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Morphology of the mental foramen;a must know in clinical dentistry

Authors:
  • College of medicine, Riyadh, KSA
INTRODUCTION
he mental foramen is an oval/circular opening on
the anterior surface of the mandible, located
below or between the premolars, approximately
midwaybetweenthealveolarcrestandlowerborderofthe
mandible. Mental foramen holds strategic importance in
clinical dentistry and oral surgery. Its accurate
identificationdetermines the effectivenessofnerveblocks
and prevention of post operative neurovascular
complications in the mental region like neuro-sensory
disturbances, paralysis, hemorrhage, altered sensation,
orofacial pain, atypical neuralgia etc. Studies highlight a
clearracialtrendintheshape,size,antero-posteriormodal
position (ranging from sub-canine to sub-molar) and
number (multiple /absent) of the mental foramen. This
review aims to elucidate the normal morphology of the
MF and its commonly occurring variations with a view to
facilitatethe accurateidentificationofMFduringinvasive
procedures of the lower face, thereby limiting post
proceduralcomplications.
An extensivereview of published literaturewas done
through use of general and meta search engines (google
scholar, pubmed, ovid, science direct) to harvest
prominentmedical database(medline,embase,cochrane).
The search strategies used were 'Mesh'(key terms used
were :mandible, mental foramen, mandibular canal,
mental nerve, mental canal etc), 'text word' searching,
'reference list' harvesting and 'related articles' feature.
Strict inclusion and exclusion criteria were applied to
select 100 articles ranging from the year 2000 through
2011,basedoncontextrelevance.
Dry skulls macroscopic investigations on Mental
T
1
2
METHODOLOGY
Inclusioncriteria:
Lecturer, Department of Anatomy, Faculty of Medicine,
Jazan University
Correspondence: Tabinda Hasan<drtabindahasan@gmail.com>
OBJECTIVE:
METHODOLGY:
RESULTS:
DISCUSSION:
CONCLUSION:
KEYWORDS:
Howtocitethisarticle:
The mental foramen is an oval or circular opening on the anterior surface of the human mandible,
through which the inferior alveolar nerves and vessels, after passing through the inferior alveolar canal, exit as
mental nerves and vessels. It is a morphologically and clinically important landmark for anatomists, dentists and
orthognathic surgeons alike. This paper aims to elucidate the anatomy and clinics of mental foramen in human
mandibles General and meta search engines were employed to conduct an extensive review of published
medical literature with strict inclusion and exclusion criteria in order to highlight the morphologic characteristics
and commonly occurring variations of mental foramen in humans. 1000 representative studies ranging from the
year1956through 2011weresystematicallyanalyzed,based on contextrelevance.
Available literature indicates that the common position of the mental foramen is below or between
mandibular premolars .Variations in foramen number (multiple or absent foramen) and modal location (subcanine
tosubmolar)areoftenencountered and holdimportantneurovascularimplications.
The mental foramen has strategic importance in determining the effectiveness of nerve blocks in
dentistry and post operative success outcomes of invasive procedures involving the lower jaw. Mental foramen
morphologyand variations arelargelyinfluencedbydemographics,race and ethnicity.
Athorough knowledge of the mentalforamenanatomyanditscommonlyoccurringmorphologic
variations can significantly reduce the incidence of misjudgments in clinical dentistry and post procedural
parasthetic,paralytic and hemorrhagic complicationsofthementalregion.
Mandible,Mentalforamen,Mental nerve.
HasanT.Mentalforamenmorphology:amust knowinclinicaldentistry.JPakDentAssoc: 2012:03;00-00
MENTAL FORAMEN MORPHOLOGY: A MUST KNOW IN
CLINICAL DENTISTRY
Tabinda Hasan MBBS, MD
REVIEWARTICLE
00 JPDA Vol. 21 No. 03 Jul-Sep 2012
_
foramina, investigations with plane radiography,
periapical radiography and computed tomography
highlighting foramen gross morphology and
morphometry, retrospective analysis of mandibular and
mental regions, Evaluative studies to detect the
frequency, size, number and modal position of mental
foramina, reviews dealing with age and race related
variations of mental foramen or post operative
complicationsof the sub-mandibularregion.
Exclusion criteria: Studies on child skulls, animal
mandibles and dry mandible researches where race or sex
were unidentified ,Studies with exclusive or excessive
detailing on histology and development of the mental
foramenwereexcluded from the review.
Key journals from Jazan medical library were hand
searched(British dental journal, Saudi dental journal,
Americanjournalof dentistry,Journal of anatomy,Journal
of American dental association, American Journal of
orthotics, Archives of oral biology etc.); along with
consultation from experts of the field and directly
contacting an author in one case for further information.
