Root canal dressing

INTRODUCTION

1. To prevent microorganisms which remain in the root canal system after preparation from proliferating and passing into the periapical tissues via the apical foramen and other pathways.

2. To seal the pulp chamber and root canal system from leakage via the coronal restoration in order to prevent passage of microorganisms and/or toxins along the root canal and into the periapical tissues via the apical foramen and other pathways.

3. To prevent percolation of periapical exudate and possibly microorganisms into the pulp space via the apical foramen and other pathways.

4. To prevent percolation of gingival exudate and microorganisms into the pulp space via lateral/furcation canals opening into the gingival sulcus or through exposed, patent dentinal tubules around the neck of the tooth.

The quality of the root canal filling depends on the complexity of the root canal system, the efficacy of canal preparation, the materials and techniques employed, and the skill and experience of the operator. Filling of the canal does not represent the end of root canal treatment, as restoration of the clinical crown to prevent leakage of fluids and oral microorganisms into the pulp space is critical to long-term success. 1 There is mounting evidence that the quality of the coronal seal affects the prognosis of root canal treatment. 2

Many materials and techniques have been used to fill root canals. 3 The current material of choice is gutta-percha combined with a sealer, because it is versatile and can be used in a variety of techniques.

Что означает лечение корневых каналов? Лечение корневых каналов ‒ это удаление пульпы, мягкой ткани в центре зуба. После извлечения поврежденной, зараженной или мертвой пульпы оставшееся пространство очищается, формируется и заполняется пломбировочным материалом. С помощью этой процедуры корневой канал герметизируется. Много лет назад зубы с поврежденной пульпой удалялись, но сегодня лечение корневых каналов позволяет их сохранить.

Наиболее распространенными причинами повреждения или отмирания пульпы являются:

Если не лечить зараженную или мертвую пульпу, на верхушке корня в челюстной кости может образоваться гной, формирующий абсцесс. Абсцесс способен привести к разрушению кости вокруг зуба и вызвать боль.

Как производится лечение корневых каналов? Лечение корневых каналов состоит из нескольких этапов, которые проводятся за несколько посещений, в зависимости от ситуации. Вот они:

Сколько времени прослужит восстановленный зуб? При надлежащем уходе восстановленный зуб прослужит вам всю жизнь. Вылеченные зубы могут разрушаться, поэтому очень важно соблюдать правильную гигиену полости рта и регулярно посещать стоматолога, чтобы предотвратить дальнейшие проблемы.

Ввиду отсутствия пульпы, зуб, который был подвержен лечению корневых каналов, становится более хрупким. Это важно осознавать при принятии решения об установлении коронки или пломбировании зуба после лечения корневых каналов.

Самым надежным способом определения успеха выполненного лечения является сравнение новых рентгеновских снимков со старыми. Они покажут, удалось ли восстановить кость.

Root canal treatment (endodontics) is a dental procedure used to treat infection at the centre of a tooth.

Root canal treatment is not painful and can save a tooth that might otherwise have to be removed completely.

Why it’s needed

The infection at the centre of a tooth (the root canal) is caused by bacteria that live in the mouth and invade the tooth.

This can happen after:

Tooth structure

A tooth is made up of 2 parts. The crown is the top part of the tooth that’s visible in the mouth.

The root extends into the bone of the jaw, anchoring the tooth in position.

Teeth also consist of:

The root canal system contains the dental pulp and extends from the crown of the tooth to the end of the root.

A single tooth can have more than 1 root canal.

When root canal treatment is needed

Root canal treatment is needed when dental X-rays show that the pulp has been damaged by a bacterial infection.

The pulp may become inflamed if it’s infected by bacteria, allowing the bacteria to multiply and spread.

The symptoms of a pulp infection include:

As the infection progresses, these symptoms often disappear as the pulp dies.

Your tooth then appears to have healed, but the infection has in fact spread through the root canal system.

You eventually get further symptoms such as:

It’s important to see your dentist if you develop toothache. If your tooth is infected, the pulp cannot heal by itself.

Leaving the infected tooth in your mouth may make it worse.

There may also be less chance of the root canal treatment working if the infection within your tooth becomes established.

Antibiotics, a medicine to treat bacterial infections, are not effective in treating root canal infections. They can though help to treat infection that spreads beyond the root and causes swelling.

How root canal treatment is done

To treat the infection in the root canal, the bacteria need to be removed.

This can be done by either:

But removing the tooth is not usually recommended as it’s better to keep as many of your natural teeth as possible.

Before having root canal treatment, you’ll usually be given a local anaesthetic.

This means the procedure should be painless and no more unpleasant than having a filling.

After the bacteria have been removed, the root canal is filled and the tooth sealed with a filling or crown.

In most cases the inflamed tissue near the tooth will heal naturally.

Root canal treatment is usually successful. In about 9 out of 10 cases a tooth can survive for up to 10 years after root canal treatment.

Find out how root canal treatment is done

Recovering from root canal treatment

It’s important to look after your teeth when recovering from root canal treatment.

You should avoid biting on hard foods until your treatment is complete.

After your final treatment, your restored tooth should no longer be painful, although it may feel sore for a few days.

You can take over-the-counter painkillers, such as paracetamol or ibuprofen, to relieve any discomfort.

