Prosthodontic and restorative materials

Correct answer: D. The pontic design prevents adequate cleaning of the tissue surface

• A. Diabetes amplifies inflammation but does not localise it neatly to one pontic; the pattern points to a local factor.
• B. Occlusal overload affects the abutment teeth and their periodontium, not the edentulous mucosa under the pontic.
• C. True metal allergy is rare and would typically involve tissue in contact with the metal more diffusely, not the pontic site alone.
• D. Correct. A pontic that laps the ridge broadly — or one with a rough, concave tissue surface — traps plaque where neither brush nor floss threader can reach, and the mucosa responds with chronic inflammation.

Correct answer: B. Dual-cure resin cement

• A. Zinc oxide-eugenol is a provisional cement; eugenol also inhibits resin polymerisation.
• B. Correct. Lithium disilicate gains a large share of its clinical strength from adhesive bonding. Etch with hydrofluoric acid, apply silane, then cement with resin — dual-cure where light cannot fully penetrate.
• C. Glass ionomer bonds chemically to tooth structure but not to silica-based ceramic, and it does not reinforce the restoration.
• D. Zinc phosphate is a purely mechanical luting agent, suitable for metal and metal-ceramic crowns but not for a bonded ceramic.

Correct answer: C. It supplies calcium and phosphate ions that redeposit into the demineralised lattice

• A. Mechanical clearance reduces substrate and acid but does not deposit mineral.
• B. Salivary IgA does limit bacterial adherence, an antimicrobial rather than a remineralising role.
• C. Correct. Saliva is supersaturated with calcium and phosphate. Once the pH recovers above the critical value, those ions — with fluoride — reprecipitate into the partly dissolved crystal surface as fluorapatite.
• D. Buffering by bicarbonate is real and important, but buffering alone raises pH without supplying the mineral needed to rebuild the crystal.