Endnotereferencemanagement systemwasused.
MF represents the termination of the mental canal.
The inferior alveolar nerves and vessels, after traversing
the mandibular canal, exit through the MF as the mental
nervesand vessels. These formimportantinnervations for
the lower jaw, cheek, teeth and lip. Developmentally, MF
is an ideal model to study bone remodeling due to
presence of neurological, vascular and primordial
contents. It is the determinant of mandible maturity and
symmetry pattern of the mental triangle. There are
discrepancies in studies regarding the shape, size, modal
position and number of MF in human mandibles. These
discrepancies result from naturally occurring differences
in facial structure, jaw skeleton size and feeding habit
inducedboneremodelinginmandiblesof different human
races.Anotherreasonfor diversificationin observationsis
the difference in strategies used to record data about MF;
ranging from direct measurements to digital imaging
,conventional panoramic radiography, computerized
tomographicscansetc.
Morphometric studies reveal the height of MF to
range from 2.5 to 5.5 mm (average 3.5mm) and thewidth
rangingfrom2to5 mm (average 3.6 mm).
The shape of MF is predominantly oval and less
commonly circular. Different shapes have been observed
in different studies.(Table 1 ) The direction of exit of MF
on the buccal cortical plate of mandible is usually
posterosuperior, with an average inclination of about 97 ;
though other exit patterns exist, like superior, labial,
mesial and posterior. A continuous bony canal is not
always present between mandibular andmental foramina.
It may lack definite walls, or end abruptly into multiple
spread out canaliculi. Bilateral symmetry of the canal is
common,whereasduplications areinfrequent.
The most common location is below the second
premolar. Otherpositionsvaryfrombeingbelowthefirst
premolar, between the two premolars, below the first
molar or below canines. (Table2) The last two positions
are relatively rare. Clear racial trends have been observed
in the MF location in the horizontal plane; below the
second premolar inmongoloids, between the premolars in
Caucasians and between the second premolar and first
molar in blacks. Vertically, MF is placed slightly above
the midpoint of the line joining the mandibular lower
border and alveolar crest. The distance of MF from
symphysis mentii ranges between 22 to 31 mm and 10 to
15 mm from the lower cortex of the mandible. The
location of MF also changes with age. It islocated closer
to the lower border of mandible in adults, nearer to the
DISCUSSION
3
4
5
o
12
13
12
Size:
Shape:
Location:
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JPDA Vol. 21 No. 03 Jul-Sep 2012
Mental foramen morphology
Hasan T
Author Year Oval MF Round MF Race/ region
Gershenson 1986 65.5% 34.5% Israel
Mbarji orgu 1998 56% 44% Zimbabwean
Oguz O 2002 92% 8% Turkish
Igbigbi 2005 70% 30% Malawian
Prabodha 2006 67% 33% Srilanka
Fabian 2007 54% 46% Tanzania
Oliveria J 2009 72% 27% Japnese
Ilayperuma 2009 59% 41% Srilanka
Siddiqui 2010 70% 30% Western India
Singh 2011 10% 90% West India
Table No 1: Shape of mental foramen (MF) as observed in
various studies 6-11
alveolar marginin children and midway in adolescents .In
old age related bony resorption, it seems to move further
upwards, so that inextreme cases, it may open directlyat
the alveolar crest. These positional variations must be
respectedduringosteotomy procedurestoavoiddamage.
Though existenceof asingle MFis themost common
presentation, variations like supernumerary (accessory
MF) or absent foramen are also encountered. (Table3) In
f a c t , p r e s e n c e o f a c c e s s o r y f o r a m i n a
(double>triple>quadruple) is a much more common
phenomenon than absence. (Table4) This phenomenon
occurs due to splitting of the mental nerve into several
fasciculi before the development of MF during the 12th
week of intrauterine life. Such variations are often
accidently discovered during routine therapeutic or
diagnostic oral procedures. The incidence of accessory
foramen differs among races: being more frequent in
Caucasiansthan non Caucasians.
The presence of supplementary blood vessels or
nerves in assessory MF hold clinical significance as
portals of anesthetic and post operative neurovascular -
hemorrhagic /paralytic complications during implant
procedures. Rarely, they may play an unexplained role in
thespreadof tumors of the mental region.
