Dental Bridges

A dental bridge is just one of the treatment options that we can use to replace one or more missing teeth.

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A dental bridges is a more traditional technique that utilises the teeth either side of a space to support a fixed appliance.
While dental implants are the best option these days in most instances, there is definitely still a place for this technique in modern dentistry.

Currently, the most common use for a bridge is to replace a single tooth, where the teeth either side of the space also warrant stabilisation and protection with crowns. After these supporting teeth are prepared for crowns, the laboratory produces a device whereby these crowns are fused together with a false tooth (pontic) joining them. The bridge is then cemented as one unit, giving you back a smile with no gaps.

Why do we replace missing teeth?

Aesthetics
Many teeth are replaced because their loss impacts heavily on a persons appearance.
As back teeth are lost, the facial muscles loose their support and ability to function correctly. The loss of muscle tone can cause the cheeks to collapse inwards.
When multiple back teeth are lost the bite can collapse and the lower jaw can rotate further closed than normal. The nose will travel closer to the chin and the lower face becomes shorter. Folds in the skin around the lips will deepen and in some cases this can lead to chronic cracking at the corner of the mouth.

Stability
A tooth remains stable in its position due to the forces exerted on it by surrounding structures. The teeth either side of it and those that oppose it prevent it drifting in these directions. Force exerted by the cheek muscles and the tongue prevent the tooth from tipping towards them. This balance of forces is disrupted when a tooth is extracted.
The amount of disruption is related to the position of the lost tooth.
A second or third molar (wisdom tooth) loss will cause little instability as its likely the only tooth that will drift around is the tooth it directly opposes.
The loss of the first molar and those in front of it can lead to great instability and drifting of surrounding teeth and the few teeth directly opposing them. Such movement of teeth can:

  • cause an increase in food packing where spaces between teeth develop,
  • see unusually high loads developing on resulting tilted teeth
  • cause disruption to the overall bite in the area.

It is not uncommon to see an increase in decay, gum disease and fractures in the surrounding area in the months to years post extraction.

Function
The loss of back teeth will reduce chewing efficiency, particularly as the bite destabilizes.
With bite collapse, the jaw joints can become overloaded and suffer damage long term, further effecting chewing efficiency and comfort.

Types of Dental Bridges

A dental bridge is named so because it ‘bridges’ a gap in the bite.
They are cemented or bonded to teeth adjacent to the space and are not intended to be removed. The adjacent teeth that are prepared and used to support the bridge are called ‘abutment’ teeth and the false tooth is referred to as the ‘pontic’.
There are 3 broad types of dental bridges that can be applied in various situations:

Traditional fixed bridges
The fixed bridge uses teeth either side of the gap for support and retention.
The most common fixed bridge used these days would be a 3-unit bridge (the tree units being the tooth either side of the gap and the false tooth to fil the gap).
Bridges of longer spans than this are rarely produced anymore as they tend to severely overload the supporting tooth, and the longer span leads to more likely fracture in the middle of the bridge (as bending forces are increased here).
The tooth either side of the gap is prepared to receive a crown. The crowns are made with a false tooth (or ‘Pontic”) joining them to form the bridge. The whole unit is then cemented permanently into position.
The bridge can be made using the following materials:

Porcelain fused to gold
This is the traditional ‘aesthetic’ bridge that has been used for many years. They look reasonable, and they have long term data to back their longevity.
Teeth either side of the gap are used for support. A gold sub frame is produced that joins the abutment crowns to the pontic, and this whole structure is then overlayed with tooth coloured porcelain to mask the gold.
This type of bridge is most useful at the back of the mouth where a tooth coloured restoration is preferred, but where ideal aesthetics are not as important.
They are not quite as aesthetic as the all ceramic bridge alternative as the porcelain must mask out dark underlying metal and they do not let light pass through them. Both of these factors cause the bridge to have different optical qualities to natural tooth structure. Therefore, they are used less at the front of the mouth these days. Overtime, a dark line can appear at their junction with the tooth. This can appear a little unsightly. This junction is often hidden under the gum line when the bridge is made, but the gum line will always move to eventually show this junction.
In contrast, All ceramic bridge junctions do not always have to be hidden in this fashion so they may be less irritant to surrounding gums, and wont fail aesthetically when gums do naturally move.

