composite chemistry

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SAY AHHH, FOR COMPOSITE RESIN FIL ERS: A STUDY OF THE

COMPOSITE RESIN

by

Vishal Patel

A Thesis in Chemistry Education

Presented to the Faculty of the University of Pennsylvania in partial fulfillment of therequirement of the Degree of

Master of Chemistry Education

At

University of Pennsylvania

2007

__________________________________________________

Constance W. BlasieProgram Director

__________________________________________________

Dr. Andrew RappeSupervisor of Thesis



University of Pennsylvania

Abstract

SAY AHHH, FOR COMPOSITE RESIN FILERS: A STUDY OF THE COMPOSITE

RESIN

by Vishal Patel

Chairperson of the Supervisory Committee: Professor Dr. Andrew RappeDepartment of Science

Abstract – Caries are an infectious disease which can be prevented by practicing proper dentalhygiene. In order to understand how caries develop it is important to understand the anatomicalstructure and function of enamel, dentin, and pulp. The process of demineralization of the enamellayer occurs due to the break down of sucrose which is a common sugar ingested daily. The sucrose

is hydrolyzed to produce glucose and fructose. Fructose is broken down via multiple steps of glycolysis to produce lactic acid and a hydrogen ion which dissolves the enamel layer. Once theenamel is demineralized, caries begin to develop. Caries need to be treated with a proper filling which can hold up for multiple years to prevent the caries to further decompose the tooth or evenpossibly fracture a tooth. Amalgam has been used for many years and due to its appearance in themouth, composite resins are being considered as an alternative. The most common dentalcomposite resin currently used is bis-GMA; however, its high viscosity and shrinkage concerns haveforced alternative composite resins to be researched. A cube structure known as silsesquioxanes

have been used with organic tethers which are used to crosslink the cube structures. Thecrosslinking of the hard core composite resin matrix with the organic, soft tethers allow the cubes toreadjust even after the initial reaction. The silsesquioxanes are one of many alternatives being reconsidered.



TABLE OF CONTENTS

List of Figures.......................................................................................................................iiList of Tables.......................................................................................................................iiiPreface.................................................................................................................................. iv Anatomy of tooth................................................................................................................1Formation of Carries (Cavities).........................................................................................1 Amalgam Fillings .................................................................................................................3

Composite Resins and Cements .......................................................................................7 Text Box #1 (What’s free about free radicals?) ................................................... 10 Text Box #2 (Concreteness of Cement).............................................................. 13

Post Shrinkage................................................................................................................... 17State of the Art Composite Resin.................................................................................. 18Conclusion ......................................................................................................................... 22Bibliography....................................................................................................................... 24 Appendix A: Lesson Overview...................................................................................... 26

Lesson Plan (Day 1) .................................................................................................. 29Experiment 1.............................................................................................................. 33Experiment 2.............................................................................................................. 39Experiment 3.............................................................................................................. 44Lesson Plan (Day 2) .................................................................................................. 49Lesson Plan (Day 3) .................................................................................................. 53Daily Learning Log.................................................................................................... 58PIM............................................................................................................................... 59



LIST OF FIGURES

Number Page

1) Tooth Anatomy........................................................................................................1

2) Steps to tooth decay ................................................................................................1

3) Demineralization of Enamel..................................................................................2

4) Sucrose.......................................................................................................................2

5) Hydrolysis..................................................................................................................2

6) Glycolysis...................................................................................................................3

7) Formation of Lactic Acid.......................................................................................3

8) Restored and repaired amalgam restoration .......................................................4

9) Elements used to make amalgam..........................................................................4

10) Symbols and Stoichiometry .................................................................................4

11) Silver-tin phase diagram........................................................................................5

12) Disposal Amalgam vial ........................................................................................5

13) General amalgamation reaction .........................................................................5

14) Schematic drawing of amalgam microstructure ..............................................6

15) Mechanics of Amalgam filling.............................................................................6

16) Amalgam photomicrograph.................................................................................6

17) Human Mercury Exposure..................................................................................7

18) γ-methacryloxypropyltrimethoxysilane..............................................................8

19) 2-methyl-2-Propenoic acid (1-methylethylidene) bis (4,1-phenylenoxy-2-Hydroxy-3,1-

Propanediyl)) (Bis-GMA).....................................................................................820) Stick model of bis-GMA .....................................................................................8

21) Ball and stick model of bis-GMA.......................................................................8

22) Amino-carboxylate based bonding agent (NPG-GMA) ...............................9

23) Carboxylate based bonding agent 9



28) Homolytic Bond Cleavage ............................................................................... 11

29) Benzoyl Peroxide ................................................................................................ 11

30) Initiation .............................................................................................................. 11

31) Electromagnetic Spectrum................................................................................ 12

32) Propagation Stage .............................................................................................. 12

33) Chain Transfer..................................................................................................... 12

34) Second type of chain transfer........................................................................... 13

35) Termination ......................................................................................................... 13

36) Cement Factory................................................................................................... 14

37) Cement Hydration.............................................................................................. 14

38) Organic Monomers ............................................................................................ 16

39) Ball and stick model of ethylene glycol dimethacrylate (EGDMA).......... 16

40) Ball and stick model of triethylene glycol dimethacrylate (TEGDMA)... 16

41) Composition of dental cements....................................................................... 16

42) Termination highlighting the unreacted double bonds ............................... 17

43) Monomer composition......................................................................................17

44) Content of CQ ................................................................................................... 17

45) Microscopic image of prosthesis .................................................................... 18

46) Typical size and volume of cube..................................................................... 18

47) Example of tether.............................................................................................. 19





52) Example of tether............................................................................................. 19

53) Continuous organic phase................................................................................ 19

54) Non-continuous phase ..................................................................................... 19



ACKNOWLEDGMENTS

I would like to express sincere appreciation to all of the administrators, faculty and especially Professor Andrew Rappe for his assistance in the preparation of this manuscript. Inaddition, special thanks to Megan Cubbage whose familiarity with the needs and ideas of theclass was helpful during the early planning phase of this undertaking.



Anatomy of tooth

We always manage to understand by

means of research how our world, the thingswhich are in our environment and mostimportantly how our bodies work to best

explain to each other and ourselves what is

happening chemically. Chemists andmaterial scientists have conducted research

to allow something as small as a cavity inyour mouth to be filled with some sort of

material, which is referred to as a composite,resin, and/or dental fillers in the dental profession. Cement is a non-metallic

substance which hardens to act as a base,

liner, filler, material, or adhesive to bind

devices and prostheses to tooth structure or to each other.

1, 2A composite is a solid

formed from two or more phases that have

been combined to produce propertiessuperior to or intermediate to those of the

individual constituents. Fillers are best

described as a combination of organic andinorganic resin particles that are designed to

strengthen a composite, decrease thermal

expansion minimize polymerization

shrinkage and reduce the amount of swellingcaused by water sorption. Not being

satisfied with the quality of materials

currently being used, scientist are hard atwork attempting to find better materials

which can be used to fill voids in teeth. This

research paper briefly explains the variousmaterials used to fill caries (cavities),

chemically examines a popular monomer used in the dental profession and currentresearch being conducted to bring about new

changes in the process of treating caries.

To best understand how cavities

form, the anatomy of the tooth needs to be

Figure 1: Tooth anatomy3

The anatomical structures relevant to having

a clear understanding of this paper are thedentin, pulp and enamel. The function of

dentin is to act as a mechanical buffer between dead and living substances, andthus, between mechanical hard and soft

material. Pulp is the vital layer of the tooth

which delivers needed nutrients and bloodsupply to the tooth for growth and

development.4

The enamel is the primary

armor of the tooth. It is one of the hardest

biological substances is the enamel. Enamelhas hardness greater than that of bones. The

Knoop Hardness Number assigned to

enamel is in the range of 340 to 431kg/mm

2.2

Enamel is entirely composed of

calcium salts which are important in

composite bonding process.

Formation of Caries (cavities)



The figure above shows the tooth decay

process from absolute healthy tooth to a

fracture. The first tooth is a health tooth.The second tooth shows the first sign of

demineralization of the enamel layer. Thethird tooth shows the results of enamel

breakdown. The forth tooth has had an

amalgam filler applied to it; however, the

demineralization of the enamel has not beenaddressed which are visible in the fifth tooth

and leading to a fracture. Had thedemineralization been address the toothcould have been saved from further decay.

The mechanism which causes the

demineralization of the enamel layer isshown below.

Figure 3: Demineralization of Enamel

It is at the surface of the tooth or the

enamel which is the hardest and most

mineralized substance in the body and wherethe formations of caries occur. Caries are an

infectious disease that destroys the toothwhich is caused by bacteria and

carbohydrate containing foods.6

Bacteria

forms on and around teeth in the form of a

thin bio-film known as plaque which ismade up of millions of bacteria which

adhere to the tooth’s surface. Not all bacteria contribute to the formation of teethcaries. Streptococcus mutants, lactobacillus

casei, acidophilus and actinomyces

naeslunddii are the common carie causingbacteria

7These bacteria seek carbohydrates

carries. The figures below8

show the

formation of the lactic acid. This is the acid

which causes the pH on the tooth’s surfaceto drop. Before the intake of any foods, the

pH level in the mouth is slightly more acidicthan water, (6.2 – 7.0).

9When the pH range

is between 5.2-5.5, the enamel begins to be

dissolved and the exposure of these foods

promotes an acid attack of approximatelytwenty minutes after eating. The millions of

bacteria that reside on the surface of theteeth ferment the sugar we intake to formlactic acid which in-turn attacks the enamel.

The demineralization of the enamel is

actually caused by the hydrogen ion produced by the lactic acid.

Figure 4: Sucrose8



Figure 6: Glycolysis

Figure 7: Formation of Lactic Acid8

The two ways in which caries

develop are trough pits and fissures which

are grooves that are visible on the top biting

f f h b k h Thi h

surface breaks down the enamel and the acid

destroys the layer.Once a carie has formed, it is the

dentist’s job to clean and apply filler to it.

