A dental is a fixed dental used to replace one or several missing teeth by permanently joining an artificial tooth to adjacent teeth or dental implants.

dental bridge

Dental bridges are also used to protect and reshape teeth that have undergone major destructions and prevent complications that may arise as a result of tooth loss.

There is a wide variety of dental bridges. The type of bridge that is designed for a particular clinical situation depends on many factors such as geographical location, patient desires and financial situation, practitioner preferences etc.

Although in some countries (mainly the most developed ones) dental implants tend to replace bridges (or, if more teeth are missing, bridges are supported exclusively by dental implants),traditional dental bridges (supported by natural teeth) are still widespread throughout world.

Parts

A dental bridge consists of two components :  Anchor crowns

The anchor crowns (also known as retainer crowns) are two (or more) dental crowns that are cemented on the teeth adjacent to the toothless gap to support the bridgework restoration.

The two anchoring teeth are called abutment teeth. A traditional bridge is supported by natural teeth (or by post and cores when remaining tooth structure is inadequate).

Bridges supported by dental implants will be discussed in a separate chapter.

 Pontics or artificial teeth

The artificial (or false) teeth are placed between the anchor crowns and basically replace the missing tooth or teeth. Depending on the clinical situation and the number of missing teeth, a dental bridge can have one or more pontics.

A made off several dental crowns joined together but without any pontics (because there are no missing teeth) is also considered as a dental bridge.

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MAIN BENEFITS

Dental bridges have two major benefits :

 Restoration of the missing teeth

 Prevent the complications that can occur after one or more teeth are lost 1. Restoration of the missing teeth

The primary role of a dental bridge is to restore (or replace) the missing teeth. Besides "bridging" the toothless gap, the bridge will also "" the abutment teeth.

A proper dental bridge will have to participate at dental process just like natural teeth (or very close too). This will ensure optimum comfort and a short period of adaptation.

Chewing process

A dental bridge is permanently fixed to the abutment teeth. All chewing forces pass along the abutment teeth to the jawbone.

The amount of pressure that acts on each abutment depends on the extent of the bridge (the number of missing teeth) and abutment teeth characteristics.

Look at the picture above: all chewing forces that act on the pontic are passed to the abutment teeth.

Unlike bridges, some removable rest exclusively on the . Consequently, chewing comfort decreases (because the patient will chew on his gums instead of his teeth) and getting used to removable dentures takes a little longer.

Very important: Dental bridges do not pass any chewing forces to the gums. Basically, the whole chewing process is performed on the teeth. That is why chewing on dental bridges has a natural comfort. Aesthetics

Tooth loss severely affects aesthetics, especially if the area is visible. Therefore, restoring the aesthetic function is, for many patients, the most important goal.

Restoring proper aesthetics greatly depends on the manufacturing material. Porcelain or zirconiumbridges are aesthetically superior.

restoring aesthetics with a porcelain dental bridge; before and after

Phonetics and pronunciation

If front teeth are missing (especially the upper incisors) the normal speech will suffer, particularly the pronunciation of consonants. When a new dental restoration is manufactured, it takes time to adapt the speech to the new conditions.

Dental bridges, compared with removable dentures, are small restorations that are permanently cemented to the abutment teeth ; getting used to normal speech takes less time.

2. Prevention of complications that can arise after teeth loss

After teeth loss, important changes that can severely disrupt dental processes may occur. These changes will seriously complicate the steps of the restoring treatments.

That is why it is advisable to begin planning for dental restorations soon after the extraction took place. Restoring missing teeth with dental bridges has many advantages. Well-executed and properly maintained, bridges ensure high comfort and aesthetics and patients get accustomed with them in a short time.

 Bridges are fixed prosthetic restorations that do not require periodic removal for cleaning

Because of this advantage, many patients prefer them against removable dentures. Bridges are permanently fixed by cementing the anchor crowns to the abutment teeth and there is no need for periodic removal.

Many patients are more comfortable with the idea of a fixed restoration rather than a removable one.

 Patients get used to dental bridges in a short time

Bridges are small and lightweight dental restorations. After the definitive cementation, getting used to dental bridges takes less time than in case of removable dentures (or other more complex restorations) which are larger and heavier.

dental bridge removable partial denture

 Dental bridges provide excellent chewing comfort

This is because all chewing forces are passed to the abutment teeth and not to the gums underneath. Therefore, teeth perform the mastication, which is the natural way. By contrast, removable dentures rest exclusively on the gums so the chewing process (or part of it) is performed on the gums.

 Aesthetics are very good

When aesthetic demands are high, it is advisable to opt for porcelain or zirconium based bridges, which are aesthetically superior.

 Few appointments are needed

Bridges can be completed in two sessions, while removable dentures need at least 4 appointments to be completed. Dental implants need 3 to 6 months after the surgical insertionto fuse with the bone through a biologic process called osseointegration.

 Life span and prognosis are good

To ensure this goal, dental bridges need to be properly maintained. DENTAL BRIDGE DISADVANTAGES

 Bridges require the preparation of the abutment teeth

To ensure the bridge support and insertion, the abutment teeth need to be properly prepared. This operation involves permanently removing much of the tooth's original structure, including portions that might still be healthy and structurally sound.

It's the biggest disadvantage as it leads to the loss of large amounts of healthy tooth tissue and sometimes even tooth devitalization and endodontic treatment. Therefore, restorations supported exclusively by dental implants have the big advantage that teeth adjacent to the gap remain untouched.

This disadvantage stands out especially when abutment teeth are perfectly healthy without any fillings or cavities.

 The abutment teeth may show increased sensitivity at external stimuli

Usually, after the preparation, one or more temporary crowns are constructed. These devices will protect the abutment teeth until the definitive restoration is completed.

If no temporary restoration was designed, abutment teeth may show an increased sensitivity to hot or cold stimuli until the bridge is definitively cemented. Traditional dental bridges have many indications.

 Restoration of partial edentulism if enough healthy teeth remain on the dental arch to support the bridge

It is the main indication of dental bridges. Partial edentulism is a condition where one or more teeth (but never all) are missing from the dental arch.

If there are not enough teeth to support the dental bridge, another type of dental restoration has to be designed: removable denture or a restoration supported by dental implants.

dental bridge indication : partial edentulism with 2 missing teeth

dental bridge after definitive fixing

 Restoring teeth with advanced destructions, erosions or large fillings

A dental bridge can be designed when some teeth show advanced destructions, large cavities, erosions or old unsightly fillings.

The dental bridge, besides replacing the missing teeth, will restore the morphology of the teeth with advance destructions. tooth bridge indication : teeth with destructions and old fillings

the designed dental bridge

 Aesthetic restorations

Sometimes, one or more teeth are out of shape, out of place, or may show discolorations, yellowish color or unsightly fillings.

If changes are not too advanced, an aesthetic dental bridge may be a viable therapeutic option.

porcelain dental bridge designed to restore aesthetics ; before and after

 Restoring teeth with high degrees of abrasion

Abrasion is a condition that can occur both due to physiological wear of the teeth, or due to pathological conditions (e.g. ). Over time, teeth become small and unsightly. This condition is difficult to treat.

In some situations, it is possible to restore these teeth by constructing a dental bridge. It is very important to re-establish the appropriate bite or dental ; otherwise, the patient may have a permanent discomfort when chewing.

dental abrasion ; teeth become small and unsightly

 Treatment of occlusal disorders

In some clinical situations, for various reasons, the dental occlusion (or bite) becomes inadequate. These conditions are usually accompanied by pain and discomfort in the jaw muscles and/or TMJ, headaches or migraines, eye or sinus pain and, sometimes, other symptoms.

These conditions call for an occlusion readjustment. Sometimes, this can be achieved by manufacturing a complete dental bridge, a bridge that covers all teeth of the dental arch. Ideally, this bridge will have new and proper contacts with the opposite teeth and the pain will gradually disappear.

In practice, these conditions are extremely difficult to treat. They call for many sessions and a lot of patience. Usually, the treatment plan is quite complex and manufacturing a dental bridge may be just one of the many steps.

 Replacement of old, inadequate restorations

Old restorations that don't meet the functional and aesthetic demands need to be replaced. Generally, after their removal, the will reassess the clinical situation and develop a new treatment plan. If enough supporting teeth are present, a dental bridge may be the therapeutic solution.

dental bridge indication : replacement of old, unsightly restorations; before and after

 Dental implants

Bridges supported exclusively by dental implants are excellent solutions. We will discuss dental implants in a separate chapter.

