Operative Dentistry
The core decisions
Operative questions center on preserving tooth structure while restoring form, function, and esthetics without injuring the pulp. Understand caries as a process: demineralization precedes cavitation, so sealants and infiltration can arrest early lesions, and extension for prevention has given way to minimally invasive preparation design that keeps margins out of heavy contact areas.
Concepts to own
- Adhesion: etch-and-rinse with 30–40% phosphoric acid removes the smear layer; etch enamel about 15 seconds and dentin 10–15 seconds, then leave dentin moist and glossy rather than desiccated. Self-etch systems are less technique-sensitive but bond enamel less reliably, so selective enamel etching is common.
- Polymerization shrinkage and configuration factor: Class I and Class V preparations have a high C-factor and therefore more interfacial stress; place increments no thicker than 2 mm and consider oblique layering or a flowable liner.
- Amalgam versus composite: amalgam requires mechanical retention and no bevel; composite benefits from an enamel bevel for esthetics and micromechanical retention.
- Liners and bases: calcium hydroxide for direct pulp capping, glass ionomer as a dentin substitute; eugenol-containing materials inhibit composite polymerization.
- Glass ionomer releases fluoride but is brittle and esthetically limited.
Traps
Questions test which material releases fluoride, which preparation needs a bevel, and what C-factor actually means. Beware the claim that self-etch adhesives eliminate postoperative sensitivity universally - they reduce it but do not abolish it. Also note that a shallow enamel-only lesion in a fissure may need only sealing.
Rule of thumb
Before you bond, ask two questions: is the enamel margin beveled, and is the dentin moist but not wet? Then cure in 2-mm increments.