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PubMed2003

High-resolution diffusion-ordered spectroscopy to probe the microenvironment of JandaJel and Merrifield resins.

The success of organic reactions performed on a gel-phase resin is highly dependent on the accessibility of solvents, catalysts, and reagents to the interior of the resin. A variety of techniques including EPR, fluorescence, and Hildebrand solubility parameters (delta) have been used to probe reaction capabilities and in particular the microenvironment of a gel-phase resin. To provide a more detailed picture of the matrix in question, researchers have turned to NMR for the determination of the diffusion coefficients of solvents and small molecules in swollen beads to provide a means to compare the microenvironment of swollen beads. Since Merrifield and JandaJel resins display different swelling properties and have significantly different kinetic behavior, we undertook a comparative study of the diffusion coefficients of solvents and small molecules in both resins by high-resolution (1)H DOSY NMR. Our results show the following: (1) diffusion values for all studied solvents and small molecules are 20-30% higher in JandaJel compared to Merrifield resins, (2) in the absence of interactions between the resin and a given molecule, the diffusion values mirror the swelling properties of the resin, and (3) in the presence of strong intermolecular interactions between the gel and the considered molecule, the diffusion behavior in the gel is primarily influenced by the strength of the interactions and secondarily by the swelling properties of the resin. These results clearly show that the microenvironment of JandaJels is more "solution-like" than that of Merrifield resins, presumably due to the higher swelling capacity.

Chemistry, Organic↗

PubMed1994

Endotoxin affinity for provisional restorative resins.

PURPOSE: This study compared the relative affinity of Porphyromonas gingivalis and Escherichia coli endotoxin, bacterial cell envelope lipopolysaccharide (LPS), for three provisional resins. MATERIALS AND METHODS: As-polymerized and pumiced polymethyl methacrylate and polyethyl methacrylate resin discs were exposed to 1,000 endotoxin U/mL P. gingivalis or E. coli LPS in water for 24 hours at 37 degrees C, whereas control discs were placed in LPS-free water. LPS-treated discs were transferred at 24-hour intervals to fresh, LPS-free water for up to 96 hours, and the incubated eluates were tested for the presence of LPS. RESULTS: Initial adherence of P. gingivalis LPS to as-polymerized and pumiced-finish resin was a function of resin type, but surface characteristics modified adherence levels. When steady rates of elution were reached at 72 to 96 hours, as-polymerized specimens released significantly greater LPS levels than pumiced samples. Comparison of initial adherence of P. gingivalis and E. coli LPS with pumiced resins showed that adherence was based on a combination of LPS and resin type. P. gingivalis LPS had a greater relative affinity for polyethyl methacrylate, and E. coli LPS has a greater relative affinity for polymethyl methacrylate. Regardless of resin type, P. gingivalis LPS eluted at levels greater than E. coli LPS. CONCLUSIONS: The affinity of LPS for provisional resins seems to be a function of selective interactions based on the chemical nature of the resin, the surface finish of the resin, and the molecular structure of the LPS.

Analysis of Variance↗

PubMed2000

Adhesion testing of a denture base resin with 5 casting alloys.

PURPOSE: This study compared denture base resin shear bond strengths to silicoated Au-Pd, Au-Pd-Ag, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys used to fabricate frameworks for hybrid implant prostheses. Microleakage between alloy and resin was also compared among groups after specimen fracture. MATERIALS AND METHODS: Twelve cylindrical specimens were cast for each alloy. Each specimen was made from a ring-shaped pattern (diameter [d] = 12 mm and height = 4 mm) and machined to achieve uniform hollow centers (d = 6.5 mm). Castings were abraded with 250-micron aluminum oxide and ultrasonically cleaned in distilled water before silicoating. Denture base resin was processed to the internal surfaces of the silicoated specimens. All specimens were thermocycled (1,000 cycles) between 4 degrees C and 50 degrees C, and placed in basic fuchsin dye for a week. A punch (d = 3.8 mm) driven at a cross-head speed of 0.5 mm/min was used to push out the resin specimens. The force required to cause failure was converted to the nominal shear bond strength for each specimen, and mean shear bond strengths for the 5 groups of specimens (N = 12) were compared using one-way analysis of variance and the Tukey-Kramer HSD multiple range test (alpha = 0.05). Six of the 12 debonded resin samples for each alloy were selected at random and evaluated for dye penetration. Using an 80-square grid, the percentage of dye penetration was evaluated with an optical microscope (x25) to determine the percentage of grid area penetrated by the dye. One-way analysis of variance was used to compare the degree of microleakage among groups. RESULTS: The mean resin-alloy shear bond strengths for the Au-Pd (9.6 +/- 3.7 MPa) and Au-Ag-Pd-Cu (9.2 +/- 1.5 MPa) alloys were significantly greater than mean resin-alloy shear bond strength for the Au-Pd-Ag alloy (5.6 +/- 1.9 MPa). No other significant differences in resin-alloy shear bond strengths were noted among the alloy groups. No significant differences were noted for dye penetration into the resin specimens bonded to any of the 5 alloys. The mean grid area penetrated by the dye was 25% when results for the alloys were pooled. CONCLUSIONS: Alloy type influences the shear bond strength of a denture base resin to silicoated alloys, but no difference in bond strength was found between Au-Pd, Au-Ag-Pd-Cu, high-Pd, and Ni-Cr-Be alloys. In addition, under the conditions of this study, all groups showed a similar degree of microleakage, which penetrated approximately 25% of the bonded specimen surface area.

