Dental Impressions Flashcardsr

Flashcards for Dental Impressions Study Notes

Agar

Gelatin-type material from seaweed, used as a thickener.

Alginate

Irreversible hydrocolloid for preliminary impressions.

Base

Foundation or main ingredient of a material.

Border Molding

Contouring impression margins using finger pressure in the mouth.

Catalyst

A substance that speeds up a chemical reaction.

Centric

Object centered, like maxillary teeth over mandibular teeth in correct relation.

Colloid

Suspension of particles in a dispersion medium (e.g., water); has sol and gel phases.

Digital Impression

Intraoral scan of dentition and gingiva.

Elastomeric

Material with rubber-like qualities.

Hydro-

Prefix meaning "water".

Hysteresis

Temperature change causing reversible hydrocolloid to transform states.

Imbibition

Absorption of water, causing swelling.

Occlusal Registration

Reproduction of patient's bite using wax or elastomeric material.

Syneresis

Loss of water, causing shrinkage.

Tempering

Bringing a material to a desired consistency.

Viscous, Viscosity

Fluid's resistance to flow.

Digital impression

3D image captured via computer technology, transferred to dental unit or lab.

What is Preliminary Impressions

Creates an accurate reproduction of teeth and surrounding tissues. Used for: Diagnostic models/casts, Custom trays, Provisional coverage, Orthodontic appliances

What is Final Impressions

Produces the exact detail of teeth and surrounding tissue. Used for: Indirect cast restorations, Partial or full dentures, Implants

What is Bite Registrations / Occlusal Registrations

Reproduces occlusal relationship of maxillary and mandibular teeth when mouth is closed. Provides accurate registration of patient's centric relationship. Important for establishing articulation of dental arches.

What is Impression Trays and must be rigid

Used to hold impression material in the mouth. Must be rigid to: Carry material into oral cavity, Hold material close to teeth, Avoid breaking during removal, Prevent warping of completed impression

What is Stock Trays what it made of? What are the characteristics and what it use for?

Designed for different mouth areas. Available in several types, sizes, and styles. Made of metal, plastic, or disposable polystyrene. Used for edentulous or partially edentulous mouths. Sizes range from pediatric to very large.

What is Custom Trays? what material is use to make it?

Fit a specific patient's mouth for accurate impressions. Constructed by DA or lab tech from a diagnostic model (preliminary impression). Materials: Acrylic resin, Light-cured resin, Thermoplastic resin

Tray Adhesives

Ensures impression remains attached to tray during removal to prevent deformity. Adhesive must dry before loading impression material.

Clinical dental assistant responsibilities

Prepare impression tray.

Set out materials.

Use proper mixing sequence.

Hydrocolloid Materials

Oldest dental impression material, still used for preliminary and final impressions. Physical change from sol (solution) to gel (solid). Irreversible (chemical change). Reversible (thermal change).

what dental impression required for

Single tooth

Full arch

Complete mouth

What dental impression use for

Indirect restoration fabrication

Implant

Denture

Bleaching trays

Mouth guard

Retainer.

Impression is the

negative reproduction of teeth and

surrounding oral structures.

Sol (solution) phase

Fluid or semi-liquid.

Models created from impressions

are positive reproductions

of those structures.

Gel (solid) phase

Semi-solid, like dessert pudding.

Imbibition

Alginate absorbs water and expands if stored in water or saturated paper towel.

Syneresis

Alginate shrinks and distorts if moisture evaporates in open air.

What is Preliminary Impressions

Who take preliminary impressions

What is it use for

Creates an accurate reproduction of teeth and surrounding

tissues.

Taken by: dentist or credentialed dental assistant.

Used for:

Diagnostic models/casts

Custom trays

Provisional coverage

Orthodontic appliances

Reversible Hydrocolloid

Changes physical state from sol to gel and back to sol. Temperature change causes transformation.

What is Final Impressions

Who take Final Impressions

What is it use for

Final Impressions

Taken by: dentist or expanded function/rda

Produces the exact detail of teeth and surrounding tissue.

Used for:

Indirect cast restorations

Partial or full dentures

Implants

Hysteresis

Describes the temperature change that causes the reversible hydrocolloid material to transform from one physical state to another.

What is bite registrations/occlusal

Who take bite registrations

What is it use for

What it’s important for

Taken by:dentist or the expanded function/rda

Reproduces occlusal relationship of maxillary and mandibular

teeth when mouth is closed.

Provides accurate registration of patient's centric relationship.

Important for establishing articulation of dental arch

Elastomeric Materials

Used when an accurate impression is essential. "Having elastic or rubber-like qualities." Allows removal without distortion or tearing.

What are the 3 classification of dental impression

How do you select the dental material

Preliminary

Final

Occlusal/bite registration

Dental material selection depends on the intended fabrication.

Light-Bodied Material

Syringe-type or wash-type. Dispensed directly onto prepared/surrounding teeth with a special syringe/extruder. Less viscous, flows into details of prepared tooth.

Impression Trays is use for

Must be rigid to:

Used to hold impression material in the mouth.

Carry material into oral cavity

Hold material close to teeth

Avoid breaking during removal

Prevent warping of completed impression

Two basic types: stock trays and custom tray

Two basic types:

stock trays and custom trays.

