Methods of filling root canals:principles and practicesJOHN WHITWORTH

Contemporary research points to infection control as the key determinant of endodontic success. While

epidemiological surveys indicate that success is most likely in teeth which have been densely root-filled to within

2 mm of root-end, it is unclear whether the root canal filling itself is a key determinant of outcome. It is also unclear

how different materials and methods employed in achieving a ‘satisfactory’ root filling may impact on outcome.

This article provides an overview of current principles and practices in root canal filling and strives to untangle the

limited and often contradictory research of relevance to clinical practice and performance.

Introduction

Successful root canal treatment depends critically on

controlling pulp-space infection. In evaluating root

canal-treated teeth, it is unusual for external assessors

to have full information on the methods used and the

detail of infection-controlling steps. Attention there-

fore tends to focus on aspects of treatment which can

be readily identified and measured, such as the radio-

graphic nature, length and density of root fillings, with

the assumption that these are good proxy markers of

the overall package of infection-managing care. It is not

surprising that the majority of epidemiological surveys

in endodontics have focused on radiographic appear-

ances alone (1), despite our recognized limitations in

radiographic interpretation (2, 3), and acceptance that

the radiographic ‘white lines’ reveal only limited

information.

The classic ‘Washington study’ (4), although never

published in a peer-reviewed journal, set the tone by

observing that 58.66% of endodontic failures were

caused by incomplete obturation. Other well-estab-

lished undergraduate textbooks have emphasized that

‘lack of adequate seal is the principal cause of

endodontic failure’ (5), positions based on the best

clinical scientific evidence at the time.

Contemporary research points to cleaning and

shaping of the root canal as the single most important

factor in preventing and treating endodontic diseases

(6), and it is difficult to endow root canal filling with

the same primary importance. But to take such views

too rigidly, and to use reports of periapical healing

without definitive root filling as evidence that root

canal filling is unnecessary (7–10) is to miss the

important role it may play in securing short- and

long-term health (11, 12).

In technical terms, we anticipate that ‘success’ will be

associated with root canals (prepared and) densely filled

to within 2 mm of radiographic root end (1, 13).

However, the body of high-quality clinical research on

which such conclusions are founded is limited (14).

Even less clear is whether a technically ‘satisfactory’

root canal treatment will deliver health regardless of the

materials and methods, or whether some are inherently

‘better’ than others in terms of predictability, safety,

consistency, healing, and tooth longevity.

Commercial pressures and glossy advertising have

never been more prominent, but the debates are not

new. As early as 1973, Brayton et al. (15) noted that

‘Many techniques have been advocated for filling root

canals. Controversies and disputes have arisen, dividing

practitioners into different schools of thought. To date,

there is still very little evidence other than clinical

impression to support or deny any particular technique.’

As no single approach can unequivocally boast superior

evidence of healing success (13), decisions may be based

on such factors as speed, simplicity, economics, or ‘how it

feels in my hands.’ For some, there may be other issues at

stake, such as the desire to keep ‘up to date,’ to

demonstrate ‘mastery,’ to keep ahead of referring

2

Endodontic Topics 2005, 12, 2–24All rights reserved

Copyright r Blackwell Munksgaard

ENDODONTIC TOPICS 20051601-1538

colleagues, or to enliven the working day by ‘the thrill of

the fill’ (16) as unexpected canal ramifications are

demonstrated more consistently. For others, issues such

as root strengthening, or a fundamental lack of confidence

in established materials may be critical (17–19).

The role of root canal fillings inendodontic success

The shaped and cleaned canal space represents an

environment in which microbial communities have

been eliminated or seriously disrupted and can no

longer promote periradicular disease (6, 20).

But how is this condition preserved? Undue reliance

on a coronal seal is probably unacceptable without first

filling the canal system (21–23) with materials that

control infection:

1.Directly: by actively killing microorganisms (24)

which remain (25) or which gain later entry to the

pulp space, and

2.Ecologically: by denying nutrition, space to multiply,

and correct Redox conditions for the establishment

of significant biomass of individual microbes, or the

development of harmful climax communities.

They should do so long-term and without damaging

host tissues.

Basic approaches

Textbook accounts describe a spectrum of filling

methods (Fig. 1) ranging from paste-only fills, through

pastes with single cones of rigid or semi-rigid material,

to cold compaction of core material and finally, warm

compaction of core material with sealer paste. It is likely

that most accounts have assumed the materials involved

to be traditional sealer cements (such as zinc oxide-

eugenol pastes) in combination with metallic or gutta

percha cones. Sealer cements are usually regarded as the

critical, seal-forming ‘gasket’ of the root canal filling

(26), but paradoxically, as the weak link of the system

whose volume should be minimized by core compac-

tion (27, 28).

Paste-only root fillings

Paste-only root fillings have a poor reputation in clinical

endodontics. Notable approaches have included highly

toxic resin cements such as ‘Traitement SPAD’ and the

original, formaldehyde-containing Endomethasone

(Septodont, St Maur des Fosses, France), which were

advocated for rapid results in minimally prepared

canals. Although success was reported, in some cases

after deliberate apical extrusion with a spiral paste-filler

(29), such ‘quick and dirty’ approaches appeared to

deny the biological perspective that what came out of

the canal was more important to success than what

went in. Inadvertent accidents of over extension into

vital structures such as the inferior alveolar canal left a

distressing legacy for affected patients. Concerns were

compounded by the all too frequent insolubility and

hardness of such materials, making removal for re-

treatment a challenge to the most skilled of operators

(30, 31).

