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PubMed1991

Interactions of copolymeric poly(glyceryl methacrylate)-collagen hydrogels with neural tissue: effects of structure and polar groups.

In a previous study we developed copolymeric glyceryl methacrylate-collagen hydrogels for implantation in surgical lesions of the rat brain. Such materials provide porous matrices that can serve as support systems for oriented growth of scar tissue and axonal growth. In the present work, we have investigated the effect of structural modifications (studied by mercury porosimetry) of polymeric matrices and the effect of polar groups on the response of the brain tissue. The findings show that the fractional porosity and the pore size distribution of matrices are critical for tissue ingrowth and that negative charges, i.e. carboxylic acid groups, incorporated in the polymer have a strong influence on reactive astrocytosis.

Animals↗
PubMed2004

Hydrogen-bonding-driven spontaneous gelation of water-soluble phospholipid polymers in aqueous medium.

It has been found that mixing of two kinds of water-soluble phospholipids polymers, such as poly(2-methacryloyloxyethyl phosphorylcholine-co-methacrylic acid) (PMA) and poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB), spontaneously forms a hydrogel in aqueous medium at room temperature without any chemical treatment. However, the mechanism of spontaneous gelation has not been clarified yet. The purpose of this study is to investigate the gelation mechanism of the hydrogel. Moreover, effects of ions on gelation and dissolution behavior were observed. We investigated the mechanism of the hydrogel formation by spectroscopic techniques and a rheological method with attention to the interactions between polymer chains. Both Raman spectroscopic analysis and FT-IR analysis revealed that carboxyl groups in methacrylic acid (MA) formed dimer when two polymer solutions were mixed, and the results of the rheological study showed dissociation of carboxyl groups caused dissolution of the hydrogel. Thus, the gelation occurred due to the formation of dimers by hydrogen bonding which acts as a physical cross-linking of polymer chains. The hydrogel dissolved in a large amount of aqueous medium. We also observed the addition of inorganic salts during the preparation of the hydrogel affected the gelation and dissolution behaviors by a rheological and a weight measuring method, respectively. The gelation period became longer in the presence of NaCl and CaCl2 compared with that in the absence of these salts. NaCl and CaCl2 disturbed the formation of hydrogen bonding between carboxyl groups by stabilization of carboxylate anion of the MA units. On the other hand, addition of FeCl3 made the gelation period shorter and stabilized the hydrogel in the aqueous medium. This is because FeCl3 can suppress dissociation of the carboxyl groups by acidic condition of FeCl3 aqueous solution and cross-link the carboxylate anions in the PMA effectively.

Calcium Chloride↗
PubMed2006

Long-term TEM analysis of the nanoleakage patterns in resin-dentin interfaces produced by different bonding strategies.

OBJECTIVES: The aim of this study was to evaluate the ability of etch-and-rinse and self-etching adhesive systems to prevent time- and water-induced nanoleakage in resin-dentin interfaces over a 6-month storage period. METHODS: Five commercial adhesives were tested, which comprise three different strategies of bonding resins to tooth hard tissues: one single-step self-etching adhesive (One-up Bond F (OB), Tokuyama); two two-step self-etching primers (Clearfil SE Bond (SE) and an antibacterial fluoride-containing system, Clearfil Protect Bond (CP), Kuraray Inc.); two two-step etch-and-rinse adhesives (Single Bond (SB), 3M ESPE and Prime&Bond NT (PB), Dentsply). Restored teeth were sectioned into 0.9 mm thick slabs and stored in water or mineral oil for 24 h, 3 or 6 months. A silver tracer solution was used to reveal nanometer-sized water-filled spaces and changes that occurred over time within resin-dentin interfaces. Characterization of interfaces was performed with the TEM. RESULTS: The two two-step self-etching primers showed little silver uptake during the 6-month experiment. Etch-and-rinse adhesives exhibited silver deposits predominantly within the hybrid layer (HL), which significantly increased for SB after water-storage. The one-step self-etching adhesive OB presented massive silver accumulation within the HL and water-trees protruding into the adhesive layer, which increased in size and quantity after water-storage. After storage in oil, reduced silver deposition was observed at the interfaces for all groups. SIGNIFICANCE: Different levels of water-induced nanoleakage were observed for the different bonding strategies. The two-step self-etching primers, especially the antibacterial fluoride-containing system CP, showed the least nanoleakage after 6 months of storage in water.

