Biomedical subjects

J D Eick

Publications and source records attributed to J D Eick.

At least 37 records · Page 2Linked to original sources

PubMed1999

Shear strength of the physis varies with anatomic location and is a function of modulus, inclination, and thickness.

Slipped capital femoral epiphysis involves the gradual displacement of the femoral head relative to the neck. Many theories have arisen to explain this slip. Frequently cited etiological factors include increases in physeal thickness and inclination. Slipped epiphysis has been postulated to result from shear overload that causes separation through the hypertrophic cellular zone. We sought to answer the following questions: (a) Do significant regional differences in strength and stiffness exist within a given physis? (b) Are regional differences in resistance to shear related to thickness and inclination of the physis? (c) Does physeal compression cause mammillary interdigitation to begin sooner and increase the resistance to shear before, during, and after failure? (d) Does shear failure occur at displacements detectable by radiography? and (e) Does cleavage occur throughout the entire columnar zone, and do the chondrocyte columns remain intact on both sides of the cleavage plane? We prepared beam-shaped microstructural samples from different sites of the bovine proximal tibial physis. We determined thickness, inclination, ultimate stress and strain, modulus, and strain energy density at ultimate stress as a function of location. Using scanning electron microscopy, we also examined the entire failed surface of several samples. Forty-eight samples were tested by displacing the epiphysis end anteriorly, without axial (across the thickness) constraint; 41 were sheared while an average axial compressive stress of 0.3 MPa was applied to the physis. The posterior region had the greatest strength and stiffness, lowest physeal thickness, and steepest inclination. Compressing the plate did not increase the shear strength or tangent modulus. Ultimate strength varied inversely with thickness and increased when shearing up steeper inclinations; however, it was more strongly associated with the modulus, implying that additional factors control both strength and modulus. Scanning electron microscopy revealed that the plane of fracture differed widely between and within samples, involving all zones of the growth plate. On either side of the fracture, individual chondrocyte columns remained intact, although separated from neighboring columns.

Animals↗

PubMed1999

In vitro cytotoxicity of solid epoxy-based dental resins and their components.

OBJECTIVE: The objective of this study was to evaluate the effect of adding a spiroorthocarbonate (SOC) or a polyol on the cytotoxicity of epoxy-based dental resins. METHODS: Resins contained one of the epoxies: diglycidyl ether Bisphenol A (GY-6004); 3,4-epoxycyclohexanemethyl-3,4-epoxycyclohexane carboxylate (UVR-6105); vinyl cyclohexane dioxide (ERL-4206) or the three-epoxy mixture (Epoxy-M). The SOC was t/t-2,3,8,9-di(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane (SOC). The polyols were polytetrahydrofuran (p-THF-250) and polycaprolactone triol (TONE-301). The photoinitiator (4-octylphenyl)phenyliodonium hexafluoroantimonate and camphorquinone were used for light curing the resins. Four types of resins (epoxy, SOC/epoxy, polyol/epoxy and SOC/polyol/epoxy) were evaluated for cytotoxicity as solids in the agar diffusion assay and as aqueous extracts in the MTT assay using L929 cells. RESULTS: In agar diffusion analysis, ERL-4206 and UVR-6105 resins were severely cytotoxic (+3), but the addition of SOC changed them to non-cytotoxic (-). Addition of 1-3% SOC changed Epoxy-M from mild (+) to non-cytotoxic. Adding SOC changed GY-6004 from moderate (+2) to mild (-) cytotoxicity. Generally, addition of SOC did not change cytotoxicity when added to polyol/epoxy combinations. Either polyol produced resins with reduced cytotoxicity when added to UVR-6105, but the opposite occurred when added to Epoxy-M resins. In MTT analysis, percent cell survival from 100 microliters resin extracts were statistically compared (ANOVA, p < 0.05). Epoxy-M and GY-6004 resin extracts were significantly less cytotoxic than UVR-6105 and ERL-4206 resin extracts were. Overall, the SOC component reduced the cytotoxicity of all SOC/epoxy combinations, except SOC/ERL-4206, which was significantly more cytotoxic than ERL-4206 resin extract. This may be the result of cell fixative effects observed for SOC/ERL-4206 in agar diffusion analysis. Addition of SOC produced significantly less cytotoxic SOC/polyol/Epoxy-M resins when compared to its non-SOC counterpart. The contrary result was obtained with SOC/polyol/UVR-6105 resin combinations. Consistent with agar diffusion results, adding polyol significantly decreased cytotoxicity of UVR-6105 resins. The cytotoxicity of these resins may be related to the 50% cytotoxicity (TC50) of their components as leachates. The TC50 values of the individual components were compared to BISGMA. Polyols, epoxy monomers, SOC monomer and camphorquinone were significantly (p < 0.05) less cytotoxic than BISGMA. SIGNIFICANCE: Addition of SOCs and polyols in the formulation of epoxy-based resins may contribute to development of biocompatible dental composites.