There are two categories of fillings which

are direct restorations (amalgam,composites, glass ionomers and resin

ionomers), and indirect restorations (all porcelain (ceramic), porcelain fused tometal, gold alloy (high noble) base metal

alloys (non-noble). Due to cost of the

material involved, direct restorations are themore common of the two types. Direct

fillings can be subcategorized into silver

amalgam, composite, and temporary filling

materials.

Amalgam Fillings

Amalgam restorations have beenused for 180 years.

10Amalgam fillings are

h h d f fill l b i



low concentration of amalgam (before

1963)11

, caused the amalgam to weaken via

corrosion because they contained gamma 2 phase (Ag3Sn), as shown in figure 11.

2

Figure 8: Restored and repaired amalgam restoration.11

(The American National Standards Institute

(ANSI) along with the American DentalAssociation (ADA) requires that amalgam

alloys are mainly comprised of silver andtin.

2

Figure 9: Elements used to make amalgam.1

Zinc is incorporated into the amalgam to

improve its clinical performance.12-14

Dental

amalgam with mercury are described by themetallurgical phases (silver-tin phase

diagram)52.

Figure 10: Symbols and Stoichiometry of Phases that are

Involved in Setting of Dental Amalgams are referred to the

mixture of the two metallic elements by a Greek letter.2

The Greek letters correspond to the symbolsfound in the phase diagram for each alloysystem

1. Amalgam fillings are extremely

durable, long lasting and not likely to break.

Amalgams have been known withstandmultiple years of chewing stress. The silver-

tin phase diagram indicates that when an

alloy contains 27% tin (Sn). Tin is cooled

below 480o

C, Ag3Sn the gamma phase in thediagram is produced. Silver-tin compound

is a key compound in this specific amalgam

which combines with mercury to obtain the properties and characteristics sought. The

silver-tin compound forms over a verynarrow composition range. The silver

content for silver-tin amalgam is 73%, the

tin content is approximately 26% and 30%of the remaining elements used for the

silver-tin amalgam are silver, copper, and

zinc. If the tin concentration is less than26%, the β phase which is a solid solution of

silver and tin forms



properties are enhanced by the addition of

palladium in amalgams

.

Figure 11: Silver-tin phase diagram2 (λ is also referred to as

Ag3Sn. β is the solid solution of silver and tin. )

Amalgation (the process of mixingliquid mercury with one or more metals or

alloys to form an amalgam) occurs whenmercury contains the surface of the silver-tin

alloy particles. The various other elements

(copper, zinc, gold, mercury, palladium,indium and selenium)

1are not exactly

specified; however they must be in

concentrations less than the concentrations

of tin and silver.

Amalgam is made available to

dentists in a disposable vial as shown above.The mercury is kept separate from the

powdered particles and the mixing pellet bya thin film. The amalgam is prepared by a

method referred to as trituration (mixing of

mercury with the powder particles). When

the amalgam is triturated it has theconsistency similar to that of a paste. When

the triturated amalgam is removed from thevial it may be further worked by the dentistusing a spatula.

The dentist is required to mold the surface of

the amalgam filling to reduce the tensilestress caused by biting forces. Amalgams

are self sealing, when amalgam is applied to

the tooth, corrosion occurs which fills

microscopic voids between tooth and filling.

Figure 13: The general amalgamation reaction. (λ 2 is also

referred to as Sn7-8Hg. λ is also referred to as Ag3Sn. β is the

solid solution of silver and tin. )

The physical properties of the

hardened amalgam depend on theconcentrations of each microstructural

phase. If the percentage composition of tinis >30% or <26% it is detrimental to theamalgam. The source of amalgam’s

strength is due to the Ag3Sn rather then the

tin. The setting time or the amount of timerequired to fill the carie is shortened by



Figure 14: A-D are schematic drawings illustrating thesequence of development of amalgam microstructure when

lathe-cut low-copper alloy particles are mixed with mercury.

(A) Dissolution of silver and tin into mercury. (B)

Precipitation of γ1 crystals in the mercury. (C) Consumption

of the remaining mercury by growth of γ1 and γ2 particles. (D)

Amalgam when finally set.2

The bond strengths have been

reviewed in many clinical studies which

indicate they are about 12 to 15 megapascals(MPa).

11Summitt’s group has reported an

average bond strength of 27 MPa.15

The

larger bond strength was reached byrefrigeration of the bonding material is the

appointed source which can be the source of

the unusual bond strength of 27 MPa.Bonding is emphasized with amalgams

because it offers sealing properties which isthe primary deter to microleackage. Acid

etching of tooth’s surface is done with phosphoric acid in various concentrations to

deter microleackage.

Figure 15: Mechanism of bonding amalgam to tooth structure.1

Figure 16: Scanning electron photomicrograph of interface

between bonding agent and dental amalgam.1

Th t i t t ti th t



degree of marginal deterioration, hence the

higher the creep magnitude, the greater the

degree of marginal deterioration.

16

Asreported by Mahler and group

17the two

major factors of corrosion and creep are thedeterminants of the amalgam behavior

which are best explained by the final

concentration of mercury. The higher the

concentration of mercury in an amalgamincreases the possibility of the creep. Creep

is not a good predictor of marginal fracture.As you can clearly see in figure 5,

the amalgam fillings are easily identifiable

in one’s mouth. In clinical practice, healthy

tooth must be removed to allocate theneeded space for the amalgam filling to hold

it securely in place. Amalgam fillings can

corrode over time which may lead to slight

discoloration of the area of contact to theamalgam. Traditional amalgam fillings do

not necessarily bond to teeth but rather sit in

the enlarged cavity which explains thereason of why healthy tooth is required to be

removed. Sometimes people may be

allergic to mercury or be concerned about itseffects. The mercury in amalgam has a very

small tendency to vaporize when chewing of food especially hard foods occurs. Research

supports the amount of mercury exposed

from fillings is comparable to what peopleget from other sources in the environment.

18

To address these concerns alternative filling

are also available for slightly higher cost and

require a lengthier setting time.

Figure 17: Estimated human mercury exposure reported in

1991.18

Composites Resins and Cements

Composite resins are a mixture of plastic and fine glass particles and are

generally applicable for small and largefillings for front teeth or the visible parts of

teeth & now by popular demands rear teeth.

Composite resin tends to hold up for approximately five years. Composite

fillings or inlays are not noticeable since

they can be matched to the tooth color selected by the dentist. Such a filling can be

completed in one visit and an inlay may

require two visits to complete. Compositefillings bond directly to the tooth via ionic

bonding which makes the tooth structurally

stronger than the amalgam which is a filling

pushed into the carie. Less drilling is

involved with the composite fillings becauseit is not necessary to create space to hold the

filling securely. The bonding process holdsthe composite resin in the tooth. Often

times indirect composite resin can are

combined with glass ionomers to provide the



methacrylate group capable of

copolymerizing with the unfilled resin of a

composite. The R refers to the spacer ((CH2)3) group. The X refers to the

OSi(OH)3 or the group capable of chemically reacting with the surface. These

three sub units combined together making

up the M-R-X structure of the bonding

agent.

Figure 18: γ-methacryloxypropyltrimethoxysilane, a typical

silane which is used as a coupling agent with composite fillings.

The commonly used dental

composite is bis-GMA.

Figure 19: 2 methyl 2 Propenoic acid (1

methacrylate. The core of the two aromatic

groups reduces its ability to rotate during

polymerization. The two diagrams belowshow the steric stress caused by the two

aromatic rings where the chain is forced to bring its two methacrylate groups at

opposite ends of the chain together.

Figure 20: Stick model of bis-GMA.

Figure 21: Ball and stick model of bis-GMA.

Like bis-GMA, all methacrylate monomers must

be diluted because of their viscosity. Diluting

methacrylate monomers brings the viscosity of the



agent.1, 2

Materials such as activation

initiators, polymerization inhibitors and

others that enhance the performance,appearance, and durability are also

incorporated into the composite.2

The teethare etched with phosphoric acid. The

etching process prepares the teeth to allow

the composite resin to bond. There are

many types of bonding agents available asshown the diagrams below.

Figure 22: Amino-carboxylate based bonding

agent (NPG-GMA)

Figure 24: Phosphate based bonding agent

The activator-indicator system converts the

soft resin paste into a moldable filling and

then to a hard material and finally a fillingwhich can withstand biting.

2The

polymerization inhibitors prolong the shelf

life of the composite.2

The coupling agent is vital that filler

particles to bonded to the resin matrix, thecoupling agent allows a flexible polymer

matrix to address the concern of stress upon

curing.2

Titanates and zirconates are other

coupling agents which can be used.Organosilanes such as γ-

methacryloxypropyl trimethoxysilane aremore commonly used simply because themethoxy groups (-OCH3) under go

hydrolysis to the silanol groups (-Si-OH)

which bonds with the resin when polymerized which completes the coupling

process.2

Composites are light activated or

chemically activated. Blue light with awave length of 470-nm is used in the light

activation process. The blue light is

absorbed by a photo-activator which isincorporated into the composite by the

f t2

O i i t i i



Figure 25: Camphorquinone (CQ)2

The camphorquinone brings the composite

paste to a slight yellow contrast making it

difficult for the dentist to obtain the proper

shade to match the other teeth. Thechemical activation is done at room

temperature. An organic amine reacts with

an organic peroxide to produce free radicalsthat attack the carbon double bonds allowing

for the polymerization process to begin.

Figure 26: The light-cure process gets activated when the

What’s free about free

radicals?

Why start a reaction in your mouth? There are three steps to free radicalpolymerization reactions which are initiation,propagation, and termination. Free radicalmolecules can be typically generated by achemical, heat, visible light, ultraviolet light, or

energy transfer from another compounds whichacts as a free radical. In dentistry, chemicalagents, heat, and visible light are used as theinitiators to start the reaction. Chemical initiatorsare the most common used in the profession.

