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Overdentures & Fixed Dentures

Implant-supported replacement teeth that look and feel great

By Dr. Mark Montana

This article is endorsed by the
International Congress of Oral Implantology.

Not too long ago, losing most or all of your natural teeth was regarded as an inevitable part of aging. The answer to that problem was essentially the same tried-and-true device that your parents and grandparents might have used: a set of removable dentures. But in recent decades, high-tech systems for tooth replacement built around dental implants have opened up better options for people with missing teeth. Two of today's most popular choices are implant-supported overdentures and fixed (non-removable) dentures.

Dental implants are small, screw-like devices that are inserted into the jaw bone in a minor surgical procedure. They provide a solid anchorage to support replacement teeth. One implant plus a prosthetic crown (a replacement for the visible part of the tooth) can be used to replace a single tooth; two or more implants can support several adjacent teeth, in the same manner as a conventional dental bridge. It's also possible to use a number of implants to replace a whole arch (upper or lower row) of teeth — the same situation that could be addressed with a traditional denture. But there's a world of difference between removable dentures and implant-supported replacement teeth.

Alternatives to Traditional Dentures

While conventional dentures remain a viable option, they come with a number of disadvantages. Getting used to dentures requires some lifestyle adjustments: Dentures must be removed and cleaned daily to avoid problems with hygiene and bad breath, and they sometimes cause difficulties with speaking and eating, particularly with more challenging foods. Over time, denture wearers also generally experience significant bone loss in the jaw. This causes the dentures to fit poorly, requiring them to be re-lined or replaced. Bone loss can also change the facial contours, making a person look older than they really are.

Recently, implant-supported fixed dentures and overdentures have gained popularity as alternatives to traditional dentures. These tooth replacement methods offer a number of advantages over removable dentures: They can stop the progression of bone loss, restore the ability to eat and speak properly, and help rejuvenate the appearance. One major difference between the two systems is that an overdenture can be taken out for cleaning at home, while a fixed denture is designed to stay in your mouth permanently. There are several reasons why either system might be recommended, based on an individual's particular needs. Let's take a closer look at what the options are and how they work.

Overdentures

An overdenture, as its name implies, is designed to go over a supporting structure. This could be natural teeth, but more often dental implants are used. In the upper jaw, the supporting structure for an overdenture is generally a metal frame anchored by three or more implants. If it's in the lower jaw, usually only two implants are needed without the frame. The overdenture contains pearly-white prosthetic crowns, plus some simulated gum tissue, which is often made of pink acrylic (plastic). In overall appearance, it's not unlike a traditional denture; in fact, in some cases, regular dentures can be converted to overdentures.

The main feature setting the overdenture apart from a traditional denture is that it gains support and stability from dental implants. A traditional denture, on the other hand, is held in place by the suction generated from its close fit with the gum tissue. Clips or other fasteners keep the overdenture securely retained in the mouth and prevent it from moving excessively; yet it's possible to release the overdenture from the frame for daily cleaning or occasional repairs very easily.

Fixed Dentures

An implant-supported fixed denture also contains prosthetic crowns, and has simulated gum tissue as well. (A similar appliance, the implant-supported bridge, consists only of crowns and has no gum tissue.) But unlike the overdenture, this device can't be removed at home; it is fixed in place by your dentist. Its firm connection to the implants gives the fixed denture a solid support that's comparable to natural teeth. It's also more like real teeth because it isn't removed for cleaning; instead, you brush and floss daily as you would with natural teeth. However, a fixed denture requires a minimum of four to six implants to work properly, all of which must be placed in suitable, good-quality bone. This makes it a more complex (and more costly) system.

Similarities and Differences

Some other major differences between these two systems include how many implants are needed to support the replacement teeth, and how well you can keep them clean at home. These factors are important when we consider which type is best suited for an individual's unique situation. As a prosthodontist, it's part of my job not only to evaluate the clinical issues related to the different systems, but also to listen to each patient's needs and desires.

One determining factor may be whether a person has already worn traditional dentures for some time. In this situation, there may already be a significant loss of bone, which often means that the lips and cheeks need to be supported to keep them from looking sunken in. Adding thickness to the denture can help make up for the missing bone structure. But when this is done with a fixed denture, the thicker material sometimes creates an oral hygiene problem. While it is certainly possible to clean underneath a fixed denture, it's often more challenging to do so successfully. In the absence of regular, effective cleanings, periodontal disease or other issues may begin to cause trouble in the mouth.

On the other hand, a removable overdenture makes hygiene easy: Both the denture and the gums are fully accessible for cleaning. What's more, a long-time denture wearer will already be used to taking the prosthetic out of the mouth for cleaning. For many, this has become such a habit that having a fixed denture can cause concern about proper cleaning. Denture wearers are also used to experiencing a small amount of 'play' in the replacement teeth, which is a feature of overdentures.

Someone new to dentures, however, may have the opposite experience: Solidly anchored in the jaw, fixed dentures feel more like natural teeth; overdentures undergo small movements during chewing or speaking, which may take some getting used to. And like natural teeth, fixed dentures are not removed for cleaning.

Upper vs. Lower Jaw

Another factor to consider is whether the upper or lower jaw needs replacement teeth. Generally, in order to achieve good support, either a fixed or removable system will require a minimum of four implants in the upper jaw. That's because bone tissue there is often thinner and softer compared to bone in the lower jaw. But clinical experience shows that only two implants may be needed to retain an overdenture in the lower jaw. As a result, the cost of an overdenture in the lower jaw may be far less expensive than a fixed denture in the same jaw. In the upper jaw, however, the need to place several implants generally means the cost difference between the two restorations will be minimal.

When cost is a decisive factor, the lower jaw offers another advantage: It's often possible to start with a low-cost overdenture and move to a fixed system. Using CT scans of the patient's mouth and high-tech computer imaging systems, dentists can plan the optimal location of implants for a fixed system. We can then place just two of those implants to start with — enough to support an overdenture. Later on, additional implants can be placed, and we can move to a fixed denture.

Which Is Right for You?

When it's time to make the choice between overdentures or fixed dentures, it's often necessary to strike a balance between aesthetic, functional and practical needs. With a fixed solution, for example, we must weigh the positives of improved function against the possible difficulties of at-home cleaning. Where there has been significant bone loss, we may find that giving facial features more support with a fixed denture makes it harder for an individual to maintain good oral hygiene due to the denture's size and location.

We also take into account each person's needs and wants for their new teeth. Are they embarrassed about having removable teeth — or just looking for a way to chew better? Are they a younger person looking to replace their teeth for the long term, or a veteran denture wearer? Can they perform good oral hygiene and/or keep a removable overdenture safe from breakage? And, of course, what's the overall cost of their treatment?

If you're considering one of the modern alternatives to dentures, it's important to consult with a dental professional about your situation. We can provide the information you need, share our clinical experience, and help you make the choice that's best for you.



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