Analysis of Variance↗

PubMed1998

Application of solubility parameter theory to dentin-bonding systems and adhesive strength correlations.

The principal aim of this study was to investigate the relationships between the solubility parameters of ectched dentin, and adhesive primer solutions and adhesive bond strength. Solubility parameters characterize the molecular interactions which determine physical properties such as wetting, and thus can serve as tools to aid development of polymeric adhesives and interpenetrating polymer networks. If an adhesive monomer has a solubility parameter close to that of a polymer substrate, then the monomer may act as a solvent for the polymer and penetrate below the surface. Subsequent polymerization of the monomer may then produce an interpenetrating network, thus adhering without necessarily forming primary chemical bonds to the substrate. The dentin substrate considered in this study was abraded dentin treated with ethylenediaminetetraaceitc acid. Solubility parameters delta pr, delta h, and delta d calculated for the etched dentin substrate were 20.3, 23.6, and 16.0 (J/cm3)1/2, respectively. Solubility parameters of the primers were expressed using Hansen's three-dimensional scheme. The data indicate a correlation between the calculated solubility parameters of the etched dentin, and dentin primers and the resulting bond strengths. The results corroborate the significance of solubility parameter considerations for adhesive bonding to dentin.

Acid Etching, Dental↗

PubMed1998

Microtensile testing of dentin adhesives.

OBJECTIVES: This study was conducted in order to compare the microtensile and shear bond strengths of five commercial dentin adhesive systems. Scotchbond Multipurpose with maleic acid (SM), Scotchbond Multipurpose with phosphoric acid (SP), Scotchbond Multipurpose Plus (SBP), Clearfil Liner Bond System (CL), and Prime and Bond (PB) were tested. METHODS: Thirty extracted unerupted third molars, in groups of six teeth per adhesive system, were prepared for microtensile testing. The specimens were tested following a 24 h incubation at 37 degrees C in normal saline. Shear bond testing was performed on 35 additional teeth, using seven teeth per adhesive system. After testing, the fracture sites were observed using light microscopy and a scanning electron microscope to determine the type of failure involved. RESULTS: The microtensile test results (mean +/- SD) were SM, 24.6 +/- 7.2 MPa; SP, 28.8 +/- 11.8 MPa; SBP, 22.7 +/- 6.5 MPa; PB, 25.5 +/- 9.4 MPa; and CL, 36.8 +/- 10.0 MPa. A Bonferroni post-hoc test showed significantly (p < 0.05) greater strength for CL compared to SM, SP, SBP, and PB. The shear bond strength test results were SM, 19.4 +/- 4.4 MPa; SP, 24.5 +/- 8.4 MPa; SBP, 15.3 +/- 4.9 MPa; PB, 23.2 +/- 7.1 MPa; and CL, 24.8 +/- 3.5 MPa. No statistically significant differences were found among the shear bond strength test results. The shear bond test produced significantly more failures within dentin and composite than the microtensile method. SIGNIFICANCE: It is concluded that the microtensile test produced a more definitive assessment of adhesive bond strength than the shear bond test. Microtensile testing showed CL to be significantly stronger than SM, SP, SBP, and PB (p < 0.05).

