Evaluation of impacted mandibular third molar using panaromic radiographs

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Evaluation of Impacted Mandibular Third Molar
using Panaromic Radiographs
Hemamalini Balaji , Dr.K.Laliytha
Saveetha Dental College and Hospitals, Chennai
INTRODUCTION:
Removal of mandibular impacted third molars are routine
surgical procedure performed by maxillofacial surgeons in
dental clinics as well as hospital setups. [1].To prevent
complications a useful diagnostic tool is needed that can
determine the relationship between inferior alveolar nerve
and the impacted third molar.[2] The reported frequency of
inferior alveolar nerve injury associated with M3 removal
ranges from 0.6% to 5.3% but the risk of permanent IAN
injury is less than 1% [3–7].Panoramic radiography is
suggested as the technique of choice to evaluate impacted
third molars as well as to estimate the pre-operative risk for
inferior alveolar nerve injury associated with third molar
surgery [8]. Smith AC et al., [9] also described panoramic
radiography as optimal method for radiological assessment
for mandibular third molar teeth prior to their removal.
Imaging techniques for impacted mandibular third molars
(IM3M s) are as follows: intraoral periapical radiography
(IOPA); extraoral techniques like lateral oblique and
panoramic methods, skull radiography, computed
tomography (CT), among which orthopantomograph
(OPG), an adjunct to IOPA, remains the method of choice.
Orthopantomography (means straight broad coverage slice
technique) was first proposed by Numata in 1933.[10]
Third molar is the most frequently impacted tooth.[11] The
prevalence of third molar impaction ranges from 16.7% to
68.6%[.11-21] Most studies have reported no sexual
predilection in third molar impaction[11,12,15,17,19] Some
studies, however, have reported a higher frequency in white
European females [21,22] and Singapore Chinese females
than males.[19].Several methods have been used to classify
impaction, in which impaction is described based on the
level of impaction,[23] the angulations of the third
molars,[24] and the relationship to the anterior border of
the ramus of the mandible.[23]
Depth or level of mandibular third molars can be classified
using the Pell and Gregory classification system,[22] where
the impacted teeth are assessed according to their
relationship to the occlusal surface of the adjacent second
molar. Thus the aim of this study is to Evaluate the
Preoperative radiographic and clinical parameters of IM3M
to assess Clinical Symptoms, Number of Roots,pattern of
Impaction,Level of Impaction,Angilation,relationship of
Inferior Alveolar Canal with their roots,and also assessment
of any effect on the adjacent tooth structure like Dental
Carries or Root resorption
Radiographic technique
The subject was positioned properly in the panoramic
machine set up by adopting the principles of Goaz and
White.[3] Appropriate kVp and mA parameters were
selected and exposures were made. All the films were
processed manually in a well-equipped lightproof dark
room as described by Goaz and White.[11]
Matetrials and methods-
Of One Hundred And Fifty OPGs ,Eighty Five
orthopantomograms (OPG) of patients aged 19 years and
older (45males and 40 females) were selected. The
remaining 48% were excluded from the study due to lack of
fulfilling the Inclusion criteria.
Orthopantomograph of 65 patients visiting department of
oral medicine and radiology of our college were selected
for the purpose of this study.The radiographs were taken
using Digital panaromic machine.
Inclusion Criteria:
The criteria for selection of radiographs are
1-Either unilateral or bilateral mandibular 3rd molar
impaction
2-Clinically symptomatic or asymptomatic patients
Exclusion criteria-
Any patient with history of extraction of permanent teeth
,age less than 19 years, mandibular fracture or orthodontic
treatment was excluded from the study, also patients with
developmental anomalies , congenital or sysetemic diseases
and major pathologies like Cleidocranial dysplasia in
mandible were excluded, also 3rd molars having
underdeveloped roots were excluded.
Method Of Examination:
The patients were clinically examined under aseptic
condition and informed consent were obtained. The
radiographs were taken according to the panoramic
machine specifications which has a constant magnification
of 1.2.
