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Accepted Manuscript

What is the risk of future extraction of asymptomatic third molars? A systematic

review

Gary F. Bouloux, DDS, MD, MDSc, FRACDS(OMS) Kamal F. Busaidy, BDS,

FDSRCS O. Ross Beirne, DMD, PhD Sung-Kiang Chuang, DMD, MD Thomas B.

Dodson, DMD, MPH

PII: S0278-2391(14)01628-0

DOI: 10.1016/j.joms.2014.10.029

Reference: YJOMS 56547

To appear in: Journal of Oral and Maxillofacial Surgery

Received Date: 2 August 2014

Revised Date: 28 September 2014

Accepted Date: 24 October 2014

Please cite this article as: Bouloux GF, Busaidy KF, Beirne OR, Chuang S-K, Dodson TB, What is

the risk of future extraction of asymptomatic third molars? A systematic review,Journal of Oral and

Maxillofacial Surgery(2014), doi: 10.1016/j.joms.2014.10.029.

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http://dx.doi.org/10.1016/j.joms.2014.10.029

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What is the risk of future extraction of

asymptomatic third molars? A systematic

review

e Page

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What is the risk of future extraction of asymptomatic third

molars? A systematic review

Authors

Gary F Bouloux DDS, MD, MDSc, FRACDS(OMS)

Associate Professor and Residency Program Director

Division of Oral and Maxillofacial Surgery

Department of Surgery

Emory University School of Medicine

Atlanta, GA

Kamal F Busaidy BDS, FDSRCS

Associate Professor

Division of Oral and Maxillofacial Surgery

Department of Surgery

University of Texas Health Sciences Center

Houston, TX

O. Ross Beirne DMD, PhD

Professor

Department of Oral and Maxillofacial Surgery

University of Washington School of Dentistry

Seattle, WA

http://ees.elsevier.com/joms/download.aspx?id=689563&guid=de620d95-8c89-4f15-a23a-48d993c02e08&scheme=1

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Sung-Kiang Chuang DMD, MD

Associate Professor

Department of Oral and Maxillofacial Surgery

Harvard University School of Dental Medicine

Boston, MA

Thomas B Dodson DMD, MPH

Professor and Chair

Department of Oral and Maxillofacial Surgery

Associate Dean for Hospital Affairs

University of Washington School of Dentistry

Seattle, WA

Corresponding author: Dr. Gary Bouloux

Acknowledgements: The authors would like to thank Mr. Martin Gonzalez and Ms.

Pat Pinkowski for the administrative support they provided in preparing this

manuscript.

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ABSTRACT

Purpose: The purpose of this paper is to answer the following clinical question:

Among young adults who elect to retain their asymptomatic third molars (M3s),

what is the risk of having one or more M3s extracted in the future?

Materials/Methods: To address the clinical question, the authors designed and

implemented a systematic review. Studies included in the review were prospective,

had sample sizes > 50 subjects with at least one asymptomatic M3, and at least 12

months of follow-up. The primary study variables were the duration of follow-up

(years) and the number of M3s extracted at the end of follow-up or the number of

subjects who required at least one M3 extraction. Annual and cumulative incidence

rates of M3 removal were estimated.

Results: Seven studies met the inclusion criteria. The samples sizes ranged from 70

821 subjects and follow-up ranged from 1 to 18 years. The mean incidence rate for

the M3 extraction of previously asymptomatic M3 was 3.0% per year (range 1 - 9

%). The cumulative incidence rates for M3 removal ranged from 5% at one year to

64% at 18 years. The reasons for extraction were caries, periodontal disease, and

other inflammatory conditions

Conclusion: The cumulative risk of M3 extraction for young adults with

asymptomatic M3s is sufficiently high to warrant its inclusion when reviewing the

risks and benefits of M3 retention as a management strategy.

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INTRODUCTION

The management of asymptomatic third molars (M3s) is controversial and

currently unresolved. Some authors advocate for M3 retention until clinical signs

and symptoms dictate a need for removal. 1, 2Others advocate for early removal of

M3s given the potential for caries3-9, pericoronitis 4, 5, 7, 10-14and periodontal disease

6, 9, 15-18. However, a systematic review by the Cochrane Collaboration failed to

provide insight and concluded that the evidence was insufficient to support or

refute the removal of third molars to prevent future problems.19

The American Association of Oral and Maxillofacial Surgeons (AAOMS)

recommends that young adults be evaluated to assess for the presence and disease-

status of M3s. If the M3s are asymptomatic and disease-free, AAOMS recommends

removal of M3s to prevent future problems, or retention and monitoring of the M3

status. Individual surgeons should review the risks and benefits of both treatment

options and make recommendations after considering patient preference regarding

M3 management.20

Commonly, during the presentation of treatment options patients inquire as

to the future need for M3 removal. The purpose of this paper is to address that issue

by answering the following question: Among young adults who elect to retain their

asymptomatic M3s, what is the risk of having one or more M3s extracted in the

future?