Air Abrasion, Dental↗

PubMed1998

Urea-formaldehyde resins and free formaldehyde content.

Specifications of wood adhesives must be in correlation with the requirements for the corresponding wood products, for which they will be used. Formaldehyde emission of wood products bonded with urea-formaldehyde resin based adhesives is strictly regulated by standards and there is a compromise is between formaldehyde emission and performance, such as strength, or water resistance. Since values of formaldehyde emission depend on the test method used, in Europe urea-formaldehyde resins for adhesives may generally be classified according to HCHO emission in the particleboard rating of Emission 0 to Emission I class (E-0 to E-1). According to DIN EN 120, particleboard quality E1 emits <6.5 mg/100 g dry article determined with the perforator method. Although a great number of factors effect the formaldehyde emission of the cured products, such as the hardener system, the type of wood etc., the emission of formaldehyde is in strict correlation with the free formaldehyde content of the resin before the curing process. E1 emission class can be achieved, if the free formaldehyde content of the resin is lower than 0.2% by mass. Urea-formaldehyde resins containing. higher than 0.5% free formaldehyde by mass exceed emission class E2, and are not accepted. Since the free formaldehyde content of the urea-formaldehyde resin effects the emission of formaldehyde in the cured product, low formaldehyde content must be ensured during resin synthesis. This can be achieved by properly selecting synthesis conditions as well as raw materials. The quality of raw materials is an essential and determining factor for the synthesis of urea formaldehyde resins. The principal changes which may take place in the formaldehyde solution on storage are the polymerization and precipitation of the polymer, Cannizzaro reaction, methylal formation, oxydation to formic acid, condensation to hydroxyaldehydes and sugars. Any of these reactions are detrimental to product quality. The state of formaldehyde is also an essential factor, since the reaction of poly(methylene glycol)s with urea leads to methylene ether linkages resulting in emission of formaldehyde during storage and later on during the process of curing. Hydrolysis, isomerisation and decomposition of urea may take place simultaneously during improper storage conditions, such as high humidity, high temperatures, industrial atmosphere. The side products formed affect the reaction with formaldehyde during the synthesis resulting in high free formaldehyde content of urea-formaldehyde resins. The relation between synthesis conditions, free formaldehyde content and performance of urea-formaldehyde resins are discussed in detail.

Formaldehyde↗

PubMed1995

Demonstration of a focused ion-beam cross-sectioning technique for ultrastructural examination of resin-dentin interfaces.

OBJECTIVES: focused ion-beam (FIB) etching, commonly used as a cross-sectioning technique for failure analysis of semiconductor devices, has recently been applied to biological tissues to expose their ultrastructure for examination. It was the aim of this investigation to determine the practical utility of FIB to cross-section resin-dentin interfaces in order to morphologically evaluate the completeness of resin penetration into the exposed collagen scaffold at the resin-dentin bond interface. METHODS: Two representative commercially available dentin adhesive systems were bonded to mid-coronal dentin. After appropriate fixation and dehydration of the resin-bonded dentin samples, a scanned focused ion-beam of a few tens of nano-meters in diameter was used to cross=section the resin-dentin interface. Examination of the interfacial ultrastructure was accomplished using a field-emission SEM. RESULTS: Results indicate possible artifact production at the cross-sectioned interface, hiding its actual ultrastructure, probably due to a heat-effect with possible recrystallization. Further studies of FIB are needed to optimize its usefulness for resin-dentin interface examinations and other biological tissue applications. SIGNIFICANCE: Complete resin saturation of the demineralized dentin surface-layer has been claimed to be the key factor for a long-lasting resin-dentin bond. A "clean" artifact-free micro-cross-sectioning technique may provide indisputable ultra-structural information about the depth of resin penetration into the demineralized zone. Such a test would be useful in the development of dentin adhesive systems.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2004