Return to your dentist if you still have pain or swelling after using painkillers.

In most cases it’s possible to prevent the need for further root canal treatment by:

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Page last reviewed: 27 January 2022
Next review due: 27 January 2025

Root canal treatment is carried out by your dentist over 2 or more appointments.

Unless you’re entitled to free NHS dental treatment, you’ll have to pay for root canal treatment.

Read about NHS dental charges and how to get help with dental costs.

If the work is particularly complex, your dentist may refer you to a specialist in root canal treatment, known as an endodontist.

All registered dental specialists in the UK are listed on the General Dental Council (GDC) website.

Preparing for root canal treatment

Before having root canal treatment, your dentist may take a series of X-rays of the affected tooth.

This allows them to build up a clear picture of the root canal and assess the extent of any damage.

Root canal treatment is usually carried out under local anaesthetic, a painkilling medicine that numbs your infected tooth and the gum around it.

In some cases where the tooth has died and is no longer sensitive, it may not be necessary to use a local anaesthetic.

Removing the pulp

Your dentist will place a rubber sheet (dam) around the tooth to ensure it’s dry during treatment.

The dam also prevents you swallowing or breathing in any chemicals the dentist uses.

Your dentist will use a drill to open your tooth through the crown, the flat part at the top, to access the soft tissue at the centre of the tooth (pulp). They’ll then remove any infected pulp that remains.

If you have a dental abscess, which is a pus-filled swelling, your dentist will be able to drain it at the same time.

Cleaning and filling the root canal

After the pulp has been removed, your dentist will clean and enlarge the root canal.

The root canal is usually very narrow, which makes it difficult to fill.

Your dentist will use a series of small files to enlarge the canals and make them a regular shape so they can be filled.

This part of the treatment may take several hours, and may need to be carried out over a number of visits.

Your front incisor and canine teeth (biting teeth) usually have a single root containing 1 root canal.

The premolars and back molar teeth (chewing teeth) have 2 or 3 roots, each containing either 1 or 2 root canals.

The more roots a tooth has, the longer the treatment will take to complete.

If the treatment needs to be carried out over several sessions, your dentist may put a small amount of medicine in the cleaned canal in between visits to kill any remaining bacteria.

The tooth will then be sealed using a temporary filling.

If you have symptoms from the infection, such as a raised temperature or large swelling, you may be given antibiotics to help manage and prevent further infection.

Sealing and fixing the tooth

At your next visit, the temporary filling and medicine within the tooth is removed and the root canal filling will be inserted.

This, along with a filling, seals the tooth and prevents reinfection.

Root-filled teeth are more likely to break than healthy unrestored teeth, so your dentist may suggest placing a crown on the tooth to protect it.

In some cases a root-filled tooth may darken, particularly if it’s died as a result of injury like a knock to the tooth.

There are several ways your dentist can treat discolouration, such as whitening the tooth using chemicals.

Adding a crown

A crown is a cap that completely covers a real tooth. It might be necessary to use a crown after root canal treatment to prevent the tooth fracturing.

Crowns can be made from:

The dentist will use a drill to reduce the size of your tooth and use the crown to replace what’s removed.

A mould of your tooth will be taken to ensure the crown is the right shape and size, and fits your tooth accurately.

When fitting the crown, cement will be used to glue the crown to the trimmed-down tooth.

If there’s only a small amount of tooth left after the root canal treatment, a post can be cemented in the root canal and used to help keep the crown in place.

Find out more about what NHS dental fillings and crowns are made of

How successful is root canal treatment?

Root canal treatment is usually successful at saving the tooth and clearing the infection.

Around 9 out of 10 root-treated teeth survive for 8 to 10 years.

Having a crown fitted to the tooth after root canal treatment is important for improving tooth survival rates.

If you keep your teeth clean, your treated tooth should survive for a long time.

The survival of your tooth depends on a number of factors, including:

But if an infection does return, the root canal treatment can be repeated.

Or if treatment has already been carried out to a high standard and the infection remains, a small operation to remove the root tip (an apicoectomy) may be carried out to treat the infection.

Root Canal Filling Materials and Techniques

1 Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK

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2 Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand

A sealer (cement/paste/resin) only.
A sealer and a single cone of a rigid or semirigid core material.
A sealer coating combined with cold compaction of core materials.
A sealer coating combined with warm compaction of core materials.
A sealer coating combined with carrier‐based core materials. Newer materials focus on the deficiencies of the key groups of sealers and of gutta‐percha, whilst improved placement techniques have provided time and cost savings. Some improvements are aimed at replacing gutta‐percha, often accompanied by newer sealers. Newer cores are produced from materials designed to match the size and taper of the canal preparation instruments, such that single‐cone obturation is now considered acceptable.Root canal obturation aims to:Seal the pulp chamber and canal system from coronal microleakage.
Prevent remaining microorganisms from proliferating.
Stop microorganisms entering the pulp space through the apical foramen and other pathways (lateral/furcation canals opening into the gingival sulcus, exposed and open dentinal tubules around the tooth).

