orofacial pain ( ofp ) includes pains whose origin is below the orbitomeatal line , 
 above the neck and anterior to the ears and pain within the mouth . it can be a symptom of various disorders , 
 however the majority of ofp is due to dental causes ( for example , toothache ) and 
 facial trauma , and in most cases it is acute . the remainder is considered chronic 
 ofp , and temporomandibular disorders ( tmd ) represent one of the most common forms of 
 chronic ofp .
tmd is a collective term , for disorders characterized by joint pain , 
 masticatory muscle tenderness , joint noises and restricted jaw movements .
the 
 percentage of the population presenting with tmd is estimated at 3 - 4% , however up 
 to a quarter of the population may report the symptoms during the past month .
it has been suggested that there is a relationship between the removal of third 
 molars and the postoperative onset of temporomandibular joint pain / dysfunction . as 
 early as 1969 , greene et al .   reported that 
 48% of patients with tmd attributed the onset of their symptoms to a specific event , 
 including prolonged oral surgery procedures .
however there is equivocal evidence on 
 a relationship between tmd symptoms and third molars removal : while some studies 
 supported this finding [ 5 - 8 ] , others did not find any association [ 9 - 11 ] . 

these studies involved patient populations , university students , 
 health plan enrolees   and dental service enrolees . one study   involved cases 
 diagnosed in clinic and controls from dental health survey
. none of the above 
 studies were conducted in general population , i.e. they were all prone to selection 
 bias as not all people with ofp seek treatment and not everybody enrolled in health 
 and dental plans .
the aim of the current study was to investigate whether there was a relationship 
 between a history of third molar removal and the prevalence of orofacial pain in a 
 sample of the general population .
the study was a four year follow - up of the population survey conducted by macfarlane 
 et al . .
the original survey included 
 randomly selected participants aged 18 - 65 years registered with a general medical 
 practice in south east cheshire , north west england .
random selection ensured that 
 the study population could represent equally all genders , ages , ethnicities and 
 social class .
as general practice registers cover more than 99% of the population in 
 england ( http://www.statistics.gov.uk ) and access to most health service care is 
 through the general medical practitioner , the practice age - sex resister is a 
 convenient frame for a general population survey .
ethical approval for the study was granted by south cheshire local research ethics 
 committee .
sample size for the baseline survey was calculated using the results of a pilot study 
 using ofp prevalence estimate of 25% . 

every participant in the main survey who gave permission to be contacted again was 
 included in the follow - up survey ( only 3 participants of the baseline survey did not 
 wish to be contacted again ) .
each participant received a postal questionnaire , with follow - up of non - responders by 
 a reminder postcard , questionnaire and , if necessary , a short questionnaire and a 
 telephone call .
ofp was defined as present if participants during the past month 
 " had any pain in their face , mouth or jaws that has lasted for one day or 
 longer " .
body pain was defined as present if participants during the past month 
 " had any ache or pain in the body which has lasted for one day or longer " . 

