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Localization of the mandibular neurovascular bundle using dental magnetic resonance imaging

Authors:
Christian Nasel at University Hospital Tulln
Christian Nasel
  • University Hospital Tulln
A Gahleitner
A Gahleitner
A Gahleitner
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Martin Breitenseher at Landesklinikum Horn
Martin Breitenseher
Christian Czerny at Medical University of Vienna
Christian Czerny
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Abstract and Figures

To assess the reliability of a commercially available 3D-MPR MRI program for the jaws for imaging the mandibular neurovascular bundle. A gradient echo sequence (TR: 49 ms/TE: 6.3 ms/flip angle: 25 degrees/excitations: 3) with a spectral fat suppression pre-impulse and a voxel size of 0.9 x 0.9 x 0.8 mm was designed. Cross-sectional and panoramic reconstruction of the whole mandible were performed from the axial scans using Easy Vision (Philips, Best, The Netherlands) software package. The ability of differentiate the mandibular neurovascular bundle was assessed in 11 patients. The mandibular neurovascular bundle was clearly visualized in all cases. Dental MRI is a possible alternative to plain films or CT for patients requiring surgery near the mandibular canal.
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SHORT COMMUNICATION
Localization of the mandibular neurovascular bundle using dental
magnetic resonance imaging
C Nas
Ï
el
1
, A Gahleitner
1
, M Breitenseher
1
, C Czerny
1
, C Glaser
2
, P Solar
3
and H Imhof
1
1
Department of Radiology, University of Vienna;
2
Department of Oral and Maxillofacial Surgery, University of Vienna;
3
Department
of Oral Surgery, University of Vienna, Wa
È
hringergu
È
rtel, Austria
Objective: To assess the reliabilty of a commercially available 3D-MPR MRI program for the
jaws for imaging the mandibular neurovascular bundle.
Methods: A gradient echo sequence (TR: 49 ms/TE: 6.3 ms/¯ip angle: 258/excitations: 3)
with a spectral fat suppression pre-impulse and a voxel size of 0.960.960.8 mm was
designed. Cross-sectional and panoramic reconstruction of the whole mandible were
performed from the axial scans using Easy Vision (Philips, Best, The Netherlands) software
package. The ability to dierentiate the mandibular neu rovascular bundle was assessed in 11
patients.
Results: The mandibular neurovascular bundle was clearly visualized in all cases.
Conclusion: Dental MRI is a possible alternative to plain ®lms or CT for patients requiring
surgery near the mandibular canal.
Keywords: magnetic resonance imaging; mandibular nerve; mandible; image processing,
computer-assisted
Introduction
Location of the mandibular canal is crucial for certain
surgical pro cedures to avoid injury to the neurovas-
cular bundle. Plain ®lm radiography and CT are
currently used to demonstrate the bony margins of the
mandibular canal,
1,2,3
but in some cases they cannot be
suciently dierentiated. MRI has been shown to
demonstrate the contents of the mandibular canal
directly.
4,5
A high resolution gradient echo sequence,
designed for dental imaging and showing good
contrast between the mandibular neurovascular
bundle and the surrounding tissues was designed by
the authors. The axial slices from this sequence are
accessible on a workstation with commercially
available dental imaging software which gives images
comparable to those obtained with other 3D-MPR
programs available for den tal CT. The aim of this
paper is to report the validity of this MR procedure
for the assessment of the mandibular neurovascular
bundle.
Materials and methods
A 1T MR-scanner (Gyroscan 10 T NT, Philips, Best,
The Netherlands) was used with a standard neck-quad
coil. The whole mandible was examined in a single
gradient echo sequence with 49 ms/6.3 ms/258/3 (TR/
TE/¯ip angle/excitations) with a spectral fat suppres-
sion pre-impulse. The slice thickness was 1.6 mm with
50% overlap resulting in a calculated thickness of
0.8 mm. A ®eld of view of 120 mm and a scan matrix
of 1286128 voxels was used. The scan time for 51
slices was 5 min 40 s. Scanning was performed in the
axial plane. Panoramic and cross-sectional multiplanar
reconstructions were performed subsequently on a
workstation (Easy Vision, CT/MR Version 2.1,
Philips, Best, The Netherlands) which was equipped
with the dental software package provided by the
manufacturer (Philips, Best, The Netherlands). This
procedure will be called dental MRI in this report. The
study was based on 11 patients aged between 32 and 57
years who complained of dysaesthesia in the ¯oor of
the mouth at the time of their follow up MR
examination, 6 ± 12 months after resection of a
pharyngeal tumour.