TOOTH BRIDGE CONTRAINDICATIONS

 Treatment of partial edentulism if there is not enough support

If the number of abutment teeth is not enough to support the bridge or some teeth are unsuitable (show large destructions, are too loose etc.), it is advisable to opt for a different type of prosthetic reconstruction: removable dentures, restorations on dental implants.

more about abutment teeth selection

 Poor oral hygiene

It is not desirable to start a dental restoration (particularly a large one) until oral hygieneprocedures are improved.

 General conditions Some severe conditions need a general checkup before starting any dental treatment. Depending on the condition, the dentist will call for a qualified doctor opinion.

Dental bridges have been used in dentistry for a long time. Dentistry has evolved and new solutions have emerged.

Despite that, dental bridges are widely used throughout the world even today. Both the design and the constructing techniques have greatly improved and the quality of manufacturing materials is excellent.

Dental bridges consist of two main parts :

Anchor crowns or retainer crowns

Anchor crowns hold the bridge in place and provide support for the pontics. If we imagine that a dental bridge is a bridge over a big river, the anchor crowns (along with the abutment teeth) are the pillars.

Anchor crowns are dental crowns permanently joined to the artificial tooth (or pontic). After the bridge is manufactured, the anchor crowns are definitively cemented to the abutment teeth, providing support for the whole structure.

The teeth that provide support for the retainer crowns are called abutment teeth. Generally, abutment teeth are positioned adjacent to the toothless gap.

Let's see how a dental bridge is designed : In the image above, retainer crowns are marked with blue arrows and the pontic (or false tooth) with red arrow. The adjacent teeth are the abutment teeth.

Pontic

The pontic is the part of the bridge that replaces the missing tooth (or teeth). For that reason, it is also called dummy or artificial tooth.

Normally, the pontic is placed between the abutment teeth (with the exception of the cantilever bridge) and is permanently joined to the anchor crowns.

A bridge can have one or more pontics (see image bellow) depending on the number of gaps to be restored and the number of missing teeth.

dental bridge with 1 pontic dental bridge with 2 pontics

During mastication, all chewing forces that act on the pontics are passed to the abutment teeth : the more artificial teeth, the greater the forces that act on the abutment teeth.

Each individual pontic passes the chewing forces to the abutment teeth. That is why the forces that act on the abutments are greater when the bridge has more pontics (image above).

It is not advisable to overextend the pontic. As a general rule, it is considered that a single toothless gap with more than 4 missing teeth cannot be restored with a traditional dental bridge. There are 2 reasons behind this :

 If the pontic is too extended, there is a risk of breaking during the chewing process  The forces that act on the abutments would be extreme. After a period of time, these teeth may become loose and the restoration would fail

Removes plaque and cleans between braces, bridges, implants, crowns and interdental spaces

SPECIAL BRIDGES

Implant supported bridges

These bridges are supported by dental implants inserted into the jawbone. They are widely used nowadays and are extensively discussed in the chapter about dental implants.

Bridges with special attachments

Because the bridge must be able to fit onto the abutment teeth simultaneously, the taper of the abutment teeth must match, to properly seat the bridge. This is known as requiring parallelism among the abutments.

When this is not possible, an attachment may be used, so that one of the abutments may be cemented first, and the other abutment, attached to the pontic, can then be inserted.

bridge with attachment

Dental bridge anchored with inlays Instead of retainer crowns, this bridge has two inlays attached to the pontic. The inlays will be cemented to the abutment teeth in specially prepared cavities inside the teeth.

Aesthetics is excellent but it lacks stability ; thus, it can only be used when a small restoration is designed.

dental bridge attached with inlays

Maryland bridge

This bridge is made from a metal framework where the pontic (false tooth) is attached to the metal or porcelain wings that are cemented to the two abutment teeth. This bridge is a conservative alternative to a traditional bridge.

Maryland bridge

Cantilever Bridge

In most of the cases, the pontic is placed between the abutment teeth. However, there are some clinical situations when the patient does not have teeth on both sides of the toothless gap.

Cantilever bridges are dental bridges that are designed when abutment teeth are present on only one side of the missing tooth or teeth. In these cases, the pontic is located outside the abutment teeth. cantilever bridge

When can such circumstances occur?

 when, for aesthetic reasons, it is not desirable to prepare the teeth on both sides of the breach

 when there are no teeth on one side of the breach

 when one of the abutment teeth is already supporting another prosthetic restoration that, for various reasons, cannot be replaced

Cantilever bridges involve increased, off the axis forces that will act on the abutment teeth (see image bellow).

Therefore, cantilever bridges should be carefully planned; otherwise, there is the risk of jeopardizing abutment teeth stability.

There are two types of cantilever bridges: 1. Cantilever bridge with the pontic placed towards the front of the mouth

This means that the gap is located in front (or anterior) of the abutment teeth. It is thefavourable situation, because the more we advance towards the front of the mouth, chewing pressures decrease.

cantilever bridge with 3 abutment teeth

However, chewing forces are still acting outside the axis of the bridge, hence putting additional pressures on the abutment teeth. Therefore, when designing a restoration like this it is advisable to follow certain rules:

o The pontic should have no more than 1 artificial tooth (only one tooth should be missing)

o The prudent approach is to design a cantilever bridge when the missing tooth is either apremolar or a lateral incisor and only in limited situations if other teeth are missing.

o Generally, at least two abutments are needed to support the bridge (although there are some exceptions if the abutment tooth is a strong canine or molar).

o If we need to replace a premolar or molar, we must take into consideration that chewing pressures are higher on the lower teeth.

Indications

There are two clinical situations when these restorations may be indicated:

o When, for aesthetic reasons, it is not desirable to prepare a tooth located in a visible part Observe the picture :

The first upper premolar is missing and the canine located at the front end of the gap is healthy and undamaged. For obvious aesthetic reasons we want to leave this tooth untouched.

In this situation, we can design a cantilever bridge with the second premolar and the first molar as abutments (marked with arrows). These teeth are much less visible compared to the canine.

Note: Of course, the best solution would be a single and then no teeth would have to be prepared. Although this is very true, not everyone in this world can afford such a restoration (or, in some places, there may be no technical capabilities for dental implants).

o When the anterior abutment tooth is already sustaining another prosthetic restoration that, for various reasons, cannot be replaced.

The easy and more effective way to floss ! b. Cantilever bridge with the pontic placed towards the back of the mouth

The toothless gap is located behind (or posterior) the abutment teeth. The chewing forces aremuch higher in the back part of the mouth. Consequently, the pressures that act on the abutment teeth are both very high and off the axis.

After a shorter or longer period of time, abutment teeth may become loose which may jeopardize the entire restoration. cantilever bridge with pontic towards the back of the mouth

Indications

There are few situations when these types of restorations may be indicated :

o temporary restorations

o if back teeth are missing and patients do not want (or cannot afford) more expensive restorations: removable dentures, dental implants

The lifespan and prognosis of these restorations is usually very short. With the development ofdental implants, such solutions are rarely used.

he average cost of a dental bridge can range in price based upon the number of units and the area of the world you live in. Here are some factors to be considered :

Dental insurance

The amount of the price covered by the insurance company depends on the country and the individual dental plan. Most policies will cover only a portion of the cost.

Manufacturing materials The final price largely depends on the materials used. For example, porcelain or zirconium bridges are much more expensive. Bellow, a list with the most important types of bridges ; the more expensive bridges are at the top.

1. Full porcelain bridge ; it is indicated only in particular situations (small front restorations).more

2. Zirconium and porcelain fused to zirconium bridge.more

3. Porcelain fused to gold (or other noble metals) bridge.more

4. Porcelain fused to titanium bridge.more

5. Porcelain fused to base metal alloys bridge.more

6. Full gold or full titanium bridge.more

7. Composite or metal composite bridge.more

8. Full metal (base metal) or metal acrylic bridge.more

zirconia dental bridge porcelain fused to gold dental bridge

Medical staff

High skills are required for both the dentist and to perform quality porcelain or zirconium bridges. The standards and expertise of the staff may differ from one office to another and so do the prices.

each doctor may have different professional degrees and different prices

Different countries

The price greatly depends on the geographic area the procedure is performed. Different areas of the same country may show dissimilar prices.

