4.4 Hard Tissue Examination, Caries Detection & Restorative Evaluation

Hard Tissue Examination, Caries Detection & Restorative Evaluation

Quick Answer: Hard tissue evaluation systematically records dental caries, tooth wear, anomalies, and existing restorations. Dental caries and restorable lesions are classified according to G.V. Black's Classes I through VI. Caries detection has shifted from aggressive tactile probing to visual inspection, air drying, and ICDAS scoring (Codes 0-6). Transillumination assists in detecting anterior Class III/IV caries and posterior fractures. Restorative evaluations assess marginal integrity, microleakage, overhangs, and recurrent caries around amalgam, composite resin, and cast restorations.

1. G.V. Black Classification of Dental Caries and Restorations

Dr. G.V. Black established the foundational system for categorizing cavity preparations and restorations based on anatomical location:

• Class I: Caries or restorations located in pits and fissures:
  • Occlusal surfaces of premolars and molars.
  • Facial or lingual pits of molars.
  • Lingual pits of maxillary incisors (near the cingulum).
• Class II: Caries or restorations located on the proximal (interproximal) surfaces of posterior teeth (premolars and molars). Involves mesial or distal surfaces, frequently extending onto the occlusal surface (e.g., MO, DO, MOD).
• Class III: Caries or restorations located on the proximal surfaces of anterior teeth (incisors and canines) that DO NOT involve the incisal angle.
• Class IV: Caries or restorations located on the proximal surfaces of anterior teeth (incisors and canines) that DO involve and include the incisal edge/angle (e.g., MI, DI, MID).
• Class V: Caries or restorations located on the cervical third (gingival third) of the facial or lingual surfaces of ALL teeth (both anterior and posterior). Does not originate in a pit or fissure.
• Class VI: Caries or restorations located on the incisal edges of anterior teeth or the cusp tips of posterior teeth (added after G.V. Black's original five classes to account for developmental cusp tip defects or severe attrition/abrasion caries).

G.V. Black Quick Location Map:
Class I   -> Pits & Fissures (Occlusal/Facial/Lingual Pits)
Class II  -> Posterior Proximal (MO / DO / MOD)
Class III -> Anterior Proximal (No Incisal Edge)
Class IV  -> Anterior Proximal + Incisal Edge
Class V   -> Cervical 1/3 (Facial / Lingual)
Class VI  -> Cusp Tips / Incisal Edges

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2. Modern Caries Detection: Visual, Tactile, and ICDAS Scoring

Dental caries is a transmissible, multifactorial, biofilm-mediated disease resulting in the demineralization of inorganic tooth structures by organic acids produced during bacterial carbohydrate fermentation (Streptococcus mutans, Lactobacillus species).

Contemporary Tactile vs. Visual Diagnostic Paradigm:

• Traditional Approach (Historical): Forcing a sharp shepherd's hook explorer into suspicious pits and fissures; an explorer "stick" or tug was considered diagnostic for caries.
• Modern Evidence-Based Standard (NBDHE Rule): Aggressive probing with a sharp explorer is explicitly contraindicated. Forcing a sharp tip into a demineralized, non-cavitated enamel lesion ruptures the intact surface zone, creating an iatrogenic cavity and driving acidogenic bacteria into the dentin.
• Current Protocol: Clean teeth, dry thoroughly with compressed air for 5 seconds, use good illumination and magnification. A blunt probe or ball-ended WHO probe is passed lightly across the surface to feel for roughness without applying pressure.

ICDAS (International Caries Detection and Assessment System):

ICDAS provides a standardized visual scoring matrix for clinical caries detection:

• Code 0: Sound tooth structure; no evidence of caries after 5 seconds of air drying.
• Code 1: First visual change in enamel; visible only after prolonged air drying (opalescent or brown discoloration restricted to pit/fissure).
• Code 2: Distinct visual change in enamel; visible when wet (white spot lesion or brown enamel discoloration wider than pit/fissure).
• Code 3: Localized enamel breakdown (micro-cavitation) due to caries with no visible dentin or underlying shadow.
• Code 4: Underlying dark shadow from dentin with or without localized enamel breakdown (grey, blue, or brown shadow shining through enamel).
• Code 5: Distinct cavity with visible dentin involving less than half of the tooth surface.
• Code 6: Extensive distinct cavity with visible dentin involving more than half of the tooth surface.

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3. Transillumination and Diagnostic Technologies

Fiber-optic transillumination (FOTI) utilizes a high-intensity light beam directed through tooth structure.