All images were read by two radiologists indepen-
dently for the ability to dierentiate the mandibular
neurovascular bundle and scored on a 2-point scale:
Grade 0: not dierentiable and grade 1: accurately
Correspondence to: C Nas
Ï
el, MD, Department of Radiology, University of
Vienna, Wa
È
hringergu
È
rtel 18 ± 20, A-1090 Vienna, Austria
Received 23 February 1998; accepted 19 June 1998
Dentomaxillofacial Radiology (1998) 27, 305 ± 307
1998 Stockton Press All rights reserved 0250 ± 832X/98 $12.00
http://www.stockton-press.co.uk/dmfr
dierentiable. If there was any doubt it was scored
grade 0.
Results and Discussion
The contents of the mandibular canal were clearly
depicted in all subjects. The neurovascular bundle
showed a moderately hyperintense signal which gives
an excellen t contrast to the low signal from
surrounding bone (Figure 1). Therefore, the neuro-
vascular structures can also be recognized easily on
the panoramic reconstructions (Figure 2). Landmarks
such as the mental foramen and the relationship of
the neurovascular bundle to the inferior cortex were
reliably demon strated on the cross-sectional recon-
structions in all cases (Figure 3a and b). In those
cases where the cortex of the mandibular canal was
present it could also be readily dierentiated.
Susceptibility artefacts from the bone/tissue interface
did not cause signi®cant interference. Spatial distor-
tion could be kept to a minimum with the scan
parameters and the voxel size used. Furtherm ore,
using this technique the scan time can be kept shorter
than 6 min. Additionally, movement of the jaw can
be avoided by using a bite block during the
examination.
Neural and vascular structures within the mandibu-
lar canal could not be identi®ed separat ely. Occasion-
ally, branches of the inferior dental plexus arising from
the neurovascular bundle were identi®ed. This is not a
disadvantage, as far as treatment is concerned,
although the ability to assess the vascularization of
the mandible after trauma would be of clinical interest.
Since the proposed sequence is compatible with
intravenous MR contrast agents, contrast-enhanced
dental MRI could be helpful.
Metallic restorations in the teeth did not interfere,
since imaging was performed in the axial plane and the
anatomical structures of interest lie below the occlusal
plane. Possible interference from fatty bone marrow
Figure 1 Axial MR-scan of the mandible about 3 mm above the
inferior cortex using a high resolution gradient echo sequence with
49 ms/6.3 ms/258/3 (TR/TE/¯ip angle/excitations) and a spectral fat
suppression pre-impulse. The neurovascular bundle is clearly shown
as a hyperintense structure (black arrows). The complete set of axial
scans constitutes the raw data for the panoramic and cross-sectional
reconstructions
Figure 2 Panoramic reconstruction showing the course of the
neurovascular bundle on both sides of the mandible as a band of
bright signal (black arrows). Additionally, the relationship of the
neurovascular bundle to the root of the lower right ®rst premolar
(open arrow) can be seen. The dental pulp shows a bright signal,
while the surrounding dentin presents as a signal void
a
b
Figure 3 (a) Cross-sectional reconstruction showing the contents of
the mandibular canal (arrow) are seen in relation to the buccal and
lingual cortices. (b) Cross-sectional reconstruction showing the exit of
neurovascular bundle at the mental foramen (small black arrow)
Mandibular nerve
CNasÏel et al
306
was suppressed by the spectral fat suppression pre-
impulse, which increased the contrast between the bone
and neurovascular structures.
In conclusion, due to the reliable demonstration of
the whole neurovascular bundle on both sides of the
mandible, independence of adjacent bony structures,
short examination time and sucient spatial resolution
for planning oral surgery, dental MRI could become a
viable alternative to plain ®lms or similar 3D-MPR CT
programs.
