Dental materials Test 2

Purpose of disinfecting impressions/dentures

Prevent cross contamination between patients, clinicians and labs

Compatibility of disinfectants

Not all disinfectants are compatible with all impression materials, must follow manufacturer instructions

Preferred disinfection method

Immersion

Why immersion is the preferred disinfection method

It ensures full surface contact

Why immersion time is limited

Hydrocolloids & polyethers can distort if immersed longer than 10 mins

Steps before and after disinfecting

Rinse impression, shake off water, disinfect, rinse again, store in 100% humidity until poured

Disinfectants harmful to metal

Hydrochlorite damages metal dentures

Proper denture storage

Store in water or water and mouthwash, never dry

Infection control during grinding/polishing

Use PPE, ventilation, disinfect lathe daily, use sterile rag wheels, stones, fresh pumice for each prosthesis

Items requiring heat sterilization

Metal trays, burs, rag wheels, disks, metal spatulas, glass slabs

Why hygienists study materials

To understand behaviour, handle materials properly, assess/treat patients safely, and educate patients

Dentin vs. enamel clinically

Dentin is more susceptible to acid attack, enamel is harder and more wear resistant

Effect of temperature changes

Different expansion rates cause microleakage and sensitivity

Biting forces as a limitation

can fracture teeth and materials

Evaluating product information

Clinical trials are more reliable

Organizations that set standards

ADA, CDA, ISO, FDA

FDA device Class I

Least regulated (prophy paste)

FDA Device Class II

Moderate regulation (composites, amalgam)

FDA Device Class III

Most regulated (bone grafts)

Direct Restorations

Placed in the mouth (composite, amalgam)

Indirect restorations

Made outside mouth (crowns, inlays)

Parts of a bridge

Pontic + abutments

Biocompatibility

Lack of harmful effects on the patient

Inlay

Intracoronal

Onlay

Replaces cusps (extracoronal)

Intracoronal

Inside the crown structure

Extracoronal

Outside the crown structure

Direct veneers

Composite

Indirect veneers

Porcelain

Purpose of provisional restorations

Protect exposed dentin, maintain function/esthetics

Spruce function

Creates channel for molten metal to enter mold

Best strength + esthetics

Ceramometal (metal + porcelain)

Implant metal

Titanium

Disadvantage of ceramics

Brittle, can fracture, wear opposing enamel

Explorer assessment

uses sound + tactile feel

Glass ionomer feels

rough/dull

Visual clues

Enamel translucent, dentin opaque, restorations often uniform in colour

Heat risks with amalgam

>140 degrees F releases mercury

Reducing heat

Use water/mouthwash slurry, light pressure, intermittent contact

Scaling stroke near margins

Use horizontal/oblique, not vertical

Materials affected by stannous fluoride

Composite (discolours)

Polishing systems for composites

Aluminum oxide discs, diamond polishers (PoGo)

Radiopaque

Absorbs more x-rays (appears white)

Radiolucent

Absorbs fewer x-rays (appears dark)

Attenuation

Absorption of x-rays by tissues/materials

Caries appearance

Radiolucent with diffuse borders

Restorations

Have sharp outlines

Cervical burnout

fuzzy

Bone density

slightly less radiopaque

Enamel density

More radiopaque

Gutta-percha appearance

Radiopaque

Definition of polishing

Reducing scratch size to create a smooth, shiny surface

Three body abrasion

Abrasive particles between two surfaces (prophy paste + rubber cup)

Factors increasing abrasion

Harder particles, larger grit, irregular shape, more pressure, higher speed, less lubrication

Selective polishing

Only polish stained teeth, use least abrasive agent

Least abrasive agent principle

Protect enamel and restorations

Air polishing powders

Sodium bicarbonate, aluminum trihydroxide, glycine, erythritol, calcium carbonate

Contraindicated surfaces

Composites, GI, porcelain (depending on powder)

RDA meaning

Relative Dentin Abrasivity; >100 = abrasive

Dentin feels

Smooth