Ground Enamel Research Articles

Adhesion of composite resins to enamel irradiated by the Er:YAG laser: application of the ultrasonic scaler on irradiated surface.

The clinical use of the Er:YAG laser in cavity preparation has become widespread. With respect to cavities prepared with the Er:YAG laser, restorations using composite resins and glass ionomer cements are common. The bond strength of current resin bonding systems to ground enamel is 14-30 MPa, whereas the strength to Er:YAG laser-irradiated enamel, regardless of the use or non-use of phosphoric acid etching is less than 10 MPa. In this investigation, an ultrasonic scaler was tested as a technique to increase the bond strength of composite resins to the Er:YAG irradiated enamel surface. The application of the ultrasonic scaler significantly increased bond strength. The tensile bond strength in the groups treated with the ultrasonic scaler exhibited approximately twice the strength observed in groups treated with laser irradiation alone.

ISS protocol for EPR tooth dosimetry

The accuracy in Electron Paramagneetic Resonance (EPR) dose reconstruction with tooth enamel is affected by sample preparation, dosimetric signal amplitude evaluation and unknown dose estimate. Worldwide efforts in the field of EPR dose reconstruction with tooth enamel are focused on the optimization of the three mentioned steps in dose assessment. In the present work, the protocol implemented at ISS in the framework of the European Community Nuclear Fission Safety project “Dose Reconstruction” is presented. A combined mechanical–chemical procedure for ground enamel sample preparation is used. The signal intensity evaluation is carried out with powder spectra simulation program. Finally, the unknown dose is evaluated individually for each sample with the additive dose method. The unknown dose is obtained by subtracting a mean native dose from the back-extrapolated dose. As an example of the capability of the ISS protocol in unknown dose evaluation, the results obtained in the framework of the 2nd International Intercomparison on EPR tooth enamel dosimetry are reported.

Effects of pH and concentration of citric, malic and lactic acids on enamel, in vitro

Objective: Dental erosion associated with soft drink consumption probably results from the contained dietary acids in the formulations. The pH value of any formulation is an important variable in acid erosion but not necessarily the only important factor. The aim of this study was to measure enamel erosion by citric, malic and lactic acids at pH values and acid concentrations representative of a range found in soft drink formulations and to determine the effect of adding calcium to citric acid.Methods: Flat ground enamel samples were prepared from unerupted human third molar teeth. Groups of five specimens were placed in citric, malic and lactic acid solutions of different pH and acid concentration for three by 10min exposures at 35°C. Enamel loss was measured by profilometry. Enamel specimens were also exposed to citric acid solutions containing calcium at different pH values and at the same pH with different concentrations of calcium.Results: Numerical data and contour plots for each acid showed a similar pattern for increasing erosion with decreasing pH and increasing acid concentration and vice versa for decreasing erosion. Increasing the concentration of calcium in a fixed pH citric acid solution resulted in decreased erosion. This effect was most marked at higher pH.Conclusions: This study has shown that under highly controlled conditions the erosion of enamel by solutions of dietary acids is influenced by the interplay of pH, acid concentration and presence of calcium. These variables and in particular the concentration of calcium could be manipulated to produce soft drinks with reduced erosivity to enamel.

In vitro permeability and scanning electron microscopy study of acid-etched and ground enamel surfaces protected with dental adhesive coating.

Clinical procedures, such as acid etching and reshaping of the teeth supporting removable partial dentures by grinding off some enamel surface, increase the permeability of dental enamel. Teeth take several months in vivo to partially recover from such damage. In the meantime, the tooth is more susceptible to carious decay. To prevent this the ground or etched enamel should be effectively protected. Using electron paramagnetic resonance (EPR) and a two-chamber diffusion cell the authors studied the influence of adhesive resin applied to the ground and acid-etched enamel surfaces on the diffusion of spin label TMAPO (2,2,6-6 tetramethyl-4-acetamido-piperidine-1-oxyl) molecules through the enamel. The enamel permeability was measured in samples exposed to 1-min etching with 37% phosphoric acid, in samples etched for 5 min, and in samples ground with a diamond bur. Next, all the treated enamel surfaces were coated with Scotchbond Multi-Purpose Plus(R) dental adhesive system and the permeability measurements repeated. Scanning electron microscopy (SEM) was used to study the porosity of enamel surfaces. The adhesive resin film covering the etched or ground enamel surfaces was found to decrease significantly the diffusion through dental enamel. This finding confirms the clinical value of dental adhesives used to protect ground or accidentally acid-etched enamel surfaces. SEM analysis showed that adhesive resin covers the porous surface of the acid-etched and ground enamel tightly.

