IADR Abstract Archives
Bond Durability of Phosphate Monomers with Different Molecular Structure/Purity
Objective: Phosphate functional monomers can chemically interact with dentinal hydroxyapatite, being thought of importance for bond durability. We determined the bond durability to dentin of experimental adhesives containing phosphate functional monomers that differ in molecular structure and purity.
Methods: Experimental self-etch primers were prepared consisting of 15wt% functional monomer (all provided by Kuraray Noritake (KN) except 4-MET by Sun Medical), either 2-methacryloyloxyethyl dihydrogen phosphate (2-MEP), 4-methacryloxyethyl trimellitic acid (4-MET), 6-methacryloyloxyhexyl dihydrogen phosphate (6-MHP), 10-methacryloxydecyl dihydrogen phosphate (10-MDP), or 6-methacryloxy-2,2,3,3,4,4,5,5-octafluorohexyl dihydrogen phosphate (MF8P), dissolved in 45/40wt% ethanol/water. Clearfil AP-X (KN) composite was bonded to 600-grit SiC-ground human dentin after the primer was rubbed for 20 sec, air-dried, and Clearfil SE Bond (KN) was light-cured (BluePhase G2, Vivadent Ivoclar). Prepared micro-specimens were subjected to micro-tensile bond strength (µTBS) testing after 24hr and 100,000 thermocycles (TC). In addition, similar experimental primers based on 10-MDP, either provided by KN (10-MDP_KN: purity grade not released, but informed to be higher than that of the other 10-MDP's, pH=2.03), by PCM (10-MDP_PCM: 83% purity following PCM, pH=2.73), or by DMI (10-MDP_DMI: 90% purity following DMI, pH=2.66), were tested likewise when the monomers were freshly received (‘fresh') or after they were frozen (-18°C) for 1y (‘1y'). The interaction of the ‘fresh' monomers with dentin was characterized using XRD.
Results:
| 2-MEP
| 4-MET
| 6-MHP
| 10-MDP
| MF8P
|
24hr
| 1.1±2.5d(0/17)
| 10.9±8.7ab(0/47)
| 9.9±5.2ab(0/26)
| 17.4±7.8c(0/22)
| 13±6.6ac(0/41)
|
TC
| pft*
| 7.5±3.8a(1/22)
| 7.4±8.6a(9/23)
| 16.0±5.5bc(0/22)
| 16.3±10.9bc(0/19)
|
Mean±SD (ptf/n); ptf*=all pre-testing failures; different superscript letters indicate significant difference (2-way ANOVA: p<0.05).
| 10-MDP_KN_‘fresh'
| 10-MDP_KN_‘1y'
| 10-MDP_PCM_‘fresh'
| 10-MDP_PCM_‘1y'
| 10-MDP_DMI_‘fresh'
| 10-MDP_DMI_'1y'
|
24hr
| 21±10.0(0/33)a
| 17.4±7.8(0/22)ab
| 17.6±11.1(0/52)a
| 10.3±5.1(0/26)c
| 10.8±3.9(0/24)c
| *
|
TC
| *
| 16.0±5.5(0/22)ab
| 9.9±8.3(2/24)bcd
| 4.3±3.0(5/22)d
| *
| *
|
Mean±SD (ptf/n); *not (yet) available; different superscript letters indicate significant difference between Weibull B63.2 95% confidence intervals.
XRD revealed significantly more intense nano-layering for 10-MDP_KN_'fresh' than for 10-MDP_PCM_'fresh' and 10-MDP_DMI_'fresh', in line with the (assumed) purity grade of the monomers.
Conclusion: The monomers 10-MDP and MF8P resulted in higher and more stable bonding effectiveness. A higher and more durable bonding effectiveness was also achieved for 10-MDP with an (assumed) higher purity grade.