Dental Materials I- Ch 43/ COMPLETED

Dental Materials must?

Be able to withstand the biting and chewing force in the posterior area in the mouth

Force is?

Any push or pull-on matter

Stress can cause?

distortion

Strain results in?

Change in the material

Types of stress and Strain

1. Tensile stress and strain:

(Pulls and stretches the material)

2. Compressive stress and strain:

(Pushes the material together)

3. Shear stress:

(Two forces of material parallel to each other sliding in opposite directions.) ((Think of like cutting a piece of paper with scissors, blades are parallel but work in opposite directions.))

Ductility means?

capacity of a metal to be stretched or drawn out by a pulling or tensile force without fracturing

Malleability means?

The capacity of a metal to be extended in all directions by a compressive force

Why are thermal changes a concern?

Thermal changes can lead to expansion or contraction of dental materials.

There is also a need to protect the pulp from thermal shock from extreme differences in temperature

Tensile means?

Compressed means?

Shear means?

Tensile: the ability of a material to withstand tension or pulling forces without breaking.

Compressed: subjected to a squeezing or pushing force that reduces its volume.

Shear: the ability of a material to withstand forces that cause one part of the material to slide past another.

How do microleakages occur?

Microleakages occur when there are gaps or spaces between the dental restoration and the tooth structure, allowing fluids and bacteria to enter, potentially leading to decay or other complications.

Can dental materials contract or expand at their own rate?

Yes

Electric current (or Galvanic Action) is?

When there are two different or dissimilar metals present in a dental restoration, an electric current can flow between them, leading to potential irritation or discomfort.

Corrosion

reaction within a metal exposed to corrosive products such as temperature, humidity, and saliva.

Hardness

is a measure of the resistance of a metal to indentation, scratching, or abrasion

Solubility

is the ability of a material to dissolve in a solvent, often influenced by temperature and composition.

A material that dissolves easily will?

wash away and leave the tooth structure exposed

Adhesion

is the tendency of different materials to cling together when they are in contact, essential for providing secure bonding and stability in dental applications.

Characteristics of dental materials that can affect the adhesion process are:

Wetting: Ability to flow over a surface (example: water flows easily)

Viscosity: Property of a liquid that causes it not to flow easily(thickness), (example: maple syrup)

Retention

is the ability of a material to maintain its position or hold onto a surface, crucial for the longevity of dental restorations and appliances.

Types of curing

1. Auto-cured or self cured: material hardens as a result of a chemical reaction of the materials once mixed together

2. Light-cured: material does not harden until exposed to a curing light

3. Dual-cured material: some curing takes place as the material is mixed

(The final cure does not occur until the material has been exposed to a curing light)

Materials used in these types of restorative and esthetic procedures are:

Amalgam

Composite resins

Glass ionomers

Temporary restorative materials

Tooth-whitening products

Amalgam

A dental material made from a mixture of metals, primarily mercury, silver, tin, and copper, used for filling cavities due to its durability and strength. Amalgam is a safe, affordable, and durable material used predominantly to restore premolars and molars.

Amalgam is not used as often today.

The alloy powder is a combination of metals

Silver, give strength

Tin, makes it workability and gives strength

Copper, for its strength and corrosion resistance

Zinc, to suppress oxidation

What are the controversial issues regarding mercury?

What is the response of the ADA and National Institution of Health-Nations Administrations have to say about this matter?

1.Potential harm to patients from mercury within the amalgams placed in their teeth

2.Toxicity level of mercury vapors affecting dental personnel exposed over a long period

3. Health risk for dental personnel is greater than that for a patient. The dentist and assistant who are exposed to mercury vapors daily should be aware of their toxic effects. An increase in exposure can result in tremors, kidney dysfunction, depression, and central nervous system disorders

The ADA and the National Institute of Health-Nations Administration have agreed that there is no basis for claims that amalgam is a significant health hazard

Trituration

The process of mixing powdered dental amalgam alloy with mercury to form a homogenous mass, essential for achieving optimal properties in dental restorations.

Condensation

The amalgam is carried by the amalgam carrier and placed in increments into the prepared tooth

Each increment is condensed immediately with the use of an amalgam condenser

Purpose of condensation is to:

• Pack the amalgam tightly into all areas of the prepared cavity

• Aid in removing any excess mercury

Carving and Finishing

Hand carving instruments: are used to carve back the amalgam material to the tooth’s normal anatomy

Burnisher: is used to smooth the amalgam

Once most of the carving has been completed, the patient is instructed to bite down lightly on articulating paper

Composite Resin

Widely accepted material of choice by dentists and patients

Placed mainly in anterior teeth because of their esthetic qualities.

Increasingly being placed in posterior teeth as well

Not as strong as amalgams or gold restorations

Class I restorations means?

restore defects on the occlusal surface of posterior teeth, the occlusal thirds of the facial and lingual surface of molars, and the lingual surfaces of maxillary anterior teeth.

Class II restorations means what?

restore defects that affect one or both of the proximal surfaces of posterior teeth.