Analysis of Variance↗

PubMed1998

A TEM study of two water-based adhesive systems bonded to dry and wet dentin.

To keep the exposed collagen scaffold penetrable to resin, it has been recommended that the conditioned dentin surface be maintained in a visibly moist condition, a clinical technique commonly referred to as wet bonding. In this study, resin-dentin interfaces produced with two water-based adhesive systems--OptiBond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M)--were compared by transmission electron microscopy, following the application of either a dry- or a wet-bonding technique. The hypothesis advanced was that the ultramorphology of the hybrid layer would differ depending on which bonding method was applied. A morphologically well-organized hybrid layer of collagen fibrils intermingled with resin in tiny interfibrillar channels was consistently formed by the OPTI system. The SBMP system was found to produce a hybrid layer with a more variable ultrastructure, less distinctly outlined collagen fibrils, and a characteristic electron-dense phase located at its surface. No major differences in hybrid layer ultrastructure were observed when the two adhesive systems investigated were bonded to either dry or wet dentin. When the adhesives were dry-bonded, no ultrastructural evidence of collapsed demineralized collagen, incompletely or not at all infiltrated by resin, could be detected. In addition, when the two adhesives were bonded to wet dentin, no signs of overwetting phenomena, that would have indicated that water was ineffectively removed, were apparent. It has been hypothesized that the amount of water provided with the hydrophilic primer solution of either of the two adhesive systems investigated suffices to re-hydrate and re-expand the gently air-dried and collapsed collagen network. Further research should be directed to determine whether this hypothesized self-rewetting effect can be extrapolated to other adhesive systems that provide water-based primers.

Adhesives↗

PubMed1998

Elements of light-cured epoxy-based dental polymer systems.

The greatest problem with current dental composite systems is their polymerization shrinkage. Extensive work is being done by many investigators to alleviate this problem. Our approach has been to examine epoxy- and spiro-orthocarbonate (SOC)-based resins. The hypothesis to be tested in this study was that the cure characteristics of experimental visible-light-cured epoxy resin systems are governed by the types and concentrations of co-reactants and activators. Resin samples containing onium salt initiators and a thiozanthone sensitizer were successfully cured by means of either an experimental visible-light irradiation system or a commercially available dental lamp. Test resins consisted of di-epoxies alone or in combination, epoxy mixtures in combination with an SOC, or an epoxy in combination with a caprolactone-derived polyol. Significant findings were as follows: (a) Resins containing the SOC had longer cure times than their counterparts; (b) the optimum ratios of epoxy to polyol for most rapid cure were 50:50 or 60:40 under conditions tested; (c) resins containing TONE 305 polyol generally were faster to cure than those containing no polyol, or TONES 201 or 310; and (d) a resin mixture was found that had a cure time of 1 to 3 min when irradiated with a commercial dental lamp. Based on this exploratory study, it should be possible for clinically relevant cure times to be achieved for visible-light-cured epoxy-based resins by careful manipulation and optimization of key elements.

Carbonates↗

PubMed1998

The effects of different storage conditions on polyether and polyvinylsiloxane impressions.

While being shipped to a laboratory, impressions can be exposed to excessive temperatures. This study compared the effects of different time and temperature storage conditions, including temperature extremes of 66 C and -10 C, on the accuracy of addition silicone and polyether impressions. The greatest distortion generally occurred as a result of the 66 C temperature extreme. The authors recommend that impressions be poured in stone according to manufacturers' specifications before being shipped to a dental laboratory.

Calcium Sulfate↗

PubMed1997

Epoxy-embedded versus nonembedded TEM examination of the resin-dentin interface.