6.2 Root Canal Obturation Materials () sealers: e.g. Tubli‐Seal and Pulp Canal Sealer (Kerr Endodontics, Brea, CA, USA) and Roth’s Sealer (Roth International, Chicago, IL, USA).
Calcium hydroxide sealers: e.g. Sealapex (Kerr Endodontics) and Apexit and Apexit Plus (Ivoclar Vivadent, Liechtenstein, Germany).
Glass ionomer sealers: e.g. Ketac Endo (3M ESPE, Seefeld, Germany).
Resin sealers: e.g. AH 26, AH Plus (Dentsply De Trey GmbH, Konstanz, Germany), SimpliSeal (Kerr Endodontics), 2Seal (VDW GmbH, Munich, Germany), and Obturys (Itena, Paris, France).
Silicone‐based sealers: e.g. Roekoseal (Coltène/Whaledent, Langenau, Germany).
HCSC sealers: e.g. BioRoot RCS (Septodont, Saint‐Maur‐des Fosses, France), EndoSequence BC Sealer (Brasseler, Savannah, GA, USA), and Totalfill BC sealer (FKG Dentaire, La Chaux‐de‐Fonds, Switzerland). 6.2.1.1 Zinc Oxide‐Eugenol Sealers Penetration of a sealer, dyed with Sudan Black B, at different levels of filled roots: absent (top left), inner third (top right), middle third (lower left), and outer third (lower right).Source: Humza Ahmed.6.2.1.2 Calcium Hydroxide Sealers6.2.1.3 Glass Ionomer Sealers6.2.1.4 Resin Sealers Confocal microscope image (×10) of penetration of AH Plus (Dentsply De Trey GmbH) into dentinal tubules.Source: Assil Russell.6.2.1.5 Silicone SealersGuttaFlow and GuttaFlow2 (Coltène/Whaledent) consist of a small amount of gutta‐percha in RoekoSeal in a capsulated form. The material is injected into a canal, and then a single gutta‐percha master cone is then placed.6.2.1.6 HCSC Sealers6.2.1.6.1 Type 2 HCSC Sealers6.2.1.6.2 Type 3 HCSC Sealers Confocal microscope image (×10) of penetration of MTA Fillapex (Angelus) sealer into dentinal tubules.Source: Assil Russell.6.2.1.6.3 Type 4 and Type 5 HCSC Sealers6.2.1.7 Other Sealer TypesUse of chloroform‐based sealers such as Rosin‐chloroform, Chloropercha (Tanrac Ltd, Gavle, Sweden), and Kloropercha has declined due to concerns about their toxicity. Formaldehyde‐containing sealers are no longer recommended because they contain substantial amounts of paraformaldehyde and are considered unsafe.6.2.2 Core Materials6.2.2.1 Silver Points Mandibular left first molar root filled with silver points.Source: Bun San Chong, Nicholas Chandler. Gutta‐percha cones of different sizes and tapers.Source: Bun San Chong, Nicholas Chandler.6.2.2.2 Acrylic Points‘PD’ Acrylic Points (Produits Dentaires SA, Vevey, Switzerland) are colour‐coded and radiopaque. They are made of a methyl methacrylate polymer, bismuth oxide, zinc oxide, and a cadmium‐free colouring agent. As a rigid core material, they are meant to offer all of the advantages and none of the disdavantages of silver points, and they are promoted as being removable with burs, solvents, or essential oils if retreatment is necessary.6.2.2.3 Gutta‐PerchaOver 2000 plant species produce natural rubber latex (), the main constituent of which is poly(cis‐1,4 isoprene). The main constituent of endodontic gutta‐percha, on the other hand, is 19–22% poly(trans‐1,4 isoprene); other constituents added to it for endodontic use include zinc oxide (59–75%) and various waxes, colouring agents, antioxidants, and metal salts as radiopacifiers. The proportions vary from brand to brand, so there are considerable variations in stiffness, brittleness, and tensile strength. To facilitate fit, gutta‐percha cones are available in different sizes and tapers (Figure 6.5).Gutta‐percha has many advantages, being:inert;
dimensionally stable after treatment;
nonallergenic;
antibacterial;
nonstaining to dentine;
radiopaque;
compactable;
softenable by heat;
softenable by organic solvents; and
easily removable from the canal, when necessary. It also has some disadvantages (Figure 6.6), being:nonrigid;
nonadherent to dentine; and
capable of being stretched. Suboptimal, poorly condensed gutta‐percha root filling in a maxillary left central incisor.Source: Bun San Chong, Nicholas Chandler.6.2.2.3.1 Coated Cones6.2.2.3.2 Chlorhexidine‐Impregnated Gutta‐Percha Points6.2.2.3.3 Gutta‐Percha Points Impregnated with Metronidazole6.2.2.3.4 Gutta‐Percha Allergy

6.3 Root Filling TechniquesSince gutta‐percha remains the most commonly used core root filling material, the main focus of this section will be on techniques utilizing gutta‐percha. Extrusion of sealer from the mesiolingual canal of a mandibular right first molar.Source: David Yong. Root canal sealer extruded through to reveal a lateral canal in a maxillary right central incisor, explaining the adjacent bone loss.Source: Finn Gilroy.6.3.1 Cold Gutta‐Percha Condensation Techniques6.3.1.1 Lateral CondensationOnly gold members can continue reading. Log In or Register to continue

CANAL ANATOMY

Pulp anatomy is complex with many root canals having apical deltas, lateral canals and other aberrations; accessory canals, fins, and anastomoses are not uncommon, especially in posterior teeth. These, together with the consequences of physiological and pathological dentine deposition and procedural problems during canal preparation, present challenges. The inherent anatomy of the root canal system has a major influence on the techniques used to fill canals and on the quality of the final result.