• Mechanism: Sound enamel and dentin scatter light uniformly, appearing translucent. Demineralized carious enamel/dentin and structural cracks alter light transmission, absorbing light and casting a distinct dark shadow.
• Clinical Applications:
  • Anterior Teeth: Placing a fiber-optic light source on the lingual surface of maxillary/mandibular incisors to detect Class III interproximal caries and Class IV fractures.
  • Posterior Teeth: Transilluminating occlusal surfaces to detect cracked tooth syndrome or craze lines.
• Adjunctive Technologies: Laser fluorescence (DIAGNOdent: measures bacterial porphyrin fluorescence under 655 nm laser light; scores >20-25 indicate dentinal caries), digital radiography, and quantitative light-induced fluorescence (QLF).

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4. Evaluation of Existing Restorative Materials

Dental hygienists must critically evaluate existing restorations for functional integrity, marginal fit, and secondary (recurrent) pathology during routine examinations.

Dental Amalgam Restorations:

• Composition: Silver-tin alloy combined with liquid mercury.
• Marginal Integrity & Ditching: Over time, amalgam margins undergo creep and corrosion, leading to fracture of thin amalgam flash at the margin. This creates "ditching" (a marginal groove). Shallow ditching without secondary caries is polished; deep ditching requires restoration replacement.
• Overhangs: Amalgam extending beyond the cavity preparation margin into interproximal embrasures (caused by improper matrix band placement or wedge adaptation). Overhangs trap plaque, prevent interproximal flossing, cause localized bone loss, and must be recontoured or replaced.
• Tarnish vs. Corrosion: Tarnish is a surface discoloration (sulfide layer) easily polished away; corrosion is chemical breakdown extending deep into the mass, which weakens the restoration but seals the tooth-restoration interface with corrosion products (tin-sulfide/copper).

Composite Resin Restorations:

• Composition: Dimethacrylate resin matrix (BIS-GMA, UDMA) with inorganic filler particles (silica, glass, quartz) and silane coupling agent.
• Polymerization Shrinkage: Composite resins shrink 2% to 5% during light-curing. Shrinkage stresses can cause microgap formation at margins, leading to microleakage, post-operative sensitivity, and recurrent caries.
• Marginal Staining: Discoloration along composite margins can represent benign superficial staining (beverage pigments) or active microleakage/recurrent caries. Recurrent caries appears as a soft, dark shadow beneath the translucent resin.
• Wear and Debonding: Assessing for loss of anatomical contour, surface roughness, or complete adhesive failure.

Cast Gold and Ceramic/Porcelain Restorations:

• Cast Gold Inlays/Onlays/Crowns: Superior marginal adaptation (malleable gold margins can be burnished to <10 microns). Inspected for margin opening, cement dissolution, or wear of opposing enamel.
• Porcelain-Fused-to-Metal (PFM) & All-Ceramic Crowns: Inspected for porcelain chipping/fractures, open margins at the subgingival finish line, and opposing tooth wear (unpolished feldspathic porcelain is abrasive to natural enamel).

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Occlusal Evaluation as a Clinical Assessment Procedure

Under the NBDHE "Assessing Patient Characteristics" domain, occlusal evaluation is a distinct clinical assessment step—not only dental-anatomy knowledge. Document findings during the hard-tissue exam before care planning.

Systematic Occlusal Exam Sequence

1. Static occlusion: Identify Angle's Class I, II (Division 1 or 2), or III molar/canine relationships at maximum intercuspation.
2. Vertical and horizontal overlaps: Measure overjet (horizontal) and overbite (vertical); note open bite, deep bite, or edge-to-edge contacts.
3. Transverse relationships: Record posterior/anterior crossbite and midline discrepancy.
4. Functional excursions: Observe working/non-working contacts in lateral and protrusive movements; note fremitus on anterior teeth under occlusion.
5. Parafunction and wear: Chart attrition facets, abfraction, fractured cusps, and reported bruxism/clenching.
6. Occlusal trauma signs: Correlate mobility, widened PDL space, and vertical bone defects with premature contacts when periodontitis is present.

NBDHE Clinical Integration

• Occlusal findings modify instrumentation access, selective polishing, and referral for occlusal adjustment or orthodontic evaluation.
• In case-based items, mismatched occlusion plus high plaque retention (e.g., deep overbite with crowded mandibular anteriors) elevates localized periodontitis and recession risk and must appear in the care plan rationale.