5 - Radiographic Interpretation of Dental Caries

Radiographic Exam Choice: CBCT

Not for dedicated caries diagnosis: beware of artifacts that imitate caries, but diagnose large lesions when you see them.

CBCT: relatively new tech

Not for dedicated caries diagnosis: beware of artifacts that imitate caries, but note large lesions when you see them on scans taken for other reasons.

Radiographic Appearance of Caries: Proximal caries

Triangular dark area with its base to tooth surface.

Caries is..

A dynamic process with periods of demineralization and remineralization corresponding to active and arrested lesions.

Radiographic Exam Choice: Bitewings

Best to assess for proximal and occlusal caries - avoid overlap of the proximal surfaces (closed contacts).

Radiographic Caries Detection in context:

Clinical exam always necessary. Visual access to occlusal surface is excellent. Clinical access to proximal surface is often limited. Radiographic exams very helpful, especially for proximal surfaces. Caries (demineralized areas) appear radiolucent with moderately diffuse borders. Radiography cannot reveal whether a lesion is active or arrested(unless compared to previous images, in which similar image geometry is important to accurately estimate lesion size.)

Buccal/Lingual Caries

Common in enamel pits and fissures. Start round, become elliptical or semilunar. Clinical exam key. Image shift principles can be helpful.

Caries Imitators and Treatment decisions:

False positives result in unnecessary and irreversible "preparation" of tooth tissue. False negatives are typically ok - caries often progresses slowly (unless patient has very high caries risk..)

Radiographic Exam Choice: Periapicals

Good for occlusal caries, okay for proximal caries.

Caries Imitator: Dental pits/fissures/anomalies:

Hypoplastic pits Concavities produced by wear (RPD clasps). Typically more well defined. Clinical exam is key.

Secondary Caries Imitator: Image Sharpening

Image sharpening is a post-processing alteration of image contrast. Can create generalized, uniform radiolucent bands next to restorations.

Caries Progression:

Incipient (enamel only) Moderate (involving dentin) Severe (involving pulp)

Occlusal Caries - Moderate

Incipient occlusal lesions rarely seen radiographically (thick occlusal enamel) Typically appears as a broad-based radiolucent zone often beneath a fissure.

3D Intraoral Radiography: new technology

Intraoral dental tomosynthesis is an intraoral approach to collecting 3D image information. Multiple independent x-ray sources in a single tube-head take images rapidly from different angles. Computerized reconstruction provides a bitewing or periapical image with thin slices in the buccal-lingual direction.

Radiographic Appearance of Caries: Occlusal caries

Rounded shape radiolucent area, wider in the dentin, narrow at the occlusal surface (usually at the deepest pit)

Rampant Caries

Extensive caries - encroaches on pulp quickly. Often pediatric patients. Often poor dietary habits. Socio-economic factors. Methamphetamine use.

Caries and Xerostomia

A dry mouth severely tips the caries process towards demineralization. Xerostomia can come from: medicantions and therapeutic radiation in the region of salivary glands(sometimes called "Radiation caries"), Sjogren's syndrome. Caries begins at cervical region. Extensive decay

Proximal Caries - Moderate Lesion

Caries involving the dentin. Demineralization spreads more rapidly along DEJ and in dentin than in enamel. Classically appears as dark triangle with base on DEJ and apex directed toward pulp. Enamel portion typically broader than incipient lesions. Cavitation of the enamel surface often defines an unarrestable lesion(requires restorative therapy) Initial cavitation cannot be accurately determined on radiographs. Approximately half of lesions just into dentin have surface cavitation(the other half can be arrested) Lesions extending more than halfway to the pulp are always cavitated.

Incipient Proximal Caries

Caries lesion in enamel only. Classic appearance: Radiolucent triangle with broad base at tooth surface. Can also appear as a notch, dot, band, or thin line. Approximately 50% of all incipient proximal lesions are not seen radiographically

Caries vs. Imitators: General Interpretation Guidelines:

Caries lesions tend to have more diffuse borders than imitators. Caries lesions tend to be found in characteristic locations (sub-contract), Imitators tend to be more well-defined and follow anatomic boundaries. Always confirm radiographic findings with clinical findings!

Radiographic Appearance of Caries: Incipient caries

Dark or radiolucent area on the surface -Enamel only. -Only 50% of lesions are actually visible on radiographs. All caries tend to be more diffuse/ill-defined than caries imitators.

Recurrent Caries

Diffuse radiolucency immediately next to a restoration. Beware radiolucent liners/cement (more well-defined, uniform) Can be obscured on radiograph by metallic restorations. Can occur beneath gingival margin. Clinical examination important: -Can be buried -If blocked out, only way to find is exam.

Cervical (Root) Caries

Diffuse, rounded radiolucency below CEJ. Associated with gingival recession. More rapid decay of cementum and dentin (softer) Clinical inspection key.

Extraoral Bitewings: new technology

Larger field of view! Ghost shadow superimposed. Preliminary studies indicate good detection but increased false positive rates.

Caries Imitator: Adumbration (Cervical Burnout)

Localized artifact from thinner edges of tooth structure. More defined, more angular at tooth margin. Much more diffuse towards pulp.

Caries Imitator: Radiolucent Restorations/Liners/Cements

Much more well-defined than caries. Radiolucent restorations take shape of preparation. Liners/Cements are uniform-width lucencies. Clinical exam helpful.

Proximal Caries Location

Occurs between contact and free gingival margin

Radiographic Exam Choice: Panoramic

Only if lesion is large. Newer panoramic units have an "extraoral bitewing" protocol; not bad, but beware of artifacts that imitate caries (false positives)

Caries Imitator: Mach band effect

Optical illusion Characteristic uniform, thin radiolucent line at enamel dentin interface. Subtle