Calcium hydroxide sealers

Calcium hydroxide-based sealers have been developed on the assumption that they preserve the vitality of the pulp stump and stimulate healing and hard tissue formation at the apical wound. Laboratory research has demonstrated their sealing ability to be similar to zinc oxide-eugenol sealers25 although it remains to be seen whether during long-term exposure to tissue fluids they maintain their integrity, since calcium hydroxide is soluble and may leach out and weaken the remaining cement. 24

Commercial products include Sealapex (SybronEndo), a calcium hydroxide-containing polymeric resin, Apexit Plus (Ivoclar Vivadent, Schaan, Liechtenstein) and epoxy-based Acroseal (Septodont, Saint-Maur Cedex, France).

The aims of preparation are to clean and shape the root canal system. Access and preparation have been discussed in Chapters 4 and 7 respectively. It should be emphasized that time and care spent during access and canal preparation will facilitate root canal filling. As well as removing microorganisms and debris from the root canal system, preparation produces the desired canal shape to receive the root filling. Cleaning of the canal may be achieved with irrigants and minimal removal of dentine from canal walls. However, achieving the correct canal shape invariably requires additional effort to create the flowing, flared preparation demanded by most root canal filling techniques. Inappropriate access and root canal preparation can leave microorganisms, pulpal remnants and dentine debris within the root canal system. These will, invariably, affect proper adaptation of the root filling to the canal walls, and the physical properties of the sealer will determine the effectiveness of the seal produced. Furthermore, creation of an inappropriate canal shape will make it difficult to introduce root filling materials along the length of the canal, resulting in a poorly condensed filling with voids. Thus, the ability to fill canals predictably is, significantly, dependent on the adequacy of access and the quality of the root canal preparation.

The method of root canal filling will be dictated by the preparation technique and the shaping objectives. Some operators prefer to create an apical stop at the dentine-cementum junction where a natural apical constriction is believed to exist; in this way instrumentation does not extend beyond the apical foramen. 4 With this shape of canal, the filling technique of choice is cold lateral condensation of gutta-percha. Other operators create a continuously tapering canal shape where the smallest diameter is at the foramen. 5 With this shape, a variety of warm gutta-percha techniques are more appropriate; the lack of an apical stop will predispose the master gutta-percha cone, used in lateral condensation, to being distorted and pushed beyond the foramen when a spreader is introduced.

A root canal sealer (cement) is used in combination with the core root canal filling material, e.g. gutta-percha. The primary role of the sealer is to obliterate the irregularities between the root canal wall and the core material. Almost all of today’s root canal filling techniques use a sealer to enhance the seal of the root canal filling. 15

• cementing (luting, binding) the core material to the canal

• filling the discrepancies between the root canal walls and core material

• acting as an antimicrobial agent

• acting as a marker for accessory canals, resorptive defects, root fractures and other spaces into which the main core material may not penetrate.

The requirements and characteristics of an ideal sealer are: 16

• non-irritating to periapical tissues

• insoluble in tissue fluids

• hermetic sealing ability

• sticky and good adhesion to canal wall when set

• non-staining to dentine

• readily removable if necessary.

No current material satisfies all these requirements but many work well in clinical practice. As well as providing a satisfactory seal, it must be well tolerated by the periapical tissues and be relatively easy to handle. Sealers are toxic when freshly prepared; 17 however, their toxicity is reduced substantially after setting. 18 Thus, although sealers produce varying degrees of periapical inflammation, it is normally only temporary and depending on composition, it does not appear to prevent tissue healing. 19

Most sealers are absorbed to some extent when exposed to tissue fluid, 20 so the volume of sealer must be kept to a minimum with the core material forming the bulk of the root filling. The core material should force the sealer into inaccessible areas and into irregularities along the root canal walls. Excess sealer should ideally flow backwards and into the access cavity, but some gutta-percha techniques tend to force sealer apically and laterally via the foramen and accessory canals. 21,22 The passage of sealer into the periapical tissues is not encouraged. However, there is equivocal evidence that it will reduce the success rate of treatment provided that canal preparation and filling have been performed with care. Clinical experience suggests that most excess sealer in the periapical region is absorbed with time but large volumes of extruded sealer must be avoided.

Sealers in use today can be divided into five groups based on their constituents:

• zinc oxide–eugenol sealers

• calcium hydroxide sealers

• silicone-based sealers.

Canal filling with gutta-percha

The objective of root canal filling is to completely fill the canal system in an attempt to seal the canal from leakage apically and coronally. Gutta-percha is versatile and can be used in a variety of techniques, but a sealer is always necessary to cement the material to the canal wall and to fill minor irregularities.

Methods for filling canals using gutta-percha can, broadly, be divided into three main groups:

• heat-softened gutta-percha

• solvent-softened gutta-percha.