In addition, the prices of dental restorations in different countries are highly divergent. If you are planning to undergo a dental treatment in a foreign country, make sure to check the prices first. Bridges supported by dental implants

Because high precision is demanded, bridges supported by dental implants are more expensive than traditional bridges (supported by natural teeth). In addition, the basic surgical procedure and other adjunctive procedures are added to the final cost (see dental implants cost).

PRICE CALCULATION

There is no general rule to determine the exact cost of a dental bridge. In many countries, computer programs are used to make the calculation.

One variation (more often used) is that the final cost is based on the total number of units the bridge has. The total number of units is obtained by adding the number of retainer crowns to the number of artificial teeth (pontics).

The bridge above was designed to restore a 2 teeth gap. Total number of units is 4 : 2 abutment teeth + 2 pontics.

The final price is obtained by multiplying the number of units with the price of a single unit. The cost of a unit is the price of a dental crown manufactured from the particular material.

In the example above, if we have a zirconium bridge and the cost of a zirconium crown is 900$, the bridge total fee would be 3600$ (900 x 4).

Another variation is that the cost is based on the necessary procedures. In this variation, each procedure (medical or dental lab) has a distinct cost and the final price is obtained by adding all fees together. Generally, a computer program is used for the operation. Probably, there are many other ways to calculate the final cost depending on the geographic area. It is important to remember that, besides the cost of the dental bridge, other preliminary procedures may be needed before the preparation for the bridge can actually start.

 All decays should be correctly treated

 The teeth with apical infections should be endodonically treated

 The treatment of gingivitis and periodontal disease

 The teeth that can no longer be treated should be extracted

 Oral hygiene should be checked

The price of these procedures adds to the final cost of the dental restoration and depends on the extent and complexity of the necessary treatments.

Dental Bridge Design

The design of a dental bridge is the most important stage of the treatment. The final design is implemented after performing a thorough examination, discussing with the patient, dental technician and, sometimes, other qualified doctors.

Following this, the practitioner has to answer three questions:

 Considering the clinical situation, is the dental bridge a proper therapeutic solution ? If not, what other restoring solutions are available ?

 Which teeth will be selected as abutments ?

 How many pontics will the bridge number ? dental bridge with 2 abutment teeth and 1 pontic

Why is the design so important ?

Proper planning will increase the prognosis and lifespan of a dental bridge. It will also provide an excellent chewing comfort and protect the abutment teeth against undesirable complications.

Flush your teeth after meals and before sleeping

What happens in case of a poor design ?

An improper design takes its toll on the abutment teeth that support the bridge. Proper planning ensures a balance between the abutment teeth and the artificial teeth (or the pontics). Without this balance, abutment teeth may become loose over time.

This has extremely negative consequences on the prosthetic restoration.

 Once the abutment teeth become loose, dental bridge support becomes inadequate. After a period, the entire restoration may end up loose and eventually will have to be removed.

 After the bridge removal, the underneath abutments are still loose. If mobility exceeds certain levels, these teeth can no longer be used as abutments (for the new restoration). Following their extraction, the new clinical situation will call for a more complex therapeutic approach.

In conclusion, improper design may produce a chain reaction, which leads not only to the failure of the dental bridge but also to the complication of the entire restoration plan. proper design of a dental bridge: 2 abutment teeth sustain 1 pontic

What are the stages of dental bridge design ?

Dental bridge design is a complex operation that includes several steps. Each stage has its importance but their order may vary from doctor to doctor.

 First, it must be established whether the clinical situation is suitable for a bridgework restoration. Only certain types of edentulism can be restored with traditional bridges.

 The next step is selecting the abutment teeth. An abutment tooth must meet certain general requirements. Besides that, some classes of teeth (molars, canines) are more important in supporting a dental bridge.

 Other important factors must be considered. They may play a smaller or larger part depending on the clinical situation of each patient.

 Finally, we will make a systematization of the concepts and provide some examples. It's time to move from theory to practice.

Once the dental bridge is designed, it is time to select the manufacturing material. Various materials and combination of materials may be used for constructing a dental crown or bridge. Each has different costs and different qualities. zirconia dental bridge

porcelain fused to gold dental bridge

CONSEQUENCES OF MISSING TEETH

Following dental extractions, one or more toothless spaces will appear on the dental arches. These spaces are calledtoothless gaps, breaches or edentulous spaces.

toothless gap or edentulous space Physiological changes following teeth extractions

After a tooth extraction, the seat remaining after tooth removal will produce a series of changes. These processes occur slowly over more months (6 to 8).

First, inside the alveolar socket (where the tooth was formerly held) bone tissue begins to deposit. Over the toothless gap, the gums slowly close the extraction wound. The bone width and height gradually diminishes.

The anatomical structure that appears after the end of the healing process is called edentulous ridge.

edentulous space : the toothless space edentulous ridge : the anatomical structured located in the edentulous space

Gradually, around edentulous spaces, serious irreversible changes take place. Untreated, these conditions will have important repercussions over the health and functionality of the entire dental system.

TEETH MIGRATION

a. Migration of opposing teeth towards edentulous spaces

Opposing teeth begin to move towards the toothless gaps. This is a vertical migration until teeth reach the opposite edentulous ridge or another obstacle located on the path. vertical migration of a tooth towards the opposite toothless gap

The vertical migration can occur in two distinct ways :

o The tooth can migrate toward the opposite space along with the surrounding bone.

o The tooth can move vertically without its surrounding bone. Basically, the tooth "gets out of its alveolar socket" (image above).

b. Migration of adjacent teeth towards the breaches

Neighbouring teeth start migrating horizontally in an attempt "to close the gap". This migration can also occur in two different ways :

o The adjacent teeth are bending towards the breach. This means that only the crown of the tooth is moving while root position remains unchanged. See picture bellow. o The adjacent teeth are moving towards the space with both the root and the crown. This means that, after a period of time, teeth will change their place inside the mouth cavity.

The type of movement that occurs depends on several internal factors.

!!!Dental migrations take place only as long as the edentulous space exists. If a is manufactured, teeth migration stops.

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TEETH MIGRATION CONSEQUENCES

Shrinkage of the edentulous space

Once the toothless gap is reduced (as a result of adjacent or opposite teeth migration), a dental restoration will be very difficult to design. Artificial teeth cannot be adequately shaped because there is too little room.

excessive shrinkage of the toothless gap because of vertical teeth migration Complex procedures may be required to create an adequate space for the dental bridge. Obviously, these have a high cost and a long period of execution.

There are situations when even such operations cannot improve the clinical situation.

Dental processes are severely affected

First, aesthetics will seriously suffer especially if migrated teeth or toothless gaps are located in visible areas.

Even if teeth are located in the back of the mouth, they will not be able to perform their main function properly: chewing. The chewing process is already diminished because the number of teeth units has decreased after the dental extractions.

Moreover, teeth can migrate in totally inappropriate positions leading to severe occlusal disorders.Pronunciation will also suffer because, as we know, teeth play a major role in speech.

Migrated teeth can suffer from periodontal diseases or cavities

Because of teeth movements, the gum can retract from the teeth leaving the root naked. This area is covered by a thin layer of dental cementum, which is very sensitive to decay.

Moreover, the tooth can change its position inside the alveolar socket. As a result, the periodontal ligaments (a group of specialized fibres that attach the tooth to the bone) may be damaged leading to tooth mobility. The gum around the bending teeth may create some spaces where food particles and germs can stagnate. These areas will increase, causing the formation of periodontal pockets.

In later stages, because of the continuous pressure of the leaning tooth against the alveolar bone, the bone tissue will suffer a process of resorption, increasing tooth mobility.

!!!To prevent these complications, it is extremely important to restore toothless spaces immediately after a tooth is lost.

Edentulism is a medical condition characterized by the absence of one or more teeth. This medical condition is caused by loss of teeth.

Classification

Following teeth loss, several edentulous gaps will form on the dental arches. The length and disposition of each gap can give important information about the type of prosthesis that may be used to restore the missing teeth.

Each prosthetic restoration has certain indications and it cannot be utilized in every clinical circumstance. Therefore, only certain types of edentulism are suitable for a dental bridge restoration.

Edentulism is divided into two major classes : 1. Complete edentulism

complete edentulism

All teeth from a dental arch are missing. This particular class cannot be restored with traditional dental bridges.

