Sterilization

Any instrument which is placed in the root canal should be sterile, for two reasons. Firstly, to prevent the introduction to the root canal system of extraneous microorganisms, which may severely compromise treatment, for example pseudomonas.
Secondly, if instruments and devices were to be used on different patients, to prevent cross-infection between patients. Bacteria, viruses, fungi and prions may contaminate instruments and research has shown that some of these may not be destroyed by any method of sterilization.
Figure 18 illustrates this dramatically. Concern has been raised over the sterilization of other items of dental equipment as well.

Measurement of working length

There are two established methods of assessing the working length of a root canal: one by radiography and the other with the use of an electronic device apex locator (Fig. 16). 

Once the working length has been confirmed, the individual preparation instruments must be accurately marked to length accordingly. There are many different gadgets available for transfer of the working length; the author prefers the device shown in Figure 17. There are also different stops for the instrument, the most popular being rubber or silicone stops. These should always be placed at right angles to the shank of the instrument. Ideally the stops should be either notched, or pear shaped, so that in curved canals the notch or point of the pear may be directed towards the curve placed in the instrument. 

Both methods will be described in Part 7.
Once the working length has been confirmed, the individual preparation instruments must be accurately marked to length accordingly. There are many different gadgets available for transfer of the working length; the author prefers the device shown in Figure 17. There are also different stops for the instrument, the most popular being rubber or silicone stops. These should always be placed at right angles to the shank of the instrument. Ideally the stops should be either notched, or pear shaped, so that in curved canals the notch or point of the pear may be directed towards the curve placed in the instrument.

Burs

Several types of bur may be required for root canal treatment. Some of these are described below, and shown in Figure 14.

Cutting an access cavity
It is generally accepted that high speed burs should be used to gain access and shape the cavity. A diamond or tungsten carbide tapered fissure bur is used for initial penetration of the roof of the pulp chamber. A tapered safe-ended diamond or tungsten carbide bur is then used to remove the roof of the pulp chamber without damaging the floor. 

Location of canal
Burs should only be used as a last resort to locate a sclerosed canal because of the danger of perforation. Small round burs are used; the standard length is usually too short but longer shank burs are available. Specially designed ultrasonic tips may also be used to remove secondary dentine, assist in the identification of canal orifices and in shaping the canal orifice during preparation. The use of ultrasonic tips has become more widespread with the introduction of a wider range of fittings to different piezo-electronic machines. Figure 15 shows the diamond coated CPRfi tips, designed for troughing and chasing sclerosed canals, and the BUCfi tips, with variable grades of diamond grit for refining access cavity walls and line angles, removing obstructions and cutting around posts. As with all instruments and materials, the manufacturer s instructions and guidance should be carefully followed or these delicate diamond tips may be damaged. It is generally wise to use them with a low power setting, and to ensure that they are in contact with dentine before activating the piezoelectric unit.

Canal preparation
The use of rotary cutting instruments in a standard handpiece is condemned because of the danger of fracture of the instrument or perforation of the root canal. The exception to this rule is the Gates Glidden bur, which has a safeended tip. In addition, the site of fracture, if it does occur, is almost always near the hub so the fractured piece is easily removed. In the past this bur has been recommended for initial flaring of the coronal portion of the canal. This may now be carried out in a more controlled manner with a nickel-titanium orifice shaper. The Gates  Glidden bur may also be used to make post space and to remove gutta-percha from the canal. Gates Glidden burs are manufactured in six sizes; their use is described in Part 7

Irrigation and lubrication materials

It is generally accepted in endodontic practice that sodium hypochlorite is the most suitable solution for irrigation of the root canal system. Normal household bleach is approximately 5.5% sodium hypochlorite solution, and this may be diluted with purified water up to five times to the operator s preference. Research has shown that the antibacterial effect is the same for a 0.5% and a 5.0% solution.

However, the greater the dilution the less effective is the solution at dissolving organic debris in the root canal system. 
Great vigilance is essential when using sodium hypochlorite, and practitioners must be aware of the risks and dangers involved in its use. Irrigation under pressure may force the solution through the apical foramen into the periradicular tissues, which may result in a rapid, painful and serious inflammatory response. The patient will be extremely distressed, and little can be done to relieve the situation which may take several days to resolve. Cases have also been reported where excess pressure on the syringe has resulted in the needle coming loose and hypochlorite spraying over the patient, operator and assistant. Protective goggles are essential for the patient and all staff. Clothing should also be protected. The defence societies have received claims from irate patients for damaged clothing following root canal treatment. The practitioner must have appropriate risk assessment procedures in place when such materials are incorporated into their clinical practice.
Chlorhexidine solution 0.2% has a similar antibacterial action, but will not dissolve the organic debris found in parts of the canal system inaccessible to hand instrumentation, such as lateral canals, fins and apical deltas. However, the substantivity associated with this irrigant means that it will adhere to dentine, thereby exhibiting a prolonged antibacterial activity. Although chlorhexidine may not be quite as effective as sodium hypochlorite, its use should not be dismissed.
Researchers are constantly seeking improved methods of cleaning root canals; reports have appeared recently relating to the use of electroactivated water as an irrigant,and the use of high frequency electric current. These and others may prove interesting developments in root canal preparation and irrigation.
EDTA paste (Ethylenediamine tetra-acetic acid) is a chelating agent which softens the dentine of the canal walls and greatly facilitates canal preparation (Fig 13). EDTA solution may be used as an irrigant at the end of the canal preparation phase to assist removal of the smear layer prior to placement of an intervisit dressing, or obturation.