Absence of MF is an extremely rare occurrence and
reports of the same are quite infrequent. The key
underlying reasons for absence may include congenital
agenesis, hyperplasic bony lesion, posttraumatic fibrosis
or age related bone resorption induced positional ascent
and loss of MF at the alveolar crest. Occasionally, false
reportings of apparent MF absence may arise from poor
quality imaging or patient position induced misalignment
and superimposition of the foramen with other bony
structures. The absence of MF is not related with the
perviousnes of inferior alveolar canal; in fact in all the
above reported cases of absence, authors have described
the inferior alveolar canal to be partially or completely
pervious. MF absence may cause sensory alterations in
the lower jaw because of absence of any exit portal for
mentalnerves.
Inferior alveolar anesthesia is administered routinely
in dental practice and unfortunately it is not always
successful. Thecommon cause of failure in this anesthetic
Number:
ClinicsofMF:
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Mental foramen morphology
Hasan T
Author Year Location of Mental
foramen
Percentage of
occurrence
Race / Region
Fish et al 1976 Between premolars
Below 2ndpremolar
70%
20%
Caucasian
Wang et al 1986 Below 2nd premolar 59% Chinese
Kekere Ekun et al 1989 Below 2nd premolar
Between premolars
56%
27%
Nigerian
Santini eta l 1990 Below 2nd premolar 53% Chinese
Santini eta l 1990 Between 1st & 2nd
premolar
65% British
Philips et al 1992 Below 2nd premolar 65% Unknown
Bergmane t al 2001 Below 2nd premolar
Between premolars
61%
36%
Unknown
Negow et al 2003 Below 2nd premolar 70% Malaysian
Olasoji etal 2004 Between apex of 1st
& 2nd premolar
65% Nigerian
Neiva et al 2004 Between premolars
Below 2ndpremolar
58%
42%
Caucasian
Apin Hasmit et al 2006 Below 2nd premolar 65% Thailandian
Gignor etal 2006 Between 1st &2nd
premolars
72% Turkish
Kim et al 2006 Below 2nd premolar 64% Korean
Fabian et al 2007 Below 2nd premolar 45% Tanzan ian
Location of Mental Foramen as observed in
various studies
Table No 2: 6-8
Popuilations Incidence of accessory
mental foramina
Freanch
American Whites
American Blacks
Greeks
Russians
Hungarians
Melanese
Egyptians
Japanese
Asian Indians
2.6%
1.6%
5.4%
3.3%
1.5%
3%
9.7%
3.6%
12%
1.5%
Table No 3: Occurrence of accessory mental foramina in
different populations.4
procedure is mis-placement of the hypodermic needle
because of improper evaluation of anatomic landmarks.
Theviolationof mentalforamenbyanimplantmayleadto
permanent injury to the mental nerve and permanent
paresthesia or anesthesia of the lower lip. Accurate
localization is therefore extremely important in order to
avoidsuchfailures.
Radiography is the only available noninvasive
medium for diagnosis and treatment planning of major
surgical procedures of the mandible. Panoramic
radiographs are commonly used for screening, diagnosis,
and for selecting the best surgical approach. Panoramic
radiography based appearance of MF has been classified
inTable5 .
Digital imaging was first introduced in dentistry for
intraoral radiography, but is now widely available for
panoramic radiography. The advantages of digital
techniques compared with film techniques are fast
communication of images, the small storage space needed
and lower contamination of the environment. However,
radiographic images often lack sufficient information in
the bucco-lingual direction and are prone to linear
distortions and superimpositions induced by patient
positioning, contrast, brightness & magnification values.
Delineation and compromised visibility of MF in relation
to other anatomical landmarks of the jaw as visualized on
panoramic radiographs can lead to in-correct prosthetic /
surgical planning in the mental region. Conventional
panoramic radiographs have been generally reported as
being more accurate than digital panoramic images while
computerized tomography(CT) scans yield the best
results; with minimum chances of errors. Clinicians
should keep in mind these measurement discrepancies.
Accurate localization of the mental and mandibular
foramens, with a measurement error less than 1mm is
important to avoid complications during periapical and
orthognathic procedures. Measuring a safety zone in mm
fromthealveolarcresttothecoronalmarginoftheMFcan
limitdamages.
Presence of a mesial loop of mental nerve poses
significant clinical challenges. It is an extension of the
inferior alveolar neurovascular bundle anterior to the MF,
which doubles up to enter the MF before finally exiting it.
Cadaveric dissection data on the prevalence or length of
mesialnerveloop doesnotcorrelatewitheitherpanoramic
/periapicalimages or CT scans.(Table6)
It is, however, a rare occurrence and predetermined
safety guidelines can reduce chances of accidental
damageto relatedstructuresinthisarea.
There is dire need for determining 'safety guidelines' and
'clinical recommendations' based on standardized
national and international criterion with special
consideration of race or age specific variability of MF in
variouspopulations.