Types of prosthetic devices that are indicated :

 Complete removable dentures (full dentures)

 Dental implants supported dentures (fixed or removable)

2. Partial edentulism

One or more teeth are missing but never all. Only certain forms of partial edentulism can be treated with traditional dental bridges.

Let's see how this condition is classified based on the number of missing teeth and thedisposition of the edentulous gaps.

Classification of partial edentulism

Over the years, a large variety of classifications has been proposed. One of the most familiar classifications belongs to Dr. Edward Kennedy. The classification is very simple and can be an important asset in designing dental restorations.

Depending on the position and extent of edentulous breaches, Kennedy divided partial edentulism into 4 classes.

Kennedy Class 1

Bilateral edentulous areas located posterior to the remaining natural teeth. Back teeth on both sides of the dental arch are missing. The condition is caused by the early loss of molars and / or premolars on both sides of the dental arch.

It is very difficult to restore this class with traditional dental bridges.

Types of prosthetic devices that can be used

 Fixed or removable restorations supported by dental implants

 Removable partial dentures

Kennedy Class 2

Unilateral edentulous area located posterior to the remaining natural teeth.

Posterior teeth on just one side of the dental arch are missing. This condition is consequent to the early loss of molars and / or premolars on one side of the dental arch. This class is the most difficult to treat. Cantilever bridges have a very poor prognosis. Removable partial dentures are difficult to design. Implant supported reconstructions seem to be by far the best option.

Types of prosthetic devices that are indicated

 Fixed or removable restorations supported by dental implants

 Removable partial dentures although they are difficult to design

 Cantilever bridges only in limited circumstances

Kennedy Class 3

Unilateral edentulous area with natural teeth both anterior and posterior to the area

Posterior teeth are missing (molars and/or premolars) but there are teeth on both sides of the toothless gap.

This class is very suitable for a dental bridge restoration if the breach is not overextended. Dental implants can be successfully used even if the gap is overextended.

Types of prosthetic devices that can be utilized

 Fixed dental bridges supported by natural teeth

 Fixed dental bridges supported by implants

 If the gap is overextended, partial removable dentures supported by implants or natural teeth Kennedy Class 4

A single but bilateral (crossing the midline) edentulous area located to the anterior of the remaining natural teeth.

Anterior teeth are missing (incisors) and the edentulous gap passes on both sides of the midline. In these situations, aesthetics is the most important factor.

This particular class is also suitable for a dental bridge restoration. Because of the high aesthetic demands, the use of porcelain or zirconium bridges is highly recommended. Bridges supported by dental implants are excellent solutions as well.

Types of prosthetic devices that are indicated

 Fixed dental bridges supported by natural teeth

 Fixed dental bridges supported by implants

 Removable partial dentures in certain situations

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Combined Classes

Obviously, in the everyday practice many clinical situations are various combinations between the 4 classes. This means that there are more edentulous gaps, without a standard disposition. In the picture above we have a combination of Kennedy classes 2 and 3.

In these cases, the first question is how to restore the most difficult gap. This gap belongs to the class with the lowest number.

The best approach is to design a prosthetic device that restores both gaps (even if it has 2 distinct parts). It is pointless to design, for example, just a dental bridge that restores the class 3 gap, hence leaving the posterior breach untreated.

In this particular situation, reconstructions supported by dental implants or removable partial dentures are the best options available.

Conclusions

 A traditional dental bridge is difficult to design if the back (or posterior) tooth is missing.

 Kennedy classes 3 and 4 are the most suitable for dental bridge restorations.

 Implant supported restorations can be used in almost any type of edentulism.

Edentulism classification is just one of the criteria used in designing dental bridges. It is, however, avery important one. Selecting the abutment teeth is one of the most important steps when planning for a dental bridge. Before conducting this step, it is important to determine whether the particular clinical situation is suitable for a dental bridge reconstruction (determining the type of edentulism).

Abutment teeth selection will allow the practitioner to answer two questions :

 How many abutment teeth are needed to support the bridge ?

 Which are the abutment teeth that will support the dental bridge ?

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General requirements

To be selected as an abutment, a tooth must meet certain requirements :

 Tooth should be healthy or properly treated

The tooth should not manifest any signs of pulp or apical tissue infections (such as cysts or granuloma). If the tooth shows one of these conditions, it is advisable to perform theendodontic therapy before starting tooth preparation.

If the tooth was endodontically treated in the past, it is wise to confirm on a dental radiography that the treatment was carried out correctly and there are no visible complications.

If conditions are too advanced for any conservatory treatments, the tooth must be extracted and the design of the bridge revised.

Dental X-rays :

healthy tooth ok as abutment tooth with chronic infection: dental cyst not ok as abutment

tooth with a proper endodontic treatment ok as abutment

tooth with improper endodontic therapy ; reoccurring apical infection not ok as abutment

 Tooth should not show advanced destructions

Sometimes, if tooth structure is inadequate, a is needed.

If destructions are very advanced, especially if they go beneath the gumline, it is prudent not to use the particular tooth as an abutment.

tooth with coronal destruction ; post and core indicated

post and cores definitively cemented  Tooth should not show a pronounced degree of mobility or advanced gingival recession

A certain degree of mobility is accepted especially if the bridge will be supported by many abutments.

It is advisable to evaluate the amount of bone loss around the tooth on a dental radiography. This should not exceed 1/3 of the total length of the roots.

Specific requirements

Each tooth will play a different part in supporting the dental bridge. For example, back teeth will have a more important part in supporting the bridge because of their larger size and the higher number of roots.

Some teeth are "very powerful abutments" (molars) while others are "extremely week abutments" (incisors).

"The degree of support" that each tooth will give to the dental bridge depends on many factors. These factors may be influenced by pathological conditions or age.

 Number of roots : the higher it is, the greater the tooth stability and strength

 The length and thickness of the roots : the greater it is, the higher the tooth stability inside the bone  Root divergence : the more divergent the roots, the stronger the tooth is anchored inside the bone

 Bone quality : refers to the amount and quality of the bone surrounding the tooth

According to these criteria, each tooth receives an index number that shows how much we can rely on it to support the dental bridge.

Molars

Molars are very strong teeth that have 2,3 or more roots. There are 12 molars in total: 6 upper (3 on each side, left and right) and 6 lower.

Molars have the biggest crown of all teeth. Molars are located in the back of the mouth and are extremely important abutment teeth. In their absence, it is difficult to design a reliable dental bridge (especially if the bridge is extended).

Tooth Index Description Image

First upper It is the most powerful upper tooth. It has 3 roots with 6 molar very strong bone implantation. Second The tooth is almost as strong as the first molar. It has 2 upper 6 or, more often, 3 roots. molar

It is also called the wisdom tooth. It may have 2 or more roots. It should always be checked on a dental X-ray to Third upper 4,5 or verify the number of roots and the degree of bone molar 6 implantation. It is used as an abutment only if there is no other possibility.

First lower 6 It has 2 very strong and extremely well anchored roots. molar

Second It resembles the first lower molar. It usually has 2 strong 6 lower molar roots.

Third lower 4,5 or It may have 1, 2 or more roots of various sizes. It is molar 6 used as an abutment only if there is no other possibility.

Premolars

Premolars are relatively strong teeth that can well be used as abutments, but they don't reach the strength and power of molars or canines. There are 8 premolars: 4 upper (2 on each side) and 4 lower.

They have a smaller crown than the molars and the roots are fewer and thinner. They are positioned immediately before the molars, hence the name.

Tooth Index Description Image First upper 4 It has two thin roots and average bone stability. premolar

Second Usually, it has a single root but there are times when it upper 4 has two. Otherwise, it resembles the first upper premolar premolar.

First lower It has a much stronger root and a better bone 5 premolar implantation than the upper premolars.

Second It is very similar to the first lower premolar. Sometimes lower 5 the root is thinner. premolar

Canines

Canines are strong teeth that have a long root with a very powerful bone implantation. They make the transition between front teeth (incisors) and lateral teeth (premolars and molars) and are located in the place where the dental arch curves. There are 4 canines: 2 upper and 2 lower.

Canines, along with the molars, are the most important abutment teeth.

Tooth Index Description Image

It has the longest root of all teeth. Because of its Upper 5 position, it plays an important aesthetic role and it is a canine strong abutment for the bridge as well.