Even with fluid materials which are regarded as bland

and biocompatible, risks of erratic length control

Fig. 1 Classic spectrum of filling techniques,emphasizing the desirability of minimum sealer volume,from (A) paste only (least desirable), through (B) singlecones with paste, and (C) cold lateral condensation, to(D) thermoplastic compaction.

Methods of filling root canals: principles and practices

3

during application are recognized. Fannibunda et al.

(32) reported a case of inferior alveolar nerve para-

esthesia, which followed the inadvertent extrusion of

molten gutta percha. Porosities in large volumes of

fluid paste, setting contraction with loss of wall contact,

and dissolution with time have all reinforced the

negative views of such approaches. Even 1% shrinkage

of a material after setting has been recognized as a

potentially significant problem in terms of seal and

success (33).

Single-cone obturations

For similar reasons, the sealer-heavy root fillings

associated with single-cone root fillings have not been

regarded well. Single-cone obturations came to the fore

in the 1960s with the development of ISO standardiza-

tion for endodontic instruments and filling points (34).

After reaming a circular, stop preparation in the apical

2 mm of the canal, a single gutta percha, silver, sectional

silver or titanium point was selected to fit with ‘tug-

back’ to demonstrate inlay-like snugness of fit. The

cone was then cemented in place with a (theoretically)

thin and uniform layer of traditional sealer, at least in

the apical part of the canal. Hommez et al. (35) have

recently reported that single-cone obturation was still

the method of choice for 16% of Flemmish dentists.

Data from the UK has indicated that 49% of dentists

qualified more than 20 years and 13.2% of those

qualified 3 years regularly used single-cone techniques

(36). All experienced dentists have witnessed success

following the use of such techniques in skilled hands,

and within the context of infection control. In a

retrospective clinical study, Smith et al. (37) demon-

strated 84% success following cementation of an apical

silver cone with sealer, and 81% with a full-length silver

cone and sealer. Equally, all those who accept endo-

dontic referrals are very familiar with single-cone

removal from canals in which a large volume of

surrounding sealer has leached away or dissolved under

the action of tissue or oral fluids. Concerns were

compounded by the realization that canal transporta-

tion is common and that damaged roots are difficult to

seal (38).

The advent of nickel titanium makes predictably

centred preparations more realistic than ever in curved

canals (39), and may make accurate apical cone

fit a possibility in many cases (40). Contemporary

advertising on ergonomic, matched file and cone

systems may serve to promote single-cone cementation

techniques (Fig. 2). Laboratory evidence in fact

suggests comparable cross-sectional area of canal

occupied by gutta percha using single-matched taper

cones compared with lateral condensation, and in

significantly less time (41), but clinical trial data is

hitherto unavailable.

Are our views on paste-heavy fills still valid?

Mineral Trioxide Aggregate (MTA) (Fig. 3) has

challenged the view that paste-only root canal fillings

are difficult to control, unacceptably porous, dimen-

Fig. 2. Matched, ergonomic shaping files and fillingcones may inadvertently promote single cone fillingtechniques.

Fig. 3. Some commercial presentations of MineralTrioxide Aggregate

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4

sionally unstable and unacceptably soluble (42).

Unpublished data (43) indicates that endodontists

worldwide have adopted this material as first choice in a

range of applications from pulp capping, to the non-

surgical management of wide open apices.

A medical-grade Portland building cement (44),

MTA is mixed into a stiff paste with sterile water. The

consistency and behavior may be adjusted by varying

the powder:liquid ratio (45), and premature desicca-

tion is prevented by covering the mixed material with

moist gauze (Dentsply/Maillefer instruction guide

REF A 0405). Although the composition of the grey

and white forms is broadly comparable (44), the white

version appears to be less ‘gritty’ and more cohesive.

Material may be carried to the canal:

1. In a narrow, MTA carrier (or ‘apicectomy’ amalgam

gun),

2. On the end of a plugger after wiping material into

the grooves of a dedicated teflon ‘Lee’ block (46), or

after expressing a pellet of material from a gun (47)

(Fig. 4).

Material is then compacted with pluggers set to extend

2–3 mm short of working length, often supplemented

by ultrasonic (48) or sonic vibration with the intention

of improving settlement and adaptation, although the

merits of vibration remain contentious (49). Further

consolidation can be achieved by tamping the material

with the broad end of paper points to wick out excess

water which could retard the curing process (Dents-

ply/Maillefer). ProRoot MTA (Dentsply) is then

usually overlaid with moist cotton wool or sponge to

ensure a humid environment for the hydration setting

reaction (Dentsply/Maillefer). The need for this action

has not been established. Setting is checked by re-entry

at least 4 h after placement, and ongoing treatment may

then proceed. Another commercial version, MTA

Angelus (Angelus, Londrina, Brazil) (Fig. 3) is claimed

to set within 15 min and may therefore require no

overlay or re-entry.

MTA is firmly established as the material of choice for

open apices (precisely those where length control is

likely to be an issue, Fig. 5) (50), and perforation

repairs (51), where there is no risk of wash-out during

the lengthy setting period. It is possible that MTA may

supersede calcium hydroxide ‘apexification’ procedures

in the management of traumatized immature teeth

(52). Volumetric change and leakage (53) have not

been identified as significant issues.

MTA has not yet found widespread acceptance in

curved and relatively narrow canals, probably due to

difficult manipulation and concerns about re-treat-

ment. But its adoption in a range of challenging

applications suggests that concerns about root canal

filling cements are not universal. A question that

research must answer is whether other classes of cement

can be used safely and effectively in thick section during

root canal filling.