Initiation is the first step in the freeradical polymerization reactions. The initiationstep is started off by an external energy sourcewhich breaks a bond to produce the free

radical(s). Free radical can be an atom or agroup of atoms (a compound) with an unpairedshared electron that is used to initiate the

sequences of reaction. R• can be any freeradical.

To better explain the initiation stage, thedisassociation of hydrochloric acid to hydrogenand calcium is shown in the reaction below.

H Cl H Cl

Heterolytic Bond Cleavage

Figure 27: Heterolytic Cleavage

In the above reaction mechanism, the covalent

bond in the hydrochloric acid is broken whichresults H+ and Cl-. Two bard curved arrow isused to point to the chlorine in the reaction toindicate that chlorine will have two unsharedelectrons. When electrons are distributedunevenly, in the initiation stage, such a reactionis referred to as a heterolytic bond cleavage.



Cl Cl

Homolytic Bond Cleavage

Cl Cl

Figure 28: Homolytic Bond Cleavage

The disassociation of molecular chlorine to

produce 2Cl• is a homolitic bond cleavage.

Notice that the single barbed arrows are used toshow the distribution of the electron pair. In ahomolytic bond cleavage, once the bond isbroken, one electron is distributed to each of thechlorines.

Your dentist uses one of three types of initiators to start a free radical polymerizationreaction.

O

O

O

O

O

O

2

benzoyl peroxide benzoylradical

heat

Figure 29: Benzoyl peroxideÆ Denzoyl radical

Sufficient free radicals for polymerization may beproduced at room temperatures by the reactionof a heat or chemical accelerator. Followed by

this initiation stage is the quick addition of othermonomer molecules to the free radical and theshifting of the free electron to the end of thegrowing chain.

The initiation of a methyl methacrylate molecule(Figure 20).

Figure 30: Initiation of methyl methacrylate molecule. As the

unpaired electron of the free radical approaches the methyl

methacrylate molecule, one of the electrons in the double bond

is attracted to the free radical to form an electron pair and a

covalent bond between the free radical and the monomer

molecule. In the process of forming these bonds, free radicalmolecules are created.2

The initiation of a dental resin, methylmethacrylate explained; as the unpaired electronof the free radical approaches the methylmethacrylate molecule (A & B), one of theelectrons in the double bond is attracted to thefree radical to form an electron pair and acovalent bond between the free radical and the

monomer molecule (C & D). When thishappens, the remaining unpaired electronmakes the new molecule a free radical (D).

The free radial-forming chemical used tostart the polymerization is not a catalyst. This isbecause it enters into the chemical reaction andbecomes apart of the final chemical compound.It is more accurately called an initiator because itis used to start the reaction. Many substances

are able to produce free radicals and are potentinitiator s for the polymerization of poly(methylmethacrylate) and other methacrylate-typeresins used in dentistry.

Another type of induction system ischemically activated at the ambient oraltemperature. This type of system consists of at



room temperature. Since the presence of aminereduces the thermal energy required to breakthe initiator into free radicals at ambient

temperature, this reaction is considered to beheat activated.

Finally, the light-activated inductionsystem is the third type. Photons from a lightsource activate the initiator to generate freeradicals. These free radicals can initiate thepolymerization process. When this system wasfirst introduced to dentistry, ultraviolet (UV) lightwas used; however, due to other health

complications visible light activated initiatorsystems were developed.

Figure 31: The Electromagnetic Spectrum19

Camporquione and an organic aminesuch as dimethlaminoethylmethacrylategenerate free radicals when irradiated by light inthe blue to violet region. A light source with awavelength of about 470-nm is needed to triggerthis reaction. Factors such as light intensity,angle if illumination, and distance of resin fromthe light source can affect the number of freeradicals that are formed which is why this type of

induction system is considered to be techniquesensitive.

Figure 32: Propagation stage.

When the initiated molecule reacts with the

methyl methacrylate molecule, the electronsattack the double bond of the methyl

methacrylate molecule. This process leads

to what is known as the chain growth.2

Figure 33: Chain transfer.

The process when the radical approaches the

methyl methacrylate molecule and offers a

hydrogen atom is referred to as chaintransfer. The chain transfer causes the free

radical to rearrange to create a carbon

double bond to become unreactive.2



Figure 34: Second type of chain transfer.

When a propagating chain has interactedwith a passive segment as formed in figure

23, another type of chain transfer hasoccurred. During this type of interaction the

passive segment becomes active and the

active segment becomes passive.2

Figure 35: Termination.

The final stage in the free radical polymerization is termination. Termination

is reached when all of the free radicals have

interacted and formed covalent bonds. 2 Free radical polymerization is how

composites reach their high durability. The

polymerized resin is highly cross-linked

because of the dysfunctional carbon doubleb d Th l i ti f th

activation or by external energy activation

such as heat or light. Considering the

product produced at the termination stage, ahypothesis can be made that the carbonyl

groups alter to create cross linkage, whichleads to high resonance along the terminal

ends of the highly conjugated structure. The

aromatic rings at either terminal ends

provide the composite resin tensile strengthand make the resin bite worthy.

Composite resins have becomestronger and more resistant to wear.Polymer research has not developed a

composite with the similar characteristics to

that of amalgam. The use of compositefillers increases the chair time of a patient by

approximately 10 to 20 minutes or longer.

When large carries have formed, composite

fillings may not last as long as amalgamfillings.

A major concern which has dentists

resisting the use of composite fillings is their ability to shrink after curing. Often times,

fillers can be added to reduce the shrinkage

of the composite; however, shrinkage cannot be prevented.

You are probably familiar with

cement and how it is used as a material inconstruction work. Just look around you

when you are outside and bring your

attention to the structures made of concrete.

How is cement made? What are itschemical properties? What is happening

chemically to make it hard and strong?



hydrates. This hydraulic powder type

mixture solidifies when combined with

water. There are several ways in which

portland cement is manufactured.Regardless of which method is used, they all

require similar chemical components and

raw materials. Concrete is approximately

70% to 80% aggregate (filler material suchas various grade rocks and/or sand)

depending on which brand and type of concrete cement. The chemical componentslimestone (CaCO3), clay, shale (2SiO2 y

Al2O3), iron oxide (Fe2O3), silica sand

(SiO2).20, 21

The afore mentioned materialsare placed in a kiln and heated

approximately 1400 to 1700oC. 3CaO ●

SiO2, 2CaO ● SiO2, 3CaO ● Al2O3, 4CaO ●

Al2O3 ● Fe2O3, are formed when the rawmaterials is heated to such extreme

temperature which allows for them to react

chemically. The product at the end of thisheating process is the cement which is

available for purchase at your local

hardware store.

Figure 36: Cement Factory

The described cement manufacturing

process can be reviewed in depth at

http://www.cement.org/basics/images/flasht

our html22

Figure 37: Cement hydration21

Figure 27 provides a visualrepresentation of cement hydration. The

process begins with dissolution of grain

particles followed by a solution of ionic

concentration. Then compounds begin to

form and upon reacting the point of saturation, solids begin to precipitate out as

the products of the hydration process.21

A chemical reaction occurs when

water and cement are mixed together, in

chemistry we refer to this type of reaction asa hydration. Cement hydration is an

exothermic reaction. The chemical

compounds that harden the quickest aretricalcium aluminate and tetracalciumaluminoferrite. Gypsum is added to prevent

the quick curing of the cement caused by

tricalcium aluminate. Heat is generated bythe hydration of tricalcium aluminate. The

http://www.cement.org/basics/images/flashtour.html






cement to strengthen over several days as it

fully cures.

So what actually is occurring chemically?

Reaction 1: 2C3S + 7H Æ C3S2H8 + 3CH

∆H = -500 J/g21

Reaction 2: 2C2S + 7H Æ C3S2H8 + CH

∆H = -250 J/g21

The two reactions above are called

hydration of calcium silicate reactions which produce calcium silicate hydrate and C-H.Reaction 2 produces half the amount of heat

that reaction 2 produces. Reactions 1 and 2

are the source of the cement’s strength of thecement.

Reaction 3: 2C3A + 3CSH2 + 26H Æ

C6AS3H32 ∆H = -1,350 J/g21

The hydration of the calcium

aluminates is the source of this exothermicreaction. This reaction also produces

needle-like interlocking structures which

consume water, contributing to stiffening of mixture the and more resistant against

sulfate attack.22 Figures 2 and 3 illustrate the

hydration of calcium aluminates. When

inspected closely hexagonal plates areformed in what geologist refer to as

“rosettes” during the initiation of the

hydration process. As the hydration process

continues, the hexagonal plates grow and asusceptible to sulfate attack.

The cement strength is based on

multiple things, some of which aretemperature, quality of cement and cement

water ratio and cement to aggregate ratio.

cement may look and feel as though it is

fully cured however it is still polymerizing.

We can say that after cement is allowed tosettle for 90 days it is fully cured or has fully

hardened.22

Most dental cements are supplied as

a liquid and a powder component. Cements

must exhibit a low viscosity to flow along

the interfaces between hard tissue and afixed prosthesis and they must be capable of

wetting both surfaces to hold the prosthesisin place. The advances in resin chemistryfor applications in dentistry have led to the

development of resin based composite

cements called rein cements. Dentalcements are classified according to their

chemical composition and bond strength to

tooth structure when bonded with adhesives.

Dental composites are being used to

restore teeth regardless of the location of their location and type of tooth in the mouth.

