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Intraocular biocompatibility of hydroxyethyl methacrylate and methacrylic acid copolymer/partially hydrolyzed poly(2-hydroxyethyl methacrylate).

A strip of partially hydrolyzed poly (2-hydroxyethyl methacrylate) containing 65%-75% H2O was implanted into the anterior eye chamber of 11 Chinchilla rabbits. No pathological changes were found in the iris or in the ciliary body. The pathological findings in the cornea accompanying implantation of a hydrogel strip to the anterior chamber were rare and not significant. The low occurrence of the foreign body giant multinucleate cells was observed on the implant surface 6 months after the implantation. Favorable properties of this hydrogel depend probably on its high water and acidic groups content.

Acrylates↗

Temperature dependence of retention in reversed-phase liquid chromatography on a porous acrylic support.

The solute retention mechanism of reversed-phase liquid chromatography is examined by using newly synthesized hydrophilic porous copolymer beads as a stationary phase. It is shown that when water is used as an eluent, the retention time for solutes such as alcohols, ketones and polyethylene glycols increases with temperature. Adsorption behaviour of polyethylene glycol onto the copolymer beads shows that the adsorption also increases with temperature. These observations are explained on the basis of the hypothesis that hydrophobic interaction plays a vital role in solute retention.

1-Propanol↗

Buccal mucosal ulcer healing effect of rhEGF/Eudispert hv hydrogel.

We have studied the effect of rhEGF on the buccal mucosal ulcer healing. rhEGF was rapidly degraded upon incubation with the hamster buccal mucosal homogenates; The degradation of rhEGF was significantly inhibited by sodium lauryl sulfate (SLS). Eudispert hv hydrogel and Polycarbophil 974P hydrogel were prepared for rhEGF delivery and their mucoadhesiveness was measured by the Instron method. The mucoadhesive force of Eudispert hv was significantly greater than that of Polycarbophil 974P. Moreover, rhEGF in Eudispert hv hydrogel remained stable for about 2 months. To evaluate the ulcer healing effect of rhEGF, the buccal mucosal ulcer was induced in golden hamsters using acetic acid. At 24 h after administration of rhEGF/Eudispert hv hydrogel, the ulcerous area was decreased compared with rhEGF solution and, as a result, the curative ratio was 36.8 +/- 5.68%. By the addition of SLS (0.5%) to Eudispert hv hydrogel, the curative ratio increased 1.5 times. The mechanism of the action was probably due to a combination of protection of the drug against proteases present in mucosa and prolongation of the release of rhEGF from the formulation at the site of action.

Acetic Acid↗

A shear test evaluation of a new, modified, unfilled resin.

A shear test was conducted under simulated oral environmental conditions to examine the retention of a new, commercially available modified unfilled resin in comparison with a conventional unfilled resin provided by the same manufacturer. Within the experimental limits of this study no difference was observed between the retention of the conventional and the modified unfilled resins to enamel specimens. However, for dentin specimens the modified resin was clearly superior to the conventional resin, which gave essentially zero retention. With the recommended procedure, the retention of the modified resin to dentin was 13% of that for the retention of either resin to enamel. It was also observed microscopically that the new resin demonstrated good wetting ability of the dentinal surface. The retention of the two resins to dentin with various surface treatments was determined. The recommended surface preparation procedures of cleaning the dentin surface with hydrogen peroxide followed by a water rinse gave equivalent, if not superior, results to a 1-minute etch with phosphoric acid or citric acid followed by a water rinse.

Acid Etching, Dental↗

Evaluation of the bond mediated by eight DBA's to enamel and dentin.

