Analysis of chemical interaction of 4-MET with hydroxyapatite using XPS

Each dental adhesive contains a specific functional monomer that determines its actual adhesive performance to tooth tissue. 4-methacryloxyethyl trimellitic acid (4-MET) is well-known as one of the functional monomers mostly available and consequently widely used in commercial adhesives. We therefore characterized the chemical interaction of 4-MET with hydroxyapatite (HAp) using X-ray Photoelectron Spectroscopy (XPS). XPS revealed that the peak representing -COO- of 4-MET shifted to a lower binding energy, when 4-MET was adsorbed onto HAp. Deconvolution of this shifted peak disclosed two components with a peak representing unreacted carboxyl groups and ester groups, and a peak suggesting chemical bonding of other carboxyl groups to Ca of HAp. XPS spectra of HAp treated with 4-MET also disclosed the surface to be enriched in calcium and decreased in phosphorus, indicating that phosphorus was extracted at a relatively higher rate than calcium. It can thus be concluded that true chemical bonding of 4-MET with calcium present in HAp occurred, as it was proven using XPS.     

Gel phase formation at resin-modified glass-ionomer/tooth interfaces

Ionic bonding between polyalkenoic acid and hydroxyapatite may explain the excellent bonding retention of glass-ionomers in clinical trials. We have here investigated the extent to which the self-adhesiveness of resin-modified glass-ionomers (RMGIs) can be attributed to this chemical bonding capacity. Therefore, the interaction of 3 RMGIs with tooth substrates was comprehensively characterized, with electron and atomic force microscopy correlated with x-ray photoelectron spectroscopy (XPS). Interfacial ultrastructural analysis for 2 RMGIs disclosed a shallow hybridization of hydroxyapatite-coated collagen, on which a submicron gel phase was deposited through reaction of the polyalkenoic acid with calcium extracted from the dentin surface. One RMGI, however, bonded to dentin without hybrid layer or gel phase formation. XPS indicated that polycarboxylic acids included in the RMGIs electrostatically interacted with hydroxyapatite. We conclude that the self-adhesiveness of RMGIs should be attributed to ionic bonding to hydroxyapatite around collagen, and to micro-mechanical interlocking for those RMGIs that additionally hybridize dentin.     

Four-year water degradation of a resin-modified glass-ionomer adhesive bonded to dentin

Glass-ionomers are auto-adhesive to tooth tissue through combined micro-mechanical and chemical bonding. How much each of the two bonding components contributes to the actual bonding effectiveness is, however, not known and there is not much information available on long-term stability. The objective of this study was to assess the bonding effectiveness of a resin-modified glass-ionomer adhesive to dentin after 4 yr of water storage. Fuji Bond LC (GC) was applied without (i) and with pretreatment using (ii) a polyalkenoic acid conditioner and (iii) a 37.5% phosphoric acid etchant. The etchant was used to exclude any chemical interaction with hydroxyapatite. The micro-tensile bond strength ( microTBS) to dentin decreased significantly over the 4 yr period in all three experimental groups. After 24 h and 4 yr, the lowest micro TBS was recorded when dentin was not pretreated. The highest micro TBS was obtained following polyalkenoic acid pretreatment, although this was not significantly different from specimens that were pretreated using phosphoric acid. Pretreating dentin with phosphoric acid intensified micromechanical interlocking at the expense of chemical bonding potential to hydroxyapatite. Nevertheless, correlating the micro TBS data with failure analysis through scanning electron microscopy and transmission electron microscopy indicated that combined micro-mechanical and chemical bonding involving pretreatment with the polyalkenoic acid conditioner yielded the most durable bond.     

Laser-Raman Spectroscopic study of the adhesive interface between 4-MET/MMA-TBB resin and hydroxyapatite or bovine enamel.

The possible chemical interaction between synthetic hydroxyapatite or bovine enamel and a functional monomer of 4-methacryloxyethyl trimellitic acid (4-MET) diluted in methyl methacrylate (MMA) was examined by measuring the Raman spectra. It was concluded that the carboxyl group of 4-MET reacted with the calcium in the substrate to form a salt that was detected by the Raman band at around 1,380 cm-1. However, formation of the salt on the surface of the hydroxyapatite (HAP) with the carboxyl group, and polymerization of the 4-MET in the methacryl group near the surface were mutually exclusive reactions for the same 4-MET molecule.     

