Congenitally Missing Teeth

Some of us will have 32 teeth develop during our lifetime. This has been considered a normal complement of teeth. More often than not, however, we do not develop a full set of 32 teeth. It is quite common for people to be missing one or more of the third molars (wisdom teeth). And as the jaw sizes of modern human beings have decreased in size, it is not unusual that there is no room for the proper placement of the third molars in a mouth, and they must be extracted.

Not as common, but not at all unusual, is a condition in which certain permanent front teeth never develop. When permanent teeth don’t develop, they are considered to be congenitally missing. The term for this condition is congenitally missing teeth. When this happens, it is frequently one or both of the upper lateral incisors, which are smaller teeth on either side of the two top front teeth. Less often, the permanent eyeteeth (canines) or premolars don’t develop.

The problem that results from congenitally missing teeth involves the space where the tooth (teeth) should have been. The teeth nearest the space shift into different positions to fill the gap, often resulting in a crowded smile—when in fact, some teeth are missing!

The problems resulting from missing permanent teeth can be reduced or eliminated with early detection and a plan for future treatment. The usual treatment involves orthodontics to move the permanent teeth into better position or keep the permanent teeth in the correct location. Because we treat missing lateral incisors so often, the treatment routine is well established. The best aesthetics, the most natural look, will be achieved by leaving the adjacent permanent central incisors and canine teeth in their customary places.

When there are missing lateral incisors, it is likely that we will recommend moving the eyeteeth (canines) into their positions. This will keep the bone in the missing tooth space at the proper level. We will then recommend moving the eyeteeth back into their proper positions. This may sound like extra treatment, but it is needed to keep the bone at the proper height for future tooth replacement treatment.

The sequence of treatment is orthodontics as early as necessary to maintain the space. The further the teeth have shifted from this original position, the more orthodontic treatment will be necessary. Then, while the child and mouth are growing, a removable replacement tooth is made. This appliance is worn until the teeth are ready to receive the implant or bridge, after age 18 or so when the mouth and dental structures are more mature.

When the permanent teeth further back in the mouth are missing, it is common for baby teeth to be retained in these spaces. Sometimes the baby teeth can last for years, but they do not have the root structure to remain stable over a lifetime. Because the retained baby teeth are meant for a small mouth, they do not have the right size, shape, or function as the permanent teeth. When lost, they can be replaced with implants or a bridge. Your own particular situation will determine the best course of treatment. 

Implants, Crowns, and Bridges vs. Natural Teeth

Nothing can replace the natural teeth you were born with for chewing and function. However, very few people go through life without having teeth filled, crowns (caps) placed, or bridges and implants used to replace missing teeth. Crowns, bridges, and implants are the best answer and closest to your natural teeth, but they are not the same as healthy, natural teeth.

Crowns

Crowns are used to reconstruct a single tooth broken down by dental decay. Crowns are made of ceramic, resin, porcelain, porcelain plus metal, or resin plus metal materials. They are bonded or cemented onto the prepared tooth and cannot easily be removed from the tooth once placed. If the tooth was in good alignment before the crown was prepared, the crown will be in good alignment. If the tooth was misaligned before the crown, sometimes the crown may be made to obtain a more ideal shape and position. It is cleaned and flossed just like a natural tooth and is most like real teeth.

Bridges

Bridges are crowns that are attached together, suspending the crown portion of a false tooth in or over the space left by the missing tooth. A bridge can be used to replace one or several teeth. Sometimes a bridge is used to splint loose teeth together in order to make the teeth more stable. Bridges are usually made of metal covered with either porcelain or resin. Some of the newer bridges are made of all resin or all ceramic materials. They are cemented or bonded onto the existing prepared teeth and are not easily removed once placed. The bridge teeth can be brushed the same as natural teeth, but since they are attached together, must be flossed differently by using a floss threader or other device.

The teeth are generally the same shape as natural teeth. However, if the existing teeth (abutments) that are used to anchor the bridge have moved from their original position because a tooth or teeth have been missing for years, the added tooth (pontic) may be longer or shorter than the tooth that it is replacing. With a bridge, the false tooth will most often butt up against the soft tissue ridge where the removed tooth was.

