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Biomedical subjects

B Haller

Publications and source records attributed to B Haller.

At least 19 recordsLinked to original sources
PubMed1996

Effect of disodium monofluorophosphate, calcium and vitamin D supplementation on bone mineral density in patients chronically treated with glucocorticosteroids: a prospective, randomized, double-blind study.

To study the effect of fluoride on bone mineral density (BMD) in patients treated chronically with glucocorticosteroids, 15 subjects (renal grafted, n = 12; skin disease, n = 1; broncho pulmonary disorder, n = 1; Crohn's disease, n = 1) were prospectively studied in a double-blinded manner and randomly allocated either to group 1 (n = 8) receiving 13.2 mg/day fluoride given as disodium monofluorophosphate (MFP) supplemented with calcium (1,000 mg/day) and 25-hydroxyvitamin D (calcifediol) (50 micrograms/day), or to group 2 (n = 7) receiving Cas+ calcifediol alone. An additional group of 14 renal transplant patients treated chronically with glucocorticosteroids but exempt of specific therapeutic intervention for bone disease was set up as historical controls. BMD was measured by dual-energy X-ray absorptiometry (DXA, Hologic QDR 1000) performed at months 0, 6 and 12 for groups 1 and 2 (lumbar spine, total upper femur, diaphysis and epiphysis of distal tibia), or 11-31 months apart with calculation of linear yearly changes for the historical cohort. Lumbar BMD tended to rise in groups 1 and 2, and to fall in group 3, the change reaching statistical significance (p < 0.05) in group 1, thus leading to a significant difference between groups 1 and 3 (p < 0.05). At upper femur, tibial diaphysis and tibial epiphysis, no significant change in BMD occurred in any of the groups. In conclusion, lumbar BMD rises more after a mild dosis of fluoride given as MFP and combined to calcium and calcifediol than on Ca+ calcifediol alone, without changes in BMD at the upper femur or distal tibia.

Absorptiometry, Photon↗
PubMed1993

Effect of storage media on microleakage of five dentin bonding agents.

The objective of this study was to investigate the effect of different storage media on microleakage at the gingival margin of mixed Class V composite restorations. Human molars were either used immediately after extraction (control group) or after a 3-4 wk storage period in 1% chloramine, 70% ethanol, 10% formalin, or 0.1% thymol. Class V cavities with cervical margins in cementum or dentin were prepared and restored with a microfill composite using five different dentin bonding agents. After thermocycling (1440 x from 5 degrees C to 55 degrees C) and basic fuchsin staining, the depth of dye penetration at the gingival margins was determined and ranked on a scale of 0 to 4. Class V restorations in teeth stored in formalin showed significantly less microleakage (mean leakage score, MLS = 1.7) than restorations in freshly extracted teeth (control group; MLS = 3.1). Microleakage scores in teeth stored in chloramine (MLS = 2.7), ethanol (MLS = 3.0) or thymol (MLS = 3.2) were not significantly different from the microleakage scores in the control group. The improvement of in vitro efficacy of dentin bonding agents when using extracted teeth stored in formalin is probably a result of collagen cross-linking by formaldehyde. Since such an alteration of the dentin does not reflect the condition of the substrate in vivo, extracted teeth assigned for in vitro evaluation of dentin bonding agents should not be stored in formalin. In teeth stored in 1% chloramine, the sums of ranks and the rank orders of the dentin bonding agents were comparable to those in freshly extracted teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1993

[The surface conditioning of pressed ceramics and its effect on the bond strength to composites].

After removal of the investment material, unpolished surfaces of pressed glass ceramics (Empress) are covered by a layer containing magnesium and phosphorus. This layer most likely results from the contact with the investment material during pressing. Following short-time conditioning with 5% HF-gel the superficial layer stays amorphous. After etching for 120 s most of the surface layer is removed revealing the fine grained etching pattern characteristic for this type of ceramics. Shear strength of composite luted to unetched pressed ceramic samples was rather low. After etching for 60 s bond strength was considerably higher, but only following 120 s of etching shear strength reached a level comparable to that of ground pressed samples and ground ingots after 60 s of etching. Since mechanical removal of the surface layer by grinding is not recommended, pressed glass ceramics should be etched for 120 s or longer to achieve an optimal bond strength to the luting composite.