Lower The root is shorter but the tooth is still very strong and 5 canine well anchored inside the bone. Lateral incisors

Lateral incisors are the smallest teeth in the mouth. They have a single root, thin and short, with a very weak bone implantation. They are 4 in number: 2 upper and 2 lower.

Regarding prosthetics, they are the weakest abutments in the mouth. Therefore, supplementary abutments are required when a lateral incisor is included in a dental bridge. They have a very important aesthetic position.

Tooth Index Description Image

Upper lateral 1 Tooth root is thin and short. Stability is very weak. incisor

Lower Strength and stability are weak. The root can be even lateral 1 thinner. incisor

Central incisors

Central incisors are larger than the laterals and they have a longer root. Apart from that, they are weaker (as abutments) than any other class of teeth. There are 4 central incisors: two upper and two lower.

Central incisors (especially the uppers) have a very pronounced aesthetic impact. Therefore, when designing a bridge that will include central incisors, aesthetics will be the most important factor to be considered.

The upper incisors have a role in the phonation process in some consonant pronunciation.

Tooth Index Description Image

Upper It has a longer and better-anchored root compared to central 2 the lateral incisor. incisor Lower central 1 It is weaker than the upper and the root is smaller. incisor

Note : Similar teeth located on the same dental arch have similar features. (E.g. right upper canine and left upper canine).

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Index calculation

As a general rule, a dental bridge is properly designed when the combined index of all abutment teeth is greater (or at least equal) than the combined index of missing teeth. If this happens, it is considered that the dental bridge is "properly supported".

To determine whether or not the abutment teeth can support a bridge, many employ Ante's rule, which states that "the root surface area of the abutment teeth has to equal or surpass that of the teeth being replaced with pontics".

Basically, Ante's rule and the index calculation (and it is possible that many dentists employ other rules) claim the same important thing : abutment teeth must be stronger than the teeth they aim to support.

Let's take an example: in the image bellow a single tooth is missing : the first lower premolar.

The abutments used : second lower premolar and the lower canine. Index calculation

Abutment teeth = 10 : second lower premolar (index 5) + the lower canine (index 5)

Missing teeth index = 5 : first lower premolar (index 5)

Abutment teeth index is greater than the index of the teeth to be replaced. That's why this particular bridge has an adequate support.

!!!All abutment teeth should meet the general requirements.

When selecting the abutment teeth, apart from the index calculation, other important factors are involved.

When designing a dental bridge, two important factors are involved :

 Edentulism type : only certain types of edentulism benefit from dental bridge restorations.

 General and specific criteria regarding the abutment teeth :

o General requirements: each abutment tooth should meet them.

o Specific criteria : each class of teeth has a different role in supporting the dental bridge.

Besides these, other important aspects should be considered.

Length of the pontic

When more teeth are missing in the same part of the mouth cavity, the "length of the pontic" (or the number of pontics) increases because more artificial teeth have to be designed. As mentioned, it is not advisable to overextend the pontic.

As a general rule, a traditional dental bridge is not indicated when more than 4 teeth are missing inside a single toothless gap. In the picture above, we have a gap of five missing teeth. It is not desirable to restore the gap with a traditional dental bridge. See why

For this particular situation, restorations supported by dental implants or removable partial dentures are more appropriate therapeutic solutions.

What happens when 3 or 4 adjacent teeth are missing ?

When a dental bridge has many pontics, the pressures that act on the abutment teeth during mastication increase. Each individual pontic will pass the chewing forces to the abutment teeth.

In the picture above, there are 3 missing teeth : 1 molar and 2 premolars. It is indicated to design 3 abutment teeth (as marked) instead of just the 2 adjacent to the gap. This way the chewing forces will be distributed between them and the dental bridge will have a better prognosis.

Conclusions

1. When more than 4 teeth are missing inside a single toothless gap, a traditional dental bridge is not indicated as a therapeutic solution. 2. If more than 2 teeth are missing (but less than 5) inside a single gap, it is wise to include more abutment teeth.

Cantilever bridges

Sometimes, for certain aesthetic or clinical reasons, dentists are forced to manufacture bridges that have dental support on only one side of the toothless gap. These restorations are called cantilever bridges. In these cases, the pontic is located outside the abutment teeth.

cantilever bridge with 3 abutments

Dental occlusion

More technically, the dental occlusion (or the bite) is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as it occur during chewing or at rest.

Static occlusion

Static occlusion refers to contacts between teeth when the jaw is closed and stationary.

In this position, the practitioner must determine whether there is enough space to shape the artificial teeth properly. An edentulous space may reduce its vertical dimensions because of opposite teeth migration (also known as overeruption). the vertical dimension of the toothless gap is reduced because of opposite teeth migration

Such situations call for preliminary procedures that aim to increase the height of the toothless gap and create adequate space for the dental bridge.

Dynamic occlusion

Dynamic occlusion refers to occlusal contacts made when the jaw is moving, such as when chewing.

It is significant to determine the intensity of chewing forces that will act on a dental bridge. This may depend on various factors :

 Chewing forces are greater if natural teeth are opposite to the designed bridge (especially if they are healthy and with a strong bone implantation).

Chewing forces decrease if a dental restoration (crown, bridge, full denture) was previously manufactured on the opposite arch. In case of complete dentures, these forces are the lowest.

 Chewing forces are higher on the lower arch especially in the back part.

 If no teeth (and no restorations either) are present on the opposite arch, a dental restoration has to be designed for the opposite arch too. Otherwise, the chewing process will be severely affected.

 There are conditions that may lead to various occlusal problems : bruxism, nervous disorders etc. The treatment of these conditions should be conducted before designing the bridge.

What is the normal conduct after examining the occlusion ? If it is considered that additional forces will act on the bridge, the number of abutment teeth will be increased. If chewing forces will be normal or lower, the number of abutment teeth will remain the same (it will not be decreased).

Easily threads floss under bridges, orthodontic appliances, implants and between connected crowns !

The aesthetic and degree of destruction criterion

It is a simple criterion : when two teeth meet all abutment requirements, the following selection can still be made :

 The tooth with a more pronounced aesthetic position will remain unprepared (assuming that the tooth is healthy and not damaged or just minimally damaged).

 The tooth with a greater degree of damage (coronary destructions, large fillings, discoloration, enamel defects) will be prepared as abutment tooth.

Complete bridge

It is an unconventional name and refers to a bridge that reconstructs an entire dental arch. In these situations, all teeth from the arch are prepared as abutments.

complete porcelain bridge Conceiving a reconstruction like this is an important process. Theoretically, a complete bridge can be designed using only 4 teeth as abutments, but they must be the first molars (left and right) and the two canines. However, the more prudent approach is to include more abutments.

Edentulism types that do not require dental restorations

There are situations when the absence of a tooth doesn't need a dental restoration:

 The absence of the third molar (wisdom tooth) : it has a negligible role in mastication

 The absence of the second molar : needs restoration only if the opposite second molar is present on the arch

!!! Do not confuse the necessity of replacing a tooth with the possibility of using the same tooth as abutment.

For example, if the third molar is missing, no restoration is needed. But the same tooth may be used as an abutment for dental bridges that restore other missing teeth.

LINICAL SITUATIONS

Let's see some practical examples. We illustrate with a picture the clinical condition, and we will try to answer each of the points listed above.

1. A traditional dental bridge Case description

Upper arch

Number of edentulous (toothless) gaps : 1

Missing teeth : 2 -- the first and second upper premolars on the right side of the patient

Remaining teeth : all the other teeth are present on the arch see questions

Dental bridge design

1. It is a Kennedy class 3 edentulism that can be treated with dental bridges.

2. There is 1 toothless gap with 2 missing teeth. The gap does not exceed 3 units (or 3 missing teeth) , so the pontic is not overextended.

3. The adjacent teeth meet the general requirements for abutment teeth (see note).

4. Total index of missing teeth is 8 (first upper premolar = 4 + second upper premolar = 4).

5. Total index of bordering teeth is 11 (first upper molar = 6 + upper canine = 5). The situation isfavorable because it is greater than the index of the missing teeth.

6. The gap has less than 3 missing teeth.

7. It is not the case for a cantilever bridge.

8. Occlusion is normal. It is not expected that chewing forces will be over the normal limit (see note). 9. No need for additional abutments.

10. No need for additional abutments.

Note : We have only assumed the answer to questions 3 and 8 to continue the presentation. These questions can be answered only after a complete examination. see questions

Therapeutic solution

Dental bridge with 4 units (2 abutments + 2 artificial teeth). Abutments will be : the first upper molarand the upper canine. It is a bridge with a very good prognosis ; both molar and canine are excellent abutment teeth.