Stress distributions in adhesively cemented ceramic and resin-composite Class II inlay restorations: a 3D-FEA study.

OBJECTIVES: The purpose of this study was to investigate the effect of differences in the resin-cement elastic modulus on stress-transmission to ceramic or resin-based composite inlay-restored Class II MOD cavities during vertical occlusal loading. METHODS: Three finite-element (FE) models of Class II MOD cavity restorations in an upper premolar were produced. Model A represented a glass-ceramic inlay in combination with an adhesive and a high Young's modulus resin-cement. Model B represented the same glass-ceramic inlay in combination with the same adhesive and a low Young's modulus resin-cement. Model C represented a heat-cured resin-composite inlay in combination with the same adhesive and the same low Young's modulus resin cement. Occlusal vertical loading of 400 N was simulated on the FE models of the restored teeth. Ansys FE software was used to compute the local von Mises stresses for each of the models and to compare the observed maximum intensities and distributions. Experimental validation of the FE models was conducted. RESULTS: Complex biomechanical behavior of the restored teeth became apparent, arising from the effects of the axial and lateral components of the constant occlusal vertical loading. In the ceramic-inlay models, the greatest von Mises stress was observed on the lateral walls, vestibular and lingual, of the cavity. Indirect resin-composite inlays performed better in terms of stress dissipation. Glass-ceramic inlays transferred stresses to the dental walls and, depending on its rigidity, to the resin-cement and the adhesive layers. For high cement layer modulus values, the ceramic restorations were not able to redistribute the stresses properly into the cavity. However, stress-redistribution did occur with the resin-composite inlays. SIGNIFICANCE: Application of low modulus luting and restorative materials do partially absorb deformations under loading and limit the stress intensity, transmitted to the remaining tooth structures.

Bicuspid↗

PubMed2006

Tensile bond strength of Er,Cr:YSGG laser-irradiated human dentin and analysis of dentin-resin interface.

OBJECTIVES: As the bond strength of composite resin to Er,Cr:YSGG laser-irradiated dentin has not yet been evaluated, the objectives of this study were to investigate the tensile bond strength and to analyze the resin-dentin interface among bur-cut/acid-etched, Er,Cr:YSGG laser-ablated/acid-etched and Er,Cr:YSGG laser-ablated human dentin. METHODS: Crown dentin disks prepared from extracted human third permanent molars were used for the observation of surface morphological changes by scanning electron microscope (SEM). The laser energy parameters were 3.5 W and 20 Hz with water spray (air pressure level, 80%; water pressure level, maximum level). Another group of crown dentin disks were prepared for composite resin restoration and observation of resin-dentin bond interface after demineralization in 6N hydrochloric acid (HCl) for 1 min and deproteinization in 1% sodium hypochlorite solution (NaOCl) for 10 min. The tensile bond strengths of the three groups were measured by a universal testing machine at a crosshead speed of 0.5 mm/min. Fracture types at the dentin-resin interface were analyzed using the digital stereoscopic microscope and fractured surfaces of the debonded specimens were examined by SEM. RESULTS: All three groups showed that the treated surfaces were free of dentin debris and smear layer. The peritubular dentin protruded from the surrounding intertubular dentin after laser irradiation. The dentin-resin interface treated with Er,Cr:YSGG laser irradiation and acid etching demonstrated numerous resin tags converging into a bulge and then diverging again. The length of resin tags was greater than 100 microm. The tensile bond strengths of bur-cut/acid-etched, laser-ablated/acid-etched and laser-ablated human dentin were 5.37+/-1.51, 5.17+/-1.41 and 3.29+/-0.86 MPa, respectively. No statistical significance was found between the bur-cut/acid-etched and laser-ablated/acid-etched groups. The predominant fracture modes of bur-cut/acid-etched, laser-ablated/acid-etched and laser-ablated human dentin were Type 1 (50%), Type 2 (70%) and Type 1 (70%), respectively. SIGNIFICANCE: Er,Cr:YSGG laser irradiation affects adversely adhesion of resin to dentin but acid etching following laser irradiation could increase the tensile bond strength as high as that of bur-cut/acid-etched human dentin.