Acid Etching, Dental↗
PubMed1991

Shear bond strength to dentin by simulation of three-dimensional Class V cavity configuration.

The purpose of this study was to investigate the effect of composite polymerization contraction on early shear bond strength of conventional and new dentin adhesives to dentin. The dentin adhesives selected for this study, i.e., Bondlite, Gluma, Prisma Universalbond, Scotchbond LC, Scotchbond 2, and XR Bonding, were tested in combination with Silux and in combination with their respective composites. The composite was applied to the treated dentin surface in cylindrical brass moulds of 4 mm diameter and 3 mm length. The configuration of cylindrical butt-joint Class V cavities was simulated by the coating of the insides of the brass moulds with silane in order that a chemical bond to the composite could be established. The results showed that shear bond strength to dentin was higher for XR Bonding and Scotchbond 2 compared with conventional phosphate ester-based dentin adhesives and Gluma. When XR Bonding or Scotchbond 2 was used, the obstruction of polymerization contraction had no effect on the bond strength to dentin. In contrast, the dentin adhesion of Scotchbond LC/Silux, Prisma Universalbond/Prisma Microfine, Bondlite/Herculite, and Gluma/Lumifor was adversely affected by the reduction of the unbonded composite surfaces. However, this effect was not observed when Prisma Universalbond, Bondlite, and Gluma were tested in combination with Silux. It can therefore be concluded that the effect of polymerization contraction on the bond strength to dentin depends not only on the dentin adhesive but also on the type of composite used.

Adhesives↗
PubMed1991

Parapulpal pins and their effects on the fracture resistance of pin-retained cores.

The bending characteristics of various parapulpal pins, the retention of a parapulpal pin in different core buildup materials, and the fracture resistance of pin-retained cores were investigated in an in-vitro study. In amalgam and composite cores, the use of parapulpal pins produced an increase in fracture resistance. The highest fracture resistance values were observed in amalgam cores, and the lowest fracture strength was exhibited by cores of glass ionomer cements (GICs) containing metallic particles. The different parapulpal pins and their flexural rigidity had little effect on the fracture resistance of the pin-retained cores. For extensive pin-retained cores it appears advisable to use GICs with restraint and, particularly in the case of large-scale bridge reconstructions, only after critical examination of the loading conditions.

Alloys↗
PubMed1991

[The effect of cavity finishing on the initial sealing capacity of amalgam fillings in vitro].

The effect of different cavity finishing methods on in-vitro microleakage of two amalgams (Amalcap non gamma 2 SAS, Tytin) was investigated by the dye penetration method. Amalcap non gamma 2 SAS demonstrated better sealing properties than Tytin. The highest degree of microleakage was observed when the cavities prepared with a diamond coated bur (mean particle size 80 microns) were left unfinished. The degree of marginal leakage in Class-I cavities was reduced by finishing their walls with tungsten carbide or diamond coated finishing burs. Cervical Class-II cavity walls finished with a tungsten carbide or a diamond coated finishing bur demonstrated lower marginal leakage than cervical walls finished with a gingival margin trimmer. Finishing of proximal Class-II cavity walls with tungsten carbide or diamond coated finishing burs followed by removal of the remaining enamel overhangs with a diamond coated file (Cavishape) resulted in a lower degree of dye penetration than finishing proximal walls with a proximal margin trimmer. The results indicate that Class-II cavities with minimal extension of the proximal walls can be effectively finished without using hand instruments.

Dental Amalgam↗
PubMed1990

[Ridge stabilization with adhesive inlays in MOD cavities].

