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PubMed2005

Single-bottle adhesives behave as permeable membranes after polymerisation. II. Differential permeability reduction with an oxalate desensitiser.

OBJECTIVES: This study examined the changes in hydraulic conductance and ultrastructure of dentine bonded with simplified etch-and-rinse adhesives to oxalate desensitiser pre-treated acid-etched dentine. METHODS: Human dentine disks were acid-etched, treated with an oxalate desensitiser (BisBlock, Bisco), and bonded with One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB) or Prime and Bond NT (PB). Similar disks from each group were acid-etched, and bonded without oxalate pre-treatment. Hydraulic conductance of the specimens was measured at 20 cm of water pressure and analysed with nonparametric statistical methods. Epoxy resin replicas of the smear layer-covered dentine and bonded dentine were examined with SEM for the extent of fluid transudation. Specimens bonded under perfusion were examined with TEM after tracer immersion. RESULTS: OB and PB exhibited a highly significant reversal of the reduced hydraulic conductance obtained with BisBlock on unbonded acid-etched dentine. Profuse water transudation across the bonded dentine was observed from the replicas. Adhesive interfaces were covered with spherical globules that interfered with dentine hybridization. Conversely, no significant difference in hydraulic conductance was observed in SB, between Bisblock pre-treated, unbonded and bonded acid-etched dentine. Significantly lower hydraulic conductance was shown on application of OS to Bisblock-treated acid-etched dentine. Water transudation was sparse, interfering surface globular structures were absent, and only angular subsurface crystals were seen in the dentinal tubules. CONCLUSIONS: Convective water fluxes through dentine may be reduced by applying Bisblock to acid-etched dentine before bonding with One-Step or Single Bond. However, reducing adhesive permeability with the use of oxalate desensitiser is not applicable to low acidity adhesives such as OptiBond Solo Plus and Prime and Bond NT.

Adhesives↗
PubMed2004

[Pain after cementation of cast restorations].

Some patients experience pain after cementation of a cast restoration on a vital tooth. Limited data are available on the prevalence of this pain. In many cases the pain disappears within two weeks. The major cause of the pain might be attributed to more permeability of the dentine after preparation. Consequently, bacteria have free access towards the pulp. With respect to the cement, it is more likely that microleakage after cementation will be the cause of pulpal problems than toxicity of the cement. In order to prevent pain, the use of a desensitizer (a primer or a bonding) can be considered. However, use of a desensitizer in combination with some cements, can reduce the retention of a cast restoration. More important than the use of a desensitizer seem precautions during the procedures of preparing the restoration, like using sufficient cooling water and preventing a tooth from dehydration.

Cementation↗
PubMed2004

Adhesive permeability affects coupling of resin cements that utilise self-etching primers to dentine.

OBJECTIVES: To examine the effects of an experimental bonding technique that reduces the permeability of the adhesive layer on the coupling of resin cements to dentine. METHODS: Extracted human third molars had their mid to deep dentin surface exposed flat by transversally sectioning the crowns. Resin composite overlays were constructed and cemented to the surfaces using either Panavia F (Kuraray) or Bistite II DC (Tokuyama) resin cements mediated by their respective one-step or two-step self-etch adhesives. Experimental groups were prepared in the same way, except that the additional layer of a low-viscosity bonding resin (LVBR, Scotchbond Multi-Purpose Plus, 3M ESPE) was placed on the bonded dentine surface before luting the overlays with the respective resin cements. The bonded assemblies were stored for 24 h in water at 37 degrees C and subsequently prepared for microtensile bond strength testing. Beams of approximately 0.8 mm(2) were tested in tension at 0.5 mm/min in a universal tester. Fractured surfaces were examined under scanning electron microscopy (SEM). Additional specimens were prepared and examined with TEM using a silver nitrate-staining technique. RESULTS: Two-way ANOVA showed significant interactions between materials and bonding protocols (p<0.05). When bonded according to manufacturer's directions, Panavia F produced bond strengths that were significantly lower than Bistite II DC (p<0.05). The placement of an additional layer of a LVBR improved significantly the bond strengths of Panavia F (p<0.05), but not of Bistite II DC (p>0.05). SEM observation of the fractured surfaces in Panavia F showed rosette-like features that were exclusive for specimens bonded according to manufacturer's directions. Such features corresponded well with the ultrastructure of the interfaces that showed more nanoleakage associated with the more permeable adhesive interface. The application of the additional layer of the LVBR reduced the amount of silver impregnation for both adhesives suggesting that reduced permeability of the adhesives resulted in improved coupling of the resin cements to dentin. CONCLUSIONS: Placement of an intermediate layer of a LVBR between the bonded dentine surface and the resin cements resulted in improved coupling of Panavia F to dentine.