The study sample was divided into symptomatic an
asymptomatic case.On clinical and radiographic
examination ten relevant questions were formulated . Each
radiograph was viewed digitally and measurements were
made using a digital software called DICOM viewer and
Analyser.
Third molar was considered impacted if it was not in
functional occlusion and at the same time, its roots were
fully formed.Outline of mandibular 1st premolar 2nd
premolar, 1st molar, 2nd molar and 3rd molar of the right and
left sides were traced. Following Ganss method, occlusal
plane was drawn through the tip of the most superior cusps
of the 1st premolar and the tip of the most superior mesial
cusps of the second molar extending upto anterior border of
ramus of the mandible . A perpendicular line is drawn from
the occlusal plane touching the most distant point of the
second molar. The available third molar space was
Hemamalini Balaji et al /J. Pharm. Sci. & Res. Vol. 7(11), 2015, 940-945
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determined as the distance between the intersection of the
vertical line with the occlusal plane , also the mesio-distal
width of the 3rd molar crown was recorded. Based on the
above method the impactions are classified as
 Class 1- the available space is more or equal to the
mesio-distal diameter of 3rd molar.
 Class2- the availabie space is less then the mesio-
distal diameter of the 3rd molar.
 Class 3- if the tooth was located completely within
the mandibular ramus( the retromolar space is
obliterated because the ascending ramus of the
mandible was located immediately posterior to the
second molar.
Radiographic analysis also reveals,the levels of eruption
 Level A: When there is crown to crown position
between impacted third molar and second molar .
 Level B:When there is crown to cervical position
between the impacted third molar and second
molar.
 Level C: When there is crown to root position
between the impacted third molar and second
molar.
Outline of the inferior alveolar canal was traced to record
its relation to the third molar root apices.
 Adjacent: When the superior border of the canal
was touching the root apices or within 2mm below
them.
 Super imposed : When the canal was
superimposed over part of the roots which
appeared less radioopaque than the remaining
radiological image.
 Notching: When there was a radiolucent band at
the apex of the roots, a break in the continuity of
the upper radio dense border, and narrowing at the
expense of the top of the canal was present.
 Grooving : When radiolucent band across the root
above apex was present with interruption of both
superior and inferior border of the canal, and
narrowing of the canal space.
 Perforation: With radiolucent band crossing the
root above the apex and loss of both superior and
inferior border of the canal at the area where they
cross the root , with constriction of the canal
maximal in the middle of the root was present.
 None: When there was no relation between the
canal and the root apices, condition was recorded.
Number of roots of the IM3M was also recorded from the
radiograph. And the Inclination of the third molars were
categorized as Mesio Angular,Distoangular,Horizontal and
Vertical.In addition any effect on the adjacent tooth
structure like Dental caries or External root resorption was
also evaluated. OPGs were reviewed by a single examiner
in a dark room using an appropriate X-ray viewer to
determine the prevalence of impacted third molars in the
sample, their levels of eruption; and their angulations.
Third molar status was determined based on the patient’s
chart and the OPG.
Data was analyzed using a Pearson chi-square (χ2) test,
performed using the Statistical Package for the Social
Sciences (version 15.0; SPSS, Inc, Chicago, IL). All
assessment was done by a single examiner to eliminate
inter-examiner errors. Chi-Square test is applied to compare
proportions. If any expected cell frequency is less than five
then Fisher’s Exact Chi-Square test is used. If P-Value <
0.05 then it was considered as Statistically Significant
RESULT:
Distribution based on Age and Sex:
All the IM3M OPG samples used in this study was Among
85 samples,45 (52.9%) were male and40 (47.1%) were
female; with the sex ratio of 1:1.3. The age range was from
19 to 55 years (mean age ± SD= 28.91±9.26). Among the
85 subjects,52.9% were males and 47.1% were
Females.(Table 1)
Table 1 also contains data regarding the no.of roots in the
Impacted Mandibular Third Molars considered for
research,which revealed presence of single root in 11
(12.9%) of the observed cases and two roots were observed
in 74 (87.1%) of cases.Out of the 85 IM3M 53 were
Partially erupted and 32 were Completely impacted.
