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PubMed2001

Protein characterisation of salivary and plasma biofilms formed in vitro on non-corroded and corroded dental ceramic materials.

Dental ceramics are generally regarded as low-adhesive materials. Different ceramics may, however, differ in composition and physico-chemical surface properties, which may be changed after corrosion. The aim of this study was to examine the adsorption of proteins onto specimens of different ceramic materials after the incubation in saliva and plasma before and after in vitro corrosion. In addition, the topography of the biofilm was examined by AFM. Surface-bound proteins were desorbed and analysed by polyacrylamide gel electrophoresis (PAGE) and immunoblotting using antibodies to saliva and plasma proteins. Silver-stained gels indicated differences in the adsorption of proteins. Differences in surface roughness at the nanometer level did not, however, seem to be correlated to the protein adsorption. After corrosion, unchanged or increased protein staining was generally seen in the gels and Western blots. The reactions for salivary amylase and proline-rich proteins varied between the different materials. Albumin and fibrinogen were identified in samples from all materials tested. Fibronectin and in specific IgA were more sparsely seen. No saliva but all plasma proteins were identified in the alumina and yttria-stabilised zirconia samples and reduced protein reactions were obtained after corrosion.

Adsorption↗
PubMed2006

Water sorption and solubility of dentin bonding agents light-cured with different light sources.

OBJECTIVE: The aim of this study was to compare water sorption (WS) and solubility (WSB) of different dentin bonding agents (DBA) as regards classification and light-activation system. The null hypotheses were: (1) there is no difference among DBA with respect to water sorption and solubility; (2) there is no effect of light-curing source on water sorption and solubility of DBA. METHODS: The tested materials were: three-step etch-and-rinse (ScotchBond multi-purpose and Heliobond-control groups), two-step etch-and-rinse (Excite, Adper Single Bond, Adper Single Bond 2), self-etching (Adhse) and all-in-one (Xeno III) systems. For each material, six specimens were prepared (0.8mmx5.5mm) for each light-activation device: halogen lamp (control) or light-emitting diodes (LED). They were transferred to desiccators until a constant mass was obtained (m(1)), subsequently immersed in deionized water until no alteration was obtained (m(2)). Following, the specimens were reconditioned to constant mass in desiccators (m(3)). The volume (V) of each specimen was calculated (mm(3)). WS and WSB were determined using the equations (m(2)-m(3)/V) and (m(3)-m(1)/V), respectively. Data were subjected to one-way analysis of variance and Tukey test (p<0.05). The influence of photo-activation units was analyzed by t-test. RESULTS: Higher values of WS and WSB were observed for the two-step etch-and-rinse and all-in-one systems. The employed light-activation unit also affected the tested characteristics. Thus, the anticipated null hypotheses were rejected. CONCLUSIONS: Simplified systems were more susceptible to water adverse and they may become more prone to degradation over time regardless of the type of light-activation source.

Absorption↗
PubMed1997

Effects of long-term storage on properties of an alginate impression material.

STATEMENT OF PROBLEM: Storage stability is a critical characteristic for perishable dental materials. PURPOSE: The purpose of this shelf-life study was to document changes in the properties of an alginate impression material on exposure to various environmental conditions for more than 78 months. MATERIAL AND METHODS: Properties measured included recovery from deformation, strain in compression, compressive strength, tear strength, working time, and creep compliance. RESULTS: Results revealed increases in strength and working time and a decrease in recovery from deformation at 30 to 50 months: strength and recovery then remained constant past 6 years, whereas working time and creep compliance decreased. Only the most stressful environmental conditions (heat and humidity) caused spontaneous failure of the material to set. CONCLUSIONS: We concluded that, under most storage conditions, properties of the alginate material tested remain within ADA specification limits well past manufacturer's designated shelf life. ADA specifications should require manufacturers to verify that the shelf life of each perishable material is based on valid data. An accelerated aging test was developed to simulate real time property changes and to assist in evaluating similar materials.

Alginates↗
PubMedDate not supplied

Automated method for determining Instron Residual Seal Force of glass vial/rubber closure systems. Part II. 13 mm vials.

Instron Residual Seal Force (IRSF) of 13 mm glass vial/rubber closure systems was determined using an Instron 4501 Materials Testing System and computerized data analysis. A series of three cap anvils varying in shape and dimensions were machined to optimize cap anvil performance. Cap anvils with spherical top surfaces and narrow internal dimensions produced uniform stress-deformation curves from which precise IRSF values were derived.

Drug Packaging↗
PubMed2006

Preliminary dosimetric characterisation of thermoluminescent materials for beta radiation monitoring at nuclear medicine services.

