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Received: 28 June 2021 Accepted: 22 February 2022
DOI: 10.1111/eos.12862
ORIGINAL ARTICLE
Retained dental roots of adults: A nationwide population study
with panoramic radiographs
Sanna Koskela1,2Miira M. Vehkalahti1Anna L. Suominen3,4,5
Sisko Huumonen3,6,7Irja Ventä1
1Department of Oral and Maxillofacial
Diseases, University of Helsinki, Helsinki,
Finland
2Department of Oral and Maxillofacial
Diseases, Helsinki University Hospital,
Helsinki, Finland
3Institute of Dentistry, University of Eastern
Finland, Kuopio, Finland
4Department of Oral and Maxillofacial
Diseases, Kuopio University Hospital,
Kuopio, Finland
5Department of Public Health and Welfare,
Finnish Institute for Health and Welfare,
Helsinki, Finland
6Diagnostic Imaging Center, Kuopio
University Hospital, Kuopio, Finland
7Research Unit of Oral Health Sciences,
University of Oulu, Oulu, Finland
Correspondence
Irja Ventä, Department of Oral and
Maxillofacial Diseases, Faculty of
Medicine, P.O. Box 41, FI-00014 University
of Helsinki, Finland.
Email: irja.venta@helsinki.fi
Funding information
Field surveys in 2000 were funded by the
Finnish Institute for Health and Welfare
(THL), the Finnish Dental Society
Apollonia, and the Finnish Dental
Association.
Abstract
The aim of this study was to assess the occurrence and nature of retained dental
roots and their associations with demographics in the Finnish adult population. From
the cross-sectional nationwide Health 2000 Survey of the Finnish population aged
30 years and older, 6005 participants with clinical oral examination and panoramic
radiographs were included. Occurrence and characteristics of all retained dental roots
were examined. Statistical analyses included χ2, Kruskal–Wallis and Mann–Whitney
U tests, and SAS-SUDAAN calculations. The mean age of the 6005 participants (46%
men and 54% women) was 53 (SD 14.6) years. At least one retained dental root was
observed in 13% (n=754) of the participants. The 1350 retained roots included 461
(34%) roots retained entirely in bone and 889 (66%) partly in bone. The most common
location of a retained dental root was the third molar region. Occurrence of retained
roots partly in bone was associated with male sex and lower education. Occurrence
of retained third molar roots entirely in bone was associated with female sex, younger
age, higher education, and living in a city. Among all retained dental roots, the pre-
ponderance of third molars emphasized the demanding nature of extracting the third
molar in women.
KEYWORDS
health surveys, panoramic radiography, third molar, tooth extraction, tooth root
INTRODUCTION
Retained dental root is a diagnosis listed in the International
Classification of Diseases 10th Revision (ICD-10) as K08.3
[1]. Such roots occur when the crown has disappeared
either during extraction or due to caries and the roots
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original
work is properly cited.
©2022 The Authors. European Journal of Oral Sciences published by John Wiley& Sons Ltd on behalf of Scandinavian Division of the International Association for Dental Research.
may locate inside the bone or may remain visible during
clinical oral examination. The presence of retained roots is
well-documented in numerous studies of selected samples at
dental care units. However, the occurrence of retained roots
in population-based studies is reported only for clinically
visible root remains. The reason for this is that panoramic
Eur J Oral Sci. 2022;e12862. wileyonlinelibrary.com/journal/eos 1of8
https://doi.org/10.1111/eos.12862
2of8 KOSKELA ET AL.
radiographs are rarely obtained in population studies. In
a nationwide population-based study from Finland in the
1980s, the prevalence of clinically visible retained dental
roots was 15%, regardless of tooth type [2]. In that study of
7168 participants, the prevalence of retained roots was twice
as great in men as in women.
Two earlier radiographic studies have focused on retained
roots in larger samples. In a radiographic study from the
1960s, conducted at two university clinics in the USA on 2189
and 1685 participants, the occurrence of retained dental roots
in edentulous and dentate participants together was 7.6% at
age 21 and 37.8% at age 61 years or older [3]. Most of these
roots were located in the posterior region of the jaws, and more
were in the maxilla than in the mandible. An associated radi-
olucency was detected in 81% of the roots exposed to the oral
cavity [3]. In another radiographic study from the 1960s, per-
formed on 2000 Australian patients referred for removal of
retained roots, 16.7% of the roots were exposed to the mouth,
while 83.3% were located deeper [4]. However, these studies
did not differentiate between tooth types or by their presence.
