DEPARTMENT OF ORAL & MAXILLOFACIAL SURGERY

RUNGTA DENTAL COLLEGE & RESEARCH CENTERKOHKA, BHILAI

PRESENTED BY –

DR. SHEETAL KAPSE

1st YEAR, P.G. STUDENT

MODERATORS -DR. SUNIL VYASDR. M. SATISHDR. MANISH PANDITDR. DEEPAK THAKUR

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.

JOURNAL CLUB

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

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

Inclusions -

1. Abstract2. Analysis for3. Aim4. Introduction5. Materials & methods6. Statistical analysis7. Results8. Discussion9. Conclusion10.Resources

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.

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

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.

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.

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.

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.

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.

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.

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).

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.

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).

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,

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.

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.

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.

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.

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.

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.

RESULTS

(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.

(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.

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.

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.

(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

(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.

(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

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.

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

DISCUSSION

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.

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.

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.

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.

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.

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

.

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.

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.

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 .

CONCLUSION

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.

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