Dental Implants

It seems obvious to many people that if you lose a tooth from extraction, or if it should happen to be knocked out, then the answer is simply to “screw” one back in. Of course this might be the ideal but the idea doesn’t take into consideration all the biological factors associated with an artificial implant. First of all, bone is not dense like wood and can’t simply be drilled and raw-plugged. It is generally trabecular and spongy in texture rather than solid inside, as in the mandible or maxilla.

Secondly there is the problem of rejection of any foreign material unless it is inert or bio-compatible in nature. Then there is the fact that natural teeth are “suspended” within their bony sockets by a thin periodontal membrane of fibres which acts as a kind of shock absorber. The first two problems have been overcome but not the latter, which may explain why an implant may look exactly like a natural tooth but never feels quite the same, much like a false limb, one would imagine.

The problem of fixing the implant into bone is overcome by inserting a bio-compatible metal anchor first into the appropriate position in the jawbone, and then allowing it sufficient time for healing to take place, and for bone to grow in and around the implant which fixes it firmly.

This process of osseointegration usually takes a couple of months or so and only then is the gum opened again surgically and a strong post inserted to screw in or fit to the base, and that post carries the artificial tooth. There may be an exception to this scenario with some types of “immediate loading” implants, but in general the whole process takes a few months, so that some kind of temporary denture or adhesive bridge may be necessary in the meantime.

The great advantage of an implant is that, once it is in place it is   as near to a natural tooth as you can get, and avoids the need for a removable bridge or denture, or for a fixed bridge which, although a viable alternative, normally requires some considerable reshaping and reduction of other teeth first. For years man has endeavoured to find a more natural replacement for missing teeth, and modern, space age materials and techniques have enabled that desire to become a reality. The dental implant is truly the most natural solution to the problem of one or more missing teeth and is amazingly successful.

The implant anchor behaves as a solid, immobile platform on which can be placed the post and artificial tooth. An implant functions just like a natural tooth allowing you the freedom to eat most normal foods although you should be careful of excessively hard bones or undetected olive stones in pizzas, for example.

An implant does not require any visible retention clasps like a denture or the interference or destruction of sound tooth tissue. It doesn’t rest on the gums like a denture but instead is embedded in the jaw bone and is firm enough to resist normal chewing forces. 

An implant is the ideal replacement for one front tooth that has been lost through decay or trauma whilst the rest of the teeth remain sound and intact, especially in the younger person.

Implants can replace more than one tooth provided there is enough depth of sound jaw bone for anchorage, and in a young person this is usually not a problem. If teeth are lost early in life, then the basal bone in which they were embedded begins to shrink and goes on gradually shrinking throughout life, a process termed resorption. This is the major reason why it is unwise to have your teeth out at a young age since by the time you reach 60 or so there may not be sufficient jaw bone left to take implants or even sometimes a satisfactory denture. It is essential to keep all your teeth for life if you possibly can.

In cases where there is insufficient bone for an implant it is often possible to graft in more bone from another place such as the chin or hip to make up the deficit. Sometimes, a combination of your own bone tissue and a synthetic substitute may be used.

There is no age limit for dental implants, with the criteria for their placement being more concerned with adequate bone depth and width for anchorage. They are not considered viable for children, however because the jaw is continually growing and developing until skeletal maturity is reached.

The provision of dental implants is a tried and tested technique and the implants generally last for many years, although in some cases of excessive loading they may work loose and can even become infected in a mouth where oral hygiene is lax.

The cost of implants is quite high, reflecting the level of expertise required in providing them, plus the cost of the implant materials themselves. It is wise for a patient to have a full and comprehensive consultation with their dentist before undergoing implant procedures so that they know exactly what to expect at each stage of the procedure and what aftercare is provided.

Replacement of a single tooth with an implant costs about the same as for dental bridge, but the advantage is that an implant does not require the cutting down of adjacent teeth. More complex treatment involving preliminary bone grafting will add to the cost, but still most patients are more than happy with the investment. Once the implant is completed it becomes virtually part of you and is as strong as a natural tooth in most instances, and can be expected to give many years of service provided you maintain a good level of oral hygiene.

A missing tooth at the front of the mouth is very unsightly to most people, especially in a young person since it is so unexpected and incongruous. Fortunately these days the situation is much less commonly caused by dental decay but can still occur on occasion from a traumatic accident leading to the loss of the tooth, either by avulsion at the time of the trauma, or shortly after, due to extraction if it was badly fractured and difficult to save. If only the crown of the tooth is lost but the root remains intact, then there is the possibility of root-treatment followed by the provision of a post-crown, but if the root is fractured then the prognosis must be considered poor.

Traditionally the way to replace such a missing tooth has been the provision of a denture or plate, and often this may still be necessary as an interim measure, but there are other options for a definitive tooth replacement, such as a bridge, or an implant.

A fixed bridge is generally constructed in a dental laboratory and consists, (when replacing just the one tooth), of three complete jacket crowns fused together so that when fitted in the mouth the crowns fit exactly over the teeth either side of the gap, whilst the artificial tooth replacing the missing tooth, is suspended in between. These teeth are called the abutments and are reduced in size and shaped in order to allow for the crowns to fit over. Once the bridge is fitted the artificial tooth is suspended between the teeth either side of the gap but appears to be growing from the gum just like a natural tooth.

As good as a bridge can be it does entail considerable loss of sound tooth structure in the preparation of the abutment teeth, and so if an even better alternative such as an implant is possible then this must be the first choice.