There have been no larger studies on retained dental roots, and
before the present study, none has used a representative sam-
ple with radiographs.
The aim of this study was to assess the occurrence and
nature of retained dental roots and their associations with
demographic features in the Finnish adult population. The
underlying question is whether the examination of retained
dental roots may reveal areas requiring attention in patient
care.
MATERIALS AND METHODS
Study design and participants
This study was part of the Health 2000 Survey (BRIF8901,
Bioresource Research Impact Factor) organized in
2000−2001 by the Finnish Institute for Health and Wel-
fare [5]. This study is reported according to the Strengthening
the Reporting of Observational Studies in Epidemiology
(STROBE) guidelines. The survey was a nationally repre-
sentative study that used a stratified two-stage cluster sample
of 8028 inhabitants aged 30 years and older [6,7]. The
sampling frame was regionally stratified according to five
university hospital regions. From each of these stratums, 16
health center districts were sampled as clusters (n=80). The
final sampling units (inhabitants aged 30 years and older)
were selected by systematic random sampling from each
cluster. This design was used to obtain a sample that properly
reflected the main demographic distribution of the Finnish
population.
From the sample, a total of 6335 (79%) individuals par-
ticipated in the clinical oral health examination [8]. Data
on participants’ age, sex, and area of residence (city, town,
or countryside) were extracted from the Population register
of Finland. The level of education (basic, intermediate, or
higher) was determined from an interview preceding the clin-
ical phase [7].
The participants (n=6335) in the clinical oral examina-
tion and the nonparticipants (n=1693) did not differ by sex
(P=0.98). However, the participants were younger, were
less likely to live in a city, and had higher level of education
than the nonparticipants (P<0.001; Mann–Whitney U and
χ2tests).
Clinical and radiographic examination
The clinical oral health examination was performed in a
portable dental unit by five calibrated dentists with assisting
nurses [8]. All teeth, including third molars, were examined
and a tooth was recorded as present if it was clinically visible
or could be probed. A tooth was recorded as a retained den-
tal root if more than half of all vertical surfaces of the crown
were missing [8]. Quality assurance of clinical examinations
included 2 weeks of training before commencement of the
survey and both repeated and parallel measurements spread
evenly throughout the field stage of the survey [8]. Related to
dental status by tooth, consistency of parallel measurements
with the reference dentist showed agreement in 93% of teeth,
with a kappa value of 0.87 (95% CI 0.84–0.89) [8]. A partic-
ipant’s number of clinically recorded teeth was used to cat-
egorize the participants as being either clinically dentate or
edentulous.
Immediately after the clinical oral examination of the 6335
individuals, panoramic radiographs were taken of 6115 volun-
tary participants. Digital panoramic radiography (Planmeca
2002 CC Proline) was performed with values of 58–68 kV
and 4–10 mA depending on participant’s size. After exclu-
sion of images that were inadequate in the third molar region,
6005 radiographs remained and were included in the analy-
sis. The 110 participants whose panoramic radiographs were
excluded, did not differ by sex from those included (P=0.85;
χ2test). However, they had less teeth in the clinical oral exam-
ination than the included participants (P<0.001; Mann-
Whitney U test).
The included participants (n=6005) in the radiographic
examination and the excluded or nonparticipants (n=2023)
did not differ statistically significantly by sex (P=0.06).
However, the included participants were younger, were less
likely to live in a city (P=0.003) and had higher level of edu-
cation than the nonparticipants (P<0.001; Mann–Whitney U
and χ2tests).
The radiographic occurrence of permanent and deciduous
teeth and their condition (tooth status, see below) were deter-
mined by three specialists in oral radiology. The specialists
RETAINED ROOTS OF ADULTS 3of8
were trained and calibrated beforehand [8]. For the interex-
aminer reliability at training stage, concerning the readability
of the radiograph the same interpretation was reported for
98% of the cases with a kappa value of 0.96 [8]. In the actual
study, intraexaminer diagnostic quality was monitored by
having the same radiologist re-examine an earlier image
taken a day before or earlier, for every 30th radiograph [8].