Power-assisted instruments

Handpieces providing a mechanical movement to the root canal cutting instrument have been available since 1964. Their function was primarily a reciprocating action through 90  and/or a vertical movement, according to the design and make. Because steel files do not have the flexibility necessary for rotary movements in a curved canal without damaging the canal configuration, these instruments were never really acceptable in endodontic practice. A totally new concept in canal preparation came with the development of sonic and ultrasonically activated endodontic handpieces. Much research took place into the mode of action and effectiveness of these machines. It was generally agreed that while the sonic machines were more effective at hard tissue removal, the ultrasonic machines were more effective in irrigation. The piezo-electric machines were found to be more effective than the magnetostrictive. The latter also generated more heat, and irrigation with effective quantities of sodium hypochlorite was found to be difficult. The ultrasonic action causes acoustic microstreaming of the irrigant, intensive circular fluid movement carried right to the tip of the instrument, found to be very effective at canal debridement. This effect is reduced, however, when the file is constrained by the canal wall. The main use of these instruments today is in irrigation and debridement, using a freely oscillating file in a sodium hypochlorite filled canal, after thorough mechanical canal shaping. However, the development of nickel-titanium alloy for endodontic instruments has allowed the concept of an engine driven endodontic instrument to be fully explored. The total flexibility of this alloy, and the use of radial lands on the cutting flutes to keep the instrument centred in the canal, permit controlled cutting of the dentine walls. Most major manufacturers have developed a nickel-titanium rotary system. Lightspeed, Profiles, GT Rotary files, FlexMaster, Quantec system, Hero, K3, Protaper, and no doubt more will appear before this book is even published. It would not be possible to describe each of these fully, but the basic concepts are presented here, with a general description of their use being given in Part 7.
The systems will generally conform to one of three patterns.

Reamer

The reamer is constructed from a square or triangular blank, machine twisted into a spiral but with fewer cutting flutes than a file. The reamer will only cut dentine when it is rotated in the canal; the mode of action described for its use is a quarter to a half turn to cut dentine, and withdrawal to remove the debris. The stiffness of an instrument increases with each larger size, so that larger reamers in curved canals will tend to cut a wider channel near the apical end of the root canal (apical zipping). Considerable damage may be caused to a root canal by the incorrect use of a reamer, and their routine use is no longer recommended.

Other hand files

Different types of hand file have been introduced from time to time with varied structure and cutting action. The Unifile and Helifile were modifications of the Hedstroem design. The Mani Flare file is made from a triangular blank, and features a greater taper than conventional 2% files. It is essential when considering the use of new file designs that the operator understands the basic principles of canal preparation, and compares and contrasts the properties with the file manipulation technique currently being used.

Hedstroem file

The Hedstroem file is machined from a round tapered blank. A spiral groove is cut into the shank, producing a sharp blade. Only a true filing action should be used with this instrument because of the angle of the blade. There is a strong possibility of fracture if a reaming action is used and the blades are engaged in the dentine. The Hedstroem file is useful for removing gutta-percha root fillings.

K-type file

These instruments were originally made from a square or triangular blank, machine twisted to form a tight spiral. The angle of the blades or flutes is consequently near a right-angle to the shank, so that either a reaming or a filing action may be used. The K-type file has been subject to continuous development. The K-flex file is made from a rhomboid or diamond shaped blank. The acute angle of this shape provides the instrument with two sharp blades and the narrower diameter allows greater flexibility in the shaft than a conventional K-file. The manufacturers claim that more debris is collected between the blades and therefore removed from the canal than with a standard K-file. The Flex-o-file employs a more flexible type of steel. It does not fracture easily and is so flexible that it is possible to tie a knot in the shank of the smaller sizes.
The latest developments in file design have seen a move away from the ISO standard 2% taper to files with increasing tapers of up to 12%, made in a nickel-titanium alloy. Although most of these new developments are used with an electric motor, hand files of greater taper are available. These are illustrated in Figure 11. Their use is described in Part 7.

DEVELOPMENT OF HAND INSTRUMENTS

For many years the standard cutting instruments have been the reamer, K-type file and Hedstroem file. These root canal preparation instruments have been manufactured to a size and type advised by the International Standards Organisation (ISO). The specifications recommended are complex and differ according to the type of instrument. For most standardized instruments the number refers to its diameter at the tip in one-hundredths of a millimetre; a number 10, for example, means that it has a tip diameter of 0.10 mm. Colour coding originally denoted the size, but now represents a sequence of sizes. All these instruments have a standard 2% taper over their working length.
Recent changes in both metallurgy and endodontic concepts have led to the introduction of a range of new instruments which do not conform to these specifications. These are described individually later and in Part 7. These instruments have been widely adopted, and appear to give consistently better results in root canal treatment. However, the conventional 2% taper instruments are essential for the initial exploration of most root canals, for difficult procedures such as bypassing separated instruments, and for the apical preparation of some difficult canals. 

