A cavity, also known as dental caries, is a hole that forms in the tooth structure due to the breakdown of hard tissues like enamel and dentin. This process is caused by acids produced by bacteria that metabolize sugars and carbohydrates left on the tooth surface. While some signs of decay are directly observable, the disease often progresses silently in areas not visible to the naked eye. Detecting a cavity requires a multi-step process combining visual inspection with specialized tools and advanced imaging.
Visual Indicators of Early and Advanced Decay
The earliest sign of potential tooth decay on an exposed surface is a white spot, which indicates demineralization or the loss of minerals from the enamel layer. This initial stage is sometimes reversible with proper hygiene and fluoride treatment, as the enamel can take minerals back from saliva in a process called remineralization. These white spots appear chalky or dull compared to the surrounding healthy, glossy enamel.
As decay penetrates deeper into the tooth structure, visual indicators become more pronounced. Advanced decay often presents as dark brown, black, or grey discoloration, signaling that tooth material has been compromised. In later stages, the decay creates a frank cavitation, which is a visible hole or pit in the tooth surface. These visible signs may also correlate with symptoms like sensitivity when consuming hot, cold, or sweet substances.
Professional Non-X-ray Detection Techniques
Dentists use specialized instruments to locate decay that is not yet an obvious hole or dark stain. The dental explorer, a thin, pointed instrument, is used to gently check for soft or sticky spots on the tooth’s chewing surfaces and around existing fillings. A sticky sensation suggests the enamel has softened and the instrument has caught in a weakened area.
Other methods employ light or color to detect changes in the tooth’s density. Transillumination involves shining a narrow beam of light through the tooth, making decayed areas appear as shadows. This occurs because damaged tissue absorbs or scatters the light differently than healthy enamel. This technique is helpful for identifying decay on the smooth sides of teeth. Laser fluorescence devices, such as DIAGNOdent, use a laser to measure reflected light, providing a numerical reading to assess the severity of the lesion, especially on chewing surfaces.
Where Decay Hides: The Necessity of Radiography
Despite effective visual and non-X-ray tools, radiography remains a necessary diagnostic tool because a large portion of decay is physically inaccessible to direct examination. The tight spaces between teeth, known as interproximal surfaces, are prone to decay but are shielded from view. Bitewing X-rays, the most common type for this purpose, provide a detailed image of the crowns of the back teeth to reveal mineral loss in these hidden areas.
Decay also frequently hides beneath existing dental work, a condition referred to as recurrent decay. Over time, the seal between a filling or crown and the natural tooth can degrade, creating microscopic gaps where bacteria and acid accumulate. Radiographs are the only reliable way to detect this decay, which often starts deep beneath the restoration and is not visible from the mouth’s surface.
X-rays are essential for assessing subgingival decay, which occurs below the gum line, and for determining the depth of any detected lesion. A periapical X-ray focuses on the entire tooth, from crown to root tip, providing a view of the internal structures and surrounding bone. This is important for evaluating how close the decay has progressed to the pulp, the innermost chamber containing the tooth’s nerve and blood vessels.