Some relevant clinical recommendations are
suggestedbelow:
1-Mandatory radiographs (periapical or panoramic) and
preferably CT scans for viewing MF morphology and
accurately accessing its location prior to implants or any
otherinvasiveproceduresof thesub-mandibularregion.
2- Updated records in medical literature and routine
anatomy text books on MF morphology and
morphometry; with special reference to modal location,
shape and commonly occuring variations in major ethnic
groupsoftheworld.
3- Considering the possible presence of 'Mesial loop of
mental nerve' anterior to the MF, it is recommended to
leave a '2mm Safety zone' between the coronal aspect of
thenerveandthe intendedimplant.
4- Since paresthesia, bleeding and inadvertent nerve
damages are common in case of positional misjudgments
of MF, it is therefore recommended to accurately localize
the mental foramen radiographically prior to any attempt
ofadministrationof routine mentalnerve blocks.
The MF is an important landmark for implant
placement in the foraminal region. The position and
number can vary, radiographs can be misleading and a
mesial nerve loop may be present. These aspects must be
considered by doctors prior to invasive procedures of the
jaw, for safe clinical practice.An adequate knowledge of
the gross morphology and clinically relevant anatomic
features of MF in different populations holds strategic
importance for anthropologists, anatomists and dentists
alike
CONCLUSION
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Mental foramen morphology
Hasan T
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Mental foramen morphology
Hasan T
... Inter-populations and regional differences in size and location of the mental and mandibular foramina has been reported (Green 1987;Moiseiwitsch and Hill 1998;Nayarana and Prashanthi 2003;Hasan 2012;Shenoy et al. 2012). Thus, its position, size, and number need to be considered before preparing osteotomy and other surgical procedures in the foraminal area. ...
... Williams and Krovitz (2004) also asserted that this position is maintained at birth and remains mostly stable during the deciduous eruption. During the eruption of the second molar, the mental foramen generally migrates to a position inferior to the second premolar (Hasan 2012;Narayana and Prashanthi 2003). ...
... The results derived from different studies (please see Tab. 9 and 10 for details) may be flawed due to the application of different methods (Hasan 2012). In addition, the observed differences between right and left sides of the mandible may result from chewing habits (unilateral) (Sójka, Hędzelek 2011). ...
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Full-text available
Aim: In face anatomy and surgery, variation in the presence, number, location, and size of the mental foramen is discussed. Knowledge of the location of the mental foramen canal, which may led due to the possibility of accidental injury of the neurovascular bundle passing through this canal may lead to anesthesia. This study aimed to present selected anatomical features of human mandibles, focusing on the morphology of the mandibular canal and its neurovascular bundle exit in populations with different socio-economic status. Material and methods: Selected well preserved and unharmed human skulls (N= 169) (50.3% males, 49.7% females) from two populations (rural and outskirts) from Poland were used. Populations differed in socio­economic statuses. Results: Obvious dimorphic differences in each analyzed population were stated and inter-population differences were observed as well. In an outskirt population sexual dimorphism was more evident. Those differences should be considered when approaching the mandibular canal during anesthetic, surgical and forensic procedures. Discussion: The occurrence of the mental foramen is relatively constant, but location is variable, and thus, each individual may exhibit a different arrangement of bundle exits. Both the position and the direction of the exit of the neurovascular bundle were similar to other European population. However, differences in localization between those two investigated populations were observed. This may suggest that not only genetic but also environmental factors, such as living conditions and diet (which affects developmental stability), may influence the morphology of the mandibular features.
... [2] Mental foramen location also shifts with age and different ethnic groups. [3] Age has an effect on who is superior and who is inferior. In young children, it is located at the lower mandibular border; in adolescents, it is situated halfway between the alveolar crest and the lower mandibular border; and in adults, it is located close to the alveolar crest. ...
... [1].Greenstein and Tarnow [10] found that the shape of the mental foramen may vary from round to oval. The most frequent shape of dried mandibles was an oval, according to many authors (including Hasan T. [3], Bhandari et al. [20], Udhaya et al. [36], Roy et al. [22], Nimje et al. [23], and Vimala et al. [24]). Studies of dried mandibles by Singh and Srivastav [6], Gupta and Soni [18], and Rai et al. [31] all show that the mental foramen is typically circular. ...
... In dried mandible specimens, Singh and Srivastav [6] found that the mental foramen measured 2.8 mm in length. Oguz and Bozkir [37] and Hasan T [3] both put the average width of the mental foramen between 2.93 and 3.14 mm, while Roy et al. [22] claimed that it was around 3.01 mm. Dried mandibles were used in the study by Rai et al. [31], and they found that the average diameter of the mental foramen was 2.63 0.85 mm. ...