Beta emitters are widely used in nuclear medicine for diagnostic and therapeutic purposes. The critical groups exposed to a radioactive patient include the staff, other patients and members of the public accompanying the patient. The aim of this work is to characterise thermoluminescent (TL) materials for the staff monitoring of nuclear medicine services that manipulate beta radiation solutions of (153)Sm. This study was performed using CaSO(4):Dy + Teflon pellets, produced at IPEN, with different dimensions. For the dosimetric characterisation, these TL dosemeters were exposed to gamma source ((60)Co) and to beta sealed sources ((90)Sr + (90)Y, (204)Tl and (147)Pm) and to a non-sealed source ((153)Sm). Results were obtained related to reproducibility, lower detection limits, calibration curves, angle and energy dependence of response. All tested materials show usefulness for monitoring of workers exposed to beta radiation.

Beta Particles↗
PubMed1985

Solvent interactions with test compounds and recommendations for testing to avoid artifacts.

Reports in the literature describing artifactual results owing to interactions of test materials with solvents are becoming more frequent. The present study was initiated to examine possible interactions of 1,1,3-trichloro-, 1,1,3,3-tetrachloro-, pentachloro- and hexachloroacetones with different solvents, since certain solvent effects with the last compound have been shown previously. Quantitative differences in levels of mutagenic potency were found for tri-, tetra-, and pentachloroacetone, dissolved in acetone or dimethyl sulfoxide (DMSO). On the other hand, hexachloroacetone without solvent was mutagenic, and this activity was enhanced when it was dissolved in DMSO; in acetone it was not mutagenic. A time-dependent reaction of hexachloroacetone with DMSO was the only test material-solvent interaction found in this study. The results show clearly that DMSO is not an appropriate solvent for hexachloroacetone. On the basis of these and previous results, we recommend consideration of the following strategy to help prevent reporting of artifactual results owing to interaction with solvents: Results from initial screening experiments should be confirmed in repeat experiments using a different solvent; and a different solvent should be used in confirming the findings of other investigators. Differences in results would indicate a need for further study.

Acetone↗
PubMed1993

Release of fluoride and other elements from light-cured glass ionomers in neutral and acidic conditions.

The purpose of this study was to measure the release of fluoride, sodium, silicon, calcium, strontium, and aluminum from light-cured glass ionomers. The materials tested were: (1) Baseline VLC thick mix; (2) Baseline VLC thin mix; (3) Fuji Lining LC; (4) Vitrebond; and (5) XR-Ionomer. A conventional glass ionomer, Ketac-FilAplicap, and a silver-reinforced glass ionomer, Ketac-Silver, were used as controls. Each test specimen was first stored for 16 days in de-ionized water, followed by a further 16 days in 0.01 mol/L lactic acid (pH 4.0); both solutions were replaced at predetermined intervals. After that, the specimens were immersed for up to 122 days in de-ionized water. During the immersion, light-cured glass ionomers showed considerable variation in the release of fluoride and other elements. In lactic acid, all cements eluted the matrix-forming cations, aluminum and calcium or strontium. This suggests that light-cured materials are as equally susceptible to erosion as are chemically cured glass ionomers. During the immersion, some of the light-cured materials showed a considerable weight gain.

Absorption↗
PubMedDate not supplied

Bond strength of self-etching primers to enamel and dentin of primary teeth.

PURPOSE: The objective of this in vitro study was to evaluate the tensile bond strength of three self-etching primers to human primary enamel and dentin. METHODS: Forty (40) freshly extracted primary molars were sectioned bucco-lingually and embedded in self-curing acrylic resin with the facial or lingual surfaces exposed. The specimens were wet ground to 600 grit SiC paper to expose a flat enamel or dentin surface. The materials tested were: Prompt L-Pop (LP2, ESPE), Clearfil SE Bond (CSE, Kuraray America), Etch and Prime 3.0 (EP, Degussa) anda control, Prime and Bond NT (NT, Dentsply/Caulk). The adhesive systems were applied according to the manufacturers' instructions. An inverted, truncated cone of composite (Pertac II, ESPE) with a 2-mm bonding diameter was cured using a polytetrafluoroethylene jig. The specimens were debonded in tension using a universal testing machine (Instron) at a crosshead speed of 0.5 mm/min. RESULTS: Analysis of variance (ANOVA) showed significant differences existed between the four systems and two surfaces. To enamel of primary teeth, Prime and Bond NT had significantly higher bond strength (25.9 MPa) than when bonding with the three acidic primers Prompt L-Pop (18.5 MPa), Etch and Prime 3.0 (19.3 MPa) and Clearfil SE Bond (18.7 MPa). Complete bond failures occurred with Prompt L-Pop and Etch and Prime 3.0 to dentin of primary teeth. With a mean of 39 Mpa, the bond strength to dentin of primary teeth with Clearfil SE Bond was significantly higher than with Prime and Bond NT (12.5 MPa). CONCLUSIONS: The results of this in vitro study show that the four adhesive systems tested bonded effectively to enamel of primary teeth, but only CSE achieved adequate bond strengths to dentin of primary teeth.