Tooth status was classified as missing, impacted, root partly
embedded in bone, root wholly embedded in bone, implant,
caries, or none of the above (such as a healthy tooth) [7]. The
criteria described above were used to determine the number
of each tooth present in the radiographs.
Statistical analysis
For greater generalizability and comparability of the results,
weighting coefficients calculated by Statistics Finland were
used to correct effects of nonresponse and oversampling peo-
ple aged 80 years or older [8]. When the observational unit
was a participant, sampling weights, clusters, and stratums
were used in the analysis. SAS-Callable SUDAAN software
version 11.0.3. was used to allow for the complex sam-
pling method and to obtain weighted estimates (with 95%
confidence intervals) of the occurrence of participants with
retained roots representative of all Finns aged 30 years and
older. All routine statistical analyses were performed with
IBM SPSS Statistics version 27.
Participants with all types of retained roots were first ana-
lyzed together, followed by participants with retained roots
entirely in bone and partly in bone. After examination of the
number of retained roots, it was also necessary to categorize
the participants as those with retained roots of third molars
and those with retained roots of other teeth. Participant
age was categorized as 30−39, 40−49, 50−59, 60−69, and
70 years or older. Differences among various subgroups
were evaluated using χ2test for frequencies and Mann–
Whitney U or Kruskal–Wallis tests for means of independent
groups.
Ethical considerations
This research was conducted in full accordance with ethical
principles such as those of the World Medical Association
and the Declaration of Helsinki. Participants provided signed
informed consent and participated in the study entirely on
a voluntary basis. Ethical approvals for the examinations in
2000 were obtained from the Ethics committee of the National
Public Health Institute and the Ethics committee of Epidemi-
ology and National Health in the Hospital District of Helsinki
and Uusimaa. A safety license was granted by the Radiation
and Nuclear Safety Authority of Finland (No.: 4969/L1/00).
The present study was approved by the Finnish Institute for
Health and Welfare.
RESULTS
Of the 6005 participants in the radiographic examination, 46%
were men and 54% women. Their mean age was 53 years (SD
14.6; median 51; range 30−97 years).
In the 6005 panoramic radiographs, at least one retained
dental root was found in 13% (n=754) of the participants,
more often in men than women (14% vs. 11%; χ2=9.21;
df =1; P=0.002) (Table 1). The mean age of the 754 partic-
ipants with retained roots was 57 years (SD 14.3; median 55;
range 30−95 years).
Participants with retained dental roots were older than
those without such roots (57 vs. 52 years; P<0.001, Mann–
Whitney U test) (Table 2). Retained dental roots entirely
in bone occurred more frequently among women than men
(65% vs. 35%), while retained dental roots partly in bone pre-
vailed in men (71% vs. 29%; χ2=93.07; df =1; P<0.001)
(Table 2). Participants with retained dental roots had a lower
level of education and were less likely to live in a city than
those without such roots (Table 2). Among the participants
recorded clinically as edentulous (n=824), retained roots
were found in 13% (Table 2).
Number of retained roots
Most participants with retained roots (84%, n=635) had
one or two retained dental roots; the highest number in
a participant was 22 roots. The total number of retained
dental roots counted over the 6005 radiographs was 1350;
more were in the maxilla than the mandible (53% vs. 47%;
χ2=13.49; df =1; P<0.001). Among all tooth-like elements
seen in panoramic radiographs, 1.2% comprised roots only
(Figure 1). The most common location of a retained dental
root was the molar region of either jaw, particularly the third
molar region. The third molars accounted for 20% (n=268)
of all retained dental roots. When the two most common tooth
types accounting for retained dental roots were compared
(Figure 1), the proportion of third molar retained roots among
all third molar teeth present in the radiographs was larger than
that of the first molar roots (4.7% vs. 1.9%; χ2=116.9; df =1;
P<0.001).
From the 1350 retained dental roots in panoramic radio-
graphs, 461 (34%) were retained entirely in bone while the
remaining 889 (66%) were partly in bone. Among the 461
retained roots entirely in bone, the most common location in
the mandible was the third molar region (58%, n=117), and
in the maxilla, the first molar region (34%, n=87). When
both jaws were analyzed together, retained roots entirely in
4of8 KOSKELA ET AL.