Individuals choose to have composite resin

filler rather then the amalgam filler mainlydue to the physical appearance of the

unnoticeable composition of the filler. The

term composite in dentistry and materialscience has varied meanings. In material

science a composite is a material comprised

of two different phases and in dentistry theterm is referred to as a particular group of

materials.23

The group of materials all have

two distinctive features about their

structures. These materials are monomers

which are based on bulky methacrylatemonomers that set by free radical

polymerization and are filled with a finelygrained type of ceramic. The problems

linked to the usage of 2-methyl-2-propenoic

acid (1-methylethylidene) bis (4 1-



Figure 38: Organic Monomers used in dental

composite resin filling materials.23

The use of the large methacrylate chain hasone disadvantage which is their high

viscosities. In all applications for dental

usage these methacrylate monomers must bediluted with either ethylene glycol

dimethacrylate (EGDMA) or trethylene

glycol dimethacrylate (TEGDMA). Using

smaller monomers as diluents to obtain aviscosity which is much more comparable to

work with; they have a larger

polymerization shrinkage which increasesthe possible occurrences of micorleakages

and fractures. It is best to reduce the

dilution of Bis-GMA to greatly reduce theshrinkage factor; however, shrinkage cannot

be totally avoided considering chemical

composition of the composite resin.

Figure 40: Ball and stick model of triethylene

glycol dimethacrylate (TEGDMA).

The shrinkage experienced by the

methacrylates was seen to decrease as the

molecular weight increased. Many researchgroups have confirmed that the polymerization shrinkage and molecular

volume indicate that they are inversely

proportional each other.24-26

Figure 41: Composition of dental cements.

When using methacrylate monomersthe polymerization process is never

complete. The polymer contains many

unreacted double bonds which range between 5 to 45% of the original

concentration.23, 27, 28

The number of

unreacted double bonds are based on severalfactors one of which is the composition of

the monomer mixture.29, 30

One method



resin is applied to the prepared carie in thin

films and cured (hardened) to reduce theshrinkage caused by polymerization.

The crosslinking of a polymer

structure is depended on the composition of the monomer from which the polymer was

created. For example TEGDMA & Bis-

GMA, result in an extremely high crosslink

density. Asmussen’s study shows that thereacted double bonds increase with the

amounts of bis-GMA in the bis-GMA &TEGDMA mixture.

27This study also

indicates that the larger the percentage of

remaining double bonds, the greater the

chances of post shrinkage.27

The unreacteddouble bonds highlighted in the termination

stage below allow for post polymerization to

occur.

Figure 42: Unreacted double bonds

The information collected about the

reacted double bonds, (RDB) was useful in

order to understanding that the relativeindication of low crosslink density and

degree of softening of the composite sample being in ethanol. The more corsslinking thatoccurs, the harder the composite resin will

be.

Figure 43: Monomer composition (mol%) remaining double

bonds and Wallace hardness (HW, μm) before and after ethanol

storage of the resulting polymers.

Figure 44: Content of CQ and CEMA (weight %)

in a 60:40 (mol:mol) bis-GMA:TEGDMA

monomer mixutre. Remaining double bonds

(RDB%) and Wallace hardness (HW, μm) before

and after ethanol storage of the resulting

polymers.

Post-ShrinkageDelphine Truffier-Boutry et al. have

reported that the post-shrinkage is mainly

due to the mobility of the chain and as

mentioned earlier the continual

polymerization process. The chemicalexplanation has been narrowed down to two

sources which (1) are the free radicals and

the double bond of the methacrylate groupsor (2) free radicals causing the effect.

Bergstrom et al. has arrived to the

conclusion that polymerization could not possibly continue at 36

oC.

31Truffier-Boutry

states that many studies have been

conducted to obtain an understanding if the

initiation step, with different lamps which is

a possible cause of the post polymerization.

32

The use of dental cement as arestorative material began with silicate

cement. Silicate cement is based on silicate

l d h h i id Th l f



placement of a third material called a luting

agent (a viscous material placed betweentooth structure and prosthesis that hardens

through chemical reactions to firmly attach

the prosthesis to the tooth structure)2

thatflows within the rough surfaces and sets to a

solid form.

Cement paste must coat the entire

inner surface of the crown and extendslightly. This is done to reassure that the

space between the crown and the tooth iscompletely sealed.

Figure 45: A microscopic image of the prosthesis interfaces.(A) Shows the roughness of the two surfaces to be bonded and

the imperfections. (B) Shows the two surfaces pressed against

each other without the cement layer. (C) Shows the two

surfaces and an intermediate layer which can be either cement

or an adhesive. (D) Shows possible voids due to the inability of

the intermediate layer to wet the surfaces.2

The State of the Art Composite Resin

Considering the many types of fillers

currently being used in dentistry, scientist,chemists and dentists are still in search for the ideal fillers to reduce shrinkage and

stress to best be used as a filling in the

mouth. This quest of scientifically creating

l b d filli h k D

Dr. Laine reports in his review that

the newly created cube shaped structureswere derived from polyhedral oligomeric

and octasilicate anions (OSA).33 The

interesting aspect of the cubed structure of the octafunctional octasilsesquioxane is that

they have a diameter in the rage of 1.2 – 1.4

nanometers.33

Figure 46: Typical size & volume of cube.34-36

Water is essential to the formation these

cubes.33, 37

Their structure allows them to

have a functional group in each octant either

on opposite or completely orthogonal toeach other. Very limited amount of

knowledge has been gained in understanding

the cube structures.The research conducted by Laine

explains that nanocomposites have to be

made in a specific way based on the purposethe composite is to serve in the oral cavity,

this is to address the shrinkage factors whichneed to be considered in all composites.

The ideal composite would be created with both hard and soft materials. The hard

materials would act as the foundation of the

it d th ft t i l ld



Figure 47: Example of organic tether.33

Figure 48: Example of an organic tether.33




The composites would be defined on the

size and spatial relationships.33

If theorganic tethers linking the cubes are short

then they would allow for the possibility to

create a microporous composite.

Figure 53: Continuous organic phase.

Figure 54: The blackened squares are the potential for

controlled microporosity. Nanocomposite morphology which

is disconnected. Nanocomposite with perfectly defined

interfacial interactions.33



understood; however it is currently being

further researched and studied.33

Figure 55: Schematic process of how the crosslinking occurs. Crosslinked polymer by hydrosilylation of

oppositely functionalized cubes.33

Laine raises a very interesting point in his

review33

about the epoxies which had beentested for shrinkage. Dodecyl methacrylate

(DDM), was reacted with various epoxies

and varying ratios of epoxy:amine at 150oC,

the temperature that cures resin. Based onthe results of these assessments it was

determined that the curing chemistry of

epoxy resin, two stoichiometries provedvery minimal structural abnormalities which

are when an epoxy reacts once with an NH2

or when two epoxy groups react with an NH2. This reaction is considered to be a

defect because when the reaction proceeds,the resin viscosity increases where the

complete reaction is inadvertentlyimpossible. He also reports two scientific

methods to place reactive methacrylate

groups on the cubes with contaminant loss

desired addition across the triple bond. At

room temperature these materials areliquids, they cure by absorption of heat or a

photochemical.

Choi’s group has also further

researched the cube structures. Similar toLaine’s groups Choi was not able to

completely explain the chemistry; however

they have realized that the amount of diaminodiphenylmethane (DDM) used to

react with

octakis(glycidyldimethylsiloxy)octasilsesquioxane (OG) effects how the cross linking

takes place.



groups is 2 to 1 resulting in the organic

tether to link up to four cubes.

Figure 57: Formation of nanocomposite.38

Not completely state of the art;

however, further research by Hiroyuki

Okamura and his team investigated on theformulation of a dental composite resin tofurther understand low-shrinkage and low-

viscosity monomers. Their motivation of

achieving such a monomer was supported bythe fact that the task seemed to be

achievable by using newly developed low-

viscosity and low-shrinkage light curing

monomers.39 Okamura and his groupreported that each composite resin indicated

an overall setting shrinkage of more than80% in the first two minutes, the composites

being exposed or irritated by the visible

light. The data collected by Okamura and

group state that a significant difference wasnoted in the main effect of the monomer.

The shrinkage was recorded to be the

highest when the filler content was increasedgradually starting at 50% of the composition

of the composite resin.

Figure 58: Change of setting shrinkage of

composite resin.39

The setting shrinkage decreased linearly

with an increase in filler content. The

composition of monomer mixtures used inthis specific study is represented in the

figure below.Figure 56 shows the change in

setting shrinkage of composite resins with

the monomer composition. Based on this

study done, it seems that the new monomer

mixtures tended to cause small settingshrinkage. This small shrinkage may have

been a result of the polyfunctional

monomers and the small intermolecular distance. It is hypothesized that when

polymerization occurred the decreasing



Figure 59: The composition of monomer mixtures used in Okamura’s study.39

amount of intermolecular distance of themonomer would be comparable to the

smaller molecule yet the decrease in the

intermolecular space would be yet even

smaller.39

Conclusion

Having conducted this investigation

has revealed much in terms of the future of composite resin and the improvement which

are to come.

The composite Laine’s group has

extensively studied and researched can bethe ideal composite resin; however, there

needs to be further studies conducted in

terms of its biocompatibility in the oralenvironment. In regards to oral environment

studies there needs to a focus on the various

cubed structures which would address theshrinkage concerns of dentists. The

crosslinking of the silsesquioxanes with the

tethers is also another advantageous

attribute. The crosslinking stabilizes thesilsesquoxanes keeping the cubes from

continuously rearranging themselves.

There are many studies beingconducted which all aim to reduce the

polymerization shrinkage in some way.

Various groups are performing further

studies to advance the usage of thecomposite resin into the application of molar

teeth is varying the ratio of bis-GMA toEDGMA or the ratio of bis-GMA to

TEGDMA.30, 40, 41

Altering the ratio of thecomposite resin and diluents, has an affect



inorganic particles reduces the shrinkage

caused by acting as fillers to compositeresin.

Another aspect to be considered for

further research is the bonding agent used toset all composites (MRX complex). The

chemistry which supports this complex is

not completely understood therefore further

study and research can lead to a clear understanding of the chemistry related to the

bonding agent.

There is a vast amount of research

surrounding composite resins waiting to beexplored and understood. Even though bis-

GMA is a commonly used dental composite

resin, the chemistry needs to be further understood in regards to reducing shrinkage

and maintaining an acceptable hardness. As

mentioned afore chemists and dentist are

working to gain the needed insight to better the bis-GMA based composite resin and also

explore the options to the ideal compositeresin.



