Interpretation of Caries

What are the components of Caries Assessment?

Patient history + Clinical Exam + Radiographic Exam —> Caries Diagnosis

What are the components of clinical detection?

• Location

• Extent

What is the G.V Black Classification of caries?

What is the importance of clinical detection

• Can identify lesions on directly visible/exposed tooth surfaces clinically

• Caries on proximal surfaces are nearly impossible to identify clinically until cavitation has occurred

  • At this point, more invasive treatment is usually indicated

  • Transillumination can help identify Class 3 caries earlier

What is the caries process?

Demineralization → destruction

Greater rate of demineralization in dentin due to lower mineralized component than enamel

What is the radiographic importance of caries process

• Decrease in density → greater x-ray penetration in carious area → radiolucency

• Degree of radiolucency increases with extent

What is the imaging modality for caries assessment?

• Intraoral (BWs > PAs) 7-20 lp/mm depending on the receptor type

• BWs have the highest spatial resolution

• The role of bitewings is to detect small interproximal caries before they can generate symptoms or become clinically visible

Imaging Modality for Panoramic Images

• Caries visible on a panoramic image are often large enough to be
  clinically apparent

• Should not rely on panoramic to detect caries (especially small lesions)

Imaging Modality for CBCT

• Many studies show CBCT caries detection rates are approximately equivalent to intraoral modalities for non-restored teeth

• Beam-hardening and streak artefacts from metal objects are limiting factors

• Use of CBCT solely for purpose of caries detection is discouraged and not evidence based

  • Increased patient dose and cos

What are the steps for radiographic evaluation of caries detection?

1. Location

   1. Tooth number

   2. Involved surfaces

2. Depth

3. Primary vs. recurrent/secondary caries

What is primary caries?

Unrestored tooth surface

What is recurrent/secondary caries?

Associated with a restoration, caries associated with restorations/sealants (CARS)

What are the classification systems for radiographic interpretation of caries?

• Multiple classification or scoring systems to categorize caries size and depth

• International Caries Classification and Management System (ICCMS) builds on International Caries Detection and Assessment System (ICDAS) for caries staging by including patient information (caries risk)

• Merged ICDAS/ICCMS assigns caries progression to one of four stages of tooth involvement

  • Sound surfaces (code 0) – No radiolucency

  • Initial stage caries (RA) – outer half of enamel (RA1), inner half of enamel with or without DEJ involvement (RA2), and outer third of dentin (RA3)

  • Moderate stage caries (RB) – middle third of dentin (RB4)

  • Extensive stage caries (RC) – inner third of dentin (RC5), reaches the pulp (RC6)

Radiographic depth and cavitation

• Once cavitation occurs, bacteria will maintain carious lesion activity unless it is surgically managed

• Can reliably predict tooth surface is cavitated and dentin heavily infected when radiographic penetration depth is deeper than outer 1/3 of dentin

  • 32% of radiographically visible lesions that extended into the outer third of dentin show cavitation

  • 72% of lesions extending into the middle third of the dentin or deeper were cavitated

    • Clinically classified under ICDAS/ICCMS as moderate and extensive stage

ICDAS-ICCMS Classification System

Radiographic Categories and Clinical Categories

ADA Caries Classification System

What is the ADA caries classification system?

• To outer ½ enamel (E1)

• To inner ½ enamel ( E2)

• To outer 1/3 dentin (D1)

• To middle 1/3 of dentin (D2)

• To inner 1/3 of dentin (D3)

What does this image show?

Caries within the outer half of the enamel (RA1, E1)

What does this image show?

Caries within the outer third of the dentin (RA3, D1)

What does this image show?

Caries within the inner third of the dentin (RC5, D3)

What does this image show?

Caries within the inner half of the enamel (RA2, E2)

What does this image show?

Caries within the middle third of the dentin (RB4, D2)

What does this image show?