RADIOGRAPHIC EQUIPMENT

Long-cone parallel radiography is a requirement for endodontics, because it gives an undistorted view of the teeth and surrounding structures and is repeatable, thus allowing more accurate assessment of periapical healing. The bisecting angle technique should no longer be employed. It is further recommended that rectangular collimation be fitted on all new radiographic equipment, and retro-fitted to existing equipment as soon as possible. There are many beam-aiming devices available to hold the x-ray film parallel to the tooth. Figure 5 shows an example of a popular holder, with a special cage attachment to fit over a rubber dam clamp.

A quick, reliable method of viewing radiographic images is essential for endodontics. Considerable time can be lost if such a system is not available, especially on those occasions when the exposed film does not show the required detail. Practitioners using conventional radiography may wish to purchase an x-ray film processor with rapid developing and fixing solutions, capable of producing a radiograph for viewing in under a minute; an example is shown in Figure 6. However, a modern automatic processor (Fig. 7) may be adjusted to deliver wet films in under two minutes. Films from both types of processor should be carefully dried after viewing for accurate storage in the patient s records. A modern alternative involves the use of digital radiography. A sensor plate, appropriately sterilized and sealed, is used in place of the conventional film. The sensor may be either directly linked to the computer, or resemble a conventional periapical film packet. The resultant image is digitally processed and projected upon the computer screen in a matter of seconds. The quality of the image can be manipulated to enable greater clarity when reading the picture. For purposes of record keeping, the image may be either dated, labelled and stored in the central database, or a hard copy printed for the patient s records. An example of such a system, and the images produced, is shown in Figure 8.

RUBBER DAM

Rubber dam is essential in root canal treatment for three reasons: To provide an operating field free from oral contamination. To prevent the patient swallowing or inhaling root canal instruments or medicaments. To give good visual access by retracting the lips and tongue. A basic kit for rubber dam equipment is shown in Figure 4. Details of this equipment, and of the techniques for the application of rubber dam, are given in the next part.

PATIENT PROTECTION

Glasses are needed to protect the patient s eyes. Figure 3 also shows a waterproof bib being worn, as the patient s clothes must be protected against accidental spillage of sodium hypochlorite, a frequent source of patient complaint or even litigation.

INSTRUMENT PACK

A basic pack of instruments must be available specifically for routine root canal procedures. An example is given in Figure 1.

A front surface reflecting mouth mirror is preferable to prevent the double image of the fine detail in an access cavity that occurs with a conventional mirror. Endolocking tweezers allow small items to be gripped safely and passed between nurse and operator. A DG16 endodontic probe is required to detect canal orifices. The excavator is long shanked, with a small blade to allow access into the pulp chamber. The pocket-measuring probe is useful, a routine CPITN probe with clearly visible gradations is ideal. A furcation probe is useful to check for the presence of furcation involvement. Other items usually included are a flat plastic, sterile cotton wool rolls, sterile cotton wool pledgets, artery forceps to grip a periapical radiograph and a metal ruler, or other measuring device that may be sterilized. A clean-stand or other device such as the endoring is required to hold the endodontic instruments. Paper points are also required, and the simplest method of storage and use is to purchase presterilized packs with five points in each pack.

Endodontics: Part 5 Basic instruments and materials for root canal treatment

Many dental practitioners find it difficult to resist new gadgets, and there are an inordinate number made specifically for endodontics. New instruments and materials are frequently sold with the promise of simplifying a technique, shortening the time taken or even increasing the success rate.

Unfortunately, these promises are often not fulfilled, and the result may be cupboards in the practice containing unwanted endodontic armamentaria. It would be impossible to cover all the instruments and materials used in endodontics in one part, but it is hoped to mention most of the basic equipment and discuss some of the newer items. 

For continuity, some instruments will be described in the relevant parts. The majority of the instruments and materials referred to in this part are generic, and may be purchased from most dental supply companies.

MANDIBULAR THIRD MOLAR

Together with the maxillary third molar, this tooth displays some of the most irregular canal configurations to be found in the adult dentition, as seen in Figure 11.

However, the mesial inclination of the tooth generally makes access easier. The canal orifices are not too difficult to locate, but the degree of curvature of the apical half of the root canal system is often pronounced. Added to this, the apex is frequently poorly developed and lies close to the inferior alveolar canal. A large access cavity allowing direct visualization of the floor of the pulp chamber enables the canal orifices to be identified. 
It should always be remembered that whilst the above descriptions are the norm, occasionally other teeth may be encountered with unusual or even bizarre anatomy. This may only be discovered after the treatment has failed and the tooth has been extracted. Clues may sometimes be found by careful examination of the radiographs, especially with the use of magnification, as described in Part 5.

MANDIBULAR SECOND MOLAR

This tooth is similar to the mandibular first molar, although a little more compact. The mesial canals tend to lie much closer together, and the incidence of two canals distally is much less. This tooth seems to be more susceptible to vertical fracture. Occasionally, the root canals may join in a buccal fin giving a  C-shaped  canal, which may lead all the way to the apex. The access cavity is similar to that of the first molar.