All ceramic
All ceramic bridges are now far superior to the ones produced in the past. While they have come a long way, we do not commonly place them towards the back of the mouth where forces are high. But they can outperform a traditional bridge at the front of the mouth.
At Melbourne Dentist we use Zirconia (IPS e.max ZirCAD) for dental bridges. Zirconia is tooth coloured and forms the substructure or framework of the bridge.
Without a metal substructure (like that found in the more traditional porcelain fused to gold bridges) they have excellent aesthetics.
In the past Zirconia bridges could be a little opaque in appearance, but the latest materials are now far more translucent and natural tooth coloured. Therefore, little characterising porcelain needs to be placed over the surface to make them look tooth like.
They are also now strong in quite thin sections and can be produced to conserve more tooth structure than a traditional porcelain fused to gold bridge.

Gold
Gold is still the most durable, predictable and conservative material available. It’s only issue is its colour.
At Melbourne Dentist we use only high percentage gold.
We don’t use semi precious or non precious metals as they do not fit as well and do not last as long.

Cantilever bridges
Sometimes, there is only one tooth adjacent to a space that is appropriate for use as the support for a bridge. This option is chosen in very limited circumstances. It is rarely appropriate at the back of the mouth where the bite forces are high, and the tooth to be used must be in good condition as it will be asked to take the load of two teeth. If this tooth is in perfect condition, the ethical dilemma arises of crowning a never before treated tooth.
One tooth is therefore prepared to accept a crown, and the bridge can be made from the same 3 types of material as the traditional bridge and thereafter be permanently fixed into place

‘Maryland’ bridges
The Maryland bridge does not use crowns to retain the pontic. It uses ‘wings’ that are cast to accurately fit to the inside surface of the supporting teeth.
The wing extends from the pontic (false tooth) and utilizes modern resin cement to bond it to inside surface of the lightly prepared enamel surface of the adjacent tooth.
They are generally only appropriate at the front of the mouth where bite forces are reduced.
The wing is usually made of a metal alloy and must be carefully designed so that it remains hidden at the back of the supporting tooth.
The Maryland’s major benefit is that it is extremely conservative of tooth structure – very little tooth preparation is required. This also makes it quicker and cheaper to place than a traditional bridge. However, it may be a less reliable long term solution than the traditional bridge.

The production process.

Before the bridge is prepared

Using a compromised tooth to support a new bridge is generally not advisable. There may be a few steps involved before getting a dental bridge fitted to ensure an ideal, long-lasting result. These steps involve assessment of the supporting teeth to ensure that the remaining structure is sound and that the internal nerves and blood vessels are healthy.
If a tooth has been previously root filled (root canal treatment), it is important to assess that this has healed adequately and that there is no sign of persisting infection or root fracture. Steps we may have to undertake include:

X-rays
X-rays may hint at infections involving the pulp (central nerves and blood vessels) as well as those involving the surrounding supporting bone. A tooth is not a good candidate to support a crown until such conditions are resolved. A further highly accurate CBCT scan may be required in some instances as some conditions are difficult to assess adequately with x-rays.

Vitality test
One in ten of all large restorations (including crowns that are components of some bridges) will suffer pulp death. If this occurs, root canal treatment will be required to clear the internal infection before the bridge is placed (otherwise the tooth will need to be extracted).
A cold test (Vitality test) is one way to assess the vitality of the pulp (central nerves and blood vessels).

Core placement
Any old filling material involved with the supporting teeth is removed, along with decay. Fractures that are present within remaining tooth structure are assessed for their depth, and for the possibility that they may extend into deeper areas of the root surface or into the pulp.
This is considered a separate billable procedure from the bridge procedure.

Root canal treatment
Any time a tooth is prepared for a bridge (including core placement) or any large restoration for that matter, there is a chance the pulp tissues may die. This is because all tooth preparation leads to inflammation of the pulp (internal blood vessels and nerves). If the drilling is deep, or the pulp was previously compromised, pulp death may be the end result of such internal swelling.
Some studies have estimated that the number of teeth requiring root canal treatment following large fillings and bridge preparations is around 10%.
These internal infections can develop very slowly so the tooth may need root canal treatment at any time, including a long time after the bridge is placed. However, most such infections show up around the time of core placement.
If discovered in this way, it’s best to apply root canal treatment to the tooth before the bridge is inserted.

Crown lengthening surgery
Sometimes, a defect in a supporting tooth leaves very little structure remaining above gum level. Crown lengthening can be applied to reposition the gums and underlying bone in this area. More tooth structure will now protrude through the gums in this area and the finish line of the bridge will be made to fit onto this newly exposed surface. This will provide more ideal support for the bridge and a more hygienically manageable junction. Sometimes, orthodontics can be used to move a tooth to similarly expose more tooth root surface that can then be used to support a bridge.