When transmission electron microscopy (TEM) is used to evaluate resin-dentin interface specimens for completeness of hybridization, the epoxy resin embedding medium that normally facilitates ultrathin sectioning may produce a secondary or artifactual hybrid layer. This secondary hybrid layer, composed of epoxy resin rather than adhesive resin, may fill the pores that remain as evidence of incomplete resin infiltration, obscuring the fact that they ever existed. In this study, resin-dentin interfaces produced by two dentin adhesive systems, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), were comparatively investigated by TEM in epoxy-embedded and nonembedded nondemineralized sections. The hypothesis advanced was that no difference in ultramorphology of the hybrid layer would result from either specimen preparation method. The two adhesive systems were applied to four mid-coronal dentin disks per manufacturer's instructions. One half of each sample was processed following common procedures for TEM sample preparation with epoxy embedding, whereas the other half was not embedded but instead immersed in hexamethyldisilazane (HMDS), dried and mounted so that it protruded from a base of cold-cure acrylic resin. Each sample was then sectioned using a diamond knife in an ultramicrotome. With either means of preparation, a hybrid layer with a relatively uniform electron density and a loose collagen fibril arrangement with electron lucent interfibrillar channels was formed by OPTI. At the base of the hybrid layer, collagen fibrils were anchored in the underlying unaffected dentin, and no microporosities or gaps were observed. Similarly, whether SBMP was embedded or nonembedded, it was found to have a hybrid layer of variable electron density and an electron dense phase localized at the surface of the hybrid layer. No porosities were evident at the base of the hybrid layer. Thus, with either of the two adhesive systems, no ultrastructural difference in hybrid layer formation was observed between epoxy-embedded and nonembedded sections, and no direct evidence of ineffective resin-infiltration of the demineralized collagen scaffold was found.

Acid Etching, Dental↗

PubMed1997

Current concepts on adhesion to dentin.

This review examines fundamental concepts in bonding to dentin. Emphasis is placed on the structure and permeability characteristics of dentin and how they may influence its interaction with adhesive resin. Several new techniques to examine the interfaces between resin and dentin are reviewed along with some of their limitations. The advantages and disadvantages of acid etchants/conditioners vs. self-etching conditioners/primers are discussed. The problems of matching the surface tension of resin-bonding systems to the surface energy of the substrate are reviewed in terms of wetting the various components of dentin. The problems associated with matching the permeability of intertubular dentin to the diffusibility of bonding reagents are explored. Speculation is advanced on how to ensure polymerization and wetting of dentinal collagen. Theoretical problems associated with dentin bonding and with bond testing are reviewed to encourage future research in this rapidly developing area.

Adhesives↗

PubMed1996

Design and development of isocyanatoacrylates as dental adhesives.

During the last 12 years, significant progress has been made in the development of dental adhesive systems. Some of the more promising systems are based on multifunctional structures that contain polymerizable vinyl double bonds and reactive isocyanate groups. The utility of compounds with such structures as adhesives arises in part because their isocyanate functionality is available for reaction independently, without compromising the reactivity of the vinyl groups. The hypotheses tested in this investigation were: (1) that the monomer reactivity ratios (r1, r2) for the free-radical-initiated copolymerization of ethyl alpha-isocyanatoacrylate (alpha-EIA) and 2-isocyanatoethyl methacrylate (IEM) with selected vinyl monomers can be determined; (2) that these reactivity ratios can be used to establish Q (reactivity) and e (polarity) values for alpha-EIA and IEM; and (3) that these reactivity parameters can be useful in designing copolymers with controlled compositions for dental adhesive applications. The free-radical copolymerization characteristics of alpha-EIA and IEM were studied. The isocyanate monomers were copolymerized at seven comonomer ratios with n-butyl acrylate (NBA), methyl methacrylate (MMA), and styrene (STY). Reactivity ratios, r1 and r2, were calculated for each of the copolymer systems, giving:IEM (r1) = 0.38 and STY (r2) = 0.44; IEM (r1) = 1.19 and MMA (r2) = 0.84; IEM (r1) = 2.50 and NBA (r2) = 0.40; alpha-EIA (r1) = 2.20 and STY (r2) = 0.06; alpha-EIA (r1) = 7.00 and MMA (r2) = 0.10; and alpha-EIA (r1) = 23.50 and NBA (r2) = 0.04. The Q (reactivity) and e (polarity) values for IEM and alpha-EIA were calculated from r1 and r2 with use of the Alfrey-Price equations, giving, for IEM, Q = 0.89 and e = 0.60, and, for alpha-EIA, Q = 7.64 and e = 0.74. These reactivity parameters are useful for tailoring copolymers with controlled compositions and properties. Based on these calculated reactivity parameters, several copolymers of IEM [for example, IEM/2-hydroxyethyl methacrylate (HEMA)] are currently being prepared and evaluated as adhesives.