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... In this context, magnetic resonance imaging (MRI) has been recently proposed as a radiation-free 3D imaging method for MTM [8]. MRI benefits by directly depicting the neurovascular bundle (NVB) [9] and is therefore independent of the integrity of the MC wall [10,11]. An ex vivo study has proven by superimposition of MRI and CT scans that the geometric accuracy of MRI to display the IAN is comparable to the CT technique [12]. ...
... To date, there is no standard term regarding what is actually visualized by MRI. Nasel et al. [9] have previously stated that the neural and vascular structures within the MC could not be distinguished and thus referred to the term "NVB." Since then, "NVB" [36][37][38][39], "IAN" [8,17,40,41], "mandibular nerve" [10,12], or "MC" [11, 14,23,29] were used synonymously in various publications. ...
... However, one should keep in mind that the "misjudgment" might actually not necessarily occur when judging the MRI images. In fact, MRI is the most commonly used technique to directly visualize the IAN [22] and to precisely localize the IAN including pathologic processes [9,[44][45][46]. ...
Is MRI a viable alternative to CT/CBCT to identify the course of the inferior alveolar nerve in relation to the roots of the third molars?
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Full-text available
  • Jun 2021
  • CLIN ORAL INVEST
Objectives To assess the reliability of judging the spatial relation between the inferior alveolar nerve (IAN) and mandibular third molar (MTM) based on MRI or CT/CBCT images. Methods Altogether, CT/CBCT and MRI images of 87 MTMs were examined twice by 3 examiners with different degrees of experience. The course of the IAN in relation to the MTM, the presence/absence of a direct contact between IAN and MTM, and the presence of accessory IAN were determined. Results The IAN was in > 40% of the cases judged as inferior, while an interradicular position was diagnosed in < 5% of the cases. The overall agreement was good (κ = 0.72) and any disagreement between the imaging modalities was primarily among the adjacent regions, i.e., buccal/lingual/interradicular vs. inferior. CT/CBCT judgements presented a very good agreement for the inter- and intrarater comparison (κ > 0.80), while MRI judgements showed a slightly lower, but good agreement (κ = 0.74). A direct contact between IAN and MTM was diagnosed in about 65%, but in almost 20% a disagreement between the judgements based on MRI and CT/CBCT was present resulting in a moderate overall agreement (κ = 0.60). The agreement between the judgements based on MRI and CT/CBCT appeared independent of the examiner’s experience and accessory IAN were described in 10 cases in MRI compared to 3 cases in CT/CBCT images. Conclusions A good inter- and intrarater agreement has been observed for the assessment of the spatial relation between the IAN and MTM based on MRI images. Further, MRI images might provide advantages in the detection of accessory IAN compared to CT/CBCT. Clinical relevance MRI appears as viable alternative to CT/CBCT for preoperative assessment of the IAN in relation to the MTM.
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... The increased ability to differentiate soft tissue from the bone structure with MRI may be advantageous for the evaluation of the anatomical variations of the MC/IAN compared to CBCT. [13][14][15][16][17][18] MRI for neurovascular imaging is a non-invasive, harmless imaging method that lacks radiation exposure and provides the advantage of tracking the nerve itself instead of the canal cortex. As there are various studies and classifications of MC/IAN in the literature, there is still no consensus on the classification of bifid MCs (BMCs). ...
... There are various imaging methods to examine anatomical variations of the MC/IAN, and there is a high level of data on branching patterns, topographical features, and location. [15][16][17][18] Conventional radiography is not an ideal method to evaluate the MC/IAN because of the lack of three-dimensional information and may lead to confusion of the mylohyoid groove and MC/IAN because of superimposition. [11,12] According to a study by de Oliveira-Santos et al., [19] only 59% of the MCs were found to be corticated when 200 hemimandibles were observed using CBCT. ...
