|
|
|||||
|
Join our Blog feed
|
|||||
|
|||||
|
|
|||||
|
|
|||||
|
|
|||||
|
|
|||||
|
|
|||||
|
|
|||||
|
|
|||||
Types of Oral Implants
Over the past 20 years, Dental Implants have undergone remarkable changes. Many clinicians designed implants to fit certain needs and properties. Some of those designs had only a short application period, whereas others survived to this very day. Dental implants vary in several aspects, such as shape, place of anchorage (within the bone or on top of the bone), composition, coatings, etc. This page will shed a little light on the different types of implants that are in use today, categorize them and explain their most common application.
In general Oral Implants can be categorized into three main groups:
- Endosseous Implants
- Subperiosteal Implants
- Transosseous Implants
Endosseous Implants are implants that are surgically inserted into the jawbone.
Subperiosteal Implants are implants, which typically lie on top of the jawbone, but underneath your gum tissues. The important distinction is that they usually do not penetrate into the jawbone.
Transosseous Implants are implants, which are similar in definition to Endosseous implants in that they are surgically inserted into the jawbone. However, these implants actually penetrate the entire jaw so that they actually emerge opposite the entry site, usually at the bottom of the chin. This is also the site, where they are secured with a device similar to a nut and a pressure plate. It is very similar to a nut and bolt arrangement in ordinary wood carpentry.
Endosseous Implants are the most frequently used implants today. They could be further categorized into several sub-categories; based on their shape, function, surgical placement and surface treatment, however for our purposes we will only look at several families of these implants.
Below you will see several thumbnail pictures of implants belonging to certain categories and families. Click on any of these individual thumbnail images and you will be linked to the area describing that implant and its category or family:
Subperiosteal Implants Ramusframe Implants Blade Implants Rootform Implants Transosseous Implants
Subperiosteal Implants—
To the left you can see a typical Subperiosteal implant for the lower jaw. This particular implant has a whitish-gray Hydroxyapatite coating on its bone-contacting portion. We will discuss this coating in more detail in the Rootform Implant section below. Subperiosteal Implants were already introduced in the 1940s. Of all currently used devices, it is the type of implant that has had the longest period of clinical application. These implants are not anchored inside the bone, such as Endosseous Implants, but are instead shaped to ride on the residual bony ridge of either the upper or lower jaw. They are usually not considered to be osseointegrated implants. Subperiosteal Implants have been used in completely edentulous (toothless) as well as partially edentulous upper and lower jaws. However, the best results have been achieved in treatment of the edentulous lower jaw.
Indications:
Usually a severely resorbed, toothless lower jaw bone, which does not offer enough bone height to accommodate Rootform Implants as anchoring devices.
The leftmost picture shows an x-ray of a fairly resorbed lower jaw. The next image shows the same jaw with a Subperiosteal implant in place.
This implant is custom-made to each individual jaw. Nowadays, a CT Scan is taken of the jaw and a computerized modeling machine uses this data to reproduce a three-dimensional plastic model of the jaw to be treated.
This image shows a plastic model of a patient's lower jaw, which was modeled using data from a CT Scan. This model is accurate to the nearest millimeter.
This model (or a plaster copy there of) is then used to design the individual Subperiosteal framework on, which is then cast in metal. Sometimes a coating such as titanium or hydroxyapatite is applied to the areas that contact the bone, in order to improve its bio-acceptability. The implant is then sterilized and returned for surgical insertion.
After the implant has been surgically inserted, only a bar is visible extending from one side of the lower jaw to the other, onto which a denture can be clipped via an internal attachment mechanism. The denture can be made approximately two weeks after the surgery and is in general smaller than a conventional denture. This denture locks into the bar of the implant as shown below.
This is an image of what will be visible in the mouth on the lower jaw, once the implant is in place.
This is a picture of a denture that is specifically made for this type of implant. Notice that they are smaller than conventional dentures.
