DA 103: Midterm Review

Fall Term 2026

The safe interaction of dental materials, with the rest of the body is defined as the materials

Biocompatibility

The study of dental materials consists of

chemical & physical reaction & manipulation of material

Tensile stress is

pulling/stretching

Compressive stress is

pushing/squeezing

Shearing stress is a

sliding force

Ductility is

The ability of an object to be pulled or stretched under tension without rupture.

E.g., gold being stretched into thin wires for a restoration

Malleability is

The ability to be compressed and formed into a thin sheet without rupture

E.g., gold being hammered into a thin sheet for a restoration

OSHA & Hazard Communication Standard

1) Written hazard communication program: must identify all employees who are exposed to hazardous chemicals and explain how the company manages HazCom, including how labels, Safety Data Sheets (SDSs), and training are handled.

2) Inventory of Hazardous Chemicals: An up-to-date master list of all hazardous chemicals present in the facility

3) Safety Data Sheets: contain health & safety information about each chemical in the office

4) Labeling of containers: strict container labels

5) Employee training: when a new employee is hired, new chemical product is added to the office, and once a year for all continuing employees (records must be kept on file and retained for at least 5 years).

Strain is the

distortion or deformation that occurs when an object cannot resist a force.

E.g., elastic deformation

The internal reaction to an externally applied force is called

Stress

Which of the following restorative materials is most likely to fracture under compressive stress?

Porcelain

Which of the restorative materials is the least soluble?

Composite resin

Corrosion is of greatest concern for which restorative material?

Amalgam

Surface discoloration of a metal restoration is called

Tarnish

Restorative materials with values of thermal conductivity similar to enamel include

composite resin

Galvanism is when

A newly placed amalgam contacts another metal restoration

E.g., amalgam contacting gold

Microleakage may be responsible for

recurrent decay, marginal staining, & postoperative sensitivity

An excessive film thickness may cause

improper seating of the restoration

The leakage of fluids and debris extending along the tooth restoration interface is called

microleakage

Materials used for the restoration of enamel need high

vitality

Color shades can vary depending on the incident light or source of light. This effect is called

metamerism

The maximum amount of stress a material can withstand without breaking is

ultimate strength

The greatest stress a structure can withstand without permanent deformation is

elastic limit

Resistance to flow is known as

viscosity

Mixing time is the length of time from

the beginning of mixing to the beginning of working time

Name 3 classifications of dental materials:

1) Preventative/therapeutic materials

2) Restorative materials: direct & indirect

3) Auxillary materials

Example of preventative/therapeutic materials

Pit & fissure sealants

Example of auxillary materials

Impressions materials and gypsum

American Dental Association (ADA):

consumer protection, promotes products, established in 1859

American National Standards Institute (ANSI):

safety, competitiveness, established in 1918

FDA:

regulatory authority, medical & dental devices

International Organization for Standardization (ISO) & World Dental Federation (FDI):

international standards

Environmental Protection Agency (EPA):

Clean Water Act & mandatory amalgam separators

When one is working with dental materials, the most common work-related health and safety hazards are

exposure to mercury, exposure to particulate matter, exposure to biological contaminants, & exposure to the toxic effects of chemicals

The acid used most commonly to etch tooth structure for bonding procedures is

37% phosphoric acid

Self-etching bonding agents

use acidic primers to etch the tooth structure

Dentin sensitivity can be caused by

open (unsealed) dentinal tubules, and/or over-etching or over-drying of the dentin

The smear layer

is a tenacious layer of cut tooth debris on the surface of enamel and dentin

For a composite to have greater wear resistance, it needs

to have a higher filler content

Composite resins are often classified according to their

filler particle size

The purpose of a silane coupling agent for composite resins is

to improve the bond between the filler particles and the resin matrix

The polymerization shrinkage of a composite

can be minimized by placing and curing a series of small increments

T or F: All composite restorative materials appear the same on radiographs of the teeth

False

One of the advantages of glass ionomer is

that it has been shown to release fluoride

Fluoride can be found as naturally occuring in what drink?

Tea

When enamel is remineralized with fluoride

the resultant remineralized crystal is more resistant to acids

Fluorosis is always considered to be

a sign that the person has ingested more than the optimum amount of fluoride

Sealant material is

an unfilled or lightly filled resin

When a dental sealant is placed, the technique

requires the field to be kept dry

What is the best candidate for a sealant?

A newly erupted tooth with numerous deep fissures

Very small filler particles are added to sealant material for which purpose?

To decrease wear of the sealant

How is the surface of the tooth prepared before acid etching for sealant placement?

The surfaces are cleaned with pumice

The acid most commonly used to etch the enamel for sealant placement is which one?

Phosphoric acid

The tip of the light wand of the curing light should be held how close to the sealant?

Very close, about 1 mm away from the surface

After placement of a sealant, which of the following should be checked?

The sealant surface for voids or porosities, the occlusion, and the contact areas of adjacent teeth

The most common reason for loss of a sealant shortly after placement is which of the following?

Saliva contamination after acid etching

How should the surface of the enamel appear after acid etching?