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A BSTRACT Background The inferior alveolar nerve (IAN) is located in the mandibular canal (MC). It is critical to evaluate the position of the MC during treatment planning to prevent intra or postoperative complications. Aims This retrospective study aimed to identify the anatomy and anatomical variations of the IAN using soft tissue imaging (pulse sequence magnetic resonance imaging [MRI]). Materials and Methods This study was designed as a retrospective Consolidated Standards of Reporting Trials (CONSORT) study. In total, 220 MR images were obtained. Nutrient canals (NCs) were classified as intraosseous and dental NCs, while bifid MCs (BMCs) were classified as forward, retromolar, and buccolingual canals. IBM SPSS Statistics 22 was used. Kolmogorov–Smirnov and Shapiro–Wilk tests, descriptive statistical methods (means, standard deviations, and frequencies), and the Chi-square test were used. Statistical significance was set at P < 0.05. Results In total, 220 patients (172 females and 48 males) were evaluated. NCs were present in 92.3% of all MCs and were significantly higher in patients aged <25 years. BMCs were observed in 106 patients (24.1%). The most common BMC of MC/IAN was in the forward canal (14.4%), followed by the retromolar canal (7.5%). Conclusion Although previously, the dental canal was considered as an anatomical variation, this study revisited the classification and suggested that dental canals are anatomical structures.
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... Up to date the mandibular canal has been the subject of various studies aimed on analysis of its anatomical variation, as well displaying its course inside the mandible using distinct imaging modalities and dissecting techniques performed on the human mandibles [13,14]. Topographic relationship between the mandibular canal, facial profile, dentition and other neighboring anatomical structures has been a scope of interest of both anatomists and clinicians specialized in the field of dentistry, endodontics and maxillofacial surgery. ...
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The clinical issues related to the anatomical variation of the mandibular canal have been extensively analyzed since the 19th century. Evolving dentistry techniques and advancements in the prosthetics forced to collect detailed information about anatomical variations of the mandibular canal due to its neurovascular content. Therefore, its radiographic imaging became an essential part of the oral surgery, in order to avoid complications resulted from an accidental damage of the mandibular canal.
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... This study confirmed previous findings of accurately visualizing the IAN's tissue within the osseous boundaries of the MC [15,19,20,40]. More precisely, high-resolution MRI displays the entire neurovascular bundle (NVB) composed of the IAN, which is divided into a larger mental nerve and a smaller incisive nerve [41], and the inferior alveolar artery (IAA), which is located within the MC [42]. Yu et al. showed in a histomorphometric analysis of the NVB at the MTM level that the IAN represented 32.4% and the IAA represented 4.5% of the area [43]. ...
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... 4 Considering the potential risk from the exposure to ionizing radiation and the only limited visualization of soft-tissue structures, there has been a continued interest in alternative approaches for the generation of dental images. Previous studies have shown standard MRI sequences to be able to visualize and assess a wide range of dental conditions: pulp vitality, 5,6 apical periodontitis, 7 impacted teeth, 8 trigeminal and mandibular nerve bundles, [9][10][11] and function of the temporo-mandibular joint. [12][13][14][15] The increased soft-tissue contrast in MRI also allows for further characterization of apical bone lesions, which is not possible with cone beam computed tomography. ...
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... Neben diagnostischen Fragestellungen wie der Fehlstellung von Zähnen [69] oder der Lokalisation von okkultem Karies [68,70], gab aus auch mehrere Veröffentlichungen, die sich mit der Darstellung des Nervus Mandibularis (N. Mandibularis) beschäftigten [74,75,76,77]. ...
