Common risk factors for postoperative pain following the extraction of wisdom teeth

Abstract

The extraction of third molars is a common task carried out at dental/surgery clinics. Postoperative pain is one of the two most common complications of this surgery, along with dry socket. Knowledge of the frequent risk factors of this complication is useful in determining high-risk patients, planning treatment, and preparing the patients mentally. Since the risk factors for postoperative pain have never been summarized before while the risk factors for dry socket have been highly debated, this report summarizes the literature regarding the common predictors of postextraction pain. Except for surgical difficulty and the surgeon's experience, the influences of other risk factors (age, gender and oral contraceptive use) were rather inconclusive. The case of a female gender or oral contraceptive effect might mainly be associated with estrogen levels (when it comes to dry socket), which can differ considerably from case to case. Improvement in and unification of statistical and diagnostic methods seem necessary. In addition, each risk factor was actually a combination of various independent variables, which should instead be targeted in more comprehensive studies.

Full text

59
a major concern4,10,11. Besides, not all complications are rare.
There are frequent and debilitating complications as well, in-
cluding postoperative pain.
Pain is also one of the most common postoperative compli-
cations of extraction6,12-15 and might be caused by the release
of pain mediators from the injured tissues3,15. Pain is an im-
portant factor in clinical practice6,16 and could even discour-
age patients from seeking dental treatment15,17,18. It begins
after the anesthesia subsides and reaches its peak levels dur-
ing the rst postoperative day15,19,20. If dry socket or infection
occur, the onset of inflammation will complicate alleviation
of postoperative pain5,15,20-26.
In the setting of elective operations, such as third molar
removal, patients demand to know the risks, benefits and
postoperative quality of life of these procedures15,1 7,27. The
knowledge of the risk factors of postsurgical complications
has clinical implications in treatment planning, patient man-
agement and prognosis15,19,21,24,28-31. This essay briefly reviews
the most common risk factors of pain following third molar
removal.
I. Introduction
One of the most common procedures carried out in dental
clinics and the most frequent task done at oral and maxil-
lofacial surgery clinics is the extraction of wisdom teeth.
This procedure is frequently followed by complications in
the mandible1-3, including both iatrogenic (e.g., nerve injury,
bone fractures, etc.) and inflammatory ones, such as dry
socket, postoperative pain, delayed healing, postoperative
infection, hematoma, swelling, trismus, etc.2,4-6. Although the
overall
complication rate might be generally low, and most
complications are minor4,7-9, this surgery is so frequent that
the population’s morbidity of complications may be notice-
able; thus, identifying methods to control or reduce them is
REVIEW ARTICLE
Vahid Rakhshan
#22 Behruzi Alley, Karegar St. Tehran 14188-36783, Iran
TEL: +982166929055 FAX: +982166902923
E-mail: vahid.rakhshan@gmail.com
ORCID: http://orcid.org/0000-0002-9503-3133
This is an open-access article distributed under the terms of the Creative Commons
Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/),
which permits unrestricted non-commercial use, distribution, and reproduction in any
medium, provided the original work is properly cited.
CC
Common risk factors for postoperative pain following
the extraction of wisdom teeth
Vahid Rakhshan1,2
1Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences,
2Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran
Abstract (J Korean Assoc Oral Maxillofac Surg 2015;41:59-65)
The extraction of third molars is a common task carried out at dental/surgery clinics. Postoperative pain is one of the two most common complications
of this surgery, along with dry socket. Knowledge of the frequent risk factors of this complication is useful in determining high-risk patients, planning
treatment, and preparing the patients mentally. Since the risk factors for postoperative pain have never been summarized before while the risk factors
for dry socket have been highly debated, this report summarizes the literature regarding the common predictors of postextraction pain. Except for sur-
gical difculty and the surgeon’s experience, the inuences of other risk factors (age, gender and oral contraceptive use) were rather inconclusive. The
case of a female gender or oral contraceptive effect might mainly be associated with estrogen levels (when it comes to dry socket), which can differ
considerably from case to case. Improvement in and unication of statistical and diagnostic methods seem necessary. In addition, each risk factor was
actually a combination of various independent variables, which should instead be targeted in more comprehensive studies.
Key words:
Pain, Risk factors, Third molar, Extraction
[paper submitted 2014. 11. 16 / revised 1st 2014. 11. 25, 2nd 2014. 12. 4 / accepted 2014. 12. 11]
Copyright
Ⓒ
2015 The Korean Association of Oral and Maxillofacial Surgeons. All
rights reserved.
http://dx.doi.org/10.5125/jkaoms.2015.41.2.59
pISSN 2234-7550·eISSN 2234-5930