Frosty white

What does the acid etch do to the surface of the enamel?

Creates a roughened irregular surface

The most important requirement for successfully bonding sealants to enamel is

Good isolation to prevent saliva contamination

Studies show caries to occur in pits and fissures most often in which group of teeth?

Permanent premolars

The main purpose of most desensitizing agents

Is to plug the openings of the exposed dentinal tubules

Bleaching of teeth works

by penetrating both enamel and dentin and ozidizing stain

Which of the following impression materials is/are transformed from a sol to a gel state when set?

Alginate and agar hydrocolloids

Hydrophobic impression materials

need a dry field to get the best results

Agar hydrocolloid

works well in a moist feild

An irreversible hydrocolloid

cannot reverse from a gel to a sol because a chemical reaction prevents it

Polyvinyl impression materials are of the class known as

elastomers

Polysulfide impression material

has excellent tear strength

All of the following are considered positive reproductions of the dental structures EXCEPT:

an impression

To decrease the working time of a gypsum product without a change to any physical properties, it is best to:

increase the water temperature

The main difference between model plaster and dental stone is

particles size and shape

The most appropriate type of gypsum product to use for orthodontic casts is

Type III

Detection of restorative materials (list 3):

Appearance, location, and radiography

Describe the components of a mercury spill kit and identify the regulatory agency responsible for governing eyewash stations.

Mercury spill kits includes: mercury absorbing powder, mercury sponges, disposal bag (mask & utility gloves should be worn when cleaning a mercury spill). OSHA regulates eyewash stations.

*never use a broom/vacuum to clean a mercury spill

Describe the EPA’s role in amalgam waste:

In July, 2017, under the Clean Water act, dental practices must control amalgam waste through the use of amalgam separators certified by ISO.

Preliminary impressions are

made prior to another tx and often used for planning purposes or to make working casts from which temp crowns can be made

Final impressions are

more accurate to their replication of the oral structures.

E.g., crown, bridge, implant

Alginate hydrocolloid (irreversible) is used for

preliminary impressions, diagnostic casts, removable orthodontic appliances, and more. It’s thick & doesn’t flow well.

Elastomers are used for ______________, ceramic & ____________ restorations, and bridges. _________- like impression material. 4 types: _____________, condensation silicones, polyvinyl _____________, and polyethers. PVS has ____________ dimensional _____________.

metal castings, bridges, rubber, polysulfide, siloxane, excellent, stability

Identify the material and its uses: Polyvinyl Siloxane (PVS)

Use: bite registration

Physical: available in different consistencies, sets into a rubber like material.

Mechanical: highly elastic and flexible, excellent tear resistance

Dimensional stability: excellent dimensional stability as it has very little shrinkage after setting

List the types of Gypsum Materials:

Type 1 (rarely used): Impression plaster

Type 2: model plaster, used in diagnostic casts

Type 3: Dental stone, used in working casts

Type 4: high strength/low-expansion stone, used for dies

Type 5: high strength/high-expansion stone, used for dental casts

Diagnostic cast is a

model of the teeth or oral tissues used to examine the mouth, plan tx, and study a pts bite

Working cast is a

model used to create dental restorations or applications, such as crowns, bridges, and dentures

Dies is a

replica of an individual prepared tooth used to make or shape a restoration, such as a crown or inlay

Baseplate wax are

sheets of wax, usually pink in color, used to help set a denture in place

Boxing wax is used

to form the base portion of a gypsum model

Utility wax (periphery wax)

provides a better fit into the vestibule and control the movement of the impression material

Key ingredient in bonding is

phosphate ester

Components of Composite Resin

1) Resin matrix: UDMA (urethane dimethacrylate)

2) Filler particles: for structural strength

3) Coupling agents: Silane, glue for the filler & resin

4) Pigments: match tooth color

Large filler particles are

macrofilled composites that are difficult to polish (no longer used)

Small filler particles are

microfilled particles that are easy to polish but are weak and have greater polymerization shrinkage

Identify uses, composition and manipulation techniques of Glass Ionomers

Type 1: luting agents

Type 2: restorative materials: root caries

Type 3: liners & bases for cavity prep

Type 4: fissure sealants

Composition: contain nanoparticles, better wear resistance, polish ability, and color match.

Manipulation techniques: plastic instruments, overfill the prep, stop manipulating once gel has hardened

Dental Ceramics uses, advantages, and disadvantages:

Use: crown, fixed bridge,, inlays, onlays, veneers

Advantages: esthetics, biocompatibility, wear resistance, color stability, stain resistance

Disadvantages: brittleness, wear of the opposing enamel or restorations

Creep is the

gradual change in shape of the restoration from compression by the opposing dentition during chewing or by pressure from the adjacent teeth

Tarnish is just

surface oxidation

Corrosion is a

chemical reaction between the amalgam & substances in saliva and food, resulting in oxidation of the amalgam

NOBLE metal doesn’t…

tarnish or corrode in the oral environment

HIGH noble must…

contain at least 60% noble elements (gold, palladium & platinum), of which 40% must be gold base metals (copper, silve, gallium)