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Neue Therapieansätze durch Tissue Engineering erfordern gleichzeitig angepasste Diagnosemöglichkeiten und nicht-invasive Erfolgskontrollen. Speziell die 3D-MR-Bildgebung ist ein vielversprechendes Instrument, um Parameter mit hoher räumlicher Präzision zu quantifizieren. Vor diesem Hintergrund wurden im Rahmen dieser Arbeit neue Ansätze für die hochauflösende 3D-MRT in vivo entwickelt und deren Eignung im Bereich des Tissue Engineerings gezeigt. Welchen Vorteil die Quantifizierung von Parametern bietet, konnte im Rahmen einer prä-klinischen Studie an einem Modell der Hüftkopfnekrose gezeigt werden. Der Therapieverlauf wurde zu verschiedenen Zeitpunkten kontrolliert. Trotz der niedrigen räumlichen Auflösung, konnten durch eine systematische Auswertung der Signalintensitäten von T1- und T2-FS-gewichteten Aufnahmen Rückschlüsse über Veränderungen in der Mikrostruktur gezogen werden, die darüber hinaus in guter Übereinstimmung mit Ergebnissen von ex vivo µCT-Aufnahmen waren. Dort konnte eine Verdickung der Trabekelstruktur nachgewiesen werden, welche sehr gut mit einer Signalabnahme in den T1-gewichteten Aufnahmen korrelierte. Die radiale Auswertung der Daten erlaubte dabei eine komprimierte Darstellung der Ergebnisse. Dadurch wurde eine effiziente Auswertung der umfangreichen Daten (verschiedene Tiere an mehreren Zeitpunkten mit einer Vielzahl an Einzelaufnahmen) ermöglicht und eine unabhängige Bewertung erreicht. Um die Limitationen der begrenzten Auflösung von 2D-Multi-Schichtaufnahmen aufzuheben, wurden neue Ansätze für eine hochaufgelöste 3D-Aufnahme entwickelt. Hierfür wurden Spin-Echo-basierte Sequenzen gewählt, da diese eine genauere Abbildung der Knochenmikrostruktur erlauben als Gradienten-Echo-basierte Methoden. Zum einen wurde eine eigene 3D-FLASE-Sequenz entwickelt und zum anderen eine modifizierte 3D-TSE-Sequenz. Damit an Patienten Aufnahmen bei klinischer Feldstärke von 1,5 T mit einer hohen räumlichen Auflösung innerhalb einer vertretbaren Zeit erzielt werden können, muss eine schnelle und signalstarke Sequenz verwendet werden. Eine theoretische Betrachtung bescheinigte der TSE-Sequenz eine um 25 % höhere Signaleffizienz verglichen mit einer FLASE-Sequenz mit identischer Messzeit. Dieser Unterschied konnte auch im Experiment nachgewiesen werden. Ein in vivo Vergleich der beiden Sequenzen am Schienbein zeigte eine vergleichbare Darstellung der Spongiosa mit einer Auflösung von 160 × 160 × 400 µm. Für die Bildgebung des Hüftkopfs mit der neuen Sequenz waren jedoch aufgrund der unterschiedlichen Anatomie weitere Modifikationen notwendig. Um längere Messzeiten durch ein unnötig großes Field-of-View zu vermeiden, mussten Einfaltungsartefakte unterdrückt werden. Dies wurde durch die orthogonale Anwendung der Anregungs- und Refokussierungspulse in der TSE-Sequenz effizient gelöst. Technisch bedingt konnte jedoch nicht eine vergleichbare Auflösung wie am Schienbein realisiert werden. Der Vorteil der 3D-Bildgebung, dass Schichtdicken von deutlich weniger als 1 mm erreicht werden können, konnte jedoch erfolgreich auf den Unterkiefer übertragen werden. Der dort verlaufende Nervus Mandibularis ist dabei eine wichtige Struktur, deren Verlauf im Vorfeld von verschiedenen operativen Eingriffen bekannt sein muss. Er ist durch eine dünne knöcherne Wand vom umgebenden Gewebe getrennt. Im Vergleich mit einer 3D-VIBE-Sequenz zeigte die entwickelte 3D-TSE-Sequenz mit integrierter Unterdrückung von Einfaltungsartefakten eine ähnlich gute Lokalisierung des Nervenkanals über die gesamte Länge der Struktur. Dies konnte in einer Studie an gesunden Probanden mit verschiedenen Beobachtern nachgewiesen werden. Durch die neue Aufnahmetechnik konnte darüber hinaus die Auflösung im Vergleich zu bisherigen Studien deutlich erhöht werden, was insgesamt eine präzisere Lokalisierung des Nervenkanals erlaubt. Ein Baustein des Tissue Engineerings sind bio-resorbierbare Materialien, deren Abbau- und Einwachsverhalten noch untersucht werden muss, bevor diese für die klinische Anwendung zugelassen werden. Die durchgeführten in vitro µMR-Untersuchungen an Polymerscaffolds zeigten die reproduzierbare Quantifizierung der Porengröße und Wandstärke. Darüber hinaus wurde eine inhomogene Verteilung der Strukturparameter beobachtet. Die Ergebnisse waren in guter Übereinstimmung mit µCT-Aufnahmen als Goldstandard. Unterschiedliche Varianten der Scaffolds konnten identifiziert werden. Dabei bewies sich die MR-Bildgebung als zuverlässige Alternative. Insgesamt zeigen die Ergebnisse dieser Arbeit, welche Vorteile und Anwendungsmöglichkeiten die 3D-MRT-Bildgebung bietet, und dass auch mit klinischer Feldstärke in vivo Voxelgrößen im Submillimeterbereich für alle Raumrichtungen erreichbar sind. Die erzielten Verbesserungen in der räumlichen Auflösung erhöhen die Genauigkeit der verschiedenen Anwendungen und ermöglichen eine bessere Identifikation von kleinen Abweichungen, was eine frühere und zuverlässigere Diagnose für Patienten verspricht.