Class III restoration means what?

used to repair cavities or decay on the anterior teeth

Class lV restorations mean what?

used to restore damage to the front teeth, specifically when both the crown and incisal edge are affected

Class V restorations mean what?

a specialized restorative solution designed to combat issues such as gum recession and non-carious cervical lesions (NCCL)

The composition of composite resins is a chemical mix, which includes

Organic resin matrix

Inorganic fillers

A coupling agent

Pigments

Fillers add?

the strength and characteristics that are needed in a restoration.

Flowable composites

Material wear-resistant

Flows easier

Sealant composites

Less viscosity to allow the material to flow into the pits and fissures

Coupling Agent

Adds strengthen to the resin by chemically bonding the filler to the resin matrix

Pigments

Add color

Differences for composites versus amalgam

The cavity preparation for a composite resin is designed to hold the resin material by means of a bonding system rather than by retention added into the preparation in a amalgam restoration.

Matrix systems will vary with composite resins.

Placement of composite resin is accomplished by increments; light-curing is performed before additional increments are added.

Shade selection

Most critical aspects when working with composite resins

Shade guide is always used when determine correct shade for application

Tips When Choosing a Shade

Determine tooth shade, if possible, in daylight or with standardized daylight lamps and not under normal ambient lighting

Make the choice quickly; always accept the first decision since the eyes begin to tire after approximately 5 to 7 seconds

Polymerization of Composite Resins

Polymerization is the process by which the resin material is changed from a pliable state into a hardened restoration. Occurs through auto-curing or light-curing

Light-curing uses a high-intensity light source

Finishing and Polishing

The finishing and polishing of composite resins are much different than an amalgam procedure

Because composite materials go from the soft, pliable state to being completely hardened by polymerization, the dentist cannot carve or adjust with hand instruments

Finishing burs and abrasive materials are used to contour and polish a finished composite resin

Glass Ionomers

Most versatile dental materials available

Because glass ionomers can adhere chemically to teeth

Most unique feature of glass ionomers they release fluoride after the final setting

Indications for Glass Ionomer Use

Primary teeth because of the fluoride release and minimal cavity preparation requirement

Final restorations in nonstress areas such as class V and root surfaces

Sealants

Core material for a buildup

Provisional (longer-term temporary) restorations

Composition of Glass Ionomers

Glass ionomer, combination of glass, ceramic particles, and a glassy matrix

Temporary Restorative Materials

Temporary restoration is designed to maintain and restore function and keep the patient comfortable for a limited time

If a tooth has lost a filling or has a small pit, an intermediate restorative material would be selected

If a cusp is gone, or dentist has prepared the tooth for a cast restoration (crown).

Intermediate Restorative Materials

IRM is a reinforced zinc-oxide eugenol composition

Eugenol has a sedative effect on the pulp, and fillers are added to improve the strength and durability of the material

Common uses of IRM include:

Restoration of primary teeth

Restorative emergencies

Caries management programs

IRM is supplied as a powder and a liquid, which are mixed manually on a treated paper pad, or as premeasured capsules that are activated and then triturated

Provisional Restorative Materials

Designed to cover the major portion of a tooth or several teeth for a longer period

Acrylic resins are supplied in several ways: as a liquid/powder, in premeasured tubes, and auto-mix cartridge.

Tooth-Whitening Materials

Most popular and cost-effective ways of restoring the esthetic appearance of teeth

Whitening products can be found in many everyday items such as toothpaste, fluoride, mouth rinses, and even chewing gum

Composition of Whitening Materials

Most tooth-whitening products are made from a peroxide-based ingredient

Peroxide-based solutions are supplied in different concentrations

Works deep within the enamel to remove staining and discoloration

Reasons Teeth Become Discolored

Aging

Consumption of staining substances such as coffee, tea, colas, and tobacco

Trauma

Use of tetracycline

Excessive fluoride

Nerve degeneration

Aging of restorations

Methods of Tooth Whitening

“in office” or “at home”

The bleaching gel typically contains between 10% and 30% carbamide peroxide

Laser Bleaching done by light accelerating bleaching- isolation of the tissue done in the dental office.

Indirect Restorative Materials

An indirect restoration fabricated outside the mouth by a dental laboratory technician

Gold-Noble Metal Alloys

Gold in its purest form is much too soft for use in cast dental restorations

The combination of gold with other metals to form an alloy gives the characteristics and hardness required of an indirect restoration

Soft: Type I alloy

• Used for casting inlays subject to slight stress during mastication

Medium: Type II alloy

• Used for practically all types of cast inlays and posterior bridge abutments

Hard: Type III alloy

• Acceptable for inlays, full crowns, three-quarter crowns, and anterior or posterior bridge abutments

Extra-hard: Type IV alloy

• Designed for crowns, bridges, and cast-removable partial dentures

Ceramic Castings

Ceramics are compounds, which is a combination of metallic and nonmetallic elements.

Combinations of ceramic-metal restorations include the following:

Porcelain fused to metal (PFM)

Porcelain bonded to metal (PBM)

Ceramic-restorations (C/M)

Porcelain-metal (P/M)

Porcelain

Ceramic most used in dentistry

Combines strength, translucency, and the ability to match natural tooth color

Stronger than direct restorations, such as composite resins, which are created in the mouth

Why Porcelain?

Shading of colors matches tooth color well

Improves the esthetic appearance of anterior teeth

Has the strength of metal

Good insulator

Low coefficient of thermal expansion