MANDIBULAR FIRST MOLAR

This is often the most heavily restored tooth in the adult dentition and seems to be a frequent candidate for root canal treatment. Generally there are two roots and three canals: two canals in the mesial root and one large oval canal distally. According to Skidmore and Bjorndal, one third of these molars have four canals. Occasionally, three roots are to be found: usually two distal and one mesial (Fig. 10),

rarely one distal and two mesial. Anastomoses occur between the canals and accessory communication with the furcation area is a frequent finding. The mesiobuccal canal tends to exhibit the greatest degree of curvature. The access cavity once again represents the shape of the pulp chamber, enlarged slightly, and flared up on to the mesiobuccal aspect of the occlusal surface to accommodate the angle of instrument approach when working at the back of the mouth.

MANDIBULAR SECOND PREMOLAR

This tooth is similar to the first premolar, except that the incidence of a second canal is very much lower. One study stated this to be 12%. Another study revealed that only 2.5% had two apical foramina. Consequently, it is a much easier tooth to treat compared with the mandibular first premolar, unless the radiograph reveals a sharp distal curve at the apex as shown in the extracted tooth at Figure 9.

MANDIBULAR FIRST PREMOLAR

The canal configuration of this tooth can be quite complex. Vertucci Fig. 9  A lower second premolar with a severe distal curve at the apex. has shown that the single canal normally found may divide into two canals and two apical foramina in 25% of cases. It is the way in which the second canal branches that can cause difficulty with instrumentation. Occasionally, the canal terminates with an extensive delta, making obturation of the accessory canals even more challenging. As in the upper premolars, the access cavity is oval between the cusp tips. 

MANDIBULAR CANINE

This tooth is similar to its opposite number, although not as long. On rare occasions, two roots may exist and this can cause difficulty with instrumentation (Fig. 8). 

An oval access cavity is again indicated.

MANDIBULAR CENTRAL AND LATERAL INCISORS

The morphology of these two teeth is very similar. The central incisor has an average length of 20.5 mm and the lateral is a little longer with an average length of 21 mm. Over 40% of these teeth have two canals, but only just over 1% have two separate foramina. Careful reading of the pre-operative radiograph may show a change in the radiodensity of the root canal, indicating division into two separate canals, and a correctly designed access cavity will facilitate checking for a second canal. This is oval in shape, commencing above the cingulum and almost notching the lingual incisal edge.

MAXILLARY THIRD MOLAR

The morphology of this tooth can vary considerably, ranging from a copy of the first or second maxillary molar to a canal system that is quite complex. They are best explored with a wide access cavity and direct vision of the individual canal anatomy.

MAXILLARY SECOND MOLAR

This tooth is similar to the first maxillary molar, but slightly smaller and shorter, with straighter roots and thinner walls.

MAXILLARY FIRST MOLAR

This tooth has three roots. The palatal root is the longest, with an average length of 22 mm; the mesiobuccal and distobuccal roots are slightly shorter, at 21 mm average length. The percentage of mesiobuccal roots having two canals reported in the literature has increased steadily as research techniques have developed. In vitro studies have usually reported a higher incidence than in vivo studies. Stropko, reporting an extensive in vivo study,
found second canals in 73% of cases before the use of an operating microscope, but 93% following its use. The canals of the mesiobuccal root are often very fine and difficult to negotiate; consequently, more errors in instrumentation occur in this tooth than in almost any other. Anastomosis between these two canals may take the form of narrow canals or wide fins, both almost impossible to instrument.

MAXILLARY FIRST PREMOLAR

Typically, this tooth has two roots with two canals. In many ways this is the most difficult tooth to treat, as it can have a complex canal system. Variations range from one to three roots, (Fig. 5)

but there are nearly always at least two canals present, even if they exit through a common apical foramen. The roots of these teeth are very delicate and at the apical third they may curve quite sharply buccally, palatally, mesially or distally, so instrumentation needs to be carried out with great care (Fig. 6).

In a small percentage of cases the buccal root may subdivide into two canals in the apical third, as shown in Figure 7.

MAXILLARY CANINE

As well as being the longest tooth in the mouth, its oval canal often seems very spacious during instrumentation. However, there is usually a sudden narrowing at the apical 2 3 mm; this leads to a danger of overinstrumentation if too large a file is used at this level. The length of this tooth can be difficult to determine on radiographs, as the apex tends to curve labially and the tooth will appear to be shorter than it actually is. The oval shape of the root canal is reflected in the shape of the access cavity.

MAXILLARY LATERAL INCISOR

Similar in shape to the central incisors, but fractionally shorter, the apical third tends to curve distally and the canal is often very fine with thin walls. Labiopalatally, the canal is similar to the central incisor, but there is often a narrowing of the canal at the apical third level. The root is more palatally placed, an important point when any periradicular surgical procedures are carried out on this tooth. The access cavity is similar to the central incisor.

MAXILLARY CENTRAL INCISORS

These teeth almost always have one canal. When viewed on radiographs the canal appears to be fairly straight and tapering, but labiopalatally the canal will tend to curve either towards the labial or palatal aspect at about the apical third level. One feature to note is the slight narrowing of the lumen at the cervical level, which immediately opens up into the main body of the canal. The inverted-triangular shaped access cavity is cut with its base at the cingulum to give straight line access.

LATERAL AND ACCESSORY CANALS

As previously discussed, lateral canals form channels of communication between the main body of the root canal and the periodontal ligament space. They arise anywhere along its length, at right angles to the main canal. The term  accessory  is usually reserved for the small canals found in the apical few millimetres and forming the apical delta (Fig. 2). 

