Letter to the Editor

Terminology of endodontic outcomes

Dear Editor

In a recent letter to the Editor, Wu et al. (2011) pro-

posed an alternative terminology for the outcomes of

root canal treatment and invited open discussion of

the topic. We support their suggestion of formal, pub-

lished debate on controversial issues important to

endodontics, and commend the Editor for permitting

such debate to be published in the IEJ. We submit this

letter in response to their proposal.

Wu et al. (2011) proposed the terminology of effec-

tive and ineffective for the outcome of treatment,

which is judged 1 year after treatment. An additional

category of uncertain is applied to cases which are

asymptomatic but demonstrate no change in lesion

size, and teeth in this category require monitoring

for an additional year. The authors contrast the

terms effective and ineffective with successful and

failed. We would like to argue against the proposed

terminology, on two grounds: first that it places the

focus on treatment rather than on disease and heal-

ing, in the same way that success/failure does; and

secondly that a 1 or 2 year cut-off is too rigid to

allow for biological variation in healing.

Treatment versus disease/healing

The traditional terminology of success and failure

served endodontics well for decades. Strindberg

(1956) used it (with an uncertain category as well),

and it remains in widespread use today. As one exam-

ple, the current edition of the textbook Endodontic

Principles and Practice (4th edition 2009) retains this

terminology (Torabinejad & Sigurdsson 2009). It is

very convenient shorthand for describing outcomes,

and endodontists seem to have a strong predilection

for dichotomous outcomes rather than more complex

classifications such as the PAI (rstavik et al. 1986).

Even the PAI is often dichotomized in the analysis of

treatment outcomes in clinical studies.

On the other hand, rstavik (1996) argued that

the terms success and failure were inconsistent with

the dynamic nature of disease and should be replaced

by a terminology of healing versus persistent/develop-

ing disease. Friedman & Mor (2004) also stressed that

endodontic treatment outcomes should be defined in

reference to healing and disease. Friedman (2008)

subsequently elaborated this argument in detail. Ear-

lier authors such as Bystrom et al. (1987) had used

similar terminology (completely healed, incompletely

healed or healing, and not healed). In 2005, the

American Association of Endodontists formally

adopted the terminology of healed, healing and non-

healed (American Association of Endodontists 2005).

[The additional category of functional (Friedman &

Mor 2004, Friedman 2008) will be addressed later in

this letter].

The fundamental distinction between the two clas-

sification schemes cannot be overemphasized. The

terminology of success and failure relates primarily to

treatment, whilst the terminology of healing relates to

the disease and the patient. The latter acknowledges

that patient-related factors other than the root canal

treatment itself can influence outcome: microbial

challenge versus host defences, extra-radicular infec-

tion, caries, periodontal status and occlusal stresses.

Other treatment-related factors such as the restora-

tion also have an influence. Many of these factors are

beyond the endodontists control and independent of

the root canal treatment itself.

With its focus on treatment, the terminology of

effectiveness is for practical purposes synonymous

with that of success and failure. A successful out-

come means that the treatment was effective; a failure

implies that the treatment was ineffective. The inten-

tion of the new terminology in Wu et al. (2011) is

unclear.

Follow-up period

Wu et al. (2011) also proposed that the follow-up

interval for determining outcome should be 1 year. In

uncertain cases which are asymptomatic but with no

detectable change in lesion size after 1 year, periapi-

cal status should be monitored for 1 additional year

only. A large part of their argument is related to

improving the low recall rates of clinical studies

with longer follow-up intervals, hence the reliability

of outcome studies. However, the problem of low

recall rates does not arise in relation to retreatment

decision-making for individual patients. Here, the

2012 International Endodontic Journal. Published by Blackwell Publishing Ltd International Endodontic Journal, 46, 289291, 2013

doi:10.1111/iej.12014

289

question is: at what point should we conclude that

healing is not occurring and recommend further

intervention?

The data of rstavik (1996) provide strong support

for the adequacy of a 1 year follow-up for many

cases. Only a small proportion (6%) of roots without

a preoperative lesion developed new lesions following

treatment, and 76% of those emerged in the first

year; late failure was rare. Approximately 44% of

all lesions present initially had healed completely (PAI

score of 1 or 2) after 1 year. Of lesions showing

unequivocal but incomplete healing (PAI score of 3,

down from a preoperative score of 4 or 5) at 1 year

follow-up, only one subsequently showed a reversal.

rstavik (1996) concluded tentatively that it is possi-

ble, therefore, that any tooth eventually healing will

already have shown radiographic signs of the process

after 1 year. It should be noted in passing that the

recall rate in that study declined from 67% at 1 year

to 37% at 4 years, so perhaps, the validity of this

conclusion should be held lightly!A reasonable conclusion from rstaviks study is

that teeth without periapical radiolucencies 1 year

after treatment (either no lesion present initially or a

completely healed lesion) do not need to be routinely

monitored further. Wu et al. (2011) also recommend

that asymptomatic lesions showing partial resolution

at 1 year follow-up do not need further monitoring,

whilst lesions that are increasing in size require inter-

vention. Up to this point, we agree with Wu et al.

