- Email: [email protected]
Influence of nanostructured hydroxyapatite on an experimental adhesive resin
e79
d e n t a l m a t e r i a l s 2 7 S ( 2 0 1 1 ) e1–e84
dimension of the resulting 48 surfaces (6 × 2 × 4) was evaluated using a variety of techniques including Minkowski cover (MC), root mean square roughness vs. area (RMS), Kolmogorov box (KB), Hurst exponent (HE), Slit Island Box (SIB), and Slit Island Richardson (SR). The coefficient of variation (CV) was used to identify the techniques with best precision (lowest CV). CV and D* data were analyzed using three-way ANOVA with Tukey’s HSD for post hoc tests. Results: The effect of method on mean D* was shown to be very significant (p < 0.0001). A water environment resulted in significantly lower mean D* values than did a saliva environment for KB, HE, and SIB, but not for RMS, MC, or SR, so there was an interaction between method and environment (p = 0.023). Angles of inclination up to 7 degrees did not have a significant effect on mean D* or CV (p = 0.89, p = 0.11). The method of calculation did have a significant effect on CV (p < 0.0001), with the CV values for RMS being statistically lower than all other methods tested for both water and saliva environments. Environment did not have a significant effect on CV (p = 0.94), and no interactions between experimental factors were noted with respect to CV. Conclusions: RMS was determined to have the best precision of the techniques measured on silica glass fracture surfaces, and a novel protocol for rapidly imaging fracture surfaces, levelling the surfaces, and measuring their fractal dimensions was established. NIH-NIDCR grants DE013358 and DE017991. doi:10.1016/j.dental.2011.08.582 P6 Fatigue loading and R-curve behavior of a fluorapatite glassceramic G.V. Joshi 1,∗ , Y. Duan 1 , K. S.T. John 1 , T.J. Hill 2 , A. Della Bona 3 , J.A. Griggs 1 1
University of Mississippi Med. Ctr., USA Ivoclar-Vivadent, Inc., USA 3 University of Passo Fundo, Brazil 2
Objectives: The objective of the study was to determine the effects of surface finish and mechanical loading on the rising toughness curve (R-curve) behavior of a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). Materials and methods: Rectangular beam specimens with dimensions of 25 mm × 4 mm × 1.2 mm were fabricated using the press-on technique. Two groups of specimens (N = 30) with polished (15 m diamond) or air abraded (100 m Al2 O3 , 2 bar) surfaces were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2 Hz (N = 44) and 10 Hz (N = 36), and at different stress amplitudes. All tests were performed using a fully articulating four-point flexure fixture in deionized water at 37 ◦ C. Fractographic techniques were used to determine the critical flaw sizes for estimating fracture toughness. To determine the presence of R-curve behavior, non-linear regression was used, KIc = ˇ0 + ˇ1 [1 − exp(−ˇ2 c)], where c is the radius of a semi-circular flaw with stress intensity factor equal to the observed semi-elliptical flaw. Forward stepwise regression was performed to determine the effects on fracture toughness of different variables, such as initial flaw type, critical flaw size,
critical flaw eccentricity, cycling frequency, peak load, and number of cycles. Results: The majority of failures for the air abraded specimens originated from air abrasion flaws. The primary initial flaw type for the polished specimens tested under rapid monotonic loading was surface porosity, while the polished specimens tested under cyclic loading exhibited approximately equal proportions of surface porosity and grinding flaws. The results of the non-linear regression are summarized in the table below. The p-values for the entire regression model were significant (p ≤ 0.05) for both loading methods (rapid monotonic loading and fatigue). The regression model for rapid monotonic loading showed a large scatter in data points and a low r2 value. The values for the fracture toughness ranged from 0.75 to 1.1 MPa m1/2 and reached a plateau at different critical flaw sizes based on loading method. For both loading methods, critical flaw dimensions had significant effects (p ≤ 0.05) on the fracture toughness, while all of the other factors mentioned above did not have significant effects (p > 0.05). Coefficient