Acid Etching, Dental↗
PubMed2004

An ultrastructural analysis of the prototype single-step adhesive applied on enamel and dentin surfaces.

A new type of self-etching agent, the single-step adhesive, was developed. The purpose of this study was to investigate the difference in the ultrastructural features of enamel and dentin surfaces following application of the prototype single-step adhesive (EXM618, 3M, MN, USA). Extracted caries-free human premolars were used in this study. Occlusal enamels of teeth--to be used as cut surface specimens--were removed perpendicular to the long axis of the specimens. The mesial and distal surfaces of these teeth, on the other hand, were used as uncut surface specimens in the test. In addition, Mega Bond (Kuraray Medical Inc., Tokyo, Japan) and Xeno CFII Bond (Dentsply Sankin, Tokyo, Japan) were used as controls. After covering half of the tooth surfaces with nail varnish (for control), the other half of each surface was treated with one of the three test adhesives--EXM618, Mega Bond, or Xeno CFII Bond--according to the manufacturer's recommendations. Conditioned enamel and dentin surfaces (i.e., decalcified depth and rugged surface) were observed with a scanning confocal laser microscope (SCLM 1100, Olympus, Tokyo, Japan; henceforth abbreviated as SCLM). Based on the findings of this study, the prototype single-step adhesive EXM618 appears to be suitable for use in dental clinics.

Acid Etching, Dental↗
PubMed1997

Changes in the permselectivity of human teeth during caries attack.

Previous studies have shown that enamel permselectivity can influence fluid composition within caries lesions during de- and remineralization. The permselectivity of human enamel, cementum, and dentin sections was examined, in a microwell model, by measurement of the membrane potential developed by KCl diffusion while the sections were immersed in solutions simulating resting (pH = 5.6) and cariogenic plaque fluid (pH = 4.8). In a second experiment, the effects of charged compounds (phytate and Zonyl-FSC) on the tooth permselectivity were examined. The average membrane potentials (+/- SD) in "resting plaque" solution were: sound enamel, 18.9 +/- 3.2 mV, n = 66; dentin, 0.9 +/- 9.2 mV, n = 59; and cementum, -0.8 +/- 8.2 mV, n = 42, with a positive sing indicating cation selectivity. The average membrane potentials became more negative in "cariogenic plaque" solution for all types of sections: sound enamel, 5.2 +/- 2.1 mV, n = 46; dentin, -8.1 +/- 7.4 mV, n = 45; and cementum, -14.3 +/- 8.0 mV, n = 34. In lesion enamel sections, the membrane potential was reduced from the non-lesion wells in both types of test solutions, while phytate treatment caused an increase of approximately 10 mV in potential (increased cation selectivity) in every enamel well in either "resting" or "cariogenic" solution. Treatment of enamel sections with Zonyl-FSC caused the membrane potential to become more negative in both test solutions, with many of the wells showing anion selectivity in the cariogenic "plaque-like" solution. However, the changes in enamel membrane potentials induced by Zonyl-FSC slowly increased toward the initial values after treatment, while the effects of the phytate pre-treatment persisted. Most dentin sections treated with phytate also showed an increase in potential after phytate treatment; however, Zonyl-FSC seemed to have little effect on the membrane potential of dentin. The results of this study suggest that modification of tooth permselectivity by surface-active agents may be a viable method of decreasing the rate of caries progression.

Dental Caries↗
PubMed1985

The effects of oxalate treatment on the smear layer of ground surfaces of human dentine.

The layer was evaluated by scanning electron microscopy and by measurement of hydraulic conductance before and after 2-min topical treatment with potassium chloride, neutral potassium oxalate, half-neutralized oxalic acid or both neutral and acidic oxalates. The treated smear layers were then re-evaluated microscopically and functionally both before and after acid challenge. The layers treated with KCl were not altered either microscopically or functionally and were susceptible to acid etching. Dentine surfaces treated with either oxalate solutions became less permeable and were acid-resistant.