Acrylates↗

PubMed1996

Correlative transmission electron microscopy examination of nondemineralized and demineralized resin-dentin interfaces formed by two dentin adhesive systems.

The resin-dentin interface formed by two dentin adhesives, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), was ultramorphologically examined by transmission electron microscopy (TEM). Ultrastructural information from nondemineralized and demineralized sections was correlated. It was hypothesized that the different chemical formulations of the two adhesives would result in a different morphological appearance of the hybrid layer. Ultrastructural TEM examination proved that each of the two dentin adhesive systems was able to establish a micromechanical bond between dentin and resin with the formation of a hybrid layer. However, the interfacial hybridization process that took place to produce this resin-dentin bond appeared to be specifically related to the chemical composition and application modes of both systems. OPTI consistently presented with a hybrid layer with a relatively uniform ultrastructure, electron density, and acid resistance. These three parameters were found to be more variable for the hybrid layer formed by SBMP. Characteristic of SBMP was the identification of an amorphous phase deposited at the outer surface of the hybrid layer. Although both adhesive systems investigated follow a total-etch concept, their specific chemical formulations result in different interfacial ultrastructures that are probably related to different underlying bonding mechanisms. The clinical significance of these morphological findings, however, is still unknown.

Acid Etching, Dental↗

PubMed1996

Quantitative analysis of the dentin adhesive interface by Auger spectroscopy.

The ultimate success of a dentin adhesive bond is dependent in large part on specific conditions at the interface between the tooth and the adhesive. Most current dentin adhesive systems use some sort of pre-treatment to demineralize the first few microns of the dentin surface, leaving a meshwork of collagen into which the adhesive resin can penetrate, infiltrate, and polymerize. The general hypothesis tested in this experiment was that the penetration and distribution of adhesive resin into the demineralized zone are a function of the conditioner used as a pre-treatment for the adhesive application. Four commercially available adhesive systems were modified to incorporate hydroxyethylthiomethacrylate (HETMA), a sulfur-substituted, traceable analogue of 2-hydroxyethylmethacrylate (HEMA), thereby allowing for a qualitative measurement of the amount and distribution of monomer in the treated dentin substrate by energy-dispersive x-ray spectroscopy (EDS) and a quantitative measurement by Auger electron spectroscopy (AES). The dentin pre-treatments investigated were: (1) 10% citric acid/3% ferric chloride, (2) 10% maleic acid, (3) 2.5% nitric acid, and (4) an alcoholic solution of HEMA with a phosphorus acid ester. These pre-treatments were applied to freshly extracted teeth that had been sectioned to expose the dentin and ground to simulate the smeared layer. After the appropriate pre-treatment was applied, a 10% (v/v) solution of HETMA in acetone was applied to the surface, followed by the corresponding adhesive resin, which was then polymerized. The samples were then processed for observation by scanning transmission electron microscopy (STEM), AES, and STEM/EDS analysis. The results indicated significant differences in the ability of HETMA to penetrate the dentin surface conditioned by the four pretreatments investigated here. This study also demonstrated that AES and STEM/EDS could be used in a correlative fashion to determine the distribution of HETMA within or adjacent to the treated dentin surface.