Tensile bond strength to and SEM evaluation of ground and intact enamel surfaces

Objectives: The aim of this study was to evaluate the bonding of four commercially available adhesive systems to ground and intact enamel surfaces. Methods: Extracted human teeth were used to measure the microtensile bond strength to enamel and a field-emission scanning electron microscopy (FE-SEM) was used to observe the bonded interface and the effect of the surface conditioning of each material. Intact buccal enamel surfaces were cleansed with tooth paste using a rotary dental brush, and the ground enamel surfaces were prepared by reducing approximately 0.5 mm from the buccal enamel surfaces using a high-speed diamond bur. One-Step (OS, Bisco), Single Bond (SB, 3M), Clearfil Liner Bond II (LBII, Kuraray), and Tokuso Mac Bond II (MBII, Tokuso) were evaluated for their ability to bond to enamel. Results: There was no significant difference in bond strengths between the materials when they were applied to ground enamel surfaces ( p>0.05). However, the bond strengths of the self-etching systems, LBII and MBII, had significantly lower bond strengths to intact enamel than the bonding systems OS and SB using phosphoric acid etching ( p<0.05). FE-SEM revealed that the etching pattern of self-etching primers was not deep enough to obtain good penetration of bonding resin when applied to intact enamel surfaces. Conclusions: Phosphoric acid etching produced good resin adhesion to ground and intact enamel. The self-etching/self-priming systems also produced good adhesion to ground enamel, but had lower bond strengths to intact enamel.

The effect of etching time with Gluma 2000 conditioning solution on shear bond strength of a composite resin and on micromorphology of the enamel

The purpose of this study was to assess the effect of etching time with Gluma 2000 conditioning agent on, first, the shear bond strength of composite resin to tooth enamel and, secondly, the micromorphology of the enamel. In the first part of the study flat enamel surfaces were prepared with 600-grit silicon carbide paper on 40 primary and 40 permanent teeth. Ten specimens of each group were etched for 15, 30, 60 or 120 seconds before applying bonding resin and restorative composite resin. After 24 hours' storage in water, the shear bond strength of each specimen was tested. Analysis of variance indicated a significant difference between the eight groups. However, the Student-Newman-Keuls test indicated that the only differences that were significant were the greater bond strengths of the 15-second primary tooth specimens compared with the 15- and 30-second permanent tooth specimens. In most cases the debonded specimens showed cohesive failure in resin close to the coupling interface. In the second part of the study the morphology of the enamel etching patterns in 96 other teeth was studied by scanning electron microscopy. The patterns were similar in primary and permanent teeth, and the longer the etching time the more pronounced was the pattern. The patterns produced in ground enamel were more uniform and predictable than those in pumiced enamel. Examination of bonded resin surfaces after dissolution of the teeth showed complete reproduction of the etched enamel surfaces, indicating excellent flow of the resin into the etched enamel.

Brushing-lnduced Effects with and without a Non-Fluoride Abrasive Dentifrice on Remineralization of Enamel Surfaces Etched with Phosphoric Acid

The remineralization of acid-etched enamel after brushing with and without a non-fluoride abrasive dentifrice was investigated using scanning electron microscopy after sodium hypochlorite (NaOCl) or ethylenediamine tetra-acetic acid treatment, of the specimens. Ground enamel pieces were etched with 30% phosphoric acid for 60 s and attached to resin plates. They were exposed to the oral environment of 4 subjects for 8 weeks and brushed for 1 min daily. Paste and brushing caused the acid-etched enamel to erode selectively, i.e., deep grooves were formed in the prism peripheral regions, while projections of the prism bodies showing a relatively low density of crystallites were retained. Brushing without dentifrice, on the other hand, caused about 0.5 micron thick pellicle with tag-like structures to cover the etched enamel. Fine mineral granules, presumably derived from saliva and minute fragments of etched crystallites, were precipitated on the enamel surface as a thin layer with the pellicle. These results indicate that daily brushing without dentifrice induces the remineralization of acid-etched enamel by depositing salivary components, while paste brushing will lead to abrasion of the weakened enamel.

