PROBLEMS AND THEIR MANAGEMENT

•Fractured instruments. Sometimes it is possible to get hold of the fractured portion with a pair of fine mosquitos. If not, insertion of a fine file beside the instrument may dislodge it. Should the fractured piece be lodged in the apical portion of the canal it may be better to fill the canal below it and keep it under observation, resorting to an apicectomy as a last-ditch solution.

•Fractured instrument removal. Ultrasonic vibration may be used to facilitate fractured instrument removal.The clinician must take care to ascertain the type of metalic obstruction because nickel-titanium (NiTi) and stainless steel respond differently to ultrasonic vibration. Direct ultrasonic vibration causes NiTi to fragment, so the clinician must work carefully around the fragment. Stainless steel is more resistant to vibration and responds to it by subsequently loosening.

•Ultrasonic vibration is applied directly to stainless steel files. Fine inserts can be used to work counter-clockwise around broken instruments. This technique often results in an “unscrewing” action that assists in removal.

• Recurrent symptoms/intractable infection If thorough cleaning and repeated dressing of the canal with calcium hydroxide are unsuccessful, it may be necessary to do an apicectomy. Do not routinely turn to surgery for failed cases consider retreatment in the first instance.

• If careful exploration with a small file is unsuccessful, investigation of the expected position of the canal entrance with a small round bur may help. Once the canal is found, a No. 8 or 10 file should be used to try and negotiate it, using EDTA, File Eze, or RC Prep as a lubricant, and the canal prepared and filled conventionally. Success rates of 80% have been reported for canals that were hairline or undetectable on radiographs.28 Occasionally, a total blockage of the canal is encountered, in which case the filling is placed to this level and/or an apicectomy done.

• Pulp stones in the pulp chamber can usually be flicked out. If they occur in the canal use EDTA and a small file to try and dislodge them.

• Pain following instrumentation. This is usually due to instruments or irrigants, or to debris being forced into the apical tissues. Placement of a small amount of Ledermix(Antibiotic/steroid paste ) in the canal may provide symptomatic relief, but care is required not to breach the apex. Occasionally, an acute flare-up of a previously asymptomatic tooth occurs following initial instrumentation this is called a phoenix abscess. Loss of face is saved by warning patients that this can happen. Affected teeth should be opened and irrigated and if possible resealed. This may need to be repeated after 24-48 h.

• Perforations can be iatrogenic or caused by resorption

In the latter case, dressing with non-setting calcium hydroxide may help to arrest the resorption and promote formation of a calcific barrier. Increasingly MTA is being used for the repair of perforations and in surgical endodontics as a retrograde filling material with excellent results. Management of traumatic perforations depends upon their size and position:

• Pulp chamber floor If small perfortion, one can cover with calcium hydroxide and fill with GP or GI, but if large, hemisection or extraction may be necessary.

• Lateral perforation If this occurs near the gingival margin it can be incorporated in the final restoration of the crown, e.g. a diaphragm post and core crown. If in the middle 1/3, the remainder of the canal may be cleaned by passing instruments down the side of the wall opposite the perforation. Then the canal can be filled with GP, using a lateral condensation technique to try and occlude the perforation as well. Larger perforations may require a surgical approach and in multirooted teeth hemisection or extraction may be unavoidable.  

• Apical 1/3 It is usually worth trying a vertical condensation technique to attempt to fill both the perforation and the remainder of the canal. If this is unsuccessful an apicectomy will be required.

• Ledge formation If this occurs, return to a small file curved at the apex to the working length and use this to try and file away the ledge, using EDTA or RC- Prep as lubricants.

Thank you for your attention