Bibliography

1. John M. Powers, R. L. S., Craig's Restorative Dental Materials. Twelfth ed.; Mosby

Elsevier: St. Louis, 2006.2. Anusavice, K. J., Phillips' Science of Dental Material. 11th ed.; Saunders: St. Louis,

2003.

3. Powers, J. M., Tooth Anatomy. Medline Plus200.

4. Powers, J. M., Tooth Anatomy. Medline Plus2007.5. Bratthall, D. Dental Carries - what is that?

http://www.db.od.mah.se/car/data/cariesser.html (August 5, 2007),6. Jacobs, J. http://www.nlm.nih.gov/medlineplus/ency/imagepages/1121.htm.http://www.nlm.nih.gov/medlineplus/ency/article/001055.htm (July 22),

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9. Ellie, About Mouth Acids. 2007.

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http://www.db.od.mah.se/car/data/cariesser.html

http://www.nlm.nih.gov/medlineplus/ency/imagepages/1121.htm

http://www.nlm.nih.gov/medlineplus/ency/article/001055.htm

http://www.lindt.ch/public/canada/chocomania/dental.pdf

http://www.elmhurst.edu/~chm/vchembook/548toothdecay.html

http://www.fda.gov/bbs/topics/CONSUMER/CON0266g.html

http://www.lib.umich.edu/dentlib/Dental_tables/Creep.html

http://mynasadata.larc.nasa.gov/ElectroMag.html

http://training.ce.washington.edu/PGI/

http://mynasadata.larc.nasa.gov/ElectroMag.html

http://www.lib.umich.edu/dentlib/Dental_tables/Creep.html

http://www.fda.gov/bbs/topics/CONSUMER/CON0266g.html

http://www.elmhurst.edu/~chm/vchembook/548toothdecay.html

http://www.lindt.ch/public/canada/chocomania/dental.pdf

http://www.nlm.nih.gov/medlineplus/ency/article/001055.htm

http://www.nlm.nih.gov/medlineplus/ency/imagepages/1121.htm

http://www.db.od.mah.se/car/data/cariesser.html



24. Matsukawa S, H. T., Nemoto K, Development of high-toughness resin for dental

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27. Erik Asmussen, A. P., Influence of selected components on crosslink density in polymer

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28. Ferracane JL, M. J., Condon JR, Todd R., Wear and marginal breakdown of compositeswith various degrees of cure. J Dent Res1997, 76, 1508-1516.

29. E, A., Factors affecting the quality of remaining double bonds in restorative resin polymers. Scand J Dent Res1982, 90, 490-496.30. J L Feracane, E. H. G., The effect of resin formulation on the degree of conversion and

mechanical properties of dental restorative resins. J Biomed Matter Res1986, 20, 121-131.

31. Bergstrom J, V. G., Temperatures of the oral cavity in 50 healthy students Sewd Dent1971, 64, 157-64.

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octasilsesquioxanes. J ournal of Materials Chemistry2005, 15, (35-36), 3725-3744.

34. N. Maxim, P. C. M. M. M., P. J. Kooyman, J. H. M. C. van Wolput, R. A. van Santen andH. C. l. Abbenhuis, Mg-Si-O and Al-Si-O Materials Derived from Metal Silsesquioxanes. Chem.Mater. 2001, 13, 2958.

35. R. H. Baney, M. I., A. Sakaibara and T. Suzuki, Silsesquioxanes. CHem. Rev. 1997, 95,(95), 1409-1430.

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37. I. Hasegawa, S. S., K. Kuroda and C. Kato, The Effect of Tetramethylammonium Ions on

the Distribution of Silicate Species in the Methanolic Solutions. J . Mol. Liq. 1978, (34), 307-315.38. Choi, J.; Yee, A. F.; Laine, R. M., Organic/Inorganic Hybrid Composites from Cubic

Silsesquioxanes. Epoxy resins of octa(dimethylsiloxyethylcyclohexylepoxide) silsesquioxane.Macromolecules2003, 36, (15), 5666-5682.

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Utilizing Low-Shrinkage and Low-Viscous Monomers. Dental Materials J ournal 2006, 25, (3),437-444.

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Appendix A: Lesson Overview

Teacher: Vishal Patel School: Mastery Charter High SchoolClass: Chemistry/Science Topic: (Polymerization/HydrogenBonding) Academic Level: Honors Chemistry/AP Chemistry

______________________________________________________________________________ Title:

Which type of Fillings would you prefer?

______________________________________________________________________________ Pennsylvania State Standard:1

3.2.10.A: Applying knowledge and understanding about the nature of scientific and technologicalknowledge.

• Compare and contrast scientific theories and beliefs.

• Know that science uses both direct and indirect observation means to study the world and

the universe.• Integrate new information into existing theories and explain implied results.

3.2.10.C: Apply the elements of scientific inquiry to solve problems.

• Generate questions about objects, organisms and/or events that can be answered throughscientific investigation.

• Evaluate the appropriateness of questions3.2.12.A: Evaluate the nature of scientific and technological knowledge.

•

Know and use the ongoing scientific processes to continually improve and better understandhow things work.3.2.10.B: Apply process knowledge and organize scientific and technological phenomena in varied ways.

• Describe materials using precise quantitative and qualitative skills based observations.

• Develop appropriate scientific experiments: raising questions, formulating hypothesis, testing controlled experiments, recognizing variables, manipulating variables, interpreting data, andproducing solutions.

• Use process skills to make inferences and predictions using controlled information and tocommunicate using space/time relationships, defining operationally.

3.4.10.A: Explain concepts about the structure and properties of matter.

• Explain the formation of compounds and their resulting properties using bonding theories

• Recognize formulas for compounds



• Examine the problem, rank all necessary information and all questions that must beanswered.

•

Propose and analyze a solution.• Communicate the process and evaluate and present the impacts of the solution.

3.2.12.D: Analyze and use the technological design process to solve problems.

• Assess all aspects of the problem prioritize the necessary information and formulatequestions that must be answered.

• Propose, develop & appraise the best solution and develop alternative solutions

• Implement and assess the solution redesigned and improve as necessary.

• Communicate and assess the process and evaluate and present the impacts of the solution.

Objective:

Students will be able to . . . .Explain variations in the chemical and physical properties of amalgam and composite fillings via aninquiry method.

Identify the three stages in polymerization (initiation, propagation, and termination).Explain the process of Hydrogen Bonding.

______________________________________________________________________________ Materials: (Be sure to have enough for the class.)

Day 1Copies of Daily Learning Log worksheets2

Large post-it sheets/newsprint paper

MarkersPhillips Science of Dental MaterialsRestorative Resins Pages 399-441Dental Amalgams Pages 495-543

Craig’s Dental MaterialResin Composite Restorative Materials Pages 190-212 Amalgam Pages 236-267

On-line resource

Published Journal articles Amalgam vs. Composite Resin: 1998, by Gordon J. Christensen.Posterior Composite Resins: The Materials and their Clinical Performance, by Karl F.Leinfelder

Copies of three mini-labs



One bag of Cheetos30 Half toothpicks55% Elmer’s glue solution in water

4% borax solution (sodium borate)Styrofoam cupsZip lock bagsFood colorsSeveral different polymer bottles

Day 3Daily Learning Log

White sheet of paperBlack sheet of paperCopies of Do Now Assignment

______________________________________________________________________________ Vocabulary: (There are the list of words which may need to be stress and explained to students.)

PolymersMacromoleculesInitiatorsMonomersCrosslinkers AmalgamCompositeResinCement

PolymerizationInitiationPropagation TerminationLight Curing



Which type of Fillings would you prefer?DAY 1

______________________________________________________________________________

Prep Teacher will write the following Do Now assignment on the board.We will be discussing amalgam and composite resin fillings. Fill in the Prior Knowledge section of the Daily Learning Log.

______________________________________________________________________________ Objective

Students will be able to. .Explain the two types of filler and the chemistry which is associated with each of them.Students will review journal articles, World Wide Web and text books to gather the information they need to use in their debate. ______________________________________________________________________________ Pennsylvania State Standard:3

3.2.10.A: Applying knowledge and understanding about the nature of scientific and technologicalknowledge.

• Compare and contrast scientific theories and beliefs.• Know that science uses both direct and indirect observation means to study the world and

the universe.

• Integrate new information into existing theories and explain implied results.3.2.10.C: Apply the elements of scientific inquiry to solve problems.

• Generate questions about objects, organisms and/or events that can be answered throughscientific investigation.

• Evaluate the appropriateness of questions3.2.12.A: Evaluate the nature of scientific and technological knowledge.

• Know and use the ongoing scientific processes to continually improve and better understandhow things work.

______________________________________________________________________________ Do Now: (5 MIN. Independent activity students complete upon entering classroom.)

Teacher will greet each student at the door, hand out the Daily Learning Log and monitor

classroom. Students are to work independently on the Do Now assignment. Students are notpermitted the use of any resources for the duration of this activity.

______________________________________________________________________________ Direction Instruction: (I do; What teacher will do to guide the students in the learning process.)



students per group). There should be areporter, script, group

monitor, and leader ineach group.

First Activity (10 MIN.)Lecture

• Provide students withbaseline information onamalgam and compositefillers.

• Have students who

have had fillers appliedin their mouths sharetheir experience. (Toobtain students’ attitudeabout science in the real word)

• Teacher is limiting formal lecture to 10-min. to allow

for inquiry learning to occur and to host a student centered classroom by allowing students toindependently investigate

• Pay attention to lectureand take notes.

Second Activity (25 MIN) • Explain the following to the groups.

• Each group will have a

different set of resources on amalgamor composite resinfillers. One group has web, test, & journals. Your task for the next25 minutes is to review the information and be

ready to report to theclass your findings/new learning.

• Each group will begiven a set of resourcesabout amalgam or

composite resin fillers. You are to review theresources in yourgroups.