It is well-established that the bonding strength between resin and acid-etched enamel is considered clinically adequate. The tensile bonding strength mediated by a group of dentinal bonding agents (DBA's) to both dentin and acid-etched enamel was measured after one hour and the results compared. For all the DBA's tested, the bonding strength to enamel was higher than that to dentin. These differences were significant for all DBA's except for Gluma/Clearfil F-II. Analysis of variance revealed significant differences between material-specific means to either enamel or dentin. For enamel, the significant differences were due to the relatively low bonding strength value measured with the Prisma Bond. The bonding strength of all DBA's tested to acid-etched enamel would secure clinically high retention rate and adequate marginal quality. For dentin, these differences were due mainly to the high mean values for strength of bonds when the Gluma/Clearfil F-II combination was used. The low values and the large variations of the bonds to dentin measured with the commercial systems would affect the two major functions of DBA's, namely, retention of the restoration and prevention of marginal gaps. The Gluma/Clearfil combination should be recommended for clinical trials.

Acid Etching, Dental↗

Effect of operator skill in relation to microleakage of total-etch and self-etch bonding systems.

OBJECTIVES: To evaluate the influence of operator skill on microleakage in class V restorations using two-step bonding systems. METHODS: Two standardized box cavities were made on the buccal and lingual surfaces of 54 human bicuspid teeth, with the cervical margin in dentin. The teeth were randomly assigned to two groups according to the operator's skill. Students group: undergraduate students. Expert group: a dentist with 20 years of clinical experience in dental adhesion. The buccal cavities of each tooth were treated with Prime&Bond NT (two-step total-etch system); the lingual cavities were treated with AdheSE (two-step self-etch system). All cavities were restored by a single calibrated operator with one bulk increment of resin composite (InTens; Ivoclar Vivadent). Specimens were thermocycled, immersed in 2% methylene blue and sectioned in a bucco-lingual plane in the middle of the restorations. They were then examined under a stereomicroscope and scored according to microleakage by two operators who were blind to the specimen preparation. The data was subjected to a multilevel statistical model. RESULTS: The microleakage resulting from the self-etch adhesive was similar in the student and in the expert groups. On the other hand, the total-etch adhesive microleakage within the expert group resulted lower than that within the student group. However, the interaction term skill x adhesive resulted statistically significant at the dentin margin (p=0.0474) but not at the enamel margin (p=0.1267). CONCLUSION: While the total-etch adhesive used in this study showed to be skill-sensitive, the self-etch one proved to be less skill-sensitive in obtaining a reliable seal with dentin.

Acid Etching, Dental↗

Coronal microleakage of permanent lingual access restorations in endodontically treated anterior teeth.

Forty-six intact extracted human anterior teeth were treated endodontically with laterally condensed gutta-percha and sealer. The teeth were restored with a base of either zinc phosphate or temporary stopping and a permanent restoration of either acid etched composite resin with GLUMA as the dentin bonding agent or with Ketac-Fil glass ionomer. The teeth were thermocycled, coated with nail varnish (except for the access), immersed in silver nitrate, developed, and sectioned longitudinally. The linear dye penetration was measured. All restorations permitted leakage into the base. All groups had specimens which leaked into the gutta-percha. There was a tendency for the glass ionomer/zinc phosphate group to leak least, but there were no statistically significant differences among the groups.

Acid Etching, Dental↗

A laboratory study of the effect of thermocycling in saline and artificial saliva on two dentine bonding agents.

Thermocycling of composite resins in saline and artificial saliva was carried out in order to determine the effect of these solutions on the bonding of Lumifor/Gluma and Valux/Scotchbond to dentine and enamel. Minimal Class V cavities were prepared in extracted human teeth and restored with light-cured composite resins, following each manufacturer's instructions. The restored teeth were subjected to 500 cycles at temperatures ranging between 5 degrees C and 45 degrees C. One group was thermocycled in saline, the other in artificial saliva. The resultant marginal gaps were stained and evaluated microscopically. No difference was found between the respective composite resins. However, significantly more gaps were present in those restorations thermocycled in saline.

Acid Etching, Dental↗

Adsorption of zirconyl salts and their acids on hydroxyapatite: use of the salts as coupling agents to dental polymer composites.

