Dental Materials and Instrument Handling
This domain covers properties of materials, handling and mixing, and correct instrument selection. Expect questions on setting reactions, isolation, and compatibility.
Core concepts
- Impression materials: alginate (irreversible hydrocolloid, dimensional change with time, pour promptly), elastomers (polyvinyl siloxane, polyether-more stable and accurate).
- Restorative materials: amalgam (strong, needs moisture control, not esthetic), composite (light-cured, esthetic, technique-sensitive), glass ionomer (releases fluoride, bonds to tooth).
- Cements and liners: zinc oxide-eugenol (sedative, avoid under composite), calcium hydroxide (pulp protection), resin cements.
- Gypsum products: plaster, stone, improved stone; water-to-powder ratio affects strength and setting expansion.
- Instrument handling: explorers for caries detection, periodontal probe for pocket depth, mirror for indirect vision, cotton pliers for retrieval, and handpieces with correct burs.
Traps
Questions test which material releases fluoride (glass ionomer), which needs a dry field (amalgam and composites), and whether eugenol is compatible with composites (it inhibits polymerization). Another trap: alginate impressions must be poured promptly because they lose water and change dimension.
Rule of thumb
Match the material to the requirement: esthetics → composite; strength under load → amalgam; fluoride release → glass ionomer; accuracy for fixed prosthetics → elastomeric impression.