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Article
Full-text available
  • Sep 2017
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Abstract Background Modern imaging techniques such as computed tomography (CT) and magnetic resonance imaging (MRI) have the advantage of producing images without superimposition. Whilst CT is a well-established technique for dental diagnostics, MRI examinations are rarely used for the evaluation of dental diseases in horses. Regarding equine endodontic therapies which are increasingly implemented, MRI could help to portray changes of the periodontal ligament and display gross pulpar anatomy. Knowledge of age-related changes is essential for diagnosis, as cheek teeth and surrounding structures alter with increasing age. The aim of the present study was to highlight the advantages of CT and MRI regarding age-related changes in selected equine cheek teeth and their adjacent structures. Results The CT and MRI appearances of the maxillary 08 s and 09 s and adjacent structures were described by evaluation of post-mortem examinations of nine horses of different ages (Group A:
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High resolution MRI of the mandibular canal at 1.5T: a comparison of gradient and spin echo sequences
Article
  • Oct 2016
  • DENTOMAXILLOFAC RAD
Objectives: The precision of localizing the mandibular canal prior to surgical intervention depends on the achievable resolution, while identification of the nerve depends on the image contrast. In our study we developed new protocols based on gradient and spin echo sequences. The results from both sequences were quantitatively compared for their agreement to identify the most suitable approach. Methods: By limiting the field of view to one side of the mandible, 3D acquisitions with T1-weighted gradient and spin echo sequences were performed with 0.5x0.5x0.5mm³ resolution within 6.5min covering the mandibular canal from the mandibular to the mental foramen. Aliasing artifacts were suppressed by different techniques. A manual segmentation of the mandibular canal from seven healthy volunteers was performed on this section by three different observers. Surface distance of the segmented volumes was computed between both sequences as well as between the different observers as a measure of equality. Results: The quantitative comparison of the segmentation resulted in an average surface distance of (0.26±0.05) mm between both sequences and an inter-observer difference of (0.26±0.08) mm for gradient and (0.29±0.07) mm for spin echo data. By repeated evaluation a difference of (0.15±0.02) mm for gradient and (0.18±0.03) mm for spin echo data was observed, indicating a slightly higher variability for spin echo images. Conclusion: Both sequences can be used to achieve high resolution images with good contrast and can be used for precise localization of the mandibular canal. Despite a slightly increased difference for the spin echo data, the advantage of an easy and robust setup remains.
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  • Jan 2016
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Location of the mandibular canal: Comparison of macroscopic findings, conventional radiography, and computed tomography
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Full-text available
  • Feb 1989
Four mandibular specimens were radiographically examined bilaterally to locate the mandibular canal. The following radiographic techniques were used: periapical and panoramic radiography, hypocycloidal tomography, and computed tomography (CT). The distance from the crest of the alveolar process to the superior border of the mandibular canal was measured in millimeters on all radiographs. The specimens were then sectioned, and the location of the mandibular canal (as measured on contact radiographs of the sections) was compared with measurements made on the other radiographs. The results showed that CT gave the most accurate position of the mandibular canal and is therefore probably the best method for preoperative planning of the implant surgery involving the area close to the mandibular canal.
