Setting reaction & compressive strength of GPC

Glass polyalkenoate cements (GPCs)

are important material for the modern

clinical dentistry

Advantages:

-chemically bond to the apatite mineral

of teeth

-avoid secondary carries

- inherently good adhesion

- have potential to replace amalgam

Limitation

-brittleness

-poor inferior fracture toughness and

wear resistance

Due to limitation of GPCs, this study lead to set of

fundamental to investigate alternative in the way

to optimize the application of GPCs in term of

Focused on the optimization of GPCs in term of:

-Compressive strength

-Setting reaction

Objectives

1. To follow the setting reaction of GPCs

2. To study influence of MMT on compressive strength of GPC

3. To investigate the influence of Na on the setting reaction of cement

GPCs composed of glass powder alumino-silicate and aqueous solution of polyacrylic acid.

Formation: acid degrade network structure of glass and releasing metal cations (Ca2+, Na+, or Al3+) [1].

Fig 1:Schematic depiction of the setting reaction of GPCs formation[2]

[1]De Barra, Hill R.G., Influence of alkali metal ions on the fracture properties of glass polyalkenoate (ionomer) cements. Journal of Biomaterial 1998, 19, 495-502.

[2] Technical Product Profile: 3M ESPE Ketac Chem Glass Ionomer Cement. 3M ESPE AG: Seefeld,Germany . Pg:6.

5

The COO− groups and the released Al3+ and Ca2+ ions enables cross linking of these chains, giving a solid network

around the glass particles. The binding of the COO− groups

with Ca2+ ions from the enamel occur and form a chemical

bond between the cement and the tooth structure [3].

Reaction involved is acid-base reaction where glass being a

base , accepts protons from acid even though it is not soluble

in water. The number and type of anions and cations

released from the glass particle will determine the extent of

cross linking in polysalt matrix [4].

[3] Tjalling J., Algera, Cornelis J., Kleverlaan, Birte P.A., Albert J.F., The influence of environmental conditions on the material properties of setting

glass-ionomer cements. Dental materials 2005, 22, 852–856.

[4] De Barra E., Composition structure property relationship in glass ionomer cements. In material science and technology. University of Limerick,

2008.

Setting reaction of GPC

- The primary step is hardening step after glass and aqueouspolyacid mix each other about 3-5 minutes.

-Through FTIR study, Crisp and Wilson [5] assigned that acalcium salt was formed leading to gelation at initial step.

- The secondary mechanism is post-hardening steps. This stepis involves the formation aluminum salt species and contributeto the improvement of mechanical properties that measuredrelative with time

Composition of glass influence setting reaction of GPCs

- Al in the glass structure is important to create negative sites tobe attacked by polyacid.

- Na result the cementlikely to have disportionate influence onits properties [1]


[5] Crisp S., Pringuer M.A., Wardleworth D., Wilson A.D., Reaction in glass ionomer cements: II. An infrared spectroscopic study.J Dent Res 1974, 53, 1414-1419.

FTIR technique used : to determine setting reaction by

assigning particular peaks that develop due to acid-base reaction.

- the absorption of original glass powder is totally different with glasses

that have been produced.

Compressive strength increase with the addition of MMT.

- ADA-MMT addition increase the mean compressive of GPCs [6]

[6] Dowling A.H., Stamboulis A., Fleming J.P., The influence of montmorillonite clay reinforcement on the performance of a glass

ionomer restorative. Journal of dentistry 2006, 34, 802-810.

GLASS COMPOSITION

• high temperature (1400 C) melt quench route

Table 1: Glass composition in mole percentage

Code SiO2 Al2O3 P2O5 CaO CaF2 Na2O

LG3 33.3 22.2 11.1 22.2 11.1 -

LG66 33.3 22.2 11.1 17.8 11.1 4.4

PREPARATION OF GPC

GPC with MMT

Glass powder +

PAA + water

Ratio : 2 : 1 : 1

GPC without MMT

Glass powder + PAA

+ water + MMT clay

Ratio : 2 : 1 : 1 :

2.5wt%

Homogenously mixed and placed

into test mold

- GPCs were kept in test mold at 37 C for 1 hour.

- quenched into liquid nitrogen ( for less 1 hour GPCs)and dehydrated with ethanol.

- GPCs were stored in water at 37 C

- ageing time: 5 minutes to 28 days

CHARACTERIZATION

Compressive strength: Instron compressive machine (5kN load cell at a

loading rate of 1 mm/min)

Setting reaction :Fourier Transform Infrared spectroscopy (range 200-4000 cm-1)

RESULTS

&

DISCUSSION

Compressive Strength

- due to the maturing and hardening reaction.

- invariant strengths are very dependent on the aging time.

- unit: MPa.

- F : load at fracture force in Newton (N)

- D : average diameter of the specimen in millimeters (mm).