A fixed bridge needs to be adequately strong, so often it is made from porcelain fused to precious metal alloy, but in some circumstances where loading is relatively light it may be possible to make the bridge completely of porcelain which gives the best aesthetic result with no risk of a dark line at the margins from the shadow of the metal.

The dental implant is another way to fill the gap left by a lost tooth and is even more amazing than a bridge in that it closely resembles a complete natural tooth by being embedded into the actual jaw bone. The actual artificial tooth is made out of porcelain like a crown, or porcelain fused to metal, but fitted on the top of a metal post instead of on to a cut-down natural tooth. The metal post fits into an anchoring device previously inserted into the jaw bone by precise drilling and placement, and is often in the form of a hollow, perforated metal tube that has become fixed and stabilised by the growth of natural bone around it and into the perforations thus fusing it in place. The sub-structure usually requires a few months to stabilise, but may in certain cases accept the post and crown almost straightaway. 

There is no doubt that the dental implant is the best way to replace a missing front tooth due to a traumatic accident when the other natural teeth are all intact and sound since it is totally independent of them and doesn’t require any interference with them. All the materials used for implants are bio-compatible so that the risk of rejection and loosening is minimised.

Individual implants can be placed as required in the dental arch provided there is sufficient depth of jaw bone to accept them without danger to any important anatomical features such as nerves. If there is inadequate depth or width of bone it can sometimes be augmented by grafting from a suitable site such as the hip or the chin.

In cases where quite a few teeth are missing it may be possible to provide several fixed anchors at strategic points and then construct a removable bridge that slots over them. This produces a more stable and retentive result often than the standard removable bridge or denture constructed around the remaining standing teeth.

Because of the elapsed time necessary for osseointegration of the implant anchor it is usually necessary to provide some sort of temporary restoration and this is most easily achieved by means of a simple denture although sometimes an adhesive temporary bridge may be possible. Sometimes, however, in the younger person where there is plenty of sound jaw bone depth it may be possible to place an immediate loading implant which avoids the delay and the need for a temporary replacement tooth. The implant must be judged to be strong enough to withstand biting forces once the post and crown are attached.

The simplest type of implant is a root form screw type which is much like the normal root of a natural tooth, and is the type usually employed where there has been loss of a single tooth at the front of the mouth. Titanium is the material generally used for construction of an implant since it is light and strong, but most importantly, is inert and bio-compatible.

Implants generally last for many years if not a lifetime, but can occasionally give problems if they work loose or become infected. Such eventualities are rare however, and can usually be treated if they should occur.

Resorption continues on throughout life in an edentulous jaw at a fairly steady rate, so the amount of resorption seen in any particular case is often age related. Someone who has all their teeth removed at age twenty can expect about a 50% reduction in alveolar ridge height by age forty.

Bone grafting is a remarkable technique which can allow procedures to be carried out that otherwise would have to be ruled out because of age-related bony shrinkage or resorption. The resorption and shrinkage of the jaw bone is now known to be an inevitable consequence of having one or more teeth extracted, since once the tooth is gone there is no stimulus to encourage bone to remain and it basically resorbs from lack of use. A fair amount of resorption takes place very quickly after a tooth is extracted as part of the healing of the socket followed by the rounding off of the sharp edges of bone around the socket.

Bone Grafts and Implants

Sometimes, when resorption has excessively reduced the amount of alveolar bone in the jaws it can be difficult for a person to satisfactorily wear dentures or to have a viable implant because of lack of depth or width of supporting bone. Fortunately, however, modern bone grafting techniques can often overcome these problems, rebuilding, augmenting, or filling in jawbone defects.

In general there are four main types of bone grafts used:

Modern bone grafting techniques can be nothing short of a miracle for those lacking sufficient of their own bone in strategic places as can be necessary for successful dental implant treatment. Most implant clinics are therefore able to offer this procedure as part of an overall implant package, but it is worth checking out precisely the nature of the graft to be provided in any particular case and all the concomitant relevant information.

1. Autografts are those where the bone to be grafted to the jaw is taken, or harvested, from another part of your own body. This is also termed an autologous graft meaning the donor and graft recipient are one and the same, and gives the highest success rate since there is little risk of rejection because the donor material is compatible in every respect. The donor site is most commonly the chin or hip area where the bone is harvested from.

2. Allografts are taken from human donors, typically from a dead, frozen bone, and also have a good rate of success when used in a healthy recipient. Many countries have a donor program that allows for harvesting of body parts or tissues after death for the benefit of others, and bone grafts from these sources are rigorously screened and sterilised before use. Provided the bone is, like blood, from a compatible donor then it is incorporated quite well into a new site, although it may take longer than an autograft. An advantage, however, is that there is no need for a second surgical site in the patient since the graft is coming from a donor. Fortunately, tissue transplants are not normally rejected by the body like organ transplants so there is no need for immuno-suppressant drugs.

3. Xenografts are harvested from animal sources, most often from the cow, and the bovine bone is specially treated to sterilise it and make it bio-compatible. It can act as an infill which is gradually replaced by the patient’s own natural bone. Thus a period of time is required for this to take place before dental implants can be inserted.

4. Alloplastic grafts are inert, man-made synthetic materials which are suitable to mix with bone and encourage further bone formation. This is usually a form of calcium phosphate which may be designed to resorb in time or be permanently incorporated into natural bone. Such grafts can sometimes be used together with autografts.