Cariology and Restorative Dentistry
This domain tests caries as a biofilm- and diet-driven process, the evidence-based prevention that follows from it, and minimally invasive restoration design - cavity classification, material selection and adhesion.
Caries as a dynamic process
The Stephan curve shows plaque pH falling below the critical pH of about 5.5 for enamel (roughly 6.2–6.7 for root dentine and cementum) after fermentable carbohydrate, then recovering through saliva and bicarbonate. Frequency of sugar exposure matters more than total amount. Detection uses visual-tactile ICDAS scoring plus bitewings; early lesions are white, chalky and non-cavitated, and are reversible by remineralisation.
Prevention that changes outcome
- Fluoride toothpaste at 1350–1500 ppm, fluoride varnish 22,600 ppm for high-risk patients, and supervised brushing in children.
- Fissure sealants on deep retentive fissures of permanent molars.
- Silver diamine fluoride to arrest active cavitated lesions where drilling is not feasible.
- Dietary analysis targeting frequency, plus dry-mouth management (sugar-free gum, fluoride, chlorhexidine where indicated).
Cavity design and materials
G.V. Black classes I to VI still organise descriptions, but preparation now follows minimal intervention: remove only irreversibly demineralised tissue, and in deep lesions consider selective or stepwise caries removal, leaving firm discoloured dentine over the pulp and sealing it. Composite relies on etching (phosphoric acid 30–40%), a hybrid layer and silane-treated filler; polymerisation shrinkage creates stress, highest at high C-factor (low-configuration) cavities such as Class I. Glass ionomer and resin-modified glass ionomer release fluoride and tolerate moisture, suiting cervical lesions and paediatric cases. Amalgam remains a durable, technique-tolerant option where indicated. Indirect inlays and onlays allow cuspal coverage where remaining walls are thin.
Worked example
A 24-year-old has a deep occlusal lesion on an upper first molar, ICDAS 4, brief cold sensitivity with no spontaneous pain, and a radiograph showing radiolucency approaching the pulp. Reasoning: symptoms indicate reversible pulpitis with a vital pulp. Management is selective caries removal to firm dentine, a resin-modified glass ionomer base over the deepest part, an adhesive composite restoration with good seal, and review at six months - not elective pulp extirpation.
Traps that cost marks
- Drilling non-cavitated white spot lesions.
- Using eugenol-containing materials as a direct pulp cap under composite.
- Forgetting rubber dam isolation, which materially affects bonding and outcomes.
- Confusing erosion (acid, no plaque), abrasion (mechanical, foreign object), attrition (tooth-to-tooth) and abfraction (flexural, cervical).