Fig. 4. Gathering Mineral Trioxide Aggregate ( on theend of a plugger from a ‘Lee’ block.

Fig. 5. Wide canal with a blown-out root end filled withMineral Trioxide Aggregate

Methods of filling root canals: principles and practices

5

Can all cements be viewed like traditionalendodontic sealers?

Limited evidence exists that other classes of material

may also be suitable for ‘sealer heavy’ or minimal

compaction techniques.

Glass ionomer cements

Ketac Endo (3M ESPE, St Paul, MN, USA) was

developed as an adhesive, root-reinforcing root canal

sealer to be applied in thick section with a single gutta

percha cone. Evidence on root reinforcement was

equivocal (17, 54, 55) and concerns have been

expressed about long-term solubility (56, 57), but

one clinical trial which included both single cone and

cold laterally condensed root canal fillings provided

outcomes comparable to those of other materials and

techniques (58).

Silicone rubbers

Addition polyvinylsiloxanes are well established in

dentistry as inert, dimensionally stable materials.

Formulations with reduced hydrophobicity are now

widely available, including two developed specifically

for endodontics. RoekoSeal (Roeko, Langenau, Ger-

many) is a white, fluid paste, whereas GuttaFlow

(Roeko) appears to be based on RoekoSeal, with the

addition of powdered gutta percha.

Materials are mixed with automix tips similar to

impression materials (RoekoSeal) or by trituration

(GuttaFlow) before carriage to the canal on a gutta

percha cone, or by passive injection through dedicated

plastic cannulae (Fig. 6). Single gutta percha cones

matching the apical preparation size are seated to

length in the sealer-filled canal, encouraging flow to the

apical region and into lateral ramifications.

Laboratory investigations indicate 0.2% setting expan-

sion (33), biocompatibility (59), and acceptable wall

coverage (60). A clinical trial comparing silicone sealer

with zinc-oxide eugenol in lateral condensation revealed

comparable healing outcomes (61), but outcome studies

on the single-cone method are not yet available.

The optimal canal preparation and shape of cone to

ensure adaptation and carriage to length without extru-

sion has not been established. Silicone rubbers provide

long-term seal in a range of wet environments and sealing

root canals may be a valid new application (62).

Urethane methacrylates

EndoRez (Ultradent, South Jordan, UT, USA) is a

hydrophilic urethane methacrylate resin capable of

good canal wetting and flow into dentinal tubules.

The mixed material is deposited into the canal by

passive injection through a narrow, 30 gauge ‘Navitip’

needle (Fig. 7) which is claimed to minimize pressure

buildup and over-extension. A single cone is again

floated to length to encourage material flow and

provide a pathway into the canal for re-entry. The

material is reported to have acceptable biocompatibility

(59, 63, 64) and to seal as well as other established

materials in vitro (65). No clinical data are available on

paste-only or single-cone EndoRez root canal fillings,

although in combination with cold lateral condensa-

tion, it was associated with 91.3% healing at 14–24

Fig. 6. GuttaFlow expressed from the end of a cannulaafter trituration.

Fig. 7. EndoRez expressed from a narrow Navitipapplicator needle.

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months (66), results comparable to other materials.

Tay et al. (67) have recently described the use of resin

coated gutta percha cones in combination with a dual-

curing EndoRez in an effort to enhance bond and seal.

Resin tags were demonstrated impregnating canal

walls, but interfacial leakage was not prevented.

Epoxy resins

Epoxy resins are well established as effective root canal

sealers, displaying acceptable biocompatibility (68, 69),

insolubility and dimensional stability (70).

AH 26 and AHPlus (Dentsply) are classic examples

with proven track records over many years of clinical use

(71, 72). In vitro tests have demonstrated comparable

seal in thin and thick section (65, 73).

AHPlus is specifically advocated with the single-cone

Lightspeed SimpliFill technique (Lightspeed Technol-

ogies, San Antonio, TX, USA). Following the prepara-

tion of an apical stop and parallel, cylindrical

preparation in the apical 5 mm of the canal with

Lightspeed instruments, a size matched gutta percha

(or Resilon) apical tip is selected which fits snugly just

short of working length in a moistened canal. After

conventional drying of the canal, a light coating of

sealer is applied, the apical tip is seated firmly to length,

and the handle removed by unscrewing anti-clockwise

(Fig. 8A). Carpules with 27 gauge needles which form

part of a dedicated injection system are then filled with

sealer, and the canal backfilled with cement (Fig. 8B).

One or more gutta percha points may be added if

desired. A recent in vitro leakage study has suggested

that backfill with AHPlus alone provided a better seal

against coronal leakage than AHPlus compacted with

injection-molded gutta percha (74).

EZ-fill (Essential Dental Systems, South Hackensack,

NJ, USA) is a similar material, presented like AH26 as a

powder and liquid for control of material viscosity.

Mixing with a warm spatula decreases the material’s

viscosity. Controlled delivery is achieved with an

innovative ‘bi-directoral spiral’ paste filler (Fig. 9).

The bi-directional spiral controls apical flow of sealer

cement by virtue of its blades which drive material

apically in the coronal region, and coronally in the

apical 2–3 mm. Canals are rapidly filled with sealer

before floating a pre-fitted 8% gutta percha cone to

length without the need for further vertical or lateral

compaction (Fig. 10).