Dentin↗
PubMed1994

Evaluation and treatment of bacterial microleakage.

Recent data have shown a correlation between pulp response and material biocompatibility when microleakage is prevented. Considering vital dentin, the dentist must keep in mind that it is an extension of the pulp, presenting the first line of response to the consequences of microleakage. Healing of the dental pulp is ensured when a clinical seal is provided to prevent bacterial microleakage. Microleakage is a biological phenomenon with several important clinical implications. The affective component clinically presents as dentin postoperative hypersensitivity due to the episodic hydrodynamic fluid movement within the tubule complex. The effective component is the disease process which signals the dentin and pulp complex to respond by deposition of sclerotic and reparative dentin deposition. Uncontrolled microleakage generally produces patient pain as well as to later allow bacterial infection resulting in recurrent caries and pulp inflammation. The dynamic, permeable nature of the dentin interface allows residual bacteria to proliferate following cavity preparation. Following sterile operative procedures, bacteria have been shown to percolate into the cavosurface margin resulting in recurrent caries and pulp inflammation. This report considers biological data emphasizing the clinical necessity to provide a hermetic seal to prepared dentin to prevent both dentin hypersensitivity and pulp inflammation.

Dental Leakage↗
PubMed2003

Have dentin adhesives become too hydrophilic?

This review discusses current trends in the development of dentin adhesives and the possibility that some classes of currently available adhesives are too hydrophilic. Manufacturers have reformulated dentin adhesives to make them more compatible for bonding to intrinsically moist, acid-etched dentin by adding 2-hydroxyethyl methacrylate and other hydrophilic resin monomers. These 3-step adhesives work well but are more time consuming to use and more sensitive to technique than the newer, simplified adhesives. When primers are mixed with adhesives in 2-step single-bottle adhesives and self-etching primers, the adhesives are more permeable to water and hence absorb more water over time than previous generations of adhesives. The most recent single-step self-etching adhesives are even more hydrophilic and hence more permeable to water derived from the underlying bonded dentin. This permeability can lead to a wide variety of seemingly unrelated problems, including incompatibility of chemically or dual-cured composites with simplified adhesives and expedited degradation of resin-dentin bonds.

Acid Etching, Dental↗
PubMed2004

Voids formation along the bonding interface between a smeared dentin surface and all-in-one adhesives.

It has been reported that the adhesive resin layer of all-in-one adhesives is permeable and allows the formation of a water channel or water tree. The effects of a smear layer on the ultra-structure of bonding interface created with three all-in-one adhesives and a resin composite were evaluated in this study. Dentin surface was ground with of 180-, 600-, or 2000-grit SiC paper to produce different smear layer thickness. The bonding interfaces were observed under a transmission electron microscope without demineralization. Voids of various sizes and water channels were found at the bottom of the adhesive resin layer along the bonding interface of SiC 180-grit dentin, while SiC 2000-grit dentin did not produce any voids. The results showed that the voids were possibly related to water that had penetrated from the underlying dentin. A smear layer may have an adverse influence on the bonding performance of all-in-one adhesives to dentin.

Adhesives↗
PubMed2003

Effect of dental adhesives on the exudative phase of the inflammatory process in subcutaneous tissue of rats.

The vascular changes in the subcutaneous connective tissue of rats induced by dentin bonding systems (one step) was studied and compared to those induced by saline solution (negative control) and Furacin (positive control), during the exudative phase of the inflammatory process. Twenty mg/kg of Evan's blue were injected intravenously in the vein of the rats' penises; 0.1 ml of each substance tested was inoculated in the subcutaneous tissue. After a 3 hour period the animals were sacrificed and their skins were excised and punched out with a standard steel 2.5 cm in diameter. The specimens were immediately immersed in 8 ml of formamide and taken to a double boiler for 72 hours at 37 C, to remove the dye. The liquid containing the overflowed dye was filtered, analyzed in the spectrophotometer (620 nm) and classified according to the criteria established by Nagem-Filho, Pereira (1976). After statistical analysis, the irritative potential of the substances was ranked as follows: Furacin (severe) > Single Bond and Bond 1 (moderate - no significant differences between the dentin bonding systems tested) > saline solution (not significant as regards the irritation degree).

