Welcome to the second part

of the lecture on clinical anatomy.

Previously, we have discussed the importance

of the structure of the maxilla.

And now, we will talk about the mandible.

Ian, how do you avoid implant surgical complications?

We could avoid surgical complications

by proper assessment of the ridge morphology,

and relevant structures before implant surgery.

If we know where they are, we could stay away from them

by proper incision designs, flat managements,

and osteotomies.

To assess the anatomy,

a panoramic radiograph is very useful.

It gives you the information of the bone height,

and the location of the important structures

like the sinuses, the mandibular canal, and mental foramen.

For a standard implant case, it is quite sufficient.

However, for patients with moderate or

severe bone resorption, we would recommend

a CT scan for evaluation,

because it shows a three-dimensional view of the atrophic ridge.

Bone quality could also be assessed

and classified into different types.

In addition, detailed representations

and localizations of the bony structures

such as the septae in the sinuses, foramen,

and intra-osseous channels for nerves

and blood vessels are possible.

For the structures that we cannot assess preoperatively,

such as the nerves and blood vessels in the soft tissues,

we could only estimate

where they are with the information obtained

from human cadaver dissections or other imaging studies.

Mandible is a U-shaped bone, formed by the fusion

of two separate halves at the mental symphysis.

From the side, we can see a vertical ramus,

and a horizontal body, joined by the angle of the mandible.

The body is further divided into

the upper alveolar bone and the lower basal bone.

There are two bony extensions on the ramus.

One is the coronoid process,

while the posterior one is the condylar process,

which forms the temporomandibular joint

with the temporal bone above.

The ramus can be viewed from lingual.

Midway from its vertical height,

there is a bony projection called a lingula.

Below this, is the mandibular foramen,

which leads to a bony canal called the mandibular canal.

It travels anteriorly, and deviates sharply

towards the buccal at the premolar region

to exit as the mental foramen.

Anterior to this opening is a canal

called incisive canal where the nerves

and blood vessels serve the anterior teeth.

If the mandible is cut at different regions,

it can be shown that the mandibular canal

takes up a lingual position initially,

but gradually becomes more buccal in the premolar region.

Besides, the lingual outline of the mandible

is also more concave in the second molar region

than in the first molar region.

The nerves of the mandible that we would encounter

during implant surgeries are the lingual nerve,

and the inferior alveolar nerve.

They are both sensory branches of the trigeminal nerve.

The lingual nerve passes the lingual bony cortex

at the posterior mandible,

before descending to the base of the tongue.

The nerve supplies the sensation and taste

of the anterior 2/3 of the tongue,

and the sensation of lingual gingivae.

The lingual nerve could be damaged

during implant placement of the lower second molar,

which would cause sensory disturbance

of the tongue, and impairment of taste.

To avoid this complication, before making the incision,

we shall palpate the lingual plate

because the soft tissue can be thick

and mask the bony morphology there.

The crestal incision needs to be directed

toward the external oblique ridge distally,

and the lingual mucoperiosteum shall

be raised carefully and be protected

before drilling and implant insertion.

The inferior alveolar nerve enters

the mandibular foramen at medial side of the ramus,

and travels through the mandibular canal.

It then branches into mental and incisive nerves

at premolar region.

Before the mental nerve exits through the mental foramen,

it sometimes forms loop anteriorly.

The nerve supplies the lower lip, chin, and the lower teeth.

Trauma to the nerve would cause

different degrees of neurosensory disturbances.

The inferior alveolar nerve could be injured

during implant placement and bone graft harvesting

at the posterior mandible by drilling

or by compression of implant body.

Moreover, direct trauma of mental nerve

could occur during relieving incisions

and flat manipulations near to the mental foramen.

The external carotid artery gives off branches

to supply the mandible by the maxillary,

facial, and lingual arteries.

Maxillary artery is a long artery,

with many branches which supplies the maxilla,

nasal cavity, and muscles of mastication.

A branch called the inferior alveolar artery

supplies the mandible and the mandibular teeth.

It enters the mandibular foramen,

and travels in the mandibular canal,

and branches to become the mental artery

at the mental foramen.

The terminal branch of it is the incisive branch,

that supplies the incisors and canines.

The external carotid branches off at two points.

The first one is the facial artery,

and runs superficially across the face.

Another one, the lingual artery,

that supplies the deep structures,

like the tongue, and also the floor of the mouth.

The lingual artery has three main branches.

Also lingual supplies the posterior 1/3 of the tongue.

The deep lingual can be seen by sticking out one's tongue.

The last one is the sublingual,

which goes forward at the base of the tongue.

It has branches that penetrate the lingual plate

and form anastomosis with incisive blood vessels.

The floor of the mouth is bounded by the mylohyoid muscle.

The muscle attaches to the mylohyoid line

of the medial side of mandible,

passing downward and unite medially.

Posteriorly, it attaches to the hyoid bone.

Above the muscle lies the sublingual salivary gland,

which is closely associated

with the Wharton's duct of the submandibular gland.

The superficial and deep parts

of the submandibular gland lie at the posterior edge.

The branches of the sublingual

and submental arteries are present anteriorly.

Normally, the contents of the floor of mouth

is quite distant from the alveolar crest.

In the atrophic mandible, however,

the structures become relatively superficial.

Implant at the anterior mandible could be risky,

if the arteries are damaged.

This may cause a haematoma at the floor of mouth,

which could displace the tongue backward

and compress the airway.

Injury of the sublingual gland is also possible.

If it is damaged, mucus extravasation could occur,

and cause a swelling at the floor of mouth.

The swelling could sometimes herniate through

the mylohyoid muscle, causing submandibular swelling,

which is known as plunging ranula.

We hope these overviews have helped you

in understanding anatomy in relation to implant surgery.

Good luck and Good-bye.

解剖学：下颌骨

口腔种植学（Implant Dentistry）

Meet the Instructors

解剖学：下颌骨

口腔种植学 （Implant Dentistry）

Meet the Instructors

口腔种植学（Implant Dentistry）