J Korean Assoc Oral Maxillofac Surg 2015;41:59-65
60
geries leave more painful sockets. However, Benediktsdóttir
et al.29 found that simply the root morphology and level of
impaction were correlated to postoperative pain; they did not
identify any impact of the actual surgery time29. Grossi et al.38
also did not nd a signicant relationship between the elapsed
time of surgery and the level of postoperative discomfort.
Seymour et al.40 stated that the postoperative pain level might
not be dependent upon the operator or the extent of surgi-
cal trauma as estimated by operating time and radiographic
score. On the other hand, Oikarinen35, Garcia Garcia et al.36,
Haraji and Rakhshan15, and Yuasa and Sugiura37 found that
more difcult operations were more painful. The release of
more inflammatory factors and proximity to the nerve might
produce more intense pain in some difcult cases. This pain
might shift to paresthesia or anesthesia in cases with direct
injury to a nerve34. It should be noted that according to recent
research, radiographic indicators alone (i.e., Winter, Pell and
Gregory, Pederson)14,41-43 cannot totally identify the extent of
the difficulty of surgery6,13,29,34,44,45. Additionally, not all the
difculty determinants are necessarily prognostic factors for
complications46. Therefore, better methods should be used to
estimate surgical difculty, or the latent variables should be
assessed independently instead31.
3. The operator’s expertise
An experienced surgeon might carry out a cleaner, less
traumatic and yet faster operation than someone new to the
procedure. Additionally, patients might trust experienced
clinicians more. These factors (trauma, duration of surgery
and anxiety) can play important roles in inducing complica-
tions8,12,22,28-30,47-53. Therefore, expert clinicians might obtain
better results8,12,34,48-51,54-56. However, the evidence is contro-
versial, as some authors did not denote a link between the
surgeon’s skill and the patient’s postoperative pain29. Some
of these “experience levels” were actually different terms of
undergraduate study and thus indicated little about the sur-
geon’s expertise57. A surgeon’s experience might reduce the
postoperative pain only within a short period after the surgery
but may have no influence on the duration or intensity of
longer pains12. This discrepancy might contribute to the con-
troversial result depending on the time at which the pain is
assessed.
4. Tobacco smoking
Smoking might increase pain by reducing blood supply in
II. Materials and Methods
The internet was searched to find relevant articles pub-
lished before July 2014 regarding the risk factors of postex-
traction pain. The search engines used were Google Scholar,
Pubmed/MEDLINE, ISI Web of Science, and Scopus. The
keywords were as follows: “third molar”, “wisdom tooth”,
“wisdom teeth”, “extraction”, “removal”, “postoperative
pain”, “postsurgical pain”, “risk factor”, “prognostic factor”,
and “predictor”.
More than 800 unique articles were initially found. All
these article “titles” were reviewed to narrow down the scope
of the search to more relevant articles, according to the eligi-
bility criteria of the presentation of results of original research
or short communications regarding pain perceived after the
extraction of the third molars before July 2014; the time span
was open to all articles published before this date. The ar-
ticles of interest were collected and evaluated. The reference
lists of the located articles were also consulted to identify ad-
ditional relevant reports. Each article or abstract was read at
least twice, and the proper information was aggregated. Other
more general topics were also researched for the sake of dis-
cussing the matters.
III. Results
1. Oral hygiene
The effects of hygiene maintenance on postoperative pain
have not been widely assessed except in a few English and
non-English articles. Sáez Cuesta et al.32 extracted 100 wis-
dom teeth and found that patients with poor oral hygiene be-
fore surgery experienced higher pain levels during the rst 6
postoperative hours. Peñarrocha et al.5 explored 190 impacted
third molars and found that pain increased with increasing
lack of care to hygiene. Larrazábal et al.33 asserted that pain
increases were correlated with less brushing before surgery
and also during the rst postoperative week.
2. Difficulty of the extraction procedure and trauma
An association between different aspects of surgical dif-
culty (such as the impaction level and angle, extent of bone
removal or length of surgery) and pain or paresthesia has
been assessed in most previous studies6,14,15,28,29,34-37 with a few
exceptions12,38. Lago-Méndez et al.13, Pedersen14, Baqain et
al.39, and de Santana-Santos et al.6 stated that lengthier sur-