EZ-fill is a rapid method, which appears to demon-

strate canal complexities well and in vitro studies have

shown it to seal as well as other established techniques

(75). Review of clinical cases managed in a multi-

Fig. 8. (A) SimpliFill device seated fully to length withsealer before unscrewing the handle; (B) preparing tobackfill by injecting sealer.

Fig. 9. Innovative bi-directional spiral for controlledsealer placement.

Fig. 10. EZ-fill/single cone root canal filling. (A)Immediate postoperative radiograph, (B) 6-monthsfollow-up (courtesy Barry Musikant).

Methods of filling root canals: principles and practices

7

surgery practice have indicated favorable clinical out-

comes estimated at 94.1% (76, 77), although once

again, independent clinical trial data are not yet

available.

Non-Instrumentation Technology

The previous section has described the delivery of sealer

cements by rotary instruments, injection, or carriage on

points of core material. A highly innovative approach is

found in non-instrumentation technology (NIT),

where the controlled development of a vacuum within

the tooth allows fluid sealer to be drawn into the

complexities of the canal system (78). This technology

has been subjected to one clinical trial in which the

radiographic quality of root fillings with AH 26 was

comparable to that of conventional techniques (79).

Gutta percha compaction methods

Despite the possibilities described, compaction meth-

ods continue to dominate clinical endodontics as

practitioners strive to optimize density of the core

material and minimize sealer volume. It is not

established beyond question whether compaction

methods benefit patients or dentists by preserving

health better, healing more disease or demonstrating

more canal complexities. Conversely, they could offer

no improvement and risk adverse events such as root

fracture or more frequent overfill. One in vitro study

has indicated that compaction may reduce canal wall

contact and seal of materials with insufficiently low

minimum film thickness (26).

Cold lateral condensation

Cold lateral condensation is probably the most

commonly taught and practiced filling technique

worldwide (35, 36, 80–82) and is regarded as the

benchmark against which others must be evaluated.

The method is generic, encompassing a range of

approaches in terms of master cone design and

adaptation, spreader and accessory cone selection,

choice of sealer and spreader application. There is little

clear evidence on how it is ‘best’ done (61, 83, 84).

Prerequisites

Canal preparation

Cold lateral condensation demands a canal which is

continuously flared from apex to coronal opening (85).

The superiority of apical stop or tapering control zone

preparations for lateral condensation has not been

investigated clinically.

Spreader selection

Condensing tools must be selected and tried into the

canals before compaction begins. For optimal deforma-

tion of material through the length of the canal, a

spreader must be pre-fitted which extends deeply into

Fig. 11. Accessory cones must occupy the space left by the spreader (A & B), otherwise an air or sealer-filled space willresult (C).

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the empty canal (86, 87). Hand spreaders encourage

higher compaction forces than finger spreaders (88),

with the theoretical risk of root flexion or fracture (89).

Nickel titanium spreaders may penetrate more deeply

(90, 91), generate less internal stress (92) and

distribute forces more evenly (93), especially in curved

canals.

Lateral condensation works by vertical loading of the

wedge-shaped spreader to move materials vertically and

laterally. The greater the taper of the spreader, the

greater the lateral component of force. Vertical loads in

the range of 1–3 kg have been reported as typical (94),

and adequate to deform gutta percha without undue

risks to the tooth (88, 95). Forces associated with

lateral condensation should not be a direct cause of

vertical root fracture (88).

Accessory cone selection

In order to secure a dense filling, accessory cones must

be able to fully occupy the space left by the compacting

spreader (Fig. 11). They should therefore be the same

size or slightly smaller than the selected spreader (84).

Incompatibility will result in the accessory cone

‘hanging up’ before full insertion, resulting in a cement

pool at best or a void at worst. In vitro evidence

suggests that tapered gutta percha accessory cones may

slide to length more predictably and be more forgiving

in the hands of non-specialists than ISO accessory

cones (84).

Master cone selection

There is no clear evidence whether ISO or unstandar-

dized cones are preferred. Laboratory investigations

(83, 87) suggest that ISO master cones allowed deeper

spreader penetration and a larger number of accessory

cones to be inserted, although this did not result in a

superior seal against microbial leakage. Unstandardized

cones may be trimmed to provide accurate apical sizing,

and are usually tried in an irrigant-lubricated canal.

Solvent dipping has been shown to improve apical

adaptation and seal of master cones in vitro (96). This is

typically achieved by immersing the apical 2–3 mm of

the master cone in chloroform or halothane for 2 s

before seating it to length in an irrigant-moistened

canal (Fig. 12).

Sealer selection

It is not known which sealer works most effectively with

cold lateral condensation, but clinical evidence suggests

that sealer choice may not have a decisive impact onFig. 12. Chloroform customized master cone.

Fig. 13. Cold lateral condensation. (A) Condensation and addition of gutta percha cones continues until the spreaderwill reach no more than 2–3 mm into the canal. Forces generated by vertical loading of the spreader are vertical andlateral. (B) Heat severs the gutta percha points and allows consolidation deep into the canal.

Methods of filling root canals: principles and practices

9

outcome (61, 97). A slow setting sealer cement is

generally preferred, which will allow adequate lubrica-

tion for accessory point insertion, and accommodate

revision and consolidation of the fill if voids are

detected on intermediate radiographs.

Leaving accessory cones with their tips immersed in

sealer may soften them and compromise their ability to

slide fully to length.