Zirconyl methacrylate (I) and zirconyl-2-ethylhexanoate (II) were synthesized, and their adsorption isotherms from solutions onto synthetic hydroxyapatite were studied. The isotherms of methacrylic and 2-ethylhexanoic acids were also determined from the same solvents. The adsorption of I was irreversible from methylene chloride, and that of II was irreversible from cyclohexane. The adsorption in both cases was constant from solutions above a certain concentration, and exhaustive below this threshold concentration. Both compounds rendered the dried apatite powder extremely hydrophobic; however, the adsorbate was slowly washed off by excess water. The configuration of the adsorbate molecules, deduced from the maximum adsorption and other adsorption characteristics of the two compounds, indicated that: (i) in both cases the adsorbate may be held to the surface by concerted hydrogen bonding of the carboxylate and zirconyl oxygen atoms; and (ii) the hydrocarbon moieties in both adsorbates expose themselves toward the solution, thereby making the dried surface hydrophobic. The adsorptive behavior of the respective acids was similar to that of the salts. Polymer, filled with synthetic hydroxyapatite covered with irreversibly adsorbed I, had a diametral tensile strength about 50% greater than that of the polymer filled with untreated apatite. The strength of the composite was not affected by treatment of the apatite with II or with the acids.

Acids↗

Effect of thermal cycling on shear bond strength with different types of self-etching primer for bonding orthodontic brackets using a MMA-based resin.

The purpose of this study was to determine the bonding durability when orthodontic bracket was bonded to human enamel using a MMA-based resin (Multibond) with two types of commercially available self-etching primer - Multibond and Megabond. Multibond primer contained a polymerization initiator, but Megabond primer did not. No significant differences in shear bond strength were observed between Multibond and Megabond primers after immersion in water at 37 degrees C for 24 hours (before thermal cycling). Multibond primer produced no significant decrease in shear bond strength after 2000 and 5000 thermo-cycles between 5 degrees C and 55 degrees C. On the contrary, Megabond primer showed significant decrease in shear bond strength after thermal cycling. The present study suggested that if Multibond resin were to be used for bonding orthodontic brackets, difference in self-etching primer's components would influence shear bond strength after thermal cycling.

Acid Etching, Dental↗

Clinical evaluation of a polyacid-modified resin composite (Dyract AP) in Class I cavities: 3-year results.

PURPOSE: This study evaluated the 3-year clinical performance of the polyacid-modified resin composite Dyract AP in restorations for Class I carious lesions. METHODS: 108 Class I cavities in 21 subjects were restored with Dyract AP. The lesions, which were diagnosed macroscopically with a probe, involved fissures and had reached the dentin, while lateral spread was limited and localized to the dentin. The average facio-lingual width of the cavities was equal to or less than one-third the intercuspal width. Restorations were evaluated clinically by two experienced, calibrated examiners at baseline and at 1, 2, and 3 years, according to the modified Ryge criteria, (color match, marginal discoloration, wear or loss of anatomical form, caries, marginal adaptation, and surface texture). RESULTS: None of the restorations failed at the end of the first year. At 2 years, two restorations required immediate replacement due to caries lesions adjacent to the margins. At 3 years, six restorations had caries lesions adjacent to their margins, and the cumulative rate of success was 93.4%. Color changes and marginal discolorations were found to be statistically significant (P < 0.001) at 3 years, although none of the restorations needed to be replaced. Significant differences were also observed in the caries rate (P < 0.001) at 3 years. Aside from the eight failed restorations, the degrees of color matching, marginal discoloration, wear or loss of anatomical form, caries, marginal adaptation, and surface texture were clinically acceptable at 3 years post-treatment.

Acid Etching, Dental↗

Controlled release microspheres based on Eudragit L100 for the oral administration of erythromycin.