Dentin-Bonding Agents↗

PubMed1995

Comparison of tetrazolium colorimetric and 51Cr release assays for cytotoxicity determination of dental biomaterials.

OBJECTIVES: The purpose of this study was to compare a methylthiazole tetrazolium (MTT) dye colorimetric method with the standard 51Cr assay as methods of assessing cytotoxicity of dental materials. METHODS: Two MTT-based colorimetric formats, test tube and 96-well microplate methods, were compared to the 51Cr release assay. A series of eight dental materials were evaluated. Cytotoxicity profiles were determined for each test material. A TC50 value (Toxic Concentration required to kill 50% of the cells) was determined for each biomaterial, and these results were used to make statistical comparisons between the methods. RESULTS: The three methods were statistically correlated (p<0.005) by comparison of the eight samples tested. That is, the same rank in toxicity was given by the two tetrazolium sample formats and the 51Cr method. SIGNIFICANCE: The MTT assay was found to have several advantages in comparison to the current standard 51Cr release assay. Optimized in the 96-well format, complete dose response curves and greater sample comparisons can be made rapidly, making the MTT method more economical in time and cost. Furthermore, the MTT method is based on intracellular biochemical changes, measuring cell viability rather than cell morbidity, and has lower detectable limits than the 51Cr release method. There is also less detector chemical binding interference than encountered in the 51Cr release method.

Animals↗

PubMed1995

Scanning transmission electron microscopy/energy-dispersive spectroscopy analysis of the dentin adhesive interface using a labeled 2-hydroxyethylmethacrylate analogue.

In an attempt to compare the morphology of the dentin adhesive interface and the wetting and penetration of the adhesive in relation to the dentin surface, we studied four dentin adhesive systems using scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). 2-Hydroxyethylmethacrylate (HEMA), a monomer common to many commercial dentin adhesive systems, was altered to produce a thiolated analogue (HETMA). Sulfur, traceable by EDS and STEM, was substituted for the oxygen atom in the backbone of the HEMA molecule. The resulting analogue, with solubility parameters and other wetting and physical properties very similar to those of HEMA, was applied to four sets of tooth specimens, each pre-treated with a different primer or etchant. Three separate pre-treatments--nitric acid, maleic acid, and citric acid/ferric chloride--created a demineralized zone approximately 1 to 3 microns thick at the dentin surface. The HETMA was found to permeate freely into this zone when either of the latter two pre-treatments was used. However, the band of dentin that was demineralized by the nitric acid pre-treatment appeared impermeable to the HETMA. The fourth pre-treatment, an alcohol-based solution including the phosphorus acid ester PENTA and HEMA, modified the smear layer of the tooth slightly and did not appear to demineralize the dentin. HETMA applied to the specimens pre-treated with PENTA and HEMA was clearly in intimate contact with the dentin or modified smear layer; however, it did not penetrate or diffuse into these areas. It did flow into the dentinal tubules, as was also evident with each of the other systems. It was concluded that the acid pre-treatment of the dentin greatly influenced the wetting behavior of the dentin adhesive and thus could substantially affect the resultant bond strength of the dentin adhesive systems.

Acid Etching, Dental↗

PubMed1995

Marginal ridge strength of Class II tunnel restorations.

PURPOSE: To test the strength, at the marginal ridge, of the tunnel preparation vs the Class II traditional box preparation when restored with composite or glass ionomer (GI). MATERIALS AND METHODS: Eighty-four extracted maxillary molars stored in normal saline and thymol were randomly divided into six groups of 14 each (determined by pilot study where alpha = 0.05, beta = 0.2). Group A and C were tunnel preparations. Group B and D were traditional Class II preparations. Group E-whole tooth (negative control), and Group F-tunnel preparation unrestored (positive control). Group A and B were restored with Scotchbond 2/P-50 composite. Group C and D were restored with Ketac Fil-GI. The marginal ridge of each tooth was loaded at 0.5 mm/minute on the Instron. A loading rod produced a contact point of 1.0 mm in diameter. RESULTS: The mean compressive loads (kg) required for fracture were: (A): 42.2 +/- 11.9, (B): 53.1 +/- 10.7, (C): 52.0 +/- 10.9, (D): 23.8 +/- 8.4. (E): 79.1 +/- 16.1, (F): 27.0 +/- 10.6. A significant difference was found between whole teeth (E) and all other groups (P < 0.05). The Newman-Keuls test showed a significant difference between Class II composite (B) and tunnel composite (A) (P < 0.05), between tunnel GI (C) and tunnel composite (A) (P < 0.05) but no difference between tunnel GI (C) and Class II composite (B).