Evidence of chemisorption of maleic acid to enamel and hydroxyapatite

Maleic acid has been used as an etchant or non-rinse conditioner in adhesive dentistry. However, the inherent mechanisms of the interaction of maleic acid with hydroxyapatite/enamel have never been fully elucidated. The purpose of this study was to provide evidence for the chemisorption of maleic acid onto hydroxyapatite/enamel, and to identify the reaction products obtained following the interaction of maleic acid with hydroxyapatite. Hydroxyapatite particles were dissolved in a 15% (w/v) aqueous solution of maleic acid (pH = 0.98). Half of the solution was dried to obtain a desiccated mixture. This mixture, hydroxyapatite, maleic acid and self-prepared calcium maleate were analysed by X-ray diffraction (XRD). Acetone was added to the other half of the solution to obtain a precipitate. This precipitate, hydroxyapatite, maleic acid, unetched enamel and maleic acid-etched enamel were analysed by X-ray photoelectron spectroscopy (XPS). The precipitate was also analysed by (1)H NMR. A new binding energy, indicating carboxylate groups, was detected by XPS on the precipitate and maleic acid-etched enamel surface. XRD data indicated the formation of calcium maleate and calcium hydrogen phosphate after the reaction. NMR data revealed that one carboxylic group of maleic acid reacted with hydroxyapatite. Hence, maleic acid can chemisorb to hydroxyapatite and enamel via ionic interactions.     

苹果酸对羟基磷灰石脱钙和化学吸附的研究

目的　研究苹果酸对牙体硬组织的酸蚀作用及其对羟基磷灰石 (HA)的化学吸附作用。方法　 (1) 15 %苹果酸水溶液 10 78ml和 4 0 0 0mgHA混合 ,4 8h后分离固体生成物和滤液并反复冲洗固体 ,真空干燥 ,用傅里叶变换红外光谱法 (FTIR)进行定性和差错分析。 (2 )用 15 %苹果酸溶液酸蚀牙齿硬组织 15、30、6 0、12 0s后 ,干燥、喷金 ,扫描电镜观察表面形态。结果　苹果酸与HA反应后生成苹果酸钙盐有两种结构 ,一种溶解性较大 ,对HA有脱钙作用 ;另一种可溶性较小 ,可化学吸附于HA表面。延长酸蚀时间易生成沉积物阻塞牙本质小管。结论　苹果酸对HA具有脱钙 -吸附作用 ,延长酸蚀时间可生成阻塞牙本质小管的沉积物。     

Effect of conditioner on bond strength of glass-ionomer adhesive to dentin/enamel with and without smear layer interposition

The effect of a polyalkenoic acid conditioner pretreatment on the bond strength of a glass-ionomer adhesive to tooth substrates with or without smear layer was evaluated. Smear-layer covered and smear-layer free dentin and enamel surfaces were prepared from 24 extracted human molars. Resin composite was bonded to the surfaces using FujiBond LC with or without a polyalkenoic acid conditioner and subjected to microtensile bond strength (microTBS) testing. Failure modes were determined using scanning electron microscopy. For dentin, smear-layer coverage and conditioner treatment did not reveal significant differences in microTBS, which ranged from 20 to 29 MPa. For enamel, smear-layer coverage did not significantly affect microTBS, whereas, the use of conditioner significantly improved microTBS, reaching the same microTBS-values as when bonded to dentin. Regarding failure mode, most dentin specimens failed mixed adhesive cohesively. For enamel, adhesive failures mostly occurred when no conditioner was used, though mixed failures were predominant when the specimens were conditioned beforehand. Bonding of the glass ionomer adhesive to dentin can be achieved without the separate use of a polyalkenoic acid conditioner, even with the interposition of a smear layer. However, instrumented and non-instrumented enamel requires separate conditioning to provide sufficient micro-mechanical retention.     

Localized fluoride release from fluorine-carrying polyphosphonates.

