The replacement of missing teeth has been one of the primary goals of Dentistry since ancient times. As anyone who wears a full lower denture can attest, the lack of solid teeth with which to chew considerably lowers one’s quality of life, both from a nutritional and a socio-psychological standpoint. Traditionally, however, replacement teeth could only be held in place relying upon support from adjacent teeth or by resting upon the gum tissue.
Due to the remarkable advances in our understanding of bone physiology and biomechanics, dental implants are now at the forefront of modern Dentistry. Dental Implantology solves some of the most vexing problems encountered in providing a solid dentition for chewing, with highly predictable and dramatic results.
Dental implants are used as support for the replacement of missing teeth. There are two basic types of dental implants: the superiosteal implant, and the root-form implant.
The subperiosteal implant is a custom made metal framework which lies directly over the lower jaw bone, but underneath the gum tissue. Usually four or five metal posts will protrude through the gum, which hold a full lower denture in place. Although still widely accepted, this technique has become far less common due primarily to advances in root-form implants.
A root-form implant is what most people commonly know as the Dental Implant. And as the name implies, it is analogous to the root of a tooth. It is usually a titanium cylinder which is placed directly into the jaw bone. A typical root-form implant has internal threads which allow a screw-type post to be threaded into the implant. This post, or abutment, protrudes through the gum tissue upon which the replacement tooth or teeth are anchored. An implant with its abutment component may be used to support a single replacement tooth; Or several implants may be used to support multiple teeth, including a full upper or lower arch of teeth. Root-form implants, in contrast to the subperiosteal, are directly integrated into the bone itself, which anchors them very solidly. They are highly predictable, and it has recently been reported that the success rate of dental implants has now surpassed the success rate of root canal treatment, at approximately 97%.
|Missing Tooth replaced with implant and crown|
There are two phases of treatment involved in the replacement of teeth using root-form implants: First, the placement of the implant itself, secondly, uncovering and loading of the implant.
Implant placement: Implant placement is a surgical procedure, often performed under local anesthesia. After careful examination and evaluation using x-rays and often a 3-D CT Scan, a small hole is made in the jaw bone which is the exact size of the implant to be used. The implant is then carefully threaded all of the way into the hole, until the top of the implant is flush with the bone. Next, a cap screw is fitted over the top of the implant to prevent ingress of gum tissue into the internal threads. The implant is then left alone usually for several months. During this time, osseointegration occurs. That is, the bone heals tightly around the implant.
Implant uncovering and loading: After the implant is deemed to be integrated (the time frame varies, usually depending on the location in the mouth and bone density), the cap screw is removed from the implant (through a small opening which is made in the gum tissue if necessary) exposing the implant (i.e. uncovering). Once the cover screw is removed, a taller healing cap is threaded into the implant body which protrudes above the gumline. The gums are allowed to heal around this “healing collar” for about one to two weeks. After the gums are healed, the implant is ready to have an abutment placed, upon which the actual replacement tooth or teeth can be supported. (In some cases, the healing collar may be placed along with the implant, making the later uncovering unnecessary.) The placement of functional teeth supported by the underlying implant is referred to as loading of the implant. In the case of a single implant and abutment, this would typically involve the fabrication of a porcelain crown. Depending upon the individual circumstances, steps in the process may be omitted, or added. (For example, in certain situations, implants may be used to support teeth at the time of placement, sometimes referred to as “teeth in a day”.)
In cases involving the replacement of a single tooth, an implant supported replacement tooth does not require “cutting down” the adjacent teeth as would be necessary to fabricate a bridge (a bridge is an artificial tooth or teeth connected to crowns on adjacent teeth, and permanently cemented.) In this instance, the implant acts as a new root for the replacement tooth, without affecting any other teeth, because it stands by itself. In recent years, implants have become the preferred method of replacing missing teeth in most patients.
In cases involving multiple lmissing teeth, the use of implants often obviates the necessity to rely upon the remaining teeth and gum tissue for support and retention of a removeable partial denture. ( a “partial” is a prosthesis which can be taken in and out of the mouth, usually composed of a substructure which clasps onto remaining teeth.) This is particularly advantageous when replacing several back teeth, because the support for chewing would otherwise be borne primarily by the underlying gum tissue.
When all of the teeth in the lower jaw are missing, dental implants present their most striking advantage. Although it is still sometimes necessary to wear a lower denture, which replaces both the missing teeth and compensates for the shrinkage in the gums and jawbone, a lower denture supported and held in place by implants, in contrast to a conventional tissue borne denture, is SOLID. Almost invariably, patients can expect to eat almost anything, and speak without fear of dislodgement of the denture. Predictably, this leads to an overall improvement in a person’s nutrition, social function, and enhancement in the quality of life in general.
Since conventional full upper dentures seem to be well tolerated by some patients, implants are sometimes not necessary. In contrast to lower plates, (which have an amazing propensity for dislodgement at inopportune moments and only provide at best 25% chewing efficiency) upper plates can be held in place by vacuum. This may keep them stable and comfortable for some patients without the use of implants.
Dental implant placement is primarily dependent upon the degree and character of available bone in the area of the mouth for the proposed implant. At times, the amount or density of the bone is deemed insufficient to provide for predictable implant longevity. Fortunately, almost all of these barriers have been overcome by the multitude of new bone-grafting techniques which we have employed with considerable success. However, adding new bone can also lengthen the treatment process.
The presence and/or location of nerves or other anatomic structures may entail a risk which outweighs the potential benefit.
Habits such as smoking, or diseases such as diabetes adversely affect the statistical predictability of success.
Risks involving any type of surgery are always present, in particular, post-operative infection, however we have found these incidences to be rare.
Since Implant Dentistry has only recently entered the mainstream, many Dentists have little knowledge and practical experience in the field, and lack state-of-the-art equipment. At Provenzale Dental, however, we have been placing and restoring Dental Implants since the early 1990’s and are one of the first of only a handful of Dental practices to own a 3-Dimensional CT Scanner.
General: the above information is intended as a simplistic overview of dental implantology, and the indications for their use must be evaluated on an individual basis.