Acid Etching, Dental↗

PubMed2005

Changes in gloss after simulated generalized wear of composite resins.

STATEMENT OF PROBLEM: Generalized wear of composite resins in the noncontact area may result in changes of gloss, which can influence esthetics of restorations. PURPOSE: The purpose of this study was to determine the changes in gloss of composite resins after generalized wear simulation. Surface roughness and amount of wear were measured for comparison. MATERIAL AND METHODS: Generalized wear simulation was performed with a wear tester for 400,000 cycles with 6 composite resins (Estelite Sigma, Esthet X improved, Filtek Supreme, Heliomolar, Renamel Microfill, and Tetric-Ceram). Composite resin was placed into a mold (8 mm in diameter, 3 mm in depth) in an acrylic resin block, and 8 specimens were prepared per group. A flat-planed stylus made with polyacetal was loaded perpendicularly. Gloss was measured after every 100,000 cycles with a glossmeter in gloss units (GU). Average surface roughness (R(a)) of each specimen before and after 400,000 cycles of wear was determined. The amount of wear was measured with a 3-dimensional profilometer. Changes in gloss were analyzed by repeated-measures analysis of variance, and mean values were compared by Fisher's PLSD interval (alpha=.05). RESULTS: Gloss was influenced by the number of wear cycles and the composite resin, and there was a significant interaction (P=.000) between the number of wear cycles and the brand of composite resin. There were no significant correlations between the wear depth and the gloss or changes in gloss after 400,000 cycles. CONCLUSION: Generalized wear simulation for approximately 3 years of clinical use resulted in gloss changes of 36 to 64 GU, and maximum wear depth was in the range of 35 to 75 mum. Change in gloss varied among the composite resins, but average surface roughness was not influenced by the various composite resins.

Acrylic Resins↗

PubMed2000

Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials.

STATEMENT OF PROBLEM: Little published information is available comparing the properties of recently developed resin-modified gypsum and epoxy resin die materials, which are claimed to be superior to conventional type IV gypsum die materials. PURPOSE: This study compared the properties of 3 new die materials and 2 conventional type IV gypsum products. METHODS AND MATERIAL: The linear dimensional change, detail reproduction, surface hardness, abrasion resistance, and transverse strength of 2 recently introduced, resin-modified gypsum die materials (Resinrock and Milestone), a new epoxy resin die material (Epoxy-Die), and 2 conventional type IV gypsum die materials (Silky-Rock and Die-Stone) were studied. RESULTS: All gypsum products expanded, whereas the epoxy resin material contracted during setting. The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had the lowest value. CONCLUSION: The resin-modified gypsum products were not significantly superior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well-adapted castings.

Analysis of Variance↗

PubMed1995

Bond strength of an adhesive resin system with various dental substrates.

A laboratory study was conducted to evaluate the Panavia 21 resin-based adhesive system as a bonding agent between a variety of dental substrates. Panavia 21 resin was bonded directly to enamel and dentin and placed between nickel-chromium-beryllium (Ni-Cr-Be) specimens and enamel, dentin, other Ni-Cr-Be samples, and type III gold. Panavia 21 resin was also used to bond amalgam to dentin. Shear bond strengths were determined at 24 hours and after thermocycling at 3 months. The results of this study at both the 24-hour and the 3-months test periods indicate that the enamel bond strengths of Panavia 21 resin (24 hours, 19.3 +/- 5.5 MPa; 3 months, 23.7 +/- 4.4 MPa) exceeded its dentin bond strengths (24 hours, 7.8 +/- 1.4 MPa; 3 months, 8.8 +/- 3.2 MPa). The bond strengths between Panavia 21 resin and Ni-Cr-Be alloy (24 hours, 16.3 +/- 3.4 MPa; 3 months, 17.6 +/- 2.7 MPa) and those for Panavia 21 resin between Ni-Cr-Be alloy and dentin (24 hours, 18.7 +/- 4.2 MPa; 3 months, 19.8 +/- 5.3 MPa) were comparable to adhesive enamel bond strengths. High bond strengths were also generated by Panavia 21 resin between Ni-Cr-Be alloy and type III gold (24 hours, 39.3 +/- 5.9 MPa; 3 months, 35.5 +/- 7.1 MPa). The greatest bond strengths observed during both test time periods for Panavia 21 resin were between Ni-Cr-Be alloy and enamel (24 hours, 54.2 +/- 10.7 MPa; 3 months, 56.4 +/- 7.1 MPa) and between two samples of Ni-Cr-Be alloy (24 hours, 55.1 +/- 5.6 MPa; 3 months, 49.1 +/- 8.6 MPa). Panavia 21 resin produced high bond strengths between a variety of dental substrates commonly used for the placement of fixed prosthodontic restorations.

