Membrane permeability properties of dental adhesive films

This study evaluated the permeability properties of five experimental resin membranes that ranged from relatively hydrophobic to relatively hydrophilic to seal acid-etched dentin saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents or as solutions solvated with ethanol (70% resin/30% ethanol). The quality of dentin sealing by these experimental resins was expressed in terms of reflection coefficients calculated as the ratio of the effective osmotic pressure to the theoretical osmotic pressure of test solutions. The effective osmotic pressure produced across resin-bonded dentin was induced in hypertonic solutions (CaCl(2) or albumin) at zero hydrostatic pressure. The outward fluid flow induced by these solutions was brought to zero by applying an opposing negative hydrostatic pressure. The least hydrophilic resins blends, R1 and R2, exhibited significantly (p < 0.05) higher reflection coefficients than the most hydrophilic resins (R4 and R5) in both conditions of dentin saturation (water and ethanol). The reflection coefficients of neat resins were, in general, significantly higher when compared with their corresponding solvated versions in both conditions of dentin saturation. In dentin saturated with ethanol, bonding with neat or solvated resins, resulted in reflection coefficients that were significantly higher when compared with the results obtained in dentin saturated with water. Reflection coefficients of CaCl(2) (ca. 1 x 10(-4)) were significantly lower (p < 0.05) than for albumin (ca. 3 x 10(-2)). Application of hydrophobic resins may provide better sealing of acid-etched dentin if the substrate is saturated with ethanol, instead of water.     

Surface properties of mussel adhesive protein component films.

Mussel adhesive protein (MAP) is the adhesive agent used by the blue sea mussel (Mytilus edulis) to attach the animal to various underwater surfaces. It is composed of 75-->85 repeating decameric units with the reported primary sequence NH2-A(1)-K(2)-P(3)-S(4)-Y(5)-Hyp(6)-Hyp(7)-T(8)-DOPA(9)-K(10)-COOH. This study identifies and compares the surface properties of the decameric unit, selected fragments and individual amino acid constituents with the complete MAP preparation. These molecular systems were examined: (a) in the solid state as thin films formed on germanium substrata using multiple-attenuated-internal-reflectance infrared (MAIR-IR) spectroscopy, ellipsometry and contact angle analysis; and (b) in the solution state using circular dichroism (CD) spectroscopy. Extensive molecular modelling of the decamer was performed making integral use of the experimentally derived data. These cumulative semi-empirical and empirical results suggest a conformation for the decamer that closely associates the L-DOPA and tyrosine residues with the solid substratum. This model provides the first representation of MAP derived from a rational integration of theoretical and experimental data. On the basis of this model, a possible explanation for the bioadhesive properties of MAP is suggested.     

Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins

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's total cohesive energy density (delta(t)), Hoy'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'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.     

Immunohistochemical study of dental pulp applied with 4-META/MMA-TBB adhesive resin after pulpotomy

The purpose of this study was to investigate nerve regeneration and proliferative activity in amputated pulp tissue after the application of 4-META/MMA-TBB adhesive resin (4-META resin). Calcium hydroxide was used as a control material. At 3 days, fibroblast-like cells were positive for proliferating cell nuclear antigen (PCNA) in both 4-META resin- and calcium hydroxide-treated groups and were located mainly within 0.5 mm from the cut surface. Only a few fragmented neurofilament protein (NFP)-positive nerve fibers were observed in this area. At 7 and 14 days, the number of PCNA-positive cells had gradually decreased and regenerated NFP-positive nerve fibers were observed close to the cut surface of the pulp in both groups. At 21 days in the experimental group, several PCNA-positive cells were still found in the area 0.5 mm from the cut surface, and NFP-positive nerve fibers were detected about 0.15-;0.2 mm from the cut surface. In contrast, a dentin bridge was produced under the necrotic layer at 21 days in the control group. PCNA-positive cells were not found underneath the dentin bridge, but NFP-positive nerve fibers had regenerated close to it. These results suggest that although cell differentiation and nerve regeneration are delayed, wound healing occurred even after the application of 4-META resin to exposed pulp surface the same as calcium hydroxide application.     

Development of adhesive pit and fissure sealants using a MMA resin initiated by a tri-n-butyl borane derivative

A new adhesive fissure sealant, which consists of a solution of 3% 2-hydroxy-3-beta-naphthoxypropyl methacrylate in methyl methacrylate (MMA), poly-MMA powder and an oxidized tri-n-butyl borane, a polymerization initiator, was developed. Tensile bond strength between an acid-etched bovine enamel and a poly-MMA bar joined by this sealant was 60 kg/cm2, and the value did not decrease much after 30 days immersion in water at 37 degrees C. Penetration of fuchsin into the sealant-enamel interface during a percolation test was not observed. SEM observation showed no voids between the enamel and the cured sealant.     