Animals↗
PubMed2006

Diffusion-induced water movement within resin-dentin bonds during bonding.

It is thought that water-filled channels and nanovoids in resin-dentin bonds represent potential sites for degradation of bonds or hydrolysis of collagen or both. How water gains access to bonded interfaces is not clear. This study evaluated the diffusion-induced water uptake through resin-dentin interfaces during bonding. Two light-cured total-etch adhesive systems (Excite and One-Step Plus) and a chemical-cured adhesive (Amalgambond Plus) were used in this study. Dentin disks were placed in a split-chamber device, and the fluid movement across dentin was measured, with and without a physiological pressure, during bonding procedures and 24 h after bonding. For light-cured adhesives in the experimental groups, a 6 min interval of dark storage was conducted prior to light-curing, to evaluate the diffusion of water through the uncured resin monomers, and to test the effect of prolonged infiltration time of adhesives on water permeability of bonds. Prolonged adhesive infiltration reduced the water permeability of resin-dentin bonds for light-cured adhesives. Water gradients produced by bonding systems contribute to water movement across the dentin-adhesive interfaces during bonding procedures. Differences in chemical formulations for adhesive systems may lead to differences in the extent of diffusion-induced water movement and the amount of water within the resin-dentin bonds.

Dentin↗
PubMed2004

Improved wet bonding of methyl methacrylate-tri-n-butylborane resin to dentin etched with ten percent phosphoric acid in the presence of ferric ions.

The objective of this study was to determine the influence of dissolved dentinal substances in demineralized dentin on the hybridization of resin for bonding to dentin. It was hypothesized that these substances, including polyelectrolytes, significantly change the substrates, which could then be assessed by the addition of Na(+), Ca(2+), or Fe(3+) in 10% phosphoric acid. Bovine dentin specimens were etched for 10 s with a solution of 10% phosphoric acid (control) or of 22.0 mM dissolved sodium chloride (10P-Na), calcium chloride (10P-Ca), or ferric chloride (10P-Fe). The specimens were then rinsed, blot-dried, and primed three times with 5% 4-methacryloyloxyethyl trimellitate anhydride in acetone for 60 s. Methyl methacrylate-tri-n-butylborane resin was then applied. The tensile bond strength of each of the dumbbell-shaped specimens was then measured. The fractured surfaces and modified cross-sections were examined by scanning electron microscopy. The cross-sections were soaked in 6N HCl for 10 s and then in 1% sodium hypochlorite for 30 min to determine the resin content in the hybridized specimens. Shrinkage of the demineralized dentins upon drying was assessed by atomic force microscopy. The tensile bond strengths were 10.8 +/- 4.5 (control), 15.0 +/- 7.0 (10P-Na), 19.3 +/- 5.5 (10P-Ca), and 27.8 +/- 8.1 (10P-Fe) MPa. The atomic force microscopy studies showed that Fe(3+) minimized the shrinkage by drying for 10 s but Ca(2+) and Na(+) did not decrease the shrinkage the same as the control. The results support the hypothesis that the monomer permeability of wet demineralized dentin is effectively improved by dissolving ferric ions in the phosphoric acid, resulting in a greater bond strength and higher resin content in the hybridized dentin. The dissolved dentinal substances, including the polyelectrolytes, had a significant influence on the characteristics of the demineralized dentin, changing the degree of hybridization and bonding.

Animals↗
PubMed2005

Self-curing, self-etching adhesive cement systems.