Acid Etching, Dental↗
PubMed1995

Coated oral 5-aminosalicylic acid (Claversal) is equivalent to sulfasalazine for remission maintenance in ulcerative colitis. A double-blind study.

In a double-blind, single-center, 1-year prospective trial, we compared a pH-dependent Eudragit L-coated formulation of oral 5-aminosalicylic acid (5-ASA) (Claversal), 0.5 g b.i.d., and sulfasalazine (SASP), 1 g b.i.d., in the prophylactic treatment of quiescent ulcerative colitis. Forty-four patients received 5-ASA and 44 received SASP. Clinical, sigmoidoscopic, and histologic findings were assessed at 6 and 12 months. The two groups were comparable in all pretrial characteristics. No significant difference was observed in the relapse rate in the two groups either after 6 months [5-ASA 20.5%, SASP 27.5%, p = 0.32, 95% confidence interval (CI) 0.28 +/- 0.13] or after 12 months (5-ASA 38.4%, SASP 51%, p = 0.18, 95% CI 0.38 +/- 0.1). We conclude that (a) 5-ASA was as effective as SASP in maintaining remission of ulcerative colitis; (b) the relapse rate was, however, higher than expected in both groups; (c) the incidence of side effects was similar with both treatments.

Acrylic Resins↗
PubMed2005

Clinical performance of a non-rinse conditioning sealant in three paediatric dental practices: a retrospective study.

The present clinical retrospective study describes the retention rates of a compomer sealant (Dyract Seal, Dentsply-De Trey, Germany) with non-rinse conditioning (NRC) placed in three paediatric dentistry practices. Three hundred and seventeen sealants were applied in 220 primary and 97 permanent molars of 176 children aged 2.5-13 years. The tooth surface was freshened with a #1/2 round bur mounted on a slow speed engine, and isolated with cotton rolls. Application of the NRC and Dyract Seal followed the manufacturer's instructions. Sealant retention was classified as A (fully retained), B (partially lost) or C (completely missing). From a total of 220 sealants placed in primary molars, 38 were in the mouth between 12 and 18 months, 29 functioned between 19 and 24 months and 46 were followed up between 25 and 36 months. One hundred and thirteen (51%) were fully retained (A), 73 (33%) scored B (27 for 12-18 months; 20 for 19-24 months, 26 for 25-36 months) and 34 (16%) were lost and scored C (12 for 12-18 months; 12 for 19-24 months; 10 for 25-36 months). From a total of 97 sealed permanent molars, 45 (46%) were fully retained (score A). Of these, 25 were followed up for 12-18 months, 10 for 19-24 months and 10 for 25-36 months. Thirty-eight sealed permanent molars (19%) scored B [17 for 12-18 months, 10 for 19-24 months and seven for 25-36 months and 14 (15%) were completely lost (score C: 6 for 12-18 months, seven for 19-24 months and two for 25-36 months)]. Dyract Seal has a lower retention rate than conventional sealants. It may be appropriate for sealing primary molars of very young children for a limited period of time and for permanent molars of children with pronounced gag reflex, where rinsing can become a problem and lead to disruptive behaviour.

Acid Etching, Dental↗
PubMed2001

Colonic delivery of sodium butyrate via oral route: acrylic coating design of pellets and in vivo evaluation in rats.

Few pharmaceutical studies, with the exception of those on rectal solutions, are described on short chain fatty acid (SCFA) formulations-especially for sodium butyrate, which is a colonocyte preferential substrate. Highly dosed butyrate pellets (90%) were prepared and their coating was designed for colonic delivery. In vivo determination (pH and transit time of pellets in rats) allowed to respectively choose the grade and thickness (resistance of 6 h) of the pH-dependent coating (Eudragi L+S, 1:1). The coated pellets were administered to naturally butyrate-deprived rats. The rats' colonic mucosa had the particularity to weakly express mitochondrial HMG-CoA synthase, an enzyme that responds to luminal butyrate. The results did not show early absorption of butyrate, but a probable cecal loss in the rat cecum as cecal residence time of the pellets was important and as pH was propitious for the coating hydrolysis. It seemed that butyrate, given daily for 7 days without the other main SCFA. was unable to induce the enzyme and/or that the dose (0.32 mmol/day) was insufficient.

Administration, Oral↗
PubMed2004

Efficacy of a self-etching dentin primer composed of TEGMA and phenyl-P.