2. Cantilever bridge Case description

Upper arch

Number of edentulous (toothless) gaps : 2

Missing teeth : 2 -- the first upper premolar and the first upper molar on the left side of the patient

Remaining teeth : all the other teeth are present on the arch see questions

Dental bridge design

1. It is a Kennedy class 3 edentulism with 2 toothless gaps that can be restored using dental bridges.

2. There are 2 toothless gaps both having 1 missing tooth. The gaps do not exceed 3 units (or 3 missing teeth) , so the pontics will not be overextended.

3. Adjacent teeth meet general requirements. (see note).

4. Total index of the missing teeth is 10 (first upper premolar = 4 + first upper molar = 6).

5. Total index of adjacent teeth is 15 (second upper molar premolar = 6 + second upper premolar = 4 + upper canine = 5). The situation is favorable because it is greater than the index of the missing teeth.

6. All gaps have less than 3 missing teeth. 7. There is a possibility for a cantilever bridge. For aesthetic reasons, we could let the canine unprepared. In this case, to ensure proper support, it is advisable to include the third upper molar as abutment tooth.

8. Occlusion is normal. It is not expected that the chewing will be over the normal limit (see note).

9. Third upper molar is an additional abutment and it meets the general requirements (see note).

10. The additional abutment (the wisdom tooth) has the index 4, 5 or 6. Let's suppose the index is 4 (we think at the worst scenario). Total index of the abutment teeth would be 13. It is higher than the total index of the missing teeth so situation is favorable.

Note : We have only assumed the answer to questions 3, 8 and 9 to continue the presentation. These questions can be answered only after a complete examination. see questions

Therapeutic solution

There are two possible therapeutic solutions. Selection depends on the aesthetic demands.

Solution 1

Dental bridge with 2 pontics and 3 abutment teeth : second upper molar, second upper premolarand the upper canine. Solution 2

Cantilever dental bridge with 2 pontics : one normal and the cantilever. The abutments will be: third upper molar, second upper molar and second upper premolar. For aesthetic reasons, the canine will remain unprepared.

3. Extended dental bridge with several toothless gaps

Case description

Lower arch Number of edentulous breaches : 2

Missing teeth : 5 -- first molar, first and second premolars from the right side and both lower central incisors

Remaining teeth : both wisdom teeth are absent, all other teeth are present on the arch. see questions

Bridge design

1. It is a combined class of edentulism : Kennedy class 3 and 4. Traditional dental bridges may be a therapeutic solution.

2. There are 2 large toothless gaps: one has a length of 3 units (3 teeth are missing), the other 2 units. Neither of the gaps exceeds 3 units so pontics are not overextended.

3. Adjacent teeth meet general requirements for abutments (see note).

4. Total index of the missing teeth is 18 (first lower molar = 6 + second lower premolar = 5 + first lower premolar = 5 + lower central incisor= 1 + lower central incisor = 1).

5. Total index of the bordering teeth is 13 (second lower molar = 6 + lower canine = 5 + lower lateral incisor = 1 + lower lateral incisor lower = 1) (both lateral incisors are adjacent teeth).

Clinical situation is unfavorable because the index is less than the index of the missing teeth. We need additional abutments. The question is : how many ?

6. We have a 3 teeth toothless gap. The missing teeth are strong and chewing forces in that area are very high. The front gap raises high aesthetic demands. For both reasons it is wise to consider more abutment teeth.

7. It is not the case for a cantilever bridge.

8. Because we are talking about the lower arch, the chewing pressures are higher (especially in the back area). It is advisable to include more abutment teeth.

9. The bridge needs additional abutments. There are two strong abutments available on the left side of the arch: the lower canine and first premolar. Both teeth meet general requirements (see note). 10. Both teeth have the index 5. If we select only the canine, total index would be 18, equal to missing teeth index.

Both the 6 and the 8 criteria indicate the use of more abutment teeth. Therefore, it is prudentto include the left premolar as an abutment tooth.

In everyday practice, there are many situations when the bridge is designed with fewer abutments. These decisions can only be made after a thorough examination

Note : We have only assumed the answer to questions 3 and 9 to continue the presentation. These questions can be answered only after a complete examination. see questions

Therapeutic solution

Dental bridge with 2 pontics and a total of 5 artificial teeth. The bridge will have six abutments: the second molar, canine and lateral incisor on the right and the lateral incisor, canine and first premolar on the left side.

Dental ceramics or porcelain is the best aesthetic materialavailable at the moment. Porcelain reconstructions can be utilized in almost any clinical situation : dental crowns, small or extended dental bridges, removable partial dentures or dental implant restorations. Porcelain is superior to any other aesthetic material used in dentistry today because it has great aesthetic features (greater shade range, translucency very close to natural teeth) and, at the same time, an excellent resistance to chewing forces.

PORCELAIN

porcelain crowns on the 2 central incisors ; notice the outstanding aesthetics

Clinically proven formula made exclusively for porcelain veneers,crowns and bonding

TYPES OF PORCELAIN RESTORATIONS a. Porcelain fused to metal

Porcelain fused to metal reconstructions are widely used in dentistry. Porcelain fused to metal restorations have a metal shell on which porcelain is fused in a high heat oven. porcelain fused to metal bridge

Structure

 Metal frame

The metal frame provides strong compression and tensile strength as well as proper support for the porcelain that will be fused on it. It has a reduce thickness and it perfectly fits theprepared teeth.

porcelain crown and bridge metal frame metal frame inside the mouth cavity

The metal alloys used in combination with dental ceramics are specific. Their composition allows a powerful chemical bond with the porcelain layer fused on top, hence greatly increasing the strength of the connection between metal and porcelain.

This is one of the most important advantages of porcelain fused to metal. The metal- composite or metal-polymer connections are significantly inferior as the aesthetic material is held in place only in specially prepared areas on the metal frame.

the metal frame for porcelain restorations has a smooth surface porcelain is held in place by strong chemical bonds

the metal frame for composite or acrylic restorations has specially prepared areas on it

The quality and price of porcelain fused to metal restorations largely depends on the type of metal alloy used for manufacturing the frame. 1. Base metal alloys

These types of alloys have only base metals in their composition. The most common base metals used in dentistry are titanium, chromium, nickel, aluminium, iron or tin.

Although they don't have the same attributes (with the exception of titanium) as noble metal alloys (gold, silver, palladium), porcelain fused to base metal alloys reconstructions are strong enough, durable, aesthetics are good and the price reasonable.

Various types of reconstructions can be performed : dental crowns, small or larger dental bridges and different types of prostheses supported by dental implants.

2. Titanium alloys

Titanium alloys are special kind of base metal alloys with superior qualities. Because of this, titanium alloys are very close to noble alloys.

They are widely used in dentistry mainly for dental implants but also for various types of prosthetic devices. The price is higher although it usually doesn't reach the cost of gold alloys based restorations.

3. Gold alloys

Although referred to as a gold alloy, this types of metal alloys are actually composed of many different types of elements, including gold, platinum, palladium, silver, copper and tin.

The first four elements listed are noble metals, while the last two listed are base or non noble metals. The gold alloy is of better quality when it is high in noble content.

As the rest of the alloys, gold alloy develops very strong chemical bonds with the ceramic layer.

o Dental gold is an alloy that is used only in dentistry. o Gold alloys used for ceramic restorations have a specific composition.

o Gold alloys used for other types of prosthetic devices have a different composition.

porcelain fused to gold dental bridge

Why is gold alloy superior ?

o Gold alloy never corrodes. What does this mean ? Some metal alloys, under the influence of saliva, may suffer in time a phenomenon called corrosion.

This may lead to the appearance of an unsightly grey coloration in the upper part of the dental crown (see image).

o Gold alloy has superior strength and resistance. The main advantage is that gold alloys can be manufactured at a very low thickness and still preserve strength and resistance.

o Gold alloys are lighter than base metal alloys (with the exception of titanium).

o Gold alloys are very well tolerated by the body and do not produce any allergic reactions. more details about metal frame fabrication at the dental lab  Porcelain layer

Porcelain can cover the metal core on all sides, living no parts of the metal visible. Another variation is that crowns are made with a partial that covers only the aspects of the crown that are visible while the remaining surfaces of the crown are bare metal.

porcelain covers all sides of the metal frame

crown with a partial veneer

The first of the two variations has superior aesthetics.