Cold lateral condensation: the process (Fig. 13)

Cold lateral condensation commences by liberally

coating canal walls with sealer cement. In vitro evidence

suggests that application with a spiral paste filler, fine

injection needle, or an ultrasonically energized file

ensures the most complete wall coverage (98–100),

although application on the master cone, a paper point

or a small file are popular alternatives. The master cone

is slid to working length and the measured spreader

applied under vertical loading for 10–60 s to

deform material apically and laterally (101, 102).

Optimal time of spreader insertion has not been

scientifically validated in the clinical setting. With-

drawal is with watch-winding motion to ensure that the

master cone is not pulled free, and the first accessory

cone is slid promptly to length with a light coating of

sealer. Compaction and accessory cone insertion

continues, as the filling develops, each spreader

insertion being slightly less deep than the previous

one mirrored by shorter and shorter accessory cone

insertion. Condensation usually continues until the

spreader will reach no further than 2–3 mm into the

canal (Fig. 13A). How closely general practitioners

comply with such guidelines has not been scientifically

evaluated.

Although the technique is described as cold lateral

condensation, heat is always applied to sever the root

filling at or below canal orifice level, and compact it

apically with a cold plugger (Fig. 13B). This may soften

and consolidate material several mm into the canal and

improve seal (103).

Variants on cold lateral condensation

A number of measures have been reported to enhance

gutta percha adaptation and density in lateral con-

densation. Examples include:

� Warming spreaders before each use in a hot bead

sterilizer

� Softening gutta percha with heat before insertion of

the cold spreader (104)

� Mechanical activation of finger spreaders in an

endodontic reciprocating handpiece (105)

� Application of an ultrasonically energized spreader

(106, 107), and

� Application of an engine-driven thermomechanical

compactor which creates frictional heat and ad-

vances the material apically within the canal (108,

109).

Figure 14 shows a complex canal system filled by

lateral condensation, supplemented with ultrasound.

Appraisal

Lateral condensation is regarded as safe, cost-effective

and user-friendly, and case reports continue to be

Fig. 14. Lateral condensation supplemented with ultra-sound in a complex upper molar (courtesy Dr GrahamBailey, London).

Fig. 15. An unsuitable case for predictable filling by coldlateral condensation.

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published showing successful healing after its use in a

variety of clinical scenarios (61, 110–114). A key

limitation is when the root canal system has an abrupt

change of diameter, as seen in internal resorption (Fig.

15). Such cases demand the application of heat to adapt

gutta percha more thoroughly, or a reliance on large

volumes of sealer in some areas of the canal. Adaptation

may be equally limited in ribbon-shaped canals, where

Kersten et al. (3) showed that clinical radiographs may

not reveal poor filling density.

However, recent clinical reports have confirmed the

ability of high-quality laterally condensed root canal

fillings to exclude the oral flora after long-term

exposure (115, 116) and it should also be noted that

the majority of epidemiological studies on which we

base our views on the predictability of root canal

treatment have included canal filling by cold lateral

condensation (117–123). Numerous other clinical

trials from around the world involving cold (39, 124–

133) and warm lateral condensation (134) have

validated this approach in clinical practice. But how

much of the observed success was directly attributable

to the filling technique is not known.

A common criticism leveled at lateral condensation is

that it is a time-consuming method, and this was borne

out in a recent clinical study, where Thermafil obtura-

tion was found to be on average 20 min per tooth

quicker (133).

Warm vertical condensation

Philosophical battles have long been waged between

advocates of cold lateral and warm vertical condensa-

tion, presenting compelling cases on the benefits and

shortcomings of each (135).

Warm vertical condensation was perfected and

promoted by Herbert Schilder (136). His approach

to filling was described as ‘3-dimensional,’ indicating

an intention to fill all ramifications of the pulp space,

rather than just the primary root canal, and the package

of care to achieve this included clear guidelines on canal

preparation, cone fit and condensation.

Contemporary advocates of this approach (137) list

the criteria for satisfactory canal shaping as:

1. Continuously tapered preparation.

2. Original anatomy maintained.

3. Position of the apical foramen maintained.

4. Foramen diameter as small as practicable.

The tapered canal preparations thus created allow

softened materials to enter anatomical complexities as

heat and pressure are applied in a canal of rapidly

diminishing diameter. Resistance to over-filling is

achieved by the creation of an apical control zone as

opposed to a traditional ISO ‘stop.’ Shaping is

considered to be sufficient when a Fine-Medium or

Medium cone (137) or other taper-matched cone (e.g.,

F2 for a ProTaper F2 prepared canal) can fit to length in

the canal.

Fig. 16. Scalpel-trimming an unstandardised guttapercha cone to conform to the ISO-gauged canalterminus diameter.

Fig. 17. Markings on the master gutta percha coneproduced by insertion of a file into an adjacent orificeindicates confluence.

Methods of filling root canals: principles and practices

11

Such preparations are now created rapidly and

predictably with a range of hand and engine driven

NiTi instrumentation techniques (138) and tapered,

rather than ISO master cones are scalpel trimmed to fit

snugly 1.0–0.5 mm short of an electronically confirmed

canal terminus (Fig. 16), or constant drying point

(139, 140). Snugness of fit is usually confirmed by

slight resistance to withdrawal from the canal (short

tug-back), indicating that the cone tip is binding at the

preparation terminus (141). Resistance to withdrawal

which continues beyond 1 mm may indicate that the

cone is binding along a greater length of canal wall and

not apically.