Recent advances in the theory and mechanism of adhesive resin bonding to dentin: a critical review

Dentin bonding issues involving adhesive resins have attracted considerable research interest in recent years. An important advance due to the ongoing research is the concept of hybridization of the tissue with primer/adhesive systems. Hybridization involves permeation of primer monomer into the tissue substrate. Although the mechanism of adhesive permeation and interaction with tissue may be complex, significant advances have been made. In systems where etching precedes priming and bonding steps, the Hoy's solubility parameter compatibility of the primer formulation with that of demineralized dentin matrix may determine adhesive permeability. Monomer permeation brings the primer atoms in closer contact with the substrate atoms, leading to adhesive interactions through van der Waals, hydrogen bonding, and electrostatic interactions. In self-etch primer systems, stronger electrostatic interaction between primer monomers and hydroxyapatite has been used to explain the adhesion process. These interactions have been computer-modeled and analyzed. Such interactions and subsequent polymerization of the monomer promote improved bond strength and efficient margin sealing. Incomplete permeation of monomer into the full depth of demineralized region may, however, leave exposed collagen fibrils and cause nanoleakage of water into these regions through a 20-100 nm sized marginal gap, leading to subsequent hydrolytic degradation of these collagen fibrils and the hybrid layer. Microleakage is also a problem in some single step formulations. In this review, we analyze these current theoretical and mechanism-related issues of interest in adhesive resin bonding to dentin, and outline the continuing problems that need to be overcome in the future.     

Onium salt reduces the inhibitory polymerization effect from an organic solvent in a model dental adhesive resin

This study evaluated the effect of organic solvent concentration on the polymerization kinetics for a model dental adhesive resin containing a ternary photoinitiator system. A monomer blend based on the bis-GMA, TEGDMA, and HEMA was used as a model dental adhesive resin, which was polymerized using a binary system [camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system [CQ, EDAB, and diphenyliodonium hexafluorphosphate (DPIHFP)]. Additionally, these blends had 0, 10, 20, 30, and 40 wt % ethanol added. Real-time Fourier transform infrared spectroscopy was used to investigate the polymerization reaction over photoactivation time. Data were plotted, and Hill's three-parameter nonlinear regression was performed for curve fitting. The addition of a solvent to the monomer blends decreased the polymerization kinetics, directly affecting the rate of polymerization, delaying vitrification, and attenuating the Trommsdorf effect. The introduction of DPIHFP displayed a strong increase in reaction kinetics, reducing the solvent inhibition effect. After 10 s of photoactivation, the binary system obtained in 0, 10, 20, 30, and 40% of ethanol, a degree of conversion of 44.6, 26.3, 13.4, 1.15, and 0.0%, respectively, whereas when a ternary system was used, the values were 54.6, 40.5, 27.4, 14.5, and 3.4%. An improvement was observed in the polymerization kinetics of a model dental adhesive resin when using a ternary photoinitiation system, making the material less sensitive to the residual presence of a solvent before photoactivation.     

Apparent conversion of adhesive resin in the hybrid layer, Part II: In situ studies of the resin-dentin bond

Penetration and conversion of adhesives into the hybrid layer (HL) is important to the quality and longevity of the adhesive resin (AR)-dentin bond. In this study, a methodology is developed to examine the degree of conversion and relative HEMA concentration with respect to Bis-GMA using Raman spectroscopy. This methodology will be used in the future reports related to this topic. Conversion in the AR of water-stored resin-dentin samples (84% +/- 3%) agreed well with that measured in commercial adhesive (Comm Adh) resin samples after 24-h water storage (80% +/- 2% from Part 1) and was significantly higher than Comm Adh without water storage (58% +/- 3% from Part 1) (p = 0.0005). Adhesive conversion was not significantly different (p = 0.5036) through the middle of the HL, with a mean of 83% +/- 6%. HEMA mole fraction, relative to Bis-GMA, was significantly higher (p = 0.0028) in the top half of the HL (0.67 +/- 0.03), when compared to HEMA in the AR (0.60 +/- 0.01). HEMA and EDMAB were identified through GC/MS as leachable components in the aqueous 24-h storage media. The effect of this elution explains the change in conversion measurements observed between dry and water-stored conditions, which is more appropriately described as the "apparent" conversion.     

Comparative biophysical study of adsorbed calf serum, fetal bovine serum and mussel adhesive protein films.

Varying concentrations of different sera and adhesive agents are routinely used to increase cellular attachment to substrata. The surface-chemical effects of some of these surface-altering materials have been examined using ellipsometry, contact angle analysis and multiple-attenuated internal reflection infrared (MAIR-IR) spectroscopy. Specifically, 15% fetal bovine serum (FBS), Ham's F-12 (containing 10% FBS + 1% penicillin/streptomycin), 10% calf serum and mussel adhesive protein (MAP) were allowed to adsorb on to similar and different surfaces and then compared. Each of these preparations is capable of altering the surface-chemical properties of substrata with varying resultant surface energies. It is therefore important to characterize serum in the proper concentrations on the substrata under consideration in order to understand the interfacial effects.     