deprivation was measured 
 by the townsend index , an area - based score derived from postcode sectors or wards 
 .
participants were also asked if they had their wisdom teeth removed and permission to 
 be contacted again .
in addition , participants were asked permission for their dental 
 records to be examined , and in case of positive reply , were asked to indicate the 
 name and address of their dentist .
data were extracted in duplicate ( both clinical examiners ) from 10 records 
 to investigate reliability .
one clinical examiner repeated data extraction from 10 
 dental records twice to investigate reproducibility .
the magnitude of association between third molar removal and ofp was described by the 
 relative risk ( rr ) .
rr here is a measure of the risk of ofp in one group compared to 
 the risk of ofp in another ( reference ) group .
a relative risk of one means there is 
 no difference between two groups in terms of their risk of ofp .
a relative risk of 
 greater than one or of less than one means that being exposed to a factor either 
 increases ( relative risk greater than one ) or decreases ( relative risk less than 
 one ) the risk of ofp .
the data were analysed using 
 stata 10 for windows ( statacorp , lp , usa , 2008 ) and spss 16.0 for windows ( spss 
 inc . , chicago , il , usa , 2008 ) statistical packages .
a total of 1680 persons ( 81% adjusted participation rate after excluding those who 
 were no longer registered with the practice , deceased or who were not able to 
 complete the questionnaire due to illness or disability or expressed a wish at 
 baseline not to be contacted again ) participated in the follow - up survey , and the 
 full study questionnaire was completed by 1510 participants .
the remainder completed 
 a short version of the questionnaire which did not include question on third molar 
 removal .
adjusted participation rate was higher in women ( 83% ) compared to men ( 77% ) 
 ( chi - square test p < 0.001 ) and in affluent areas ( 83% ) compared to deprived 
 areas ( 59% ) ( chi - square test p < 0.001 ) .
non - respondents were older ( mean age 49 
 years [ sd = 12 ] ) then non - respondents ( mean age 44 years [ sd = 13 ] ) ( t - test p < 
 0.001 ) . of those who completed the full questionnaire , 295 ( 19% ) reported ofp , 1202 ( 80% ) did 
 not report such pain and 13 ( 1% ) did not answer this question .
majority ( 60% ) of 
 self - reported ofp was chronic , i.e. lasted for more than 3 months .
the mean pain 
 severity was 4.8 on 10-point numerical analogues scale ( sd = 2.3 ) and 62% sought 
 advice on ofp from a health professional .
over half ( 873 , 58% ) of respondents did not report a history of perceived third molar 
 extractions , 77 ( 5% ) did not answer this question , giving 560 ( 37% ) who reported 
 third molar removal .
the majority of participants ( 1060 , 70% ) who completed the full questionnaire gave 
 permission for their dental records to be examined , and indicated the name and 
 address of their dentist .
eight hundred and sixty ( 81% ) participants were registered 
 with four main dental practices in the study area ; the remainder were registered 
 with dentists in the surrounding areas .
these distant practices were not visited , so 
 only these four main practices were included , and 806 ( 94% ) patient records were 
 found .
in addition , one practice in the surrounding area with 3 patient records was 
 used as a pilot site , giving total of 809 records .
median time of registration with 
 a dentist was 14 years ( range 1 day - 46 years ) prior to completing the 
 questionnaire .
there was an acceptable ( cohen 's kappa > 0.6 , p < 0.05 ) agreement when 
 reliability and reproducibility of information regarding third molars extracted from 
 dental records .
the minimum cohen 's kappa value was 0.61 , maximum 1.00 , median was 
 0.71 , indicating at least substantial agreement , according to classification by 
 landis and koch . to validate the answers in the questionnaire regarding perceived third molar removal , 
 this question was cross tabulated against the extractions recorded by dentists 
 ( table 1 ) .
of those who reported at least 
 one perceived extraction , 20 ( 37% ) had extractions recorded in dental records , while 
 for those who did not report history of extractions in the questionnaire , this 
 figure was 27 ( 6% ) .
all four third molars were present in 113 ( 25% ) of participants 
 who did not report extractions . only 9 ( 3% ) of participants who reported that they 
 had third molars removed had all four third molars present
. validity of self - reported third molar extractions information was missing for 33 participants .
participants who reported third molar extractions in the questionnaire were more 
 likely to report ofp ( adjusted relative risk [ rr ] 1.29 ) ; ( 95% confidence interval 
 [ ci ] 1.01 - 1.65 ) ( table 2 ) . when only 
 information from the dental records was used and participants with all four molars 
 present were compared to those with at least one extraction , the rr was 1.50 ( 95% ci 
 0.90 - 2.49 ) .
however when time since last extraction was investigated , the increase 
 was evident only in relatively recent extractions ( rr = 1.91 , 95% ci 1.10 - 3.32 ) 
 for people with third molar extraction less than eight and a half years ago , whilst 
 the number of third molars remaining did not show any particular pattern .
relationship between third molar extractions and orofacial pain 
 ( ofp ) 100 months was a median time since extraction and therefore 
 was chosen as a cut - off point .
this population - based epidemiological study has provided evidence that individuals 
 who report third molar extractions are more likely to report ofp .
when extraction 
 information was validated using dental records , this association was only found in 
 relatively recent extractions .
any dental intervention that alters the occlusion has the potential to alter the 
 position of the mandibular condyle in the mandibular ( glenoid ) fossa and predispose 
 to tmd symptoms .
the incidence of tmd 
 has been shown to rise after 19 years of age .
it has been suggested that this could 
 be attributed to occlusal changes as a consequence of teeth exfoliation and eruption 
 of permanent successors , or the eruption of third molars leading to overcrowded 
 dental arches .
third molar removal could lead to tmd development as a 
 consequence of the required surgery , which may necessitate wide mouth opening and 
 the application of relatively large forces to the posterior mandible .
traumatic 
 arthritis has been reported after third molar removal although the occurrence is 
 rare .
tmd patients with a history of 
 trauma or non - temporomandibular joint - related operations have reported higher 
 prevalence , severity and frequency of ofp than controls .
it has been 
 postulated that nerve damage in hard and soft tissues can cause sensitisation of 
 both peripheral and central neurons . 