Both lateral and accessory canals develop due to a break in  Hertwig s epithelial root sheath  or, during development, the sheath grows around existing blood vessels. Their significance lies in their relatively high prevalence, Kasahara et al.
finding 60% of central incisors with accessory canals, and 45% with apical foramina distant from the actual tooth apex. Kramer found that the diameter of some lateral canals was often wider than the apical constriction.

Lateral canals are impossible to instrument and can only be cleaned by effective irrigation with a suitable antimicrobial solution. Consequently, sealing such canals is only moderately successful.

ROOT CANAL SYSTEM

The pulp chamber in the coronal part of a tooth consists of a single cavity with projections (pulp horns) into the cusps of the tooth (Fig. 1). With age, there is a reduction in the size of the chamber due to the formation of secondary dentine, which can be either physiological or pathological in origin. Reparative or tertiary dentine may be formed as a response to pulpal irritation and is irregular and less uniform in structure.

The entrances (orifices) to the root canals are to be found on the floor of the pulp chamber, usually below the centre of the cusp tips. In cross-section, the canals are ovoid, having their greatest diameter at the orifice or just below it. In longitudinal section, the canals are broader bucco-lingually than in the mesiodistal plane. The canals taper towards the apex, following the external outline of the root. The narrowest part of the canal is to be found at the  apical constriction , which then opens out as the apical foramen and exits to one side between 0.5 and 1.0 mm from the anatomical apex. Deposition of secondary cementum may place the apical foramen as much as 2.0 mm from the anatomical apex. It must be realized, however, that the concept of a  single  root canal with a  single  apical foramen is mistaken. The root canal may end in a delta of small canals, and during root canal treatment cleaning techniques should be employed to address this clinical situation.

Endodontics: Part 4 Morphology of the root canal system

This part may seem at first sight the most boring in the book, yet it could be the most important in improving clinical practice. Both undergraduate students and dentists on postgraduate courses frequently state that the reason they find root canal treatment so difficult, and the reason surveys frequently report inadequate treatment standards, is because they are working  blind . Unless a surgical microscope is available it is impossible to see down the root canal   to visualize exactly what the instruments are doing. An understanding of the architecture of the root canal system is therefore an essential prerequisite for successful root canal treatment (see Part 1, Fig. 1). As long ago as 1925, when Hess and Zurcher first published their study,

it became clear that teeth had complicated root canal systems rather than the simplified canals that had been previously described. 

POST-ENDODONTIC TREATMENT

The following factors need to be considered should pain occur following sealing of the root canal system.
  High restoration   Overfilling   Underfilling   Root fracture
Once obturation of the root canal space has been completed, restoration of the rest of the tooth can be carried out. The occlusion must be checked for interferences, to avoid an apical periodontitis, or worse, a fractured tooth.
Root fillings that are apparently overfilled do not as a rule cause more than mild discomfort after completion. The most likely cause of pain following obturation of the root canal space is the presence of infected material in the periapical region. The significance of an underfilled root canal is whether the canal has been properly cleaned and prepared in the first instance, and infected debris is still present in the canal. Postendodontic pain in these circumstances may well be due to inadequate debridement of the canal.
Removal of an overextended root filling is rarely completely successful and the options left are as follows:
  Prescription of analgesics and, if the pain is more severe and infection is present, antibiotics.
  An attempt at removal of the root filling and repreparation of the root canal.
  Periradicular surgery and apicectomy.
Root fracture

PATIENTS UNDER TREATMENT

Following endodontic procedures, patients may sometimes experience pain no matter how carefully the treatment has been given. It would be prudent to warn every patient to expect a certain amount of discomfort following endodontic treatment, advising them that this is caused by an inflammatory response at the tooth apex. They should be advised to take over-the-counter analgesics, preferably NSAIDs. However, if the pain persists for more than two or three days, further treatment is probably required for one of the following reasons.
Recent restorations
Pain may be a result of:   High filling
  Microleakage   Micro-exposure of the pulp   Thermal or mechanical injury during cavity
preparation or an inadequate lining under metallic restorations
  Chemical irritation from lining or filling materials
  Electrical effect of dissimilar metals.
It is not always possible to know beforehand whether there is a pre-existing pulpal condition when operative procedures are undertaken. Consequently, a chronic pulpitis may be converted into an acute pulpitis.
Periodontal treatment
There is always a chance that some of the numerous lateral canals that communicate with the periodontal ligament are exposed when periodontal treatment is carried out. This aspect is considered in the section in Part 9 on  perioendo lesions .
Exposure of the pulp
If a carious exposure is suspected, then removal of deep caries should be carried out under rubber dam. The decision to extirpate the pulp or carry out either a pulp capping or partial pulpotomy procedure depends on whether the pulp has been irreversibly damaged or not (see Part 9   calcium hydroxide). If there is insufficient time, or any difficulty is experienced with analgesia, temporary treatment, as recommended for irreversible pulpitis, may be carried out. Root or crown fractures
Most root or crown fractures can be avoided by adequately protecting the tooth during a course of root canal treatment. If the structure of the tooth is damaged between appointments, pain is likely to occur as a result of salivary and bacterial contamination of the root canal. If the tooth happens to fracture in a vertical plane, the prognosis is poor and the tooth may have to be extracted (Fig. 9). In the case of multirooted teeth, it may be possible to section the tooth and remove one of the roots.
Pain as a result of instrumentation
The two conditions that may require emergency treatment during a course of root canal treatment are:
  acute apical periodontitis;   Phoenix abscess.