Effect of light-cure time of adhesive resin on the thickness of the oxygen-inhibited layer and the microtensile bond strength to dentin

A thick oxygen-inhibited layer (OIL) on a cured adhesive layer (AL) is believed to result in both good adaptation of composite resin (CR) and high bond strength. A high degree of conversion (DC) of the AL is also needed for durable bonding. This study evaluated the hypothesis that increasing the DC by prolonging the light-curing time of adhesive bonding resin might decrease the bond strength of the adhesive to dentin because of the subsequent thinning of the OIL thickness. The OIL thickness and the DC of solvent-removed One Step and D/E bonding resin of All Bond 2 (Bisco, USA) were measured simultaneously with FT-NIR spectroscopy according to increasing light-cure times (10, 20, 30, and 60 s) so as to evaluate their effect on the microtensile bond strength. The bonded interfaces were evaluated using scanning electron microscopy. Excessive irradiation of light-curing adhesives increased the DC, but decreased the OIL thickness. When the OIL was significantly thin by curing the adhesives for 30 or 60 s, defects were observed at the interface between the AL and the CR, as well as at the interface between the AL and the hybrid layer. When the OIL was thick, free radicals from the overlying CR may have diffused into the unreacted monomer mixtures of the OIL, chemically connecting the cured AL and the newly curing composite. It was found that to obtain maximum dentin bond strength, light-curing adhesives should be cured for the irradiation time recommended by the manufacturer.     

Panavia F遮色树脂黏结剂对Cerinate瓷贴面修复不同染色程度模拟四环素牙遮色效果研究

背景：关于四环素牙的美学修复大多局限于临床上的观察,而基础的实验研究相对较少。 目的：观察Cerinate瓷贴面修复轻度(黄色)、中度(黑灰色)、重度(黄-灰色)、极重度(灰褐色)4种不同染色程度模拟四环素牙的颜色变化。 方法：将模拟四环素牙试件按轻、中、重、极重度4种不同染色程度分为4组,每组10个试件,用Cerinate瓷贴面进行修复,Panavia F遮色树脂黏结剂黏结,用电子测色仪测定修复体黏结前及黏结后的L*、a*、b*值及变化。 结果与结论：瓷贴面黏结前与黏结后的表面的L*、a*、b*值之间差异有显著性意义(P < 0.05)。轻度四环素牙选用未含有遮色剂的树脂黏结剂黏结会较小,中、重度四环素牙在用含有遮色剂的遮色树脂黏结剂黏结后对修复体的颜色遮色效果较好,而对极重度四环素牙遮色效果不好,最好选用其他修复体修复。     

Permeability of continuous capillaries

This review describes the theories of transport of solutes and solvent across the endothelial membrane of continuous capillaries which constitutes the microvascular exchange domain in peripheral tissues such as the heart, skeletal muscle, adipose tissue, and skin. The theories of equivalent endothelial pores and fiber matrix are considered together with discussions of the various methodological techniques for measurement of fluxes and flows, and the results and implications of anatomical and physiological examinations are considered.     

Permeability of amalgam restorative materials

The beneficial effect of fluoride-containing amalgam in preventing recurrent dental caries depends on the ability of the material to deliver fluoride (F). A two-chamber diffusion cell has been employed to monitor the diffusion of F in freshly prepared amalgam sections (membranes) as well as in amalgam sections stored in F solution for 15 d. The diffusion of ¹²⁵I was also monitored, as a reference. Five and ten successive measurements at 72 h intervals were made on the fresh and stored amalgam specimens, respectively. The average diffusion coefficient, D, of F and ¹²⁵I in fresh amalgam was 2.39 × 10⁻¹⁰ and 1.85 × 10⁻¹⁰ cm²/s, respectively. For stored amalgam, the average D of F during a 30 d experiment was 1.35 × 10⁻¹⁰ cm²/s. The average D of F in stored amalgam, during the first 15 d of the experiment, was 31 % less than in fresh amalgam (p < 0.01). A decline in the diffusion process was observed during the course of the experiments. During 15 d diffusion in fresh amalgam and 30 d diffusion in stored amalgam the cumulative diffused F were 0.79 and 0.88% of the F in the source. SEM findings revealed the deposition of corrosion products on amalgam stored for 3 months in 0.19% F solution.     

Effect of resin hydrophilicity and water storage on resin strength

This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125 degrees C for 10 min. After dry ageing for 24 h at 37 degrees C, the middle third of each resin specimen was trimmed into an 'I' shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p < 0.01) in UTS was observed in Groups II-V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p > 0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin-dentine bonds.     

Neurosurgical application of fibrin adhesive

We have tried fibrin adhesive, which mimics the end stage of plasmatic coagulation, in 26 patients with various neurosurgical problems such as: repair of cerebrospinal fluid (CSF) leaks, sealing of the vascular anastomosis sites, reinforcements of aneurysmal clippings, and hemostasis after resection of brain tumors. Presented in this report are 11 intracranial aneurysms, 11 brain tumors, 2 lipomyelo-meningoceles, and one each of cerebral arteriovenous malformation and torn dura resulting from a mastoidectomy. Procedures which seemed to be impossible or very difficult by conventional neurosurgical techniques could be accomplished in all cases without any complication. Our experience with fibrin adhesive suggests that it is a valuable adjuvant to various microneurosurgical procedures, and it may be potentially useful for protection of major cerebral veins and venous sinuses during cerebral retraction.