Fluoride release from fluorine-carrying copolymers of vinylphosphonate induced by calcium apatite and tooth enamel has been investigated. Fluoride ions were determined potentiometrically in the study of calcium hydroxyapatite, and Auger spectroscopy was used to study the fluoride release to enamel. The adsorbed copolymer of vinylphosphonic acid and vinylphosphonyl thiofluoride was shown to release fluoride to calcium hydroxyapatite and to enamel. The oxygen analog has shown a similar behavior with calcium hydroxyapatite, but not with tooth enamel. The results suggest a potential application of such copolymers as caries preventive agents which combine the effects of polyphosphonates and of fluoride ions.     

Bond strength of a fluoride-releasing bracket adhesive Experimental study

The aim of the study was to examine a new fluoridereleasing light-cured filling composite for its bonding and debonding qualities when used as a bracket adhesive. The material investigated was a hybrid composite containing a chemically modified fluoride apatite, which is claimed to provide the enamel with phosphate, calcium, and fluoride ions in the presence of an acid pH, recharging its resources of these ions through fluoride-containing toothpastes used in daily oral hygiene.Concurrently suitability as an enamel conditioner was tested in a new self-etching primer, which does not require water rinsing but is gently air dried instead. For comparison a conventional light-cure single-component adhesive was used together with 37% orthophosphoric acid. After application of the respective conditioners, mesh-backed metal brackets were bonded to 20 human premolars in each of the 2 adhesive groups and subjected to a shear test. Bond failure location was evaluated using the Adhesive Remnant Index (ARI).     

Analysis of the enamel/adhesive resin interface with laser Raman microscopy

Adhesion of resin composites into enamel is currently believed to rely on infiltration of bonding resin into the porous zone, establishing micromechanical retention to etched enamel. This study investigated the change in chemical composition of the enamel/resin interface using a laser Raman microscopic system (System-2000, Renishaw). Two-step bonding systems, Mac Bond II (Tokuyama Corp), Clearfil Mega Bond and Single Bond (3M/ESPE) were employed. Resin composites were bonded to bovine enamel with bonding systems and sectioned through the bonded interface. The sectioned surfaces were then polished with diamond pastes down to 1.0 microm particle size. Raman spectra were successively recorded along a line perpendicular to the enamel/ resin interface. The sample stage was moved in 0.2 microm increments on a computer-controlled X-Y precision table. Additional spectra from samples of enamel and cured bonding resins were recorded for reference. The relative amounts of the hydroxyapatite (960cm(-1), P-O), bonding agent (640cm(-1), aromatic ring) and alkyl group (1450cm(-1), C-H) in the enamel/resin bonding area were calculated. From Raman spectroscopy, a gradual decrease in hydroxyapatite was observed, and it was estimated to extend 2.2-2.6 microm for Mac Bond II, 1.2-1.6 pm for Clearfil Mega Bond and 5.2-5.6 microm for Single Bond. Furthermore, the enamel/resin interface represents a gradual transition of bonding agent from the resin to tooth side. Evidence of poor saturation of adhesive resin in etched enamel with Single Bond was detected. From the results of this study, non-uniform resin infiltration into etched enamel was detected and the degree of resin infiltration was found to be different among the bonding systems used.     

Evaluation of the bonding mechanism of an adhesive material to primary teeth

PURPOSE: The aim of this study was to evaluate with scanning electron microscopy (SEM) the bonding mechanism of the one-bottle adhesive Prime&Bond NT (Dentsply, PBNT) to enamel and dentin of deciduous teeth, following different methods of substrate treatment. METHODS: Eighteen extracted posterior deciduous teeth were randomly divided into 6 groups (N=3). The experimental groups differed for substrate and method of substrate conditioning prior to bonding with PBNT. Group 1: 36% phosphoric acid (PA)/PBNT on dentin; group 2: PA/PBNT on enamel; group 3: non-rinsing conditioner (NRC) (Dentsply)/PBNT on dentin; group 4: NRC/PBNT on enamel; group 5: PBNT on dentin without any previous conditioning; group 6: PBNT on enamel without any previous conditioning. On all the specimens, following the application of the adhesive solution, Dyract AP was layered on top and light-cured. The bonded specimens were processed for SEM observations. RESULTS: When used in combination with 36% phosphoric acid, PBNT was able to form a hybrid layer with resin tags on both enamel and dentin. Following conditioning with NRC, a thinner hybrid layer with shorter resin tags was developed on dentin; on enamel an etching pattern was still detectable. When only PBNT was applied without any previous conditioning, on dentin neither hybrid layer nor resin tags were visible; no sign of micromechanical bonding could be seen on the untreated enamel. CONCLUSIONS: The bonding mechanism of the one-bottle adhesive Prime&Bond NT on enamel and dentin of deciduous teeth is effective only following substrate conditioning with 36% phosphoric acid or NRC.     

