Comparison of surface layer properties of composite resins by ESCA, SEM and X-ray cliffractometry

Comparisonof surfacelayer properties of compositeresins by ESCA,SEMand X-ray diffractometry Department

of Dental

Technology,

Osaka University,

Faculty of Dentistry.

Osaka 565.

Japan

W.H.Do@la,s Biomaterials (Received

Program,

University

11 October

1983;

of Minnesota,

revised

School of Dentistry,

15 February

Minneapolis,

Minn.

55455,

USA

1984j

Hyperfine surface layer properties of three types of dental composite resins highly-filled filled resins, were studied using X-ray photoelectron

conventional

spectroscopy (ESCA) by a combination

and micru

of X-ray diffracts

metry and scanning electron microscopy (SEM). X-ray diffraction and SEM analysis showed clearly that each resin has different characteristics of SiOz particle size and distribution. ESCA depth resolution with argon ion etching indicated that, in contrast to conventional and microfilled resins, carbon due to polymers of highly-filled resin decreases Keywords:

Composite dental

resins

restorative

aesthetic them

resin

particles

permit than

have

come

however,

to

resin-rich

layer. nanometer

large filler

To overcome developed

it to

be finished with

than

The

this

composite

formulations

so

necessary

performance

a much filler

far

All

tested

especially

in the

variety lacked

of the

withstand

stress

size,

distribution

and

seem

to be very

important

ment

of suitable

fillers.

This

examines,

study

scanning

electron

photoelectron scopy

for Chemical

three

types

and and

mentedle3.

for

@ 284

1984

improved

surface

Butterworth Biomaterials

structural

fillers

layer

surveying

the

In

technique

hyperfine

is

surface

AND METHODS

Three

types

conventional (Tab/e

of composite

resins,

highly-filled

composite

‘Concise’,

and

I), were

each

prepared

resin ’ Pl 0’.

microfilled

by mixing

Photoelectron

two

resin pastes

Spectroscopy

and

resin,

Ek: hv - Eb

of

(nanometer

range)

’

occlusal

particular,

information

t

docuuseful

the

provides

escape depth ( lo-2oii

X-ray on an

as shown

Ltd. 0142-9612/84/050284-05$03.00

Vol 5 September

photoelectron

X-ray

whose

been

provide

In

X-ray

)

composite,

solving

resins.

(ESCA

Spectro-

properties

have may

8 Co (Publishers) 1984,

Electron

highly-filled

of composite

analysis, and

conventional

approaches

for

hydrogen”‘.

this

preparation

at the

diffraction

properties

spectroscopy thin

the -

choosing

problem

photoelectron extremely

Sample

for the develop

(SEM),

(ESCA:

chemical These

information wear

by X-ray

Analysis),

useful

except

etching,

of posterior

especially

factors

microscopy

of composites

microfilled physical

volume,

spectroscopy

very

MATERIALS

X-ray

Particle

ion

argon

of filler is required.

and a greatervolume

surface,

all elements

with

layers.

‘Silai,

placements’.*. A hard resin

1 and covers

is,

and with

of the to

the

in Figure

smoother resin

have

range

therefore a

surface layer.

filler

found

composites

wear.

characteristics

wear,

small

range of the resiprich

combination

make

problem,

microfilled

conventional occlusal

occlusal

to

as

of their

sizes

whose

the coarse

excessive

frequently

because

to finish. been

surface

be used

has

weaker

extreme

depth in the nanometer

their

composites.

shows

with increasing

principally

However,

is possible

conventional time

composites,

materials,

impossible

surface

ESCR

properties.

microfilled

dramatically

Figure 1 (ESCAJ.