The use of Eudragit L100, a copolymer based on methacrylic acid and methacrylic acid methyl ester, in preparing erythromycin microspheres is described. The microspheres were simply prepared in liquid paraffin by solidifying an Eudragit L100 in ethanol solution. When gelatin was incorporated in the solidifying solution, the resultant microspheres were more spherical and had a smooth surface. The size of the microspheres could be controlled by varying the Eudragit L100 concentration in ethanol, and erythromycin was incorporated with 60-70% efficiency. The degradation of erythromycin by acid was markedly protected when the erythromycin microspheres were coated with the polymer. The in vitro release rate of erythromycin from the microspheres was also modified by the coating process. The feasibility of preparing formulations of erythromycin for oral administration, which release the drug at a controlled rate, and protect the drug from gastric acid, is thus demonstrated.

Acrylic Resins↗

Synthesis and application of boronic acid-immobilized porous polymer particles: a novel packing for high-performance liquid affinity chromatography.

A preparation method of a novel type of packing materials for high-performance liquid affinity chromatography to determine glycated proteins was studied, and a fundamental study on its application to diabetic serum was conducted. To quantify glycated proteins such as glycated serum albumin, a new hydrophilic and durable porous polymer particle recently developed in our laboratory was used as the basic matrix. The matrix was activated with 1,1'-carbonyldiimidazole (CDI), and optimization of the coupling reaction between these CDI-activated matrix and m-aminophenylboronic acid hemisulfate (APBA) as affinity ligand was investigated. The optimum value for the APBA coupling yield was found to be obtained under acidic conditions very different from the data reported by previous workers. Using this APBA-immobilized matrix an affinity column was prepared, and its usefulness in HPLC separation of glycated serum proteins was investigated. Also, the fundamental and preliminary results for diagnosis of diabetes mellitus are discussed in this paper.

Acrylic Resins↗

Long-term bond between dual-polymerizing cementing agents and human hard dental tissue.

OBJECTIVES: To examine the long-term adhesion of seven dual-polymerizing cementing agents to human dentin in vitro. METHODS: Two hundred and eighty extracted non-carious human molars were ground flat to expose dentin surfaces. The bond strengths of cementing agents with their respective bonding systems were examined: one compomer cement (PermaCem), five resin cements (RelyX ARC, Panavia F, Variolink II, Nexus 2, Calibra) and one self-adhesive universal resin cement (RelyX Unicem). One subgroup (n=10) was tested after 150 days of storage in water at 37 degrees C (time t(1)), the other subgroup (n=10) was tested after 150 days of storage plus 37,500 thermal cycles (time t(2)). All specimens were stressed in shear at a constant crosshead speed of 0.5mm/min until failure. Statistical analysis was performed by ANOVA, taking effect interactions into account. The Tukey method was used for multiple paired comparisons (alpha=0.05). RESULTS: The three-way ANOVA (cementing agents, polymerization methods, times of measurements) showed Variolink II to have the highest strength at 9.9+/-4.5MPa. Values were slightly higher at t(1) (5.9+/-4.7MPa) than at t(2) (4.9+/-4.2MPa) (p=0.0044). Polymerization with light activation (6.5+/-5.1MPa) yielded higher strengths than polymerization without (4.3+/-3.3MPa) (p<0.0001). Separate two-way ANOVAs for t(1) and t(2) showed that the two main effects (cementing agent, polymerization method) and their interactions differed significantly. SIGNIFICANCE: Cementing agents/adhesive systems and the polymerization method influence the long-term bond to hard dental tissues.

Acid Etching, Dental↗

Enteric-coated cholylsarcosine microgranules for the treatment of short bowel syndrome.