Silicone-based sealers

RoekoSeal (Coltène/Whaledent, Cuyahoga Falls, OH, USA) is a polydimethylsiloxane-based sealer. The manufacturer stated that this silicone-based sealer expands slightly on setting (0.2%) and is highly radiopaque; the claimed advantages include good sealing ability33 and excellent biocompatibility. 34 However, in a histopathological study on periapical healing in dog’s teeth, no differences were noted between RoekoSeal and AH Plus. 35

GuttaFlow (Coltène/Whaledent), introduced in 2004, is a modification of RoekoSeal. GuttaFlow contains particles of gutta-percha less than 30 µm in size and and also expands slightly (0.2%) on curing according to the manufacturer. The material is considered to be almost insoluble. It is used with a single master gutta-percha cone, without mechanical compaction, although lateral or vertical condensation are acceptable. Its flow is significantly better into lateral grooves and depressions in the apical regions of root canals than lateral condensation or warm compaction with AH 26 sealer. 36 Its sealing qualities are similar to lateral compaction or the System B technique with AH 26. 37 All traces of irrigants must be thoroughly rinsed from the canal with water or isopropyl alcohol prior to introducing the material. GuttaFlow has a working time of 15 minutes and a setting time of about 30 minutes; GuttaFlow FAST has a 5 minute working time and a 10 minute set. A potential concern is extrusion of material beyond the apex36,37 although its cytotoxicity is lower than some other sealers.

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Zinc oxide-eugenol sealers

Most of the zinc oxide-eugenol sealers are based on Grossman’s formula. 23 Commercial products include Tubli-Seal (SybronEndo, Orange, CA, USA), Pulp Canal Sealer (SybronEndo) and Roth Sealer (Roth International Ltd, Chicago, IL, USA). Modified formulations with extended working times are also available.

Once set, zinc oxide-eugenol sealers are relatively weak and porous, and are susceptible to decomposition in tissue fluids, particularly when extruded into the periapical tissues. 24 All zinc oxide-eugenol cements are cytotoxic and the cellular response may last longer than those produced by other materials. 18 However, these problems are not usually apparent clinically, and zinc oxide-eugenol materials are, probably, the most commonly used sealers. The various zinc oxide-eugenol sealers have a range of setting times and flow characteristics so the choice of formulation is dependent on the case. Difficult canals that need some time to fill require a sealer with an extended working time. If heat is applied during root canal filling, its influence on the setting time of sealers should also be taken into account.

SMEAR LAYER

The smear layer, comprising both organic and inorganic components, is found on the root canal walls after endodontic instrumentation.38.39. and 40. It is composed largely of particulate dentine debris created by endodontic instruments during root canal preparation but also contains pulpal remnants and microorganisms. With further instrumentation the material is forced against the canal walls forming a friable and loosely adherent layer. The smear layer is typically 1–2 µm thick, although it can also be found within the dentinal tubules for up to 40 µm. 38

The smear layer has received much attention, not only because it may harbour microorganisms already in the canal but it may create an avenue for leakage of microorganisms and act as a substrate for microbial proliferation. It may also be broken down by bacterial action41 to provide a pathway for leakage. In addition, the smear layer has the potential to interfere with the adaptation of sealer against the root canal walls and prevent tubular penetration of sealer, thereby increasing the likelihood of leakage. 1,42 Indeed, it has been shown that most leakage occurs between the sealer and the wall of the root canal. 43

Smear layer removal prior to filling would appear to be desirable as it would eliminate microorganisms and allow for better adaptation of sealer. However, this procedure has been questioned since opening the tubules might increase the diffusion of potentially irritant root filling materials through the tubules to the root surface, 44 allow microorganisms trapped in the tubules to escape45 or to proliferate within the tubules and, potentially, increase leakage. 46 Nevertheless, the present consensus is that the removal of the smear layer is beneficial and desirable, particularly when treating infected teeth.

In laboratory studies, a number of methods have been shown to be effective in removing the smear layer. 40 The key method involves 17% EDTA as a chelating agent together with sodium hypochlorite to dissolve the organic component. 42

Cold gutta-percha techniques

Cold gutta-percha techniques are relatively simple to master as they are not complicated by the need to soften the material with heat or solvents, hence they do not require expensive devices or equipment. However, cold gutta-percha cannot be effectively compacted into all the irregularities in a root canal system so this is the role of the sealer. Lateral condensation is the most popular method of root filling with cold gutta-percha.

Lateral condensation

With the advent of the standardized preparation technique, 48 the method of filling root canals with a single, full length gutta-percha cone and sealer became popular. The concept was simple and attractive; the root canal was prepared to a round cross-sectional shape of a standard size with reamers and filled with a gutta-percha cone of the same diameter. Unfortunately, a round canal shape was rarely achieved, especially in curved roots, 49,50 and the single cone required large amounts of sealer to fill the intervening gaps resulting in increased leakage. 51 It was also clear that discrepancies in size52 and taper between gutta-percha cones and equivalent numbered instruments were prevalent. While many clinicians appreciated these problems and adopted other filling techniques, others continued to fill canals using this method (Fig. 9.1).

