Bone Grafting Explained
Over a period of time, the jawbone associated with missing teeth
atrophies or shrinks. This often leaves a condition in which there is
poor quality and quantity of bone suitable for placement of dental
implants. In these situations, most patients were previously not
candidates for placement of dental implants.
We now have the ability to grow bone where needed. This not only
gives us the opportunity to place implants of proper length and width,
it also gives us a chance to restore functionality and esthetic
appearance. There are a variety of bone grafting procedures which can
be done in our office to allow implant placement.
Jawbone and Extraction Site Preservation
When you need to have a tooth or teeth extracted, whether it be due to
decay, abscess, gum disease or injury, it is usually in your best
interest to do so in a manner which preserves as much of your
underlying jawbone as possible. From the time the teeth are removed,
significant degeneration of the surrounding bone begins to take place.
You have many options to prevent this, and it is important that you
consider them BEFORE any teeth are removed. Some of these procedures
are best performed at the time the tooth is removed. Dr. Ehsan is an
oral and maxillofacial surgeon who specializes in tooth removal,
jawbone preservation and dental implant placement.
What happens when a tooth is removed?
There is a special type of bone surrounding your teeth. This bone
is called alveolar "ridge" bone, and exists solely to support your
teeth. As soon as the tooth is removed, this bone begins to degenerate
and "melt away". This occurs in two dimensions. The first is loss of
horizontal width caused by the collapse of the bone surrounding the
socket. This makes the remaining ridge narrower than when the tooth was
present. The second is a loss of vertical height. This makes the
remaining bone less "tall". This process is faster in areas where you
wear a partial or complete denture.
Why is it important to preserve the bone?
You will have several choices of how you can replace the newly
missing teeth. All of the options rely on bone support and bone contour
for the best function and esthetics. Here is a list of the possible
options:
You may choose to replace your missing teeth with dental
implants. These are root-shaped supports that hold your replacement
teeth. The more bone support you have, the stronger the implant
replacements will be. In some cases, the bone can degenerate to a point
where implants can no longer be placed without having more complex bone
grafting procedures to create the necessary support. Obviously,
preventing bone loss is much easier than recreating the bone later.
You may choose to replace the missing teeth with a "fixed
bridge". This is a restoration that is supported by the teeth adjacent
to the missing tooth space. The replacement tooth (or pontic) spans
across the space. If the bone is deficient, there will be an unsightly
space under the pontic that will trap food and affect your speech.
Other replacement alternatives include removable partial
or full dentures. These often perform better with more supporting bone.
How can the bone be preserved?
There are two important phases in retaining your alveolar
ridge during and after the tooth extraction. Not all extractions
are the same. Dr. Ehsan will use the most careful techniques
to extract the teeth while preserving as much bone as possible.
Second, and key to preventing the collapse of the socket,
is the addition of bone replacement material to the extraction
socket.
There are several types of bone grafting materials and techniques
Dr. Ehsan will discuss the most appropriate one with you. After the
tooth is extracted, the socket will be packed with a bone graft
material and covered with a small absorbable plug, membrane or suture.
Early on, the grafting material will support the tissue surrounding the
socket, and in time will be replaced by new alveolar bone (your own
bone). This bone will be an excellent support should you choose later
to have dental implant-supported replacement teeth.
Although the bone created by socket grafting supports and preserves
the socket, it will not do so indefinitely. Placing dental implants two
to six months after the extraction and socket grafting will provide the
best long-lasting support for preserving your jawbone and allow you to
function as before. Otherwise the graft may "melt away" or resorb over
time because bone is maintained in the jawbone when it is under
function of tooth or implant.
Sinus Lift Bone Grafting
The maxillary sinuses are behind your cheeks and on top of the upper
teeth. Sinuses are like empty rooms that have nothing at all in them.
Some of the roots of the natural upper teeth extend up into the
maxillary sinuses. When these upper teeth are removed, there is often
just an egg shell thin wall of bone separating the maxillary sinus and
the mouth. Dental implants need bone to hold them in place so when the
sinus wall is very thin, it is impossible to place dental implants in
this bone.
This procedure involves elevating the sinus membrane and placing
the bone graft onto the sinus floor. This allows implants to be placed
in the back part of the upper jaw when teeth have been removed and bone
loss has occurred. The implants can often be placed at the time the
grafting is performed.
Block Bone Grafting
In severe cases the ridge has been reabsorbed and a bone graft is
placed to increase the ridge height and/or width. In these situations,
the graft is taken from another area inside your mouth or body. This
dental implant bone grafting technique is where a block of bone is cut
out of one area and screwed into the area where the dental implants
will be placed. Normally, the block bone graft is placed and allowed to
integrate into the jaw bone for four to six months before the dental
implant is placed.
This office procedure is usually performed using general anesthesia and takes about an hour.
