Restorative Dentistry and Endodontics
What this domain tests
Questions test cavity classification, adhesion and shrinkage, material selection, and the diagnosis and technical sequencing of root canal treatment, including irrigation chemistry and causes of failure.
Direct restorations
- Black classes: I pits and fissures, II posterior proximal, III anterior proximal without incisal involvement, IV with incisal involvement, V cervical, VI cusp tips.
- Etch-and-rinse uses 37% phosphoric acid, 15-30 s on enamel and 10-15 s on dentin; self-etch systems are simpler but weaker on unprepared enamel, so selective enamel etching is common.
- Polymerisation shrinkage and the configuration factor drive postoperative sensitivity and marginal staining; layer composite in increments of 2 mm or less and cover cusps in wide cavities.
- Glass ionomer and resin-modified glass ionomer release fluoride and bond chemically; useful in high caries risk and primary teeth.
Endodontic principles
- Diagnoses: reversible pulpitis (sharp, brief cold response), irreversible pulpitis (lingering pain), symptomatic apical periodontitis, asymptomatic apical periodontitis, acute apical abscess with swelling.
- Working length from apex locator plus radiograph, terminating 0.5-1.0 mm short of the radiographic apex.
- Irrigation: sodium hypochlorite 1-5.25% dissolves tissue and disrupts biofilm; EDTA 17% removes the smear layer; chlorhexidine has substantivity but must never contact hypochlorite, forming a precipitate.
- Calcium hydroxide is the usual interappointment medicament. Obturation uses gutta-percha with sealer and a sound coronal seal.
- Failure causes: missed canal (MB2 in roughly 60% of maxillary first molars), untreated anatomy, perforation, coronal leakage and root fracture.
Worked example
A clinician has 5.25% hypochlorite but wants 1% for a patient with a wide apical foramen. Reasoning: dilution factor is 5.25/1 = 5.25, so one part stock plus 4.25 parts water. For 100 mL total, take 100/5.25 = 19 mL of stock and add 81 mL of water. Lower concentration reduces tissue damage on extrusion while retaining antimicrobial effect with adequate volume and time.
Traps
Assuming a radiolucency proves a non-vital tooth; using cold tests as reliable on heavily restored teeth; mixing hypochlorite and chlorhexidine; obturating without a coronal seal.