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What are fillings?
Fillings occur when a dentist must ‘fill in’ a damaged part, or cavity, in one of your teeth. The commonest cause of tooth decay is bacterial infection, caused by hydrolysis of food particles lodged in the teeth which produces acid. The dentist must clear away any affected area and fill the remaining gap.
As well as repairing rotten surfaces, fillings can repair teeth that are broken or cracked, or have been gradually worn by bad habits such as teeth grinding or gnawing nails.
The main steps in creating fillings
Working on damaged tooth tissue will be a potentially painful experience for the patient. A dentist’s first step will to be to apply a local anesthetic to numb the area around the affected tooth.
Several factors will impact the particular instrument your dentist chooses for the task. These include level of training, general comfort level, and the range of dental equipment that is to hand. As well as this, the dentist will consider the location of the tooth within your mouth, as well as exactly how severe the decay is.
After the area has been frozen, the dentist can begin scraping away the infected tissue. During this process he will keep examining the tooth to check how well this removal is proceeding. Once he is satisfied that the decay has been eradicated the next stage is to prepare the space that must now be filled. This involves ensuring the cavity is thoroughly cleansed of bacteria and any other foreign matter. When the affected region is around the root of the tooth, it might be in order for a liner to be put in place. This will consist of a suitable material such as glass ionomer. This is a composite resin that will protect the tooth’s nerve. The cavity is then filled completely and after this has been accomplished, the final step is for the filling to be polished.
There are different types of filling. For patients who began visiting dentists several decades ago, filled teeth will almost certainly be silver in colour. Tooth-coloured fillings are now far more favoured as they are almost invisible. With the latter, once the decay has been removed from the cavity and the gap cleansed, the tooth-coloured material is added in a series of layers. The dentist applies a special light source that hardens each layer as it is applied. When this process concludes, the dentist can then shape the composite material to achieve the desired result, trimming away any excess, then polishing.
Varieties of metal filling
The types of material that can be used to fill teeth are diverse. Metal is particularly popular, the commonest examples being gold or a silver amalgam (comprising mercury combined with tin, copper, zinc and silver itself). Porcelain is also used, as well as tooth-coloured material (such as glass or plastic). These are also known as composite resin fillings. Many factors will determine which particular material your dentist favours. Again, the location and extent of the decay is all-important. Economic consideration may well be made by some dentists, such as whether or not you are covered by insurance.
There are several advantages to cast gold fillings. They are very durable compared to other materials. Fillings will last for anything up to 15 years without any corrosion. Gold fillings are tough and able to withstand a lot of chewing. Many patients find that gold is a warmer colouration than silver amalgam fillings.
Amongst the disadvantages is the cost.Gold fillings are much more expensive than their amalgam counterparts. The placement operation requires two visits. In addition, there can be a likelihood of galvanic shock: a gold fillings placed beside silver amalgam can instigate a sharp pain, caused when the different metals react with saliva to create a small electric current. Although rare, this is nonetheless unpleasant. Where some patients do find gold fillings more aesthetically pleasing, others find the very prominence of gold fillings to be a negative factor.
Silver amalgam fillings are equally durable; like gold fillings they are far hardier than composite fillings. Again, they can cope with strong chewing activity. They are also less expensive than composites.
But there are a lot of disadvantages. Silver amalgam will contrast starkly with natural tooth colour; in fact, these fillings can appear to be grey against the surrounding teeth. When exposed to hot or cold liquids, amalgam material will expand and then contract to a greater extent than the surrounding tissue, leading to a higher incidence of fractures. More of the actual tooth needs to be removed to create space to cope with the filling. As well as this, around one percent of patients can experience an allergic reaction to the mercury that exists in amalgams.
The most obvious selling point of tooth-coloured fillings is the fact they can be so closely matched to the colour of the rest of your teeth. Because they will blend in, effectively becoming invisible to onlookers, these are popular for fillings required in front teeth.
These composite fillings will bond very well to tooth structure and are extremely versatile. As well as providing filling material they can be used to repair chipped or damaged teeth.
These fillings also require less of the tooth tissue to be removed during the preparation process, compared to gold or silver amalgam fillings.
One of the main disadvantages is the fact these fillings do not last as long as amalgams – they will normally last for around five years, whereas metal fillings can last three times as long. They will not withstand the pressure of chewing to the same extent, especially if they have been deployed over large cavities.
Composite material takes much longer to put into place than metal fillings, meaning your trip to the dentist might last 20 minutes longer than if you were being fitted with silver amalgam fillings. When these fillings are being used for inlays more than one visit will be necessary. In addition, composite fillings can often chip from the tooth, meaning that further visits will be required.
Expense is another considerable drawback, as these fillings are likely to set you back around double what you would expect to pay for amalgam material.
Other forms of composite fillings
Ceramic fillings are normally constructed from porcelain. More resistant to staining than composite material, they were also much more abrasive. Ceramic is long-lasting – anything up to 15 years – but can be as costly as gold.
Glass ionomer fillings are made from acrylic and glass. This type of filling is most commonly used for fillings that are required below the gum line, or for fillings in young children. These fillings release fluoride, which will help to protect teeth from further decay.
Glass ionomer fillings are not as strong as composite filings, more prone to wear and tear, and will only last for five years or less.
Although similar to tooth-coloured fillings, indirect fillings are made up in a dental laboratory. Two visits are required before they are placed into the patient’s mouth. These types of filling will be used when too much tooth structure has been damaged to allow for amalgam or composite fillings, although not to the extent that a crown would be required.
