inferior alveolar nerve in opg

1. PRESENTED BY –
DR. SHEETAL KAPSE
1st YEAR, P.G. STUDENT
MODERATORS -
DR. SUNIL VYAS
DR. M. SATISH
DR. MANISH PANDIT
DR. DEEPAK THAKUR

2. DARKENING OF THIRD MOLAR
ROOTS ON PANORAMIC
RADIOGRAPHS: IS IT REALLY
PREDOMINANTLY THICKENING OF
THE LINGUAL CORTICAL?
J. Szalma, L. Vajta, E. Lempel, S. Jeges, L. Olasz: Darkening of third
molar roots on panoramic radiographs: is it really predominantly
thickening of the lingual cortical?. Int. J. Oral Maxillofac. Surg. 2012;
xxx: xxx–xxx. # 2012 International Association of Oral and Maxillofacial
Surgeons. Published by Elsevier Ltd.

3. Authors
1. J. Szalma - Associate Professor, Head Of Division , Dentoalveolar
division
2. L. Olasz - Mentor: M.D., D.M.D, Ph.D. Professor,
Vice Chairman, Head Of Department , Maxillofacial division
3. L. Vajta – Resident, Dentoalveolar division
- Department of Oral and Maxillofacial Surgery,
University of Pecs, Hungary
4. E. Lempel - Assistant Professor, Department of Restorative Dentistry
and Periodontology, University of Pecs, Hungary
5. S. Jeges - Department of Biostatistics and Medical Informatics, Faculty
of Health Sciences, University of Pecs, Hungary

4. Key words:
Third molar
Panoramic radiography
Inferior alveolar nerve
Darkening of the root

5. Inclusions -
1. Abstract
2. Analysis for
3. Aim
4. Introduction
5. Materials & methods
6. Statistical analysis
7. Results
8. Discussion
9. Conclusion
10.Resources

6. Abstract
 This study investigated the exact intra-alveolar
etiology of a panoramic high-risk sign, darkening of
the third molar roots.
 83 mandibular third molar surgical removals
demonstrating dark bands on the third molar roots in
preoperative radiographs were included in this
prospective study.

7. ANALYSIS FOR -
 Association between
1. Exposure of the inferior alveolar nerve (IAN)
2. The root morphology of the third molar (e.g. groove or hook)
3. The integrity of the mandibular canal or lingual cortical wall
 Differences between
1. Single (increased radiolucency alone)
2. Multiple darkening cases (increased radiolucency with accompanying
‘high risk’ signs)
 Differences between exposure of inferior
alveolar nerve & groove on root

8. AIM
The authors’ aim was to examine the
Exact morphology of the third molar roots, the
integrity of the IAC and the visible thinning or
fenestration of the lingual cortical wall of the alveolus
when the preoperative panoramic radiograph showed
darkening of the root.

9.  Preoperative risk assessment of neurosensory
disturbances before third molar surgery is essential.
 Panoramic radiography is widely accepted and used
because of its advantages (cost effectiveness and low
radiation levels).
 The values of different ‘high risk’ markers
and specific signs have been evaluated and
discussed to some extent.
Introduction
Andrew C. Smith, Susan E. Barry, Inferior alveolar nerve damage following
removal of mandibular third molar teeth. A prospective study using
panoramic radiography. Australian Dental Journal 1997;42:3.

10.  Darkening of third molar roots on panoramic radiographs
was proved by several authors to be one of the strongest
classic specific signs indicating a close anatomic
relationship between the third molar roots and the
inferior alveolar canal (IAC).
Atieh MA. Diagnostic accuracy of panora-mic radiography in determining relationship between inferior
alveolar nerve and mandib-ular third molar. J Oral Maxillofac Surg 2010;68:74–82.
Blaeser B, August MA, Donoff RB, Kaban LB, Dodson TB. Radiographic risk factors for inferior alveolar
nerve injury during third molar extraction. J Oral Maxillofac Surg 2003;61:417–21.
Gomes A, Vasconcelos EB, Silva OE, Caldas FA, Neto I. Sensitivity and specificity of pantomography to
predict inferior alveolar nerve damage during extraction of impacted lower third molars. J Oral
Maxillofac Surg 2008;66:256–9.
Leung YY, Cheung LK. Correlation of radio-graphic signs, inferior dental nerve exposure, and deficit in
third molar surgery. J Oral Maxillofac Surg 2011;69:1873–9.