TABLE 1 Distribution of the 754 participants with retained roots classified according to sex
Total N Participants with retained roots
Men/Women Men Women Both combined
Age(years) N/N n % (95% CI) n % (95% CI) n % (95% CI)
30-39 653/689 53 8 (6; 10) 38 6 (4; 8) 91 7 (6; 8)
40-49 703/786 98 14 (11; 17) 77 10 (8; 12) 175 12 (10; 14)
50-59 647/692 95 15 (12; 18) 79 11 (9; 13) 174 13 (11; 15)
60-69 418/497 69 17 (13; 21) 84 17 (14; 20) 153 17 (15; 19)
≥70 336/584 70 21 (17; 25) 91 16 (13; 19) 161 18 (16; 21)
Total 2757/3248 385 14 (13; 15) 369 11 (10; 12) 754 13 (12; 14)
The denominator for the percentage calculations is the number of men or women or both in the age category. Percentages are weighted values with their 95% confidence
intervals (CI) making the estimates representative of the Finnish population aged 30 years and older.
FIGURE 1 The proportion of retained dental roots (n=1350) according to tooth type as observed in 6005 panoramic radiographs. The
number of teeth observed indicates that many third molars are congenitally missing or have been extracted
bone were more common in the third molar region than in
other tooth regions (57% vs. 29%), while retained dental roots
partly in bone occurred more often related to other teeth than
the third molars (71% vs. 43%; χ2=75.74; df =1; P<0.001).
Participants with third molar roots
Participants with retained roots of third molars alone were
younger than participants with retained roots also in other
dental areas (mean ages 52 vs. 58 vs. 58 years, respectively,
in Table 3; Kruskal-Wallis test =27.12; df =2; P<0.001).
Retained roots of teeth other than third molars were accu-
mulated more often among older than younger age groups
(Table 3).
The prevalence of retained roots inside the bone was
twice as great in women than men (Table 4). Participants
with retained roots of third molars entirely in bone were
younger, had higher level of education and were more likely
to live in cities than participants with retained roots of other
teeth in bone (Table 4). Most participants (91%, n=357)
with retained roots in bone had one or two such roots
(Table 4).
DISCUSSION
The aim of this study was to assess the occurrence and nature
of retained dental roots and their associations with demo-
graphic features in the Finnish adult population. The main
finding was that the third molar region was the most frequent
location for a retained dental root, both for all retained roots
and for those retained entirely in bone. In addition, retained
roots of third molars entirely in bone occurred more often
in women than men. These findings add a new aspect to the
extensively investigated third molar tooth.
RETAINED ROOTS OF ADULTS 5of8
TABLE 2 Distribution of selected demographic and clinical characteristics according to the occurrence of retained dental roots among 6005
participants aged 30 years and older
Retained roots: Participants with
At least one root entirely in
bonean=392
Only roots partly in bone
n=362 No retained roots n=5251
Variable Levels n % (95% CI) n % (95% CI) n % (95% CI)
Age group (years) 30–39 41 10 (1; 19) 50 14 (4; 24) 1251 24 (22; 26)
40–49 69 18 (9; 27) 106 29 (20; 38) 1314 25 (23; 27)
50–59 84 23 (14; 32) 90 26 (17; 35) 1165 24 (22; 27)
60–69 96 25 (16; 34) 57 16 (7; 26) 762 14 (12; 17)
≥70 102 24 (16; 32) 59 15 (6; 24) 759 13 (11; 15)
SexcMen 134 35 (27; 43) 251 71 (65; 77) 2372 47 (45; 49)
Women 258 65 (59; 71) 111 29 (21; 37) 2879 53 (51; 55)
Educationc,d Higher 89 23 (14; 32) 49 14 (4; 24) 1576 30 (28; 32)
Intermediate 93 24 (15; 33) 127 35 (27; 43) 1708 33 (31; 35)
Basic 209 53 (46; 60) 185 51 (44; 58) 1947 37 (35; 39)
Area of residencecCity 214 55 (48; 62) 190 53 (46; 60) 3259 62 (60; 64)
Town 69 18 (9; 27) 53 15 (5; 25) 737 14 (12; 17)
Countryside 109 27 (19; 35) 119 32 (24; 40) 1255 24 (22; 26)
Clinical dentitionc,e Dentate 292 77 (72; 82) 355 99 (98; 100) 4518 87 (86; 88)
Edentulous 98 23 (15; 31) 5 1 (0; 3) 721 13 (11; 16)
No. of roots/ personc1310 79 (75; 83) 218 60 (55; 65) 0
247 12 (9; 15) 60 17 (13; 21) 0
3-22 35 9 (6; 12) 84 23 (19; 27) 0
Mean age (95% CI) Years 58.5 58; 61 53.3 53; 55 51.9 51; 52
The denominator in percentage calculations is the number of people with the given retained root condition. Percentages are weighted values with their 95% confidence
intervals (CI) making the values representative for the Finnish population aged 30 years and older.
