Restoring the back teeth: amalgam versus resin composite fillings

Close up of amalgam filling in a back tooth, being checked with dental mirror

Traditionally, metal fillings made of a silver‐coloured material known as amalgam have been used to treat tooth decay in the back permanent teeth effectively and cheaply. But there have been concerns about the way they look, and concerns about the mercury they contain. The Minamata Convention on Mercury is a global agreement that has promoted a worldwide reduction in the use of mercury (including amalgam fillings) in order to reduce the impact of mercury on the environment. Tooth‐coloured fillings made of a composite resin material have been used as an alternative to amalgam fillings. Initially, they were used only in the front teeth, but as their quality has improved, they have been used in permanent teeth at the back of the mouth.

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What are the most accurate tests for finding cancer of the mouth (oral cancer) and conditions that may lead to oral cancer?

Diagnosing mouth cancer involves the surgical removal of a piece of affected tissue (biopsy) which is then sent to a laboratory for examination of the cells using a microscope. This is painful for patients and involves a delay in finding out the results. Persistent abnormal patches or sores in the mouth may represent mouth cancer or oral potentially malignant disorders (OPMDs). OPMDs can sometimes turn into mouth cancer, but if identified early enough patient outcomes can be improved.

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Comparing treatments for advanced tooth decay

Illustration of a cross-section of a tooth  showing the different layers (tooth pulp, dentine, enamel. The dark shadow of caries is encroaching into the dentine.

Tooth decay is very common and can cause pain, eating and speaking difficulties, and self‐consciousness. Teeth are made up of three layers: enamel (hard outer layer), dentine (hard inner layer), and pulp (nerves and blood vessels). Our mouths contain bacteria, which grow in a sticky film over our teeth known as dental plaque. The bacteria live on sugar from our diet and turn it into acid that dissolves the teeth. Saliva can reverse this process, but if there is too much sugar in the diet or bacteria are not removed often enough by toothbrushing then the acids will erode the teeth. This can progress into the dentine, eventually causing a hole in the tooth, which is known as a cavitated carious lesion. If it reaches the pulp, it can cause infection. Cavitated carious lesions can be treated by complete removal of decayed parts of the tooth and placement of a filling. Dentists call this non‐selective carious tissue removal and conventional restoration. Although effective, this risks weakening the tooth or causing problems if the pulp of the tooth is exposed. There are some newer ways of treating the tooth which involve removing less or none of the tooth decay.

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What are the benefits and risks of using lasers to treat tooth hypersensitivity (short, sharp tooth pain)?

Woman with protective glasses receiving laser treatment in the dental chair

Tooth hypersensitivity is short, sharp pain that is not due to a dental disease or problem such as caries (holes in the teeth) and can occur when teeth come into contact with hot or cold food or drinks; cold air; or specific food or drinks such as sugar and fizzy (carbonated) drinks. It can also occur when people brush their teeth or receive professional dental care.

An option for treating tooth hypersensitivity is to use laser (light) therapy. Lasers produce a narrow, focused beam of light that is applied to the painful tooth to treat it. Depending on the type of laser used, the treatment either aims to seal off the painful area, or to numb it.

We wanted to find out if lasers work to treat tooth hypersensitivity, and whether they are associated with any unwanted (adverse) effects.

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Visual or visual‐tactile examination for the diagnosis of dental caries

Why is it important to improve the detection of dental caries (tooth decay)?

Dentists often aim to identify tooth decay that has already advanced to a level which needs a filling. If dentists were able to find tooth decay when it has only affected the outer layer of the tooth (enamel) then it is possible to stop the decay from spreading any further and prevent the need for fillings. It is also important to minimise the number of false‐positive results when treatment may be given when caries is absent, and improved visual detection methods may reduce such occurrences.

What is the aim of this review?

The aim of this Cochrane Review was to find out how accurate visual classification systems are for detecting early tooth decay as part of the dental ‘check‐up’ for children and adults who visit their dentist. Researchers in Cochrane included 67 studies to answer this question.

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Does using a rubber dam to isolate teeth from the rest of the mouth during a dental procedure improve the success of tooth repairs?