The purpose of the present study was to evaluate the efficacy of an experimental self-etching dentin primer composed of TEGMA and phenyl-P using primary and young permanent teeth. The efficacy of the self-etching dentin primer was evaluated by measuring the wall-to-wall polymerization contraction gap width and the shear bond strength to the flat dentin surface. The contraction gap formation was prevented completely in the specimens primed with the 35 vol% TEGMA and 20% phenyl-P for 30 sec.

Acid Etching, Dental↗
PubMed2004

Micro-tensile bond strength of adhesive systems applied on occlusal primary enamel.

The aim of this study was to evaluate the micro-tensile bond strength of adhesive systems (OptiBond Solo, Kerr; Prime & Bond NT, Dentsply) on occlusal surface of primary molars. The adhesives were tested under manufacturers' specifications and after contamination of the bonding site with saliva. Hourglass cylindrical-shaped samples were obtained and subjected to a tensile force. No significant difference was observed among the groups. OptiBond Solo and Prime & Bond NT showed similar values of bond strengths when applied on occlusal enamel of primary molar under either saliva contamination or not.

Acid Etching, Dental↗
PubMed2004

Bonding durability between orthodontic brackets and human enamel treated with megabond self-etching primer using 4-META/MMA-TBB resin cement.

The purpose of this study was to determine the bonding durability when a Megabond self-etching primer is used with 4-META/MMA-TBB resin to bond metal orthodontic brackets to human premolar enamel. Three conditions of enamel were prepared: Megabond self-etching primer without saliva contamination, Megabond self-etching primer with saliva contamination, and repeat Megabond self-etching priming after saliva contamination. Shear bond strengths were measured after immersion in water at 37 degrees C for 24 hours, or after 2000 or 5000 cycles of thermal cycling between 5 degrees C and 55 degrees C. There were no significant differences in shear bond strength among the three groups not only before thermal cycling, but also after thermal cycling. FE-SEM observation revealed the presence of saliva and reduced amount of resin tag formation after saliva contamination. The present study provided the evidence in human teeth that when using 4-META/MMA-TBB resin, Megabond self-etching primer treatment produced tight bonding even when surface was contaminated with saliva.

Acid Etching, Dental↗
PubMed1999

Fracture strength of intact and fragment-bonded teeth at various velocities of the applied force.

Bonding of a tooth fragment to the remaining tooth substance can restore crown fracture of an anterior tooth. In this study, sheep central incisors were used. The crowns were fractured transversely and the crown fragment was bonded to the remaining tooth structure. This technique involves acid etching, use of an experimental adhesive (Gluma+) and a BisGMA/TEGDMA resin. The mean fracture strength of the restored teeth was not significantly different from that of intact teeth when tested at a rather low crosshead speed (0.5 mm/min) but different and about 30% lower when tested at a higher crosshead speed (500 mm/min). In studies aiming to test resistance to forces which might cause trauma, it might be appropriate to use a high crosshead speed.

Acid Etching, Dental↗
PubMed1999

Standardized microscopic evaluation of the bonding mechanism of NRC/Prime & Bond NT.

PURPOSE: To investigate the in vitro formation of hybrid layer, resin tags and adhesive lateral branches, when using Prime & Bond NT (PBNT) "one-bottle" enamel-dentin bonding system on conditioned and unconditioned human dental substrates. MATERIALS AND METHODS: The enamel dentin adhesive was tested on 18 dentin and 18 enamel flat preparations made on facial and occlusal surfaces, respectively, of extracted posterior teeth. Each experimental tooth substrates were randomly divided in six groups of six samples each: Group 1: PBNT on conditioned dentin (CD) with 36% phosphoric acid (PA), Group 2: PBNT on etched enamel (EE) with 36% PA, Group 3: PBNT on CD with NRC non-rinse conditioning (NRC); Group 4: PBNT on EE with NRC, Group 5: PBNT on dentin without any conditioning (UD), Group 6: PBNT on enamel without any conditioning (UE). In the experimental groups, PBNT was applied following the manufacturer's instructions. Over the PBNT, a layer of Dyract AP was placed and light-cured for 20 seconds. All samples were split-fractured along their long axis. One half of each sample was deproteinized and decalcified at the interface in order to visualize the hybrid layer and the other was completely dissolved in order to observe the morphology of resin tags with a scanning electron microscope. RESULTS: Groups 1, 2: The tested samples showed a micromechanical bonding mechanism to CD and EE with phosphoric acid. PBNT formed hybrid layer, resin tags and adhesive lateral branches on dentin. In the dentin samples of the first group, characteristic reverse cone-shaped tags with their corresponding adhesive lateral branches were evident. At the enamel site, traditional pattern of etch enamel was always observed with resin tags formation. Groups 3, 4: When the bonding system was applied on dentin conditioned with NRC, a thin hybrid layer was formed, resin tags were also noted but their shape was narrower than that observed in Group 1. At the enamel site, the conditioned surface showed presence of an etched pattern and of resin tags. Groups 5, 6: When PBNT was applied without any previous conditioning, the hybrid layer and resin tags formation were not evident on dentin, and no bonding mechanism was developed with unetched enamel.

