Surgical anatomy of floor of mouth /certified fixed orthodontic courses by Indian dental academy

SURGICAL ANATOMY
OF
FLOOR OF THE
MOUTH
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

www.indiandentalacademy.co
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FLOOR OF THE MOUTH
 Lined with smooth thin mucous membrane
(stratified squamous epithelium)
BOUNDARIES:
 Anterior – ant. part of the mandible
 Either sides –body of mandible
 Posterior –base of the ant. pillar
 Inferior – mylohyoid muscle
 Superior – mucous membrane lining
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SUB-LINGUAL PAPILLAE: small
elevations seen on either side of the
lingual frenum.(sub-mandibular duct
orifice is seen on either side of the
papillae)
SUB-LINGUAL FOLD : ridge produced
by
underlying sublingual gland
extending postero-lateral from
sublingual papillae .(sub lingual duct
seen on the crest of the fold)
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Contents of the floor of the
mouth
 Muscles - Mylohyoid
- Geniohyoid
-hyoglossus
 Salivary glands – Sub-lingual
- Deep part of sub-mandibular
- Wharton’s duct
 Nerves - Lingual.N
-9th CN & 12th CN
 Blood vessels - Arteries (Lingual.A)
- Venous channels
 Tissue spaces
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Mylohyoid muscle






Triangular sheet of the muscle.
Forms a mobile diaphragm flooring oral cavity
Origin , insertion
Median fibrous raphae
POST. FREE EDGE(from where the infection
Spreads)

 Action

:- 1) Elevates FOM, hyoid bone
:- 2)Depresses mandible once the
hyoid bone is fixed

 Nerve supply :- Mylohyoid.N which lies below
the mylohyoid muscle.
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Geniohyoid muscle
 Narrow muscle, which lies above the
mylohyoid muscle.
 INFECTION spreads in b/w the pair of
geniohyoid
 Action :- Elevates & draws the hyoid bone
forward
:- Depresses the mandible.
 Nerve supply :- 1st Cervical through 12th CN.
Midline incision ( sublingual cellulitis ) should
separate this both muscles of geniohyoid
present on the either side.
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Hyoglossus muscle
 Arises from upper body & greater cornua
of hyoid bone and ascends vertically deep
to mylohyoid to enter the sides of the
toungue.
 Interdigitates with styloglossus.
 Action :- Depresses the tongue.
 Nerve supply :- 12th CN
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structures seen lateral to hyoglossus muscle :





Lingual.N
Hypoglossal.N
Deep lingual vein
Sub mandibular duct
Deep part of sub mandibular gland

Structures seen mesial to hyoglossus muscle :



Glossopharyngeal.N
Lingual A
Stylohyoid ligament
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GLANDS
 Sub-mandibular salivary gland:
(deep part)
 Lies in the gap between mylohyoid
and hyoglossus.
 Deep part is seperated from
hyoglossus by:- 1) hyoglossal N
2) deep lingual vein.

 Lingual.N lies above the deep part.
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WHARTON’S DUCT;-

Begins in the superficial lobe –
crosses the gland curving around
post margin of mylohyoid in
connection between sup & deep
lobes to emerge from ant.surface of
deep part
Runs forwards –close relationship to
lingual N .(first between mylohyoid &
hyoglossus and later between
sublingual gland & genioglossus)
opens in to sublingual papillae.
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SALIVARY CALCULI- 80% occurs in the
sub-mandibular gland
 Stone causes PARTIAL OBSTRUCTION
when it lies within the hilum of the gland
or within the duct in FOM
 Stone lying within the duct in the FOM ant.
to point at which the duct crosses the
lingual nerve ( 2nd molar region ) stone
can be removed by incising longitudinally
over the duct.
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 When the stone is proximal to
where the duct crosses the lingual
nerve, i.e at the hilum of the gland.
Stone retrieval via intra oral
approach should be AVOIDED to
prevent damage of the lingual nerve
during exploration in the posterior
lingual gutter.so extra oral
approach is preferred for submandibular gland excision & removal
of stone by www.indiandentalacademy.co duct under
ligation of the
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direct vision.

LIGATION OF WHARTON’S DUCT
The duct should be divided as
distally as possible to ensure
removal of retained stones & avoid
leaving a portion of the duct as a
blind pouch that may become
infected.