When dental practitioners need to repair a tooth, they often isolate it from the rest of the mouth to:

‐ keep away saliva to prevent it from impairing the bonding of materials;
‐ reduce aerosols produced during the dental procedure to a certain extent;
‐ stop materials, liquids or instruments used for the repair from being swallowed or damaging the mouth.

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What works best to preserve the jaw bone after tooth extraction?

Why is this question important?

Tooth extraction is a common procedure that can be used for example to:

– remove damaged or diseased teeth;
– remove teeth that are in the wrong place; or
– make room for other teeth.

After a tooth extraction, the part of the jaw bone that used to hold the tooth shrinks because it is no longer needed to support the tooth. If the bone shrinks too much, this can:

– make it difficult or impossible to replace the missing tooth with an artificial one (an implant); and
– weaken the support and health of neighbouring teeth.

To limit bone loss after tooth extraction, dentists or surgeons can carry out a procedure called alveolar ridge preservation (ARP). ARP involves filling the hole left by the missing tooth (using a range of different materials and techniques), and leaving it to heal for several months. The hole can be filled with human, animal, or artificial bone. It can be covered over (to stop gums from growing into the hole) using:

– materials that, after some time, are naturally absorbed by the body; or
– materials that need to be removed with surgery once no longer needed.

To find out if ARP works to preserve jaw bone after tooth extraction, we reviewed the evidence from research studies. We also wanted to know if any materials and ARP techniques are better than others.

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Electrical conductance for the detection of early tooth decay

Dentists often aim to identify tooth decay that has already advanced to a level that needs a filling. If dentists were able to find tooth decay when it has only affected the outer layer of the tooth (enamel) then it is possible to stop the decay from spreading any further and prevent the need for fillings. It is also important to avoid a false‐positive result, when treatment may be provided when caries is absent. This is one of a series of reviews on diagnostic tests for dental caries, we also have reviews on imaging modalities, transillumination, fluorescence devices and tests to detect root caries.

The aim of this Cochrane Review was to find out how accurate electrical conductance devices (non‐invasive devices that send an electrical current to the surface of the tooth) are for detecting and diagnosing early tooth decay as part of the dental ‘check‐up’ for children and adults who visit their general dentist. Researchers in Cochrane included seven studies published between 1997 and 2018 to answer this question.

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Dental imaging methods for the detection of early tooth decay

Dentists often aim to identify tooth decay that has already advanced to a level which needs a filling. If dentists were able to find tooth decay when it has only affected the outer layer of the tooth (enamel) then it is possible to stop the decay from spreading any further and prevent the need for fillings. It is also important to avoid a false-positive result, when treatment may be given when caries is absent.

This Cochrane Review aimed to find out how accurate X-ray images and other types of dental imaging are for detecting early tooth decay as part of the dental ‘check-up’ for children and adults who visit their general dentist. Researchers in Cochrane included 77 studies published between 1986 and 2018 to answer this question.

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Are antibiotics an effective way to prevent infection following tooth removal?

Teeth that are affected by decay or gum disease or painful wisdom teeth are often removed by dentists. Tooth extraction is a surgical procedure that leaves a wound in the mouth that can become infected. Infection can lead to swelling, pain, development of pus, fever, as well as ‘dry socket’. Dry socket is where the tooth socket is not filled by a blood clot, and there is severe pain and bad odour. These complications are unpleasant for patients and may cause difficulty with chewing, speaking, and teeth cleaning, and may even result in days off work or study. Treatment of infection is generally simple and involves drainage of the infection from the wound and patients receiving antibiotics.

Antibiotics work by killing the bacteria that cause infections, or by slowing their growth. However, some infections clear up by themselves. Taking antibiotics unnecessarily may stop them working effectively in future. This ‘antimicrobial resistance’ is a growing problem throughout the world. Antibiotics may also cause unwanted effects such as diarrhoea and nausea. Some patients may be allergic to antibiotics, and antibiotics may not mix well with other medicines. Dentists frequently give patients antibiotics at the time of the extraction as a precaution in order to prevent infection occurring in the first place. This may be unnecessary and may lead to unwanted effects.

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