The thickness of the ceramic layer is 1.5 to 2 mm depending on the area of the tooth. It has a very good resistance to chewing forces and great aesthetics.

There is a huge range of colors, with the possibility of combining them. Consequently, porcelain will give the crown a tooth-like appearance and can be color matched to the adjacent teeth or gingivae. Moreover, porcelain has a translucency that resembles the enamel, which highly improves its appearance.

porcelain crown (on center tooth) color matched to the adjacent teeth

Does dental ceramic crack when eating hot food ?

Porcelain is not influenced by temperature variations. It does not crack after eating or drinking higher temperature products.

Ceramics are fused in special ovens at temperatures that can rise over 1000 degrees Celsius (1832 Fahrenheit). It is obvious that temperatures like that will never be reached inside the mouth cavity.

Why does porcelain chip when biting on harder pieces of food ?

Porcelain is not so resistant to certain types of forces. These are especially high intensity forces acting suddenly and off the axis.

It is advisable not to bite on extremely harsh pieces of food and not to overstress the ceramic restorations.

Dental ceramics means the same as ?

Yes. Both terms describe the same thing. We will use both forms in our presentation. !!!Porcelain is a very good and strong dental material. However, it is only an attempt to replace natural teeth. No dental restoration can ever achieve the strength and resistance of natural teeth.

Full Metal

As their name indicates, these restorations consist entirely of asingle piece of alloy.

Metals used in crowns and bridges include gold alloy, other noble alloys (for example palladium) or a base-metal alloy (for example nickel, chromium or titanium). Stainless steel or aluminium- prefabricated crowns are used as temporary crowns.

Compared with other crown types, less tooth structure needs to be removed with metal crowns, and tooth wear to opposing teeth is kept to a minimum. Metal crowns and metal bridges withstand biting and chewing forces well, rarely chip or break and probably last the longest in terms of wear down.

base metal crown

full metal bridge

full gold crown

stainless steel crown

The main disadvantage of full metal restorations is their poor aesthetics, the metallic color being the main drawback. Indications

 Metal crowns and bridges are a good choice for out-of-sight back teeth (molars, sometimes premolars).

 To prevent the detachment of acrylic or composite veneers on less visible molars, a full metal crown may be a better choice than a metal acrylic one.

 Although porcelain fused to metal seems to be a better solution, full gold or full titanium restorations are still widely used on posterior teeth.

1. Full gold crowns and bridges

Gold is a superior dental alloy utilized for various types of indirect restorations : porcelain fused to gold crowns and bridges, full gold crowns and bridges, dental implant abutments, removable partial dentures or inlays.

The gold alloy is composed of many different types of elements : noble metals : gold, platinum, palladium, silver, and base metals : copper, tin and others. A proper gold alloy should contain at least 60% noble metals.

full gold crown

Advantages of gold alloys

 Gold alloy never corrodes. Some metal alloys, under the influence of saliva, may suffer in time a phenomenon called corrosion. This may lead to the appearance of an unsightly grey coloration in the upper part of the dental crown.  Gold alloy has superior strength and resistance. The main advantage is that gold alloys can be manufactured at a very low thickness and still preserve strength and resistance. The benefit is that less tooth structure needs to be removed.

 Gold alloys are lighter than base metal alloys (with the exception of titanium).

 Gold alloys are very well tolerated by the body and do not produce any allergic reactions.

Besides gold alloys, other types of noble metal alloys are available. For example, the palladium alloy contains palladium, gold, silver and other base metals.

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2. Full titanium crowns and bridges

The use of titanium alloys for medical and dental applications has increased dramatically in recent years.

Many of titanium's physical and mechanical properties make it desirable as a material for dental implants and prostheses. The strength and rigidity of titanium are comparable to those of other noble or high noble alloys used in dentistry.

full titanium bridge.

In dentistry, titanium is used for many purposes : dental implants (main purpose), base material for porcelain restorations, full metal restorations and others.

Although the cost of titanium restorations is high, it doesn't usually reach the price of gold reconstructions. 3. Base metal alloys restorations

Full base metal restorations are the less expensive reconstructions. They have good strength and durability, although inferior to gold or titanium alloys.

Various metals can be used : nickel, chromium, iron etc. Stainless steel or aluminium are mainly used for temporary crowns.

They are a good choice for out-of-sight molars when patients cannot afford more expensive prostheses.

ACRYLIC

Acrylic resins restorations have been widely used in dentistry in the past but since higher quality materials have emerged, they have lost ground. Although they are still used in certain parts of the world as permanent restorations, their main indication is fortemporary prosthetic devices.

The main advantage is their low cost and easy manufacturing but they are significantly inferior to both porcelain and dental composite.

metal acrylic dental bridge metal acrylic dental crown

When permanent restorations are designed, they will always have a metal shell on which acrylic is placed in specially prepared areas. Most of the times, acrylic will cover only visible areas of the crown and it cannot be placed on the chewing side of the tooth because of its low resistance.

Indications

 When the cost of a porcelain (or composite) restoration is too high for the patient. To overcome the negative consequences of teeth loss, it is very important to restore the edentulous spaces as soon as possible.

This is why an acrylic restoration is better than nothing, at least until the patient will have the financial situation for a superior prosthesis.

 Limited indications for the following cases : elderly persons, people with other acrylic restorations which they don't want to change, very poor persons.

 Temporary crowns or other temporary restorations. It is the main indication of acrylic restorations. In this case, the temporary crown doesn't need a metal shell because its life span is very short (until the definitive restoration is completed).

Structure

 Metal frame The metal shell can be constructed from various types of metal alloys (chromium/nickel, chromium/cobalt etc.). Normally, base metal alloys are utilized but it is possible to use noble alloys as well.

metal dots

Basically, the metal frame covers the entire tooth ; on the visible part, it has a special "window" which is carved inside the metal shell (see image bellow). The acrylic is placed inside this window and is held in place by small metal "dots" or "scales".

Unlike porcelain, acrylic does not bind chemically with the metal, which leads to a less strengthful connection. This may cause the breaking or separation of acrylic veneers.

see lab procedure

 Acrylic resin

Acrylic resins are plastic materials that are processed by means of polymerization in special furnaces at 150-200 degrees Celsius (300-400 Fahrenheit).

Most often, the crowns are made with a partial acrylic veneer that covers only the aspects of the crown that are visible while the rest of the crown remains bare metal. It is not indicated to place acrylic resins on the occlusal side of teeth because of the low resistance. dental crown with partial acrylic veneer

Features

o Weak resistance and durability

o Smaller range of shades and a lower possibility of combining them, hence inferior aesthetics

o No translucency

o Weak connection with the metal part. This may lead to the detachment of acrylic veneers

o Normally, it has a low cost

see acrylic resins bulidup at the dental lab

Conclusions

 Definitive acrylic restorations have limited indications nowadays. They are normally utilized when patients cannot afford more expensive (and superior) dental restorations : zirconia, porcelain etc.

 Temporary acrylic restorations are widely used. Temporary crowns are usually manufactured without a metal frame and their main function is to protect the prepared teeth until the definitive restoration is completed.

COMPOSITE Dental composite resins are types of synthetic resins, which are used in dentistry as restorative materials. Today's composite materials have many important advantages.

ADVANTAGES

Bonding

Dental composite chemically bonds to tooth structure. This strengthens the tooth's structure and restores its original physical integrity. Because composite are "glued" to the tooth, less healthy tooth needs to be removed for a composite restoration.

Bonding technique:

1. Etching -- is performed with phosphoric acid that will produce enamel and dentin irregularities ranging from 5-30 micrometers in depth.

2. Bonding -- a specific bonding agent is used for the operation. The bonding agent is supplied together with the composite. The bonding agent will secure a micromechanical bond to the tooth allowing good adhesion of the restoration to the tooth.

3. The composite is finally placed and light cured.

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Clinical use

The bonding feature of composite resins is an important asset for various types of restorations :

 Fillings The fact that composite fillings are glued (bonded) to the tooth means that unlike amalgam fillings, there is no need for creating retentive features destroying healthy tooth.