CRACKED TOOTH SYNDROME (POSTERIOR TEETH)

Crazing of the enamel surface is a common finding on teeth as a consequence of function, but on occasion it may indicate a cracked tooth. If the crack runs deep into dentine and is therefore a fracture, chewing may be painful. Initially, this may not be of sufficient intensity for the patient to seek treatment. However, once the fracture line communicates with the pulp, pulpitis will ensue. A quiescent period of several months may follow before any further symptoms develop. The patient may present with a whole range of bizarre symptoms, many of which are similar to those of irreversible pulpitis:

  Pain on chewing.   Sensitivity to hot and cold fluids.   Pain which is difficult to localize.   Pain referred along to the areas served by the

fifth cranial nerve.   Acute pulpal pain.   Alveolar abscess.

Diagnosis can be difficult and much depends on the plane of the fracture line and its site on the tooth. Radiographs are unlikely to reveal a fracture unless it runs in a buccolingual plane. A fibre-optic light is a useful aid as it will often reveal the position of the fracture. One diagnostic test is to ask the patient to bite on a piece of folded rubber dam. Care must be exercised as this test may extend the fracture line. The extent of the fracture line and its site will decide whether the tooth can be saved or not. If it is a vertical fracture, involves the root canal system and extends below the level of the alveolar crest, then the prognosis is poor and extraction is indicated (Fig. 8).

Root canal treatment

Once access and initial drainage have been achieved, a rubber dam should be applied to the tooth to complete the operation. Before any further instrumentation is carried out, the pulp chamber should be thoroughly irrigated with a solution of sodium hypochlorite to remove as much superficial organic and inorganic debris as possible. This in itself may bring considerable pain relief and will make subsequent instrumentation easier. Having debrided the canals to the best possible extent with frequent changes of irrigant, the canals should be dried with paper points and a dry sterile cotton wool pledget placed in the pulp chamber to prevent ingress of the temporary dressing. The access cavity is then sealed to prevent re-infection of the canals from the oral cavity. If complete debridement was not possible the patient must be recalled within 48 hours. At this time it will usually be possible to complete instrumentation and place a calcium hydroxide dressing in the canals.
The temptation to leave the tooth open to drain must be resisted at all costs.

Incision to establish drainage

Incision to establish drainage is the only surgical endodontic procedure which may be undertaken when acute inflammation is present. The principal indication is the presence of a collection of pus which points from a fluctuant abscess in the soft tissues. Establishing drainage to help bring the infection under control is essential, and should always be obtained through the root canal and soft tissues in preference to administering antibiotics alone. The
soft-tissue swelling should be examined to see if it is fluctuant. Where the swelling is pointing intra-orally, copious amounts of surface analgesia should be applied, for example ethyl chloride or topical lignocaine ointment. Regional anaesthesia may not be effective due to the presence of pus, and the administration of a local analgesic solution may spread the infection further into the tissues. Incise the swelling with a Bard Parker No. 11 or 15 scalpel blade, or aspirate, using a widebore needle and disposable syringe. It may be possible to aspirate the abscess via the root canal as well. The advantage of this technique is that the sample can be sent for bacteriological examination if required. It is not usually necessary to insert a drain, but if it is thought necessary then a piece of quarter-inch or half-inch selvedge gauze may be used. The same criteria apply when extra-oral drainage is indicated, and it may be possible to use the same technique of aspiration with a wide-bore needle and disposable syringe. However, if an extra-oral incision is considered necessary, as in Figure 7, it is wise to refer the patient to an oral surgeon for this particular procedure.

Acute periapical abscess

This condition develops from an acute periapical periodontitis. In the early stages, the difference between the two is not always clear. Radiographic changes range from a widening of the periodontal ligament space (Fig. 2),

to a welldefined area (Fig. 3). The typical symptoms of an acute periapical abscess are a pronounced soft-tissue swelling (Fig. 4)

and an exquisitely tender tooth. Extrusion from the socket will often cause the tooth to be mobile. Differential diagnosis of a suspected periapical swelling is important in case the cause is a lateral periodontal abscess. The diagnosis can be made by testing the vitality of the tooth. If it is vital, then the cause may well be periodontal in origin.
The immediate task is to relieve pressure by establishing drainage, and in the majority of cases this can be achieved by first opening up the pulp chamber, as seen in Figure 5. Initially, gaining access can be difficult because the tooth is often extremely tender. Gently grip the tooth and use a small, round, diamond bur in a turbine to reduce the trauma of the operation. Regional analgesia may be necessary, and inhalation sedation can prove invaluable. If drainage is not immediate it is permissible to explore the apical foramen with a very fine (size 08 or 10) file. The foramen should not be instrumented or enlarged, and if drainage does not result the procedure should not be persevered. As discussed in Part 7, the use of ultrasonically activated endodontic files may be particularly helpful in this situation for effectively flushing infected debris from the root canal system.
If a soft-tissue swelling is present and pointing intra-orally, then it may be incised to establish drainage as well. The presence of a cellulitis may result in little or no drainage. If a cellulitis is present, medical advice should be sought before any treatment is carried out (Fig. 6).