Resin Adhesion on the Primary Ground Enamel Report 6 Influence of the Light-Irradiation Times on the Bonding Agent

Resin Adhesion on the Primary Ground Enamel Report 6 Influence of the Light-Irradiation Times on the Bonding Agent

Microstructural Changes of Human Enamel Surfaces by Brushing with and without Dentifrice Containing Abrasive

Toothbrushing with and without dentifrice containing abrasive was performed on human enamel pieces attached to resin plates exposed to the oral cavities of 3 human subjects for 8 weeks. The effects on the ground enamel surfaces with engraved scratches were examined by scanning electron and scanning laser microscopy. Brushing with such a dentifrice caused smaller scratches to disappear, large scratches to expand and new microwear to appear; in some samples, prism structures were exposed. Under brushing without dentifrice, these scratches were protected by an organic pellicle with mineral deposits, and also the experimental surface was entirely covered with these membranous deposits. The results indicate that toothbrushing with no dentifrice but saliva induces an organic-mineral protective membrane on the enamel surface. The membrane may increase the enamel resistance to caries. On the other hand, the use of abrasive-containing dentifrice causes slight abrasion with microwear. This roughness may contribute to the formation of dental plaque.

Resin Adhesion on the Primary Ground Enamel

Resin Adhesion on the Primary Ground Enamel

Resin Adhesion on the Primary Ground Enamel (Report 3)

Resin Adhesion on the Primary Ground Enamel (Report 3)

Preliminary Surface Analysis of Etched, Bleached, and Normal Bovine Enamel

X-ray photoelectron spectroscopic (XPS) and secondary ion-mass spectroscopic (SIMS) analyses were performed on unground un-pumiced, unground pumiced, and ground labial enamel surfaces of young bovine incisors exposed to four different treatments: (1) immersion in 35% H2O2 for 60 min; (2) immersion in 37% H3PO4 for 60 s; (3) immersion in 35% H2O2 for 60 min, in distilled water for two min, and in 37% H3PO4 for 60 s; (4) immersion in 37% H3PO4 for 60 s, in distilled water for two min, and in 35% H2O2 for 60 min. Untreated unground un-pumiced, unground pumiced, and ground enamel surfaces, as well as synthetic hydroxyapatite surfaces, served as controls for intra-tooth evaluations of the effects of different treatments. The analyses indicated that exposure to 35% H2O2 alone, besides increasing the nitrogen content, produced no other significant change in the elemental composition of any of the enamel surfaces investigated. Exposure to 37% H3PO4, however, produced a marked decrease in calcium (Ca) and phosphorus (P) concentrations and an increase in carbon (C) and nitrogen (N) concentrations in unground un-pumiced specimens only, and a decrease in C concentration in ground specimens. These results suggest that the reported decrease in the adhesive bond strength of resin to 35% H2O2-treated enamel is not caused by a change in the elemental composition of treated enamel surfaces. They also suggest that an organic-rich layer, unaffected by acid-etching, may be present on the unground un-pumiced surface of young bovine incisors. This layer can be removed by thorough pumicing or by grinding. An awareness of its presence is important when young bovine teeth are used in a model system for evaluation of resin adhesiveness.

Effects of phosphoric acid concentration and etch duration on enamel depth of etch: An in vitro study

In a previous study we reported no significant differences among the shear bond strengths resulting from the application of an orthodontic bonding resin to enamel surfaces etched with three phosphoric acid (H3PO4) concentrations, each for three etch durations. The objective of the current study was to determine the depths of etch on ground enamel surfaces exposed to the nine etching procedures. The facial surfaces of 45 extracted human maxillary permanent central incisors were ground wet on 600-grit silicon carbide paper. Annular adhesive disks of 6 mm outer diameter and 3 mm inner diameter were positioned on the ground enamel surfaces and etched with 10 mm3 of 37%, 15%, and 5% H3PO4 for 60, 30, and 15 seconds, respectively. The calcium concentrations of the etching solutions were determined and the depths of etch calculated. The depths of etch were then measured with a surface profilometer. A stepwise decrease in the calculated depths of etch with decreasing acid concentration and duration of etching was obtained. The calculated etch depths ranged from 27.1 microns by etching with 37% H3PO4 for 60 seconds to 3.5 microns by etching with 5% H3PO4 for 15 seconds. The measured depths of etch followed a similar pattern. A highly significant correlation between calculated and measured depths of etch was obtained.