Article
Full-text available
The mental foramen is used by oral surgeons during procedures such as extractions, implant placements, osteotomies, nerve blocks, and other surgeries that might potentially harm the neurovascular bundle in the area. The purpose of this research was to evaluate the accuracy of the digitalized volumetric tomography (DVT) in detecting the brain foramen and in assessing its size, shape, and clarity in comparison to the orthopantomogram (OPG) (DVT). Materials and Method: Twenty-five people total took part in the research, with men and women represented equally. Expert three-dimensional (3D) software in DVT and Annotation software in OPG were used to compare and contrast the location, contour, size, and clarity of the cerebral foramen. Results: “The mental foramen was located in the center of the jaw, between the roots of the upper and lower molars and the super inferior cortex of the mandible. The mental foramen was found to be in the same place by both OPG and DVT. Most mental foramen were found to be oval, with the highest definition seen in DVT. DVT provided a more distinct picture of the anatomy, and measurements of the mental foramen were determined to be 0.51 0.06 cm, compared to 0.49 0.05 cm in OPG.
... Irregular tooth alignments or missing teeth make it challenging to determine the location of the MF. 9 Most patients have a single MF. However, variations such as supernumerary (accessory), curling, looping, or missing MFs are also encountered by clinicians. ...
... An accessory MF can occur because the mental nerve splits into several nerve fibers before the development of the MF, resulting in double, triple, or quadruple MFs. However, an accessory MF is more common than an absent MF. 9 An accessory MF is present in approximately 1% to 6% of people in different populations. A literature review showed that the MF was detectable in approximately 87% to 94% of DPRs but clearly visible in only 49% to 64% of DPRs. 10 Jacobs et al. 11 reported detection of the MF in 94% of 545 DPRs; however, only 49% were considered visible by two independent observers (oral radiologists). ...
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Full-text available
Objective To apply deep learning to a data set of dental panoramic radiographs to detect the mental foramen for automatic assessment of the mandibular cortical width. Methods Data from the seventh survey of the Tromsø Study (Tromsø7) were used. The data set contained 5197 randomly chosen dental panoramic radiographs. Four pretrained object detectors were tested. We randomly chose 80% of the data for training and 20% for testing. Models were trained using GeForce RTX 2080 Ti with 11 GB GPU memory (NVIDIA Corporation, Santa Clara, CA, USA). Python programming language version 3.7 was used for analysis. Results The EfficientDet-D0 model showed the highest average precision of 0.30. When the threshold to regard a prediction as correct (intersection over union) was set to 0.5, the average precision was 0.79. The RetinaNet model achieved the lowest average precision of 0.23, and the precision was 0.64 when the intersection over union was set to 0.5. The procedure to estimate mandibular cortical width showed acceptable results. Of 100 random images, the algorithm produced an output 93 times, 20 of which were not visually satisfactory. Conclusions EfficientDet-D0 effectively detected the mental foramen. Methods for estimating bone quality are important in radiology and require further development.
... It normally occurs singly, but up to 4 AMFs can appear on one side of the mandible. The separation of the mental nerve into several fasciculi before the development of mental foramen during the 12 th week of intrauterine life causes T the formation of accessory foramen(s) [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Studies have shown the different incidence of AMF among various ethnic groups [6][7][8][9][10][11][12][13][14]. ...
... However, the identification of AMF by the two-dimensional exams is difficult because AMF is usually smaller than 1.0mm. CBCT, which uses a lower patient dose than CT, has become established as a diagnostic tool to determine the anatomical variations [2][3][4][5][6][7][8][9][10][11][12][13]. Jaju et al. concluded that 3D reconstructions might help to identify the AMFs and differentiate them from nutritive foramina [9]. ...
Article
Full-text available
Introduction: Any additional foramen except mental foramen in the mandibular body that transfers mental nerve and vessels is called Accessory Mental Foramen (AMF). The objective of this study was the determination of the AMF using Cone-Beam Computerized Tomography (CBCT). Materials and Methods: This descriptive study was performed on 180 CBCT images selected by simple sampling method. We checked AMF presence in tangential and cross-sectional slices. Each of them had a connection with the inferior alveolar canal in the cross-sectional slices and had an opening in the buccal surface of the mandibular body. The position of AMF was assessed on reconstructed 3D CBCT images or tangential images in eight regions of postero-superior, postero-inferior, postero-anterior, antero-superior, posterior, superior, inferior, and anterior regions. We used descriptive analysis to examine the presence of AMF based on sex and age on each side. Results: The prevalence rates of AMF were 3.3% and 5.6% in the right and left sides, respectively. There were 2 (1.1%) image samples with AMF on both sides. There were no significant difference between the presence of AMF and gender (right side P=0.42, left side P=0.73) and age (right side P=0.30, left side P=0.32). Conclusion: There are variations in the incidence and location of the AMF; therefore, CBCT is an effective tool for 3D preoperative assessment of AMF. Citation: Karbasi Kheir M. Assessment of Accessory Mental Foramen by Cone-Beam Computerized Tomography. Journal of Dentomaxillofacial Radiology, Pathology and Surgery. 2018; 7(3):109-114. http://dx.
