Various Types of Dental Implants
The dental implant has been hailed as a miracle by some because it enables a person to have a missing tooth or several teeth replaced without having to wear some form of denture or have other teeth cut down in order to hold a bridge in place.
There are various different types of implants available, each designed for a specific application. Most implants are made of titanium which is an inert metal and which has been shown to be ideal in that when perforated or special treated over its surface, it allows bone to grow and fuse with it, a process termed “osseointegration”. Possible alternatives are stainless steel, vitallium, chromium cobalt molybdenum alloy, ceramic, or a carbon compound.
The cylindrical or screw type implant, called the “root form”, is similar in shape to the root of a natural tooth with a large surface area designed to promote good attachment to the bone. It is the most widely used type to replace a single tooth where there is adequate width and depth of jaw bone, and can be placed singly or in groups. Where there is insufficient width or depth of bone it may be possible to consider a bone graft or an alternative shape of implant, such as a “plate form”. Preliminary radiographs are taken, or sometimes even a CAT scan is performed to decide on precise location and design for the implants.
In cases of advanced bone loss, the “subperiosteal” implant may be provided in some cases, which is a thin metal skeleton framework that merely rests on top of the jaw bone but under the gums. The success of this type of implant could perhaps be less likely to be guaranteed long term.
The actual implant procedure involves the surgical placement of the implant or implants, followed by a healing period of osseointegration, and then the insertion of the implant post and restoration to replace the missing tooth or teeth. The treatment may sometimes involve cooperation between a surgical specialist who places the implant into the jaw bone and a restorative dentist who designs and provides the actual replacement tooth or teeth which are made from porcelain fused to gold alloy much like a crown or bridge. Some dentists undergo specific further training in providing implants and are able to offer the complete service themselves. Most implant procedures are performed in the dentist’s own practice under local anaesthesia, sometimes with additional intravenous sedation for the nervous patient. Hospitalization might be considered necessary in very complex cases or where there are underlying medical complications.
Root form implants are the closest in terms of size and shape to the root of a natural tooth and are the more usual type employed where there is plenty of bony support available in terms of both depth and width. The implant may be hollow or solid, straight-sided, tapered, or conical in shape, and be perforated, threaded, or specially coated with a porous titanium layer, or hydroxyapatite to encourage bonding with bone.
The surgical implantation of an implant is no worse than having a tooth extracted, although it’s a case of putting something in rather than taking a tooth out. After the local anaesthetic has taken effect the area of the jaw to be implanted is exposed with one or more incisions and reflection of the mucosa, and then a precise hole is drilled to accept the implant which is inserted into it. The soft tissues are replaced and sutured, and healing usually takes place within three to six months.
During this time osseointegration occurs by bone growing into and around the implant, setting it firmly in place, rather like a piece of wrecked ship might become enclosed in coral under the sea.
Once healing is deemed to be complete the area is uncovered again and the post or attachment is affixed to support the new artificial tooth or teeth.
Plate form or blade implants are usually used when the bone is so narrow it may not be adequate for the root form implant, and where there are problems with bone grafting. The plate form implant is flat and long so it can fit into the narrower jaw bone. The insertion method is similar to that for a root form implant but there may need to be slightly more bone removal. As with root form implants, there is usually a healing period for osseointegration to take place, although some plate form implants are designed for immediate restoration. In the edentulouslower jaw a type of frame design shaped like a horseshoe and called a Ramus Frame implant can be used to provide multiple anchorage points with the loading spread over a wider area than could be achieved with individual implants.
A transosteal implant is more complex, combining subperiosteal and endosteal elements, and involves penetration of both cortical plates, in effect locking them together. It is also called a mandibular staple implant or transmandibular implant.
Depending of the number and type of implants employed the whole process can take between two and six months to complete, or longer if bone grafting is needed. In most cases there is minimal post-operative discomfort.
Tolerance of dental implants is generally good in terms of the materials and patients have little problem with keeping them clean, so they should last for many years provided they are not overloaded.