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Dissection of deep lobe and
identification of LingualN.: An imp landmark in sub-mandibular
gland dissection is posterior border
of mylohyoid muscle
 Once identified, the muscle is
retracted forwards revealing the
deep part of the sub-mandibular
gland, duct, lingual N, submandibular ganglion
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 Hypoglossal N lies deep to submandibular capsule & should not be
damaged during intra capsular dissection
 The sub-mandibular gland is attached to
lingual N through para-sym. secretomotor
fibers. Its is imperative that lingual N is
formally identified prior to division of parasym. Fibers
 The gland is now pedicled entirely on the
duct which can be identified & ligated.
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Sub lingual gland
 Extending from 2nd molar to premolar
region
 Situated in front of deep part of
submandibular gland
 Lies in b/w hyoglossus & genioglossus
 Medial to sub lingual gland lies
1) lingual N
2) sub mandibular duct
 Lateral surface of gland is in contact with
sub lingual fossa
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 Mucous retention cyst develops in
the FOM either from minor or from
sub-lingual gland
RANULA should be applied only to a
mucous extra vasation cyst arising
from sub-lingual gland
MANAGEMENT – excision of the cyst &
sub-lingual gland
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Linear incision is made parallel to
duct & SHOULD NOT extend more
posterior to the 1st molar so as to avoid
damage to lingual nerve

Plunging Ranula – arises from both
sub-lingual& sub-mandibular gland &
penetrates the mylohyoid diaphragm
to enter the neck
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 Excision is usually performed via
cervical approach removing the cyst ,
sub-mandibular & sub-lingual gland
SUB-LINGUAL DERMOID CYST- it is
opaque and lies exactly in the
midline and may extend into submental region
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LUDWIGS ANGINA
• It is a firm,acute,toxiccellulitis of the
sub-mandibular & sub-lingual spaces
bilaterally & of the sub-mental space.
• ANT.TEETH-produce sub-lingual
infection
• POST.TEETH-produce subman.space infection.
• Mylohyoid-hyoglossal cleft.
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• If left untreated—infection extends
into the lateral pharyngeal space
through buccopharyngeal
gap,causing la.edema&obstruction.
• Bil.incision into sub-mandibular
spaces with blunt dissection to the
midline suffices if a through&through
drain or bil. Drains meeting in the
midline are placed.
• This maneuver,combined with
drainage of the sub-lingual
spaces,releives the intense pressure
of edematous tissue on the airway.
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NERVES
 Lingual N - lateral to hyoglossus
 Hypoglossal N -lateral to hoglossus
 Glossopharyngeal N -medial to
hyoglossus

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Lingual nerve
 Leaves the infratemporal surface
 Passes beneath sup. Constrictor
muscle
(close to last molar).A submucosal
inj. at this is danger of introducing
an inj into sub- mandibular space
 Runs forwards,downwards,medially
b/w mylohyoid & hyoglossus
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 Continues forwards to reach the
front edge of hyoglossus( *here it
crosses below the submandibular
duct from its lateral to medial
surface)
 Running forwards & upwards it
passes b/w sublingual gland &
genioglossus

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Relationship of duct/ lingual N:
As the duct emerges from deep part, it
lies superficial to lingual nerve
Submandibular ganglion:
Suspended from lingual N, on the
surface of hyoglossus below subman. duct
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Hypoglossal Nerve

 Having crossed the ECA & ICA ,hypoglossal
N enters the mouth passing deep(i.e
above) the posterior border of mylohyoid
 Lies in b/w mylohyoid & hyoglossus
(below lingual
N)


After leaving the lateral surface of
hyoglossus the 12th CN continues forwards
on genioglossus
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12th CN has numerous connections with
lingual N
12th CN lies superficial to lingual A
Injury to 12th CN
- trauma ( mandibular #)
-tongue deviates to affected side
-atrophy, paralysis of one side of
tongue
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GLOSSOPHARYNGEAL N
-lies medial to hyoglossus muscle
-post 1/3 rd of the tongue.
Blood vessels
Lingual A
- Leaves the ant surface of ECA opp the tip of the
greater cornu of hyoid bone
Lingual A then enters FOM by running deep to
hyoglossus and turns superiorly at the ant
.border of hyoglossus to become deep lingual A
&sublingual A
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Venous channels
 Deep lingual v begins near the tip of
tongue
 At the ant. Border of hyoglossus it
receives sublingual v
 The vein ends by draining into the
facial ,lingual or IJV
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Tissue spaces in FOM
 A dental abscess from an infected lower
tooth may erode the cortex of the body of
the mandible allowing the escape of pus
into adjacent soft tissues
 If this occurs in lateral direction- pus may
enter buccal sulcus
 If this occurs in medial direction- pus may
enter FOM , neck
 *if the cortex is eroded above the
mylohyoid attachment pus enters FOM
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 *if the cortex is eroded below the
mylohyoid attachment pus enters
neck
 An abscess from post teeth is more
likely to open below mylohyoid
muscle attachment(i.e neck)
 Posteriorly it communicates freely
with the tissue spaces of the neck
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 Apical levelof roots of 5-1 1-5
is always above mylohyoid line (sub
lingual cellulitis)
 Apical root tip of 3rd molar always
below mylohyoid line. Submandibular
space (cervical cellulitis)
 1st & 2nd – above or below

