For dental implants to be successful, the jawbone must have enough bone
to support them. You may not have enough bone because of tooth loss from
periodontal (gum) disease, injury or trauma, or a developmental defect.
If your jaw is too short (up and down), too narrow (side to side), or
both, you will need a procedure to add bone to your jaw before implants
can be placed.
Bone
augmentation is a term that is used to describe a variety of procedures
that are used to "build" bone so that dental implants can be placed.
These procedures typically involve grafting (adding) bone or bonelike
materials to the jaw, and waiting for the grafted material to fuse with
the existing bone over several months.
There are
several different procedures that can be used for bone augmentation.
Your dentist will select a procedure depending on the type, location and
number of implants to be used. If
you need a bone graft, it is important that you and your dentist discuss
all of the options available to you.
After a
bone-augmentation procedure, dentists usually wait 6 to 12 months before
placing implants, although some dentists may place them sooner.
Most
bone-augmentation procedures involve the use of bone grafts. The best
material for a bone graft is your own bone, which most likely will come
from your chin or ramus (the back part of your lower jaw). If your
oral surgeon cannot get enough bone from these areas, he or she may need to
get bone from your hip or shin bone (tibia) instead. The hip is
considered to be a better source because the hip bone has a lot of
marrow (soft tissue within the bone), which contains bone-forming cells.
If you
don't like the idea of having bone removed from your body to be placed
in your jaw, there are other options available to you. Your dentist can
use materials made from the bone of human cadavers or cows. There are
also synthetic materials that can be used for bone grafting. While most
dentists prefer using a person's own bone, possibly in combination with
other materials, the choice is yours. You should discuss your options
and their risks and benefits with your dentist before any procedures are
done.
In a
typical situation, a patient has lost a single tooth and wants to have
it replaced with a crown supported by a dental implant. However, the
tooth has been missing for several years and there is not enough bone to
support the implant. In this case, bone taken from the patient's chin
can be used to "rebuild" the lost bone so that it can support an
implant. This type of procedure would be done in a dentist's office.
Local
anesthesia will be used to numb the area where the bone augmentation is
needed (recipient site) as well as the area from where bone will be
removed (donor site). The DSI specialist first will make an incision
(cut) in the gum where the implant will be placed to determine how much
and what type of bone is needed.
He or she
then will make an incision in the gum below the lower front teeth to
expose the chin bone. A block of bone will be removed from the chin
along with any bone marrow. The specialist will fill the spot where the
bone was removed with another type of bone-graft material, and will
cover this with a membrane (thin film of tissue) to keep soft tissue
from filling the space as it heals. The incision then will be stitched
closed.
To place
the removed bone in the recipient site, the DSI specialist first will
drill little holes in the existing bone to cause bleeding. This is done
because blood provides cells that help the bone heal. The block of bone
that was removed from the chin will be anchored in place with titanium
screws. A mixture of the patient's bone marrow and some other bone-graft
material will then be placed around the edges of bone block. Finally,
the DSI specialist will place a membrane over the area and will stitch
the incision closed.
After a
bone-augmentation procedure, you will be given antibiotics, pain
medication and an antibacterial mouthwash. You will be asked to avoid
certain foods, and will be told how to avoid putting pressure on the
area while it heals. If you wear a denture, you may not be able to wear
it for a month or longer while the area heals. If you have natural teeth
near the bone graft, your dentist may make a temporary removable bridge
or denture to help protect the area.
The bone
graft will take about 6 to 12 months to heal before dental implants can
be placed. At that time, the titanium screws used to anchor the bone
block in place will be removed before the implant is placed.
Many people
are missing several teeth and need several implants. If bone needs to be
built up to support several implants, a lot more bone-graft material
will be needed than if a single implant is being placed. If you are
having several implants placed and choose to use your own bone for a
bone-graft procedure, the bone probably will have to be taken from your
hip, shin or another site. This type of procedure is done in the
hospital under general anesthesia, and requires an overnight stay.
The success
rate for bone grafts in the jaws for the purpose of placing dental
implants is very high. However, there is always a chance that the bone
graft will fail, even if your own bone was used. Bone grafts are not
rejected like organ transplants. When they fail, it is usually because
of an infection or because the grafted bone wasn't stabilized and has
come loose from your jaw. Dentists don't know why some bone grafts fail,
but they do know that certain people — such as those who smoke and those
with certain medical conditions — have a higher risk of graft failure
than others.
A failed
graft will be removed. Once the area has healed, your dentist can place
a second graft.
In addition
to bone grafting, many other types of procedures can be used to build
bone so that implants can be placed.
One type of
bone-augmentation procedure, called a sinus lift (or elevation),
increases the height of your upper jaw by filling part of your maxillary
sinus (the area above your jaw on either side of your nose) with bone.
This is done when there is not enough bone to allow implants to be
placed in the back part of the upper jaw.
A ridge
expansion is a type of bone graft that can be done when the jaw is not
wide enough to support implants. Your
oral surgeon uses a special saw to
split the top of the jaw ridge, and then packs graft material into the
newly created space. Some dentists will place implants directly after
this procedure. Others will wait several months for the ridge to heal.
This procedure can be done in the dental office under local anesthesia.
One of the
newest procedures for augmenting areas of bone is called distraction
osteogenesis. This procedure originally was used for lengthening the
bones of patients with abnormally short legs. It now has been adapted
for use in the mouth. A surgeon makes cuts in your jawbone to separate a
piece of bone from the rest of the jaw. A titanium device inserted into
the jaw with pins or screws holds the piece of bone apart from the rest
of the jawbone. Over time, the space between the piece of bone and the
jawbone is widened slightly by unscrewing the device, and the area
between the pieces gradually fills in with bone. "Distraction" refers to
the process of separating the two pieces of bone, and "osteogenesis"
refers to the forming of new bone. Distraction osteogenesis is used more
often to make the jawbone taller, but it can be used to increase the
bone in any direction. The procedure is becoming more common.
A nerve
called the inferior alveolar nerve runs through the lower jaw. This
nerve gives feeling to the lower lip and chin. In patients who have lost
significant amounts of lower jawbone, it may not be possible to place
implants without damaging this nerve. To address this problem, an oral
surgeon can drill a small window in the bone and move the nerve to one
side. The implants then can be placed through the bony canal previously
filled by the nerve. This technique is not used very often because it is
possible to damage the nerve just by moving it.