11.  In addition, Leung and Cheung stated that only darkening
of the root was significantly related to postoperative inferior
alveolar nerve (IAN) deficit.
Leung YY, Cheung LK. Correlation of radio-graphic signs, inferior dental nerve exposure,
and deficit in third molar surgery. J Oral Maxillofac Surg 2011;69:1873–9.
Bundy et al and O¨hman et al concluded that -
This radiolucent band - root material loss (groove on the
root) caused by the IAC.
Bundy MJ, Cavola CF, Dodson TB. Panora- mic radiographic findings as predictors of
mandibular nerve exposure following third molar extraction, digital versus conventional
radiographic techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:e36–
40.
O¨hman A, Kivija¨rvi K, Blomba¨ck U, Flygare L. Pre-operative radiographic eva- luation of
lower third molars with computed tomography. Dentomaxillofac Radiol 2006; 35:30–5.

12. whereas
 Tantanapornkul et al. stated,
According to their cone beam computed tomographic
(CBCT) findings, that -
Dark banding on panoramic radiographs is the sign
of lingual cortical thickening.
Tantanapornkul W, Okochi K, Bhakdinaronk A, Ohbayashi N,
Kurabayashi T. Correlation of darkening of impacted mandibular third
molar root on digital panoramic images with cone beam computed
tomography findings. Dentomaxillofac Radiol 2009;38:11–6.

13.  The exact formation of this sign seems to be multi-causal.
 The results of the author’s earlier investigations suggested
a significant difference between so-called single and
multiple appearances of dark bands on the third molar
roots in relation to IAN exposure.
Szalma J, Lempel E, Jeges S, Olasz L. Darkening of third molar roots: panoramic
radiographic associations with inferior alveolar nerve exposure. J Oral Maxillofac
Surg 2011;69:1544–9.

14. Case study & approval -
All the patients underwent surgery in the authors’ department
(Department of Oral and Maxillofacial Surgery, University of
Pe´cs, Pe´cs, Hungary) between January 2010 and September
2011.
Prior to operation, each patient provided full informed consent.
The study was approved by the Regional Research Ethics
Committee of the Medical Center, Pe´cs (Ref. No. 3795.316-
7851/KK4/2010).

15. Materials and methods
o This prospective study included 83 patients
39 males and 44 females
mean age of 28.1 + 6.7 years (range 16–48 years).
o Inclusion criteria –
Patients with darkening of the root on preoperative radiographs.
o Exclusion criteria –
Patients without darkening on preoperative radiographs were excluded
from the study.

16. Patients with darkening of the root on preoperative radiographs.
 Darkening was defined as a radiolucent band on the root of the third
molar, where the Inferior alveolar canal crosses it.
 Isolated/ single darkening was defined as
darkening of the root without adjacent panoramic signs.
 Multiple darkening was defined as darkening of the root and one or
more of the adjacent panoramic radiographic signs simultaneously
(diversion of the canal, narrowing of the canal, and interruption of the
superior cortical line).

17. Method -
Third molar removals were carried out under local anesthesia.
Flap designing
 Envelope (sulcular) mucoperiosteal flaps – superficial impactions
 Triangular flaps - deep impactions,
Vestibular and distal bone removal.
The sockets were irrigated with 20 ml of sterile saline solution at
room temperature,

18. The alveoli were checked during and after precisely focused,
careful suction for –
• IAN exposure,
• Root morphology,
• Groove formation and visible lingual cortical defects,
• Perforations or thickening lingual cortical bone.
 If excessive bleeding made intra-operative observation
ambiguous, the case was excluded from the study.

19. The exposed IAN
 The exposed IAN bundles were examined under loupe magnification using
a headlight.
 An IAN exposure was defined upon direct visualization of the suspected
neurovascular bundle.
 Criteria : Mesiodistally oriented tubular, pale or whitish structure at the
expected level of the socket (estimated according to the panoramic
radiographs).
 When the IAN was visible,
iodoform impregnated drains were placed at the suture insertion to prevent
possible nerve compression.

20. lingual cortical thickening
 Criteria : a regularly or irregularly shaped dark area on the
lingual surface of the alveolus, with or without an impression
caused by the third molar.
Soft tissues on the lingual surface lacking a tubular shape and
lacking mesiodistal orientation were determined to be
fenestration of the lingual cortical wall.

21. Root morphology
 The root morphology was observed from both
mesiodistal and buccolingual directions after
removal.
 If the reconstruction of fractured or segmented
roots was not possible, the case was excluded.

22.  Preoperative radiographs and the presence of the high risk
sign, darkening of the root (with or without adjacent ‘high
risk’ signs) were analyzed by J. Szalma & L. Vajta
 For preoperative panoramic image analysis, the Easydent
(Vatech, Korea) software was used.