Cholylsarcosine (CS) is a semisynthetic bile salt that may be useful in bile salt replacement therapy of short bowel syndrome (SBS). In SBS the bile salt pool becomes depleted, disturbing the uptake of dietary lipids and resulting in weight loss. Previous studies showed that CS in a simple capsule formulation of 1.5-12 g day(-1) can increase the uptake of lipids but often results in gastric irritation. In this work a microgranule dosage form was developed to protect the gastric mucosa while facilitating rapid generation of CS levels in the duodenum. CS microgranules were produced by wet granulation and coated with Eudragit L30D-55 in a fluidized-bed coater. The in-vitro dissolution rate of CS from the microgranules was investigated with USP apparatus under fasted- and fed-state conditions. CS release was delayed under simulated gastric conditions (pH 1.2 and 4.5) but was very fast at higher pH values (5.5, 5.8 and 6.5) more typical of the duodenum. In a pilot clinical trial, four patients received 4 g CS with meals (1.5 g with lunch, 2.5 g with dinner) for 1 week. The parameters investigated were fat absorption coefficient (FAC%), serum beta-carotene level and faecal weight. Although study numbers were too small to achieve statistical significance, the serum beta-carotene level and FAC% increased in the three patients who completed the trial. As expected, the fecal weight did not change. The results indicate that the CS microgranules are promising for the treatment of the intraluminal bile salt deficiency in patients with SBS.

Adult↗

Effects of surface wetness of etched dentin on bonding durability of a total-etch adhesive system: comparison of conventional and dumbbell-shaped specimens.

The dentin bonding durability of a total-etch adhesive system (Prime & Bond NT) was investigated by tensile bond test using conventional and dumbbell-shaped specimens. Two bonding techniques were compared. After etching and rinsing, dentin surface was either blotted by cotton ball (wet-bonding) or air-dried (dry-bonding) before bonding agent was applied. The bond strength of wet-bonding specimens was significantly higher than that of dry-bonding for both conventional and dumbbell-shaped specimens after one day. The bond strength of wet-bonded conventional specimens did not decrease after two years of water immersion, but cohesive failure in demineralized dentin was observed after two years. Wet-bonded dumbbell-shaped specimens showed cohesive failure within demineralized dentin after only one day. The bond strength of dry-bonded conventional specimens decreased significantly after one year, and cohesive failure in demineralized dentin was confirmed after three months. As for dry-bonded dumbbell-shaped specimens, they showed cohesive failure in demineralized dentin after one month. The results of the present study showed that the bonding durability of dry-bonded Prime & Bond NT restorations was lower than that of wet-bonded restorations. Further, by using tensile bond test, cohesive failure in demineralized dentin was detected earlier in dumbbell-shaped specimens than in conventional specimens.

Acid Etching, Dental↗

Gluma shear bond strength to enamel and dentin treated with pyruvic acid and glycine.

The purpose of this study was to determine the effect of pyruvic acid and glycine on the shear bond strength (SBS) of the Gluma Bonding System to dentin and enamel. Forty-five mandibular and maxillary permanent first and second molars and 45 maxillary permanent central incisors were used in the study. Fifteen test specimens were prepared with each of the following procedures. Dentin: using the conventional Gluma Bonding System (A); the Gluma 2 Cleanser was replaced with 10% pyruvic acid containing 10% glycine with pH 2.8 (B); or the dentin was etched with 10% pyruvic acid (pH 1.5) followed by the application of 10% glycine with pH adjusted to 9.0 (C). Enamel: etched with Gluma 1 Etchant (D); etched with 10% pyruvic acid containing 10% glycine (E); or etched with 10% pyruvic acid followed by the application of 10% glycine (F). The test specimens were disassembled 15 minutes after cure, stored in physiological saline at 37 degrees C for 24 hours, and the SBS determined in an Instron machine at a crosshead speed of 0.5 mm.min.-1 The SBS was expressed in MPa. The data were analyzed by ANOVA and the Student-Newman-Keuls test. The mean +/- SD of the SBS in MPa were: A: 8.7 +/- 5.2; B: 14.7 +/- 4.6; C: 12.8 +/- 4.8; D: 19.8 +/- 3.8; E: 18.0 +/- 3.1; F: 17.6 +/- 3.5. The application of 10% pyruvic acid containing 10% glycine, and 10% pyruvic acid followed by 10% glycine, resulted in a significant increase in SBS to dentin. The SBS to enamel treated with the three procedures were not significantly different.

Acid Etching, Dental↗