On clinical Evaluation of a patient ,He/she can be
categoriesed as Symptomatic (54)and Asymptomatic(31),
depending on the Chief Complaint and clinical response of
the Patient .Chart 1 shows the prevalence of various causes
of Symptomatic Cases individually like
Pericoronitis(72.2%),Pericoronal Abscess(0%),Restricted
Mouth opening(1.9%) and Fetor Oris (0%)These clinical
symptoms are also present in Combinations.
Then based on Radiological evaluation , In this study out of
85 impacted third molars, greater frequency of impacted
third molars were found to be in a mesioangular 42
(49.4%), followed by 21 (24.7%) in vertical , 21(24.7%)
horizontal,1 (1.2%) distoangular.There was no significant
difference between the angulations of different
groups(considering P<0.658)( Table 2)
Table 1:
Gender Count % Number of Roots Right Left Total
Male 45 52.9 N % N % N %
Female 40 47.1 1 6 14.0 5 11.9 11 12.9
Total 85 100.0 2 37 86.0 37 88.1 74 87.1
Total 43 100.0 42 100.0 85 100.0
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Chart 1:
Table2:
Angulation of Impacted teeth Level of Impaction
Clinical Symptoms Asymptomatic Symptomatic Total Clinical
Visibility Partially erupted Completely
Impacted Total
N % N % N % N % N % N %
Mesioangular 13 41.9 29 53.7 42 49.4 Level-A 19 35.8 3 9.4 22 25.9
Disto angular 0 0.0 1 1.9 1 1.2 Level-B 25 47.2 12 37.5 37 43.5
Horizontal 9 29.0 12 22.2 21 24.7 Level-C 9 17.0 17 53.1 26 30.6
Vertical 9 29.0 12 22.2 21 24.7 Total 53 100.0 32 100.0 85 100.0
Total 31 100.0 54 100.0 85 100.0
Chi square Test –Fisher’s Exact Test
Value-1.908,P-Value-0.658
Chi square Test –Fisher’s Exact Test
Value-17.244,P-Value<0.001
Table 3:Distribution Based on Radiographic third molar Space Availability:
Available space
Clinical visibility if tooth Chief Complaint
Partially erupted Completely erupted Total Asymptomatic Symptomatic Total
N % N % N % N % N % N %
Class-I 23 43.4 11 34.4 34 40.0 16 51.6 18 33.3 34 40.0
Class-II 29 54.7 20 62.5 49 57.6 15 48.4 34 63.0 49 57.6
Class-III 1 1.9 1 3.1 2 2.4 0 0.0 2 3.7 2 2.4
Total 53 100.0 32 100.0 85 100.0 31 100.0 54 100.0 85 100.0
Chi Square test -Value =14.353.P-Value <0.001
Assessing the level of impaction using PELL and
GREGORY classification showed that 22 (25.9%)
impacted tooth was in position A, 37(43.5%) was in
position B, and 26 (30.6%) was in position C.There was
highly significant difference between the level of Impaction
of Third molar in different groups considering
P<0.001.(Table 2-Right side)
On Examination of the collected OPG’s ,34(40.0%)
impacted mandibular Third molar were in class1 reralition
of which 33.3 % were symptomatic and 51.6% were
0
10
20
30
40
50
60
70
80
90
100
SymptomaticcasesClinicalFindings
SymptomaticcasesClinicalFindings
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Table 4
Table5:
Effect on
adjacent tooth
Chief Complaint Clinical visibility if tooth Impacted Tooth
Asymptomatic Symptomatic Total Partially
erupted Completely
erupted Total Right Left
N % N % N % N N % N % % N % N %
NP 22 71.0 27 50.0 49 57.6 29 24 55.8 25 59.5 54.7 20 62.5 49 57.6
P-DC 5 16.1 7 13.0 12 14.1 11 6 14.0 6 14.3 20.8 1 3.1 12 14.1
P-EXT 4 12.9 15 27.8 19 22.4 9 10 23.3 9 21.4 17.0 10 31.3 19 22.4
P-DC, EXT 0 0.0 5 9.3 5 5.9 4 3 7.0 2 4.8 7.5 1 3.1 5 5.9
Total 31 100.0 54 100.0 85 100.0 53 43 100.0 42 100.0 100.0 32 100.0 85 100.0
Chi-Square Test Fisher's Exact Test
Value-6.145
P-Value -0.085
Chi square Test Fisher’s Exact Test
Value-14.353
P-Value-0.001
Chi Square Test-Fisher’s Test
Value-0.396
P-Value-0.998
Asymptomatic,49 (57.6%) belonged to class2 relation of
