Dear friends, in the next few minutes

we will discuss some implications of implant dentistry

in the posterior maxilla.

As we have seen previously, the extraction of teeth

is a catalyst to a chain reaction that leads to

compromise of the alveolar bone and the soft tissues.

In the case of the posterior maxilla, we have two different phenomena

which together can significantly

reduce the availability of bone for dental implants.

The first, is the reduction of the height and width

of the alveolar ridge which occurs normally

after every extraction.

The second, is what we call the pneumatisation of the sinus.

Pneumatisation is one of the funny Greek words

that is easier to understand than to actually pronounce.

In Greek, it means to "pump air" into something, to inflate.

And exactly this is how it looks like sometimes,

the sinus cavity expands as if a balloon

is actually inflated inside.

Is there a balloon in the sinus?

Not really, but then again I like the idea!

Let's try to imagine a bit of the anatomy.

Sinus is lined with a very thin membrane,

the sinus mucosa or Schneiderian membrane.

And just like a balloon this membrane

has only one opening at the highest point, the Ostium,

where it communicates with the nose.

If you think about it, the sinus is

under mild but constant pressure changes as long as you live.

Every breath you take in,

creates negative pressure in the sinus cavity

and every time you breathe out,

the pressure becomes positive.

If the sinus membrane wasn't firmly attached on the bone

what we could see with every breath

would resemble the idea of the balloon.

And if you prefer the real thing to the animations,

take a look at this clip.

The membrane detached from the sinus walls

during augmentation surgery

as it moves following the breathing of the patient.

This is actually an elderly patient

with a thick fibrous membrane.

Sometimes the move can be much more spectacular,

especially in younger patients

with thinner and more sensitive membranes, as in this case.

So maybe the balloon metaphor

might be not so far from the reality after all!

The dynamics of the anatomy might give you a good idea

of the complexity of this area

when it comes to implant surgery.

The constant pressure changes

transferred to the mechanosensitive bone

through the sinus membrane

might contribute to the gradual expansion

of the sinus after teeth are lost.

Regardless of the cause,

a recent radiographic study estimated that

approximately 60% of the bone loss height

is attributed to the marginal alveolar ridge reduction,

while about 35% is due to the sinus pneumatisation.

This means that we often have to augment

both the sinus as well as the alveolar ridge,

in order to place the implants

in the proper prosthetic position.

Does the extent of the pneumatisation correlate with the amount of the missing teeth?

A clear answer to this is not easy

based on the existing research.

In one of our three dimensional radiographic studies

we found that the bucco-lingual width

of the residual alveolar ridge was related

to the presence or absence of adjacent teeth,

but not the height.

A good predictor of reduced bone height

appeared to be periodontal bone loss at the existing teeth

and evidence of abnormal lining of the sinus membrane.

Often, we will see that the presence of a single posterior tooth

appears to prevent major sinus expansion,

but other times,

even the loss of one single tooth

can provoke a significant downgrowth of the sinus.

What appears to be significant predictive factor

is the relation of the roots of the posterior teeth

to the actual floor of the sinus

and this is something that is not easy to evaluate

on the basis of two-dimensional radiographs.

Very often, the apical portion of the roots of the molars

are in very close proximity

or even intermingled with the sinus floor.

In such cases, extraction of the teeth

can actually lead to much faster pneumatisation of the sinus.

Consequently, in order to address

the challenges of this compromised anatomy,

sinus floor elevation and sinus augmentation procedures have been proposed

with the most established being

the Transalveolar or Osteotome technique

and the Lateral window sinus floor elevation.

Each of these approaches will have many modifications

and also specific indications and contraindications.

In general, 8 mm or more of bone height should be enough

for the placement of an implant without engaging the sinus.

Cases where we have 6 to 7 mm

combined with a flat sinus floor are well indicated

for the Osteotome technique.

Similarly, we can treat cases with 4 to 5 mm

and a flat sinus floor with osteotome,

only here, often a grafting material is recommended.

Cases with an oblique sinus floor

or with less than 4 mm of residual bone height

are typically treated with the lateral window approach.

In the case of the lateral window,

implants can be placed simultaneously with the sinus elevation

if the residual bone height is enough

to offer primary stability.

Otherwise, a two-stage procedure is followed

and implants are placed six to nine months

after the sinus augmentation.

上后牙区种植牙 (*新增内容)

口腔种植学（Implant Dentistry）

Meet the Instructors

上后牙区种植牙 (*新增内容)

口腔种植学 （Implant Dentistry）

Meet the Instructors

口腔种植学（Implant Dentistry）