23. Statistical analysis
 Data collection and statistical analysis were carried out with SPSS 18.0
(SPSS Inc., Chicago, USA) software.
 Associations of single and multiple darkening cases with the presence of
nerve exposure or with the presence of groove/hook formation were tested
by Pearson’s x2 test.
 A P value less than 0.05 was considered to be significant.
 Cohen’s kappa statistic was used to calculate observer agreement.
A kappa value -
<0.40 = poor agreement,
0.40–0.59 = fair agreement,
0.60–0.74 = good agreement,
0.75–1.00 = excellent agreement.

24. RESULTS

25. (a and b) 25-Year-old female patient with left lower
impacted third molar. Darkening of the root (single
darkening) developed because the mesiobuccal root
was curved and shorter than the mesiolingual root.

26. (a) 36-Year-old female patient with left mandibular
impacted third molar, with single darkening of the root.
(b) The buccal and lingual roots were superimposed.
(c) Mesiodistal view of the tooth shows that the shorter
buccal root explained the development of the darkening.

27.  Of the 83 extractions, the IAN was visible in 38 cases (38/83,
45.8%)
 Broken down
 30 times (30/83, 36.2%) in multiple darkening cases
 8 times (8/83, 9.6%) in single darkening patients.

28.  The localization of the visible IAN was:
10.8% buccal (4/ 38 cases),
40.6% inferior or inter-radicular (15/38 cases)
48.6% lingual (18/38 cases).
 Groove or hook formation was observed 25 times in multiple
darkening cases (25/47, 53.2%) and 6 times in single darkening cases
(6/36, 16.7%). All grooves were localized on the lingual surfaces of
the third molar roots or were positioned inter- or intra-radicularly.

29. (a–c) Different appearances of intra- and inter-radicular grooves with
the impression of the dental canal. In (c), the arrow indicates the
prepared cavity for improved retention for the Barry elevator

30. (d) The crop of the panoramic radiograph represents multiple
darkening (darkening with slight narrowing of the canal) of the
root. (e) The exposed IAN was seen lingually (arrow). (f) A
marked groove (almost a hook) was seen on the lingual surface
of the root.

31. (a and b) Despite the notable groove on the lingual surface of
the root (arrow), no darkening was seen at the expected height
of the root in the panoramic radiograph, supporting the
hypothesis that grooves might be present without radiological
consequences.
In 9.6% of the cases, special root conformation (imitating
darkening, was observed without any nerve exposure or cortical
deficiency

32. 27-Year-old female
patient with impacted
lower third molar with
single darkening. (b)
Note the exposed IAN
on the lingual surface
(arrow). (c) A groove
was observed on the
lingual surface of the
root tip (arrow). (d)
The lingual cortical
thickening is
remarkable (arrow).
The combination of a
missing canal wall, a
groove on the root and
a thicker lingual cortical
wall resulted in the
increased radiolucency.

33.  Both IAN exposure and groove formation
were significantly more frequent in multiple
darkening than in single darkening cases.
 Reversible paresthesia occurred in 1 patient
(1/83, 1.2%) observed at suture removal, and
the sensory disturbance resolved completely
within the first 3 weeks.
Follow up visits

34. DISCUSSION

35.  Proper screening of ‘high risk’ patients before impacted third
molar surgery is crucial.
 The determination of risky cases based on different panoramic
radiographic signs is widely accepted, but judgments on the
usefulness of these markers vary on a broad scale.
 Although these markers should indicate the close anatomical
relationship between the IAC/IAN and the third molar, the
explanation of their etiology is not uniform in the literature.

36.  In 1999, Rood and Shehab , in a literature review, collected seven
radiographic indicators of a close relationship between the mandibular
third molar and the inferior alveolar canal.
 Four signs were observed in the tooth root (darkening, deflection and
narrowing of the root, and a bifid root apex)
 Three in the canal (diversion, narrowing, and interruption in the white
line of the canal)
 Palma-Carrió C, García-Mira B, Larrazabal-Morón C, Peñarrocha-Diago MA. Radiographic
signs associated with inferior alveolar nerve damage following lower third molar extraction.
Med Oral Patol Oral Cir Bucal. 2010 Nov 1;15 (6):e886-90.
 Rood JP, Noraldeen Sheehab BA. The radi-ological prediction of inferior alveolar nerve
injury during third molar surgery. Br J Oral Maxillofac Surg 1990;28:20–5.

37. A – Darkening of root;
B – Deflection of root;
C – Narrowing of root;
D – Bifid root apex;
E – Diversion of canal;
F – Narrowing of canal;
G – Interruption in white
line of canal.

