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Biomedical subjects

H J Staehle

Publications and source records attributed to H J Staehle.

At least 19 recordsLinked to original sources
PubMed1992

An experimental study of the stability of irradiated teeth in the region of the dentinoenamel junction.

In this in vitro study we investigated the influence of ionizing gamma rays on the stability in the region of the dentinoenamel junction. We removed the enamel on the labial surface of 30 incisors of bovines up to the dentinoenamel junction, so that a circular area of enamel with a diameter of 2.0 +/- 0.1 mm was left and an enamel cylinder was created. 15 teeth were irradiated by a cobalt-60-source (energy dose 70 Gy). The other 15 teeth were used as controls. Using a material testing apparatus the shear bond strengths were measured by breaking off the enamel cylinders. Furthermore, the breaking modes were investigated in SEM. Comparing the results of the shear bond strength experiments, it was obvious that the stability in the region of the dentinoenamel junction was significantly less among the irradiated teeth than among the non-irradiated teeth. The median value of the gamma ray treated teeth was x = 19.1 MPa and that of the non-ray-treated teeth was x = 37.4 MPa. The non-irradiated teeth showed fractured surfaces only in dentin in 10 cases and in 5 cases in both dentin and enamel. In contrast to that, the irradiated teeth had fractured surfaces in 12 cases exclusively in dentin and only in 3 cases the enamel was also fractured. These results lead us to conclude that changes of biophysical property of teeth can be caused by the influence of ionizing rays.

Animals↗
PubMed1992

[The marginal sealing of composite inlays with different cavity liners].

In this in-vitro study we investigated the sealing properties of composite inlays (EOS system) dependent on 8 different base materials. Using a dye-penetration test, the sealing was determined after mechanical and thermal cycling. A partially massive dye-penetration was detected in most cases when one of the following materials was used: a calciumsalicylate cement (Dycal), a combination of calciumsalicylate cement and a resin (Basic), a calcium hydroxide filled resin (Prisma VLC-Dycal), or a zinc phosphate cement (Harvard Cement). In contrast to this, we discovered a complete or almost complete sealing in most cases after application of chemically-cured glass ionomer cements (Ketac-Bond, Ketac-Bond Aplicap, Base-Line) or a light-cured glass ionomer cement (XR-Ionomer) as base materials. From these results it can be concluded that the choice of base materials has an influence on the marginal sealing of composite inlays after thermal and mechanical cycling. However, it is not possible to make a definitive statement on the suitability of these base materials under clinical conditions, because the results of dye-penetration tests have only limited clinical validity.

Color↗
PubMed1991

[Solubility of enamel and synthetic hydroxylapatite on irradiation].

The effect of Co 60-irradiation (70 Gy) on pulverized human enamel and synthetic hydroxyapatite was studied in vitro. Irradiated and non-irradiated samples were experimentally demineralized (pH 5.1) during a period of 28 days. In terms of solubility, defined as the equilibrium of saturation, there was no statistically significant difference between irradiated and non-irradiated enamel. However, in terms of solubility rates, defined as the amount of dissolved substance during the demineralization period, irradiated enamel showed a statistically significantly higher solubility rate than non-irradiated enamel. There was no effect of Co 60-irradiation on synthetic hydroxyapatite.

Dental Enamel Solubility↗
PubMed1991

[Experimental study of compactness of occlusal composite restorations as compared to occlusal metal inlays].

In this study class I cavities were prepared in extracted human molar teeth. The cavities were treated with composite restorations or metal inlay restorations. After thermal and occlusal stress, the marginal seal was tested using a dye-penetration-test. The results were evaluated as follows: Grade 0-Grade 1 = sealed or almost sealed restoration; Grade 2-Grade 3 = evident or clearly distinct loss of marginal adaptation. The study showed following results: 1 Composite restorations (Heliomolar) proved seven out of ten cases to be sealed or almost sealed (Grade 0 or Grade 1). Three out of ten cases showed a dye penetration at Grade 3. 2 Metal inlays (Degulor M) that were cemented with zinc phosphate cement, were rated in none of the cases as sealed. They showed in nine out of ten cases a dye penetration at Grade 2 or 3. With dye-penetration-tests conclusions can be made regarding the marginal seal of restorations. However, clinical application of a restorative material should not be made dependent on this criteria alone.

Acrylic Resins↗
PubMed1991

[Experimental research on the finishing and polishing of amalgam fillings].

In an in-vitro study occlusal amalgam restorations were finished and polished with four different methods. The quality of the restorations were evaluated according to the surface homogeneity and marginal adaptation. Additionally, the loss of substance due to the finishing and polishing process was determined. The results can be summarized as follows: The use of carbide finishing burs in combination with silicon polishing instruments (method A) results in rather smooth surfaces with numerous defects in the marginal area. The maximum loss of substance was about 160 microns in the filling material and about 110 microns in the adjacent enamel. Diamond finishing burs (grain size 30 microns = method B; grain size 15 microns = method C) in combination with silicon polishing instruments lead to rougher surfaces. The marginal areas, however, showed less deficiencies compared with method A. The maximum loss of substance in the adjacent enamel was about 220 microns (method B) and about 200 microns (method C), respectively, and in the amalgam area about 200 microns (method B) and 90 microns (method C), respectively. When finishing and polishing was done with a brush and a polishing paste (method D), the surface homogeneity and marginal adaptation of the restorations showed poor results. However, the maximum loss of substance was strongly decreased compared with methods A, B and C to an average of about 40 microns in the adjacent enamel and to about 75 microns in the amalgam. In conclusion, the application of the finishing and polishing methods A, B and C leads to a higher quality of the amalgam restoration than that, which can be achieved by applying method D.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Amalgam↗
PubMed1991

[Experimental study of material properties of calcium salicylate cement with and without polymeric additives].