These procedures may be performed separately or together, depending
upon the individual's condition. There are several areas of the body
which are suitable for attaining bone grafts. In the maxillofacial
region, bone grafts can be taken from inside the mouth, in the area of
the chin or third molar region or in the upper jaw behind the last
tooth. In more extensive situations, a greater quantity of bone can be
attained from the hip or the outer aspect of the tibia at the knee.
These surgeries are performed in the out-office surgical suite
under IV sedation or general anesthesia. After discharge, bed rest is
recommended for one day and limited physical activity for one week.
Bone Expansion
Many people, including some doctors, incorrectly believe that bone is
hard and unbendable. Perhaps this false idea comes from studying dried
skeletons. However, living bone is much softer than dried bone. Living
bone can be stretched open in certain areas of the jaw. This stretching
is called bone expansion.
Bone Expansion Rationale
After an area of bone has had bone expansion, the bone area is much
larger than it was before the bone expansion. The bone expansion allows
for larger dental implants to be inserted into the bone. Larger
implants have a greater surface area to bond to the bone and so have a
better long term prognosis. The primary purpose of bone expansion is to
allow a larger dental implant to be placed into the recipient area
where the bone expansion was successfully performed.
Bone expansion is most often performed in the front of the upper
jaw to assist with replacing incisors. However, bone expansion can be
done in selected areas anywhere in the mouth.
Bone Expansion Procedure
A small hole is first drilled though the center of the area of the
bone to be expanded. Then a series of bone expansion tools are tapped
into the hole. As the bone expansion tools get progressively larger,
the hole in the bone gets progressively larger and the walls expand.
The hole created by the bone expansion can then be filled with bone or
an implant can be immediately inserted into the hole. Bone expansion
expands or widens the walls of the bone.
Nerve- repositioning
The inferior alveolar nerve, which gives feeling to the lower lip
and chin, may need to be moved in order to make room for placement of
dental implants to the lower jaw.
Immediate Dental Implant placement
In some cases it is possible to actually extract the tooth and
place the dental implant at the same time. This is called immediate
implantation.
Guided Tissue Regeneration
Soft tissue, such as gum tissue, grows very fast while bone grows very
slow. When a surgical hole is created by a surgeon, soft tissue grows
into the surgical hole very quickly and blocks out bone from growing
into the hole. When bone is needed in an area to place dental implants,
uncontrolled gum tissue growth is a problem. A membrane barrier can be
used to cover the surgical hole and block out the gum tissue from
growing into the area. This allows the more slowly growing bone to fill
the surgical hole without any competition.
The membrane barrier guides the gum tissue away from the surgical
defect. Gums and bone are both tissues and both are guided by the
artful placement of a membrane barrier. Because the bone regenerates in
the surgical hole, the technique is called guided tissue regeneration.
Some surgeons call it guided bone regeneration because implant surgeons
are very concerned about the supporting bone around their dental
implants.
Guided tissue regeneration can be used to repair defects around
previously placed dental implants or to create additional bone in
deficient areas before placing dental implants. The surgical hole can
be filled with several different types of materials before covering the
area with a protective membrane barrier.
When there is adequate bone height and width and when the density
of the bone is acceptable, implant placement and ensuing success is
almost a foregone conclusion. However, many of our patients are
deficient in bone and in order for the implant placement to be
successful, we have to select a means of regenerating this missing
bone. While this is not necessarily an easy task, it does have a high
degree of success when carried out with skill and knowledge.
GRAFT MATERIALS:
Autogenous Bone
- Generally considered the best material for bone grafting. In many
implant procedures, bone for this purpose can be secured from adjacent
sites, the chin, the tuberosity and occasionally from the hip or other
areas of the body.
Allografts - They are derived from genetically unrelated
members of the same species. This is generally Cadaver bone which has
been specifically prepared for this purpose, Freeze dried cortical bone
is in this category.
Xenografts - Bone derived from other species such as cows.
Bio-Oss (Osteohealth - Shirley, NY) is a popular one at this time.
These materials generally work via either Osteoconduction, the
formation of new bone from host cells along a framework of a compatible
alloplast, or biological material, or Osteoinduction, the formation of
new bone from the biomechanically differentiation of the host
mesenchymal cells. Bone Morphogenic Protein (BMP) is the material that
will stimulate osteoinduction and the research that is currently
ongoing gives us great hope of being able to use BMP to predictably and
very rapidly induce the growth of bone just about anywhere we want it.
Barrier Membranes - In addition to the grafting materials
and BMP, membranes are very often used to guide the generation of new
bone. When there is a defect in bone, there is a competition between
the bone cells and the epithelial and connective tissue cells to fill
up the defect. If left alone, bone usually looses. The membrane allows
the bone to win by blocking out the epithelial cells and the connective
tissue cells from the site.
Additional Information About Bone Grafting
Click Here for information about Resorption of the Jaw
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