Schematic

diagram

of X-ray photoelectron

spectroscopy

1

Dental

Table 1

Chemical

and physical

properties

Plo*

of composite

resins

Concise*

Silar*

Bis-GMA

Bis-GMA

Bis-GMA

Filler material

Stllca

Silica

Silica

86

78

51

total (wt %) average size (N

3.0

X-ray photoelectron Before

Resm material

3600

Coefflclent of thermal expansion (1 /“C)

26~10~~

37x10-s

51 x 10-s

(mg/cm’)

0.59

0.67

86

of the teflon

same

weight

The

Rockwell

1.60

Figure2

dye of inner diameter20

side of the composite and the

other

put into

mm and height2

was kept on a clean

side was

pressed

with

a thin

mm. One

Samples Siemens 0.15 40

X-ray

Diffractometer

mm receiving

diffractometry

with

slit. and scanning

Cu-Ka speed

on

radiation, of 2”/min.

at

seem

composite

Concise

pattern

from materials broken

or

with smooth

cut

distribution

seldom

and

directly.

deposition,

then

microscope

at 40

observed

clear

glassy surfaces,

polished Samples

provides to

information

samples

observe

the

were gold-coated under

a

JEOL

were

particle

as polymer resin

3

shows

of the three

tion from

broken

means

that

electron

seen

PI0

is dif-

shows

This

result

Figures those

in Figures

sizes

filler

3a,

of PlO

particles

3d, e and f show

b

than

Si02

are indis-

diagonal

particles

of

while

in the

sections

PlO

appear

microfilled

It should

layer at the surface 3d,

informa-

in the matrix of the microfilled

of Concise,

resin-rich

bulk

in Figures

particles

the small

The

microphoto-

The

is shown

while

3c),

electron resins.

the smaller

(Figure

than

the

that

position.

resin they are too small to distinguish.

by vapour

of PI 0

of conventional

of SiOz are dispersed

scanning

composites

composites.

smaller

particles

by 20.

2C is the X-ray

peak

composite

are apparent,

of cut

This

in Figure surface

those

peak

peaks

matrix.

Figure graphs

small

of composite

near the SiO,

resin Silar, which

at the SiOz

be noted

cannot

be clearly

e and f.

kV.

X-ray photoelectron Figure

4

shows

composite

resins

The relative internal) L

patterns

1. Figure

of the microfilled

peak

resin

2B).

in Table

that many

resin Silar

microscopy

analysis

on

microscopy

of unfilled

(Figure

as noted

tinguishable. SEM

range.

into the specimen.

and area of the smooth

Concise

Since

the peak

and c, in which

electron

radiation Torr

information

to be less than

a

kV. 30 mA.

Scanning

of depth

B and C are identified

with

2A)

in the by X-ray

to obtain

night,

were made

Mg-Ka

(Figure

suggests

identified

for one

1 Oeg

The peak intensity

fraction

plate.

analysis

were

used

the X-ray diffraction

2A,

a very broad

X-ray diffraction

was

with

in the

and scanning electron

shows

resinless,

glass surface,

teflon

system

resins. The broad peaks at about 18.5O comparison

were

vacuumed

60 mA

as a function

X-ray diffraction

H.

mixtures

ESCA

etching

in Figures *3M, St Paul, MN, USA3. ‘Barcol 83 IS equivalent to 107

were

RESULTS

71

76

ion

and W. H. Douglas

with Al foil. Measurements

at 10 kV,

composition

2500

hardness+ 24 h

ev)

Argon

4100

Barcol

samples

on a PerkiwElmer (1253.6

Compressive strength 24 h (kg/cm’)

Water absorption

analysis,

resins: M. Okazaki

spectroscopy

then partly covered

0.04

B-l 0

composite

I

I

1

typical

4C)

whereas

can

those

signal

binding

of composite be scarcely

of pure

the changes and

composites

during

depth signal

of

oxygen

Si

PI0

The figure signals

sputter

time,

signals

decrease

with

initially,

atomic

con-

and

Silar

with Ar ions. Sputter from

reveals while

a strong

chains.