which 63.0% were symptomatic and 48.4% were
Asymptomatic,while class 3 was found in 2 (2.4%) of the
cases among which 3.7% were symptomatic. There was
significant difference in the third molar space availability
among different group was found when partially erupted
and completed impacted tooth were compared considering
P<0.001
On tracing the Inferior alveolar canal ,and identifying the
relation between the canal and the root apices ,a total of
40(47.6%) was found to be in adjacent relation,27(32.1%)
were superimposed. In 8(9.5%) the relation was notching
,in 2(2.4%) it was Grooving,and in 7(8.3%).There was no
significant difference between the third molar roots and
IAN relation in different groups (considering P<0.06)
comparing asymptomatic with symptomatic group
,Partially erupted with Completely Impacted Category and
right and left sided tooth.(Table4)
Radiological evaluation of the adjacent tooth to that of the
impacted third molar ,reaveals any presence or absence of
destructive effect on the adjacent tooth.Table 5 shows
distribution of effect on adjacent tooth structure due to the
impacted third molar which represents No destructive
effects on adjacent tooth in 49(57.6%) of the
samples,Presence of Decay in 12(14.1%) of case ,presence
of external root ressorption in 19(22.4%) of cases,while
both decay and External root resorption observed in
5(5.4%) of cases.There was no significant differences in the
effect on adjacent tooth struction in symptomatic and
asymptomatic group(P<0.085),and no significant difference
comparing Right and left sided (P<0.998).But there was
high significance when comparing the Partially erupted and
Completely Impacted Groups(P<0.001).
DISCUSSION:
Orthopantomographs were taken for 65 subjects visiting
Saveetha Dental College and Hospitals who consented to
participate in our study. Only those subjects who
conformed to the inclusion and exclusion criteria outlined
previously were selected for the study. The normal time of
eruption of third molars are variable, starting at the age of
16 years.[25] The patients included in our study were
consecutive individuals in the age group of 20–35 years
(mean 28.91). This was consistent with other studies where
the subjects were in the same age group [26-29].The
subjects were clinically examined and their OPG's were
taken. Evaluation was done as per guidelines mentioned in
the materials and methods. The parameters sought were
prevalence of impacted third molars with or without
clinical symptoms and clinical visibility, no.of roots
,angulations, level of eruptions, mesiodistal width of
impacted third molar and retromolar space
Relation of
IM3M
Chief Complaint Clinical visibility of tooth Impacted tooth
Asymptomatic Symptomatic Total Partially
erupted Completely
erupted Right Left Total
N % N % N % N % N % N % N % N %
Adjacent 12 38.7 28 52.8 40 47.6 33 62.3 7 22.6 17 40.5 23 54.8 40 47.6
Super
imposed 14 45.2 13 24.5 27 32.1 12 22.6 15 48.4 16 38.1 11 26.2 27 32.1
Notching 1 3.2 7 13.2 8 9.5 2 3.8 6 19.4 3 7.1 5 11.9 8 9.5
Grooving 2 6.5 0 0.0 2 2.4 1 1.9 1 3.2 2 4.8 0 0.0 2 2.4
Perforation 2 6.5 5 9.4 7 8.3 5 9.4 2 6.5 4 9.5 3 7.1 7 8.3
None 0 .0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0
Total 31 100.0 53 100.0 84 100.0 53 100.0 31 100.0 42 100.0 42 100.0 84 100.0
Chi square Test-Fisher’s Exact Test=Pvalue-0.061
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available,relation to the Inferior Alveolar canal,and effect
on the adjacent tooth structure. The OPG’ were also used
for evaluating the agenesis of third molars.