Visit 1

Anaesthetic
The tooth and surrounding areas are made numb. A specially formulated topical numbing gel is used prior to anaesthetic placement. This, plus other techniques learned over the last 30 years, makes this process more comfortable than ever.

“Bite” impression
A quick impression is taken of the tooth to be crowned, along with a couple of teeth either side of it. This will be used to produce a temporary crown at the end of the appointment.

Isolation of the tooth
Sometimes, the tooth is isolated from the rest of the mouth to protect surrounding structures by the use of an isolation structure called a rubber dam or dental dam.

Tooth preparation
The outer surface of a tooth, and any filling present, is removed by somewhere between 0.5 to 1.5mm to make room for the crown. The walls of the tooth are converted from convex to near-parallel sides. A finish line, or ledge, is produced circumferentially around the tooth to allow for a tight seal at the junction between the crown and the tooth.

Gum retraction and impressions
The gums are gently reflected away from the finish line with retraction cord.
This very fine piece of specialised “string” is placed in the trough between the gums and the preparation finish line. It’s removed just before the impression is taken, so impression material with a very fluid consistency can be applied to this area. A material of thicker consistency is then placed over this to record all teeth shapes in the area. Incredible detail is thus recorded of the finish line and the root surface just below this. This process is one of the most important elements in obtaining an accurately fitting crown and can take 15 minutes of time to apply correctly.

Temporary crown production
A temporary crown is produced and cemented over the preparation with temporary cement. This temporary crown is produced from the simple impression taken of the tooth before any work was done. Therefore, it most commonly feels exactly the same shape as the tooth did prior to preparation, and thus is readily tolerated by the tongue and cheeks for the two weeks that it takes for the crown to be produced by the laboratory.

Shade selection
A shade is taken using the surrounding teeth as a guide. If the tooth is a front tooth, we prefer that you visit the laboratory that will produce the crown. There you will meet with expert technicians that will be involved in the crown production who will take detailed notes on the shade, shape and texture of surrounding teeth to ensure the crown matches your teeth nearly imperceptibly.

Visit 2

Anaesthetic
Little actual tooth preparation is carried out at this visit but the teeth need to be thoroughly cleaned and polished after the temporary bridge is removed, and this process will normally require the teeth to be numb.

Bridge fit-check
While some clinics now produce bridges in house, we still believe that the most ideal result will be achieved if the bridge is produced in a dental laboratory. Sure it takes a little longer, but it will be designed by an actual technician (rather than dental support staff), and it can be ‘re-marginated’ for ideal fit after milling, characterized for realism and glazed for smoothness and beauty in a way that can not be replicated within most all dental practices.
Before the bridge is cemented into place, it must be critically assessed for fit to your tooth, and its correct relationship to the teeth it surrounds and opposes.

Gum retraction and impressions
The gums are gently reflected away from the finish lines with retraction cord to ensure they are completely out of the way of the edges of the bridge.

Cementation
The teeth surfaces are prepared, along with the fitting surface of the bridge, to accept permanent cement and the bridge is then gently pushed into place. Once the cement has set, excess cement is cleaned away and the bridge is again assessed.
Sometimes there can be mild sensitivity to hot and cold temperatures for a few weeks after cementation. This is generally temporary and should resolve on its own.
If the bridge feels a little odd in the bite after the first 48 hours, you will likely need to return to our practice to have your bite checked and adjusted – a simple 5 minute procedure.

The benefits and risks with dental bridges

Benefits

  • They can stop the remaining surrounding and opposing teeth from moving into the gaps. Such movement will always put the other teeth involved under increased stress leading to further breakdown and collapse of the bite
  • They can return chewing function and allow for proper nutrition and digestion
  • They can cheaper than an implant supported crown, particularly if the adjacent teeth warrant crowns being placed anyway.
  • They can be made to look and feel like natural teeth in the mouth.
  • They can take as little as 2 weeks to complete, whereas implants can take a few months and orthodontics a couple of years to complete properly.
  • They are firmly fixed in place and do not move around in function as removable partial dentures can.
  • They can be used to support the cheeks and lips as a ‘sunken’ look can develop with multiple tooth loss.
  • They can help protect the remaining teeth.
    • With fewer correctly connecting teeth, the remaining teeth will be forced to take on increased loads leading to them chipping and breaking.
    • In the absence of back teeth, the front teeth can be overloaded and are more likely to drift apart or to break
  • They can help to retain correct ‘vertical dimension’.
    • When fewer teeth remain, those that do will tend to drift and wear down leading to a collapse of the bite.
    • This puts undue stress on your jaw joint and effectively places your chin closer to your nose.