• Each group is requiredto take notes from whatyou read; however, theresources are not to

leave the room.

(15 MIN) • Let students know thatthey may want to take

• Remain silent while theelected group reporter



class the groups’information.

• Emphasize polymerization andshrinkage. Explainthe process of polymerization.

• Explain hydrogenbonding and the roleit plays in thecomposite resin.

• Review teacher’snotes and stress the points of importanceto the class.

______________________________________________________________________________ Exit Assessment: (You do: How will you assess if the students acquired the skill for today)

Students will complete the last three sections of the Daily Learning Log and submit to teacher.

______________________________________________________________________________ Homework: (You do: An extension to the content covered in class.)

Teacher will distribute the lab for the following day for students to prepare pre-lab reports.

______________________________________________________________________________ Teacher Notes:

Limit direct instruction to ten minutes. Having the lecture limited to ten minutes will provide anample amount of time for teacher to provide the baseline information students will need to beginthinking about the types of filler; however, it will make them interested in the types of fillers toinvestigate them in small groups.In small groups the type of resource will be different for each group. The table below indicates theresource and what will be the groups focus.

Groups Number Type of Resource Type filler to focus on1 Dental Text Amalgam2 Dental Text Composite Resin Filler3 Journal Article Amalgam4 Journal Article Composite Resin Filler5 World Wide Web Amalgam



After the twenty-five minutes of small groups investigation, a selected reporter will report theirfindings to the whole class, where they will be required to answer questions their classmates haveabout the information they report to the class.

During the sharing of information, students will be taking notes to develop a deeper understanding of the information which is shared with their class makes. The Daily learning log will be handed in by all students. Daily Learning Log is used to assess thestudents’ understanding of composite resin and amalgam fillers and the chemistry associated witheach of them. The Daily Learning Log also allows students to relate daily topics to their lives, ask clarifying questions, and restate what was taught in class and how comfortable they are with thematerial. During the last five minutes students will be lead in an organized whole class discussion toclose the class with the highlighting the make points of the class.



EXPERIMENT 1 4

Crunch and Munch Lab

Desk Top Building of Polymer Chain Components

Objective: The objective of this lab is to introduce the concepts and vocabulary of "polymers" withsimple models.

Review of Scientific Principles:

Polymers (Greek-POLY...many and MEROS...parts) have existed since the beginning of life. Both"natural" and "synthetic" polymers are an integral part of our life. Most of the natural and syntheticmaterials with which we come in contact are wholly or partly polymeric in nature.

Polymers (plastics) are large molecules ( macromolecules ) made up of repeating units called "mers"or more correctly "monomers". These "units" are chemical molecules. To introduce the commonterms used in polymers, we will use the models shown in this desktop experiment.

Time: This laboratory experiment requires about 40 minutes.

Materials and Supplies:

30 half toothpicks

Procedure:

1. Remove the initiators from the bag that you were given. Record your bag number. Add atoothpick and than a monomer to each initiator. Continue to add toothpicks and monomersto chain until all the monomers have been used. (Don't eat the experiment.)

http://matse1.mse.uiuc.edu/polymers/glos.html#mac

http://matse1.mse.uiuc.edu/polymers/glos.html#mac



unstable groups are formed by tearing apart a normally stable molecule so that there is anunpaired electron (pairing produces stability) in some part of the chemical segment.

2. Using toothpicks, connect the partial chains together at the ends which do not have"initiators" located on them. Continue the connection until all the partial chains have beenused.

3. Using the ends of the crosslinker with the attached toothpick, connect the chains together(cross-link). The connection of chains together along their body is called cross-linking. Thesynthetic process has an origin as far back as "vulcanization" in which sulfur was used tocross-link natural rubber in making and patching tires. In later experiments, we will be using borax as a cross-linking agent.

Questions:

1. Describe (define) a polymer in your own words.2. Draw your polymer and the polymers of two other people who have different numbers on

their bags. It should be noted here that normal polymers have literally tens to hundreds of thousands of monomers making up a chain instead of the sparingly few that you have beengiven to use.

3. As the number (concentration) of initiators increase, what happens to the length of thechains? (Note: You will have to compare the above structure to those of other students.)

4. How (predict) do the "strength" and "flexibility" of the polymers change as the number(concentration) of cross-linkers increases.

a) A "branched polymer" is formed when one chain is attached along the body of anotherchain. A branched polymer resembles the branches of a tree. Redraw your structure so that itshows branching.

b) What did you have to do with one of the terminal ends in order to create the branching requested for your polymer?

5. Below is the structure of benzoyl peroxide (used in acne medicines). Separate the moleculeto show two identical free radicals.



6. Below is the polymer of PVC, Poly(Vinyl) Chloride. Circle the repeat unit of this if is wasmade from ethylene.



Teachers Copy

Teacher Notes:

Objective: The objective of this laboratory is to learn the vocabulary of polymer synthesis throughthe making of models. This is a very simplistic modeling lab. The terms used will have meaning andpurpose as a result of this desk top lab.


We will be using cheese snack foods to present models in addition polymerization and cross-linking

of the polymer chains. All of these materials may be obtained from a grocery or discount store.Starch or Styrofoam peanuts may be used instead of food products if the maturity of the class is inquestion.

Students at this point have no background for condensation polymerization and it is suggested thatnothing but its existence be noted at this time. A more "in-depth" presentation will be made later inthe module.

Free radicals are introduced as initiators to the polymerization process. The formation of a sampleradical and its action on a monomer may be described as:

In the presence of UV light or other high energy sources, a monomer may also form a radical. Inthis section the cross-linker and monomer were considered as totally different. This self initiating and/or self cross-linking of the monomer should not be presented to the student at this time. The



A popular example of a harmful radical is one formed by the types of Chloro-Fluoro-Carbons that we use as refrigerant gases.

Of course, the very reactive ozone of the ozone layer of the atmosphere may cause the samereaction, also forming the unstable radicals.

Time: The preparation time for this lab is about 30 minutes.

Procedure:

Three classes of bags should be filled and numbered as follows:

Bag # Cheese balls Cheese Puffs Cheeto Crunchies

1 4 20 2

2 7 20 4

3 10 20 7

Answers to Questions:

1. A high molecular weight macromolecule made up of multiple repeating units.

2. Students should have only one attachment on each initiator.3. The greater the number of initiators or concentration of initiators, the shorter will be the

length of the straight chain of the polymer.4. As the concentration of cross-linkers increase, the flexibility/fluidity of the polymers will

decrease. This explanation can be likened to the fact that as the number of steps on a ladderincrease, so will the stability of the ladder. Those students having an odd # of initiators willalready have a branched polymer in this model. In the normal polymerization "branching" will occur as part of the normal process regardless of the number of initiators. Students thathad an even number of initiators could do one of two things:a) they could remove one of the initiators from one of chains to make the connection.b) they could break one of the chains making a branch with each segment.



6.



EXPERIMENT 2 5

Slime Away

Cross-Linking Poly (vinyl alcohol) with Sodium Borate

Objective: The objective of this experiment is to explore the change in physical properties of apolymer as a result of cross-linking. The result of adding more cross-linking agents to a polymer isconsidered and another model of cross-linking is viewed.

Applications:

There are a number of uses of the PVA polymer we are studying:

1. They may be used in sheets to make bags to act as containers for pre-measured soap yousimply throw into a washing machine.

2. The PVA sheets may be made into larger bags to be used by hospitals as containers for thecotton cloth used in the operating rooms or to hold the bed linen or clothing of infectedpatients.

Time: This experiment will require approximately 15-20 minutes to run and clean up.


•

100 ml/group of poly (vinyl alcohol) 4%• 10 ml of sodium borate 4%• Styrofoam cups and wooden stir sticks (tongue depressors)• Zip lock bags or latex gloves (surgical)

General Safety Guidelines:

• Laboratory aprons and goggles should be worn in this experiment as in all procedures.

• Both the borax and the PVA will burn the eyes. Hands should be washed at the endof the experiment.



Procedure:

The polyvinyl alcohol and sodium borate are mixed together in approximately a 10 to 1 ratio.

1. 100 ml of the 4% poly (vinyl alcohol) is added to a Styrofoam cup .2. Food coloring can be added to the PVA in the cups to make different colors. Simple food

coloring is recommended. This coloring should be added before any of the borax solutionhas been added, or it can be added directly to the borax solution.

3. Add 10 ml of the 4% cross-linker (sodium borate) to each cup. Begin stirring the mixtureimmediately with your wooden tongue depressor.

4. Make observations as to what is occurring as the reaction proceeds.5. Within a couple of minutes the slime will be formed. Lift some of it out with the tongue

depressor and make your observations. Record your observations on your data sheet.6. Take some in your hand and stretch the slime slowly. Record your observations on your data

sheet.7. Repeat the stretching exercise only this time do it rapidly. Record your observations on your

data sheet. Compare the results of the two tests. The slime is non toxic and is safe to handle,so you can put it in a Zip-lock bag (or latex glove) and seal it to take home.

8. Follow good laboratory procedure and wash your hands with soap and water. It isrecommended that this procedure be followed whenever handling this material. Keep it inthe glove or bag until it is discarded. The sodium borate or PVA could burn your eyes.

9. Place a small amount of the PVA on a paper towel and set it off to the side to dry untiltomorrow. Upon returning to class the next day, record in the data section your observationof the slime.

Data and Analysis:

Observation of the PVA before the sodium borate is added:

Observation of the PVA after the sodium borate is added:

Observation of stretching the cross-linked PVA slowly :

Observation of stretching the cross-linked PVA rapidly :

Observation of the cross-linked PVA left out in the air overnight:



Questions:

1. What are the physical properties that change as a result of the addition of sodium borate to

the poly (vinyl alcohol).2. What would be the effect of adding more sodium borate to your cup (your thoughts only)?3. After making the observations on the dried PVA, how does the water affect the elasticity of

the polymer? What is elasticity?4. Find and circle the repeat unit in the polymer molecule below?

