Setting reaction & compressive strength of GPC

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  • 1.  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
  • 2. 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 ofFocused on the optimization of GPCs in term of: -Compressive strength -Setting reaction
  • 3. Objectives1. To follow the setting reaction of GPCs2. To study influence of MMT on compressive strength of GPC3. To investigate the influence of Na on the setting reaction of cement
  • 4.  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
  • 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.
  • 6.  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.
  • 7.  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.
  • 8.  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
  • 9.  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
  • 10. 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)
  • 11. RESULTS &DISCUSSION
  • 12. 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).
  • 13. 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.
  • 14.  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.
  • 15.  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.
  • 16.  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.
  • 17.  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
  • 18. 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 ionsfrom the silica network.• 850 – 500 cm-1 due to extraneous ion such Ca2+ and Na+ thatincorporated in glass phase[8].[8] Farmer V.C., The infrared spectra of mineral. Mineralogical Soc., London.p 469, 1974.
  • 19. 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.
  • 20.  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.
  • 21.  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.
  • 22. • 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.
  • 23.  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.
  • 24. 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-1Figure 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.
  • 25.  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.
  • 26.  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.
  • 27. [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.