Acid Etching, Dental↗
PubMed2000

Mechanical disruption of dentin collagen fibrils during resin-dentin bond testing.

PURPOSE: To determine if collagen fibrils on the dentin side of failed resin-dentin interfaces undergo mechanical disruption during microtensile bond testing. MATERIALS AND METHODS: Extracted, caries-free human third molars were divided into four groups. The occlusal enamel was removed, leaving a flat dentin surface for bonding. Resin composite buildups were made after the acid-conditioned dentin was bonded with either Single Bond (S) or One-Step (O), and using either moist bonding (M) or air drying for 5 s (D). After storage in water for 24 h, the teeth were vertically sectioned into an array of 0.9 x 0.9 mm resin composite-dentin beams. They were stressed to failure using the nontrimming version of the microtensile bond test. Fractured dentin and resin composite sides of representative beams from each group that exhibited adhesive failures under light microscopy examination were prepared for scanning (SEM) and transmission electron microscopy (TEM). RESULTS: A two-way ANOVA showed that moist bond strengths were significantly higher than those made to dry dentin (M > D; p < 0.001), but that there was no difference between the adhesives (S vs O; p = 0.547). SEM analysis showed the presence of loose collagen fibrils within fractured hybrid layers in the dry groups, but not in the moist groups. TEM examination of the dry-bonded groups revealed collagen fibrils that were thinner and exhibited abnormally wide interfibrillar spaces when hybrid layers were intact. Within dry-bonded fractured hybrid layers, broad mechanical disruption zones could be seen, consisting of fibrils that were devoid of cross banding, defibrillation of the subfibrillar architecture, and gross disaggregation into microfibrils. In the moist-bonded groups, only short mechanical disruption zones were found along the torn edges of the collagen fibrils. The rest of the fibrils beyond the fracture site were intact and retained their periodicity. Mechanical testing of demineralized matrices yielded a maximum modulus of elasticity of 43.9 +/- 6.1 MPa. CONCLUSION: We speculate that adhesive resin has a protective function for demineralized collagen in well-infiltrated hybrid layers. We propose that both the collagen and resin contribute to load sharing during stress application until the final moment of rupture. On the other hand, collagen fibrils in poorly infiltrated hybrid layers, being unsupported by resin, undergo various degrees of irreversible mechanical disruption depending on how the stress is dissipated. The collagen fibril network has a much lower modulus of elasticity compared to those of resin-infiltrated fibrils or the demineralized dentin.

Acid Etching, Dental↗
PubMed1996

Bonding strength of glass ionomers to dense synthetic hydroxyapatite and fluoroapatite ceramics.

The bonding strength of two glass ionomers, a resin-modified and a conventional one, to dense synthetic hydroxyapatite (HA) and fluoroapatite (FA) ceramics was compared by measuring the shear strength between the ionomers and the apatites. Before the glass ionomers were applied on the apatites, the surfaces of HA and FA plates were either fine-polished or acid-etched after fine polishing. Commercially pure titanium (CP Ti) plates were used as a control. The effects of polyacrylic acid (PAA) surface preconditioning on bonding strength were also studied. The results show that the ionomers bind to HA significantly more strongly than to FA in all cases. The resin-modified material showed a significantly higher shear strength to apatites than the conventional one. Acid etching increased the shear strength significantly for the conventional glass ionomer to both HA and FA, and 25% PAA preconditioning increased the shear strength significantly for the resin-modified glass ionomer to both HA and FA. It was concluded that glass ionomers seemed to bind to apatite chemically, and the bonding strength was influenced by the cohesive strength of the ionomers and the surface roughness of the apatites. The dense synthetic apatites seemed to be good test materials for bonding evaluations of glass ionomers to mineral tissue.

Acid Etching, Dental↗
PubMed2003

Human serum opsonization of orthopedic biomaterial particles: protein-binding and monocyte/macrophage activation in vitro.