5. What is the formula of the poly (vinyl alcohol) monomer circled above? (Your teacher may want to show you how to alter this slightly after you have drawn the structure.)

6. In the picture below, circle the borax cross-linking agent.



TEACHER COPY Teacher Notes:

Objective: The objective of this experiment is to explore the change in physical properties as aresult of cross-linking polymers. The results of the addition of more cross-linking agents areconsidered and another model of cross-linking is viewed. Students also have an opportunity formonomer identification.

Experimental:

1. The Polyvinyl Alcohol as a solid is mixed in water to make a 4% solution. That is 40.0 grams

of PVA per 960 grams (milliliters) of water. The best results are obtained by heating the water to about 80oC on a hot plate with magnetic stirrer. Sprinkle the PVA powder in very gently and slowly on the top of the solution while stirring so as not to cause the mixture toclump together. Temperatures above 90oC may result in decomposition of the PVA andperhaps the creation of an odor to the solution. Continue to sprinkle the PVA into the hotsolution while it is stirring. After all of the PVA has been added to the water, place a top onthe vessel. If the water evaporates off, a skin of PVA will form. This PVA sheet might alsobe a nice item to lift off and show the students. Continue stirring until the mixture is

uniform (note also that it will be somewhat viscous). Allow the solution to cool, and theresulting solution will be ready for the students to use.

2. If students are adding a dye to their PVA, make sure they do this before the addition of borax.

3. The borax (sodium borate) can be obtained from your grocery store as "Twenty Mule TeamBorax," a laundry bleaching agent. The borax is mixed at a 4% concentration in water. To dothis measure out 4 grams of borax and dissolve in 96 grams (milliliters) of water (note: Waterhas a density of 1 g/mL).

4. The material becomes more viscous as we mix the PVA and the borax. It will reach amaximum level of viscosity and will not thicken further without more cross-linking agent. The addition of a higher ratio of Borax will result in a very viscous polymer (like Jell-O).

Theoretical:

The polymer used is "poly (vinyl alcohol)". The monomer has a formula of:

• Borax is sodium borate, Na3BO3. The borax actually dissolves to form boric acid, H3BO3. This boric acid-borate solution is a buffer with a pH of about 9 (basic). Boric acid will accepta hydroxide OH- from water as indicated on the next page.



The hydrolyzed molecule will then act in a condensation reaction with PVA as indicated inthe last question on the student laboratory.

• In the above illustration, two PVA molecules are shown being cross-linked by a hydratedborax molecule. Four molecules of water are also produced.

• The resulting material is about 95% water. It is the water that gives the polymer flexibility.Note that as the polymer dries it returns to its solid phase now as a sheet that is rigid andalmost transparent.

• The PVA does not dissolve easily in water. Prepare the PVA solution at least one day in

advance.• Guar Gum dissolves in water much more easily than PVA, but seems to "jell" at a much

more unpredictable rate than the PVA mixture does. For this reason, PVA is preferred.

Additional reading for more in depth information can be found in:

Journal of Chemical Education, Jan. 1986, #63, pp. 57-60.

Sample Data and Analysis:

Observation of the PVA before the sodium borate is added:The solution is fluid.

Observation of the PVA after the sodium borate is added:The mixture becomes more viscous (thicker).

Observation of stretching the cross-linked PVA slowly : The slime flows and stretches.

Observation of stretching the cross-linked PVA rapidly : The slime breaks.




1. The mixture becomes more viscous (thicker).

2. The mixture would jell.3. The ability of the cross-linked polymer to stretch decreases. The polymer becomes more

brittle and will break.

4. 5. C2H3OH6. The hydrated borax, minus the four hydrogens are shown on the previous page bonding two

chains of the PVA polymer together.

EXPERIMENT 3 6



EXPERIMENT 3 6

A Silly Polymer

Cross-Linking a Polymer to Create Everyone's Favorite Childhood Toy, Silly Putty

Objective: The objective of this experiment is to cross-link a polymer and observe the changes inthe physical properties as a result of this cross-linking. The changes in physical properties of a cross-linked polymer are also studied as the temperature is varied.


If a substance springs back to its original shape after being twisted, pulled, or compressed, it is mostlikely a type of polymer called an elastomer. The elastomer has elastic properties (i.e., it will recoverits original size and shape after being deformed). An example of an elastomer is a rubber band or acar tire.

The liquid latex (Elmer's glue) which you use contains small globules of hydrocarbons suspended in water. The silly putty is formed by joining the globules using sodium borate (a cross-linker). The silly putty is held together by very weak intermolecular bonds that provide flexibility around the bondand rotation about the chain of the cross-linked polymer. If the cross-linked bonds in a polymer arepermanent, it is a thermosetting plastic, even if above the glass-transition temperature (Tg ). If thebonds are non-permanent, it can be considered either thermoplastic or an elastomer.

Time: A 20-25 minute period is required to perform the mixing/making of the silly putty.


• 55 % Elmer's glue solution in water• 4 % borax solution (sodium borate)• Styrofoam cups• zip lock bags•

food colors

General Safety Guidelines:

Proced re:

http://matse1.mse.uiuc.edu/polymers/glos.html#el

http://matse1.mse.uiuc.edu/polymers/glos.html#el



Procedure:

1. Wear goggles and lab aprons.

2. Pour 20 ml of the Elmer's glue solution into a Styrofoam cup.3. Add 10 ml of the cross-linker (borax solution) to each cup.4. Immediately begin stirring the solutions together using the wooden stick.5. After a couple of minutes of mixing, the silly putty should be taken out of the cup and

kneaded in the hands. Don't worry about the material sticking to your gloves as these pieces will soon mix with the larger quantity with which you are working. Continue to knead untilthe desired consistency is reached.

6. Using a ruler to measure, drop the ball from a height of 30 centimeters. To what height does

it rebound?7. Stretch the silly putty slowly from each side.8. Compress the silly putty back into a ball.9. Pull the silly putty quickly from each side and compare the results.10. Place the silly putty on some regular news print and press down firmly.11. Remove the silly putty from the news print and make observations.12. Repeat the same procedure on a comic section of the newspaper. The silly putty is non-toxic

and safe to handle so you can put it in a zip-lock bag and take it home.

13. Follow good laboratory procedure and wash your hands with soap and water when you havefinished the experiment.

Data and Analysis:

Height of the rebound _________ cm.

Observations of pulling the silly putty slowly:

Observations of pulling the silly putty quickly:

Observations of the silly putty on newsprint:

Observations of the silly putty on the comic's section of the newspaper:

Questions:



Questions:

1. How do the physical properties of the glue, water mixture change as a result of adding the

sodium borate?2. What would be the effect (your thoughts) of adding more sodium borate solution?3. What is the ratio of the height of the drop to that of the rebound distance?4. Who in the class had the ball with the most elasticity?5. How did you come to the conclusion of whose ball was most elastic?

At Home: -Place your ball in the refrigerator for 10 minutes. Recheck the bouncing portion of thisexperiment.

6. What are your observations?7. Why do you think this was observed?

-Now place your ball about 6 inches from a light bulb for about 5 minutes and again recheck the bouncing portion of this experiment.

8. What are your observations?9. Why do you think this happened?

Explain the Following:

1. Why does a car tire appear to be flat in the summer even though the gas inside is hotter thanin the winter.

2. Why does a basketball bounce differently inside a gym than it does outside on a cold wintry day.

3. Why will a tire sometimes bump during the winter as a car is moving, only to smooth out itsride after the car has been traveling for a distance.

Teachers Copy



Teachers Copy

Teacher Notes:

Objective: The objective of this experiment is to investigate cross-linking using a similar techniqueas was used in the making of slime. The same parameters are worked again with a formal and aquantitative measurement used to describe elasticity. The added home investigation of the effect of temperature on the elasticity also includes concepts of molecular motion and intermolecular bondstrength.


If a substance springs back to its original shape after being twisted, pulled, or compressed it is a typeof polymer called an elastomer. The elastomer has elastic properties. It will recover its original sizeand shape after being deformed.

The liquid latex used contains small globules of hydrocarbons suspended in water. Joining theseglobules forms the mass with which the students will be working. The covalent bonds along thechain are strong, but the bonds between chains are normally weak. However, additives such as borax

allow the formation of strong "cross-links" between chains, such as C-B-C. As the number of cross-links increases, the material becomes more rigid and strong.

If the rigidity of a polymer is noticed to decrease when a critical temperature is reached, the polymeris called a thermoplastic. If the bonds between polymer molecules are very strong, the materialdecomposes before any softening occurs. Such a material is called a thermoset plastic.

Natural sources of this liquid latex are milkweed, rubber trees, pine trees, aloe plants, and many desert plants. This latex is used to quickly mend and repair any damage to the outer covering of theplant.

Experimental:



Experimental:

There are many variations of this experiment.

1. The original silly putty was prepared using sodium silicate and mixing this with borax.2. A variation also exists using laundry starch and mixing it with borax.3. Similar variations also exist by sprinkling the borax evenly and gently over the solution of

latex then working it with the hands. This does not require as much kneading to dehydratethe sample.

Time: - About 15 minutes are required to ready solutions, cups and tongue depressors.

10-15 minutes will be required in lab for testing and clean up. The students will require 10-15 minutes of work at home in order to finish all of the experimental work on this laboratory and the write up.


1. The liquid type of starting material should jell and become more viscous as cross-linking occurs.

2. The material will become more solid or rigid.3. Student answer. This is only a method of measuring elasticity of the polymer. Stretching

gives a similar means of comparison.4. Student answer.5. Greatest rebound to drop height ratio.6. Here the student will be studying the effect of temperature variation on elasticity. Students

are sometimes surprised if they place their sample into a freezer rather than a refrigerator. The results are that the ball will shatter rather than bounce.

7. The ball should be more elastic.8. Contrary to what some students will predict, should the ball become too warm, the resulting

ball will deform rather than continue to increase in elasticity.9. The ball deformed rather than rebounding.