The flexural rigidity of the buccal cusps of upper premolars was determined under a vertical load of 100 N by use of displacement transducers. The stiffness of the cusps was higher when the cavities were restored with cast gold onlays or with composite or ceramic inlays luted with composite resin. In most cases a decrease in cusp stiffness was observed after thermocycling of the teeth restored with composite or ceramic inlays. With amalgam restorations or cast gold inlays, the flexural rigidity of the cusps was not higher than that of the unrestored cavities.

Bicuspid↗
PubMed1990

[Shear bond strength between composite inlay and luting composite resin].

The shear bond strength between composite inlay materials and luting composite resins was measured under different storage conditions and using different finishing techniques. The initial shear bond strength was distinctly higher with light-cured composites subjected to secondary light and heat cure (56.7-81.1 MPa) than with a heat- and pressure-cured material, where appreciable bond strength was achieved only after sandblasting of the composite surface (18.8 MPa). In general, water storage of the samples for 30 days with intermittent thermocycling adversely affected the bond strength. The influence of secondary light and heat curing on the bond strength of primarily light-cured composites was highly dependent on the material used.

Composite Resins↗
PubMed1990

[Marginal seal of cervical composite inlays in vitro].

The presence of microleakage at the dentinal margins of conventional Class V restorations and direct composite inlays in combination with four dentin bonding agents was assessed by means of dye penetration. The use of dentinal adhesives with conventional one-step composite fillings failed to prevent marginal leakage. The dentin bonding agents used in this study were for more efficient when used with direct composite inlays. The resistance to thermal stress of these bonded Class V composite inlays was improved by application of a secondary light and heat cure, probably due to relaxation of residual material stress.

Acid Etching, Dental↗
PubMed1989

[Technology and progress in conservative dentistry].

In a synopsis different possibilities for the use of tooth colored restorations as replacements for amalgam fillings are described and discussed: composite resin fillings, indirect or direct composite resin and ceramic inlays.

Composite Resins↗
PubMed1989

[Influence of die spacer on the marginal gap of partial crowns].

The effect of die spacer in the fabrication of partial crowns was examined in an in vitro study. Even with good overall expansion of the investment material it is impossible to prevent tight spots in the areas of the box form or clasp retentions. These have to be removed by grinding. Accurate application of die spacer may improve the marginal fit significantly while reducing the amount of grinding necessary.

Crowns↗
PubMed1988

Replacement of the macronuclear ribosomal RNA genes of a mutant Tetrahymena using electroporation.

The macronucleus of the ciliate Tetrahymena contains approx. 10(4) ribosomal RNA gene molecules (rDNA) in the form of linear, autonomously replicating palindromes. Previous studies have shown that macronuclear rDNA molecules derived from wild-type (wt) inbred strain C3 out-replicate those derived from wt inbred strain B, in macronuclei initially heterozygous for both, leading to the complete loss of the B rDNA. However, rmm-1, a cis-acting laboratory-induced mutation obtained previously by mutagenesis of inbred strain C3, causes the mutant rmm-1 rDNA to be completely out-replicated by B rDNA. These findings suggest the following hierarchy of replication potential: wt C3 greater than wt B greater than C3-rmm-1. We used electroporation to test whether cells containing only rmm-1 macronuclear rDNA are favorable recipients for transformation with either wt B or C3 donor rDNA molecules. The donor rDNA molecules carried the selectable marker Pmr (paromomycin resistance) located in the coding region of the 17S rRNA. Transformants were obtained, at a frequency greater than 1 in 10(5), by electroporation under a wide range of electrical discharge parameters. The fraction of cells surviving electroporation varied between 2 and greater than 95% in successful experiments. Replacement ('transplacement') of the recipient rDNA was observed, consistent with the prediction that B and C3 rDNA should out-replicate rmm-1 rDNA. These findings are also consistent with the previous conclusion that the differential replication determinants reside in the 5'-nontranscribed spacer of the rDNA.

Animals↗