 
Dental implants
Dental implants have been used to replace missing teeth since the mid-1960s,
but in recent years their use has become much more widespread. They can be used
to support crowns replacing single missing teeth, bridges that restore a larger span of missing teeth, or even dentures.
Implants are manufactured from titanium, a metal that is known to be compatible
with body tissues and able to bond with adjacent bone during healing. There is
a now a wealth of evidence from studies and from clinical experience to show that
dental implants are a safe and convenient way to replace lost teeth with natural-looking
results.
Why have dental implants?
Dental implants have a number of important advantages over conventional crowns,
bridges and dentures:
- Implants look and feel like natural teeth.
- Implants function in the same way as natural teeth and there are no difficulties
with eating or cleaning the teeth.
- Healthy adjacent teeth do not have to be filed down to act as supports for
the missing tooth or teeth. This means that they are therefore less likely to
need root fillings.
- The presence of the implant maintains the structure of the bone beneath the
replaced tooth, as chewing forces are transmitted through the implant to the bone
and stimulate the natural process of bone renewal. This helps preserve a good
appearance, both of the restored teeth and of the face.
- Dental implants can be used to give removable dentures a firm grip.
- With dental implants, there is no need to use special glues to hold the false
teeth in place, as there is with some dentures.
What does a dental implant consist of?
A dental implant is essentially a titanium screw or cylinder, between 8 and
16 mm long, which is inserted into a prepared bony socket in the jaw and acts
as a replacement root for the missing tooth. A special attachment called the abutment,
which is fitted to the top of the implant, forms the external connection for the
new replacement tooth (crown) or teeth (bridge or denture).
During healing, the titanium surface of the implant fuses with the surrounding
bone, in a process known as osseointegration, which can take
about 3-6 months. After this time, the implant is stable enough to support one
or more false teeth.
Who can have an implant?
Dental implants are suitable for almost anyone who has lost one or more teeth
and would like to restore their appearance or chewing ability; however, as it
is important that the patient’s bone tissue is fully developed, they are not used
in young people younger than 18 years of age.
To be considered for implants, your mouth must be in a healthy condition, with
no untreated tooth decay or active periodontal (gum) disease. If implants are
fitted in the presence of active periodontitis, there is a danger that an infection
will develop around the implant, which will lead to its failure and loss. Your
dentist will need to be sure that your oral hygiene is of a high standard before
treatment is offered, because the long-term success of implants depends on good
plaque control. After treatment is completed, you need to be willing to attend
regular follow-up appointments with your dentist or periodontist, so that he or
she can assess the implants and take steps to prevent any complications at an
early stage.
If you meet all the criteria for implants above, your periodontist will be
happy to discuss the various treatment options that are available, which will
depend on many factors individual to you, such as your general health, the number
and position of missing teeth, and the quantity and quality of your bone tissue.
When is an implant not a suitable treatment?
Implant therapy may not be possible if the jaw bone is not sufficiently thick
to accommodate implants and bone grafting is not possible. Also, implants are
not suitable for patients with untreated periodontitis or uncontrolled diabetes,
because of the risk of failure through infection or poor healing.
Other medical conditions that rule out the use of implants include blood clotting
disorders; certain bone diseases, deficiencies in the immune system, severe systemic
illnesses and drug abuse. Smoking is also an important consideration, because
smokers heal less efficiently than non-smokers and are more likely to experience
loosening of their implants. Quitting smoking will significantly increase your
chances of successful implant therapy.
What does implant treatment involve?
- Examination
After discussing the potential courses of treatment open to you, your dentist
or periodontist will conduct a thorough examination of your mouth. He/she will
then take radiographs of your jaws to assess the shape and condition of your bone
tissue and locate the positions of any important structures, such as nerves and
sinuses, which may be close to the intended implant site. This allows the dentist
to plan exactly how the implants will be placed. Rarely, if X-rays are not adequate,
a computed tomography (CT) scan may be used to provide three-dimensional images,
but this is an expensive procedure and exposes you to more radiation than standard
radiographs.
- Insertion of the implant/s
Implant surgery can be carried out using either a one-stage or two-stage procedure,
depending on your particular clinical circumstances. In either case, the surgery
involves making a small incision in the gum to expose the bone and using a special
drill to shape the implant site.
In the one-stage procedure, the implant is fitted into the prepared bone and then
an attachment called a healing cap, which protrudes through the gum, is placed
over it. This healing cap is removed after a 3-6 month period and replaced with
a permanent attachment called the abutment, which takes the form of a post and
core. The replacement tooth, or crown, is cemented in place over the abutment.
In the two-stage procedure, a cover screw is placed flush over the top of the
implant and the gum is sewn up over it for the period of healing. A second procedure
is needed to uncover the implant via a small incision in the gum and attach the
healing cap. Then, after the gums have healed, the healing cap is removed and
replaced by the abutment, in readiness for the new crown.