The initial visit would deal with decayed tissue or any previously applied filling. The dentist would then take an impression of the tooth to record the shape. This would be send to the dental laboratory where it would be used as the template for the indirect filling. The tooth would be protected with a temporary filling to keep the vulnerable tooth protected while the restoration is being organized. At the second visit, the temporary filling would be removed prior to the dentist placing the indirect filling into place. If this covers the cavity satisfactorily, the indirect filling will be cemented into position.
These indirect fillings take two formats – inlays and outlays. The former are similar to any other type of filling, although the work lies within the ‘bumps’ on the tooth surface (the chewing area). The latter are more expensive, and will cover one or more bumps. These types of indirect fillings are sometimes referred to as partial crowns.
Indirect fillings are far more durable than other types of fillings, with a longevity of anything up to 30 years. The material they can be made from includes tooth-colored composite resin, gold or porcelain. Although indirect fillings will weaken tooth structure, they do this to a far lesser extent than other fillings.
Direct inlays and outlays follow the same process as indirect fillings, although these are prepared in the dental surgery and can be placed in one visit. The decision on which type of outlay to use will depend on the extent of the damage to the tooth structure, and whether or not there are any cosmetic considerations.
A dentist will apply temporary fillings in those cases where more than one appointment is necessary. This is the case when gold fillings are being fitted, or when indirect fillings are required. Root canal treatment will require temporary fillings. They will also be used to help a nerve to settle when the pulp has become irritated. Temporary fillings can counter dental emergencies, such as severe toothache.
The important issue with these fillings is that they are temporary and should only ever be used as a short-term dental solution. Most of these fillings will fracture or wear out within about a month of being fitted. You should always make a follow-up appointment with your dentist to have any temporary filling replaced with a permanent one, otherwise your mouth could well become infected.
Medical concerns with silver fillings
In recent years questions have been asked about the safety of silver-coloured amalgam fillings, due to their mercury content. Mercury is toxic and because of this, amalgam fillings have been linked to various diseases, such as Alzheimer's, autism and multiple sclerosis.
However, there is no scientific evidence to correlate any such link. Indeed, the American Dental Association (ADA), US Food and Drug Administration (FDA), and various health agencies have stated that amalgams are perfectly safe. The truth of the matter is that the causes of these afflictions remain largely unknown. Removal of amalgam fillings will not make any person any less susceptible.
Amalgams do contain mercury. But when this metal is combined with other elements, such as copper, zinc or tin, a stable alloy is formed; one that dentists have been using for more than 100 years to combat the effects of tooth decay. There are currently several large scale studies under way, sponsored by National Institutes of Health, which are focused on providing definitive answers to issues raised about the use of silver-colored amalgams. Concerns have also been raised about amalgam fillings releasing small amounts of mercury vapor but there is no scientific evidence to justify these suspicions.
Caring for filled teeth
As with any other teeth, the best advice is to follow good oral hygiene practices. Aside from regular, vigorous brushing (with fluoride-containing toothpaste) first thing in the morning and last thing at night, you should pay regular visits to your dentists for professional cleaning. Flossing is another fundamental activity that will remove foreign bodies from those parts of your teeth which are simply inaccessible to brushing.
Your dentist might suspect a filling to be cracked if its sides aren’t fitting snugly to the tooth – an issue that is known as ‘leaking’, and which allows saliva and debris to seep inside the filling. In this instance it will be necessary to take X-ray images to assess the extent of the damage. Other issues that will indicate your filling needs attention are if you can feel a sharp edge with your tongue, if there is a visible crack, or a portion of the filling is missing.
Issues with fillings
After a filling has been placed into a cavity it is common for the affected area to remain sensitive to air, pressure, sweet foods or hot or cold liquids. Normally this will resolve itself within a matter of weeks, during which time it is best to simply avoid whatever it is that can exacerbate sensitivity (although it is best not to resort to pain relief tablets).
If there is no improvement in tooth sensitivity after a month it would be best to contact your dentist again. What might be recommended is the use of specialist toothpaste, or the application of a desensitizing agent. The last resort would be to consider root canal treatment.
It is common for patients to experience pains around the filled area. If you find it painful to bite, it may well mean that the filling needs to be reshaped, so you should book a return visit to your dentist. The likely cause for this is when different metal surfaces touch but such discomfort is never a long-term issue. If toothache persists, then root canal treatment may be required.
Some patients do experience what is known as ‘referred pain’. This is where the painful or sensitive areas in your teeth do not necessarily match with the filled cavities. There is likely to be nothing actually wrong with your teeth – the affected areas are merely receiving pain signals from the filled tooth. This phenomenon usually lasts no longer than a fortnight.
Fewer than 100 cases of allergic responses to silver fillings have ever been reported. In these isolated situations, mercury or some other metal used in amalgam fillings are generally accepted to trigger the adverse reactions. The symptoms are similar to those provoked by skin allergies, and might include itching or skin rashes. In most of these instances the patients had a family history of allergies to metals. The dentist will simply choose a different restorative material.
Filling wearing down
As with anything else, fillings will deteriorate over time. Teeth are constantly subjected to pressure, by grinding or chewing, and this will cause fillings to chip, crack of simply wear away. Dentists will check for these issues during your regular check-ups.
The seal between the filling and your tooth enamel can break down, allowing foreign bodies and bacteria to work their way beneath the filling. Decay can develop and if this is not treated, it can lead to an abscessed tooth. If the recurring decay is extensive, there may not be enough healthy tooth tissue to support a replacement filling. Your dentist would replace the original filling with a crown.
If fillings become dislodged, the likely causes include poor cavity preparation, or contamination of the preparation prior to the filling being applied. Older restorations are particularly susceptible to fracturing of the remaining tooth tissue.