Dental decay, known as dental caries, is a disease process where the hard structure of the tooth breaks down. This destruction begins when acid-producing bacteria convert sugars from food into acids, which then erode the protective outer layer of enamel. Recognizing the visual evidence of this process is important for seeking timely professional care. The appearance of a cavity changes significantly as it progresses, moving from subtle mineral loss to a distinct physical hole.
The First Signs of Enamel Demineralization
The earliest stage of decay is often reversible and presents as a change in the enamel’s optical properties, rather than a physical hole. This initial breakdown of the tooth’s surface is known as a white spot lesion. These spots appear chalky white or opaque, differing distinctly from the surrounding translucent, healthy enamel. The white color is caused by the loss of calcium and phosphate minerals, which increases the porosity and causes light to scatter differently. This demineralization causes the affected area to lose its natural, glossy luster, taking on a dull or rougher appearance.
Visual Appearance of Moderate Decay
If the demineralization process continues without intervention, the decay penetrates deeper, marking the transition to moderate decay. At this stage, the lesion often begins to take on a visible discoloration, transforming from white to a yellow, brown, or even black spot. This color change is a result of acids breaking through the enamel and beginning to affect the underlying, softer dentin layer. The decay can first be observed as a dark pit or groove, particularly in the deep crevices and fissures on the chewing surfaces of the back teeth.
Unlike the smooth, hardened surface of healthy enamel, the surface texture of the cavity becomes rough or sticky to the touch. The dark coloration is due to the accumulation of food debris, bacterial pigments, and staining within the porous, decayed tooth structure. The progression into the dentin accelerates the decay because this layer is less mineralized than enamel and offers less resistance to acid attack.
These spots are highly localized and will not fade with standard brushing, indicating a true structural breakdown rather than a temporary surface issue. The presence of a localized dark stain or a rough-textured area suggests the decay is active and spreading.
Advanced Decay: Visible Cavitation and Holes
The most severe stage of decay is characterized by visible cavitation, which is a physical hole or crater in the tooth surface. At this point, the structural integrity of the tooth has been compromised, creating a noticeable breach. The opening appears dark, often deep brown or black, and can be felt easily with the tongue as a depression or void. Advanced decay often causes the tooth to look visibly chipped or broken because the enamel has been undermined and collapsed. Sensitivity or throbbing pain often becomes a persistent symptom once the decay reaches this depth, signaling that the inner pulp or nerve tissue is affected.
How to Tell a Stain from a Cavity
Distinguishing a harmless stain from a developing cavity can be challenging, as both can appear as dark spots on the tooth surface. External stains, typically caused by dark liquids like coffee, tea, or red wine, usually affect large, smooth areas of the tooth and remain flush with the surface. These stains are surface-level discolorations that do not involve a loss of tooth material.
In contrast, a cavity is a localized process that results in a structural defect. A cavity will feel rough, sticky, or soft when gently examined, while a harmless stain remains smooth and hard. Unlike stains, which are limited to the surface, a true cavity indicates a porous or soft area where the protective enamel has been breached.
While you can observe these differences at home, only a dental professional can definitively determine if a discoloration is a benign stain or an active carious lesion. A dentist uses specialized tools and X-rays to assess the depth and activity of the spot, confirming the diagnosis and recommending appropriate treatment.