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Multiplanar MR and anatomic study of the mandibular canal
Article
Full-text available
  • Apr 1996
To evaluate the MR appearance of the mandibular canal and its contents. Cadaveric mandibles were imaged at 1.5 T and 3 T, then sectioned with a cryomicrotome. The size, shape, signal intensity, and pattern of structures in the mandibular canal were identified on MR images by comparing them with corresponding anatomic sections. The inferior alveolar nerve and connective tissue were identified on the 1.5-T and 3-T images in the mandibular canal. Within the nerve the axon bundles were distinguished from the nerve sheath on the 3-T images. This study suggests that MR images can show excellent anatomic detail in the mandibular canal.
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[Localization of the mandibular canal: experimental comparison of four types of radiological examination]
Article
  • Jul 1991
This investigation, involves eight dry mandibles, and compares four of radiological examinations to allow the measurement of the depth of the mandibular canal in relation to the alveolar crest. It showed that their (ability to detect the mandibular canal) differed significantly: coronal tomography: 64% retro-alveolar X-ray: 83% orthopantomography: 85% coronal tomodensitometry: 100% The retro-alveolar X-ray appears to have the best cost/information ratio, while the coronal tomography must be left aside.
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Cross-sectional tomography. A diagnostic technique for determining the buccolingual relationship of impacted mandibular third molars and the inferior alveolar neurovascular bundle
Article
  • Jan 1991
  • Oral Surg Oral Med Oral Pathol
Twenty-two patients with 31 impacted mandibular third molars were examined with a new, precise, cross-sectional tomographic technique to assess the radiographic size, shape, branching pattern, location, and degree of cortication of the mandibular canal, and the inclination of impacted mandibular third molars in the buccolingual plane. The mandibular canal, including bifid canals, was accurately identified in 30 cases (96.8%). The cross-sectional appearance of the canal was an uncorticated, or partially corticated, radiolucent oval that measured on average (+/- SD) 2.9 +/- 0.7 x 2.5 +/- 0.6 mm in diameter. It was located more frequently (45.2%) on the buccal aspect of the impacted mandibular third molar. About 60% of the mandibular canals notched the inner cortical plate of the mandible or the third molar root surface. Cystic expansion and quantification of cortical bone destruction were readily assessed by this technique. It was concluded that diagnostic information obtained from cross-sectional tomograms significantly aids the oral and maxillofacial surgeon during the preoperative diagnostic workup and that the radiation risks are comparable to those of other accepted localization techniques.
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Pre-surgical dental implant assessment by magnetic resonance imaging
Article
  • Feb 1996
The use of magnetic resonance imaging (MRI) for pre-surgical implant assessment of available bone in the maxilla and mandible is described. An acrylic surgical template with suitable MRI reference markers allows potential implant sites, as chosen on the MR images, to be accurately identified at surgery. MRI is a tomographic modality capable of giving accurate information on the three-dimensional relationships of all the relevant anatomic structures. Our results show that MRI is reasonably tolerant of artifacts caused by metal pins and amalgam fillings. Unlike computerized tomography (CT) and other x-radiographic techniques, MRI uses no ionizing radiation, and is capable of angulating and offsetting its scan plane at will. Good bone detail is available because cancellous bone yields a strong signal from the marrow fat, while cortical bone and dental enamel are dark. The excellent anatomic detail provided by thin-slice high-resolution MRI allows for assessment of the suitability of sites to receive an implant in terms of bone quality and thickness, and the relative position of the site to important structures such as the inferior dental nerve and nasal sinuses. The MRI technique used is described in detail. The principles underlying image contrast are outlined where appropriate and examples shown. To date, we have used MRI in conjunction with rotational panoramic x-rays (OPG) to plan 26 implants (21 maxillary, 5 mandibular) in 12 patients.
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