Impression Trays Characteristics

Quadrant trays (half an arch)

Section trays (anterior portion of arch).

Full-arch trays (entire arch)

Impression tray characteristics:

Perforated surface: Material oozes through holes,

creating a mechanical lock.

Smooth surface: Requires adhesive to hold material

securely.

Sizing of Tray

Selected by trying in the patient's mouth.

Correct size is :

Is comfortable

Extends slightly beyond facial surfaces of teeth

Extends ~2-3 mm beyond third molar, retromolar, or

tuberosity area

Is sufficiently deep to allow ~2-3 mm of material

between tray and incisal/occlusal edges

Depth/length of the tray is extended with:

What wax is added to palate area for patient with high palate

utility wax on the border if needed.

Softened utility wax added to palate area for patients with

high pal

Custom Trays is designed to?

what materials is use to create a custom tray?

What can it be fabricated for?

Custom Trays

Fit a specific patient's mouth for accurate impressions.

Constructed by DA or lab tech from a diagnostic model

(preliminary impression).

Materials used:

Acrylic resin

Light-cured resin

Thermoplastic resin

Can be fabricated for:

Full arch

Quadrant

Sectional

Tray Adhesives Is use

Adhesive must be______before loading impression material

Apply adhesive______before use

Ensures impression remains attached to tray during removal

to prevent deformity.

Adhesive must dry before loading impression material.

Apply adhesive 15 minutes before use.

What are the 3 main type of adhesive

What’s there uses?

VPS adhesives (blue): for polyvinyl siloxane and

polyether materials

Rubber base adhesives (brown): for rubber base

impression materials

Silicone adhesives (orange-pink): for silicone

impression material

Hydrocolloid Materials

What 2 impression it’s use for

Irreversible is what type of change

Reversible is what type if change

Oldest dental impression material, still used for preliminary

and final impressions.

Physical change from sol (solution) to gel (solid).

Irreversible (chemical change).

Reversible (thermal change).

Irreversible Hydrocolloid: Alginate

Irreversible hydro colloid Cannot return to ——————-

What impression is it use for?

Cannot return to sol state after gelling (chemical change).

Used for preliminary impressions

Composition and Chemistry

List all alginate components and what the do?

Potassium alginate: Thickening agent, from seaweed.

Calcium sulfate: Reacts with potassium alginate to form gel.

Trisodium phosphate: Slows down reaction time for mixing.

Diatomaceous earth: Filler, adds bulk.

Zinc oxide: Adds bulk.

Potassium titanium fluoride: Prevents interference with

setting and surface strength

What are the two physical phases of hydrocolloid impression material

Gel strength is lower than_______

Hydrocolloids have difficulty withstanding________ and _________

Sol (solution) phase: Fluid or semi-liquid.

Gel (solid) phase: Semi-solid, like dessert pudding.

Gel strength is lower than elastomeric materials.

Hydrocolloids have difficulty withstanding tensile stress

(tearing) and elastic strain (stretching).

Strength

Alginate must be completely set to resist____________

Strength increases even after______

Alginate must be completely set to resist tearing during

removal.

Strength increases even after it appears set.

Side note: Leaving impression in the mouth for the manufacturer's

recommended time achieves maximum strength.

Dimensional Change

High water content makes alginate ________from environmental changes.

Impressions(alginate) must be poured up within ______

Imbibition: Alginate absorbs water and expands if stored in___ or ______saturated paper towel.

Syneresis: Alginate_____ and ____if moisture

evaporates in open air.

Storage: Disinfected impression in plastic biohazard bag with

slightly moistened towel maintain____relative humidity,

minimizing distortion.

High water content makes alginate susceptible to distortion

from environmental changes.

Impressions must be poured up within 1 hour.

Imbibition: Alginate absorbs water and expands if stored in

water or saturated paper towel.

Syneresis: Alginate shrinks and distorts if moisture

evaporates in open air.

Storage: Disinfected impression in plastic biohazard bag with

slightly moistened towel maintains 100% relative humidity,

minimizing distortion

Regular and Heavy-Bodied Materials

Tray-type materials. Thicker than light-bodied. Fill the tray. Stiffness helps force light-bodied material into contact with prepared teeth and surrounding tissues to ensure accurate impression and details.

Initial set

Stiffening of paste without elastic properties; material can only be manipulated during this stage; mix must be completed within working time.

Final set

Elasticity appears, changing to a solid, rubbery mass; material must be in place before elasticity develops.

Final cure

Occurs within 1-24 hours; slight dimensional change.

Automix System

Provides a homogeneous mix without waste. Extruder mixes and dispenses automatically. Used with any viscosity. Loaded with dual cartridges (catalyst and base).

Mixing Unit System

Tabletop or wall-mounted unit; saves time. Advantages: Controlled dispensing, Infection control, Versatility (can mix various materials).

Putty System

Higher viscosity than heavy-bodied materials. Warmed in palms, which warms up syringe material and accelerates setting without reducing intraoral working time.

Dimensional stability

Ability to keep shape after removal.

Deformation

Ability to resist permanent change caused by stresses during removal.

Polysiloxane Bite Registration Paste

Fast-setting, No resistance to biting forces, No odor or taste, Gains dimensional stability over time, Convenient to use.