P = 4F

D²

0 5 10 15 20 25 30

30

40

50

60

70

80

Figure 2: Compressive strength of LG3 cement

without and with addition of MMT

0 5 10 15 20 25 30

0

10

20

30

40

50

60

70

80

Figure 3: Compressive strength of LG66 cement

without and with addition of MMT

• increased rapidly in 14 days period

•Without MMT=53.55 MPa

•With MMT =74.21 MPa

• increased slowly between 1 to 7

days

• increased rapidly after 7 days and

continued even after 28 days

•Without MMT =53.24 MPa

•With MMT =66.16 MPa.

increased the compressive value

property of MMT : able to act as filler by intercalation reaction and fill in the

layer within GPCs.

The hydrogen bond that formed between acid and MMT layer also may

influence the increase of strength of the GPCs.

According to Drowling et al. (2006), the formation of hydrogen bond

occurred between carboxylic acid group and amine group of ADA-MMT

have a greater reinforcing effect on the mechanical properties of the

material system to which they have been added.

The amount of MMT used that is 2.5 wt% also suitable for both glasses in

cements formation. Drowling et al. (2006) highlighted that MMT addition with

excess of 2.5 wt% cause in difficulty to mix with the glass.

4.4 mole% of Na2O might cause the differences interaction in the LG66 cements.

When comparing the trends of compressive strength for both cements, it was found that LG3 cements showed rapid increase within 14 days. After 14 days, the compressive strength became slightly lower.

For LG66 cements, the compressive strength continually increases even after 28 days.

It shows that the setting reaction of LG3 cements were faster than LG66 cements. This situation most likely related to the alkali metal anions leaching process.

Na+ in LG66 ions have tendency to slower the setting reaction by competes calcium and Ca2+ and Al3+ to bind with carboxylate group of PAA.

At initial aging time, Na+ may disrupt the crosslinking . However, this situation only temporary and take place at early stage of reaction. Na+ has mobile properties to move freely and will leave the carboxylate group [7] (Akinmade and Hill, 1991). Therefore, after Na+ released from carboxylategroup, Ca2+ and Al3+ will replace to form crosslink.

Similar finding was obtained by De Barra and Hill (1998). In their study, they found that the influence of Na+ content glasses give significant reduction in compressive strength at early stage of reaction and became considerably reduced as aging time increase.

[7]Akinmade A.O., Hill R.G., The influence of cement layer thickness on the adhesive bond strength of polyalkenoatecements. Biomaterials 1991, 13, 931


Before formation

- FTIR spectrum of LG3 glass

- FTIR spectrum of LG66 glass

- FTIR spectrum of PAA

After formation

- FTIR spectra of LG3 cement with/without MMT at various aging time

- FTIR spectra of LG66 cement with/without MMT at various aging time

4000 3500 3000 2500 2000 1500 1000 500

0

20

40

60

80

100

4000 3500 3000 2500 2000 1500 1000 500

0

20

40

60

80

100

Figure 4: Infrared spectrum for LG3 glass Figure 5: Infrared spectrum for LG66 glass

•1050 – 980 cm-1 is the asymmetric Si-O(Si) stretch vibration in the glass

• band intensity near 730 cm-1 are may related to the Al, Ca and/or ions

from the silica network.

• 850 – 500 cm-1 due to extraneous ion such Ca2+ and Na+ that

incorporated in glass phase[8].

[8] Farmer V.C., The infrared spectra of mineral. Mineralogical Soc., London.p 469, 1974.

% I

nte

nsi

ty

% I

nte

nsi

ty

Wavenumber, cm-1 Wavenumber, cm-1

Si-O (Si)Stretch

Si-O (Si)Stretch

1700 – 1660 cm-1 is C=O stretching

3200 cm-1 to 2400 cm-1 gives information of acidity character.

4000 3500 3000 2500 2000 1500 1000 500

0

20

40

60

80

100

Figure 6: Infrared spectrum for PAA

% I

nte

nsi

ty

Wavenumber, cm-1

COOH

O-H Stretch

For original glass, there was only one absorption peak between 1050 – 980 cm-

1.

After 5 minutes aging time, two new peaks already developed

1)1710 – 1390 cm-1: formation of COO-M+

2) 900 cm-1 : hydrated silica gel (Si-OH).

The change of absorption pattern between 1200 – 900 cm-1 were related to the evaluation of band as cement formed.

The stretching vibration observed at 1650 cm-1 due to the binding vibration water that appeared after the leaching (Davis and Tomozawa, 1996). Peak at region 3700 to 2400 cm-1 came from O-H stretch.

For original glass, there was only one

absorption peak between 1050 – 980

cm-1.

Generally, the absorption peaks of

LG66 cements were similar with LG3

cements.

Two new peaks developed after 5

minutes set of cements.

1) 1710 – 1400 cm-1 : COO-M+

2) 900 : hydrated silica gel (Si-OH).