38. Darkening of root
 Rood and Shehab stated that darkening of the root is an
impingement of the root where the canal crosses it, whereas they
suggested that loss of the cortical lining of the canal is possible
as well.
 Bundy et al. described this sign as evidence for root material
loss of the third molars.
O¨hman et al. stated that groove formation of the root appears on
radio-graphs as a dark band, whereas this sign can be present without grooves.
 O¨hman et al. stated that groove formation of the root appears
on radio-graphs as a dark band, whereas this sign can be present
without grooves.
O¨hman A, Kivija¨rvi K, Blomba¨ck U, Flygare L. Pre-operative radiographic eva-
luation of lower third molars with computed tomography. Dentomaxillofac
Radiol 2006; 35:30–5.

39.  Monaco et al. found (in 73% of increased radiolucency cases)
direct contact between the third molar root and the mandibular
canal on axial CT scans.
Monaco G, Montevecchi M, Bonetti GA, Gatto MR, Checchi L. Reliability of panora- mic
radiography in evaluating the topographic relationship between the mandibular canal and
impacted third molars. J Am Dent Assoc 2004;135:312–8.
 O¨hman et al. found it in 100% according to coronal CT scans
O¨hman A, Kivija¨rvi K, Blomba¨ck U, Flygare L. Pre-operative radiographic eva- luation of lower
third molars with computed tomography. Dentomaxillofac Radiol 2006; 35:30–5.

40. Findings in favor of lingual cortical thickening
 Mahasantipiya et al first mentioned the possibility that darkening may
be present because of lingual cortical thickening,
Mahasantipiya PM, Savage NW, Monsour PA, Wilson RJ. Narrowing of the inferior dental
canal in relation to the lower third molars. Dentomaxillofac Radiol 2005;34: 154–63.
 while Tantanapornkul et al. later clearly concluded that the majority
(80%) of darkening cases showed lingual cortical thickening in CBCT
images, in contrast with 20% caused by grooves.
Tantanapornkul W, Okochi K, Bhakdinaronk A, Ohbayashi N, Kurabayashi T. Correlation of
darkening of impacted mandibular third molar root on digital panoramic images with cone
beam computed tomography findings. Dentomaxillofac Radiol 2009;38:11–6
.

41.  Additionally, special root conformation, which
imitated darkening of the root on radiographs, had a
notable 9.6% rate of occurrence.
Neither Mahasantipiya et al. nor Tantanapornkul et al.
had described this as an possible alternative.
 Grooving without darkening has been experienced in
the authors’ practice , but it did not occur during the
study period.

42.  Susarla et al estimated the correlation between interrupted cortical walls of
IAC and IAN exposures using panoramic radiography, CT scans and
intraoperative observations.
Susarla SM, Sidhu HK, Avery LL, Dodson TB. Does computed tomographic assessment of inferior alveolar
canal cortical integrity predict nerve exposure during third molar surgery? J Oral Maxillofac Surg 2010;68:
1296–303.
 They showed that the IAN exposure group had significantly bigger defects
of the IAC wall.
 They observed 31 IAN exposures showing significant ( 3 mm) cortical
defects of the IAC from the 80 evaluated ‘high risk’ third molar extraction
cases in their study.
 The frequency of IAN exposures (38.8%) representing IAC cortical wall
deficiency in their study correlates with the present results, but Susarla et al.
did not publish any information on the concurrent panoramic signs in that
study.

43.  In 38 cases (45.8%), the IAN was visible during the operation with
adjacent grooving of the root in 31 (81.6%) of these cases.
 22 (26.5%) of the cases showed lingual cortical thickening.
 Specious root conformation explained the formation of darkening on the
radiographic images of an additional 8 (9.6%) of the cases.
 According to these findings, darkening of the third molar roots is
more often the result of fenestration of the inferior alveolar canal
wall or groove formation of the root than lingual cortical thickening .

44. RESOURCES
1. J. Szalma, L. Vajta, E. Lempel, S. Jeges, L. Olasz: Darkening of third molar
roots on panoramic radiographs: is it really predominantly thickening of the
lingual cortical?. Int. J. Oral Maxillofac. Surg. 2012; xxx: xxx–xxx. # 2012
International Association of Oral and Maxillofacial Surgeons. Published by
Elsevier Ltd.
2. Andrew C. Smith, Susan E. Barry, Inferior alveolar nerve damage following
removal of mandibular third molar teeth. A prospective study using panoramic
radiography. Australian Dental Journal 1997;42:3.
3. Rood JP, Noraldeen Sheehab BA. The radi-ological prediction of inferior
alveolar nerve injury during third molar surgery. Br J Oral Maxillofac Surg
1990;28:20–5.
4. Palma-Carrió C, García-Mira B, Larrazabal-Morón C, Peñarrocha-Diago MA.
Radiographic signs associated with inferior alveolar nerve damage following
lower third molar extraction. Med Oral Patol Oral Cir Bucal. 2010 Nov 1;15
(6):e886-90.

45. THANK
YOU