Risk factors for postextraction pain
61
conflicting results4,12,15,37,38,46,57,72,73. Capuzzi et al.12 reported a
greater extent of pain in males. Yuasa and Sugiura37 declared
that postoperative swelling and morbidity but not pain might
be greater in females. de Santana Santos et al.41 observed
signicantly more pain in females only during the rst 4 and
12 postoperative hours, but at the 24th and 48th postopera-
tive hours, the greater pain intensity in women did not reach
a level of signicance41. This controversy might be rooted in
various missing latent variables (e.g., hormonal, psychologi-
cal or genetic differences, etc.).
6. Oral contraceptives
Contraceptive consumption might be less likely to affect
or confound pain-related results4,12,38,74, although a few stud-
ies have reported on its positive role in this regard as well75.
Regardless, modern contraceptive pills contain considerably
lower doses of estrogen and therefore have a reduced role
compared with those of the past34,76.
7. Age
The production and process of sensory stimuli might be
influenced by aging77-79. The elderly could be at higher risk
of complications, such as severe pain and sensory distur-
bances4,12,38,80,81, possibly because of this group’s poorer heal-
ing potential, denser bones and completed dental roots4,28,34,82.
Some investigators have observed significant deteriorating
effects of aging on pain9,12,28,81. Blondeau and Daniel34 report-
ed increased neurosensory problems in patients older than
24 years. However, other studies have not identied such a
role29,39,83. Adeyemo et al.84 and Bui et al.4 found no signi-
cant association between age and complications. Yuasa and
Sugiura37 reported a signicant influence of age on swelling
and collective postprocedural morbidity but not pain. Grossi
et al.38 observed a significant association between patients
older than 23 years and merely severe trismus but not pain
either reported subjectively by the patients or implied by the
number of painkillers taken. Benediktsdóttir et al.29 found no
correlation between age and discomfort, despite their find-
ing indicating that surgery could last signicantly longer in
older patients. In the study of Capuzzi et al.12, younger par-
ticipants reported less pain in the rst postextraction day, but
the number of painkillers taken was not correlated with age.
Haraji and Rakhshan15 studied younger patients and showed
that when the effects of the operation difculty, smoking and
gender were not controlled for, younger people might show
the alveolar socket33,49. Meechan et al.49 asserted that heavy
smokers have a high chance of poor lling of their extraction
sockets with blood. They also found a correlation between
this phenomenon measured immediately after the extraction
and painful sockets49. Nevertheless, to the author’s knowledge,
only certain authors have found a significant link between
postoperative pain and smoking33. The only relationship that
was found was between the pains perceived on the rst post-
surgical day and with postsurgical smoking33. The same study
and many others did not correlate preoperative smoking with
postsurgical pain in their total samples4,12,15,33,38,39. In the stud-
ies of Grossi et al.38 and Heng et al.2, a greater amount of pain
perceived by females was associated with smoking2,38. Grossi
et al.38 suggested that smoking only affects the perception of
pain by females. However, Haraji and Rakhshan15 adjusted
for the role of gender while assessing the effect of smoking
on pain. In their analysis, smoking had no signicant effects
on postoperative pain on the rst or third postoperative days
or in general. They also assessed the interaction of gender
and smoking, and no signicant results appeared15.
5. Gender
Gender is a crucial variable that should be considered when
designing and analyzing the findings of studies in all areas
and at all levels of biomedical and health-related research38.
This issue has been ignored in the past and has gained popu-
larity only in the last few decades58. The association between
clinical pain and gender is not a simple one, but females have
reported more frequent pains compared to men in terms of
various anatomic regions, neuropathic conditions, chronic
musculoskeletal pains, temporomandibular pains, facial
pains, toothaches, etc.58-64. Postoperative pain studies lack
standardization and are at some points conflicting; however,
in general, it could be inferred that women might experi-
ence pain more often and to a greater extent than men58,65-68.
Although the research in this regard is rather scarce in terms
of postextraction pain by gender, the aforementioned results
could imply that females might have a higher sensitivity to
pain stimuli perhaps due to psychosocial factors (mood, sex
role beliefs, pain coping strategies, and pain-related expectan-
cies), catastrophizing and sex hormones38,69,70. Also the thin-
ner mandible of women might render them more vulnerable
to pain and some complications after dental procedures6,71.
Some authors have reported more intense postsurgical
pains28,29,40, longer symptom recovery times17,47 or neuro-
sensory deficit in females34. However, many others found