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MATERIALS AND METHODS

To address the research question, the investigators designed and

implemented a systematic review. Online electronic searches were performed in

PubMed, Google Scholar and the Cochrane Central Register of Controlled Trials to

identify articles to include in the review. The PubMed data base was queried for

[molar, third] and [asymptomatic]; [molar, third/surgery] and [epidemiologic

studies]; [molar, third] and [pubmednotmedline]. Abstracts and subject headings

from the resulting searches were manually reviewed to select articles mentioning

retention of third molars and identifying the type of study done. Selected articles

had manual reviews of all references through PubMed. Additionally, Google scholar

was queried for [third Molar Asymptomatic]. Abstracts were manually reviewed by

the 5 investigators to select articles reporting on retained third molars.

Study Criteria

Studies were included if they were an English language publication, were a

prospective study design, had more than 50 subjects, subjects > 18 years of age who

had a least one M3 present at enrollment, had only asymptomatic M3s at

enrollment, had recorded the number of subjects or M3s requiring extraction

overtime, and the duration of follow-up was > 1 year. The investigators made the

assumption that the teeth were retained because they were asymptomatic and

disease free M3s.

Studies identified for possible inclusion from the reviewed abstracts were

obtained and further reviewed by all the professional members of the AAOMS M3

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Taskforce (n=5, all authors on this paper). Studies identified for detailed analyses

were reviewed for quality by each taskforce member.

Data Extraction

A standardized data extraction form was used by all 5 task members who

independently extracted and tabulated data. Discrepancies were resolved by group

discussion. Factors assessed in reviewing the studies included study design, sex, age,

practice type, smoking, eruption status, absence of symptoms, absence of caries and

periodontal disease, sample size, duration of follow-up, attrition and number of

subjects or teeth that required removal over time.

Study Variables

The primary predictor variable was duration of follow-up, recorded in years.

The primary outcome variable was either the number of M3s removed during the

follow-up period or the number of subjects who required one or more M3s removed

during this time. Other study variables included subject age and number of M3s or

subjects present at the baseline examination.

Data Analysis

Data was analyzed with descriptive statistics. Limiting studies to only include

those with greater than 50 subjects eliminated the need for special considerations for

the statistical distributions of small sample sizes. To estimate the cumulative incidence

rate of M3 removal, the number of M3s (or subjects) removed during follow-up was

divided by the total number of M3s (or subjects). The annual incidence rate was

estimated by dividing the cumulative incidence rate by the total number years of

follow-up.

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RESULTS

During the initial literature search, 65 articles were identified that reported

on the number of teeth or subjects that required extraction of previously

asymptomatic M3s over time. Seven articles were included in the analysis. (Figure

1) Twenty-two papers were excluded because they had a retrospective study

design. Of the remaining 43 studies, 36 were excluded because of one or more of

the following criteria: insufficient follow-up, at least one 3M was not present at

inception, outcomes were not reported as teeth extracted or subjects who had

extractions.

All seven studies reported the number of subjects, follow-up period and the

number of M3s at inception1, 9, 21-25. The mean age of subjects at inception in the five

studies that provided data was 25.2 years. All studies included mandibular M3

extractions, and 4 studies included maxillary and mandibular M3s. (Table I)

Third Molars Extracted

The follow-up ranged from 1 18 years with a mean of 8.8 years. Four

studies reported the number of M3s extracted over time 1, 9, 23, 24. Two studies

reported the percentage of M3s extracted 21, 25. The cumulative incidence for M3

extraction varied from 5 64% and was associated with the duration of follow-up.

The annual incidence rates for M3 extraction varied from 1-9% with a mean of 3.0%

per year. (Table II).

One study reported the percentage of subjects who required M3 extraction

with 31% of subjects requiring at least one M3 extraction over 5 years with an

annual incidence of 6% of subjects per year22(Table III)

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DISCUSSION

The purpose of this study was to address the following question; Among

young adults with asymptomatic M3s, what is the future risk for M3 removal over

time? The results of this review suggest that the mean annual rate for extraction is

3% of previously retained asymptomatic M3s during the age range studied.

Although the annual risk of extracting at least one originally asymptomatic,

disease-free M3 is low, 3%, the cumulative extraction risk over time appears to

increase with the risk for extraction being 64% after 18 years of follow-up in one

study. The time points at which the third molars were extracted during the studies

was not reported. This prevents calculating the variation in the rate of extraction

over time through a life table analysis which would provide a better understanding

of age related changes in the frequency of M3 extractions. The 3% annual risk of M3

extraction is unlikely to be constant over time and it is likely that the risk of

extraction decreases with age while the initial risk for extraction may actually be

higher than the 3% reported.

