Up until about 25 years ago conventional bridges--fixed, removable, partials--were the standard of care for tooth replacement. About 25 years ago, the dental implant was introduced. In the intervening time, titanium implants (sometimes in conjunction with bone grafting) have become the standard of care for tooth replacement. Many people may still wonder why.
There are several reasons.
Tooth Preparation
Conventional bridgework often involves the grinding down of the tooth enamel to place the hardware that will support the bridge. Wherever possible, dentists usually prefer to go with the least-invasive procedure, particularly if the tooth or teeth being replaced are between two "virgin" teeth--that is teeth that have never had any previous dental work on them.
Dental implants, on the other hand, don't require the grinding down of the enamel. The restoration is supported by the dental implants that have integrated with the bone in the jaw. Most dentists will prefer to place dental implants particularly for single tooth restorations and those places where the edentulous (toothless) space is in between virgin teeth.
In some cases, it may be possible to use a combined implant/conventional bridge set up. This may be used where several teeth need to be replaced and there are "non-virgin" teeth on either side of the space. In this instance, there is the option for one or two implants to be placed in the space and the bridge to be anchored on either end by the two "non-virgin" teeth. (There are cost advantages to this as well, which we will look at a little later.)
How Bone Reacts
Many people don't realize how much their jawbone health is predicated on having functioning teeth in place. Those people who have lost their teeth and not replaced them will notice over time that the quality and quantity of bone in that particular site will deteriorate. (Some people are lucky enough not to have too much "resorption," but there is always some.) Even those who opted to go with conventional dentures will experience bone loss over the years.
Your body's bones need weight to generate bone marrow, which is the heart of your bones' structure. Without that weight, bone marrow production will decrease, potentially leaving your bones brittle and unable to support basic function--such as what happens with osteoporosis. In the case of dentistry, this can be rectified in many cases--though not all--with bone grafting, which is often done in patients who have been edentulous for a long time, before placing the implants.
If, however, an implant-based restoration (either crown or bridge) is done immediately or soon after tooth loss occurs, the chewing function carried out on that implant will keep the bone vital and strong. Once the implants are placed where bone grafting has been required to replace lost bone, it is hoped that renewing functioning on that bone will keep it strong. This happens in the vast majority of cases, but cannot be guaranteed for each patient.
Longevity, Stability, and Function
One of the main comparisons between a conventional bridge restoration and an implant-based restoration is how long the respective restorations will last.
A conventional bridge restoration (conventional dentures also carry about the same lifespan) will last between 15-20 years.
An implant-based restoration, with a properly osseo-integrated implant, the restoration is expected to have a lifespan of more than 30 years. The chewing surface of the crown on that implant may need be replaced. The bridge that is supported by the implant may need to be replaced, but the implants--in the vast majority of cases--will not.
Implant-based restorations are also more stable. There is less shifting, particularly of implant-supported bridges or dentures, because the bridge or denture is not suspended (hanging off) between the two teeth on either side of the space. The "suspended" portion is actually supported by the implants. This makes for much better function and people are able to eat regular food--apples, steaks--that they might have avoided before because their conventional bridge or denture just couldn't handle the bite forces needed.
Esthetics
Along with longevity, esthetics are a major concern when considering which type of restoration to go with.
The implant is buried below the surface of the gum and the crown/bridge restoration placed on top of that implant cover the abutment or screw that protrudes through the gum tissue. If done properly, no one should notice the difference between your natural teeth and your restorations.
You may have to have tooth whitening done so that your other teeth match the color of the porcelain crowns used in the restoration, but that is entirely optional.
Because the implant structure is below the gum line, it means that the crowns, even on an implant-supported bridge will sit along the gum just like your normal teeth. In some cases, soft tissue grafting may be necessary (usually taken from the wisdom tooth area or palate) to make sure the gum line is even all the way along.
Conventional bridgework and dentures don't quite look as natural. Sometimes there is metal showing. Sometimes the spacing of the teeth on the bridge or denture aren't quite the same as the rest of your teeth. Technology has improved in this area, as well, but still can not match the esthetics of an implant-based restoration.
Costs/Insurance
On a unit-by-unit basis (a unit relating to each tooth needing replacement), implants do cost a little more, but when you take into account the longevity issues, the better bone health issues, and the esthetic issues, it can save you money in the long run.
Implant-based restorations are often the main alternative to root canal treatment where the viability of the tooth is in serious question--that is, even with root canal treatment there is still the possibility that tooth will be lost. In some cases, the tooth lasts the patient a long time. In many cases, though, the tooth still fails and after paying $1500 for a root canal, they face the choice of having to pay $1500 for an implant, too.
Many insurance companies are realizing that dental implants are the preferred method of treatment for tooth replacement, but many still do not cover implant placement procedures. They may cover the consultation, and the crown or bridgework that follow, but not the implants themselves.
Some insurance companies will offer the patient the equivalent of what they would have paid had the patient gone with conventional bridgework. For example, if the insurance company's policy is to provide 80% coverage for a conventional bridge, they will offer that 80% coverage to the patient that opts for an implant-based restoration. In many cases, the insurance companies will require a note from whoever is doing the implant treatment (dentist, oral surgeon, endodontist, periodontist) to confirm that implant treatment in this case is the best course of treatment. In some cases, it is the only option for treatment available.
But, as of now, many insurance companies still do not cover implant placement--either the hardware or the surgery required.
Earlier I mentioned how cost-effective an implant-supported bridge or denture can be. In the cases where several teeth need to be replaced, including those with no teeth whatsoever, there is always the option of placing individual implants to replace all the teeth (usually 10-15 in the upper and 10-12 in the lower), or going with an implant-supported bridge, which only requires 4-6 implants to be placed. The patient still walks away with an esthetically ideal result and the security of having their restoration supported by implants, but can save 50 percent off replacing every tooth.
Whether this is an option in your particular case, though, needs to be discussed with your dentist/oral surgeon...whoever you are consulting with to do the treatment. Each treatment plan is decided on a patient-by-patient basis. Implants may not be right for everyone.
In some situations, implant placement will not be possible and it is in those cases where conventional bridgework can done (that is a bridge that is supported by other teeth, not implants.)