J Korean Assoc Oral Maxillofac Surg 2015;41:59-65
62
tential factor might likely be a real risk factor (Table 1), the
trauma of surgery and experience of the surgeon were more
likely to be causative or risk factors of pain. High levels of
estrogen were not necessarily a risk factor for pain. Evidence
suggesting a higher incidence of postextraction pain in fe-
males was outnumbered by reports that refuted such an as-
sociation. The effect of age remained inconclusive. Although
only a few studies regarding the effect of oral hygiene on
postoperative pain exist, it was shown to be effective in that
regard as well. There were at least three obstacles for detect-
ing possible links between pain and risk factors: consumption
of painkillers and antibiotics by the patients after surgery,
which act as efficient confounders15,20,25, as well as poorer
statistical approaches, and confusion of pain caused by a
dry socket or infection with pain caused only by the surgery
and also with discomfort. Except for a few essays15, almost
signicantly greater pain. However, when these factors were
adjusted for, younger patients showed a borderline signifi-
cantly greater amount of pain only for the rst postoperative
day but not on the third postsurgical day15. The narrow range
of patient ages could mask such an effect, since third molar
extraction is usually indicated in young ages38, and debilitat-
ing effects of age might appear in older ages79. Some authors
have advocated the removal of impacted molars in young
adults to avoid severe or permanent sequelae9,34,81. Nonethe-
less, if the assumption is not confirmed, early prophylactic
extraction of wisdom teeth, which is common in Europe and
America, might not be justiable38,84,85.
IV. Conclusion
Based on the number of studies agreeing that a certain po-
Table 1. A summary of studies supporting or not supporting the role of the searched risk factors (some studies fit both criteria)
Factor Supporting study Studies failing to support the risk factor
Oral hygiene
Operation difculty, duration or trauma as
risk indicators of postoperative pain, sensory
disruption or discomfort
The expertise of the surgeon
Smoking
Gender
Age
Sáez Cuesta et al.32
Peñarrocha et al.5
Larrazábal et al.33
Lago-Méndez et al.13
Pedersen14
Baqain et al.39
de Santana-Santos et al.6
Oikarinen35
Garcia Garcia et al.36
Haraji and Rakhshan15
Yuasa and Sugiura37
–
Meechan et al.49
Larrazábal et al.33
Grossi et al.38
Heng et al.2
In favor of female gender
Phillips et al.28
de Santana Santos et al.41
Benediktsdóttir et al.29
Seymour et al.40
In favor of male gender
Capuzzi et al.12
Osborn et al.9
Bruce et al.81
Blondeau and Daniel34
Capuzzi et al.12
Phillips et al.28
–
Capuzzi et al.12
Benediktsdóttir et al.29
Grossi et al.38
Seymour et al.40
Benediktsdóttir et al.29
Capuzzi et al.12
Bui et al.4
Haraji and Rakhshan15
Larrazábal et al.33
Capuzzi et al.12
Grossi et al.38
Baqain et al.39
Eshghpour et al.57
Abu Younis and Abu Hantash72
Barbosa-Rebellato et al.73
Carvalho and do Egito Vasconcelos46
Haraji and Rakhshan15
Yuasa and Sugiura37
Bui et al.4
Grossi et al.38
Capuzzi et al.12
Akadiri et al.83
Adeyemo et al.84
Bui et al.4
Yuasa and Sugiura37
Grossi et al.38
Benediktsdóttir et al.29
Capuzzi et al.12
Haraji and Rakhshan15
Baqain et al.39
Vahid Rakhshan: Common risk factors for postoperative pain following the extraction of wisdom teeth. J Korean Assoc Oral Maxillofac Surg 2015

Risk factors for postextraction pain
63
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evaluating the risk factors for postoperative pain. Future
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with each other. Therefore, analyses not accounting for the
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consider a broader clinical picture31.
Conflict of Interest
No potential conflict of interest relevant to this article was
reported.
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