Adhesives↗

PubMed1985

Further characterization of bacterial adherence to urinary bladder mucosa: comparison with adherence to anion exchange resin.

Bacterial adherence to anion exchange resin has recently been reported to provide a useful, rapid, in vitro screening assay for identifying putative antiadherence agents. The studies presented in this report provide additional evidence that adherence to anion exchange resin is similar to urinary bladder mucosa adherence. Results are as follows. 1) Heparin inhibits the adherence of Escherichia coli, Klebsiella ozaenae, Proteus mirabilis, Streptococcus fecalis and Pseudomonas aeruginosa to both the mucin deficient bladder and anion exchange resin. 2) Drugs which inhibit E. coli adherence to the bladder also inhibit E. coli adherence to the resin and conversely, drugs which do not effect E. coli adherence to the resin do not affect attachment to the bladder. 3) Extracts from mammalian urinary bladder mucosa prevent E. coli adherence to both the bladder and resin. 4) The ability of heparin to displace preattached bacteria from anion exchange resin is inversely proportional to the time the bacteria are in contact with resin. Similar results were obtained for the ability of heparin to displace bacteria from the bladder. These studies indicate that bacterial adherence to anion exchange resin responds to heparin and other chemical agents in a manner similar to the mucin deficient rabbit urinary bladder. Because of the ease and rapid nature of this in vitro assay, it serves as a useful screen for potential bacterial antiadherence agents and could be used to help elucidate mechanisms of bacterial attachment.

Adhesiveness↗

PubMed2004

The effect of a resin-based sealer on crown retention for three types of cement.

STATEMENT OF PROBLEM: In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products. PURPOSE: This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents. MATERIAL AND METHODS: Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test. RESULTS: Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement. CONCLUSIONS: Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.

Analysis of Variance↗

PubMed2001

A light curing method for improving marginal sealing and cavity wall adaptation of resin composite restorations.

OBJECTIVE: The aim of this study was to evaluate whether the method of light curing could influence: (a) marginal sealing and resin composite adaptation to the cavity wall; (b) polymerization contraction rate; and (c) the hardness at the top and bottom surfaces of a body of resin composite. METHODS: Standard cylindrical cavities, 1mm deep and 3mm in diameter were prepared on flat superficial dentin surfaces in bovine teeth. The teeth were bonded with one of two adhesive systems (Clearfil Photo Bond, and Super-Bond D Liner) and filled with a hybrid resin composite. The resins were cured using three light intensities of 600, 270 and 20mW/cm(2), and various curing times. After thermal cycling, the specimens were subjected to a dye penetration test to evaluate marginal sealing and adaptation of the resin composite to the cavity walls. In addition, using the same curing conditions, the rate of polymerization contraction was measured. The difference of hardness over time of composite specimens was measured using Knoop hardness measurements taken at the top and bottom surfaces of resin specimens made in a Teflon mold the same dimensions as the cavity prepared in dentin. RESULTS: When the composite was light cured with an initial light intensity of 270mW/cm(2) for 10s, a 5s interval then a light intensity of 600mW/cm(2) for 50s, the best marginal sealing and cavity wall adaptation was observed compared with the other curing modes. Earlier hardening occurred at the resin composite base compared with the top surface of the composite, and most of the polymerization contraction was completed during the initial flowable stage of the resin composite. All other methods demonstrated results with some degree of marginal opening and cavity wall gap formation, the worst being 600mW/s for 60s. SIGNIFICANCE: The use of a low initial light intensity (270mW/cm(2)) for 10s followed by high intensity light (600mW/cm(2)) for 50s provides the best adaptation of resin composite to cavity walls and possibly the least polymerization contraction stress.