Effects of a chlorhexidine varnish on shear bond strength in indirect bonding

The purpose of this study was to evaluate the effects of an antimicrobial varnish on the shear bond strength (SBS) of metallic orthodontic brackets bonded with an indirect bonding resin. For this purpose, 60 noncarious human premolars were divided into three equal groups. Group 1 was an indirect bonding control group and, after acid etching of the enamel, the brackets were indirectly bonded to the teeth with an indirect bonding resin. In group 2, before bonding, an antimicrobial varnish was painted on the etched enamel and indirect bonding was carried out as in group 1. In group 3, Transbond MIP primer and the antimicrobial varnish were thoroughly mixed in a 1:2 proportion, applied to the enamel surface, light cured for 20 seconds, and the brackets were direct bonded. A universal testing machine was used to determine the maximum load necessary to debond the brackets, the SBS values recorded, and the adhesive remnant index scores determined. Data were analyzed using analysis of variance (ANOVA), Tukey HSD, and chi-square tests. Results of ANOVA revealed statistically significant differences in the SBS among the various groups tested (P < .05). Indirect bonding of brackets with Sondhi Rapid Set after the application of the antimicrobial varnish showed significantly lower SBS when compared with both the group 2, indirect bonding control group, and the group 3, direct bonded-antimicrobial varnish group.     

Improved adhesion of acrylic restorative materials to dental enamel by precoating with monomers containing phosphonate groups.

The adhesion of acrylic composite restorative materials to etched dental enamel is increased by a factor of two or more when the enamel is coated with a thin layer of vinyl-benzyl phosponic acid (VBPA) prior to forming the enamel-restorative bond. The present results support the suggestion that the enhanced adhesion is attributable to bonding between calcium ions in the enamel surface and phosphonate groups in the VBPA.     

Effect of moist vs. dry bonding to normal vs. caries-affected dentin with Scotchbond Multi-Purpose Plus.

Recent research in dentin bonding demonstrated the superiority of moist bonding over dry bonding on normal dentin, but it is unclear if this technique is also superior in bonding to caries-affected dentin. The purpose of this study was to evaluate the SEM appearance and bond strength of Scotchbond Multi-Purpose Plus (SMPP) to normal vs. caries-affected dentin bonded under moist vs. dry conditions, with and without polyalkenoic acid in the primer. Extracted carious human third molars were ground down by means of 600-grit SiC paper until the carious dentin no longer stained with caries detector solution. The flat surfaces were then primed, bonded, and built up with resin composite. After soaking in water for 1 day, the teeth were serially sectioned vertically into 5 or 6 slabs 0.7 mm thick. The bonded caries-affected areas were isolated by means of an ultrafine diamond bur to create an hourglass configuration with a cross-sectional area of 0.9 mm2. Bonded normal dentin was isolated the same way. Each specimen was attached to a Bencor device and tested in tension to failure. SMPP bonds to dry, normal dentin were only half as strong (21+/-10 MPa, x +/- SD) as those made to moist, normal dentin (42+/-9 MPa, p<0.01). There was no significant difference between bonds made to normal vs. caries-affected dentin by means of the moist technique (42+/-9 vs. 48+/-4 MPa, respectively). Removal of the polyalkenoic acid from the primer lowered (p<0.05) the bond strength of SMPP to caries-affected dentin (38+/-8 MPa). The benefits of moist bonding extend to caries-affected dentin. The polyalkenoic acid in the SMPP primer contributes to the high bond strength that can be achieved to caries-affected dentin.     