Wear particles generated after total joint arthroplasty activate monocyte/macrophages and incite formation of a granulomatous periprosthetic tissue associated with bone loss and implant loosening. This study tested the hypothesis that selective opsonization of orthopedic implant biomaterial wear particles by human serum proteins influences monocyte/macrophage activation. Serum protein binding to metallic, polymeric, and ceramic particles was determined by one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Individual proteins bound to particles were subsequently identified using two-dimensional SDS-PAGE, microsequencing techniques, and SWISS-PROT analysis. Effects of selective protein opsonization on particle-induced monocyte/macrophage activation were assessed by quantification of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha release. Results from one-dimensional gel analyses revealed distinct serum protein-binding patterns specific for each material tested. Two-dimensional gel analysis together with amino acid sequencing of the prominent protein species confirmed the presence of albumin and alpha-1-antitrypsin bound to all particles tested. In contrast to the metallic particles, apolipoprotein was a major species associated with polymeric particles. Opsonization of PMMA particles with purified preparations of each of the identified proteins showed that albumin significantly enhanced particle-induced monocyte/macrophage activation. These data confirm orthopedic biomaterial specific binding of human serum proteins and demonstrate that albumin exacerbates particle-induced monocyte/macrophage activation. Alterations in the chemical and surface properties of orthopedic biomaterials to modulate protein interactions may improve implant longevity.

Biocompatible Materials↗
PubMed2004

Porosity evaluation and pore size distribution of a novel directly placed ceramic restorative material.

OBJECTIVES: The aim of this in vitro study was to compare porosity, i.e. voids or pores due to placement, of a new directly placed ceramic restorative material (DoxaDent, Doxa Certex AB, Uppsala, Sweden) to a glass ionomer (Fuji IX, GC Corporation, Tokyo, Japan), a hybrid composite control (Filtek Z250, 3M ESPE St Paul, MN, USA) and an amalgam control (Tytin, Kerr Orange, CA, USA). Pore distribution and size were determined for each material tested. METHODS: Standardized MOD preparations (one operator) on 20 extracted human molars had gingival margins located above and below the CEJ. Restored teeth (5 teeth/material) were sectioned in mesio-distal directions (two sections/tooth; n=10/group). Sections were polished through 1 microm Al2O3 abrasive. Porosity levels and size distributions were measured using SEM. Effects of different gingival extensions of inter-proximal boxes on porosity levels and distributions were investigated (mesial, occlusal, and distal regions). RESULTS: No MOD region was free of pores. Porosity in mesial, occlusal and distal boxes, respectively, for each restorative material were (vol%): Tytin: 1.3(0.9), 2.9(2.1), and 2.9(1.4); Filtek Z250: 2.6(1.0), 2.9(1.0), and 2.6(0.8); Fuji IX: 8.8(1.9), 7.9(1.7), and 7.7(1.8); Doxadent: 13.0(1.8), 12.4(1.7), and 11.5(1.4). Overall porosity ranged from 2.4(0.9)% for Kerr Tytin, 2.7(0.7)% for Filtek Z250, 8.0(1.1)% for GC Fuji IX, and 12.3(1.1)% for Doxadent. There was no difference between Z250 composite and Tytin amalgam, but differences existed between them with Fuji IX and Doxadent. No statistically significant difference (p>0.05) in porosity occurred among different restoration regions (mesial, distal and occlusal box) for any material. Total porosity levels for different measurement methods (point counting versus direct counting) were remarkable consistent (p>0.05). SIGNIFICANCE: Based on results of this limited study, the new directly placed ceramic restorative material (Doxadent) contains significantly (p<0.05) higher bulk porosity levels than both amalgam and composite. This may explain the lower than expected mechanical property values reported in other studies.

Aluminum Compounds↗
PubMedDate not supplied

Simultaneous activation technique: an alternative for bonding composite resin to glass ionomer.

PURPOSE: The purpose of this study was to evaluate a new simultaneous activation technique (SAT)-for the union between glass ionomer cements and composite resins. METHODS: Forty primary molars were embedded in self-curing acrylic resin. Class I cavity preparations were performed on the dentin surface and the teeth were randomly divided into 4 groups (N = 10). Two groups were restored with the SAT and 2 by etching the ionomer surface/sandwich technique (ST). The materials tested were Vidrion F (SS/ White), Vitremer (3M), and Z100 (3M). After 24 hours in aqueous solution at 37 degrees C, a tensile test was performed. The microleakage study was also performed by selecting 40 primary molars which were distributed in the same way as in the bond strength test. Furthermore, 1 tooth from each group of the microleakage test was evaluated by means of scanning electron microscopy. RESULTS: The SAT and ST did not show statistically significant differences in both tests. CONCLUSIONS: The SAT is a less complex, quicker, and feasible alternative for the bonding of glass ionomer cements to composite resins in primary molars.