Acid Etching, Dental↗
PubMedDate not supplied

Thickness and morphology of resin-infiltrated dentin layer in young, old, and sclerotic dentin.

The purpose of the present study was to evaluate the morphology of the resin tags and the resin-infiltrated dentin layer (RIDL) of several bonding systems in superficial vs deep young, old, and sclerotic human dentin. Dentin was obtained after the removal of occlusal enamel from extracted molars. Phosphoric acid gels (35-37%) were used to etch dentin before the application of bonding systems (OptiBond FL; Prime & Bond 2.0; Scotchbond Multi-Purpose Plus and Scotchbond 1; One Step). Each bonded specimen was then sectioned into two halves. One half was polished using a standard procedure to evaluate RIDL thickness and morphology by SEM. The other half was demineralized and deproteinized to evaluate the presence and the morphology of resin tags. RIDL was thinner in superficial dentin than in deeper dentin for all the materials tested regardless of the type of dentin. Sclerotic and old dentin showed thinner RIDL, with short resin tags, and fewer lateral branches than normal dentin.

Acid Etching, Dental↗
PubMed1999

Effect of saliva contamination on micromorphological adaptation of single-bottle adhesives to etched enamel.

This study explored the topography of the interface of composite resin bonded with four single-bottle adhesives and enamel under salivary contaminated conditions. Prime & Bond 2.1, One Step, Tenure Quik and Syntac Single Component were evaluated. Thirty six sound molars were divided into three subgroups for each of the four adhesives. Small flat areas on the buccal and lingual surface were wet ground in enamel. The adhesives were tested under: uncontaminated condition (Group 1), contamination of the bonding site with fresh whole saliva for 20 seconds (Group 2) and rinsing the saliva for 20 seconds before adhesive application and after enamel etching (Group 3). After adhesive application button of composite resin was applied and light cured. The roots of the teeth were removed and the crowns with the bonded composite immersed in HCl acid till the composite resin buttons become free of enamel. The buttons were immersed in NaC10(4) and prepared for SEM examination. The bonding surface of the composite resin buttons revealed the formation of resin tags reflecting the different etching pattern of enamel. Saliva contamination either washed or unwashed did not affected the resin tags formation except for Syntac Single Component with contaminated unwashed enamel. The clinical significance of this in vitro research was that saliva contamination did not affect the resin tags formation of Prime & Bond 2.1, One Step, and Tenure Quick. For Syntac Single Component, only contaminated unwashed enamel decreased resin tags formation.

Acid Etching, Dental↗
PubMed1999

Distribution of nanofillers from a simplified-step adhesive in acid-conditioned dentin.

PURPOSE: This in vitro study examined the interfacial ultrastructure of a nanofilled, simplified-step adhesive (Prime & Bond NT, Dentsply), to determine the distribution of nanofillers within the collagen network of the hybrid layer. MATERIALS AND METHODS: Twenty-four dentin discs were divided into two groups and bonded using two recommended conditioning techniques: Group I, NRC (Non-Rinse Conditioner), and Group II, Conditioner 36 (colloidal silica thickened 36% phosphoric acid). Following conditioning, a single coat of adhesive was applied and light-cured. Dentin discs were then bonded to form disc-pairs and processed for TEM examination. Demineralized, ultrathin sections were examined stained or unstained. Non-demineralized sections were used for STEM/EDX analysis of elemental distribution across the resin-dentin interface. In addition, four dentin discs were bonded with a generic adhesive (HEMA/TBBO) for TEM examination of stained collagen and proteoglycans. RESULTS: In unstained sections of both groups, nanofillers from the adhesive layer were congested around patent tubular orifices, but were not found within the interfibrillar spaces of the hybrid layer. EDX analysis of silicon (Si) showed predominant distribution within the adhesive layer and tubular orifices. Phosphorus (P) was present within the hybrid layer and adhesive layer in Group II. CONCLUSION: It is hypothesized that a) aggregation of the nanofillers within the adhesive resulted in filler clusters that are too large to infiltrate the interfibrillar spaces of the hybrid layer; and b) retention of ground substance within the demineralized intertubular collagen matrix may also have prevented the infiltration of the nanofillers.