Effect of conditioning and 1 year aging on the bond strength and interfacial morphology of glass-ionomer cement bonded to dentin

ObjectiveThe purpose of this study was to determine the bond stability and the change in interfacial ultra-structure of a conventional glass-ionomer cement bonded to dentin, with and without pre-treatment using a polyalkenoic acid conditioner.MethodsThe occlusal dentin surfaces of six teeth were ground flat. Glass-ionomer cement was bonded to the surfaces either with or without polyalkenoic acid conditioning. The teeth were sectioned into 1-mm² stick-shaped specimens. The specimens obtained were randomly assigned to two groups with different periods of storage in water: 1 week and 1 year. The micro-tensile bond strength (μTBS) was determined for each storage time. Additional specimens were prepared for Transmission Electron Microscopy (TEM); they were produced with or without prior polyalkenoic acid conditioning in the same way as in the μTBS test.ResultsThere was no significant difference in μTBS to conditioned dentin and non-conditioned dentin (p > 0.05). The failures appeared to be of a mixed nature, although aging caused more areas of cohesive than adhesive failure in both groups. The TEM observation showed an intermediate layer, a matrix-rich layer and a partially demineralized layer in the polyalkenoic acid conditioned group.SignificanceAging did not reduce the bond strength of the conventional glass-ionomer cement to dentin with or without the use of a polyalkenoic acid conditioner.     

Bonding effectiveness and interfacial characterization of a nano-filled resin-modified glass-ionomer

Glass-ionomers (GIs) exhibit excellent clinical bonding effectiveness, but still have shortcomings such as polishability and general aesthetics. The aims of this study were (1) to determine the micro-tensile bond strength (μTBS) to enamel and dentin of a nano-filled resin-modified GI (nano-RMGI; Ketac N100, 3M-ESPE), and (2) to characterize its interfacial interaction with enamel and dentin using transmission electron microscopy (TEM).MethodsThe nano-RMGI was used both with and without its primer, while a conventional RMGI restorative material (conv-RMGI; Fuji II LC, GC) and a packable conventional GI cement (conv-GI; Fuji IX GP, GC) were used as controls. After bonding to freshly extracted human third molars, microspecimens of the interfaces were machined into a cylindrical hourglass shape and tested to failure in tension. Non-demineralized TEM sections were prepared and examined from additional teeth.ResultsThe μTBS to both enamel and dentin of nano-RMGI and conv-GI were not statistically different; the μTBS of non-primed nano-RMGI was significantly lower, while that of conv-RMGI was significantly higher than that of all other groups. TEM of nano-RMGI disclosed a tight interface at enamel and dentin without surface demineralization and hybrid-layer formation. A thin filler-free zone (<1 μm) was formed at dentin. A high filler loading and effective filler distribution were also evident, with localized areas exhibiting nano-filler clustering.ConclusionsThe nano-RMGI bonded as effectively to enamel and dentin as conv-GI, but bonded less effectively than conv-RMGI. Its bonding mechanism should be attributed to micro-mechanical interlocking provided by the surface roughness, most likely combined with chemical interaction through its acrylic/itaconic acid copolymers.     

Dentin conditioned with a metal salt-based conditioner

ObjectivesUniversal adhesives (UAs) can optionally be applied in either an etch-and-rinse (E&R) or self-etch (SE) bonding mode. As the preferred bonding mode differs for enamel versus dentin, a universal conditioner for both enamel and dentin in replacement of the relatively aggressive phosphoric-acid etchant remains desirable. This study aimed to test if a metal salt-based etchant (ZrO(NO₃)₂) provides as durable bonding to dentin as a classic E&R or SE bonding modeMethodsBefore applying the UA Adhese Universal (‘AdU’; Ivoclar Vivadent) to bur-cut dentin of 24 teeth (n = 8), dentin was conditioned with either (1) an experimental metal salt-based conditioner (‘ZON’; Ivoclar Vivadent) or (2) 37% phosphoric acid (Total Etch gel, Ivoclar Vivadent), representing a classic ‘E&R′ mode; (3) a third experimental group involved AdU applied in SE mode. Bonding effectiveness was determined in terms of immediate (‘1w’) and aged (‘50k’ TC) micro-tensile bond strength (μTBS) to bur-cut dentin. Adhesive-conditioned dentin interfacial interactions were characterized by S/TEM.ResultsLinear mixed-effects modeling revealed significantly higher immediate μTBS to dentin of ZON_AdU than E&R_AdU, while ZON_AdU performed not significantly different from SE_AdU. No significant differences were found between the three experimental groups after 50k TC (aged μTBS). S/TEM disclosed less exposure of dentinal collagen fibrils when AdU was bonded upon ZON etching than when applied in E&R mode. Moreover, ZON resulted in more hydroxyapatite (HAp) crystals remaining at the bottom of the hybrid layer, while dentinal tubule orifices remained nearly fully closed, by which hardly any resin tags were formed.SignificanceThe alternative metal salt-based conditioner revealed at dentin a more HAp-protected hybrid layer with less exposure of collagen fibrils, while a comparable bond strength was obtained to that with a phosphoric-acid E&R as well as with an SE (no conditioner) bonding mode. These findings confirm that the metal salt-based conditioner can be considered as a suitable alternative (enamel/)dentin conditioner to classic phosphoric acid employed in an E&R bonding mode.     