Acid Etching, Dental↗
PubMedDate not supplied

Influence of light activation on the volumetric change of core foundation resins.

A core foundation system is frequently used in endodontically treated teeth that suffer excessive loss of the coronal portion of their structure. The volumetric shrinkage of core foundation resins may create marginal gaps that influence the bonding ability and longevity of a restored tooth. Little is known about how activation conditions of resin core foundation resin pastes affect their volumetric shrinkage. This study evaluated the influence of light intensity and light activation duration on volumetric shrinkage of direct core foundation resins. Two dual- and one light-activated core foundation resin pastes were employed. The material was placed in a Teflon mold 4 mm in diameter and 2 mm in height and extruded into a water filled dilatometer. The specimens were then light activated and the change in height of the meniscus of water was recorded using a charged-coupled device camera. The average volumetric shrinkage of the core foundation resins after 180 seconds ranged from 1.53% to 2.63%. For all materials tested, there was a tendency for increased volumetric shrinkage with increased light activation time and intensity. The results of this study indicate that the volumetric change of core foundation resins is influenced by the time and intensity of light activation.

Analysis of Variance↗
PubMed2005

Comparison of the root-end sealing ability of MTA and Portland cement.

The aim of this study was to compare the in vitro sealing ability of ProRoot MTA, ProRoot MTA (Tooth-Coloured Formula), ordinary Portland cement and white Portland cement when used as root-end filling materials. Twenty-four single-rooted human premolars were prepared and obturated using standard techniques, then retrofilled with the test materials. The prepared teeth were immersed in 1% methylene blue dye for 72 hours and then assessed for dye leakage. The depth of dye penetration was measured and expressed as a percentage of the length of the retrofilling. Data was analysed using ANOVA and Fisher's Least Significant Test (LSD) (p < 0.05). None of the teeth in any of the test groups showed leakage beyond the retrofillings. Given the low cost and apparently similar sealing ability of the cements, it is reasonable to consider Portland cement as a possible substitute for MTA as a root-end filling material. However, further tests, especially in vivo biocompatibility tests, need to be conducted before Portland cement can be recommended for clinical use.

Aluminum Compounds↗
PubMedDate not supplied

Marginal discrepancies and leakage of all-ceramic crowns: influence of luting agents and aging conditions.

PURPOSE: This study evaluated the marginal discrepancies and leakage of all-ceramic crowns cemented with different luting agents after fatigue tests. MATERIALS AND METHODS: Forty-eight all-ceramic crowns were cemented onto natural molars. Zinc-phosphate cement, compomer cement, and an adhesive composite resin luting system were used in 16 specimens each. Sixteen metal-ceramic crowns were cemented with zinc-phosphate cement as a control. Half of the specimens in each group were fatigued in a chewing simulator for 600,000 loading cycles with 3,500 thermocycles. The others received the 3,500 thermocycles only. An impression-replica technique and SEM were used for evaluation of the marginal discrepancies. Leakage of the specimens was microscopically assessed. RESULTS: There were no significant differences between marginal discrepancies of the groups, with the exception of porcelain shoulder margins in the metal-ceramic group, which had significantly larger discrepancies (P < .01). There was no significant effect of the fatigue tests on marginal discrepancies. However, significant differences of leakage were found between the groups cemented with the different luting agents after both fatigue tests. The adhesive composite resin luting system demonstrated the least leakage. The compomer cement showed an intermediate level of leakage, and the zinc-phosphate cement showed severe leakage that extended through the dentinal tubules to the pulp chambers. No significantly different effect of the two fatigue tests on the leakage was found. CONCLUSION: The adhesive composite resin luting system showed clinically acceptable marginal discrepancies and an excellent ability to minimize leakage of all-ceramic crowns.

Adhesives↗
PubMed2001

Biocompatibility and osseointegration in osteoporotic bone.

We implanted nails made of titanium (Ti6Al4V) and of two types of glass ceramic material (RKKP and AP40) into healthy and osteopenic rats. After two months, a histomorphometric analysis was performed and the affinity index calculated. In addition, osteoblasts from normal and osteopenic bone were cultured and the biomaterials were evaluated in vitro. In normal bone the rate of osseointegration was similar for all materials tested (p < 0.5) while in osteopenic bone AP40 did not osseointegrate (p < 0.0005). In vitro, no differences were observed for all biomaterials when cultured in normal bone-derived cells whereas in osteopenic-bone-derived cells there was a significant difference in some of the tested parameters when using AP40. Our findings suggest that osteopenic models may be used in vivo in the preclinical evaluation of orthopaedic biomaterials. We suggest that primary cell cultures from pathological models could be used as an experimental model in vitro.

Alloys↗