... The number of mental foramina can vary from absence up to four foramina on one side [10,11]. The presence of accessory foramina is much more common than the absence of MF [5,10]. ...
... The number of mental foramina can vary from absence up to four foramina on one side [10,11]. The presence of accessory foramina is much more common than the absence of MF [5,10]. ...
... It is recommended to leave a '2mm Safety zone' between the coronal aspect of the nerve and the intended implant. 27 The limitation of the study was that only one observer evaluated all the CBCT, thus, there could be some bias in the interpretation. However, the observer had a strict fixed parameter for reading and recording. ...
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INTRODUCTION: The mental foramen is located in a position where certain dental procedures may cause inadvertent damage to the mental nerve and lead to disorders of sensory functions such as altered sensa-tion, complete numbness, and neuropathic pain, which are uncommon but severe treatment complications with significant medico-legal implications. Hence thorough knowledge of its anatomical relation to its surrounding structures is critical while undertaking dental procedures AIM AND OBJECTIVE: To investigate the size, shape, and position of the mental foramen (MF), its distance from adjacent teeth and mandibular borders, and the pattern of the inferior alveolar canal using CBCT in the Indian subpopulation DESIGN: This was a retrospective, cross-sectional study METHODS: The study evaluated 310 CBCT scans (179 males, 131 females) in axial, sagittal, and coronal planes. CBCT scans were evaluated, mapped and measured for all the parameters listed above based on age and sex. Data were analyzed using ANOVA, independent't-test, and chi-square test RESULTS AND CONCLUSION: The size of MF is independent of age and sex; the most frequent shape of MF was Type III (round); location was below the apex of the second premolar (p>0.05). The distance of MF from the nearest root apex decreased with an increase in age and more in females than males (p>0.05). Inferior Alveolar Nerve Canal (IAC) pattern was perpendicular, and linear patterns of exit at MF were more common than anterior loops in all age groups
... It is important to differentiate Accessory Mental Foramina (AMF) from nutritive vascular canals and fistulas. Supplementary blood vessels or nerves in AMF may be significant for anesthesia procedures and the knowledge about their presence could be used to avoid post-operative complications (hemorrhages and sensory disturbances) during implant installations [2][3][4]. ...
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The purpose of this study was to assess the incidence, location, and sizes of the accessory mental foramina in Bulgarian population using Cone-Beam Computed Tomography (CBCT). The CBCT records of 1400 Bulgarian patients were evaluated for Accessory Mental Foramina (AMF) by two expert radiologists familiar with CBCT interpretation. Their presence and location in relation to the Mental Foramen (MF) were assessed using axial, panoramic and cross-sectional 2-dimensional CBCT images. The long and short axes diameters of the AMF were also measured. Accessory mental foramina were observed in 3.86% of the patients: up to two foramina on one side, unilaterally presented in 94.4% of cases with AMF. Their location regarding MF was distally and inferiorly in 62.9%. In 35.5 % of cases with AMF the foramen was situated above the level of MF and therefore needs special attention before surgery. The mean inner long and short axis diameters were 1.5 mm (SD: 0.4 mm) and 1.2 mm (SD: 0.3 mm) respectively. The measurements ranged from 0.7-2.5 mm for the long axis and 0.7-2 mm for the short axis. Demonstration of AMF using CBCT can improve the surgery treatment planning in anterior part of the mandible and thus helps to avoid unwanted neurovascular damage and possible malpractice litigations. This is the first study about the incidence, location, and sizes of the accessory mental foramina in Bulgarian population and adds additional information regarding the Caucasian race.