Bond strength of a fluoride-releasing bracket adhesive

The aim of the study was to examine a new fluoridereleasing light-cured filling composite for its bonding and debonding qualities when used as a bracket adhesive. The material investigated was a hybrid composite containing a chemically modified fluoride apatite, which is claimed to provide the enamel with phosphate, calcium, and fluoride ions in the presence of an acid pH, recharging its resources of these ions through fluoride-containing toothpastes used in daily oral hygiene.Concurrently suitability as an enamel conditioner was tested in a new self-etching primer, which does not require water rinsing but is gently air dried instead. For comparison a conventional light-cure single-component adhesive was used together with 37% orthophosphoric acid. After application of the respective conditioners, mesh-backed metal brackets were bonded to 20 human premolars in each of the 2 adhesive groups and subjected to a shear test. Bond failure location was evaluated using the Adhesive Remnant Index (ARI).Average bond strength of the experimental bracket adhesive and the conventional etchant was 8.96 MPa. Conditioning with the self-etching primer led to a decrease of mean shear bond strength values to 6.55 MPa. Highest bond strength was determined in the control group (12.19 MPa).The bond strength results obtained in the shear test recommend the new material as a bracket adhesive to be used with orthophosphoric acid for etching.     

Direct bonding comparing a polyacrylic acid and a phosphoric acid technique

The purpose of this study was to compare in vitro a polyacrylic acid technique (crystal bonding) with a conventional phosphoric acid-etch technique for the preparation of teeth for bonding. The potential value of the polyacrylic acid technique was evaluated for bond strength, enamel loss, cleanup, and fracture location--with and without the use of a sealant. Ninety-six premolars were evenly divided into two groups. Group A was preconditioned with polyacrylic acid and group B with phosphoric acid. Half of each group was treated with a sealant before direct bonding of orthodontic brackets. Sealant was not used on the other half of each group and brackets were bonded directly to the conditioned labial surfaces with a composite cement. Bonding and rebonding shear strength tests were carried out for both groups. Results indicated that shear bond strength values for the polyacrylic acid group were approximately one third those of the phosphoric acid group using a composite cement as the adhesive. Enamel loss was measured on the lingual surfaces of 30 of the 96 premolars. The lingual surfaces were conditioned with polyacrylic acid. Following debonding and cleanup procedures, the polyacrylic acid treated surface was left slightly pitted with no resin tags remaining. Cleanup procedures required only a rubber-cup silicate prophylaxis. The total enamel loss was minimal (4.5 micron), thus preserving most of the outermost fluoride-rich layer of enamel.     

氢氟酸蚀刻对Vita烤瓷贴面粘结抗剪强度的影响

目的　研究氢氟酸蚀刻对 Ｖｉｔａ 烤瓷贴面粘结抗剪强度的影响。方法　选择 ３０ 个氢氟酸（ Ｈ Ｆ）蚀刻瓷贴面的浓度—时间搭配点,模拟临床实际情况,作整体粘结抗剪强度测试和体视显微镜观察。结果　 Ｈ Ｆ酸各浓度—时间点蚀刻烤瓷后的剪切强度值均比对照组高。 Ｈ Ｆ酸浓度—时间的最佳搭配点为：２．５％ ５ｍ ｉｎ,５．０％ ２．５ｍ ｉｎ,７．５％ ,１５％ ５ｍ ｉｎ,１０％ ３０ｓ。烤瓷—树脂—牙釉质间的粘结破坏形式以混合破坏为主。结论　蚀刻可增加烤瓷与牙釉质间的粘结抗剪强度。