Intro to composite resins

Question 1

Components of composite resin

Answer 1

1. Resin matrix - BisGMA
2. Inorganic filler particles - barium/borosilicate/strontium glass
3. coupling agents - silane
4. initiators

Question 2

3 features of filler particles which benefit the restoration

Answer 2

• increase strength
• decrease linear coefficient of thermal expansion
• offer radiopacity

Question 3

Why is post op sensitivity common in composite resin restos?

Answer 3

due to polymerization shrinkage which causes the resto to pull at the margins and cause leakage

Question 4

Marginal relationship of amalgam-enamel = _____

Marginal relationship of composite-enamel = ____

Answer 4

Marginal relationship of amalgam-enamel = BUTT-TYPE JOINT

Marginal relationship of composite-enamel = ADHESIVE INTERFACE

Question 5

What is a butt type joint?

Answer 5

two pieces of material are joined simply by placing their ends together. ie. no adhesion

Question 6

As compared to amalgam preps, bonding of composite to enamel allows for:

Answer 6

1. more conservative prep design
2. less reliance on mechanical retention
3. less removal of unsupported enamel

Question 7

Simplified 3 main steps in composite restos:

Answer 7

1. etch
2. primer/bond
3. composite

Question 8

Two step total etch procedure:

Answer 8

• Etchant applied to preparation (15 sec enamel, 10 sec dentin)
• etchant is washed off with water for 10 seconds and lightly dried (do not dessicate dentin)
• Bonding agent applied to prep with microbrush (light cured for 10 seconds)
• Composite is incrementally placed (20 second light cure per increment)

Question 9

Synonym of etchant:

Answer 9

conditioner

Question 10

Following etching, what should the appearance of enamel and dentin be?

Answer 10

• enamel: white and chalky

- dentin: no change

Question 11

What is generated on the surface of enamel by etchant?

Answer 11

microporosities. These increase SA for adhesion and increases surface energy to enhance penetration of bond into enamel surface

Question 12

Conditioned dentin results in:

Answer 12

-removal of SMEAR LAYER, resulting in enhanced bond between tooth and composite resin

Question 13

what is the smear layer?

Answer 13

• thin layer on dentin surface that has received instrumentation
• comprised of loosely bound debris, collagen and HA crystals

Question 14

Major difference between total etch and self etch

Answer 14

In self etch, the smear layer is not removed and a hybrid layer is created when material is added to the tooth.
-Also, total etch uses higher acid content than self-etch

Question 15

How many generations of dental adhesive exist?

Answer 15

8 gens

Question 16

dental adhesive is classified based on 4 things:

Answer 16

1. generation (8)
2. Mode of application
3. Number of clinical steps
4. Etching pattern (total vs self etch)

Question 17

How many clinical steps are involved in 3rd, 5th and 8th generation adhesive?

Answer 17

3rd - 3 (E+P+B)
5th - 2 (E+PB)
8th - 1 (EPB)

Question 18

Bond enters microporisities of enamel and create long projections called __ ___

Answer 18

resin tags

Question 19

RDT stands for:

Answer 19

remaining dentin thickness

Question 20

What relationship is there with bond strength and RDT?

Answer 20

As RDT decreases, the concentration of dentinal tubules increases and so does peritubular dentin. These contain higher organic content (therefore more H2O) and thus bonding to dentin becomes increasingly unreliable.

Question 21

Bond strength to ____ dentin is stronger than with ___ dentin

Answer 21

Bond strength to INTERTUBULAR dentin is stronger than with PERITUBULAR dentin

Question 22

3 things that happen as RDT decreases:

Answer 22

1. concentration of dentinal tubules increases
2. peritubular dentin:intertubular dentin increases
3. Resulting bond decreases

Question 23

Goals of adhesive/bond

Answer 23

1. seal enamel-composite interface
2. increase retention
3. decrease leakage at enamel-composite interface

Question 24

4 types of composite resins

Answer 24

1. flowable
2. microfill
3. macrofill
4. hybrid

Question 25

Filler content in the 4 types of composite resins

Answer 25

1. flowable - lowest
2. Microfill - low
3. Macrofill - high
4. a. mcrohybrid - high filler loading