Resin Adhesion on the Primary Ground Enamel (Report 1)

Resin Adhesion on the Primary Ground Enamel (Report 1)

Resin Adhesion to the Ground Enamel

Resin Adhesion to the Ground Enamel

Resin Adhesion on the Primary Ground Enamel (Report 2)

Resin Adhesion on the Primary Ground Enamel (Report 2)

Effects of phosphoric acid concentration and etch duration on the shear bond strength of an orthodontic bonding resin to enamel: An in vitro study

The purpose of this in vitro study was to determine the effects of phosphoric acid (H 3PO 4) concentration and duration of etching on the shear bond strength of an orthodontic bonding resin to enamel. Nine bonding procedures, each involving 18 extracted human maxillary permanent canines, were used. Ground enamel surfaces were etched with a 37% H 3PO 4 solution, a 15% H 3PO 4 gel, or a 5% H 3PO 4 solution for 60, 30, and 15 seconds, respectively. Cylinders of an orthodontic bonding resin, Concise, were prepared in a special device. The test specimens were disassembled 15 minutes after preparation and stored in distilled water at 37°C for 24 hours. A shear load was applied to the bonded cylinders at a crosshead speed of 0.02 in·min −1 in an Instron testing machine, and the shear bond strengths were calculated and expressed in MN·m −2. A two-factor analysis of the data showed that the H 3PO 4 concentration had no significant effect on the shear bond strength, but the duration of etching affected shear bond strength significantly. The enamel aspects of the fractured test specimens were examined microscopically and the percent failure within the bonding resin at the bonding sites estimated. The correlation between shear bond strength and percentage failure within the bonding resin was not significant. The effects of the nine etching procedures on ground and unground enamel surfaces were studied by scanning electron microscopy. The etching procedures produced well-defined etching patterns on both ground and unground enamel surfaces.

Technology for fluorine-free ground enamels and coatings for chemical apparatus

Until recently ground and cover enamels containing fluorine have been used in the industry. Fluorine added to the enamel in the form of Na~AI~, Na~SiF6, NaF, and CaF2 acts as an excellent flux and produces a sharp reduction in the viscosity of the silicate melts, thereby reducing the melting points of the enamels and fusing them onto the surface of the metal articles. However, a high concentration of florine reduces the chemical resistance and increases the brittleness and the tendency to crystallization of the enamels. The main disadvantage of fluorine compounds is their high volatility, as a result of which there is a change in the chemical composition of the enamels; the properties are less stable, and most important of all, the surrounding atmosphere is contaminated with toxic fluorine and its compounds.

Surface Tension and Contact Angle on Enamel of Surfactant Solutions for Caries Diagnosis with Dyes

We measured the surface tension of solutions of five surfactants in water, ethanol, and a 50% water/ethanol mixture at 25 degrees C, as well as the contact angle of these solutions on ground and polished bovine enamel in vitro and on intact pellicle-covered human enamel in vivo. All surfactants lowered the surface tension of water. In ethanol, no reduction of the surface tension was achieved by any of the five surfactants. In the water/ethanol mixture, only Fluorad lowered the surface tension from 29.2 to 19.7 mJ.m-2 at 25 degrees C. On bovine dental enamel, all surfactant solutions showed a significantly lower contact angle than did distilled water. On pellicle-covered human enamel, Rewoteric in distilled water showed no significantly lower contact angle than did pure distilled water, but all other solutions did. Both in vitro and in vivo, ethanol spread instantaneously over the enamel surface. Based on these measurements, we concluded that several surfactants may be used to spread aqueous dye solutions. In a 50% mixture of water and ethanol and in pure ethanol, no surfactant is necessary for enhanced spreading of the solution, but surfactants may be considered for adhesive properties.

Silicate ground enamels based on oxidized nickel ore

Silicate ground enamels based on oxidized nickel ore