Analysis of Variance↗

PubMed1994

Effect of esterase on methacrylates and methacrylate polymers in an enzyme simulator for biodurability and biocompatibility testing.

Current in vitro biocompatibility methods do not evaluate the degradation of biomaterials after contact with enzymes that might be present in the oral or systemic environment. In this study, two methods of in vitro enzyme degradation and a method for the separation of the degradative products by high performance thin-layer chromatography (HPTLC) are reported. In the first method two dental adhesives, Scotchbond and Scotchbond II, and two dental composites, Heliomolar and P-50, were evaluated. These materials were incubated with four different enzymatic preparations for periods of up to 72 h. The enzymes were lipase, esterase, and liver enzyme extracts from both mouse and rat. Chloroform soluble products extracted from the aqueous phase were examined by HPTLC for decomposition products resulting from enzyme activity. The second method was similar, but analyzed the aqueous fraction directly without chloroform extraction. In this method five dental restorative materials, P-50, P-30, Scotchbond II, Silux, and Silux Plus, were incubated with a nonspecific porcine liver esterase. In addition to the polymerized biomaterials, monomers containing methacrylic acid units were also hydrolyzed with esterase and analyzed by ion chromatography to establish the sensitivity of the enzyme simulator. Each biomaterial presented thin-layer zones not present before enzymatic action. These experiments provide support that aqueous enzymatic action may facilitate the hydrolytic weakening of polymeric biomaterials.

Animals↗

PubMed1994

Dentinal tubule anastomosis: a potential factor in adhesive bonding?

This study investigated adhesive tag formation within dentinal tubules and the anastomosing of lateral canals observable with scanning electron microscopy. This mechanism of micromechanical bonding had not been studied previously. The following brands of adhesives were applied to the prepared dentin surface of unerupted human third molars: Scotchbond Multipurpose, C&B Metabond, All-Bond 2, both etched and unetched, Tenure Solution, and XR-Bond. The experimental specimens were decalcified and prepared for SEM examination. Many tubule resin tags with lateral branching were observed. The resin branches were the result of primer, adhesive, or both entering lateral canals and communicating with adjacent tubules. The polymerization of adhesive in lateral canals was more prevalent with Scotchbond Multipurpose, C & B Metabond, and etched All-Bond 2 adhesives. The network of interconnected adhesive tags formed with these materials may be fundamental to the development of a stronger dentin/resin bond.

Acid Etching, Dental↗

PubMed1994

Shear strength of ceramic brackets bonded to porcelain.

The purpose of this study was to compare the bond strengths of three different adhesive systems when used alone and combined with a porcelain priming agent to bond ceramic brackets to porcelain surfaces. Sixty porcelain specimens were randomly assigned to the six different treatment groups. Half were bonded with the porcelain priming agent and one of the adhesive systems and the other half with one of the adhesive systems alone. The shear bond strengths of all specimens were tested, with an Instron testing machine, 10 minutes after being bonded. The surface of the porcelain and the bracket base were examined, with scanning electron microscopy (SEM) and qualitative energy dispersive x-ray analysis (EDS), to determine the bond failure patterns and to check the porcelain surface for the presence of cracks and fractures. There was a statistically significant difference within each adhesive between those samples with the priming agent and those without the priming agent. Differences between the three adhesives were not statistically significant (p < or = 0.05).

Acid Etching, Dental↗