Current canal preparation techniques produce a flared canal with a flowing conical shape and cannot be filled adequately with a single 0.02 taper gutta-percha cone. Gutta-percha cones with ISO standardized tip sizes but with varying tapers, e.g. 0.04 or 0.06 tapers are available (Fig. 9.2). These cones with increased taper can fill funnel-shaped canals more effectively because they are more likely to correspond to the canal shape created by instruments with similar taper. In a laboratory study on curved canals, a single tapered cone technique has been found to be comparable with lateral condensation in terms of the amount of gutta-percha occupying the root canal space; the technique is also faster than lateral condensation. 53 A clinical example shows radiographically acceptable results (Fig. 9.3).

A spreader is inserted alongside the master cone to improve its adaptation at the terminus of the preparation and to create the space for the accessory gutta-percha cones. When inserted to within 1 mm of the terminus to condense the master cone apically54 and laterally, the result will be considerably less leakage than if the spreader had only entered part of the way into the canal. 55 The need to advance the spreader well into the root canal is one of the main reasons why canals are flared. A narrow, parallel shape will not allow the spreader to influence the adaptation of the apical region of the master gutta-percha cone. Narrow canal preparations also risk removing the master gutta-percha cone when withdrawing the spreader, as it might pierce the cone instead of condensing the material.

The requirements for successful lateral condensation are:

• a flared canal preparation with an apical stop

• a well-fitting master gutta-percha cone

• speader/s of the appropriate size and shape

• accessory cones which match the dimensions of the spreader/s

The master gutta-percha cone must fit to the full length of the preparation, be tight at the end-point of the canal preparation (ideally present some resistance to withdrawal or ‘tug-back’), and it must not be able to pass through the foramen.

The size of the master gutta-percha cone should correspond to the master apical file used to prepare the apical stop. The selected gutta-percha cone is held with tweezers at the correct length, equivalent to the working distance and then inserted into the canal. Ideally, the gutta-percha cone should:

• pass down to the full working distance

• be impossible to push beyond this depth or through the foramen

• fit tightly giving some resistance to withdrawal (tug-back).

The tweezers are squeezed slightly to mark the gutta-percha cone and the tweezers removed, leaving the cone in situ (Fig. 9.7). A radiograph may be taken to confirm the correct depth in relation to the terminus of the preparation and the radiographic apex. If the canal length is correctly estimated, the gutta-percha cone should be at the right depth and position, and the canal filling procedure can proceed. However, a number of problems can occur, either as a result of technical difficulties during canal preparation or because of size discrepancies in the gutta-percha cones and/or instruments. Most of these problems can be easily addressed but they require some thought to ensure that the exact problem is identified.

Gutta-percha cone reaches the working distance but is loose

This may occur for a number of reasons.

• The gutta-percha cone was smaller than expected. During manufacture, a tolerance of ±0.05 mm is allowed at d1 so that it is possible for a gutta-percha cone with the correct nominal size to be smaller than the equivalent master apical file size and prepared canal width. The solution may be to remove 1 mm increments from the tip of the cone with a sharp scalpel blade to increase the tip diameter, or to select a larger gutta-percha cone.

• The end-point of preparation was wider than expected. Just as the size of cones may vary so can the size of files. The tolerance of files can be ±0.02 mm at d1 so it is possible for the canal to be wider than anticipated. The solution to this problem is the same as that described above.

The canal can become wider than expected through inappropriate choice of instruments and/or preparation technique leading to the excessive removal of tooth tissue from the outer wall of the canal apically. If this is the problem, then either a selection of gutta-percha cones can be tried-in until one is found to fit or an alternative filling method chosen.

Gutta-percha cone passes beyond working distance or through foramen

This can occur when the apical stop is inadequate or when the gutta-percha cone is too small. If the stop is not sufficiently definite, then the cone will pass more deeply and through the foramen. The solution is either to reprepare the canal with larger instruments until a distinct stop is created at the end-point of preparation, or to remove 1 mm increments from the gutta-percha cone until its diameter is sufficient to bind in the canal at the working distance.

Gutta-percha cone does not reach the working distance

This is the most common problem with positioning of the master cone and there are a number of reasons:

• The gutta-percha cone was larger than expected. Just as gutta-percha cones can be smaller than the nominal size and appear loose, they can also be larger. Thus, if a cone is a short distance (<2 mm) away from the end-point of the preparation it may be possible to try a selection of cones of the same diameter to find one that fits.

• The canal was not widened sufficiently at the end-point or the canal taper was too narrow. This is a common problem and occurs when the master apical file is either smaller than its nominal size or, more likely, that it was not used sufficiently to widen the canal fully. In this way, either the apical dimensions of the canal are too small or the curved region of the canal is too narrow and causes the gutta-percha cone to bind. It is essential that the master apical file be manipulated until it can pass down freely to the termination of the preparation without the application of any undue force. With insufficient preparation it may be possible to force the master apical file to the working distance, but the gutta-percha cone will bind and buckle before reaching the expected length. The solution to this problem is to select a new file and reinstrument the canal to the working length until the file is loose. Increasing the taper along the length of the canal may also be necessary.

Once the master gutta-percha cone has been chosen, it is important to select and try-in the spreader to ensure that it can pass down the canal to within 1 mm of the termination of the preparation. Spreaders should be precurved in curved canals and a silicone stop used to mark the depth of insertion. Nickel-titanium spreaders, which are more flexible, are also available. To reduce the risk of root fracture due to excessive condensation pressures, finger rather than hand-held spreaders may be used.