Canal confluence may be confirmed by the insertion

of a cone to working length before inserting a file or

spreader into the adjacent canal. Failure of the

instrument to advance to length, or evidence of

instrument markings on the side of the master cone

indicates confluence (Fig. 17). The master cone for the

second canal is trimmed to the point of confluence with

a scalpel.

Sealer selection

Classic descriptions of warm vertical condensation have

specifically advocated zinc oxide-eugenol sealers (Pulp

Canal Sealer, Kerr, Romulus, MI, USA) which are

believed to set rapidly in the event of extrusion and

hopefully become inert in the periradicular tissues (16).

There is, however, little clinical evidence that other

classes of material, such as slow-setting epoxy resins

may not perform equally well in warm vertical

condensation.

Multiple wave warm vertical condensation

Plugger and heater-tip selection

In common with other filling techniques, condensing

tools must be selected before treatment, and it is usual

to select three or more pluggers which will extend

progressively deeper into the canal, the narrowest

extending within 4–5 mm of root-end (142). Nickel-

titanium instruments such as the double-ended Bucha-

nan or Dovgan pluggers may be better suited to curved

Fig. 18. Warm vertical condensation – multiple wave. Heating and compaction occurs in three or more stages (A–C),taking an increment of gutta percha from the canal each time and continuing until the apical 4–5 mm are ‘corked’ withgutta percha and sealer.

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12

canals than stainless steel Machtou or Schilder plug-

gers.

Heat may be applied to the canal either with

traditional ‘heat carriers’ which are warmed in a Bunsen

burner flame, or more safely and neatly with an

electronic touch-and-heat instrument. The instrument

for delivering heat must have a narrow enough tip to

reach within 5 mm of root-end.

Sealer application

Warm vertical condensation generates significant hy-

draulic forces and there is an increased risk that excess

sealer may be extruded into the periradicular tissues

(109). In contrast with cold lateral condensation, sealer

application is therefore sparing, and often applied on

the master cone, coating its length before insertion and

seating to length initially before withdrawing to inspect

that its entire surface (and therefore presumably the

entire surface of the canal) has a light coating of sealer

16, 141).

The compaction process (Fig. 18)

Downpack

Compaction of the root canal filing occurs in multiple

waves as the material is softened with heat and driven

apically with cold pluggers. The first wave severs the

gutta percha cone at canal orifice level, taking care not

to withdraw the master cone from the canal. The largest

cold plugger is then applied, gently condensing

material around the walls of the canal entrance before

positioning in the centre of the mass of gutta percha

and compacting apically with firm finger pressure. Care

should be taken to avoid contact of the plugger with

canal walls, which is believed to carry an unacceptable

risk of damaging force transmission to the root.

The second wave of heating follows, plunging the

heat carrier or touch-and-heat tip 3–4 mm into the

Fig. 20. Calamus: engine-driven thermoplastic gutta percha in pre-dispensed cannulae (Courtesy Dentsply).

Fig. 19. Ultrafil low-temperature injectable guttapercha.

Methods of filling root canals: principles and practices

13

mass of compacted gutta percha and removing an

increment of material from the canal. Condensation

proceeds in the same manner as previously, using the

next plugger. Third and fourth waves of heating,

material removal and compaction proceed in a similar

manner until the apical 4–5 mm of the canal is ‘corked’

with thermally compacted gutta percha and sealer.

Progressive heating and compaction is expected to

drive gutta percha and sealer into all accessible canal

ramifications during the downpack (143, 144).

Backfill

Empty canal space is most quickly and efficiently filled

with injection-molded gutta percha, delivered from a

gun in increments of 3–4 mm and compacted by hand

to counteract cooling contraction. A variety of systems

are available, including:

� Pre-heated carpule systems offering gutta percha in

a range of viscosities (e.g., Ultrafil, Hygenic) (145)

(Fig. 19). Such systems are relatively inexpensive,

but offer limited working time before the carpule

must be re-heated.

� Manual gun systems which work on the same

principle as a glue gun, heating gutta percha pellets

and maintaining heat to the point of expression

from the gun (e.g., Obtura II), which offer the

advantage of unlimited working time. Radiogra-

phically seamless union with the downpack is more

likely to be achieved if the needle of the gun system

touches the cut gutta percha surface in the canal and

is held in place for 5–10 s before commencing

backfill injection.

� New-generation engine-driven gun systems, in

which temperature and flow rate can be regulated

(Fig. 20).

� Systems incorporating downpacking and backfilling

devices (Fig. 21).

Injectable gutta percha is commonly deposited in 3–

5 mm increments, with further compaction, although

one laboratory study supported the deposition of

increments up to 10 mm (146).

Alternative backfill methods include the incremental

addition of ‘backfill’ lengths of pre-trimmed gutta

percha which are heated and compacted as in the

downpack (147), and sealer-only backfills, which

recent laboratory reports have suggested are superior

to gutta percha compaction methods in terms of seal

(74, 148).

Single-wave vertical condensation (Fig. 22)

System B was the first of a new generation of electronic

heat carriers which allowed rapid heating and cooling of

tips to facilitate their use as both heat carrier and

plugger (Fig. 23).

Tip selection

System B is supplied with a variety of tips in 4%, 6%, 8%,

10%, and 12% taper, each marked at 5 mm intervals

along their length (16) (Fig. 23).

A single tip is selected which will extend to within 4–

5 mm of canal terminus before binding on canal walls.

Following cone fit, sparing sealer application and

cone insertion, the System B is set for maximal rate of

heat increase and to a working temperature setting of

2001C.