Above is a picture of the underside of that same denture. Notice the black attachment clips.
This is an image of that same denture inside the patient's mouth.
Ramusframe Implants—
This image represents the Ramusframe type implants. Its use will be discussed below. Ramusframe Implants belong in the category of endosseous implants, although their appearance might not suggest that at first. These implants are designed for the toothless lower jaw only and are surgically inserted into the jaw bone in three different areas: the left and right back area of the jaw (the approximate area of the wisdom teeth), and the chin area in the front of the mouth. The part of the implant that is visible in the mouth after the implant is placed looks similar to that of the Subperiosteal Implant described above.
Indications:
Usually a severely resorbed, toothless lower jaw bone, which does not offer enough bone height to accommodate Rootform Implants as anchoring devices. These implants are usually indicated when the jaws are even resorbed to the point where Subperiosteal Implants will not suffice anymore.
Above you can see an x-ray of a severely resorbed mandible. The vertical dimension in the mid-jaw (1st molar) area is less than 1/4 of an inch.
This is the same lower jaw with the implant in place. The outlines represent the part of the implant which is embedded in bone. The white mass you see added in is synthetic bonegraft, used to augment the ridges.An additional advantage that comes with this type of implant is a tripodial stabilization of the lower jaw. A jaw as thin as the one shown above can easily fracture at its thinnest part. The Ramusframe Implant, once integrated (after a three month waiting period) will also stabilize and protect the jaw somewhat from fracturing.
The Ramusframe Implant usually comes in a standard pre-shaped form and needs to be custom-fitted to the patient’s individual jaw dimension, as shown below:
Above is a picture of a pre-shaped Ramusframe implant.
This is the same implant custom-fitted.Once surgically inserted, a bar, running from one side of the jaw to the other is visible in the mouth. A denture similar to the one shown for the Subperiosteal Implant above, can then be attached to the bar.
Here you can see an image of a Ramusframe Implant in the patient's mouth immediately after surgery. Notice the similarity to the Subperiosteal Implant.
Blade Implants—
Above is a picture of a blade implant specifically designed for the back-most portion of the lower jaw. This implant offers great anchorage in that particular area.
The image above shows a custom-made blade implant specifically designed for the upper jaw.
In contrast, this implant was specifically and custom-designed for the lower jaw of a patient. Notice the difference in shape to the upper-jaw implant. These two implants also feature a Hydroxyapatite coating.Each of the three implants in that row belongs to the family of Blade Implants. However, since these are also surgically placed into the bone we categorize them also into the Endosseous Implant category. Blade Implants have a long track record, much longer then the Rootform Implants. Their name is derived from their flat, blade-like (or plate-like) portion, which is the part that gets embedded into the bone.
Indications:
Blade implants are not used too frequently any more, however they do find an application in areas where the residual bone ridge of the jaw is either too thin (due to resorption) to place conventional Rootform Implants or certain vital anatomical structures prevent conventional implants from being placed. Nowadays, if a certain area of the jaw bone is too thin and has undergone resorption due to tooth loss it is recommended to undergo a Bonegrafting procedure, which re-establishes the lost bone, so that conventional Rootform Implants can be placed.
Here you can see an x-ray of a blade implant in place. An important anatomical structure (mandibular nerve and vessel canal) is outlines in black underneath. Notice how the implant was placed to avoid injury to this structure.
Rootform Implants—
Since the introduction of the Osseointegration concept and the Titanium Screw by Dr. Branemark (see History of Dental Implants), these implants have become the most popular implants in the world today. Rootform Implants are also categorized as endosseous implants. These implants come in a variety of shapes, sizes, and materials and are being offered by many different companies worldwide. Some clinicians regard them to be the Standard of Care in Oral Implantology.
Indications:
These implants can be placed wherever a tooth or several teeth are missing, when enough bone is available to accommodate them. However, even if the bone volume is not sufficient to place Rootform Implants, Bonegrafting procedures within reasonable limits should be initiated, in order to benefit from these implants.
