Issue 102 / November - December 2014
Imitation Teeth: Implants
Hasan Ali Gunes
Our teeth were designed in a harmonious and organized fashion, just like each and every particle of our body. It becomes unbearable when one tooth is missing, as this harmony is spoiled. Dentists are trying to compensate for such absences with artificial teeth called implants. This kind of application is nearly as old as human history. Most of the time, however, humanity was utterly inadequate in replicating real teeth, as many implants, shaped from wood or computer assisted technology, failed to match real teeth.
In the past, the area missing a tooth could be filled by bridge implants by eroding the enamel on neighboring teeth. In cases where there was a large gap or no teeth to use as connectors, removable implants were used. In other words, present healthy teeth would be treated to compensate for the missing teeth; if the number and health of the remaining teeth was not sufficient, removable implants would be produced that gave the "ready to fall out" feeling. The imperfections of this type of implant led scientists to pursue new ideas.
Scientists have tried to fill in missing teeth with artificial roots and with implants mounted over these by mimicking the existing tooth root. This way, there is no need to treat and erode the healthy enamel of neighboring teeth in the gap. These artificial roots, which are positioned into the jaw bone by a surgical operation, are called a "tooth implant." Modern-day implants are generally composed of two main parts.
One of these is the fixture part which is secured into the jaw bone by screws; the other is the support part (abutment) which mimics the visible parts of the tooth in the mouth. Approximately 3-4 months of curing time is required for the fusion of bone and implant (osseointegration), which is screwed together by a surgical operation. Towards the end of this time, the implant is built over the abutment. The length of time necessary for the implant to integrate with the bone to replace a tooth which can be extracted so quickly is rather noteworthy despite ongoing studies to reduce the wait time and successful attempts to do so.
Even though the main logic for implants is the mimicry of the tooth and the root, the materials utilized are quite variable. The history of such implants goes back thousands of years. The employment of bamboo sticks in tooth restorations could be seen in some civilizations, such as ancient China. Mayans used sea shells, which were recently shown to be biologically suitable as implant material. Maggiolo produced a tooth root by using gold, in 1809. In the beginning of the 20th century, Lambotte prepared implants using materials such as aluminum, silver, brass, copper, and gold.
These newer implant methods have failed because of the insufficient strength of the majority of the materials and the failure to fit into biological tissues. The initial employment of titanium and its alloys in the 1950's almost opened a new age in implantology and enabled the successful use of these materials up until today. However, these titanium implants, which are considered successful, have a very limited ability to mimic tooth roots:
- Once the implant is in place, for reasons such as aging and improper tooth brushing, tooth gum recession and resurfacing of the bright faces of the implants which mimic the root surface can take place. This leads to undesirable displays. Even though gum recession can also occur in natural teeth for similar reasons, this situation is not as disturbing as with implants. This is because the tooth root color is similar to that of the tooth surface.
- Under normal conditions, implants should be fused to integrate with the bone (osseointegration). Integrated implants are considered successful clinically. A similar case to this bondage, which is unwanted clinically, is the fusing of tooth and bone which can be seen generally in dead teeth and is called ankylosis. Many hardships can be encountered when the tooth that is fused with the jaw bone is required to be removed. The same thing also applies to the implant. If an implant is set to be extracted for a reason, even if just a small amount must be removed, the surrounding jaw bone must be removed as well. However, a natural tooth is not bonded so tightly to the jaw bone, as if the tooth is healthy, it is suspended over the jaw bone through small suspension-like structures. When a tooth is needed to be pulled as a result of trauma or tooth rotting, only these suspensions are detached; thus any damage to the jaw bone is averted. Present efforts to design similar mechanisms for implants have not been successful yet.
- When a disease develops in our natural teeth, we feel pain and take action before it is too late. However, diseases within implants are rarely encountered as pain; generally, when the pain is felt, the implant is already disconnected from the bone and it is lost. Toothache often felt as a strong pain is a blessing granted to us. If the implants were built with pain mechanisms, just like in our natural teeth, we could take action at the beginning of the disease and avoid the time and financial losses.
- Even a healthy tooth, which we think of as immobile, can move via microscopic ligaments for 0.1 mm around its root on a type of pad. The tooth root is created in a perfect fashion to resist the strong chewing power that can be generated from many directions in the mouth through these ligaments, which are wrapped around different sides and which come from different angles. However, these ligaments, which act as a suspension, do not exist in between the implant and jaw bone. Therefore, implants are almost immobile. Even though it may seem like a good thing for them to be immobile and tightly fixed, there may be intense power spots generated on the implant or jaw bone since these forces acting on the implants are transmitted to the jaw bone without being dispersed. Forces densely acting on small areas can lead to fractures of the material, including tiny screws or porcelain plating, and can damage the bone tissue. Investigators once understood that these tiny, suspension-like structures won't form around the implant, so they engaged in mounting tiny Teflon or spring pieces inside the implant to generate suspension. However, these imitated suspensions failed to resist the chewing forces that can go up to 400 kg at times, and their use was aborted after a short time.
- Teeth can be examined by the method of tapping with small hand tools (percussion). These small impacts cause pain in case of an abscess at the tooth root. By taking necessary actions, the tooth can survive longer. It is impossible to do such determination and diagnosis with implants.
As it is seen, making less successful artificial implants as opposed to real teeth is quite a cumbersome, costly, painful, and time consuming job. Despite all of these imperfections, because of their numerous advantages over traditional implants, the popularity of dental implants continues to increase, and is preferred by dentists and patients. In addition, implants are seen as an inevitable treatment option when tooth loss occurs, and may ultimately provide patient relief in the long run.
Despite progress made in implants, it's clear that our teeth were created in such a perfect way, down to the very smallest detail, that they cannot be replaced. Science is well aware of the fact that we will never fully be able to replicate tooth structure. Therefore, studies are shifting towards stem cell research. This way, instead of foreign substances, the missing tooth will be compensated as if by planting tooth seeds by using human's own cells. Nonetheless, the opportunities that are discovered via all these efforts will never replace the natural teeth that were so perfectly created for us.