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Sub lingual cellulitis
 Invades loose CT b/w geniohyoid &
involves both sides
 May spread posteriorly-cervical cellulitis
DRAINAGE (sub lingual cellulitis )
 clearing the infected spaces is by
drainage in the midline from chin to hyoid
bone
 The incision of skin should be made
transversly ( so that scar falls in neck
folds )
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 Mylohyoid muscle is incised along the
midline and then entire stock of inter
muscular CT is accessible
 Cellulitis extends laterally, below and
above the geniohyoid muscle

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Sublingual A (endangered during minor
surgical procedures or during dental
Rx
When sharp instrument slip off a lower tooth
(premolar/1st molar region ) it injures the
floor of the mouth (sublingual A) which
lies medial & inferior
to submandibular duct & lingual N
haemorrhage
control by clamping of sublingual A
if still bleeds

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Ligation of lingual A
still bleeds
Sublingual A is replaced by br.of
submentalA (br.of facial A)
*Sub lingual A is sometimes small or
even missing

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Relationship of sublingual A &
submental A to mylohyoid
muscle
 Sub-lingual A is close to upper
,inner surface of mylohyoid muscle
 Sub-mental A is close to outer
surface of mylohyoid muscle
 Sub-lingual A is ll el to sub-mental A

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Ligation of lingual A
 Exposure of lingual A is done in digastric
triangle
 After the submandibular gland is
lifted,digastric tendon becomes visible
 Pull the tendon downwards
 Hyoglossus muscle is seen with its vertical
fibres. Divide the muscle bluntly
 Lingual A is found
 Lesser’s triangle-formed by 12th CN,
post.fibres of mylohyoid and tendon of
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digastric

CA. OF FOM
 2nd most common site for oral cancer
 Most tumours occur in the ant.
Segment of the FOM to one side of
the midline
 Small tumours – simple excison
 Larger lesions and those involving
the ventral tongue and/or alveolus,
surgical access is gained through
midline or lateral mandibulectomy
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and lip split

Bone invasion by ca. of
FOM


In dentatemandible – invasion
through PDL & is nearly ALWAYS
above mylohyoid insertion
 Once the tumour has invaded the
mandible it soon enters the inferior
dental canal and the perineural
spread occurs anteriorly and
posteriorly
 In edentulous mandible – invasion
throu deficiencies in cortical bone of
alv crest
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SURGICAL ANATOMY OF
FLOOR OF THE MOUTH

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ORAL ENDOTRACHEAL
INTUBATION:MEDIAN
SUBMENTAL
(RETROGENIAL)APPROACH
 J ORAL MAXILLOFAC SURGERY
 2002;VOL:60.
 Shaukat mahmood & Edward Lello

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 Routine orotracheal intubation is
performed using a preformed
sheridon cuffed orotracheal tube.
 FIRST INCISION:A 10mm
transverse sub-mental incision is
made centerd on the facial midline.
 SECOND INCISION: A 10mm
transverse intra-oral mucosal incision
centerd on the mid sagittal plane is
made midway b/w the point of
reflection of mucosafrom the
mandible to the FOM & the submand. duct www.indiandentalacademy.co
pappilae.
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 This incision is deepened with blunt
dissection b/w the 2 geniohyoid &
genioglossus to join the sub-mental
incision.
 This tech. AVOIDS trauma to the lingual
N,sub-mand.duct,sub-lingual gland&sublingual papillae.ALSO AVOIDS sub-lingual
haematoma&edema.
 Easy to learn,quick&safe technique.
 FOR SHORT TERM POST-OPERATIVE
AIRWAY MANAGEMENT.
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THANK YOU

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Surgical anatomy of floor of mouth /certified fixed orthodontic courses by Indian dental academy

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