The shape of the tongue side of the false tooth varies. It is usually smaller on the tongue side and completely fills the space. Food will have more of a tendency to collect in this area, so you must be prepared to clean it. If the missing tooth has been gone a long time, the ridge may have shrunk considerably, and the pontic tooth will be longer that the teeth on either side. If this is the case, there are several periodontal procedures that can be done prior to the construction of the bridge. These procedures will build up the tissue to its former height. The more your mouth has changed from its normal state, the harder it is to make new teeth look and feel natural.

Implant Crowns

Implant crowns are used to replace single or multiple missing teeth. They are either cemented or screwed-retained onto an implant fixture. The crowns are made of porcelain or resin and metal. But they have some significant differences from the natural teeth they replace. Teeth are supported by a root or roots that are irregular in shape. Implants are round. The cross-sectional of the implant will never match that of the tooth it is replacing. A multirooted tooth may be replaced by a single implant, so the manner in which an implant crown comes out of the soft tissue ridge will appear different from a natural tooth. There will be more space between the implant root and the adjacent teeth. Implant crowns are often cemented with temporary cement. This allows the dentist to easily take off the crown and evaluate how the implant is doing. Crowns on teeth are usually cemented with a final cement. Implant-supported crowns are wonderful, but not the same as natural teeth with crowns. Be prepared for some differences. Expect more maintenance on your part and in the dental office with crowns, bridges, and implants.

Smokers take note: There is a heightened risk of dental implant failures among smokers—as much as 20% greater failure rate!

Maryland Bridge (Bonded Resin Retainer)

The Maryland bridge, or bonded resin retainer, is an alternative to implants and conventional crowns to replace missing teeth. This type of replacement procedure can be considered when the space to be restored is next to teeth in good alignment that are not heavily restored with filling materials. Because this type of bridge is adhesively bonded to the enamel on the abutment teeth, having adequate enamel is important. A Maryland bridge is fixed into place and is not meant to be removed at night.

Maryland Bridge vs. Fixed Bridge

One advantage of this process over a conventional bridge is that a missing tooth can usually be replaced with a minimum amount of preparation (drilling) of the remaining teeth. It is not necessary to prepare the tooth to the same extreme degree as with full tooth coverage restorations (crowns or caps). This method is an extremely conservative procedure. It is also less expensive (about one quarter less) than a conventional bridge. Tissue health around the abutment teeth is usually excellent because little or no preparation of the tooth structure near the gingival (gum) tissues is needed. Unlike conventional full coverage restorations, teeth prepared for a Maryland bridge retainer will not need endodontic treatment (root canal therapy) at a later date.

If the patient has abusive eating or bruxing (grinding) habits, this type of restoration is contraindicated. Although we do consider it more of a restoration for posterior (back) teeth rather than anterior teeth, it does display metal more so than a conventional bridge. The biggest disadvantage of a Maryland bridge is that the expected life may not be as long as that of a conventional bridge made of full coverage crowns. This technique was only introduced in the early 1980s and therefore does not have the extensive successful history of full coverage bridges. While breaking of a Maryland bridge is not likely, debonding can occur, requiring a re-cementation. In some rare instances, it might have to be redone. In either case, you may be charged a fee for the procedure. A Maryland bridge is a fixed replacement for a missing tooth, but one that will need to be redone in the future. The success rate at 5 years of Maryland bridges in our practice is approximately 80%. However, this is a much better result than the national average, which shows a success rate of about 33% at 4 years. Maryland bridges are most appropriate for single-tooth replacement. 

If dental implants are not an option for you for tooth replacement and you do not want the teeth on either side of the space to be radically prepared (cut down or drilled), then you should consider the Maryland bridge technique. For many patients, the advantages of less drilling of the teeth and the reduced cost make it a desirable alternative.

If you have any questions about the Maryland bridge technique, please feel free to ask us.