-All of the answers to the questions in the EXPLAIN THE FOLLOWING section involve the useof principles previously presented in this laboratory.

Which type of Fillings would you prefer?



yp g y pDAY 2

______________________________________________________________________________

Prep:

Teacher will have on board. Be seated in your lab groups at your lab stations. REMINDER: A copy of your pre-lab must be handed in before you leave lab. Teacher should prep for lab.

Obejctive:

Students will be able to. . .Understand the vocabulary of polymer synthesis by creating models.Explain the processes of polymerization (initiation, propagation, & termination).Understand the change in physical properties of a polymer by crosslinking.Identify monomers

______________________________________________________________________________

Pennsylvania State Standards:

7

3.2.10.B: Apply process knowledge and organize scientific and technological phenomena in varied ways.

• Describe materials using precise quantitative and qualitative skills based observations.

• Develop appropriate scientific experiments: raising questions, formulating hypothesis, testing controlled experiments, recognizing variables, manipulating variables, interpreting data, andproducing solutions.

• Use process skills to make inferences and predictions using controlled information and to

communicate using space/time relationships, defining operationally.3.4.10.A: Explain concepts about the structure and properties of matter.

• Explain the formation of compounds and their resulting properties using bonding theories

• Recognize formulas for compounds

• Understand that carbon can form several types of compounds.3.4.12.A: Apply concepts about the structure and properties of matter.

• Apply rules of systematic nomenclature and formula writing to chemical structure.

• Explain how the forces that bind solids, liquids and gases affect their properties.

______________________________________________________________________________ Do Now: (5 MIN. Independent activity students complete upon entering classroom.)

Teacher will greet each student at the door, hand out the Daily Learning Log and monitor

While students are working on Do Now assignment, teacher should attend to administrative duties



g gand reinforce lab safety. Teacher should check to maximize groups of four students to minimizechemical wastes.


Activity (Time) During class teacher will . . . During class students will. . .5 MIN • Begin lesson by

addressing lab safety.

• Stress to student thateating and drinking inthe lab is strictly prohibited.

• Explain to students thatthey will be doing threemini labs during this labday. They have the fulllab period to work withlast ten minutes to cleanup. They can work inany order they choose.

• Students will gather intotheir groups.

20 MIN Slime Away40 MIN Crunch and Munch25 MIN A Silly Polymer

• Circulate around theroom to reinforce labsafety.

• Complete 3 mini-labsand submit pre-labbefore leaving.

Some time throughout the

lab

• Write on board and

bring to the attention of students some timethroughout the lab.

• Lab reports are due in one week. Each mini lab must be written up separately with all post lab questions answered.

• Should read and write

down at some pointduring the lab.

Last 15 minutes • Teacher should informstudents to begincleaning up and wipeeverything down.

• Teacher will close

• Students should finish what they are working on, clean up and havelab experiment data outto be initialed before

Students will have they lab data initialed before they leave the lab & complete Daily Learning Log.



______________________________________________________________________________

Homework: (You do: An extension to the content covered in class.) Students will work on completing the lab write up due next lab period.

______________________________________________________________________________ Teacher Notes:

The Do Now assignment is administered as an informal assessment to inform the teacher of who need reinforcement/remediation. This specific Do Now will be reviewed before the beginning of the lab. The reinforcement/remediation should take place sometime through the class periods by

pulling several students from each small group. (At this time if the students who have beenidentified for reinforcement, have questions they should be allowed to ask them before selecting students who understand the concept (this is due to the limited time).

During this class period students will be working on mini-labs at stations set up throughoutthe classroom. Students will be in their assigned lab groups. It is the responsibility of each group tocomplete the three mini labs set up. During the time students are working on the mini-labs, teacher will be monitoring that students are practicing proper lab safety.

During the last fifteen minutes of class, teacher will lead the class in a discussion to

reinforcement the purpose of the three mini labs which were.• Understand the vocabulary of polymer synthesis by creating models.

• Explain the processes of polymerization (initiation, propagation, & termination).

• Understand the change in physical properties of a polymer by crosslinking.

• Identify monomers

NAM DAT



NAME: DATE:

DO NOW-DAY 2

Answer the following questions to the best of your ability. You are to work independently and youare not allowed to use any resources.

Identify the following polymerization stages.

1.

Br

C C C CBr

C CBrH Br

CCBr

BrH

+

2.

BrBr BrBr

C CBr Br C CBr Br

3. Br Br Br2

R O O Rheat

or hvR O O R+

Which type of Fillings would you prefer?DAY 3



DAY 3 ______________________________________________________________________________

Prep:

Teacher should have the room set up so the desks are in two large groups. Teacher is to select amethod of randomizing students into the two groups. In the center of one group of desks place a white piece of paper representing composite and at the center of the other group of desk place apiece of black construction paper representing amalgam.

______________________________________________________________________________

Objective: ______________________________________________________________________________ Student will. . .Defend either amalgam or composite fillers using supporting chemistry knowledge as evidence.

Pennsylvania State Standard:8

3.2.10.D: Identify & apply the technological design process to solve problems.

• Examine the problem, rank all necessary information and all questions that must beanswered.

• Propose and analyze a solution.

• Communicate the process and evaluate and present the impacts of the solution.

3.2.12.D: Analyze and use the technological design process to solve problems.

• Assess all aspects of the problem prioritize the necessary information and formulatequestions that must be answered.

• Propose, develop & appraise the best solution and develop alternative solutions• Implement and assess the solution redesigned and improve as necessary.

• Communicate and assess the process and evaluate and present the impacts of the solution.

Do Now: (5 MIN. Independent activity students complete upon entering classroom.)

Teacher will stand by door to greet students and hand out Daily Learning Log.


Activity (Time) During class teacher will . . . During class students will. . .5 MIN E l i h d P i d

of debating. (Eachr p m mb r i



group member isrequired to state one

fact about the fillerbefore the debatebegins each group willbe allowed to comment when they are calledon.) Explain tostudents that they willhave 30 minutes to

review the literature tofind chemistry facts onthe specific filler they are to defend.

20 MIN Review Literature(First Activity)

• Monitor and sit in ongroup that needhelp/assistance.

• Make sure that both

groups understand whatit is to have chemistry evidence to supporttheir facts.

• Scan literature to findinformation on theirspecific filler and any chemistry information

to support their filler.

15 MIN Debate (Second Activity)

• Over see • Each student will state afact about the filler they are defending

10 MIN (Summary) • Teacher shouldhighlight the pointsmade by both groupshowever should notfavor either type of filler. Allow thestudents to evenconsider furtherstudy/understand thetypes of filler.

• Pay attention, posequestions to confusing points made in class by teacher.

______________________________________________________________________________ Exit Assessment: (You do: How will you assess if the students acquired the skill for today)

NAME: DATE:



DO NOW-DAY 3

Answer the following questions to the best of your ability. You are to work independently and youare not allowed to use any resources.

Make a list of all the facts you remember about amalgam and composite resin fillers.

AMALGAM COMPOSITE

______________________________________________________________________________ Teacher Notes:



Teacher Notes:

Monitor students closely to make sure that they have sufficient information on their paper

during the Do Now to take back to their sub groups. Students who are struggling with getting started should be assisted during this time to get them motivated to be productive in groupdiscussions.

Teacher should not say any to funnel students’ thinking during the Do Now and during thetwenty minute literature review. The twenty minute literature review time should be closely timed.

Teacher should briefly explain the following. . .1. Each student must state a fact about the filler they are defending.2. Then the debate will begin with three points from each group which will be debated

by a representative from each group.3. Summarize and conclude.

If the following points are not brought up during the debate, they should be discussed toclose the activity.

• Polymerization forces composites to shrink o Unreacted double bonds cause post shrinkage.

• Certain composite resins hydrogen bond

• Amalgam fillers are not bonded to the tooth

• Corrosion occurs with the amalgam filler called (creep)



DAILY LEARNING LOG

Prior Knowledge: The prior knowledge I had to bring into this lesson was…

MAIN IDEA: Today I learned…

3 Important Points about what I learned are:

1.

2.

3.

x.

x.

Societal Relevance: One way I could see how this information applies to the “real world” is …

This page is intentionally left blank.

This page should be trashed when this



p gdocument is printed.

Initial Question Amalgam is used as a filler for teeth decay. Today more and moredentists are taking their practices to be amalgam free and are usingcomposite fillings. As a young adult which type of filling would youhave your dentist use?

Which type of filling would youprefer?

Results D ti t th ti i i l f ffi t tH



Existing Information

• I have some in my mouth

• General knowledge of amalgam.

• Teeth are made of calcium.

• How cavities are formed.

• Ex erience of dentist’s office.

Reflect and OrganizePolymerization(initiation, propagation,termination)Hydrogen bonding

Model Accepted?

Peer Review There is substantial information that supports both amalgamand composite fillings. The major differences are personalpreferences & costWe have used amalgam as a filler for many years and notmany people have had been exposed to Hg poisoning .Composite fillings are not as durable.

Composite fillings cost too much and amalgam fillings arecheaper.Is light curing process of composite fillings dangerous tous?

Dentist are the practicing in amalgam free offices to prevent Hgpoisoning which is why they are supporting composite fillings.

Price is a major factor in which filling patients get. The compositefillings are prepared to match the color of an individual’s teeth.

New Information Needed

• Introduction of amalgam andcomposite fillings (Thesis).

• How do composite fillingswork?

• How do amalgam fillings work?

• Are there any side effectscaused by both types of fillings? Community Knowledge

There is a slight risk of getting Hg poisoning if the root of the tooth is exposed to amalgamfillings.Dentists are at risk of small amounts of Hg poisoning each time they use amalgam as a filler.Effects can be detrimental over a long period of time.

Although composite fillings are expensive & do not withstand as long as amalgam fillingsthey are safer for both the patient and dentist.

Created by Vishal Patel

composite chemistry

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