aIn addition to at least one retained root entirely in bone, 26 of these participants also had retained roots located partially in bone.
bP<0.001, Kruskal–Wallis test.
cP<0.001, χ2test.
dLevel of education was not available for 22 participants.
eClinical number of teeth was not available for 16 participants.
A limitation of the study was that our data were two
decades old. Even so, we decided to describe the retained
dental roots of this unique population having data from
panoramic radiographs, as so far, no such studies have been
published. We presume that the prevalence of retained roots
has not changed much during the 20 years. Another limitation
of our study is the accuracy of the panoramic radiograph
in detecting structures, especially in the anterior regions
of both jaws and the maxilla [9]. However, in our study,
the specialists in oral radiology interpreting the panoramic
radiographs were calibrated beforehand and repeated assess-
ments were made during reading [8]. A third limitation of
our study was that the cross-sectional data did not include
information on the history of the teeth recorded as retained
roots, such as the duration of being a retained root, the
time since extraction, the experience of the clinician who
extracted the tooth, or the method of anesthesia used during
extraction. The etiology of retained roots has been alluded
to in an Australian study on incomplete exodontia, where
89% of the 2000 patients had undergone the extraction more
than 2 years ago (some up to 50 years ago) and only 22.5%
of retained roots had caused symptoms or any demonstrable
pathology [4].
The initial, nationally representative sample (n=8028)
were those who were invited to take part in the survey. Among
these, 79% participated in the clinical oral examination and
76% in the panoramic radiography. Due to this exceptionally
high response rate and the study design, analyzed samples can
be considered nationally representative.
Among all teeth, it was surprising to observe the prepon-
derance of retained third molar roots. In contrast, an earlier
study from the 1960s showed that the maxillary molar region
is the most frequent location for all types of retained roots
[3]. A detailed study from 1981 showed that in edentulous
jaws, the bicuspid and first molar regions in the maxilla pre-
dominate [10]. The difference between our findings and those
of earlier studies may depend on the general improvement of
oral and dental health since the 1960s. Consequently, among
6of8 KOSKELA ET AL.