Patients who initially present with caries, periodontal disease, pericoronitis

or other pathology related to M3s are appropriate candidates for M3 removal. A

more controversial situation arises in young patients who initially present with

asymptomatic and disease free M3s. Deferring M3 extraction in this patient

population until signs or symptoms of pathology develop may initially appear a

logical choice, but given an annual 3% risk of extraction it may then be more

prudent to remove even asymptomatic M3s. Although the M3s in the studies only

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reported currently asymptomatic third molars, it is not clear whether subjects had

previously experienced signs and symptoms related to these teeth. It is therefore

also possible that the initially asymptomatic third molars had sub clinical disease at

the study inception. This may also influence the likelihood of subsequent extraction.

Caries, periodontal disease and other inflammatory conditions were the most

identified reasons for subsequent extractions. It is also possible that some of the

M3s that were extracted were disease free and asymptomatic. This may contribute

to an overestimation of the cumulative annual risk of M3 extraction.

Complications from M3 removal are generally minor and infrequent, but can

vary considerably26, 27. Pain, edema and decreased function are typical, but these

symptoms normally resolve within a few days of the procedure 28, 29. The greatest

concern relates to lingual and inferior alveolar nerve injury. Several factors

influence the risk of this complication including M3 position (degree of impaction)

and advancing age26-31. The potential for an increased complication rate in patients

who initially defer M3 extraction, but ultimately require M3 removal at an older age,

may also support the extraction of initially asymptomatic M3s.

The AAOMS and the American Academy of Pediatric Dentistry both advocate

for the removal of asymptomatic M3s if there is a likelihood of future pathology 32-34.

This preventative approach to M3 pathology has not been supported in the United

Kingdom by the National Institute for Clinical Effectiveness (NICE) given the

purported low risk for pathology to develop and the cost effectiveness of

prophylactic removal2. The cost effectiveness of prophylactic M3 removal was also

questioned by Edwards35. However, a review of current patterns of M3 extraction in

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Table I. Descriptive Statistics

Authors Country Number

of

Subjects

Age

(yrs)

Sex

(M/F)

M3 Site M3 at

baseline

Von Wowern24

(1989)

Denmark 70 20.3 24/46 Mandibular 130

Garcia9(1989) USA 97 47 97/0 Maxillary/Mandibular 151

Venta1. (2000) Finland 81 20.7 32/49 Maxillary/mandibular 285

Kruger21(2001) New

Zealand

821 18.0 417/404 Maxillary/Mandibular 2652

Venta25.(2004) Finland 118 20.2 37/81 Maxillary/mandibular 402

Hill22(2006) UK 228 N/A 150/78 Mandibular 427

Fernandes23

(2010)

UK 613 N/A 250/363 Mandibular 676

N/Anot available

M3- Third molar.

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Table II. Risk Rate of Third-molar Extraction (teeth)

Authors Follow-

up

(yrs)

Mean

Age at

inception

(yrs)

Baseline

M3s

retained

Extracted

M3s

Analysis

unit

Cumulative

incidence

of

extraction

Annual

incidence

of

extraction

Fernandes23

(2010)

1 not

reported

676 37 teeth 0.05 0.05

Von

Wowern24

(1989)

4 20.3 130 49 teeth 0.38 0.09

Kruger21

(2001)

8 18.0 2652 790 teeth 0.30 0.02

Garcia9

(1989)

10 47 151 18 teeth 0.12 0.01

Venta1

(2000)

12 20.7 285 135 teeth 0.47 0.04

Venta25

(2004)

18 20.2 402 257 teeth 0.64 0.04

Mean 8.8

6.0

25.2

12.2

716

969.2

214.3

295.6

0.30 0.03

M3- Third Molar

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Table III. Subject level estimate of M3 extraction risk

Authors Follow-

up

(yrs)

Age at

inception

(yrs)

Number

of

Subjects

baseline

Number

of

Subjects

having an

extraction

Baseline

Third-

molars

Extracted

Third-

molars

Analysis

unit

Cumulative

incidence

of

extraction

Ann

Rela

risk

extr

Hill22

(2006)

5 Not

reported

228 71 427 Not

reported

subjects 0.31 0.06

Legend

Figure 1. Flow chart outlining the systematic review methodology

Table 1. Descriptive Statistics

Table II. Risk Rate of Third-molar Extraction (teeth)

Table III. Subject level estimate of M3 extraction risk

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Figure 1.

Records identified through

database searching

(n =44 )

Screening

Included

li

i

ilit

Identification

Additional records identified

through bibliographies

(n = 21 )

Records after duplicates removed

(n = 65)

Records screened

(n = 65 )

Records excluded

(Non English)

n=1

Full-text articles assessed

for eligibility

(n =64)

Full-text articles excluded,

(Retrospective,