Concise

the surface

is roughly

of the

equivalent

to a

that the carbon

C( 1 s)

the

increase

whereas

shows

in relative

in PlO,

to the depth

decreases

O(2s)

40) carbon

1 h of sputtering

1 h of sputtering

of 1200a.

and Silar

sputtering,

can be seen clearly(Figure4B).

of C, 0

is proportional

eV. Si(2s)

4A)

before

resin (Figure

5 shows

time

three resin.

energy,

detected

centrations

composite;

the

of pure

PI 0 (Figures

of C(1 s) due to the bound Figure

of

that

per second per unit energy

against

of Concise

spectrum

spectra with

intensities(counts

are presented

(Figure

ESCA

in comparison

and Si(2 p) peaks

The

spectroscopy

silicon

Si(2s)

and

dramatically

with

the

Concise

and Silar,

then rise gradually

0 and Si

to near initial

levels. Table calculated I

I

25

20

I

J IO

15 2e (0) Figure 2 X-ray diffraction patterns of composites and unfilled resin. A: highly-filled resin, PlO; B: conventional composite, Concise; Cc microfilled resin, Silar; 0: unfilled resin.

depth.

2 from

The

shows the

the

values

SiOp concentration

far from its bulk concentration original

SiOz

surface

However,

the

approach

rapidly

is too Si02

because

concentration

to the bulk value,

1984,

i.e.,

concentrations

5 as a function

of each

shallow,

Biomaterials

filler

in Figure

composite

of

is still

the depth from the 12OOa of

when

PI0

in depth. seems

compared

Vol 5 September

to with

285

Dental

composite

resins: M. Okazaki

and W.H. Douglas

Figure 3 Scanning electron microphotographs of composite resins at broken (a, b and c) and diagonally resin, PIO; b,e: conventional composite, Concise; c, 17 microfilled resin, Silar.

cut surfaces (d. e and f). a, d: highly-filled

C(Al 6

PI0

s-

7

6.

,

I

,

1

,

,

,

,

C(AI RN6

Resin

5C 4-

I -

-1000

-800

-600

-400

0

Ee Cd’)

Figure 4 ESCA X-ray satellites Sitar; 0: unfilled resin.

286

Biomaterials

1984,

of composites

Vol 5 September

and unfilled resin. A: highly-filled

Eg (eV1

resin, PIO; 6: conventional

composite.

Concise; C: microfilled

resin,

Dental composite

resms: M. Okazaki

and W. H. Douglas

Concise 60

60

i

0

IO

20

30

40

50

60

Figure 5 ESCA atomic concentration (%) of composites as a function of sputtering time. A: highly-filled resin, PlO; 13 conventIonal Concise; Cc microfilled resin, Silar. C, 0 and Si indicate the atomic concentrations of carbon. oxygen and silicon, respectively.

those

of Concise

concentration of the

and

Silar.

of resin

fillers

This

matrix

increases

means

decreases

rapidly

from

that

in PI0

the

could

sharply

while

that

such

the

surface

into

the

bulk.

the

not be applied

surface completely

results

and

of X-ray

method distribution

particles

of

of PI0

accurately And

the

for

analysis

of fields

diffraction

the

nanometer

range with

results

were

quantifying sensitivity

Although

factors,

which

have

concentrations

Depth

been

SIO,

0

(wt%)*

9.7

ESCA

the

Concise

Silar

SIO,

SiO,

(wt%)*

18.5

1200

62.9

19.6

31.9

86

78

51

resrn

PlO

as the is

bulk

surface

(VA%)*

2M, 100.

W=

aM,+

bM,+

concentration

of Si;

M,:

atomic

weight

of Si

b: atomic

concentration

of 0;

M,:

atomic

weight

of 0

c: atomic

concentration

of C:

M,:

atomic

wetght

of C

1

of highly-filled

such Since

CM,

w

a: atomic

Table

features

distribution.

