Dental Linings, Bases, Impression Materials, Acrylics, and Nylons

Vocabulary flashcards covering dental linings, bases, impression materials, acrylics, nylons, and medical grade plastics from DENT2012.

Lining

A thin layer of material placed on the floor of a cavity preparation to protect the pulp from bacteria, chemical irritation, thermal changes, and galvanic action, as well as to stimulate tertiary dentine formation.

Base

A thicker layer of material placed under a restoration to improve its resistance to occlusal load, eliminate undercuts for indirect restorations, and add thermal insulation.

Calcium Hydroxide

A lining material with a high pH ($> 11.0$) that is strongly antibacterial, neutralises acids, promotes tertiary dentine formation with a source of $Ca^{2+}$, but has low strength and high solubility.

RMGIC

Resin-Modified Glass Ionomer Cement; a material with chemical bonding, fluoride release, moderate compressive strength, and a high modulus of elasticity, allowing it to function as a combination liner and base.

Ledermix

A medicinal lining material containing Demeclocycline hydrochloride (broad-spectrum antibiotic), Triamcinolone acetonide (corticosteroid anti-inflammatory), Zinc oxide (structural matrix), Calcium hydroxide, and Eugenol.

Eugenol

A powerful indirect pulpal sedative found in materials like ZOE that inhibits the setting reaction of any resin-based polymerisation reaction.

Zinc Phosphate Cements

Historic base materials with the formula $\text{Zn}_3(\text{PO}_4)_2$ that exhibit high strength, pulpal irritation, and difficult handling.

Philipp Pfaff

A German dentist to Frederick the Great of Prussia who in 1713–1766 first described taking impressions using softened sealing wax and pouring plaster of Paris to create a rigid cast.

Dental Compound

A rigid, mucofunctional thermoplastic impression material introduced in the early 20th century that softens around $50\,^\circ\text{C}$ and can be repeatedly adjusted on the same patient.

Alginate

An irreversible, algae-based hydrocolloid impression material formed from a powder and water mixture (sol to gel to solid) with a reproduction accuracy of approximately $50\,\mu\text{m}$.

Alginate Setting Temperature Dependence

For every $1\,^\circ\text{C}$ increase in room temperature, alginate setting speed increases by $5.5\,\text{seconds}$ for normal set or $5.6\,\text{seconds}$ for fast set.

Imbibition and Syneresis

Processes of water gain and loss affecting alginate dimensional stability, requiring impressions to be poured within $30\,\text{minutes}$ and stored at $100\%$ humidity.

Precision

The closeness of repeated measurements to each other, where higher precision yields greater predictability.

Trueness

The level of deviation of a measurement or impression from the object's actual dimensions.

Elastomeric Impression Materials

Rubber-based impression materials (Polysulfides, Condensation silicones, Polyethers, Addition silicones) offering dimensional stability, high tear resistance, and reproduction accuracy up to ~$10\,\mu\text{m}$.

Dental Acrylics

Rigid, inexpensive removable appliance materials composed of methyl methacrylate (monomer liquid) and pre-polymerised MMA beads (powder), cured via heat, cold activation chemicals, or light.

Polyamides (Nylons)

Thermoplastic condensation copolymers used for removable appliances that can be injected under high temperatures or 3D printed, requiring mechanical looping to secure acrylic teeth.

EVA

Ethylene-Vinyl-Acetate; a clear, soft, pliable, inexpensive thermoplastic medical grade plastic used for oral appliances.

PETG

Polyethylene Terephthalate Glycol; a comparatively rigid medical grade plastic used in removable appliances that allows pressure to move teeth.

Medical Grade Plastics Storage

A maintenance protocol requiring medical grade plastics to be stored dry, avoiding water storage.