Rapid monotonic loading Value
ˇ0 ˇ1 ˇ2 Total
r2
−0.0348 1.0122 0.0227 0.1999
Fatigue
p-Value
Value
0.9807 0.4748 0.1873
0.2812 0.8774 0.0038
0.0053
Total
r2
p-Value 0.2506 <0.0001 0.0395
0.6990
<0.0001
Conclusions: The loading method and critical flaw dimensions had significant effects on R-curve behavior of this fluorapatite glass-ceramic. Supported by NIH grants 5R01 DE013358 and 5R01 DE017991. doi:10.1016/j.dental.2011.08.583 P7 Influence of nanostructured hydroxyapatite on an experimental adhesive resin V.C.B. Leitune ∗ , F.M. Collares, R.M. Trommer, C.P. Bergmann, S.M.W. Samuel Federal University of Rio Grande do Sul, Porto Alegre, Brazil Objectives: The purpose of this study was to evaluate the influence of nanostructured hydroxyapatite addition to an experimental adhesive resin. Materials and methods: The organic phase of adhesive resin was prepared by mixing 50 wt.% Bis-GMA, 25 wt.% TEGDMA, and 25 wt.% HEMA. Camphoroquinone and EDAB were added at 1 mol% for all groups as polymerization initiators. No radical scavenger was added. Nanostructured hydroxyapatite (HAnano ) was added at seven different concentrations: 0, 0.5, 1, 2, 5, 10 and 20 wt.%. HAnano was obtained by a flame-based process and submitted to the silanization process with V-MTPS. To perform monomer photo-activation, a light emitting diode unit (Radii, SDI) was used. An irradiation value of 1200 mW/cm2 was confirmed with a digital power meter (Ophir Optronics, USA). HAnano particles were characterized for their morphology (SEM) and specific surface area (B.E.T.). Adhesive resins with hydroxyapatite incorporation were evaluated by Knoop microhardness, softening in solvent (absolute
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d e n t a l m a t e r i a l s 2 7 S ( 2 0 1 1 ) e1–e84
ethanol), flexural strength and radiopacity. Data were analyzed by one-way ANOVA and Tukey’s test (˛ = 0.05), except for softening in solvent (paired t-test). Results: Particles characterization showed nanostructures with 15.096 m2 /g of specific surface area and a mean size of 26.7 nm. Microhardness and softening in solvent are shown in Table 1. The incorporation of HAnano did not influence the flexTable 1 – Microhardness values of the model adhesives before (KHN1) and after the immersion in solvent (KHN2) and the variation of microhardness values (KHN%). Groups 0% 0.5% 1% 2% 5% 10% 20%
KHN1
KHN2
KHN%
22.6 (±0.6)Ba 22.8 (±1.9)Ba 22.7 (±0.9)Ba 23.2 (±0.3)Ba 23.4 (±0.4)Ba 23.9 (±0.2)Aa 25.1 (±0.8)Aa
15.3 (±2.4)b 18.5 (±0.8)b 18.9 (±0.7)b 18.6 (±1.0)b 20.2 (±0.6)b 20.7 (±0.3)b 22.7 (±0.8)b
32.4 (±9.6)C 18.7 (±7.0)B 16.7 (±2.9)B 19.6 (±4.7)B 13.9 (±1.9)B 13.3 (±1.1)B 9.6 (±4.7)A
Different capital letters in the same column indicate statistical difference (p < 0.05). Different small letters in the same row indicate statistical difference (p < 0.05).
sorption (WS) and solubility (SL) evaluation was conducted based on the ISO 4049:2000. The degree of conversion (DC) and kinetics of polymerization by RT-FTIR analysis were obtained in a spectrophotometer (Shimadzu). FS after 24 h, WS and SL were analyzed using One-Way ANOVA and Tukey’s test (p < 0.05). Results: DC, mean values for FS, WS and SL and standard deviation (±SD). SD
FS (MPa) 24 h
7dw
7e
g/mm3
% DC
A 37.8b
(3.9)
WS SL ♥ 69.5 (1.2) 7.1♠ (3.1)
B 19.7b
P10
♥ (3.1) B 64.0a (4.9) 85.5♥ (7.3) C 40.9a (4.2)
(3.0)
89.4♠ (2.2)
B10
97.8 (2.8) A 74.5a (2.9) A 41.7b (1.1)
51.4䊉 (2.8)
P4
B30 UP4 H
91.9
84.7♥ (6.6) C 41.6a (5.0)
(3.1)
79.4 (2.4)
111.8♠ (8.6) A 75.7a (7.4) A 37.7b (1.6) 112.9♠ (6.2) B 65.3a (3.6) B 22.5b (2.3)
59.3♣ (2.7) 85.9♠ (3.1)
B 19.0b
65
1.8♠ (1.6) 63
−0.4♥ (1.2)
65
1.1♥ (0.7) 69 0.4♥ (2.0) 58 4.3♠ (2.4) 49
Differences between resin adhesive groups are represented by different superscripts symbols. FS after storage in the solutions (dw: distilled water; e: ethanol) was analyzed using Two-Way ANOVA (monomer and storage solution factors) and Tukey’s test (p < 0.05), where capital letters in columns indicate differences between the resin adhesive groups whereas different small letters at the same row represent differences for storage solution (p < 0.05).