In irreversible pulpitis

There is often a history of spontaneous bouts of pain which may last from a few seconds up to several hours. When hot or cold fluids are applied, the pain elicited will be prolonged. In the later stages, heat will be more significant; cold may relieve the pain. Pain may radiate initially, but once the periodontal ligament has become involved, the patient will be able to locate the tooth. The tooth becomes tender to percussion once inflammation has spread to the periodontal ligament. A widened periodontal ligament may be seen on the radiographs in the later stages. Careful evaluation of a patient s dental history and of each test is important. Any one test on its own is an insufficient basis on which to make a diagnosis. Records and radiographs should first be checked for any relevant information such as deep caries, pinned restorations, and the appearance of the periodontal ligament space (Fig. 1).

Vitality tests can be misleading, as various factors have to be taken into account. For example, the response in an older person may differ from that in someone younger due to secondary dentine deposition and other atrophic changes in the pulp tissue. Electric pulp testing is simply an indication of the presence of vital nerve tissue in the root canal system only and not an indication of the state of health of the pulp tissue Once pulpal inflammation has spread to the periodontal ligament, the resulting inflammatory exudate may cause extrusion of the tooth, making it tender to bite on. This particular symptom, acute apical periodontitis, may be a consequence of occlusal trauma; the occlusion must therefore always be checked.
Ideally, the treatment for irreversible pulpitis is pulp extirpation followed by cleaning and preparation of the root canal system. If time does not permit this, then removal of pulp tissue from the pulp chamber and from the coronal part of the root canal is often effective. Irrigation of the pulp chamber using a solution of sodium hypochlorite before carrying out any instrumentation is important. (Sodium hypochlorite is usually sold as a 5% solution. This may be diluted with purified water BP to the operator s preference.) Sodium hypochlorite solution has proved to be one of the most effective disinfecting agents used in root canal treatment,
7,8
with different authors recommending strengths between 0.5 and 5.0%. The pulp chamber and root canals are dried, and a dry sterile cotton wool pledget placed in the pulp chamber with a temporary filling to seal the access cavity. Antiseptic solutions such as phenolic solutions or corticosteroid/ antibiotic preparations on cotton wool pledgets have been advocated, but their effectiveness is of doubtful value. Corticosteroid dressings should be used sparingly as there is evidence that suppression of an inflammatory response by steroids allows bacteria to enter the bloodstream with ease.

This is a particularly undesirable effect in patients who, for example, have a history of rheumatic fever. Studies have shown that provided the pulp chamber and the root canals have been cleansed and dried, medication of the pulp chamber and root canals is of little practical benefit. Paper points are used to dry the canals and under no circumstances should they be left in the canal, otherwise any fluid that enters the canal system will be absorbed and so provide an effective culture medium for any residual bacteria.
Difficulty with local analgesia is a common problem with an acutely inflamed pulp. In
Fig. 3    to a large, well-defined area of radiolucency.
addition to standard techniques, supplementary analgesia can be obtained with the following:
1 Additional infiltration anaesthesia, such as long-buccal, lingual and palatal.
2 Intraligamental (intra-osseous) injection. 3 True intra-osseous injection. 4 Intrapulpal analgesia. 5 Inhalational sedation with local analgesia.
Should these techniques give only moderate success, it is advisable to dress the pulp to allow the inflammation to subside and to postpone pulp extirpation. A corticosteroid/antibiotic preparation with a zinc oxide/eugenol temporary restoration will provide an effective, shortterm dressing.
Continuation of pain following pulp extirpation may be due to one of the following causes.
1 The temporary filling is high.
2 Infected pulp tissue is present in the canal.
3 Some of the canal contents have been
extruded through the apex.
4 Overinstrumentation of the apex or perfora-
tion of the canal wall.
5 An extra canal may be present which has not
been cleaned. If the problem is not found to be occlusal,
whatever the cause the remedy is to irrigate the pulp chamber and root canal system again with sodium hypochlorite solution and perhaps gently instrument, then dry and redress the tooth as before.Once pulpal inflammation has spread to the periodontal ligament, the resulting inflammatory exudate may cause extrusion of the tooth, making it tender to bite on. This particular symptom, acute apical periodontitis, may be a consequence of occlusal trauma; the occlusion must therefore always be checked.
Ideally, the treatment for irreversible pulpitis is pulp extirpation followed by cleaning and preparation of the root canal system. If time does not permit this, then removal of pulp tissue from the pulp chamber and from the coronal part of the root canal is often effective. Irrigation of the pulp chamber using a solution of sodium hypochlorite before carrying out any instrumentation is important. (Sodium hypochlorite is usually sold as a 5% solution. This may be diluted with purified water BP to the operator s preference.) Sodium hypochlorite solution has proved to be one of the most effective disinfecting agents used in root canal treatment, 7,8 with different authors recommending strengths between 0.5 and 5.0%. The pulp chamber and root canals are dried, and a dry sterile cotton wool pledget placed in the pulp chamber with a temporary filling to seal the access cavity. Antiseptic solutions such as phenolic solutions or corticosteroid/ antibiotic preparations on cotton wool pledgets have been advocated, but their effectiveness is of doubtful value. Corticosteroid dressings should be used sparingly as there is evidence that suppression of an inflammatory response by steroids allows bacteria to enter the bloodstream with ease.