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Introduction and aim: Mandible usually has a bilateral oval or circular mental foramen [MF] situated on the anterolateral aspect of the body of mandible. Variations of the MF are often encountered ranging from difference in incidence, shape, size, position and supernumerary [accessory MF] to even complete absence. So, the aim of the present study was to evaluate the incidence and the anatomical features of the mental foramen and the accessory mental foramen. Materials & method: 61 dry human mandibles of unknown sex were examined. Size and distance of mental foramen and accessory mental foramen from symphysis menti [Mandibular midline], inferior border of the mandible, posterior border of ramus and superior border of body of mandible were measured using vernier calliper and statistically analyzed by mean and standard deviation. Results: Bilateral mental foramina [MF] were present in all 61 [100%] mandibles. Out of 122 mental foramina [MF], 86 [70.5%] were round and 36 [29.5%] were oval in shape. Approximately half [47.54%] of MF were present below the apex of 2nd premolar tooth. MF was located approximately half way between alveolar crest and mandibular body. Bilateral AMF were present in 1.64% mandibles. All 5 AMFs were round in shape. AMF was separated from MF by a median distance of 2mm. Conclusion: The knowledge about incidence and variability in position of mental foramen and accessory mental foramen is important in order to avoid nerve damage in connection with surgical procedure and to achieve complete effect of anaesthesia after mental nerve block
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Background: Mental foramen (MF) is an important landmark to facilitate surgical, local anaesthetic and other invasive procedures. The present study was aimed to provide anatomical information on the position, morphological variations and incidence of mental foramen and accessory mental foramen.Methods: This study was conducted on 41 dry adult human mandibles in the department of anatomy, Government Medical College Srinagar, Jammu and Kashmir. Parameters like incidence, position, shape and presence of accessory mental foramen were studied.Results: Mental foramen was present bilaterally in all 41 mandibles. Accessory mental foramen(AMF) was present in 2 cases (4.87%). The most frequent position of foramen in relation to the teeth was in line with the longitudinal axis of 2nd premolar on both right (63.42%) and left (60.98%) side. Most common shape was round shape.Conclusions: Mental foramen variation often remains unnoticed and undiagnosed. Variations do exist in the position, shape, and size of mental foramen in different population groups. Present study provide the necessary data of mental foramen location and morphometry which may be useful for the surgeons, anaesthetists, neurosurgeons and dentists to carry out nerve block and surgical procedures.
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Mental foramen, an important landmark of the human mandible is the determinant of the mental triangle. It is an oval or circular opening on the anterior surface of the mandible. The mental bundle exits through the mental foramen and supplies the soft tissues of the chin, lower lip, and gingivae. Recent advancements in orthognathic surgery have increased surgical procedures in the mental region. The exact location of the mental foramen is determinant of effective nerve block and prevention of post surgical neurovascular complications. Its modal position varies according to age and ethnicity, from sub-canine to sub-molar. Variations like multiple or absent foramina hold strategic importance in clinical dentistry and are best revealed by computerized tomography scans. This case reports an extremely rare and previously undescribed anatomic variation of bilateral absence of mental foramen along with literature review of relevance to peridontologists and maxillofacial surgeons.
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Introduction: The mental foramen (MF) is a strategically important landmark during surgical interventions and anaesthetic blockage procedures involving the mental nerve. The purpose of this study was to assess various parameters pertaining to the morphology and morphometry of the mental foramen in 93 dry human mandibles. Methodology: Measurements were taken as the distance between alveolar margin and MF, distance between MF and base of the mandible, distance between symphysis menti and MF and distance between MF and posterior border of the ramus of the mandible. The study also included the relation of MF with the lower teeth (the position of the MF was recorded as lying in line with the long axis of a tooth or interdental space in one of the six types, 1 to 6). Results: The most common shape of the foramen was oval (70%). The most common position of the MF as related to the lower set of teeth was in line with the second premolar. The mean distance between symphysis menti and anterior margin of MF was 18.8mm (SD= 12.02) and 19.6mm (SD= 12.18), on the right and left sides respectively. Mean distance between posterior margin of MF and posterior border of ramus was 48.8 mm (SD=28.6) on the right side and 47.9 mm (SD=28.1) on the left side. Mean distance between alveolar crest and superior margin of MF was 10.2 mm (SD= 5.4) on right side and 10 mm (SD=5.2) on the left side. Mean distance between inferior margin of MF and lower border of the body of mandible was 9.9 mm (SD= 5.12) on the right side and 10.1 mm (SD= 5.2) on the left side. Conclusion: The study carries clinical credibility in ascertaining the accurate location of the MF and thus avoiding any unforeseen injury related to anaesthesia or dental surgeries. Key Words: Mental foramen, Mental nerve, Mandible, Morphology, Morphometry, Dental Anaesthesia
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In this retrospective study with limited cone-beam computed tomography (limited CBCT), we investigated the anatomic characteristics of the accessory mental foramina and accessory branches of the mandibular canal. The CBCT records of approximately 150 patients were evaluated, and 17 accessory mental foramina were found in 16 patients. The anatomic peculiarities of the mandibular canal that might be relevant to endodontic treatment were observed. Accessory mental foramina tended to exist in the apical area of the first molar and posterior or inferior area of the mental foramen. The accessory branches of the mandibular canal showed common characteristics in the course of gently sloping posterosuperior direction in the buccal surface area. Verification of the existence of accessory mental foramina would prevent accessory nerve injury during periapical surgery. In root canal treatment, the possibility of accessory mental foramina-related nerve paresthesia seems low unless the mental foramen and mandibular canal are injured. Limited CBCT is effective for presurgical 3-dimensional assessment of the neurovascular structures in dentoalveolar treatment.