This family of implants has undergone a tremendous development. They were tested and offered in different material compositions, since isolated studies have shown that materials other than titanium may integrate into living bone. Such materials included Aluminum Oxide, Vitallium, Commercially Pure (CP) Titanium, Titanium Alloys, even Sapphire. Today, the most accepted material for dental implants is high grade Titanium—either CP Titanium or an alloy thereof. The titanium alloy implants tend to be stronger than the CP titanium implants. The bone integration shows no difference to the two different types of titanium.
Further research eventually introduced titanium implants with different surface treatments. Some implants have an outer coating of Hydroxyapatite (HA). HA-coated implants have been shown to initially integrate somewhat faster, however after a year, the amount of bone contacting the implant surface is roughly the same as measured for the titanium-surface implants. Other implants have their surface altered through plasma spraying, aderchims or beading process. This was developed to increase the surface area of the titanium implant and, thus, in theory, give them more stability. These surface treatments were also offered as an alternative to the HA coatings, which on some implants have shown to break loose or even dissolve after a few years.
Other variations dwell on the shape of the Rootform implant. Some are screw-shaped, others are cylindrical, or even cone-shaped or any combination thereof. Each implant design has its specific reason or purpose and your doctor will make the right choice for you, based on your individual needs.
Below are images and descriptions of several different types of Rootform Implants.
This is an example of a commercially pure solid titanium screw implant. The screw shape usually offers better primary stabilization in bone of less than ideal density. There are no surface alterations on this implant, hence its shiny appearance.
To the right you can see an example of another screw-type implant. In contrast to the one above, however, here the surface alteration becomes apparent. This rough surface is referred to as a Plasma Sprayed Surface. It offers an increase in surface area over the smooth surface and, thus also more retention in the bone. Some research has also shown that initial integration into the host bone is somewhat accelerated through that.
To the left is an image of a Titanium Screw Implant with a Hydroxylapatite (HA) coating (notice the white-gray, rough surface). Beyond an increase in surface area as compared to smooth surface implants, this surface has also shown to have an accelerated initial integration, which makes it ideal for quick initial post-surgical stabilization in weak bone. There is a large range in the quality of coatings offered. HA coatings from some implant manufacturers have shown to dissolve or break loose after a while. The surgeon has to be very careful in the selection of a proper quality coating on an implant.
To the right is an image of a cylindrical-type implant. Notice the absence of the threads. There are, however anti-rotational features, such as grooves and holes, which prevent rotation during the healing process. This particular implant also has an HA coating. Cylinder Implants usually require good primary stabilization at the time of surgery.
To the left are two images showing two different types of tapered, cylindrical implants. One looks like a Christmas tree with fins projecting out to the sides; the other shows a special surface treatment consisting of spherical titanium beads. Each of these implants was designed to fulfill a specific purpose. As research in this field continues, we are assured to see many more shapes, forms, materials and coatings emerge, each trying to improve upon the last designs.
Transosseous Implants—
To the left you can see a typical Transosseous Implant. The plate on the bottom is firmly pressed against the bottom part of the chin bone, whereas the long screw posts go through the chin bone, all the way to the top of the jaw ridge inside the mouth. The two attachments that will eventually protrude through the gums can be used to attach an overdenture-type prosthesis. Indications:
These implants are not in use that much any more, because they necessitate an extraoral surgical approach to their placement, which again translates into general anesthesia, hospitalization and higher cost, but not necessarily higher benefits to the patient. In any case, these implants are used in mandibles only and are secured at the lower border of the chin via bone plates. These were originally designed to have a secure implant system, even for very resorbed lower jaws.
The Transosseous Implants can also be categorized into the endosseous implant category. Most clinicians nowadays however, prefer to use one of the other mentioned implant modalities instead of the transosseous system.
|
|