Analysis of Variance↗

PubMed2002

Effects of mechanical properties of adhesive resins on bond strength to dentin.

OBJECTIVES: The purpose of this study was to evaluate the relationship between the micro-tensile bond strength to dentin and mechanical properties of the cured adhesive resins. METHODS: Coronal dentin surfaces of extracted human teeth were treated with four commercial self-etching priming systems (Clearfil SE Bond; UniFil Bond; Tokuso Mac-Bond II; and Imperva Fluoro Bond) and bonded with a resin composite. After 24h storage in water at 37 degrees C, the bonded specimens were trimmed and subjected to micro-tensile bond strength testing at a cross-head speed of 1mm/min. Debonded surfaces were observed under a FE-SEM. For testing mechanical properties, 0.7-mm thick slabs of each adhesive resin were prepared, light-cured, and stored dry at the room temperature for 24h. After trimming, ultimate micro-tensile strength was measured. The nano-hardness and Young's modulus were also evaluated using cured adhesives that were prepared in the same manner as described above. RESULTS: The micro-tensile bond strengths to dentin and ultimate micro-tensile strengths of the resins were not significantly different among all systems (P>0.05). However, the nano-hardness and Young's modulus of Clearfil SE Bond and Imperva Fluoro Bond adhesive resins were significantly higher than those of UniFil Bond and Tokuso Mac-Bond II resins (P<0.05). The micro-tensile bond strength significantly correlated with the ultimate micro-tensile strength of the resins (r(2)=0.77; P<0.05), but was not correlated with the nano-hardness or Young's modulus (P>0.05). SEM observation of the debonded surfaces revealed a mixed type of fracture with a combination of interfacial and cohesive failure within the adhesive resin. SIGNIFICANCE: The four self-etching priming systems exhibited similar dentin bond strengths, which also correlates with the ultimate strength of the adhesive resins.

Acid Etching, Dental↗

PubMed1999

An investigation of the variables which may affect the bond between plastic teeth and denture base resin.

OBJECTIVES: The failure of the bond between acrylic resin denture base material and resin teeth remains a significant problem. This study evaluated the tensile bond strength of specimens produced by commonly employed tooth preparation and processing methods as used in dental laboratories. METHODS: Twenty-two experimental groups, each consisting of 36 specimens, were investigated by subjecting the tooth-resin bond to tensile loading. The groups were allocated to one of five experimental sets to investigate: (a) effect of resin dough time, (b) effect of tooth surface condition, (c) effect of processing variables, (d) effect of monomer cementing, and (e) effect of acrylic resin cement. The results were analysed statistically using a one factor ANOVA and a Student t test. RESULTS: A significantly stronger bond was obtained when the resin was packed late in the dough stage, and a superior bond, in all cases, when high-impact resin was used. Tooth surface modification by grinding or grooving made no significant difference when compared with unmodified surfaces. Wax-contaminated surfaces produced highly significant weaker bonds. Time of introduction and duration of water-bath processing had no significant effect on bond strength. Monomer cementing of the tooth surface, especially with high-impact monomer. significantly improved the bond strength. The application of resin cements was found to produce the most significant increase in denture tooth bond strength. CONCLUSIONS: The important steps in obtaining a consistently high value denture tooth bond are thorough dewaxing of the tooth surface followed by the application of a suitable resin cement.

Acrylic Resins↗

PubMed2004

Mechanical behavior of bioactive composite cements consisting of resin and glass-ceramic powder in a simulated body fluid: effect of silane coupling agent.

Time-dependent strength behavior was investigated for bisphenol-a-glycidyl methacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) resin cements combined with glass-ceramic A-W filler treated with various kinds of silane coupling agents. The fracture strength of the composite resin cements was measured by three-point bending as a function of stressing rate in a simulated body fluid (SBF), and thereby the stress-corrosion susceptibility constant was evaluated. The fracture strength was found to depend on the kind of coupling agent used. For the present Bis-GMA/TEGDMA resin, the silane coupling agents without hydrophilic amine groups can be used to obtain good adhesion between resin and A-W filler owing to their nature of co-polymerizing with the resin. On the other hand, all the composite resin cements showed nearly the same degree of stress-corrosion susceptibility whether the A-W fillers were treated or untreated with silane coupling agents. This means that the stress-corrosion susceptibility of the present composite cements is predominantly affected by that of the matrix resin. Thus, the microcrack formation and growth at the resin matrix near particle - resin interface were thought to determine overall time-dependent strength behavior of the composite cements.