In our study, the frequency of impacted third molars
showed a predilection for males over females which was
not consistent with a previous study [25,26,30]w Haidar
and Shalhoub[40]evaluated 1000 orthopantomograms
(OPGs) and reported an incidence of 32.3% for third molar
impaction with no sex predilection.
The mesiodistal space available for third molars is as same
as or larger than mesiodistal width of the crown then, the
crown has more chances to erupt.[31] In the present study
the mean mesiodistal crown width of right and left side of
the mandible is 13.17 mm (1.07) and 13.16 mm (1.18). the
corresponding average retromolar space of right and left
mandible is 11.8 mm (SD = 2.96) and 12.16 (SD = 2.86)
respectively.
The most significant radiological sign noticed in our study
was the diversion of the mandibular canal & the least
associated sign was found to be grooving. Our study was
in consistent with the study conducted by Rood &
Carrio.[32,33]
The current study is in agreement with those of Quek et
al,[34] Kramer and Williams,[35] and Moris and
Jerman[36] regarding the most common angulation in the
mandible, which was the mesioangular (41.9%). However,
the findings are in contrast to those of Hugoson and
Kugelberg,[37] who found the vertical angulation to be the
most common. This could be due to the fact that a different
method of classification of angulation was used in this
study.
Evaluating incidence, position, depth and measurements of
impacted teeth in a population helps us to compare the
patterns of impacted teeth in other regions and sub-
populations of the world.
Most third molars were noticed in level B(43.5%), followed
by level C(30.6%)and level A( 25.9%). In all impactions
the mesiodistal width of the tooth was more than the
retromolar space, there by accounting for the impactions.
As the presence of Partially impacted Mandibular molars
are higher than the completely impacted molars,it was
found that_mandibular third molars are in Class 2
relation,followed by –in class 1 relation and – in class 3
relation.Results of present study are in accordance with that
of Susarla and Dodson[38].Results were not in agreement
with that of Jerjes et al [39]as they suggested maximum
number of IM3M in class 1 relation..the measurement of
mesiodistal space ,measured from the panaromic
radiograph served to be an important variable in prediction
of the eruption.Abortive eruption occurs due to lack of
space also. In the present study, 12.9% one, 87.1% two and
0% had three roots ,this was similar to that reported by
Tammisalo.[41] However, the findings of the present study
are very much dissimilar with 22% one 67% two and 11%
more than two roots reported byWenzel.[42] The disparity
among the number of roots for third molars could be
attributed to the racial variation, sample size, and
methodology.The presence of destructive effect on adjacent
tooth structure was noted in 42.4% of the cases of which
dental caries was prevalent in 14.0% of right and 14.3% of
left side,external root resorption in 23.3% of right and
21.4% of left side impacted tooth,presence of both in 7.0%
in right and 4.8%in left side.
On comparing this study with other regional studies it was
evident that there was no universal consensus on incidence
or patterns of impactions. These differences may be
attributed to inadequate International standardization of
evaluation criteria and to the difference in evaluation tools.
There is plenty of scope to do standardized global
multicentric studies with uniform guidelines and larger
number of subjects. This may help us to understand
similarities and differences in the patterns of impaction on
global level.
CONCLUSION:
Thereby, future studies are required to evaluate the etiology
behind this relatively high frequency of third molar
impaction especially in the India. The present study, like
most of the similar previous works about third molar
impaction, used a hospital based sample, which lacks
randomization. More precise studies are necessary to
evaluate the impaction of third molars in a randomized
sample representative of Indian population as they are
required to evaluate the pattern of third molars impaction in
India. Thus this study has hopefully fulfilled the purpose
of creating evidence based report of preoperative
evaluation of Impacted mandibular third molar thus
minimizing the complications during surgical extraction.
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