PURPOSE: To investigate the influence of the acid-base reaction between acidic monomers and amines on the polymerization behavior of self-etching, self-curing adhesives, determine the effect of the application mode on the shear bond strength and morphology, and elucidate the adhesion performance of such systems by shear bond strength measurements. MATERIALS AND METHODS: The amine redox-initiator system N,N-di(2-hydroxyethyl)p-toluene (DEPT)/dibenzoyl peroxide (BPO) was selected to investigate the influence of the amine-base reaction on polymerization behavior. The PKa value of DEPT hydrochloride was measured by titration with NaOH. The influence of the pH value and DEPT concentration on the polymerization rate of methacrylates was investigated by exotherm time measurements. Three different application protocols of Multilink Primer (Ivoclar Vivadent) and Panavia 21 ED-Primer (Kuraray) were tested, 15 s passive vs 15 s agitation vs 60 s passive in combination with the corresponding resin luting material. The effects of these three application protocols were evaluated and monitored by both shear bond strength tests and SEM characterization of the surface morphology. The adhesion potential of these self-etching, self-curing luting systems was compared on enamel and dentin both directly after application and after 24 h. RESULTS: The pKa of DEPT-HCl is 4.45. The polymerization rate of the DEPT-containing, self-etching, self-curing adhesive system is highly influenced by both the amine concentration and the pH value. In the case of Multilink, agitation of the primer mixture for 15 s, especially on dentin, resulted in a higher bond strength and a more pronounced removal of the smear layer. Multilink resulted in statistically higher bond strengths (p < 0.05) than Panavia 21 for both the enamel and dentin directly after application and for the dentin after 24 h. CONCLUSION: Radical polymerization initiators used in self-curing systems are strongly adversely affected by acidic monomers incorporated in self-etching adhesives. However, if there is a good adjustment of these components and effects of adhesive application are taken in account, high bond strengths can be achieved.

Acid Etching, Dental↗
PubMed1999

A comparative study of fluoride uptake from dentin bonding agents and glass-ionomer cements in permanent and primary tooth enamel.

OBJECTIVE: Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount of fluoride release of these materials is still uncertain. The aim of this study was to determine the amount of fluoride uptake in primary and permanent tooth enamel from 1 conventional glass-ionomer cement (Fuji II), 1 resin-modified glass-ionomer cement (Fuji II LC), and 2 fluoride-releasing dentin bonding agents (Liner Bond 2 and Optibond) in vitro. METHOD AND MATERIALS: One hundred sixty caries-free primary and permanent molar teeth were assigned to the study. Materials were applied according to the manufacturer's instructions to standard windows created on the enamel surfaces. The amount of fluoride uptake by enamel was investigated by using a specific fluoride electrode and acid-etching biopsy technique. RESULTS: The amount of fluoride taken up from Fuji II and Fuji II LC by permanent and primary tooth enamel was found to be statistically significant. However, no significant fluoride uptake from Optibond and Liner Bond 2 was found. CONCLUSION: Fuji II and Fuji II LC glass-ionomer materials seemed to provide more effective fluoride release than did Optibond and Liner Bond 2 in permanent and primary enamel.

Analysis of Variance↗
PubMed2002

How can nanoleakage occur in self-etching adhesive systems that demineralize and infiltrate simultaneously?

PURPOSE: Single-step adhesives which etch and prime simultaneously and are not rinsed should not exhibit areas of incomplete infiltration within hybrid layers produced in sound dentin. This study examined the extent of silver uptake using ammoniacal silver nitrate in three two-step, self-etching primers (Imperva Fluoro Bond, Shofu; UniFil Bond, GC, ABF system, Kuraray) and one single-step, self-etching adhesive (AQ Bond, Sun Medical) bonded to dentin and four poly(HEMA) resins used as controls. MATERIALS AND METHODS: Flat dentin surfaces were bonded with these adhesives and sectioned into 0.8-mm-thick slabs that were then coated with nail varnish except for the bonded interfaces and immersed in AgNO3 for 24 h. Four types of poly(HEMA) resins were made: 100% HEMA; 90% HEMA-10% water; 75% HEMA-10% water, all polymerized with TBBO at 50 degrees C for 6 h; 100% HEMA polymerized at 25 degrees C for 30 min. After developing, undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. RESULTS: Nanoleakage patterns were observed in all bonded specimens. Fine segregated silver particles and reticular silver-staining patterns were found within the thin hybrid layers created by the three self-etching primers. For the single-step, self-etching adhesive, heavy silver deposits were identified within the hybridized complex formed by this adhesive within the smear layer, the underlying intact dentin, and in the adhesive layer. Increasing amounts of silver uptake were observed in poly(HEMA) specimens containing more water or that were polymerized at 25 degrees C for a short time instead of 50 degrees C for 6 h. CONCLUSIONS: Silver uptake in hybrid layers formed by self-etching adhesives in sound dentin is not necessarily caused by disparities between the depths of demineralization and resin infiltration. They represent areas of increased permeability within a polymerized resin matrix in which water is incompletely removed resulting in regions of incomplete polymerization and/or hydrogel formation.

Acid Etching, Dental↗