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Spreaders come in non-standardized or standardized 0.02 tapers, the same as for most hand files. Non-standardized spreaders have relatively small diameters at the tip but a range of tapers ranging from extra-fine through fine, medium to large; some manufacturers use letters rather than words to denote the degree of taper, e.g. A, B, C, D. Spreaders with a standardized taper are manufactured in a range of ISO diameters.

The choice of spreader design, that is, with non-standardized or standardized taper, and the type of accessory cones are determined by operator preference. When non-standardized spreaders are used the cones should also be non-standardized. However, standardized spreaders require standardized accessory gutta-percha cones. In this way, the cone will fill the space created by the corresponding spreader. The space created by a standardized spreader cannot be filled adequately with a non-standardized cone. It is also beneficial to use instruments and materials from the same manufacturer to ensure accurate sizing.

The size of the spreader, and thus cones, are determined by the size of the canal. Large canals with a substantial taper are more efficiently filled with larger taper cones, whilst smaller canals with narrower tapers should be filled with finer cones. On most occasions, an extra-fine or fine spreader is required along with matching accessory gutta-percha cones.

Completion of lateral condensation

1. The master gutta-percha cone, spreader, accessory gutta-percha cones and sealer should be organized to ensure they can be handled efficiently.

2. The canal should be dried thoroughly with paper points.

3. The sealer should be mixed and smeared onto the canal wall using either a hand file rotated anticlockwise, by coating a paper point and inserting it into the canal, or by coating the master cone itself. Large volumes of sealer introduced with motor driven devices are not necessary and may be hazardous.

4. The master cone should be ‘buttered’ lightly with sealer and then inserted immediately to the full working length.

5. The spreader is then placed alongside the gutta-percha cone and pushed apically with controlled force until it reaches the appropriate depth, 1 mm from the end-point of preparation. These forces can be considerable, 57 and the direction of force should be apical with no lateral action, which could risk root fracture. Apical pressure is applied in a constant manner for 10 to 20 seconds to compact the gutta-percha in an apical and lateral direction. In curved canals, the spreader may be precurved and applied either lateral to, or on the outer aspect of the master gutta-percha cone. It should not be applied along the inner aspect of the curve as it could pierce the cone and drag it out when the spreader is removed.

6. The first accessory gutta-percha cone is inserted into the space created by the spreader.

7. The spreader is then cleaned and reinserted immediately into the canal. It should not go down to the full working length.

8. The second accessory gutta-percha cone is inserted into the space created.

9. The sequence of spreader application and cone insertion continues until the canal is full, with the number of accessory cones required varying from canal to canal (Fig. 9.8). If a post-retained restoration is planned, if desired, lateral condensation can cease when the apical 5–6 mm have been filled.

10. If the final coronal restoration is not post-retained, the excess gutta-percha emerging from the canal entrance should be removed with a hot instrument and condensed vertically with a plugger to promote a satisfactory seal. The gutta-percha should be reduced to below the gingival level, particularly in anterior teeth, in order to maintain the translucency of the crown and to prevent the possibility of sealer staining the dentine. 58 In all cases, having the root filling confined to well within the root and protected by suitable restorations will reduce the risk of microleakage.

When a post-retained restoration is planned gutta-percha can be removed immediately but carefully, leaving approximately 4–5 mm of apical root filling undisturbed. 59,60 Post space preparation at this stage is advantageous as the operator is very conscious of the anatomy and length of the canal. A rubber dam is already in place and the required length of post is easily assessed.

Lateral condensation is relatively simple to carry out, rapid, and has been used for many years with considerable success, even in quite demanding cases (Fig. 9.9). However, since it is impossible for cold gutta-percha to flow into all the irregularities in the root canal system, parts of the canal must either remain unfilled61 or be filled only with sealer. The importance of cleaning anatomical irregularities in oval canals has been emphasized. Otherwise, they remain packed with debris and reduce the quality of the root filling; 61,62 canals which are this shape present a challenge for most obturation methods. 63

Innovative means of obturation using gutta-percha aimed at reducing the time involved with lateral condensation include SimpliFill (Discus Dental, Culver City, CA, USA). A section of gutta-percha or Resilon (see later) is held at the end of the SimpliFill disposable delivery device, which is inserted into the canal to the desired depth. An apical plug of root filling is left inside the canal by twisting, to free the delivery device, which is then withdrawn; the remainder of the canal is then back-filled if required.

The perceived deficiencies of lateral condensation have resulted in the development of techniques in which gutta-percha is softened by heat or solvents so that the core material can be condensed into anatomical irregularities. 62 Some of these techniques are ‘hybrids’ which use the controllability and safety of cold lateral condensation in the apical region and heat-softening to fill the coronal two-thirds more quickly. Other techniques involve heat to soften the whole length of gutta-percha in the root canal.

Heat-softened gutta-percha techniques

For decades the only technique that used heat-softened gutta-percha was warm vertical condensation64 but a number of innovative methods for warming and condensing gutta-percha are now available. In some, cold gutta-percha is placed in the canal and warmed in situ; these can be referred to as intracanal heating techniques. Others rely on warming gutta-percha outside and then delivering it into the canal, the extracanal heating techniques.