The cold tip is presented to canal entrance before

activating the heater. Within 1 s, the tip has reached

working temperature and is swept in one fluid move-

ment over the course of 2–3 s until it sits 2 mm short of

the binding point. At this point, the unit is de-

activated, allowing the tip to cool rapidly, and pressure

is maintained for 5–10 s on the cooling mass of gutta

percha in order to counteract cooling contraction. The

plugger now being locked into the canal by a solidifying

Fig. 21. Elements – combined System B and gun systemin a single unit (Courtesy Sybron).

Whitworth

14

mass of gutta percha, further heating is necessary to

release the tip for withdrawal from the canal. The heater

is therefore re-activated, classically by a 1 s ‘separation

burst’ before smooth withdrawal. The apical gutta

percha mass is then condensed further by hand before

backfilling by any of the methods described previously

(16).

Evaluation of warm vertical condensationCompaction techniques of any sort require dentine

removal to accommodate condensing instruments and

the application of potentially damaging forces in non-

physiological directions.

In warm vertical condensation, opponents have

historically argued that the cost in terms of dentine

Fig. 22. Warm vertical condensation – single wave. (A) Single wave downpack. (B) Separation and withdrawal. (C)Apical 4–5 mm ‘corked’ with gutta percha and sealer.

Fig. 23. Original System B heat source with a range of tips.

Methods of filling root canals: principles and practices

15

removal to accommodate appropriate pluggers was

excessive compared with that required for lateral con-

densation. This seems to be less of an issue in current

practice with controlled canal flaring by contemporary

instruments, and a welcome range of sufficiently

narrow and efficient heat carriers, pluggers (including

nickel titanium pluggers) and backfill needles.

Additional concerns have been raised with regard to

thermal damage to the periodontal ligament during

thermal compaction techniques, particularly if tem-

perature guidelines are exceeded (149–152). Evidence

on this appears to be equivocal (153, 154), with most

of the modeling taking place in the laboratory setting

where the heat-buffering effects of a richly perfused

periodontium cannot properly be taken into account.

There is little clinical evidence of adverse periodontal

responses following thermoplastic obturation in clin-

ical practice.

Perhaps as important are the questions of efficacy and

control.

Many laboratory studies have addressed how well

warm vertically compacted gutta percha adapts to canal

walls and reduces sealer-pools following heating and

compaction to different depths. The consensus of

recent laboratory reports is that heating and compac-

tion within the apical 2–3 mm of the canal is required

for optimal gutta percha adaptation to the canal

terminus (155–159), with significant (30%) differences

in area of canal occupied by gutta percha following heat

application to 2 or 4 mm from canal terminus (157). It

is difficult to imagine that the majority of practitioners

working in curved canals are able to consistently deliver

heat and pressure to such depths, and in reality, many

warm vertically compacted root canal fillings may

comprise of a single, minimally distorted cone in the

apical few millimeters.

Warm vertical condensation techniques are designed

to drive materials into anatomical complexities (16),

but a higher prevalence of sealer extrusion is recognized

(109) with potential for further tissue injury and

delayed healing. However, a recent clinical report (160)

found no association between sealer extrusion and

postoperative pain, whereas small extrusions of zinc

oxide-eugenol sealers have been shown to resorb

(161). A recent 20–27 year review on teeth with

extruded of filling materials showed progressive peri-

apical improvement with time (162).

Clinical studies (39, 109, 125, 132) and case reports

(163, 164) have convincingly reinforced the view that

warm vertical condensation techniques can enjoy

comparable success to lateral condensation methods.

The impact on clinical outcome is central to our choice of

techniques, and until recently, there has been little to

separate established methods. However, data from a recent

longitudinal study suggests that root canal treatments

involving minimal apical enlargement and warm vertical

condensation may be associated with higher successes than

large apical preparations and cold condensation (165).

Whether the filling technique or the overall approach to

treatment was critical is hitherto unclear.

Carrier systems

Carrier systems represent another convenient means of

delivering thermally softened gutta percha to canal

Fig. 24. Carrier obturation. (A) Verification of the canal with a blank carrier. (B) Smooth insertion into a lightly sealer-coated canal. (C) Cut-back of the carrier.

Whitworth

16

systems with some degree of control. This approach is

typified by Thermafil, which has developed from a

method involving the coverage of a conventional file

with regular gutta percha (166) to contemporary

plastic carriers coated with flowable, reduced molecular

weight gutta percha (167). Carrier methods and may

be considered low temperature techniques with little

risk of overheating tissues (168).

Clinical application (Fig. 24)

Verifying the preparation

In common with other techniques, the compacting

tool (in this case, a plastic blank, which in the filling

devices is covered with gutta percha) must first be tried

in the canal to ensure that it will be able to carry and

compact material to full length. This takes special

importance in the case of carrier systems, where

insertion occurs in one action, with little opportunity

to revise the result if the carrier does not go to length

first time.

Products from different manufacturers have differing

degrees of taper, which may make some systems more

suitable with certain canal shapes than others.

Whole systems are available with matched shaping

instruments, absorbent points, and carrier devices (40,

169).

Such systems introduce an element of ergonomics to

root canal treatment and may be welcomed by many.

The relative success of such systems in different

configurations is largely unknown.

Preparing the device

The majority of practitioners probably use Thermafil

and other devices as supplied.

