A dental filling is a restorative material used to repair a tooth damaged by decay (dental caries). The procedure involves removing the decayed portion of the tooth and filling the resulting space. This intervention halts the progression of decay, restores the tooth’s function and structure, and physically seals the tooth, preventing harmful oral bacteria from accessing inner tissues.
How Tooth Decay Starts
Tooth decay begins with the interaction of oral bacteria and dietary sugars. Bacteria, such as Streptococcus mutans, live in the mouth and form plaque, a sticky film on the teeth. When carbohydrates are consumed, these bacteria metabolize the sugars.
This metabolic process produces organic acids as a byproduct. These acids lower the pH level within the plaque biofilm. When the pH drops below a critical threshold (around 5.5 for enamel), the acidic environment begins to dissolve the tooth’s mineral structure.
The enamel is composed mainly of crystalline hydroxyapatite. During an acid attack, essential minerals are pulled out of the enamel structure in a process called demineralization. Saliva works to neutralize these acids and reincorporate minerals back into the enamel (remineralization). However, frequent consumption of sugary foods overwhelms this defense, causing net mineral loss and weakening the tooth structure.
When a Filling Becomes Necessary
The need for a filling is determined by the progression of decay through the tooth layers. In the earliest stage, decay is confined to the enamel and appears as a white spot, representing mineral loss. This damage is often reversible through diligent oral hygiene and professional fluoride treatments that promote remineralization.
A filling becomes necessary when the decay progresses past the enamel and creates a hole. Once the damage breaches the enamel barrier and enters the underlying dentin, the process accelerates rapidly. Dentin is softer, more porous, and contains tiny tubules leading toward the tooth’s nerve center, the pulp.
Decay in the dentin is irreversible and must be removed and replaced with a filling to seal the tooth. The filling restores structural integrity and prevents bacteria from advancing deeper. Increased sensitivity to hot, cold, or sweetness often signals the decay has reached this sensitive dentin layer, requiring immediate intervention.
What Happens If a Cavity Goes Untreated
Without a filling, the decay continues toward the innermost chamber of the tooth, which houses the dental pulp. The pulp contains the tooth’s nerves and blood vessels. Once bacteria reach the pulp, they cause inflammation and infection called pulpitis, often accompanied by persistent or excruciating pain.
If the infection is left untreated, bacteria can spread beyond the tooth root, leading to a dental abscess. An abscess is a pocket of pus that forms at the root tip, causing significant swelling and bone loss in the jaw. At this advanced stage, a simple filling is no longer sufficient to save the tooth.
Treatment escalates to more invasive procedures, such as a root canal to remove the infected pulp, or a complete tooth extraction. In serious instances, an untreated infection can spread to other areas of the body, including the jawbone and sinuses, potentially causing systemic infection.