Caries in contact with the pulp (RC6, D3)

Decision to treat a carious lesion surgically is based on

• Caries risk status of the patient

• Depth of the lesion

• Whether there is cavitation

When decision made not to manage lesion surgically, follow-up imaging schedule developed to monitor

• Follow-up period based on patient’s caries risk

• New images should be as similar as possible to original for accurate comparison

  • See if lesion has grown (active) or not (arrested)

  • If lesion has progressed, decision regarding surgical treatment may be revised

What is the susceptible zone?

Between the contact point of the teeth and gingival margins. And it may extend apical to this zone only if there is periodontal bone loss

Where is there a higher risk of caries developing?

On interproximal surface in contact with carious lesion or restoration

What are some treatment considerations?

• Conservative interventions (oral hygiene, fluoride) for ICCMS RA categories (involvement of enamel or *outer 1/3 of dentin)

• Surgical management when there is cavitation or the lesion has reached middle third of dentin (RB4, D2)

• Differences in management strategies mostly based on caries risk status

  • Higher risk would benefit from more proactive approach

What are incipient caries?

DO NOT extend into DEJ, most often defined at extending ½ through enamel

What shape would you see in incipient caries?

Triangle with broad base at outer surface

• Demineralization occurs along long axes of enamel rods (oriented 90 ̊ to enamel surface)

• Other shapes: band, rectangle, semicircular notch

What are primary caries?

Involves DEJ or extends through

What is the caries progression of primary caries?

• Once lesion reaches DEJ, demineralization spreads across the interface

• Second triangle forms with broad base at DEJ

  • Dentin triangle has a wider base than enamel

• Lesion progresses through dentinal tubules toward pulp

  • Triangular shape may be lost as lesion gets bigger due to curvilinear or “S-shaped” arrangement of dentin tubules

Interproximal Lesion Examples

Primary dentition

• Primary teeth have thinner enamel

• Dentin reached more quickly

• More rapid progression

What are occlusal caries?

• Large lesions easily observed clinically and radiographically

  • Large, dark circles in crowns

  • Pulp exposure can not always be determined

• Not very effective at detecting small lesions

  • Minimum or no changes in enamel

  • Near impossible to identify enamel-only lesions (enamel too thick)

  • Thin line, triangle or cup shaped zone under enamel with base at DEJ

• Easier to identify in panoramic radiographs

• Clinical exam important

  • High false negative rate in 2D radiographs

Examples of occlusal caries

What are buccal and lingual caries?

• Identified from clinical exam

  • Arise in cervical region, pits or fissures

• Well-defined ovoid radiolucency

  • Surrounding structure intact

• Need 2 images at different angles to localize (SLOB)

• Can be confused with occlusal due to superimposition

  • Occlusal usually not as well defined

What are root caries?

• Patients with gingival recession and/or bone loss

• Cratering on buccal/lingual/proximal root surfaces of teeth involving cementum

  • Cementum is soft and thin

  • Often involves CEJ

• Most can be detected clinically

• Saucer like irregular cavitation

• Can be confused with cervical burnout

What are rampant caries?

• Rapid progression with severe widespread involvement

• Most often in

  • Young children – poor hygiene and dietary habits

  • Patients with xerostomia – often secondary to head/neck radiation therapy

• “Radiation caries” seen on surfaces and teeth that do not usually present carious

  • Often cervical location

What are recurrent (secondary) caries?

• New areas of demineralization that develop at margin of existing restorations

• Can be caused by defective restoration and/or ineffective hygiene

• Radiolucencies in tooth structure at junction of restoration and tooth

• Best image for detection is BW due to beam angulation

  • Can use 2nd image at different angle to help distinguish if in doubt

What are residual caries?

• Represent areas of demineralization that remain when the original lesion has not been completely removed

  • Can be involuntary

  • Most often purposeful when a large lesion encroaches on the pulp

Examples of recurrent caries

What are some limitations and pitfalls?

• False Positives

  • Cervical burnout

  • Mach band effect

• Radiographic vs. clinical depth

• Caries activity

• Impact of angulation and superimposition in 2D images

What are false positives?