ural strength (ranged from 123.3 to 143.4 MPa) and radiopacity (p > 0.05). Radiopacity values did no present difference to 1 mm of aluminum. Conclusions: Incorporation of nanostructured hydroxyapatite up to 20 wt.% increased some evaluated properties, showing to be an available and promising alternative for adhesive resin.
Conclusions: The B10 and UP4 groups presented better physical and mechanical characteristics than the control (HEMA group).
doi:10.1016/j.dental.2011.08.584
A.D. Nogueira ∗ , A. Della Bona
P8 Physical and mechanical properties of experimental HEMAfree resin adhesives
Universidade de Passo Fundo, RS, Brazil
E.A. Munchow ∗ , C.H. Zanchi, F.A. Ogliari, E. Piva Federal University of Pelotas, Pelotas, RS, Brazil Objectives: Surfactant dimethacrylates (SD) have a potential use in the development of HEMA-free adhesive systems (Zanchi et al., J Dent 2010; 38: 503–508). The purpose of this study was to evaluate some physical and mechanical properties of five experimental HEMA-free resin adhesives. Materials and methods: Five experimental resin adhesives were prepared with one type of SD1 ,2 ,3 ,4 ,5 Bis-GMA, TEGDMA, CQ and EDAB, and a control group with HEMA instead using a SD. For flexural strength (FS) evaluation of 30 bar shaped specimens (12 mm × 2 mm × 2 mm) were made for each resin and stored dry for 24 h (control) or at 37 ◦ C for 7 days in different solutions: distilled water or ethanol 70% (n = 10). Then, a three-point flexural test was performed (EMIC DL-500). Water
1
Poly-ethyleneglicol (400) dimethacrylate (P4). Poly-ethyleneglicol (1000) dimethacrylate (P10); Ethoxilate bisphenol A diglycidyl dimethacrylate. 3 B10. 4 B30. 5 Poly-ethyleneglicol (400) extended urethane dimethacrylate (UP4). 2
doi:10.1016/j.dental.2011.08.585 P9 Translucency of dental ceramics tested by different methods
Objectives: To evaluate the translucency of different dental CAD–CAM ceramics using three distinct methods. Materials and Methods: CAD–CAM ceramic specimens (10 mm × 20 mm × 1 mm) were fabricated according to manufacturers’ instructions and polished to 1 m surface finish (n = 15). The direct transmittance percentage (T%) was measured from 300 to 800 nm wavelengths using a spectrophotometer (Lambda 20, Perkin Elmer, USA). The T% values at 525 nm wavelength were considered for this study. The ceramic specimens were placed on white and black backgrounds and the L* (lightness), a* (red-green) and b* (blue-yellow) coordinates of color were measured using a spectrophotometer (EasyShade, Vita Zahnfabrik, Germany) allowing for calculations of the translucency parameter (TP) and the contrast ratio (CR). TP, CR and T% values from the different groups were statistically analyzed by ANOVA and Tukey test. Methods were correlated using Pearson correlation coefficient (r). Results: See Table 1. Conclusions: As there is no a translucency standard method to examine this optical property, it is difficult to compare the translucency between dental materials. This rationale was demonstrated by the lack of a strong correlation between most of the methods examined, except for the TP-CR
d e n t a l m a t e r i a l s 2 7 S ( 2 0 1 1 ) e1–e84
dimension of the resulting 48 surfaces (6 × 2 × 4) was evaluated using a variety of techniques including Minkowski cover (MC), root mean square roughness vs. area (RMS), Kolmogorov box (KB), Hurst exponent (HE), Slit Island Box (SIB), and Slit Island Richardson (SR). The coefficient of variation (CV) was used to identify the techniques with best precision (lowest CV). CV and D* data were analyzed using three-way ANOVA with Tukey’s HSD for post hoc tests. Results: The effect of method on mean D* was shown to be very significant (p < 0.0001). A water environment resulted in significantly lower mean D* values than did a saliva environment for KB, HE, and SIB, but not for RMS, MC, or SR, so there was an interaction between method and environment (p = 0.023). Angles of inclination up to 7 degrees did not have a significant effect on mean D* or CV (p = 0.89, p = 0.11). The method of calculation did have a significant effect on CV (p < 0.0001), with the CV values for RMS being statistically lower than all other methods tested for both water and saliva environments. Environment did not have a significant effect on CV (p = 0.94), and no interactions between experimental factors were noted with respect to CV. Conclusions: RMS was determined to have the best precision of the techniques measured on silica glass fracture surfaces, and a novel protocol for rapidly imaging fracture surfaces, levelling the surfaces, and measuring their fractal dimensions was established. NIH-NIDCR grants DE013358 and DE017991. doi:10.1016/j.dental.2011.08.582 P6 Fatigue loading and R-curve behavior of a fluorapatite glassceramic G.V. Joshi 1,∗ , Y. Duan 1 , K. S.T. John 1 , T.J. Hill 2 , A. Della Bona 3 , J.A. Griggs 1 1
University of Mississippi Med. Ctr., USA Ivoclar-Vivadent, Inc., USA 3 University of Passo Fundo, Brazil 2
Objectives: The objective of the study was to determine the effects of surface finish and mechanical loading on the rising toughness curve (R-curve) behavior of a fluorapatite glass-ceramic (IPS e.max ZirPress, Ivoclar-Vivadent). Materials and methods: Rectangular beam specimens with dimensions of 25 mm × 4 mm × 1.2 mm were fabricated using the press-on technique. Two groups of specimens (N = 30) with polished (15 m diamond) or air abraded (100 m Al2 O3 , 2 bar) surfaces were tested under rapid monotonic loading. Additional polished specimens were subjected to cyclic loading at two frequencies, 2 Hz (N = 44) and 10 Hz (N = 36), and at different stress amplitudes. All tests were performed using a fully articulating four-point flexure fixture in deionized water at 37 ◦ C. Fractographic techniques were used to determine the critical flaw sizes for estimating fracture toughness. To determine the presence of R-curve behavior, non-linear regression was used, KIc = ˇ0 + ˇ1 [1 − exp(−ˇ2 c)], where c is the radius of a semi-circular flaw with stress intensity factor equal to the observed semi-elliptical flaw. Forward stepwise regression was performed to determine the effects on fracture toughness of different variables, such as initial flaw type, critical flaw size,
critical flaw eccentricity, cycling frequency, peak load, and number of cycles. Results: The majority of failures for the air abraded specimens originated from air abrasion flaws. The primary initial flaw type for the polished specimens tested under rapid monotonic loading was surface porosity, while the polished specimens tested under cyclic loading exhibited approximately equal proportions of surface porosity and grinding flaws. The results of the non-linear regression are summarized in the table below. The p-values for the entire regression model were significant (p ≤ 0.05) for both loading methods (rapid monotonic loading and fatigue). The regression model for rapid monotonic loading showed a large scatter in data points and a low r2 value. The values for the fracture toughness ranged from 0.75 to 1.1 MPa m1/2 and reached a plateau at different critical flaw sizes based on loading method. For both loading methods, critical flaw dimensions had significant effects (p ≤ 0.05) on the fracture toughness, while all of the other factors mentioned above did not have significant effects (p > 0.05). Coefficient
Rapid monotonic loading Value
ˇ0 ˇ1 ˇ2 Total
r2
−0.0348 1.0122 0.0227 0.1999
Fatigue
p-Value
Value
0.9807 0.4748 0.1873
0.2812 0.8774 0.0038
0.0053
Total
r2
p-Value 0.2506 <0.0001 0.0395
0.6990
<0.0001
Conclusions: The loading method and critical flaw dimensions had significant effects on R-curve behavior of this fluorapatite glass-ceramic. Supported by NIH grants 5R01 DE013358 and 5R01 DE017991. doi:10.1016/j.dental.2011.08.583 P7 Influence of nanostructured hydroxyapatite on an experimental adhesive resin V.C.B. Leitune ∗ , F.M. Collares, R.M. Trommer, C.P. Bergmann, S.M.W. Samuel Federal University of Rio Grande do Sul, Porto Alegre, Brazil Objectives: The purpose of this study was to evaluate the influence of nanostructured hydroxyapatite addition to an experimental adhesive resin. Materials and methods: The organic phase of adhesive resin was prepared by mixing 50 wt.% Bis-GMA, 25 wt.% TEGDMA, and 25 wt.% HEMA. Camphoroquinone and EDAB were added at 1 mol% for all groups as polymerization initiators. No radical scavenger was added. Nanostructured hydroxyapatite (HAnano ) was added at seven different concentrations: 0, 0.5, 1, 2, 5, 10 and 20 wt.%. HAnano was obtained by a flame-based process and submitted to the silanization process with V-MTPS. To perform monomer photo-activation, a light emitting diode unit (Radii, SDI) was used. An irradiation value of 1200 mW/cm2 was confirmed with a digital power meter (Ophir Optronics, USA). HAnano particles were characterized for their morphology (SEM) and specific surface area (B.E.T.). Adhesive resins with hydroxyapatite incorporation were evaluated by Knoop microhardness, softening in solvent (absolute
e80
d e n t a l m a t e r i a l s 2 7 S ( 2 0 1 1 ) e1–e84
ethanol), flexural strength and radiopacity. Data were analyzed by one-way ANOVA and Tukey’s test (˛ = 0.05), except for softening in solvent (paired t-test). Results: Particles characterization showed nanostructures with 15.096 m2 /g of specific surface area and a mean size of 26.7 nm. Microhardness and softening in solvent are shown in Table 1. The incorporation of HAnano did not influence the flexTable 1 – Microhardness values of the model adhesives before (KHN1) and after the immersion in solvent (KHN2) and the variation of microhardness values (KHN%). Groups 0% 0.5% 1% 2% 5% 10% 20%
KHN1
KHN2
KHN%
22.6 (±0.6)Ba 22.8 (±1.9)Ba 22.7 (±0.9)Ba 23.2 (±0.3)Ba 23.4 (±0.4)Ba 23.9 (±0.2)Aa 25.1 (±0.8)Aa
15.3 (±2.4)b 18.5 (±0.8)b 18.9 (±0.7)b 18.6 (±1.0)b 20.2 (±0.6)b 20.7 (±0.3)b 22.7 (±0.8)b
32.4 (±9.6)C 18.7 (±7.0)B 16.7 (±2.9)B 19.6 (±4.7)B 13.9 (±1.9)B 13.3 (±1.1)B 9.6 (±4.7)A
Different capital letters in the same column indicate statistical difference (p < 0.05). Different small letters in the same row indicate statistical difference (p < 0.05).
sorption (WS) and solubility (SL) evaluation was conducted based on the ISO 4049:2000. The degree of conversion (DC) and kinetics of polymerization by RT-FTIR analysis were obtained in a spectrophotometer (Shimadzu). FS after 24 h, WS and SL were analyzed using One-Way ANOVA and Tukey’s test (p < 0.05). Results: DC, mean values for FS, WS and SL and standard deviation (±SD). SD
FS (MPa) 24 h
7dw
7e
g/mm3
% DC
A 37.8b
(3.9)
WS SL ♥ 69.5 (1.2) 7.1♠ (3.1)
B 19.7b
P10
♥ (3.1) B 64.0a (4.9) 85.5♥ (7.3) C 40.9a (4.2)
(3.0)
89.4♠ (2.2)
B10
97.8 (2.8) A 74.5a (2.9) A 41.7b (1.1)
51.4䊉 (2.8)
P4
B30 UP4 H
91.9
84.7♥ (6.6) C 41.6a (5.0)
(3.1)
79.4 (2.4)
111.8♠ (8.6) A 75.7a (7.4) A 37.7b (1.6) 112.9♠ (6.2) B 65.3a (3.6) B 22.5b (2.3)
59.3♣ (2.7) 85.9♠ (3.1)
B 19.0b
65
1.8♠ (1.6) 63
−0.4♥ (1.2)
65
1.1♥ (0.7) 69 0.4♥ (2.0) 58 4.3♠ (2.4) 49
Differences between resin adhesive groups are represented by different superscripts symbols. FS after storage in the solutions (dw: distilled water; e: ethanol) was analyzed using Two-Way ANOVA (monomer and storage solution factors) and Tukey’s test (p < 0.05), where capital letters in columns indicate differences between the resin adhesive groups whereas different small letters at the same row represent differences for storage solution (p < 0.05).
ural strength (ranged from 123.3 to 143.4 MPa) and radiopacity (p > 0.05). Radiopacity values did no present difference to 1 mm of aluminum. Conclusions: Incorporation of nanostructured hydroxyapatite up to 20 wt.% increased some evaluated properties, showing to be an available and promising alternative for adhesive resin.
Conclusions: The B10 and UP4 groups presented better physical and mechanical characteristics than the control (HEMA group).
doi:10.1016/j.dental.2011.08.584
A.D. Nogueira ∗ , A. Della Bona
P8 Physical and mechanical properties of experimental HEMAfree resin adhesives
Universidade de Passo Fundo, RS, Brazil
E.A. Munchow ∗ , C.H. Zanchi, F.A. Ogliari, E. Piva Federal University of Pelotas, Pelotas, RS, Brazil Objectives: Surfactant dimethacrylates (SD) have a potential use in the development of HEMA-free adhesive systems (Zanchi et al., J Dent 2010; 38: 503–508). The purpose of this study was to evaluate some physical and mechanical properties of five experimental HEMA-free resin adhesives. Materials and methods: Five experimental resin adhesives were prepared with one type of SD1 ,2 ,3 ,4 ,5 Bis-GMA, TEGDMA, CQ and EDAB, and a control group with HEMA instead using a SD. For flexural strength (FS) evaluation of 30 bar shaped specimens (12 mm × 2 mm × 2 mm) were made for each resin and stored dry for 24 h (control) or at 37 ◦ C for 7 days in different solutions: distilled water or ethanol 70% (n = 10). Then, a three-point flexural test was performed (EMIC DL-500). Water
1
Poly-ethyleneglicol (400) dimethacrylate (P4). Poly-ethyleneglicol (1000) dimethacrylate (P10); Ethoxilate bisphenol A diglycidyl dimethacrylate. 3 B10. 4 B30. 5 Poly-ethyleneglicol (400) extended urethane dimethacrylate (UP4). 2
doi:10.1016/j.dental.2011.08.585 P9 Translucency of dental ceramics tested by different methods
Objectives: To evaluate the translucency of different dental CAD–CAM ceramics using three distinct methods. Materials and Methods: CAD–CAM ceramic specimens (10 mm × 20 mm × 1 mm) were fabricated according to manufacturers’ instructions and polished to 1 m surface finish (n = 15). The direct transmittance percentage (T%) was measured from 300 to 800 nm wavelengths using a spectrophotometer (Lambda 20, Perkin Elmer, USA). The T% values at 525 nm wavelength were considered for this study. The ceramic specimens were placed on white and black backgrounds and the L* (lightness), a* (red-green) and b* (blue-yellow) coordinates of color were measured using a spectrophotometer (EasyShade, Vita Zahnfabrik, Germany) allowing for calculations of the translucency parameter (TP) and the contrast ratio (CR). TP, CR and T% values from the different groups were statistically analyzed by ANOVA and Tukey test. Methods were correlated using Pearson correlation coefficient (r). Results: See Table 1. Conclusions: As there is no a translucency standard method to examine this optical property, it is difficult to compare the translucency between dental materials. This rationale was demonstrated by the lack of a strong correlation between most of the methods examined, except for the TP-CR