Two-stage surgery may be necessary if there is a need to increase the quantity
of bone at the site with a bone graft or a bone regenerative
technique. There are a number of reasons why there might be a lack of
bone at the implant site, including long-term missing teeth, denture wear, and
bone loss from periodontal disease, ageing or injury. When teeth are missing,
the surrounding gum and underlying bone shrink away over time. This is because,
in health, the presence of our teeth stimulates the natural turnover, or renewal
process, within the bone.
- Preparation of teeth and impression
When your gums have fully healed (after about 6 weeks), your dentist will take
a new impression of your mouth. This will be used to make a model of your teeth
on which the dental technician will construct your crown or bridge, paying special
attention to achieve a natural finish that matches the rest of your teeth.
- Fitting of crowns or bridges
When your new crowns and bridges have been prepared, your dentist will cement
them on to the abutments over the dental implants, assess the appearance and fit,
and check that your upper and lower teeth work together comfortably when you bite.
You will usually need to return for several review appointments to make sure that
the implants are stable and functioning well, and that you are completely happy
with the finished result.
What is bone grafting and bone regeneration?
Bone grafts
Bone grafts are carried out to increase the width and height of the jawbone at
the implant site. The best results are seen when bone from another part of your
own body is used and this is known as autogenous grafting. Typically,
bone is harvested from the hip, as it is a good source of marrow which contains
many bone cells. Allografts are grafts that use donated human
bone taken from a ‘bone bank’ and work in the same way as autogenous grafts. Xenografts
are procedures that use bone from an animal donor, with cows acting as the main
source (bovine bone). The bovine bone in the graft is replaced by your own bone
tissue over time. Alloplasts are grafts that use synthetic bone
substitutes that are chemically similar to human bone. These grafts act as a sort
of framework for new natural bone formation and may be replaced by natural bone
(resorbable alloplast) or retained (non-resorbable alloplast).
An autogenous graft is the preferred option because there is no risk of your
body rejecting it. After the procedure, you will need to wait for at least 3 months
before having implants placed, so that healing can take place. The exact waiting
time will depend how much bone has been grafted.
Bone regeneration using barrier membranes (guided tissue regeneration)
This is a special technique that helps to give bone cells an advantage over
other types of cell to multiply and fill an area where bone loss has occurred.
Usually, cells from the gum surface and the connective tissues are much faster
at filling the gaps created by periodontal destruction compared with the bone
cells and so bone may not have an opportunity to regenerate even when inflammation
has been eliminated. In this procedure, the barrier membrane covers the area of
bone loss and blocks access to it for the other cell types, giving the bone cells
a chance to fill in the defect. The barrier may disintegrate and disappear over
time (resorbable) or may need to be removed in a later procedure (non-resorbable).
How long will my implant last?
Dental implants have been used successfully for many decades and we know that,
with careful maintenance, they will function for many years. In studies, 95% of
implants last for at least 5 years, but most are likely to have a much longer
life. To maximize the lifespan of your implant, you are strongly advised to avoid
smoking. It is also extremely important to continue with a very thorough oral
hygiene programme at home and to attend regular recall visits at your dentist
for careful inspection of your implant, teeth and gums. This will allow you to
have your implant and teeth professionally cleaned and enable any problems to
be dealt with promptly before they threaten the stability of your implant.
With very good oral hygiene, regular recall appointments and avoidance
of smoking, your dental implant has every chance of lasting for many years.
What might cause an implant to fail?
Assuming there have been no problems with the healing process after implant
placement, the most likely cause of failure is inadequate oral hygiene. If tooth
cleaning is poor, bacteria will build up on the implant surface and cause inflammation
of the mucous membrane surrounding the implant - mucositis. If
left untreated, this can progress to a more dangerous condition called peri-implantitis,
in which there is inflammation and bone loss around the implant. Eventually, the
implant loses its anchorage in the bone and becomes loose.
How are mucositis and peri-implantitis detected
and treated?
It is not easy for you to detect when mucositis or peri-implantitis is present.
Often, the only warning sign is an increased tendency for the gums to bleed during
brushing and interdental cleaning. Some bleeding is expected during the healing
phase after implant placement, but when bleeding occurs many months or years after
implant placement, it is a sure sign of inflammatory changes. Other changes that
you might notice are local swellings, bad breath or a bad taste, and loosening
of the implant, bridge or dentures.
Regular recall appointments with your dentist will help ensure that
any suspicious changes are picked up early so that peri-implantitis can be prevented.
It is vital that you make an appointment as soon as possible if you notice any
signs of inflammation around your implant between scheduled visits.
Treatment of mucositis and peri-implantitis involves professional cleaning
of the implant surface to remove bacterial deposits. In addition, you may be asked
to use an antibacterial mouthwash or gel or, in some cases, prescribed an antibiotic
to eliminate the infection. If the peri-implantitis is more advanced, your dentist
might consider a surgical procedure to gain better access for cleaning. However,
if the condition cannot be controlled, the implant may have to removed.
The earlier the detection of mucositis and peri-implantitis, the better
are the chances of successful treatment. |
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