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The antero-posterior position of the mental foramen was studied in 68 Chinese and 44 British skulls of known or calculated age at death. All skulls showed low pre-mortem tooth loss and had a good occlusion. The position of the foramen was related to the body of the mandible as well as to the standing mandibular teeth using two previously published methods. There was no significant difference in the size of the Chinese and British mandibles. There was a significant difference between the two groups when measurements relating the foramen to the body of the mandible (symphysis menti) were considered, the foraminal position being more distal in the Chinese group. The modal position of the foramen in the Chinese sample was along the long axis of the second premolar, whereas in the British sample it lay between the apices of the first and second premolar. The foraminal position apparently moved distally in both groups with age and this was likely to be associated with mesial tooth drift and age-related attrition.
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The purpose of this work was to study the morphology and morphometry of the mental foramen (MF), as well as to evaluate its morphological configuration; in addition to taking measures of its localization using as a parameter the distances of the foramen to the inferior border of the mandible and at the alveolar ridge. 80 dry mandibles were analyzed using the test of Qui-square and T test, with 5% of significance. Its average distance, on the right side, at the inferior edge of the mandible (IEM) was of 12.96(±1.57) mm and of the alveolar ridge (AR) was of 12.82(±3.4) mm. On the left side it was found distant of IEM 12.96(±1.32) mm and of the AR 12.82(± 3.22)mm. The largest horizontal diameter found was of 3.32 (± 0.91) mm to the right and 3.25 (± 0.86) mm to the left side while the largest vertical diameter was of 2.38 (± 0.63) mm on the right and of 2.39 (± 0.58) mm on the left side. It was predominantly found in the oval form, on the right side, of which 98.3% presented as a larger diameter the horizontal (type I). On the left side, all the oval foramens were classified as of type I. 76 (95%) appeared single on both sides. As to the localization related to the mandibular dentition, it was localized in similar statistic proportions between the 1 st and 2 nd premolars and above the 2 nd premolar, in 45.17% of the mandibles, on the right side. On the left side it was predominantly found between the 1 st and 2 nd premolars 48.48% of the mandibles. The study of the MF is of vital importance to the acupuncture practice, as well as to modern surgical procedures, like anesthesia, requiring a detailed and precise study of the morphology and morphometry of the area.
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The purpose of the present study was to assess the accessory mental foramen using cone-beam computed tomography (CBCT) images. A total of 157 patients were enrolled in this investigation. The mental and accessory mental foramina, which show continuity with the mandibular canal, were assessed using axial and cross-sectional, 2-dimensional CBCT images. The sizes of the mental and accessory mental foramina were measured and statistically analyzed. Also, the distance between the mental and accessory mental foramina was measured. The accessory mental foramen was observed in 7% of patients. There was no significant difference regarding the sizes of the mental foramen between accessory mental foramen presence and absence. Also, the mean distance between the mental and accessory mental foramina was 6.3 mm (SD: 1.5 mm). The accessory mental foramen, which shows continuity with the mandibular canal, could be observed in 7% of the subjects using CBCT.
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The absence of the mental foramen was investigated in 1,435 dry human mandibles (2,870 sides). The foramen was absent twice in the right side (0.06%) and once in the left side (0.03%). The meaning of this anatomical variation was commented.
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An anatomical variant in the region of the mental foramen is discussed. In these cases the inferior alveolar nerve divides into its two terminal branches only after it has exited through the mental foramen. The incisive nerve thus commences outside the mandible, and has a short extra-osseous course before it enters the mandible through a separate foramen on the same horizontal plane. For the distance between these two foramina there is no nerve supply within the mandible. The groove between the two foramina may be the remnants of the mandibular canal. The foramen through which the nerve enters the bone is a separate anatomical entity from the mental foramen and should be recognised as such. It is proposed that this foramen be named the mandibular incisive foramen.