Biocompatible Materials↗

PubMed2003

Effects of thermocycling on the bond strength of a resin-modified glass ionomer cement: an in vitro comparative study.

This study investigated the effects of thermally induced stresses (thermocycling) on the shear bond strength of resin-modified, chemically cured, glass ionomer cement for use as an orthodontic bonding agent. A conventional no-mix composite resin was also used as a control. Mesh-based metal orthodontic brackets were bonded to extracted human premolars using either the resin-modified glass ionomer cement or the no-mix composite resin. Specimens were stored either in water at 37 degrees C for 24 hours for baseline data or thermocycled between 5 degrees C and 55 degrees C for 200 and 20,000 cycles before testing the in vitro shear bond strengths. Thermocycling reduced shear bond strengths for all specimens. The resin-modified glass ionomer cement showed a 11.1% decrease after 200 thermocycles and 26.5% decrease after 20,000 thermocycles, whereas the no-mix adhesive resin showed only 5.7% and 17.9% reductions, respectively. Analysis of variance showed statistically significant differences between the mean shear bond strengths of the groups at the P < .001 level of significance. For the resin-modified glass ionomer cement groups, the predominant bond failure site was at the bracket-adhesive interface. The results of this study suggest strongly that resin-modified glass ionomer cements offer a viable alternative to conventional no-mix composite resins, with satisfactory in vitro shear bond strength even after 20,000 thermocycles.

Analysis of Variance↗

PubMed2002

In vitro wear simulation measurements of composite versus resin-modified glass ionomer luting cements for all-ceramic restorations.

BACKGROUND: Although composite cements are generally indicated for cementation of all-ceramic restorations, some manufacturers of dental cements propose that resin-modified glass ionomers (RMGIs) may be used for cementation of high-strength ceramic restorations. PURPOSE: This study was undertaken to compare the in vitro abrasion and attrition wear of two dual-cure cements (in dual-cure and self-cure modes) and two RMGI cements when placed between ceramic and enamel to simulate the margin of a restoration. METHODS: Rectangular fragments of pressed ceramic (Empress 2) were cemented between the halves of bovine incisors sectioned mesiodistally, using one of the following materials: RelyX ARC, Variolink II, RelyX Luting, or ProTec CEM. The two resin cements were tested in dual-cure and self-cure modes. A three-body wear test was performed in the new Oregon Health Sciences University (OHSU) oral wear simulator (100,000 cycles; abrasion load: 20 N; attrition load: 90 N). Degree of conversion of resin cements was determined by Fourier transform infrared spectroscopy. Results were analyzed by analysis of variance and Tukey's test (p = .05). Epoxy replicas of wear specimens were observed in the scanning electron microscope. RESULTS: No significant differences in abrasion wear (RelyX ARC dual-cure: 11 +/- 4.4 microm; RelyX ARC self-cure: 17 +/- 7.0 microm; Variolink dual-cure: 14 +/- 8.6 microm; Variolink self-cure: 23 +/- 10.7 microm) or attrition wear (RelyX ARC dual-cure: 18 +/- 6.4 microm; RelyX ARC self-cure: 31 +/- 4.5 microm; Variolink dual-cure: 32 +/- 6.8 microm; Variolink self-cure: 39 +/- 15.9 microm) were found between activation modes of the resin cements. ProTec CEM (32 +/- 8.7 microm) showed abrasion similar to that of Variolink II and RelyX ARC self-cure. Resin-modified glass ionomers showed more attrition wear than the resin cements (ProTec CEM: 62 +/- 13.0 microm; RelyX Luting: 69 +/- 7.1 microm). RelyX ARC showed a similar degree of conversion for both activation modes (dual-cure: 70 +/- 4.3%; self-cure: 68 +/- 1.2%), but Variolink II had a higher degree of conversion in dual-cure mode (67 +/- 0.5% vs 60 +/- 1.0%). Cement wear was accompanied by marginal breakdown and increased surface roughness of enamel and ceramic. CONCLUSIONS: The activation mode of resin cements did not influence their wear resistance. The RMGIs underwent higher attrition wear than the resin cements. CLINICAL SIGNIFICANCE: Increased submargination associated with marginal breakdown and increased roughness of the surrounding structures may be expected when ceramic inlays are cemented with resin-modified glass ionomers.

Analysis of Variance↗