(2011) although some endodontists may prefer to

continue monitoring incompletely resolved lesions.

However, we question their suggestion that asymp-

tomatic lesions unchanged in size after 1 year

(uncertain category) should be monitored for only

one additional year before a decision on further

management. This is a departure from the more

conventional recommendation (European Society of

Endodontology 2006) of monitoring asymptomatic

lesions for up to 4 years.

We need to distinguish between clinical trials (out-

come studies), where a specified endpoint of 2 years

rather than 4 may be desirable, and the care of indi-

vidual patients. Compliant patients can be monitored

for longer periods following treatment, and there is

no compelling reason to stipulate a rigid endpoint

for follow-up. It may lead to unnecessary retreat-

ments, which Wu et al. (2011) rightly wish to mini-

mize. The risk of a painful exacerbation is low and

healing after prolonged periods (20+ years) has beendocumented.

Friedman & Mor (2004) made an extremely useful

contribution to the question of patient follow-up and

intervention when they proposed the outcome cate-

gory of functional, in which the clinical presentation

is normal, and the tooth is serving its intended

purpose in the dentition (AAE 2005). Functional is

essentially equivalent to clinical normalcy without

regard to radiographic (periapical) status. Some of the

impetus for this classification was the controversy

over replacing failed root-filled teeth with implants,

leading the authors to state that the asymptomatic

functional state allows the tooth to be retained

without necessitating extraction. However, an

unstated implication is that such teeth may also be

monitored as long as they remain asymptomatic,

rather than undergoing retreatment. It also intro-

duces the important element of patient involvement

in decision-making. There is a strong clinical and

biological rationale for this approach.

A large majority of persistent lesions remain

asymptomatic with little radiographically detectable

change over long periods. The risk of painful exacer-

bation is low. Eriksen (2008) estimated the incidence

of exacerbation at 5% per year, whilst the data of

Van Nieuwenhuysen et al. (1994) suggest that it may

be as low as 12% per year. In our recent study

(Yu et al. 2012a), the overall incidence of flare-up

requiring emergency intervention amongst patients

with persistent lesions was only 5.8% over 20 years.

Whilst less severe pain was more frequent, the impact

on daily activities was minimal. Additionally,

complete radiographic resolution may occur after

extended periods, in one study (Molven et al. 2002)

even after 2027 years. We have recently reported

(Yu et al. 2012b) that a majority of asymptomatic

lesions persisting for 420+ years had decreased insize since treatment. As a result, we recommended

that no specific endpoint should be used to conclude

that a lesion will not resolve without intervention.

Continued monitoring of asymptomatic lesions in

functional teeth is a completely justifiable approach.

[The possible systemic implications of persistent

lesions (e.g. Cotti et al. 2011) are beyond the scope of

this letter.]

In our judgment, it is time to abandon the

treatment-oriented success/failure (or the suggested

effective/ineffective) dichotomy, and to adhere to a

disease/healing paradigm. Just as there are vary-

ing severities of disease, there are varying degrees of

response to treatment. Arresting and partially

reversing disease progression, and preserving or

Letter to the Editor

2012 International Endodontic Journal. Published by Blackwell Publishing LtdInternational Endodontic Journal, 46, 289291, 2013290

restoring a reasonable degree of function for a period

of time all constitute a benefit to patients. We should

not put the healing process into a straitjacket of 2 (or

even 4 or 10) years, for complete resolution to occur.

The real challenge confronting endodontists is to

identify the risk factors for and indicators of progres-

sive disease and to develop a rational decision-making

process to determine when further intervention is

required.

H. H. Messer1,2 & V. S. H. Yu2

1Melbourne Dental School, Melbourne, Vic., Australia2Faculty of Dentistry, National University of Singa-

pore, Singapore City, Singapore

E-mail: hhm@unimelb.edu.au

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Letter to the Editor

2012 International Endodontic Journal. Published by Blackwell Publishing Ltd International Endodontic Journal, 46, 289291, 2013 291