In this study a new calcium-salicylate cement with an additional polymerized filler material (Alkaliner) was compared with a commonly used calcium-salicylate cement without polymerized filler material (Dycal) regarding the microstructure, the EDX elemental analysis, the hydroxid ion release, the compressive strength and the film thickness. The tests showed the following results: 1. Alkaliner and Dycal are almost identical in relation to their micro-morphology and elementary composition (EDX-analysis). 2. In the titration test, Dycal and Alkaliner show no significant differences (p = 0.05) in the hydroxid ion release. 3. Having stored the specimens in synthetic saliva for 2 days, the compressive strength of 25 MPa is noted for both of the materials. Having stored the specimens for 150 days, the compressive strength of Alkaliner (8.3 MPa) is significantly (p = 0.05) higher than that of Dycal (3.8 MPa). 4. The film thickness was measured by placing the materials between dry glass-plates. Dycal measures an average of 19.8 micrometers and Alkaliner of 30 micrometers. Under these experimental conditions the measured difference is statistically significant (p = 0.05). Placing the materials between damp glass-plates, the film thicknesses increase to an average of 56.5 micrometers (Dycal) and of 50 micrometers (Alkaliner) respectively. This difference however, is statistically not significant (p = 0.05).

Calcium↗
PubMed1989

The alkalizing properties of calcium hydroxide compounds.

Calcium hydroxide compounds are available in various forms, such as in aqueous suspensions or as cements, liners, pastes or filled resins. When such compounds are exposed to water, the calcium hydroxide dissociates and the pH value shifts to the basic. In this study the compounds Pulpdent, Dycal, Hydroxyline, Gangraena Merz and Prisma VLC-Dycal were subjected to analysis, including quantitative measurement of the amount and the chronological course of ion release following exposure to water, qualitative analysis of the alkalizing effects at the dentin surface and examination of antimicrobial properties. The results showed that calcium hydroxide compounds differed greatly. The strongest degree of ion release, combined with definite antimicrobial properties, was found for the aqueous calcium hydroxide suspension (Pulpdent). The cement (Dycal) demonstrated significantly weaker activity. The liner and the paste (Hydroxyline and Gangraena Merz), as well as the calcium hydroxide filled resin (Prisma VLC-Dycal), were largely lacking in both ion release and antimicrobial properties under the experimental conditions.

Calcium Hydroxide↗
PubMed1989

[Antimicrobial efficacy and alkalizing effect of different calcium hydroxide compounds].

This publication compares the alkalizing effect of various calciumhydroxide compounds and their antimicrobial efficacy. In these experiments aqueous calciumhydroxide suspensions demonstrate the comparably highest alkalization combined with a profound longacting antimicrobial action. At relatively minor alkalization the examined calciumhydroxide cement caused a less profound, but also consistent inhibition of bacterial growth. Samples of calciumhydroxide-containing liners, fillers, and synthetic compounds, although showing a marked alkaline reaction themselves, did, however, not or almost not cause an alkalization of the environment or an inhibition of bacterial growth.

Bacteria↗
PubMed1989

[Bonding of glass-ionomer cements to tooth hard tissues under various experimental conditions].

In this study the enamel- and dentin-bonding properties of two glass-ionomer cements (ChemFil-II and Ketac-Bond) were evaluated under various test conditions in vitro. The tests showed the following results: 1. ChemFil-II exhibits a significantly stronger bond to the hard tooth substances than Ketac-Bond in the short term test (the samples were stored 2 days in synthetic saliva). The stability of the bond made with ChemFil-II, however, proves in the long term test (the samples were stored 150 days in synthetic saliva) to be less than that made with Ketac-Bond. 2. Acid-conditioning of the enamel does not statistically effect a change in the stability of the bond to any significant degree. Corresponding conditioning of the dentin, on the other hand, causes a definite reduction of the bond to be obtained. 3. Deviations from the powder-liquid mixing ratio recommended by the manufacturer result in a statistically significant reduction in the bond stability, whether these involve an increase in the amount of powder or rather a decrease.

Aluminum Silicates↗
PubMed1989

[Experimental study of the effect of intermediate substances on the margin seal of amalgam restorations].

In the preceding study Class-I-cavities in extracted human molars and premolars were restored using amalgam following diverse pretreatment methods. The teeth were stored in synthetic saliva for 7 days during the short-term test and for 6 months in the extended test. The tightness of the cavity seal was examined using a dye penetration test. The results show that the intermediate substances which may be applied have greatly divergent effects on the tightness of the seal around amalgam restorations.

Dental Amalgam↗