Risks

  • The supporting abutment teeth will take on more load which could be a problem if there is limited remaining structure related to previous damage.
  • Once cemented in place, the destiny of all teeth involved are tied together. If there is failure around one tooth involving the bridge, the whole device most often has to be removed and replaced with another bridge.
  • All tooth preparation leads to inflammation of the pulp (internal blood vessels and nerves). If the drilling is deep, or the pulp was previously compromised, pulp death may be the end result of such internal swelling.
    Some studies have estimated that the number of teeth requiring root canal treatment following large fillings and bridge preparations is around 10%.
  • Bridges require increased daily maintenance to adequately clean under and around the pontic.
  • Microscopic bacterial leakage can occur at the junction with one of the supporting teeth. As the other supporting tooth stays firmly fixed, this leakage can develop into decay with no obvious instability of the bridge. It is often impossible to detect decay under a bridge support, even with x-rays. Thus considerable damage can occur to an abutment tooth with limited chances to detect it.

Alternatives to dental bridges

Do Nothing
Sometimes, the loss of a tooth is neither aesthetically displeasing nor an issue with regards to reduced function or bite instability. This is often the case with second and third molar loss.

Removable partial dentures
These appliances may be a good option if you are missing multiple teeth, or you expect to lose several more teeth. They may be used as a provisional appliance before the more long term bridge or implant option is chosen.

Cobalt chrome based partial dentures
Modern chrome based dentures can be surprisingly thin, accurately fitting and light weight. At Melbourne Dentist we use the premium brand ‘Vitallium’ as the ‘skeleton’ of the denture.
Read more

Flexible dentures
‘Valplast’ partial dentures are extremely tough, light, flexible and resistant to fracture.
Read more

Dental implants
Dental implants are reliable, safe alternatives for replacing missing teeth that more and more people are using to improve function and appearance.
Read more

Orthodontics
Orthodontic treatment can sometimes be used to close spaces after tooth removal. If possible, they offer an ideal solution whereby implant placement is not requires, nor is preparation of any teeth to support bridges. Other bite issues can be corrected at the same time.

Maintaining a dental bridge

Teeth that support a dental bridge are never as strong or easy to clean as completely intact teeth. Proper care is needed to ensure this device provides you long trouble free service.

The following information may help you take care of your new dental bridge.

Immediately after placement

  • Take care not to damage areas of your mouth that remain numb. Don’t eat or drink anything too hot until sensation completely returns
  • There may be initial sensitivity of the supporting teeth to hot or cold. This should resolve by itself. If the teeth involved slowly becoming more sensitive, or a little tender to bite on, please give us a call. It’s likely that the bridge biting surface needs a simple adjustment.
  • It can take a little while to get used to the feel of a new bridge in your mouth. Sometimes your tongue may get in the way and be bitten, but it will soon learn to stay out of the way. In the mean time you may have to take a little care and eat more slowly.

Oral hygiene measures

  • While the surface of a bridge is highly polished and glazed to prevent plaque build up or staining, it has a weak spot – the ‘margins’. The margin of a bridge is where it meets the tooth surface. We try our utmost to ensure this junction is as close fitting as possible to allow for good daily maintenance. However, at a microscopic level, this area is not smooth and therefore it requires particular attention during cleaning.
  • It is preferable to use an electric toothbrush to maintain a crown.
  • Floss or interdental brushes should be used to clean between the teeth at either side of the crown

Controlling bite forces

  • Hard biting, clenching or grinding will hasten damage to the crown and force its early replacement. Sometimes, clenching or grinding will occur during the day, particularly during stressful periods of your life. Some sports or exercise (eg. weightlifting) can cause heavy clenching. Most people who grind or clench do so at night while asleep, and if this is suspected, an ‘Occlusal Splint’ should be considered. READ MORE
  • Beware of habits that may place undue stress on the porcelain. Although very strong, porcelain can chip, particularly if it comes up against a similarly hard and brittle object. Chewing on very hard foods (like bones, stone fruit pips, crab shells and ice) should be avoided. Chewing on pens or fingernails will also lead to damage as will using the crown as a tool (eg opening bottles, cracking nuts).

The average crown should last from 10 – 15 years (depending on local forces and materials used).
As with your natural teeth, the longevity of a crown depends on good daily dental care. Its life expectancy will also increase with regular continuing care appointments.