Acid Etching, Dental↗
PubMed2002

The nanoleakage phenomenon: influence of moist vs dry bonding.

PURPOSE: To assess the degree of nanoleakage of Class V preparations restored with three bonding agents using wet and dry bonding. MATERIALS AND METHODS: Standardized Class V cavities were prepared in 66 human molars with cervical margins located in dentin. The composite was placed using one of three different dentin bonding agents with a moist or dry bonding technique (n = 11 per group). The teeth were stored in a 1% rhodamin-B solution for 24 h at 20 degrees C, then rinsed with water, embedded in methacrylate, and sectioned parallel to the long axis of the tooth, separating the restorations into two parts. A confocal laser scanning microscope (CLSM) was used to visualize the layer 10 microm under the prepared surface of the section. The lengths of the dye-penetrated pathways were measured, representing the amount of nanoleakage. RESULTS: Differences in nanoleakage between the tested materials were proven to be statistically significant. The effect of drying had a significant influence on both the acetone-based and the ethanol-based material, but not on the water-based bonding resin. CONCLUSION: Dentin drying may have an influence on nanoleakage, depending upon the nature of the individual bonding agent.

Acetone↗
PubMedDate not supplied

Immunohistochemical analysis of collagen fibrils within the hybrid layer: a FEISEM study.

This study evaluated the immunohistochemical labeling pattern of dentin collagen fibrils within hybrid layers created by different bonding systems using high resolution SEM. Four different adhesive materials, including self-etching and total-etching systems, were examined: Prime & Bond NT, OptiBond SOLO Plus, Single Bond and Clearfil Protect Bond. All materials were applied to the dentin of extracted human third molars. After cutting the bonded specimens transversely, an anti-collagen type I antibody was incubated on the surface of the dentin-adhesive interface and gold-conjugated secondary antibody was applied to reveal collagen labeling under high resolution SEM. The hybrid layers showed a significant number of collagen fibrils embedded in the resin matrix. The presence of exposed dentin collagen fibrils, as determined by positive labeling with an anti-type I collagen monoclonal antibody, is considered an indication of the presence of incompletely embedded fibrils and, thus, the quality of dentin matrix hybridization. The hybrid layers produced by total-etching systems showed higher labeling compared to those produced by the self-etching system. Positive collagen labeling was also found along the resin tags produced by total-etching adhesive systems.

Acid Etching, Dental↗
PubMed2005

Effects of Nd: YAG laser irradiation on the adaptation of composite resins to root dentin.

One of the most important goals of the restoration of endodontically treated teeth with a composite resin post system is to achieve good adaptation of the composite material to dentin walls to prevent microleakage apically and coronally. In post core systems, to avoid microleakage between the dentin wall and resin material, laser irradiation may seem to be an alternative therapy for increasing adaptation quality. The aim of this study was to investigate the adaptation of a packable composite resin to lased root canal dentin when it was used as post material. Forty-five freshly extracted human teeth were selected and post spaces were prepared. The teeth were divided into three groups. In group 1 the dentin of the post spaces were etched with 35% phosphoric acid, in group 2 the dentin surfaces were irradiated with an Nd: YAG laser, and in group 3 the dentin surfaces were initially treated with the laser and then etched. The teeth of all groups were obturated with a bonding agent and composite. The groups were divided into two subgroups: a group for the scanning electron microscope (SEM) study and a group for the microleakage study. The lased group showed poor adaptation and more microleakage was detected (p<0.05; variance analysis). The laser beam and acid-etching showed no advantage compared to the acid-etching alone (p>0.05). The Nd: YAG laser irradiation adversely affects adhesion to dentin for using composite resin as a post material and does not constitute an alternative to acid-etching.

Composite Resins↗