TABLE 3 Distribution of the 754 participants with retained dental roots classified into three groups according to the tooth types affected
Participants with retained roots of
Age group
(years)
Third molars alone Both types Other teeth alone Total
n % (95% CI) N % (95% CI) n % (95% CI) n
30–39 46 49 (39; 59) 3 3 (0; 7) 42 48 (38; 58) 91
40–49 41 23 (17; 29) 18 11 (6; 16) 116 66 (59; 73) 175
50–59 33 19 (13; 25) 15 9 (5; 13) 126 72 (65; 79) 174
60–69 26 17 (11; 23) 17 11 (6; 16) 110 72 (65; 79) 153
≥70 26 16 (10; 22) 13 8 (4; 12) 122 76 (69; 83) 161
Total 172 23 (20; 26) 66 9 (7; 11) 516 68 (65; 71) 754
The denominator for the percentage calculations is the number of people in the age category. Percentages are weighted values with their 95% confidence intervals (CI)
making the estimates representative of the Finnish population aged 30 years and older
TABLE 4 Distribution of selected demographic and clinical characteristics among the 392 participants with retained dental roots inside the
bone classified into three groups according to the tooth types affected
Participants with retained roots inside the bone
Third molars alone
n=131 Both types n=17 Other teeth alone n=244
Variable n % (95% CI) n % (95% CI) n % (95% CI)
Age groupb(years) 30–39 37 28 (20; 36) 0 0 4 2 (0; 4)
40–49 34 26 (18; 34) 1 6 (0; 17) 34 14 (10; 18)
50–59 23 19 (12; 26) 4 26 (5; 47) 57 25 (20; 30)
60–69 17 13 (7; 19) 6 36 (13; 59) 73 30 (24; 36)
≥70 20 14 (8; 20) 6 32 (10; 54) 76 29 (23; 35)
SexcMen 39 32 (24; 40) 425 (4; 46) 91 38 (32; 44)
Women 92 68 (60; 76) 13 75 (54; 96) 153 62 (56; 68)
Educationb,e Higher 49 38 (30; 46) 1 7 (0; 19) 39 16 (11; 21)
Middle 42 32 (24; 40) 0 0 51 21 (16; 26)
Basic 40 30 (22; 38) 16 93 (81; 100) 153 63 (57; 69)
Area of residencedCity 76 59 (51; 67) 10 60 (37; 83) 128 53 (47; 59)
Town 23 17 (11; 23) 16 (0; 17) 45 18 (13; 23)
Country 32 24 (17; 31) 634 (12; 57) 71 29 (23; 35)
Clinical dentitionb,f Dentate 117 91 (86; 96) 11 69 (47; 91) 164 69 (63; 75)
Edentate 14 9 (4; 14) 6 31 (9; 53) 78 31 (25; 37)
No. of roots in bone/
personb
1118 90 (85; 95) 0 0 192 79 (74; 84)
2 8 6 (2; 10) 949 (25; 73) 30 13 (9; 17)
3-11 54 (1; 79) 851 (27; 75) 22 8 (5; 11)
Mean ageaYears 50.8 (48; 53) 64.8 (60; 70) 62.3 (61; 64)
The denominator in percentage calculations is the number of people with the given retained root condition. Percentages are weighted values with their 95% confidence
intervals (CI) making the values representative for the Finnish population aged 30 years and older.
aP<0.001, Kruskal–Wallis test.
bP<0.001, χ2test.
cP=0.270, χ2test.
dP=0.485, χ2test.
eLevel of education was not available for one person.
fClinical number of teeth was not available for two persons.
RETAINED ROOTS OF ADULTS 7of8
the few extracted teeth the third molar may be the most fre-
quently extracted tooth with root fragments left behind, either
purposefully or iatrogenically.
Our finding on the preponderance of the third molar root
retention suggests that extraction of this tooth is a demanding
procedure. Therefore, we wanted to determine whether there
is any difference between retained roots of the two most com-
mon groups of retained roots, namely, the third and the first
molar. The proportions (4.7% vs. 1.9%) of retained roots of all
teeth present indicate that third molars were extracted more
often than the first molars. However, in the mandible, but
not in the maxilla, third molar roots were more often located
wholly embedded in the bone than the first molar roots, which
suggests that third molar roots in the mandible may fracture
more easily.
Our study partly confirmed some earlier findings on the
prevalence of retained dental roots of all teeth. The occurrence
of 13% observed here for retained roots is lower than those of
an earlier Finnish (15%), British (17%), and US (20%) stud-
ies [2,11,3]. The slightly lower occurrence of retained roots in
our study may indicate that the level of oral and dental health
has increased since the time of the oldest studies. Other fac-
tors may be improvements in instrumentation, technique, and
education related to extractions.
Those who had only retained roots from third molars were
younger on average than those with other locations of retained
roots. This age difference may be explained by third molar
extractions (and thus root fracture), which are most often per-
formed in the age group of 20−40 years [12]. Another expla-
nation may be the upward movement of third molar roots left
behind, as demonstrated in coronectomy studies to occur over
time [13], and therefore, in older persons this tendency to
movement has brought some roots to the surface and subse-
quently the roots have been removed. The difference may be
also associated with the surge of extraction of third molars
beginning in the 1980s when all impacted teeth were indicated
for removal [14].