These

13.6 9.9

‘See

distance

texural

filler

com-

Silar.

to obtain

toward

15.1

+

to their and

conventional resin

was for

15.0

a(M,

size

of

thin to be

useful area

56.7

=

particle-to-particle

be due

filler

those

microfilled

in the found

ion

peak

600

(wfil

may

loading,

from and

was

a

methods

11.0

*ws,02

different

profile

PI0

in the

and

54.0

concentratmnt

the filler resin

the

argon

300

Bulk

ion etching,

2.

in

even

developed layer

thin

it is not

Ws,oz in the hyperfme

Pl 0

(A)

SEM,

utilizing

in each

Table 2 S/O, filler concentrations layers of composite resins

with

the

measurement

of

extremely

Electron

in analysing

In our work, and

in the

resolution

Thus,

of layers

diffraction

obtained.

in Figure

successfully

Especially,

are accessible.

samples

estimatrons

estimate

layers.

effective

compositions

X-ray

ESCA

the atomic

used

SiOz

composites

of highly-filled

Concise

differences filler

better

be determined

range.

features.

been

the to

the depth

has similar

and has proved

combined

size

can

surface

chemical

this

the

large

hyper-fine has

that

roughly

results

confirmed,

1 to 2 nm of surfaces4-8.

etching

too

composition

ESCA

suggest

However,

are

is in the micrometer

Recently upper

X-ray

studying

microprobe

particles.

structures

of this technique

analysis estimating

Concise

elemental

and molecular

number

for

filler

and

from

although

suitable

diffraction

is useful

argon

layer

posite simple

of

to heterogeneous

provided

layers. With

The

they

compositions

surface

DISCUSSION

rigorously

as composites,

composite,

Figure 6 Scannmg electron microphotographs of composites after 1.5 h of ESCA sputtering. a: highly-hlled resjn, PlO; 6: conventional composite, Concise.

Biomatenals

1284.

Vol 5 September

287

Dental

composite

resins: M. Dkazaki

and W.H. Douglas

much less than those found in conventional composite Concise and microfilled resin Silar, there is much less tendency for the particles to compress together, and less resin to exude onto the curing surface. However, in the case of Concise the small digital pressure under a matrix band may compress the surface particles closer together with the exudation of excess resin onto the surface. On the other hand, in addition to the lower filler loading the microfillers of Silar are bound in polymerized resin particles during pretreatment Therefore, much resin may exist near the surface. It should be noted, however, that use of Ar-etching of ESCA for surface removal is likely to change the chemical nature of the surface. Thus, identification of the remaining chemical states may not accurately reflect the initial composition. Further interesting results concerning the distribution of particles of composites were obtained by observing their ESCA-etched surface by SEM. Although the surface of composites PlO and Concise after 1 .S h of ESCA sputtering, shown in Figure 6a and b, are stiil too smooth to provide clear pictures, the differences between the composites in particle size and distribution are evident.

288

Biomaterials

7984,

Voi 5 September

Investigations on the filler distribution and contacts in composite resins are in progress.

REFERENCES Craig, R.G. and Peyton, F.A., Restorative Dental Materials, (6th Edn), Mosby, St Louis, 1980, pp 394-417 Phillips, R.W., Skinner’s Science of Dent& Materials, (8th Edn), W.B. Saunders, Philadelphia, 1982, pp 216-247 Dental Product 3M Technical Information, St Paul, Minnesota, September 14, 1981, Sheet No. 4 Baud, C.A. and Bang, S., Electron probe and X-ray diffraction microanalysis of human enamel treated in vitro by fluoride solution, Caries ffes. 1970, 4, l-l 3 Hercules, D.M. and Craig, N.L. Composition offluoridated dental enamel studied by X-ray photoelectron spectroscopy (ESCA), J. Dent. Res. 1976, 56. 829-635 Wagner, C.D., Riggs, W.M., Davis, LE., and Moulder, J.F., Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Co., (Physical Electronics Division), Eden Prairie, Minnesota, 1979, pp 3-31 Duschner, H., Uchtmann, H., and Ahrens. G.. Electron Spectroskopische Bestimmung der Ca-, P, 0 und FVerhaeltnisse in Uitraduennen Schichten der Schmelzoberflaeche, Dtsch. Zahnaerztl. Z 1980, 35, 306-309 Uchtmann, H. and Dushnev, H., Electron spectroscopic studies of interactions between superficially-applied fluorides and surface enamel, J. Dent Res. 1982, 61, 423-428