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 aqueous
polyacid mix each other about 3-5 minutes.
-Through FTIR study, Crisp and Wilson [5] assigned that a
calcium salt was formed leading to gelation at initial step.
- The secondary mechanism is post-hardening steps. This step
is involves the formation aluminum salt species and contribute
to the improvement of mechanical properties that measured
relative with time

 Composition of glass influence setting reaction of GPCs
- Al in the glass structure is important to create negative sites to
be attacked by polyacid.
- Na result the cementlikely to have disportionate influence on
its properties [1]

[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.
[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

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

Table 1: Glass composition in mole percentage

 PREPARATION OF GPC

GPC with MMT GPC without MMT
Glass powder + Glass powder + PAA
PAA + water + water + MMT clay
Ratio : 2 : 1 : 1 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)

Compressive Strength
- due to the maturing and hardening reaction.

- invariant strengths are very dependent on the aging time.

P= 4F
D²

- unit: MPa.

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

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

80

80
70

60
70

50

60
40

50 30

20
40
10

30 0
0 5 10 15 20 25 30 0 5 10 15 20 25 30

Figure 2: Compressive strength of LG3 cement Figure 3: Compressive strength of LG66 cement
without and with addition of MMT without and with addition of MMT

• increased slowly between 1 to 7
• increased rapidly in 14 days period days
•Without MMT=53.55 MPa • increased rapidly after 7 days and
•With MMT =74.21 MPa 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 carboxylate
group, 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 polyalkenoate
cements. Biomaterials 1991, 13, 931
[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.

 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

100 100

80 80
% Intensity

% Intensity
60 60

Si-O (Si) Si-O (Si)
40
Stretch 40
Stretch
20 20

0 0
4000 3500 3000 2500 2000 1500 1000 500 4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1 Wavenumber, cm-1

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.

100

80

% Intensity
60

40

COOH
20
O-H
Stretch
0
4000 3500 3000 2500 2000 1500 1000 500

Wavenumber, cm-1

Figure 6: Infrared spectrum for PAA

 1700 – 1660 cm-1 is C=O stretching
 3200 cm-1 to 2400 cm-1 gives information of acidity character.

 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 metal
ions (Al3+ and Ca2+) crosslink with the carboxyl group in the acid [9].

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

• Setting reaction of LG66 cement is slower than LG3 cement. Na+ in
LG66 cement have tendency to compete with Al3+ and Ca2+ and
delay 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.
LG3
 This is also the main reason why
COO-M+
the working time in this stage is
Si-O(Si) too slow and GPCs formed have
LG66 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.

Figure 9: Comparison of FTIR spectra of LG3 cement and LG66  Sodium ions have tendency to
cement without MMT at 5 minutes aging time
compete with other ion like
calcium and aluminium cations
and may inhibit the crosslinking
process.

Si-O(H)

Si-O(H)
% Intensity

% Intensity
Si-O(Si)
Si-O(Si)

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

Wavelength, cm-1 Wavelength, cm-1

Figure 10: Infrared spectra of LG3 glass with and Figure 11: Infrared spectra of LG66 glass with and
without addition of MMT at 5 minutes without addition of MMT at 5 minutes

 A slight difference between spectrum at 920 cm-1 that corresponded to hydrated
silica 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 may
have been because of hardening reaction that took place.

 Cements with MMT easily to form hard surface and less working time compare than
cements without MMT.

 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.

[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.

[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.

Setting reaction & compressive strength of GPC

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