Amalgam Removal for Fillings

What is an amalgam filling?

Amalgam is a material composed of up to 50% liquid mercury combined with a powdered alloy, typically consisting of tin, silver, zinc, and copper. The reaction between the liquid mercury and the powdered alloy causes the mixture to set at room temperature.

Amalgam was once a popular choice due to its strength and longevity. Additionally, dental amalgam is capable of bonding to teeth and retaining moisture, unlike its counterparts such as composite and ceramic fillings.

Amalgam is also an affordable product due to the low cost of its elements. Its ease of application and lack of need for specialised equipment, like the curing lamp required for composite fillings, further reduce the cost of treatment.

Why is it being removed and replaced?

Amalgam is reactive to different temperatures. When exposed to cold, it contracts, potentially causing small gaps to form between the filling and the tooth. In contrast, heat causes amalgam to expand, which can lead to cracking of the tooth.

Amalgam fillings have a characteristic silver appearance, which can be visually unappealing compared to the natural white of teeth and pink or red soft tissues. This makes it clear that restorative work has been done, which some patients find undesirable.

Concerns about inorganic mercury exposure are also growing. While we cannot yet quantify the long-term effects of such exposure on health, some dental practices are phasing out amalgam fillings. Although it is not fully understood how mercury is absorbed, many practices now replace amalgam fillings with composite or ceramic alternatives.

How is an amalgam filling removed?

The removal of an amalgam filling begins with an assessment of the mouth and an examination of the filling. One common diagnostic tool is an X-ray, which helps the dentist determine the depth and width of the filling.

After the assessment, the dentist will recommend a treatment plan to replace the amalgam filling, often offering options such as ceramic, gold, or composite fillings.

The procedure starts with a local anaesthetic injection into the gum surrounding the filled tooth to numb the area, preventing discomfort.

Next, the filling is broken down. This is done by drilling into parts of the filling, causing it to break apart. The filling is removed in small sections for two main reasons:

1. Drilling generates heat due to friction, and mercury is reactive to heat. Removing it in sections helps cool the area quickly.
2. Mercury vapour is released during the process, which is toxic if inhaled or ingested, potentially harming the lungs, nervous system, and kidneys. A dental vacuum is used to collect and remove debris.

Once the filling is fully removed, the tooth is cleaned. This includes removing any decayed areas and reshaping the tooth if necessary, before drying it in preparation for the new filling.

How is a composite filling fitted?

After the tooth is cleaned, it is prepared for the composite filling by etching the surface of the cavity. Etching helps ensure the composite adheres securely to the tooth.

The composite resin is applied in layers, with each layer cured using a light. Curing each layer is crucial to prevent the filling from being loose or having gaps, which could allow bacteria to enter and cause decay.

Once the cavity is fully filled, the dentist shapes the composite to replicate the natural contours of the tooth. The tooth is then polished to remove imperfections and add a shine.

How is a ceramic filling fitted?

The process for a ceramic filling is different. After the cavity is cleaned, a mould is taken to create an impression of the cavity. This is because ceramic fillings are custom-made in a laboratory, typically using a milling machine.

A temporary cement filling, containing glass ionomer and acrylic, is placed on the tooth in the meantime. These elements help with both the aesthetic appearance and durability of the temporary filling, allowing the patient to maintain normal mouth function while the ceramic filling is being made.

Once the ceramic filling is ready, a second appointment is needed to fit it. The surface of the filling that will bond to the tooth is etched to ensure it adheres to the resin cement agent. The resin cement helps secure the ceramic filling in place, and any excess cement is cleaned using sponges and dental floss.

What are the benefits of a composite filling?

Composite fillings offer several advantages:

• Aesthetics: Composite resin can be colour-matched to the patient’s natural tooth shade, providing a seamless and aesthetically pleasing appearance.
• Stability: Unlike amalgam fillings, composite fillings do not expand or contract with temperature changes, making them more stable for the tooth.
• Non-corrosive: Composite fillings do not corrode over time like amalgam fillings.
• Bio-compatibility: Composite materials are generally biocompatible, although some resins may contain small traces of BPA. However, the negligible amount of BPA is no cause for concern; feel free to ask your dentist about the contents of their composite resin.
• Durability: Composite fillings can last between 5-10 years, depending on how well they are maintained.
• Minimally invasive: Composite fillings require less tooth structure to be removed compared to amalgam fillings, which need more depth and surface area to bond.
• Repairable: Composite fillings can be repaired more easily than amalgam fillings, which typically require complete removal and replacement.

What are the benefits of a ceramic filling?

Ceramic fillings offer excellent aesthetic results due to their customisable colour and shape, which make it easier to match the original appearance of the tooth. As a result, ceramic restorations are often difficult to detect. The material is also stain-resistant, ideal for those wanting to maintain a bright smile.

Ceramic fillings are very durable due to the porcelain component, which is resistant to chipping and fracturing. This contributes to their longevity, with some fillings lasting up to 15 years or more.

Ceramic fillings are also bio-compatible, unlike amalgam and, to a lesser extent, composite fillings, which have raised concerns due to the chemicals contained in their ingredients.