Intracanal heating techniques

In these techniques, cold gutta-percha is placed in the canal and then heated to become soft and condensable. All the techniques involve the use of a sealer. The popularity of these methods was limited until Schilder64 described his method for filling canals using warm vertical condensation.

Warm vertical condensation

Logically, teeth with non-infected pulps and no sign of apical periodontitis can be prepared and filled in one visit, whereas infected cases with apical periodontitis should be treated cautiously, with additional appointments to allow an intracanal medicament to further reduce the microbial population. Unfortunately, research in this area is difficult and time-consuming and so far, a definitive answer is lacking. 13 Irrespective of the number of treatment visits, it is essential that the root canal can be thoroughly dried prior to filling, otherwise it will influence the effectiveness of the seal.

MATERIALS USED TO FILL ROOT CANALS

Many materials have been used to fill root canals. Historically, these range from feathers and wood sticks through a range of precious metals to amalgam and dental cements. The requirements for a root canal filling material have been specified for many years. 14 A large number of materials have proved to be inadequate, impractical or biologically unacceptable.

Resin-based sealers

Resin-based materials have been available for many years but they remain less popular than zinc oxide-eugenol sealers. The first resin sealer, AH 26 (Dentsply DeTrey, Konstanz, Germany), a powder and a liquid, consisted of an epoxy resin base which set slowly when mixed with an activator. It has good sealing26 and adhesive properties, and antibacterial activity. However, it produces an initial severe inflammatory reaction18 which subsides after some weeks and the material is then well tolerated by the periapical tissues. The resin has a strong allergenic and mutagenic potential27 and cases of contact allergy and paraesthesia28 have been reported. The material releases formaldehyde29 which may explain its strong antibacterial effect. 30 AH 26 has largely been superseded by AH Plus (Dentsply DeTrey), a two paste system formulated to polymerize without the release of formaldehyde; this sealer is also marketed as TopSeal (Dentsply Maillefer, Ballaigues, Switzerland). AH Plus is also less cytotoxic, with a thinner film thickness and lower solubility.

EndoREZ (Ultradent, South Jordan, UT, USA) is a urethane dimethacrylate (UDMA) based resin sealer. It is recommended for use with EndoREZ points (Ultradent), methacrylate resin coated gutta-percha points so that there is bonding between the root filling, sealer and the root canal dentine. Other resin sealers include Hybrid Root SEAL (Sun Medical Co. Ltd., Moriyama City, Shiga, Japan) or MetaSEAL (Parkell, Edgewood, NY, USA), both of the same chemical formulation and based on 4-methacryloethyl trimellitate anhydride(4-META).

Calcium silicate-based sealers

An advantage with these, newer types of sealer is their potential bioactive property. Similar to other tricalcium silicate and dicalcium silicate-containing biomaterials, calcium hydroxide is produced on reaction with water. It is anticipated that release of calcium and hydroxyl ions from the set sealer will result in the formation of apatites as it comes into contact with phosphate-containing fluids.

ProRoot Endo sealer (Dentsply Tulsa Dental, Tulsa, OK, USA) is a calcium silicate-based endodontic sealer that is designed to be used in conjunction with a root filling material in either the cold lateral, warm vertical or carrier-based filling techniques. The major components of the powder are tricalcium silicate and dicalcium silicate, with the inclusion of calcium sulphate as a setting retardant, bismuth oxide as a radiopacifier and a small amount of tricalcium aluminate. The liquid component consists of a viscous aqueous solution of a water-soluble polymer (polyvinyl-pyrrolidone homopolymer). Other calcium silicate-based sealers on the market include iRoot SP sealer (Innovative Bioceramix Inc., Vancouver, BC, Canada) and Endosequence BC sealer (Brasseler); the same product marketed under different names in different countries.

Gutta-percha has been used to fill root canals for over 130 years and is the most widely used and accepted root filling material. Gutta-percha is a form of rubber obtained from tropical trees of the Sapotaceae family. It is a trans isomer of polyisoprene, which exists in two crystalline forms, the α- and β-phases. The α-phase occurs naturally and the β-phase arises during refining; the two are interchangeable depending on temperature. Gutta-percha is mixed with other materials to produce a blend that can be used effectively within the root canal. Commercial gutta-percha cones contain gutta-percha (19–22%), zinc oxide (59–75%), various waxes, colouring agents, antioxidants, and metal salts to provide radiopacity. There is considerable variation in the stiffness, brittleness and tensile strength of commercially available gutta-percha cones and obturating products. 47

Gutta-percha cones are:

• non-allergenic to almost all individuals

• softened by organic solvents

• removable from the root canal when necessary.

However, the disadvantages are:

• do not adhere to dentine.

Glass ionomer sealers

The ability of glass ionomer cement to adhere to dentine would appear to provide a number of potential advantages over conventional sealers. Its endodontic potential was recognized soon after its introduction as a restorative material31 but it was many years before a product for endodontic use was formulated. The results of a multicentre clinical trial evaluating its performance32 suggested that it was similar to traditional sealers, but this sealer is no longer available.

Activ GP glass ionomer sealer (Brasseler, Savannah, Georgia, USA) was recently introduced for use with Activ GP points (Brasseler). The surface of these gutta-percha points is coated with glass ionomer. The sealer is meant to adhere chemically and micromechanically to the Activ GP points and also bond to the root canal dentine.

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