DH220 Dental Materials

Lecture #4

Prof. Lamanna RDH, MS

Restorative Dentistry:

Composite

Ivoclar 4 Seasons Composite System®

I. Use - Repair/replace tooth structure that has decayed

or fractured: Cl. III, IV, V, VI, & small Cl. I & II

Cl. V -Before

Cl. V - After

Cl. IV

Cl. I Cl. II

Cl. III

Cl. VI

- Enhance esthetic appearance of teeth: veneers, close diastemas, contour (reshape) teeth

Veneers

Diastemia closed

Recontour peg

laterals

- Cores for cast restorations

- Repairing fractured/chipped porcelain restorations

II. Characteristics

• ↓ thermal conductivity

• ↑ thermal expansion (percolation)

• Polymerization shrinkage

• ↑ sorption

• Color stability (staining due to surface roughness,

internal change)

• Strength: tensile similar to amalgam; ↓ compressive

• ↓abrasion resistance

• Retention mechanism:

chemical

Mechanical

retention

Chemical

retention

III. Types A. Self-curing

- Supplied as a 2-part paste system: base & catalyst

- Limitations: fixed working time (hardens w/in several minutes)

B. Light-curing

- Supplied as direct placement paste; syringe – compule dispensation

- Limitations: must be layered to achieve proper polymerization; utilizes blue light for curing; potential hazard for retinal damage; use of filtered eyewear

- Advantage: more working time

C. Dual-curing

- Self and light cure capacities

IV. Composition A. Polymer (resin) matrix

1. BIS-GMA (bisphenol-A glycidal methacrylate)

2. Triethylene glycol dimethacrylate

B. Glass particles (fillers)

1. Ground quartz, glasses, silica particles

*Always coated with a coupling agent: silane. WHY? Enhances adherence of matrix (resin) to the filler particles.

2. Particle size

a. Macrofills – 10-25 µ - ↑ strength

- ↓ polishability

- ↓ wear resistence (KHN – 55)

- quartz

- primarily used for orthodontics (luting brackets) and cores

b. Microfils – 0.04 µ

- ↓ strength

- ↑ polishability

- silica

c. Small particle – 1 – 5 µ

- strength, but not as strong as macro

- polishable, but not as smooth as micro

- glasses

d. Hybrids (micro + small particle)

- ↑strength

- ↑polishability

- glasses

- radiopaque

Composite surface

Magnified particles

p. 59

C. Chemicals – promotes polymerization

1. Self-curing system:

a. benzoyl peroxide

b. amine

2. Light-curing system:

a. camphoroquinone

b. amine

D. Pigments – provide different shades to match existing teeth

● inorganic oxides

V. Handling and Placement

A. Self-curing composite

· equal portions base &

catalyst spatulated together

· limited working time

B. Light-curing composite

· direct dispensation into site

· increased working time

· use of clear matrix

· exposure to blue light -

polymerization

Chemical Retention ● Step #1 – Acid etchant

– 10-37% phosphoric acid; removes smear

layer on dentin

- applied, rinsed, dried

● Step #2 – Primer

- wetting agent- ↑ penetration into

dentinal tubules

- applied, not rinsed, dried sparingly

● Step #3 – Adhesive (resin material)

- interlocking with dentin to achieve chemical retention –

referred to as “hybrid zone”

- applied, light-cured

Chelating agent

Smear layer

Dentin

Enamel

Process of decalcifying &

removing tooth structure by

chemical means.

Return

Ground dentin & cytoplasmic

cells that are mixed together as

the tooth is prepped. It is sticky

and adheres to the tooth

surface; “smeared” inside the

tooth prep. Return

Hybrid Zone Etched to remove smear layer

p. 48

p. 51

VI. Polymerization A. Two major considerations -

1. Polymerization shrinkage

a. overall volume shrinks

b. creates marginal gaps – breaks chemical seal

Result – sensitivity, 2º decay

2. Extent & depth of curing

a. exposure time –

☼ quantity of light shone on material – do not under cure; impossible to over cure

☼ quality of light of shone on material – bulb should be checked regularly on meter

b. Composite depth – built-up in thin (1.5-2 mm) layers to ensure proper curing; aids in polymerization shrinkage outcome

Material Placement – incremental layering

Vll. Finishing A. Can be finished & polished after placement

B. Wet field, carbide burs, diamonds, discs with varying

grades of abrasiveness

C. Polishing – aluminum oxide or diamond pastes;

composite polishing kits (lab)

Dental Charting – Paper Chart Black’s Classification I – VI Know them!!

Dental charting on a paper chart – hand-out #2

24

IX. Clinical Success

A. Anterior Placement

1. high level of success – 10 years

2. certain cases only 3 – 4 yrs (operator variability??)

3. major reasons for failure: 2º decay, marginal discoloration

– due to inadequate marginal seal

4. Cl. III – low wear/stress - ↑ rate of success

Cl. IV - ↑ stress exposure – rechipping

Cl. V – least success – incomplete sealing

due to dentin/cementum at gingival margin

- mat’l of choice: glass ionomer WHY?

Cl. III

Cl. V

Cl. IV - before

Cl. IV – after - rechipped

Cl. IV

B. Posterior Placement - wear and marginal breakdown

1. Wear – 2 types

a. Abrasive wear – results from the movement of food,

toothpaste, etc over the entire surface

- occurs in a uniform manner

- resin matrix (least resistant) – wears 1st

- filler particles exposed

- as chewing continues – filler particles are pulled out

- result: small holes, rough surface, traps plaque, microbes, stains

Before After

b. Contact/Attrition wear – results from direct contact with opposing dentition

- 3 - 4 times more extensive damage then abrasive wear

KHN: enamel = 350

amalgam = 165

composite = 40 – 80

- Studies have shown that composites last 7-10 years, which is comparable

to amalgam except in very large restorations, where amalgam lasts much

longer than composites.

2. Premolars – less wear than molar placement due to less force during mastication

3. Contraindication to placement: bruxism, grinding

4. No “self sealing” mechanism

5. Exposed filler particles could abrade opposing enamel

6. RDH clinical management –

a. OHI –

b. Instrument choices -

c. Fluoride choices -

Any Questions??