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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.
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.
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.
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.
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.
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.
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).
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.
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.
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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