As there is usually an excess of gutta percha on the

carrier, and as the excess apical to the tip of the plastic

carrier is not accurately known, some choose to

� trim back the apical extent of gutta percha until

1.5 mm of the tip of the carrier is visible, with the

reported intention of allowing more accurate

carrier control during insertion and limiting excess

gutta percha extrusion beyond the root apex (16)

(Fig. 25)

� Remove the most coronal 2–3 mm of gutta percha

from the carrier, with the intention of limiting

Fig. 25. A Thermafil device prepared for use. Upper device unaltered; lower device trimmed to remove excess guttapercha apically and coronally.

Fig. 26. (A) Resilon, a biodegradable polycaprolactonewith (B) matching sealer.

Methods of filling root canals: principles and practices

17

excessive gutta percha in the pulp chamber (16)

(Fig. 25).

It is critical for the development of adequate flow and

to facilitate insertion that the device is heated to the

correct temperature, and for the required time in the

manufacturer’s recommended oven.

Sealer application

The insertion of a well-fitting Thermafil device is akin

to inserting the plunger of a syringe to the root canal.

As a consequence, and in contrast to cold lateral

condensation, where excess sealer will slowly migrate

coronally, excessive sealer application should be

avoided to reduce the risk of large-scale apical extru-

sion.

Sealer is generally applied sparingly on a paper point,

with the subsequent insertion of further dry paper

points to ensure that excess has been removed and that

there is even, light wall contact (16).

Carrier insertion

When the carrier is adequately heated, it is removed

from the heater without delay or distraction and

smoothly seated to full working length in one smooth,

fluid movement.

In the hands of skilled and experienced operators,

the extent of gutta percha and sealer movement

can be controlled by the rate of carrier insertion

(G. Cantatore, personal communication, 2005), and

laboratory evidence (170) has suggested that more

rapid insertion captures apical detail better than slow

insertion.

Condensation pressure may be applied with a small

plugger to compensate for some of the shrinkage which

inevitably accompanies cooling. The shank may then be

severed with a bur or heated instrument.

Evaluation

Laboratory evidence suggests that Thermafil obtura-

tion is a low-pressure technique (171, 172), capable of

rapid, and dense filling of root canal systems and their

ramifications (11, 173–175).

Periapical extrusion has again been identified as a

potential drawback of Thermafil (175) and Da Silva et

al. (176) have therefore described a modified carrier

obturation technique in which a sealer-coated master

gutta percha cone is first inserted to length before the

heat-softened carrier. This method has been shown in

vitro to create dense root canal fillings while controlling

apical extrusion of materials, and presumably, after

pain.

Two clinical trials have been reported recently.

Gagliani et al. (177) have shown 94.9% periapical

health in teeth with apical periodontitis, and 48.2%

healing in teeth without apical periodontitis, 24

months after treatment with Profile and Thermafil,

whereas Chu et al. (133) showed comparable, 80%

success at 3 yr review in teeth filled with Thermafil or

lateral condensation. Lateral condensation was, how-

ever, found to take 20 min longer on average per tooth

than Thermafil.

Carrier devices are firmly established in clinical

practice, and are reported to be especially effective in

long, curved canals, where the insertion of conven-

tional spreaders and pluggers may be compromised

(167).

Resilon (Fig. 26)Despite apparently satisfactory performance over many

decades, and in a variety of guises, gutta percha and

sealer filling techniques do not represent the universal

ideal. Although few materials, with the exception of

MTA, have seriously challenged gutta percha and sealer

in the majority of filling situations, research continues

to find alternatives which may seal better, mechanically

reinforce compromised roots, and avoid any potential

for adverse responses in latex-allergic patients.

Resilon, a polycaprolactone core and sealer filling

system has recently entered the market as Real Seal

(Dentsply, Tulsa, OH, USA), Epiphany (Pentron,

Wallingfort, CT, USA) and Resilon Simplifill (Light-

speed Technologies). Cones of ISO and increased

taper, and pellets for injection-molding are available,

with the recommendation that the material can be used

in any conventional technique. Melting temperatures

are, however, reduced to 1501C for System B, and to

1401C for Obtura (178). Anecdotal reports suggest

that the material is user-friendly but does not retain its

softness after heating as well as gutta percha. Compo-

nents were developed to bond with each other and with

canal walls to produce an hermetically sealing (19) and

root-reinforcing (18) monobloc of material. Claims on

the in vitro sealability of Resilon were recently

challenged by independent researchers (178), but

recent clinical research in dogs has confirmed that

Resilon provides a better coronal seal against microbial

ingress than laterally or vertically compacted gutta

percha with AH26 (179). Clinical studies in humans

are awaited.

Whitworth

18

Conclusions

Although the importance of root canal filling should

not be diminished within a package of infection-

controlling care, clinical trials have failed to identify

filling methods as significant in endodontic outcome

(39, 109, 129, 132, 133). Meta analysis has also

provided little evidence that endodontic outcomes have

improved with time (180), indicating that the explo-

sion of technology in endodontics may have met needs

other than those of simply healing more disease. Recent

case reports demonstrate the extraordinary skills of

contemporary endodontists, but the message of the

radiographic white lines may be weakened without

follow-up images to demonstrate biological success

(181, 182).

Most critical may be the elements of care which are

not seen; the integrity of the operator in securing

infection control at every step, rather than the details of

materials and methods. Within that framework, the

choices of practitioners may justifiably be based on

individual preference and particular practice circum-

stances.

The clinical science of root canal filling is weak, and

weighted toward laboratory studies, often of question-

able clinical relevance and with little standardization of

method. There is a need to translate daily practice into

research data to provide stronger evidence to support

our care of patients.

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