Pulpal pain

The histological state of the pulp cannot be assessed clinically.
Nevertheless, the signs and symptoms associated with progressive pulpal and periapical disease can give a reasonable indication of the likely state of an inflamed pulp, that is whether it is reversibly or irreversibly damaged.

Irritation of the pulp causes inflammation, and the level of response will depend on the severity of the irritant. If it is mild, the inflammatory process may resolve in a similar fashion to that of other connective tissues; a layer of reparative dentine may be formed as protection from further injury. However, if the irritation is more severe, with extensive cellular destruction, further inflammatory changes involving the rest of the pulp will take place, which could eventually lead to total pulp necrosis.
There are features of pulpitis which can make the borderline between reversible and irreversible pulpitis difficult to determine clinically. In general, if the responses to several tests are exaggerated, then an irreversible state is possible.
The essential feature of a reversible pulpitis is that pain ceases as soon as the stimulus is removed, whether it is caused by hot or cold fluids, or sweet food. The teeth are not tender to percussion, except when occlusal trauma is a factor. Initially, one of the following treatment may be all that is necessary:
  Check the occlusion and remove nonworking facets.
  Place a sedative dressing in a cavity after removal of deep caries.
  Apply a fluoride varnish or a dentine bonding resin to sensitive dentine and prescribe a desensitizing toothpaste.
Should the symptoms persist and the level of pain increase in duration and intensity, then the pulpitis is likely to be irreversible. The patient may be unable to decide which tooth is causing the problem, since the pain is often referred to teeth in both the upper and lower jaw on the same side. In the early stages, the tooth may exhibit a prolonged reaction to both hot and cold fluids, but is not necessarily tender to percussion. When testing for sensitivity to percussion it is not necessary to tap the tooth with the handle of dental instrument. Gentle finger pressure will be more than sufficient to elicit a response, and much kinder to your patient.

BEFORE TREATMENT

Details of the patient s complaint should be considered together with the medical history. The following points are particularly relevant and are covered more fully in Part 2.
1. Where is the pain? 

2. When was the pain first noticed? 

3. Description of the pain. 

4. Under what circumstances does the pain
occur? 

5. Does anything relieve it? 

6. Any associated tenderness or swelling. 

7. Previous dental history:
a) recent treatment; 

b) periodontal treatment; 

c) any history of trauma to the teeth.
Particular note should be made of any disorders which may affect the differential diagnosis of dental pain, such as myofascial pain dysfunction syndrome (MPD), neurological disorders such as trigeminal neuralgia, vascular pain syndromes and maxillary sinus disorders.
Diagnostic aids

Endodontics: Part 3 Treatment of endodontic emergencies

ENDODONTICS 1. The modern concept ofroot canal treatment 2. Diagnosis and treatment
planning 3. Treatment of endodontic
emergencies 4. Morphology of the root
canal system 5. Basic instruments and
materials for root canal treatment
6. Rubber dam and access cavities
7. Preparing the root canal 8. Filling the root canal
system 9. Calcium hydroxide, root
resorption, endo-perio lesions
10. Endodontic treatment for children
11. Surgical endodontics 12. Endodontic  Problems

The aim of emergency endodontic treatment is to relieve pain and control any inflammation or infection that may be present. Although insufficient time may prevent ideal treatment from being carried out, the procedures followed should not prejudice any final treatment plan. It has been reported that nearly 90% of patients seeking emergency dental treatment have symptoms of pulpal or periapical disease.
1,2

CONTRA-INDICATIONS TO ROOT CANAL TREATMENT Part. 2

Both types of resorption may eventually lead topathological fracture of the tooth. Internal resorption ceases immediately the pulp is removed and, provided the tooth is sufficiently strong, it may be retained. Most forms of external resorption will continue (see Part 9) unless the defect can be repaired and made supragingival, or arrested with calcium hydroxide therapy.
Bizarre anatomy
Exceptionally curved roots (Fig. 13), dilacerated teeth, and congenital palatal grooves may all present considerable difficulties if root canal treatment is attempted. In addition, any unusual anatomical features related to the roots of the teeth should be noted as these may affect prognosis.
Re-root treatment
One problem which confronts the general dental practitioner is to decide whether an inadequate root treatment requires replacement (Fig. 14). The questions the operator should consider are given below.

1 Is there any evidence that the old root filling has failed?
• Symptoms from the tooth.   Radiolucent area is still present or has
increased in size.   Presence of sinus tract.
2 Does the crown of the tooth need restoring? 3 Is there any obvious fault with the present
root filling which could lead to failure? Practitioners should be particularly aware
of the prognosis of root canal re-treatments. As a rule of thumb, taking the average of the surveys reported in the endodontic literature (see Part 12) suggests a prognosis of 90–95% for an initial root canal treatment of a tooth with no radiographic evidence of a periradicular lesion. When such a lesion is present prognosis will fall to around 80–85%, and the longer the lesion has been present the more established will be the infection, treatment (ie removal of that infection from the entire root canal system) will be more difficult and the prognosis significantly lower. The average reported prognosis for re-treatment of a failed