The change of absorption pattern

observed between 1200 – 900 cm-1

and the stretching vibration at 1650

cm-1 were also same with LG3

cements. Peak at region 3700 to

2400 cm-1 came from O-H stretch.

• As time elapsed, the shoulder peaks at 1570 cm-1 and 1550 cm-1

increase in intensity (Figure 8 & 9) due to formation COO-M+ as metalions (Al3+ and Ca2+) crosslink with the carboxyl group in the acid [9].

• In contrast, the intensity of shoulder peak at 1710 cm-1 decreases inintensity due to uptake of H+ from acid by silica network to form silicagel layer during the cross linking of metal ions and COO- in cementsformation.

• Setting reaction of LG66 cement is slower than LG3 cement. Na+ inLG66 cement have tendency to compete with Al3+ and Ca2+ anddelay the crosslinking process [1].

[9] Crisp S., Wilson A.D., Reaction in glass-ionomer cements . The precipitate reaction. J.Dent Res 1974, 53, 1420-1424.

[1] De Barra, Hill R.G., Influence of alkali metal ions on the fracture properties of glass polyalkenoate (ionomer) cements. Journal of Biomaterial 1998, 19, 495-502.

LG66 cement: peak of COO-M+ is

weak - delay reaction of cross

linking due to the presence of

sodium.

This is also the main reason why

the working time in this stage is

too slow and GPCs formed have

low compressive strength.

shoulder peak Si-O(Si) stretch is

also still very weak. The setting

reaction of LG66 cement

seemed slower than LG3

cement.

Sodium ions have tendency to

compete with other ion like

calcium and aluminium cations

and may inhibit the crosslinking

process.

Figure 9: Comparison of FTIR spectra of LG3 cement and LG66 cement without MMT at 5 minutes aging time

LG3

LG66Si-O(Si)

COO-M+

A slight difference between spectrum at 920 cm-1 that corresponded to hydratedsilica gel.

With addition of MMT, this peak is seemed hardly to observe.

The intensity of this peak was very small compared with glass without MMT. This mayhave been because of hardening reaction that took place.

Cements with MMT easily to form hard surface and less working time compare thancements without MMT.

2000 1800 1600 1400 1200 1000 800 2000 1800 1600 1400 1200 1000 800

% I

nte

nsi

ty

% I

nte

nsi

ty

Wavelength, cm-1 Wavelength, cm-1

Si-O(Si)

Si-O(H)

Si-O(H)

Si-O(Si)

Figure 10: Infrared spectra of LG3 glass with and without addition of MMT at 5 minutes

Figure 11: Infrared spectra of LG66 glass with and without addition of MMT at 5 minutes

The compressive strength for both GPCs were improved with the

addition of MMT.

LG3 cement achieved 74 Mpa (with MMT) and 53 Mpa (without

MMT).

LG66 cement achieved 66 MPa (with MMT) and 53.24 Mpa (without

MMT).

It proves that MMT able to act as filler by intercalation reaction

within GPCs. The formation of hydrogen bonding also provides the

great effect on the compressive strength.

For both GPCs, the peak at1700 cm-1 (COOH) decreased in

intensity.

While peak at1540 cm-1 (COO-M+ ) peak increased in intensity.

The peak at 900cm-1 corresponded silica gel (Si-OH).

Setting reaction of GPCs from LG3 glass was faster than GPCs

from LG66 glass.


[2] Technical Product Profile: 3M ESPE Ketac Chem Glass Ionomer Cement. 3M ESPE AG: Seefeld,Germany . Pg:6.

[3] Tjalling J., Algera, Cornelis J., Kleverlaan, Birte P.A., Albert J.F., The influence of environmental conditions on the material properties of setting glass-ionomer cements. Dental materials 2005, 22, 852–856.

[4] De Barra E., Composition structure property relationship in glass ionomer cements. In material science and technology. University of Limerick, 2008.

[5] Crisp S., Pringuer M.A., Wardleworth D., Wilson A.D., Reaction in glass ionomer cements: II. An infrared spectroscopic study.J Dent Res 1974, 53, 1414-1419.

[6] Dowling A.H., Stamboulis A., Fleming J.P., The influence of montmorillonite clay reinforcement on the performance of a glass ionomer restorative. Journal of dentistry 2006, 34, 802-810.

[7]Akinmade A.O., Hill R.G., The influence of cement layer thickness on the adhesive bond strength of polyalkenoate cements. Biomaterials 1991, 13, 931

[8] Farmer V.C., The infrared spectra of mineral. Mineralogical Soc., London.p 469, 1974.

[9] Crisp S., Wilson A.D., Reaction in glass-ionomer cements . The precipitate reaction. J.Dent Res 1974, 53, 1420-1424.

Technology

Setting reaction & compressive strength of GPC