 Adhesive composite bridges

In this case, a composite false tooth is attached to the neighbouring teeth with the bonding procedure. The main advantage of this method is that there is no grinding of neighbouring teeth.

adhesive composite bridge

 Inlays

A composite inlay is an indirect restoration (constructed at the dental lab) that will be bondedinside the prepared tooth cavity which will strengthen the entire tooth structure.

 Veneers

A composite veneer may be directly placed (built-up in the mouth), or indirectly fabricated by a dental technician in a dental laboratory, and later bonded to the tooth.

more about indirect composite restorations

Aesthetics

The main advantage of a direct dental composite over traditional materials such as amalgam is improved aesthetics. Composites can be in a wide range of tooth colors allowing near invisible restoration of teeth. Composite fillings can be closely matched to the color of existing teeth. before : amalgam fillings

after : composite fillings

Composite vs Porcelain

When indirect restorations are involved, especially large ones, composite is the least ideal solution in terms of strength and durability.

Even if today's composite materials can provide a life-like, beautiful appearance and can last for a long time, porcelain is more resistance to stain and chipping, it does not wear under pressure, is color stable and better aesthetically.

However, composite restorations are normally cheaper.

Clinically proven formula made exclusively for porcelain veneers,crowns and bonding

DIRECT AND INDIRECT DENTAL COMPOSITE

Dental composite can be used in 2 different ways:

a. Direct dental composites

curing light

Direct dental composites are placed by the dentist in a clinical setting. Polymerization is accomplished typically with a hand held curing light that emits specific wavelengths to initiate the polymerization process. Direct dental composites can be used for filling cavities or small gaps between teeth, minor reshaping of teeth, to make teeth look longer or to change the shape or color of teeth.

composite filling

b. Indirect dental composites

Indirect composites are cured outside the mouth, in processing units capable of delivering higher intensities and levels of energy than hand held lights can.

Indirect composites are cured for longer times and have higher levels and depths of cure than direct composites.

Indications

Indirect dental composites can be used for:

o Filling teeth cavities with the indirect technique : inlays and/or onlays

o Filling gaps (diastemas) between teeth

o Reshaping of teeth

o Full or partial crowns on single teeth

o Bridges spanning 2-3 teeth and adhesive bridges

o Veneers Composite dental crowns

Composite crowns are not as durable as gold, zirconia or porcelain crowns and do need to be replaced more often. Composite crowns can have a metal shell but there are situations when it is possible to manufacture full composite crowns.

Metal-composite crowns are often made with a partial veneer that covers only the aspects of the crown that are visible. When aesthetic demands are high, it is possible to cover all sides of the crown with composite.

full composite crown

metal composite crowns with partial veneer and fully covered

Indications

o Patients who cannot afford more expensive types of crowns

o Patients with extreme metal sensitivities who are also unable to tolerate full porcelain (very rare)

o Temporaries or as an interim option for patients with a high decay rate Metal composite dental bridges

Similar to crowns, composite dental bridges can have a metal shell on which composite is placed, normally in the form of veneers that cover the visible parts.

Metal composite bridges have a similar structure to the crowns and are usually indicated when patients cannot afford or tolerate more expensive solutions.

metal composite bridge with partial veneers

Adhesive composite bridges

Adhesive composite bridges are utilized when a single tooth (normally front tooth) is missing. The procedure involves attaching a false composite tooth, that is modelled either by the dentist at the office or by the dental technician, to neighbouring teeth with the bonding technique.

The main advantage of this method is that there is no grinding of neighbouring teeth. Therefore, the neighbouring teeth are not damaged. This means that the patient can at any time revert to their natural teeth. Sometimes the composite bridge can be fibre reinforced.

A resin-bonded bridge looks and functions better than a removable denture but isn't as strong as fixed bridgework and typically doesn't function or last nearly as long as dental implants.

Indications

o When there is not enough bone and implants cannot be inserted

o When the grinding and damaging of neighbouring teeth for a normal dental bridge is not accepted by the patient

o When the cost of alternative treatments is too high for the patient

Inlays

An inlay is an indirect restoration consisting of a solid substance (as gold, porcelain or composite resin) fitted to a cavity in a tooth and cemented into place. Unlike gold and porcelain, composite inlays are attached inside cavities with the bonding technique. dental composite inlays on the dental cast

Although composite inlays are better held in place because of the bonding technique, they are inferior to gold and porcelain inlays in strength, durability and life span.

Veneers

A veneer is a thin layer of material placed over a tooth, either to improve the aesthetics of a tooth or to protect the tooth's surface from damage. There are two main types of material used to fabricate a veneer: composite and dental porcelain.

A composite veneer may be directly placed (built-up in the mouth), or indirectly fabricated by a dental technician in a dental laboratory. The composite veneer will be fixed in place with the bonding technique.

veneer

Porcelain veneers are more resistance to stain and chipping, more durable and are better aesthetically. TEMPORARY CROWN

A temporary crown is a provisional, short-term restoration cemented in place with a soft temporary dental cement until the definitive restoration is completed.

temporary crown

temporary crown inside mouth cavity

Main functions

 Partially restores aesthetics by disguising the prepared teeth to some degree. This is especially important if teeth are located in visible parts of the mouth.

 Protects the prepared teeth (for example from temperature variations) and prevents damage to the periodontal tissues (gums).

 Partially restores the chewing function.

Features

Temporary crowns are usually constructed from plastic-like materials (acrylic) or composite resins. These crowns don't need any metal frame because they have a short life-span. It is possible to manufacture temporary crowns from stainless steel or aluminium. Usually, these types are prefabricated.

stainless steel temporary crown

If fabricated from acrylic resins or composite, temporary crowns have a close color to the adjacent teeth and low resistance to chewing. There is no need for a high resistance because they stay in place only for a short time.

How are temporary crowns manufactured ?

For best results, temporary crowns should be constructed and cemented immediately after teeth preparation. There are two ways to manufacture a temporary crown :

1. Direct method

The temporary crown material is shaped by the dentist to form a tooth shape. For this operation, the dentist uses a specific crown kit. The crown kit contains prefabricated crown forms for incisors, canines, premolars and molars.

These crown forms are manufactured from various materials : polycarbonate, acrylic, transparent plastic and sometimes aluminium. crown forms for molars

Technique

 After tooth preparation, the dentist selects from the kit a crown form that best fits the prepared tooth.

 The crown form is adjusted on the prepared tooth.

transparent plastic crown form adjustment

polycarbonate crown form adjustment

 The temporary crown material is placed inside the crown. Usually, this material is supplied together with the crown kit.

The material has several shades and a relatively short curing time.  The crown form with the temporary material inside is repositioned on the prepared tooth. The temporary crown is shaped between the inside walls of the crown form and the outside walls of the prepared tooth.

 After temporary material sets, the crown is removed from the tooth and the temporary material (which by now is hardened) is removed from the crown form. Further adjustments can be made if necessary.

The temporary crown is adjusted to fit in the bite and. At end, the final polish is performed.

temporary crown fitting

 The crown is cemented in place with a soft temporary cement. This allows for easy removal when fitting the definitive restoration. temporary crown after cementation

2. Indirect method

This method involves the dental laboratory. The crown is manufactured by the dental technician and sent to the dental office for temporary cementation.

A do-it-yourself temporary tooth replacement product

Technique

 After teeth preparation, the dentist makes a . It is possible to make an additional impression for the temporary crown but more often the same impression is used. The impression is sent to the dental lab.

 The technician pours fluid gypsum inside the impression to create the dental cast. Then, according to the instructions received from the practice, the dental technician constructs the temporary crown on the dental cast.

 The crown can be constructed using various techniques some of them similar to the direct method described above (but performed by the dental technician on the dental cast). The materials used are dental acrylic or composite.

 After modelling is over, the crown is placed in specific processing units for polymerization. At the end, the technician polishes the crown for a smooth surface. The whole process takes 1- 2 hours, so the temporary crown can be fixed during the same day.

Other temporary restorations

Besides temporary crowns, other types of temporary restorations can be manufactured.

 Temporary bridges : indicated in cases with extended restorations but they are rarely used. Usually, in such situations, temporary crowns are constructed on all abutment teeth.

If aesthetic demands are high and it is estimated that the restoration will require a longer time to completion, provisional removable dentures are preferred.  Provisional removable dentures : are constructed when large restorations require a long period of execution. For example, in case of dental implants the time that is needed may be up to 6 months.

After the medical examination, the dentist will consult with the patient to determine the exact type of temporary restoration that will be manufactured.