hypothetically , the increased pain perception following surgical third molar removal 
 could tip the threshold balance toward tmd .
there are methodological issues which need to be considered when examining the study 
 results .
the study involves a sample of the population of one geographic area in the united 
 kingdom and therefore may not be representative .
while the overall participation 
 rate at follow - up was high , non - participants were more likely to be male , younger 
 and from lower socio - economic background .
nevertheless , these differences would only affect the comparisons in the present 
 study if the relationship between these factors and presence of ofp were different 
 in those subjects who participated compared with those who did not .
questionnaires were 
 posted together with a covering letter from the general medical practitioner 
 informing practice members of the practice participation in the study .
non - respondents were followed up by a postcard reminder , a further questionnaire , 
 and , if necessary , a short questionnaire and a telephone call .
although there was a statistically significant increase in risk ( 30% ) of ofp 
 associated with self - reported extractions , we did not find a statistically 
 significant association between at least one third molar extraction determined from 
 the dental records and ofp ( 50% increased risk ) .
firstly , there was less statistical 
 power when information from dental records was analysed , as not all participants who 
 completed the questionnaire had information from dental records .
however we have adjusted in 
 the statistical analysis in both cases for other potential risk factors such as 
 other body pain and psychological distress .
thirdly , it has been shown that that 
 there was good correspondence between subjective self - reports of well - defined oral 
 health conditions and clinical findings , for example the number of teeth and the 
 presence of dentures .
finally , there was 
 a statistically significant increase in risk among participants with more recent 
 extractions , which support the findings of huang and rue , who also found elevated 
 risk in more recent extractions . while the study has achieved high participation rate and acceptable reliability when 
 extracting information from dental records , several problems were encountered . 

although participants had reported third molar removal in the original 
 questionnaire , it may not be entirely accurate . for approximately half of all cases , 

third molars were marked as absent in the records but with no record of extraction . 

it was impossible to determine from the notes whether third molars marked as absent 
 in this way were : 1 ) congenitally absent ; 2 ) unerupted ; 3 ) had been extracted before 
 the origin of the notes .
this problem was accentuated in the older age groups , where 
 early dental records were not available .
in rare cases it was obvious that after early extraction of first 
 molars , third molars were being recorded
. in some cases charting of the tooth could 
 change several times throughout the notes .
better recording of dental notes would 
 help resolve some of these problems in primary dental care research .
in addition , 
 this study is a cross - sectional survey and therefore the associations we report are 
 not necessarily causal .
this research has shown that there is a weak relationship between self - reported 
 history of third molar removal and self - reported orofacial pain , and the depth and 
 detail of evidence is still inconclusive .
the authors are grateful to staff and patients of lawton house surgery , dental 
 practice of ar mellor & associates , canal street dental practice , moody 
 terrace dental practice and tdu miller dental practice in congleton , cheshire , 
 united kingdom for their help with the study .
d. 
 king , university of manchester , manchester , uk and mrs . c. mackie , manchester 
 dental school , manchester , uk , for help with access to dental records .
 abstractobjectivesthe aim of the current study was to investigate whether there was a 
 relationship between a history of third molar removal and the prevalence of 
 orofacial pain in a sample of the general population.material and methodsa survey was conducted in south east cheshire , united kingdom ( 81% 
 participation rate ) . 
 information was collected using postal questionnaires 
 ( n = 1510 ) and dental records ( n = 809).resultsparticipants who reported third molar extractions were more likely to report 
 orofacial pain ( rr = 1.29 ; 95% confidence interval [ ci ] 1.01 - 1.65 ) . 
 
 participants with a more recent history of extractions ( < 8 years ago ) as 
 recorded in dental records were more likely to report orofacial pain 
 compared to those who had all third molar present ( rr = 1.91 ; 95% ci 1.10 - 
 3.32).conclusionsthis research suggests that self - reported third molar removal is linked to 
 self - reported orofacial pain , however evidence from one study is not 
 sufficient to give an unequivocal answer . 
INTRODUCTION
MATERIAL AND METHODS
RESULTS
DISCUSSION
CONCLUSIONS
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS