ricardo carvalho - Academia.edu (original) (raw)
Papers by ricardo carvalho
Dental Materials, 2004
Este estudo examinou o efeito do agente clareador peróxido de carbamida a 10% e a 16% na microdur... more Este estudo examinou o efeito do agente clareador peróxido de carbamida a 10% e a 16% na microdureza superficial de cerâmicas feldspáticas micro-particuladas (VM7 e VM13, Vita Zahnfabrik). Quarenta corpos-de-prova (8 mm de diâmetro, 2 mm de espessura) foram divididos em quatro grupos (n=10): G1-VM7 + 10% Whiteness, G2-VM7 + 16% Whiteness, G3-VM13 + 10% e G4-VM13 + 16% Whiteness. Os agentes clareadores foram aplicados por 8 horas durante 15 dias e os cp foram armazenados em água destilada a 37°C. A dureza Vicker's (HV) de cada cp foi determinada. Os dados foram analisados pelos testes de Wilcoxon e Mann-Whitney (p<0.05). Os valores da dureza antes da exposição ao agente clareador foram: g1-433 (57); g2-486 (22); g3-509 (28); g4-518 (24), e depois da exposição: G1-349 (32); G2-496 (95); G3-519 (38); G4-502 (81). G1 exibiu diferença significante e microdureza maior comparado ao G2 nos grupos da VM7 e o efeito da concentração do clareador foi significante, apresentados através dos testes Mann-Whitney. Para VM13, ambos testes, Wilcoxon e Mann-Whitney, não apresentaram diferença significante. Quando o peróxido de carbamida a 10% foi avaliado, a microdureza da cerâmica VM7 foi afetada, e não houve diferença na microdureza entre as cerâmicas VM7 e VM13 quando o peróxido de carbamida a 16% foi utilizado. ABSTRACT This study examined the effect Whiteness. The home-use bleaching agents were applied for 8 hours on 15 days, and the specimens were stored in distilled water at 37°C. The Vicker's hardness number (HV) was determined for each specimen. Data were analyzed by the Wilcoxon and Mann-Whitney tests (p<0.05). The microhardness values before exposure were: g1-433 ; g2-486 (22); g3-509 (28); g4-518 (24), and after exposure: G1-349 (32); G2-496 (95); G3-519 (38); G4-502 (81). G1 exhibited a higher and significant difference than G2 in VM7 groups, and the effect of bleaching concentration was shown to be significant by the Mann-Whitney test. And for VM13, both the Wilcoxon and Mann-Whitney tests showed no significant differences. When using 10% carbamide peroxide, the microhardness of VM7 ceramic was affected, and there were no effect on the microhardness between VM7 and VM13 ceramics when 16% carbamide peroxide was used.
Journal of Biomedical Materials Research, 2004
This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-et... more This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-etching adhesives (Adper Prompt—AD, and One-up Bond F—OB), two two-step, self-etching primers (Clearfil SE Bond—CF, and Unifil Bond—UB), and one two-step, total-etch adhesive (Single Bond—SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37°C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm-thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO3 for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 μm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 90–98, 2004
Dental Materials, 2004
Objective. This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) an... more Objective. This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) and dentin -enamel junction (DEJ) using the microtensile technique. It was hypothesized that the UTS of dental structures varies according to location and nature.
Dental Materials, 2007
All other uses, reproduction and distribution, including without limitation commercial reprints, ... more All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial A u t h o r ' s p e r s o n a l c o p y d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 705-713 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a A u t h o r ' s p e r s o n a l c o p y 706 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 705-713
Dental Materials, 2006
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx-xxx a v a i l a b l e a t w w w . s c i e n c... more d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx-xxx a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a a b s t r a c t
Dental Materials, 1995
Adhesion testing of dentin bonding agents was reviewed starting with the adhesion substrate, dent... more Adhesion testing of dentin bonding agents was reviewed starting with the adhesion substrate, dentin, the variables involved in etching, priming and bonding, storage variables and testing variables. Several recent reports attempting to standardize many of these variables were discussed. Recent advances in the development of new bonding systems have resulted in bond strengths on the order of 20-30 MPa. At these high bond strengths, most of the bond failure modes have been cohesive in dentin. As this precludes measurement of interfacial bond strength, new testing methods must be developed. One such new method, a microtensile method, was described along with preliminary results that have been obtained.
Dental Materials, 2003
Objectives. The aim of this study was to test the null hypothesis that the tensile properties of ... more Objectives. The aim of this study was to test the null hypothesis that the tensile properties of demineralized dentin are not influenced by the hydrogen bonding ability of anhydrous polar solvents.
Dental Materials, 1998
Objectives. Little research has been done to evaluate the effects of acids commonly used in adhes... more Objectives. Little research has been done to evaluate the effects of acids commonly used in adhesive dentistry, on the tensile properties of the demineralized dentin matrix. The purpose of this study was to evaluate the effects of a number of acidic conditioners on the ultimate tensile strength (UTS) and modulus of elasticity (E) of human coronal dentin matrix. Methods. Small hour-glass shaped (for UTS) or I-beam shaped (for determination of E) were prepared from mid-coronal dentin of extracted human third molars. After protecting the ends with varnish, the middle of the specimens was completely demineralized in 0.5 M EDTA (pH 7). UTS was determined by tensile stressing to failure. Modulus of elasticity was calculated from stress strain curves. The results were analyzed by ANOVA and Student-Neuman-Keuls test at the 95% confidence level. Results. Brief (ca. 1-2 min) exposure of demineralized dentin matrix to acids had no measurable effects on its tensile properties. Tenminute exposures to 2.5% and 17.5% nitric acid lowered (p Ͻ 0.05) the UTS compared to phosphate buffered saline (PBS)-exposed controls. Exposure of the decalcified dentin to 10% citric acid containing 3% ferric chloride, 10% citric acid, 37% phosphoric acid or 17.5% nitric acid containing 3% ferric chloride for 10 min had no effect on UTS. None of these acids consistently lowered stiffness. Significance. The results indicate that relatively long exposures to acids are required to alter the tensile properties of demineralized dentin. It is unlikely that the brief exposures to acids that are used in adhesive dentistry would acutely weaken the physical properties of demineralized dentin. However, long-term studies should be done to determine if such treatment increases the susceptibility of the matrix to hydrolysis. ᭧ 1998 Published by Elsevier Science Ltd on behalf of the Academy of Dental Materials 222 Zhang et al./Effects of acid on collagen strength
Journal of Dentistry, 2002
Objectives. This study tested the hypotheses that micro-tensile bond strengths of all currently a... more Objectives. This study tested the hypotheses that micro-tensile bond strengths of all currently available single-step adhesives to dentine are adversely affected by delayed activation of a light-cured composite, and that such a phenomenon only occurs in the presence of water from the substrate side of the bonded interface.
Biomaterials, 2005
As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high conce... more As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high concentrations, the adhesive becomes more hydrophilic. Water sorption by polymers causes plasticization and lowers mechanical properties. The purpose of this study was to compare the water sorption and modulus of elasticity (E) of five experimental neat resins (EX) of increasing hydrophilicity, as ranked by their Hoy's solubility parameters and five commercial resins. Methods: After measuring the initial modulus of all resin disks by biaxial flexure, half the specimens were stored in hexadecane and the rest were stored in water. Repeated measurements of stiffness were made for 3 days. Water sorption and solubility measurements were made in a parallel experiment. Results: None of the specimens stored in oil showed any significant decrease in modulus. All resins stored in water exhibited a time-dependent decrease in modulus that was proportional to their degree of water sorption. Water sorption of EX was proportional to Hoy's solubility parameter for polar forces (d p ) with increasing polarity resulting in higher sorption. The least hydrophilic resin absorbed 0.55 wt% water and showed a 15% decrease in modulus after 3 days. The most hydrophilic experimental resin absorbed 12.8 wt% water and showed a 73% modulus decrease during the same period. The commercial resins absorbed between 5% and 12% water that was associated with a 19-42% reduction in modulus over 3 days. r
Dental Materials, 2005
Objectives: To evaluate the effects of long-term storage on the mechanical properties of the comp... more Objectives: To evaluate the effects of long-term storage on the mechanical properties of the components of resin -dentin bonds, that is, resin composite, adhesive system, demineralized and mineralized dentin.
Journal of Endodontics, 2006
This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin mo... more This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice pushout tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention. (J Endod 2006;32:537-540)
Biomaterials, 2005
This study examined the extent of organic solvent and water retention in comonomer blends with di... more This study examined the extent of organic solvent and water retention in comonomer blends with different hydrophilicity (Hoy's solubility parameter for hydrogen bonding, δ h ) after solvent evaporation, and the extent of tracer penetration in polymerised films prepared from these resins. For each comonomer blend, adhesive/solvent mixtures were prepared by addition of [1] 50wt% acetone; [2] 50wt% ethanol [3] 30wt% acetone and 20wt% water; and [4] 30wt% ethanol and 20wt% water. The mixtures were placed in glass wells and evaporated for 30-60 s for acetone-based resins, and 60-120 s for ethanol-based resins. The weight of the comonomer mixtures was measured before and after solvent evaporation. Resin films were prepared for transmission electron microscopy (TEM) after immersion in ammoniacal silver nitrate. The percentages of solvent and water retained in the comonomer mixtures, and between the acetone and ethanol groups were measured gravimetrically and were statistically compared. In comonomer-organic solvent mixtures, the percentage of solvent retained in acetone and ethanol-based mixtures significantly increased with hydrophilicity of the comonomer blends (P<0.05). In resin-organic solvent-water mixtures, significantly more solvent and water were retained in the ethanol-based mixtures (P<0.0001), when compared to acetone-based mixtures after 60 s air-drying. TEM revealed residual water being trapped as droplets in resin films containing acetone and water. Water-filled channels were seen along the film periphery of all groups and throughout the entire resin films containing ethanol and water. The addition of water to comonomer-ethanol mixtures results in increased retention of both ethanol and water because both solvents can hydrogen bond to the monomers.
Biomaterials, 2006
This study examined the effects of copolymer hydrophilicity and temperature on water sorption and... more This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter x 1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s total cohesive energy density (delta(t)), Hoy&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s solubility parameter for polar forces (delta(p)) and hydrogen bonding (delta(h)), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35-51 kJ/mol for copolymer blends R1-R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin-dentine bonds.
Dental Clinics of North America, 2002
In his classic thesis work on pulpal tissue reactions to restorative procedures and materials, La... more In his classic thesis work on pulpal tissue reactions to restorative procedures and materials, Langeland [1] drew a number of important conclusions. Among them was that ''dentin exposed by preparation of cavities or abutments should be covered immediately with a non-irritating material that does not permit leakage.'' That is, he recommended that dentin be sealed. At that time, there was no knowledge of smear layers or adhesion of materials to dentin. Most restorative materials in use then did not adapt perfectly to cavity walls and left gaps between the walls and the materials, permitting oral bacteria to colonize the gaps and to shed bacterial products to the pulp, where they could cause pulpal inflammation. Pulpal inflammation can be induced simply by leaving dentin cavities open to the oral environment . Brännströ m and Nyborg proposed that the presence of microorganisms in gaps between cavity walls and restorative materials was the major cause of pulpal inflammation after restorative treatment. Bergenholtz and Lindhe and Bergenholtz demonstrated that cell-free bacterial products could induce pulpal inflammation through freshly prepared dentin, Dent Clin N Am 46
European Journal of Oral Sciences, 2006
Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental ... more Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental adhesives are acidic (pH 1.5–2.7) and may activate dentin MMPs. The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic and collagenolytic activities in powdered mineralized dentin. Powdered dentin made from human teeth was mixed with all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the adhesives using acetone. Fresh untreated mineralized dentin powder had a gelatinolytic activity of 3.31 ± 0.39 relative fluorescent units (RFU) per mg dry weight (24 h) that increased, over storage time, to 87.5 RFU mg−1 (24 h) after 6–8 wk. When fresh powder was treated with acidic Tri-S Bond, the gelatinolytic activity increased from 3.24 ± 0.70 RFU mg−1 to > 112.5 RFU mg−1 (24 h) after 20 min and then remained unchanged. Monomers with lower pH values produced less activity. There was a significant, direct correlation between gelatinolytic activity and pH, with Tri-S giving the highest activity. Coating dentin powder with Tri-S resin prevented fluorescent substrates from gaining access to the enzyme, even though it activated the enzyme. In conclusion, self-etch adhesives may activate latent MMP and increase the activity to near-maximum levels and contribute to the degradation of resin–dentin bonds over time.
Journal of Dentistry, 2003
Objectives. To evaluate the microtensile bond strength of total-etch or selfetch adhesives to car... more Objectives. To evaluate the microtensile bond strength of total-etch or selfetch adhesives to caries-affected versus normal dentine, and to correlate these bond strengths with DIAGNOdent laser fluorescence and Knoop microhardness (KH) measurements of the substrates.
Biomaterials, 2005
This study provided morphological evidence that discrepancies between the depth of demineralisati... more This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives. r
Dental Materials, 2004
Este estudo examinou o efeito do agente clareador peróxido de carbamida a 10% e a 16% na microdur... more Este estudo examinou o efeito do agente clareador peróxido de carbamida a 10% e a 16% na microdureza superficial de cerâmicas feldspáticas micro-particuladas (VM7 e VM13, Vita Zahnfabrik). Quarenta corpos-de-prova (8 mm de diâmetro, 2 mm de espessura) foram divididos em quatro grupos (n=10): G1-VM7 + 10% Whiteness, G2-VM7 + 16% Whiteness, G3-VM13 + 10% e G4-VM13 + 16% Whiteness. Os agentes clareadores foram aplicados por 8 horas durante 15 dias e os cp foram armazenados em água destilada a 37°C. A dureza Vicker's (HV) de cada cp foi determinada. Os dados foram analisados pelos testes de Wilcoxon e Mann-Whitney (p<0.05). Os valores da dureza antes da exposição ao agente clareador foram: g1-433 (57); g2-486 (22); g3-509 (28); g4-518 (24), e depois da exposição: G1-349 (32); G2-496 (95); G3-519 (38); G4-502 (81). G1 exibiu diferença significante e microdureza maior comparado ao G2 nos grupos da VM7 e o efeito da concentração do clareador foi significante, apresentados através dos testes Mann-Whitney. Para VM13, ambos testes, Wilcoxon e Mann-Whitney, não apresentaram diferença significante. Quando o peróxido de carbamida a 10% foi avaliado, a microdureza da cerâmica VM7 foi afetada, e não houve diferença na microdureza entre as cerâmicas VM7 e VM13 quando o peróxido de carbamida a 16% foi utilizado. ABSTRACT This study examined the effect Whiteness. The home-use bleaching agents were applied for 8 hours on 15 days, and the specimens were stored in distilled water at 37°C. The Vicker's hardness number (HV) was determined for each specimen. Data were analyzed by the Wilcoxon and Mann-Whitney tests (p<0.05). The microhardness values before exposure were: g1-433 ; g2-486 (22); g3-509 (28); g4-518 (24), and after exposure: G1-349 (32); G2-496 (95); G3-519 (38); G4-502 (81). G1 exhibited a higher and significant difference than G2 in VM7 groups, and the effect of bleaching concentration was shown to be significant by the Mann-Whitney test. And for VM13, both the Wilcoxon and Mann-Whitney tests showed no significant differences. When using 10% carbamide peroxide, the microhardness of VM7 ceramic was affected, and there were no effect on the microhardness between VM7 and VM13 ceramics when 16% carbamide peroxide was used.
Journal of Biomedical Materials Research, 2004
This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-et... more This study evaluated the nanoleakage patterns in bonded interfaces using two single-step, self-etching adhesives (Adper Prompt—AD, and One-up Bond F—OB), two two-step, self-etching primers (Clearfil SE Bond—CF, and Unifil Bond—UB), and one two-step, total-etch adhesive (Single Bond—SB). Dentin surfaces were bonded with the adhesive systems and stored in water at 37°C for 1 week and 6 months. After storage periods, teeth were sectioned into 0.8 mm-thick slabs, coated with nail varnish except for the bonded interfaces, and immersed in ammoniacal AgNO3 for 24 h. After immersion in photodeveloping solution, bonded sections were prepared and observed under a SEM using the backscattered electron mode. Undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. Nanoleakage patterns were qualitatively compared between periods. Nanoleakage was observed in all bonded specimens at both periods. CF and UB presented silver deposits predominantly restricted to the thin (0.5 μm) hybrid layer (HL) at both periods. Although no evident differences were observed in the nanoleakage pattern of UB at 7 days and 6 months, CF presented enlarged areas of silver impregnation after 6 months. SB presented accumulation of silver particles mostly within the HL at 7 days, which was intensified after 6 months. AD and OB presented massive silver accumulation within the HL and the overlying adhesive layer. No evident differences were noticed between storage periods. Silver impregnation increased for all adhesive systems from 7 days to 6 months, except for UB. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 90–98, 2004
Dental Materials, 2004
Objective. This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) an... more Objective. This study determined the ultimate tensile strength (UTS) of enamel (E), dentin (D) and dentin -enamel junction (DEJ) using the microtensile technique. It was hypothesized that the UTS of dental structures varies according to location and nature.
Dental Materials, 2007
All other uses, reproduction and distribution, including without limitation commercial reprints, ... more All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution's website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial A u t h o r ' s p e r s o n a l c o p y d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 705-713 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a A u t h o r ' s p e r s o n a l c o p y 706 d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 705-713
Dental Materials, 2006
d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx-xxx a v a i l a b l e a t w w w . s c i e n c... more d e n t a l m a t e r i a l s x x x ( 2 0 0 6 ) xxx-xxx a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a a b s t r a c t
Dental Materials, 1995
Adhesion testing of dentin bonding agents was reviewed starting with the adhesion substrate, dent... more Adhesion testing of dentin bonding agents was reviewed starting with the adhesion substrate, dentin, the variables involved in etching, priming and bonding, storage variables and testing variables. Several recent reports attempting to standardize many of these variables were discussed. Recent advances in the development of new bonding systems have resulted in bond strengths on the order of 20-30 MPa. At these high bond strengths, most of the bond failure modes have been cohesive in dentin. As this precludes measurement of interfacial bond strength, new testing methods must be developed. One such new method, a microtensile method, was described along with preliminary results that have been obtained.
Dental Materials, 2003
Objectives. The aim of this study was to test the null hypothesis that the tensile properties of ... more Objectives. The aim of this study was to test the null hypothesis that the tensile properties of demineralized dentin are not influenced by the hydrogen bonding ability of anhydrous polar solvents.
Dental Materials, 1998
Objectives. Little research has been done to evaluate the effects of acids commonly used in adhes... more Objectives. Little research has been done to evaluate the effects of acids commonly used in adhesive dentistry, on the tensile properties of the demineralized dentin matrix. The purpose of this study was to evaluate the effects of a number of acidic conditioners on the ultimate tensile strength (UTS) and modulus of elasticity (E) of human coronal dentin matrix. Methods. Small hour-glass shaped (for UTS) or I-beam shaped (for determination of E) were prepared from mid-coronal dentin of extracted human third molars. After protecting the ends with varnish, the middle of the specimens was completely demineralized in 0.5 M EDTA (pH 7). UTS was determined by tensile stressing to failure. Modulus of elasticity was calculated from stress strain curves. The results were analyzed by ANOVA and Student-Neuman-Keuls test at the 95% confidence level. Results. Brief (ca. 1-2 min) exposure of demineralized dentin matrix to acids had no measurable effects on its tensile properties. Tenminute exposures to 2.5% and 17.5% nitric acid lowered (p Ͻ 0.05) the UTS compared to phosphate buffered saline (PBS)-exposed controls. Exposure of the decalcified dentin to 10% citric acid containing 3% ferric chloride, 10% citric acid, 37% phosphoric acid or 17.5% nitric acid containing 3% ferric chloride for 10 min had no effect on UTS. None of these acids consistently lowered stiffness. Significance. The results indicate that relatively long exposures to acids are required to alter the tensile properties of demineralized dentin. It is unlikely that the brief exposures to acids that are used in adhesive dentistry would acutely weaken the physical properties of demineralized dentin. However, long-term studies should be done to determine if such treatment increases the susceptibility of the matrix to hydrolysis. ᭧ 1998 Published by Elsevier Science Ltd on behalf of the Academy of Dental Materials 222 Zhang et al./Effects of acid on collagen strength
Journal of Dentistry, 2002
Objectives. This study tested the hypotheses that micro-tensile bond strengths of all currently a... more Objectives. This study tested the hypotheses that micro-tensile bond strengths of all currently available single-step adhesives to dentine are adversely affected by delayed activation of a light-cured composite, and that such a phenomenon only occurs in the presence of water from the substrate side of the bonded interface.
Biomaterials, 2005
As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high conce... more As acidic monomers of self-etching adhesives are incorporated into dental adhesives at high concentrations, the adhesive becomes more hydrophilic. Water sorption by polymers causes plasticization and lowers mechanical properties. The purpose of this study was to compare the water sorption and modulus of elasticity (E) of five experimental neat resins (EX) of increasing hydrophilicity, as ranked by their Hoy's solubility parameters and five commercial resins. Methods: After measuring the initial modulus of all resin disks by biaxial flexure, half the specimens were stored in hexadecane and the rest were stored in water. Repeated measurements of stiffness were made for 3 days. Water sorption and solubility measurements were made in a parallel experiment. Results: None of the specimens stored in oil showed any significant decrease in modulus. All resins stored in water exhibited a time-dependent decrease in modulus that was proportional to their degree of water sorption. Water sorption of EX was proportional to Hoy's solubility parameter for polar forces (d p ) with increasing polarity resulting in higher sorption. The least hydrophilic resin absorbed 0.55 wt% water and showed a 15% decrease in modulus after 3 days. The most hydrophilic experimental resin absorbed 12.8 wt% water and showed a 73% modulus decrease during the same period. The commercial resins absorbed between 5% and 12% water that was associated with a 19-42% reduction in modulus over 3 days. r
Dental Materials, 2005
Objectives: To evaluate the effects of long-term storage on the mechanical properties of the comp... more Objectives: To evaluate the effects of long-term storage on the mechanical properties of the components of resin -dentin bonds, that is, resin composite, adhesive system, demineralized and mineralized dentin.
Journal of Endodontics, 2006
This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin mo... more This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice pushout tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention. (J Endod 2006;32:537-540)
Biomaterials, 2005
This study examined the extent of organic solvent and water retention in comonomer blends with di... more This study examined the extent of organic solvent and water retention in comonomer blends with different hydrophilicity (Hoy's solubility parameter for hydrogen bonding, δ h ) after solvent evaporation, and the extent of tracer penetration in polymerised films prepared from these resins. For each comonomer blend, adhesive/solvent mixtures were prepared by addition of [1] 50wt% acetone; [2] 50wt% ethanol [3] 30wt% acetone and 20wt% water; and [4] 30wt% ethanol and 20wt% water. The mixtures were placed in glass wells and evaporated for 30-60 s for acetone-based resins, and 60-120 s for ethanol-based resins. The weight of the comonomer mixtures was measured before and after solvent evaporation. Resin films were prepared for transmission electron microscopy (TEM) after immersion in ammoniacal silver nitrate. The percentages of solvent and water retained in the comonomer mixtures, and between the acetone and ethanol groups were measured gravimetrically and were statistically compared. In comonomer-organic solvent mixtures, the percentage of solvent retained in acetone and ethanol-based mixtures significantly increased with hydrophilicity of the comonomer blends (P<0.05). In resin-organic solvent-water mixtures, significantly more solvent and water were retained in the ethanol-based mixtures (P<0.0001), when compared to acetone-based mixtures after 60 s air-drying. TEM revealed residual water being trapped as droplets in resin films containing acetone and water. Water-filled channels were seen along the film periphery of all groups and throughout the entire resin films containing ethanol and water. The addition of water to comonomer-ethanol mixtures results in increased retention of both ethanol and water because both solvents can hydrogen bond to the monomers.
Biomaterials, 2006
This study examined the effects of copolymer hydrophilicity and temperature on water sorption and... more This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter x 1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s total cohesive energy density (delta(t)), Hoy&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s solubility parameter for polar forces (delta(p)) and hydrogen bonding (delta(h)), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35-51 kJ/mol for copolymer blends R1-R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin-dentine bonds.
Dental Clinics of North America, 2002
In his classic thesis work on pulpal tissue reactions to restorative procedures and materials, La... more In his classic thesis work on pulpal tissue reactions to restorative procedures and materials, Langeland [1] drew a number of important conclusions. Among them was that ''dentin exposed by preparation of cavities or abutments should be covered immediately with a non-irritating material that does not permit leakage.'' That is, he recommended that dentin be sealed. At that time, there was no knowledge of smear layers or adhesion of materials to dentin. Most restorative materials in use then did not adapt perfectly to cavity walls and left gaps between the walls and the materials, permitting oral bacteria to colonize the gaps and to shed bacterial products to the pulp, where they could cause pulpal inflammation. Pulpal inflammation can be induced simply by leaving dentin cavities open to the oral environment . Brännströ m and Nyborg proposed that the presence of microorganisms in gaps between cavity walls and restorative materials was the major cause of pulpal inflammation after restorative treatment. Bergenholtz and Lindhe and Bergenholtz demonstrated that cell-free bacterial products could induce pulpal inflammation through freshly prepared dentin, Dent Clin N Am 46
European Journal of Oral Sciences, 2006
Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental ... more Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental adhesives are acidic (pH 1.5–2.7) and may activate dentin MMPs. The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic and collagenolytic activities in powdered mineralized dentin. Powdered dentin made from human teeth was mixed with all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the adhesives using acetone. Fresh untreated mineralized dentin powder had a gelatinolytic activity of 3.31 ± 0.39 relative fluorescent units (RFU) per mg dry weight (24 h) that increased, over storage time, to 87.5 RFU mg−1 (24 h) after 6–8 wk. When fresh powder was treated with acidic Tri-S Bond, the gelatinolytic activity increased from 3.24 ± 0.70 RFU mg−1 to > 112.5 RFU mg−1 (24 h) after 20 min and then remained unchanged. Monomers with lower pH values produced less activity. There was a significant, direct correlation between gelatinolytic activity and pH, with Tri-S giving the highest activity. Coating dentin powder with Tri-S resin prevented fluorescent substrates from gaining access to the enzyme, even though it activated the enzyme. In conclusion, self-etch adhesives may activate latent MMP and increase the activity to near-maximum levels and contribute to the degradation of resin–dentin bonds over time.
Journal of Dentistry, 2003
Objectives. To evaluate the microtensile bond strength of total-etch or selfetch adhesives to car... more Objectives. To evaluate the microtensile bond strength of total-etch or selfetch adhesives to caries-affected versus normal dentine, and to correlate these bond strengths with DIAGNOdent laser fluorescence and Knoop microhardness (KH) measurements of the substrates.
Biomaterials, 2005
This study provided morphological evidence that discrepancies between the depth of demineralisati... more This study provided morphological evidence that discrepancies between the depth of demineralisation and the depth of resin infiltration can occur in some mild self-etch adhesives. Sound dentine specimens derived from extracted human third molars were bonded with 5 one-step and 5 two-step self-etch adhesives. One millimeter thick slabs containing the resin-dentine interfaces were immersed in 50 wt% aqueous ammoniacal silver nitrate and processed for TEM examination. A zone of partially etched but uninfiltrated dentine was identified beneath the hybrid layers in the milder versions of both one-step and two-step self-etch adhesives. This zone was characterised by the occurrence of silver deposits along the interfibrillar spaces of mineralised collagen fibrils. The silver infiltrated interfibrillar spaces were clearly identified from the one-step self-etch adhesives Xeno III, iBond, Brush&Bond and the experimental adhesive, and were thinner and only occasionally observed in the two-step self-etch adhesives Clearfil SE Bond and Clearfil Protect Bond. The more aggressive one-step and two-step adhesives that exhibit more abrupt transitions from completely demineralised to mineralised dentin were devoid of these silver-infiltrated interfibrillar spaces beneath the hybrid layers. Incomplete resin infiltration observed in some self-etch adhesives may be caused by the reduced etching potential of the acidic monomers toward the base of hybrid layers, or the presence of acidic but non-polymerisable hydrolytic adhesive components, creating potential sites for the degradation of the bonded created by these self-etch adhesives. r