Our findings suggest that roots may fracture more easily
during tooth extraction in women than men. However, women
may also be more likely to visit a dentist and have their third
molars extracted. Earlier studies have not compared sexes for
the presence of retained roots located entirely in bone. In a
population study of clinically visible roots alone, a higher
occurrence of retained roots in men was reported [2]. How-
ever, the sex-difference was not apparent when using linear
regression analysis [15].
An important aspect of retained dental roots is whether
they need treatment [16]. Like most periradicular radiolucen-
cies, carious root remnants are focuses of infection and clear
indications for treatment. In our material, 6% of all partici-
pants had retained roots located partly in bone (Table 2), and
therefore, suggestive of need of treatment. In the British study
based on panoramic radiographs, 17% of the 1817 patients
had retained roots [11]. However, according to the individual
patient’s dentist, only 5–7% of the patients needed treatment
for the roots [11].
The coding for the diagnosis of a retained root in the ICD-
10 coding system [1] is confusing. It does not differentiate
between the two types of retained roots, namely, those within
bone after extraction and those exposed to the oral cavity and
with caries. Therefore, separate codes could be added to the
coding system for the two different types of retained roots.
This would also clarify research on the subject of retained
roots.
Our findings on the occurrence and characteristics of
retained roots entirely in bone are likely to be applicable
to all countries where oral and dental health is good, and
third molars are the most frequently extracted teeth. Further
research is needed on retained dental roots of third molars and
the rate of complications around third molar removal to iden-
tify measures to reduce their occurrence.
In conclusion, although retained dental roots were not
abundant in the population, the third molar region was the
most frequently observed. This suggests that extraction of the
third molar is challenging, especially in women. Our findings
which take account of all retained dental roots are novel and
further emphasize the distinctive character of the third molar
tooth.
ACKNOWLEDGMENTS
We acknowledge Planmeca Oy (Helsinki, Finland) for provid-
ing the digital panoramic x-ray apparatus and software. This
study formed part of the Health 2000 health examination sur-
vey organized by the Finnish Institute for Health and Wel-
fare which was supported in part by the Finnish Dental Soci-
ety Apollonia and the Finnish Dental Association. We thank
Mika Mattila DDS and Kari Soikkonen DDS, PhD for their
participation in interpretation of the radiographs. The authors
received no funding for the study. Field surveys in 2000 were
funded by the Finnish Institute for Health and Welfare (THL),
the Finnish Dental Society Apollonia, and the Finnish Dental
Association.
CONFLICTS OF INTEREST
The authors report no conflicts of interest.
AUTHOR CONTRIBUTION
Conceptualization: Sanna Koskela, Irja Ventä; Methodol-
ogy: Sanna Koskela, Miira Vehkalahti, Irja Ventä; Software:
Sanna Koskela, Miira Vehkalahti, Liisa Suominen, Irja
Ventä; Validation: Liisa Suominen, Irja Ventä; Form al
analysis: Sanna Koskela, Miira Vehkalahti, Liisa Suominen,
Irja Ventä; Investigation: Sanna Koskela, Liisa Suomi-
nen, Sisko Huumonen, Irja Ventä; Resources: Planmeca;
8of8 KOSKELA ET AL.
Data Curation: Miira Vehkalahti, Liisa Suominen, Sisko
Huumonen; Writing - original draft preparation: Sanna
Koskela, Irja Ventä; Writing - review and editing: Miira
Vehkalahti, Liisa Suominen, Sisko Huumonen, Irja Ventä;
Visualization: Irja Ventä; Supervision: Irja Ventä; Project
administration: Finnish Institute for Health and Welfare;
Funding acquisition: Finnish Dental Society Apollonia,
Finnish Dental Association.
ORCID
Sanna Koskela https://orcid.org/0000-0002-4284-3458
Miira M. Vehkalahti https://orcid.org/0000-0002-6319-
854X
Anna L. Suominen https://orcid.org/0000-0002- 8543-0055
Sisko Huumonen https://orcid.org/0000-0001-5891-7979
Irja Ventä https://orcid.org/0000-0003-2753-8444
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How to cite this article: Koskela S, Vehkalahti MM,
Suominen AL, Huumonen S, Ventä I. Retained dental
roots of adults: A nationwide population study with
panoramic radiographs. Eur J Oral Sci. 2022;e12862.
https://doi.org/10.1111/eos.12862