• When a carious lesion is thought to be detected on image but tooth structure is actually intact

• Studies show observers consistently have < 100% agreement on caries diagnosis

  • Especially true with enamel caries

• Most common source of false-positives: misinterpretation of cervical burnout

• Lack of training or experience

• Technical errors (ex. contact overlap)

What is cervical burnout?

• Artifact that can mimic caries

• Commonly at or just apical to CEJ near alveolar crest

• X-rays passing tangentially through proximal area encounter less structure

  • Thinner tooth structure absorbs fewer x-rays → appears relatively more radiolucent

• Shallow depression/concavity on mesial/distal root surface can make area appear more radiolucent

• Imperfect mesiodistal overlap of roots in multirooted teeth

  • Confirm by identifying PDL spaces of each roo

Radiographic interpretation of PA

What is the Mach Band Effect?

• Artifact caused by differential contrast between more opaque enamel and less opaque dentin

  • Optical illusion from differential stimulation and inhibition of neighboring receptors in retina

  • Retinal receptors overstimulated by enamel opacity inhibit adjacent receptors that perceive more radiolucent dentin

• Results in perception of a radiolucent band in the superficial dentin adjacent to DEJ

• To overcome Mach-band effect

  • Mask the more radiopaque enamel

  • If the radiolucent band disappears, not caries

  • If continues to be seen, caries

• If lesion visible only on image without clinical evidence

  • Monitor/observe to avoid unnecessary treatment

What are some depth limitations?

• Caries are further advanced clinically than radiographs indicate

• Bacterial penetration of dentinal tubules and early demineralization do not produce enough change in density to affect x-ray attenuation

• Estimated that enamel demineralization must be > ~35% before lesion can be observed on image

What are some activity limitations?

• Demineralization (radiolucency) detected on image does not equate to active carious lesion

  • Can represent older, inactive (arrested) lesion (scar in enamel)

  • Remineralization of surface is possible due to contact with calcium and phosphorus in saliva

  • Cannot penetrate deeper

• Second image at another time point is required to differentiate active from arrested caries

What are some 2D superimposition limitations

• Degree of radiolucency is determined by extent of caries in buccolingual plane

• Caries depth relative to pulp

  • Appearance of exposure could be result of superimposition

• Small amount of demineralization may not be visible

  • Tooth with broad contact does not show caries as well – greater density of tooth structure surrounding caries

• True depth of lesion often greater than visible on image

What are some 2D angulation limitations

• Change in angulation impacts ability to detect and stage caries lesions

• Horizontal angulation

  • Contact overlap can obscure lesion and DEJ

  • Changes projection of lesion relative to other structures

    • DEJ, pulp

What are some 2D vertical angulation limitations

In presence of restorations

Examples of 2D angulation limitations

A. BW with correct vertical and horizontal angulation of x-ray beam demonstrating carious lesion on the distal surface of the maxillary left first molar.

B. BW of the same patient with incorrect horizontal angulation causing an overlap of the interproximal regions, hiding the carious lesion

C. PA of same patient with incorrect vertical angulation, causing an overlap of the coronal restoration with a portion of the root, again hiding the carious lesio

Examples of 2D angulation limitations

What are some differential diagnoses for caries?

• Unfilled Cavity Preparations

  • Usually sharply marginated unless secondarily affected

• Radiolucent restorations - older restorative materials completely radiolucent

  • "C" shape of prep helps distinguish

• Cervical Burnout - overpenetration of cervical area of tooth due to decrease in mass and density of tooth structure

  • Can extend below level of bone; caries does not

• Mach Band Effect - optical illusion producing radiolucency along DEJ

• Idiopathic Cervical Resorption – type of external resorption

• Dental Anomalies - irregularities and hypoplasias

• Tooth Wear - physiologic (attrition) or non-physiologic (abrasion & erosion) wear will result in low-density areas that may mimic caries

• Abfraction – non-carious cervical lesions