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Biomedical subjects

U Platzer

Publications and source records attributed to U Platzer.

11 recordsLinked to original sources
PubMed1998

Age and Helicobacter pylori decrease gastric mucosal surface hydrophobicity independently.

BACKGROUND: Gastric mucosal surface hydrophobicity (GMSH) is an essential component of the mucosal defence system that is decreased by Helicobacter pylori and non-steroidal anti-inflammatory drugs (NSAIDs). Gastric ulcers occur predominantly in elderly subjects, and may thus reflect diminished mucosal resistance. AIMS: To investigate whether aging decreases GMSH. PATIENTS: One hundred and twenty patients without peptic ulcer disease were divided into three age groups: I (41 years or below); II (41-64 years); and III (65 years or above). METHODS: Biopsy specimens were taken from the antrum, corpus, and cardia for histology (Sydney system), urease testing for H pylori, and for contact angle measurement of GMSH with a goniometer. The presence of specific H pylori antibodies was checked by immunoblotting. RESULTS: Fifty two patients (43%) were infected, and 68 were uninfected with H pylori. GMSH at all biopsy sites was lower in H pylori infected subjects (p=0.0001), but also decreased with age independently of infection status (p=0.0001). The most notable decrease in GMSH occurred between age groups I and II in those with, and between age groups II and III in those without, H pylori infection. GMSH was greater in antral than in corpus mucosa in both infected (p=0.0001) and uninfected patients (p=0.0003). CONCLUSIONS: A physiological decrease in GMSH with aging may contribute to the risk of ulcer development in the elderly, and may act synergistically with H pylori and/or NSAIDs on gastric mucosal defence.

Adult↗
PubMed1997

Effect of different surface textures on retentive strength of tapered posts.

STATEMENT OF PROBLEM: Tapered posts allow for the preservation of tooth substance in the fragile apical area and are advantageous in clinical situations where they conform to the root and canal configuration of endodontically treated teeth. However, their lower retention compared with passive parallel-sided or active threaded posts is a disadvantage. PURPOSE: This study determined the retentive strength of tapered titanium posts with different surface textures and examined the effect of roughening dentinal walls of the prepared post space. MATERIAL AND METHODS: Posts with four surface configurations (smooth, with and without grooves, and sandblasted, with and without grooves) were examined when cemented in extracted anterior teeth. RESULTS: The smooth post showed the lowest retentive strength. Sandblasting the smooth post more than doubled its retentive strength. The retentive strength of both smooth and sandblasted posts could be further increased by the addition of circumferential grooves. Roughening the dentinal walls of the prepared post space increased the retentive strength of sandblasted posts with and without grooves even more. CONCLUSIONS: These findings indicated that, when a tapered post is used, roughening the dentin canal wall, as well as sandblasting and grooving the post, can provide statistically significant additional resistance to dislodgment.

Analysis of Variance↗
PubMed1996

Shear bond strength of a new polycarbonate bracket--an in vitro study with 14 adhesives.

Shear bond strength and failure location were used to evaluate the effectiveness of plastic bracket primers for bonding diacrylate adhesives on a new fibre-reinforced polycarbonate bracket. Maxillary incisor polycarbonate and mesh-based brackets as control were bonded to human incisors with 14 different adhesives (four filled diacrylate two-paste, six diacrylate one-step and four power-liquid acrylic adhesives), and after thermo-cycling for 2000 cycles between 5 degrees and 55 degrees C, tested in shear. A non-parametric test (Mann-Whitney U test) was used to compare the shear bond strength of the polycarbonate brackets with the mesh based brackets and a One-way test (according to Scheffe) to compare the shear bond strength of different adhesives. The following conclusions can be made: 1. Seven of the 14 adhesives used in this study with both types of brackets demonstrated adequate shear bond strength values for the clinical application. The exceptions were: Achieve Mix, No-Mix:30 Silkon, Lee Insta-Bond, Ortho-Loc and Bond-Eze, all with too low a shear bond strength for one or both types of brackets, and finally Quasar, which used with the plastic brackets sometimes caused enamel fractures, due to high bond strength. 2. The adhesives with their own plastic primer demonstrated higher blood strength values than those without plastic primer, and two-paste adhesives used with plastic primer displayed a higher bond strength than the other adhesives. 3. Generally, the shear bond strength values of the one-step adhesives were lower compared with the two-paste adhesives. 4. The liquid-powder adhesives demonstrated very different values for bond strength.

Composite Resins↗
PubMed1995

[The shearing strength of titanium brackets depending on the coating procedure].

It has long been recognized that corrosion of the metal alloys used in the different fields of dentistry can cause intra-oral problems such as allergic reactions. Titanium, a metal all but impervious to corrosion, presents an alternative to the metal alloys used in the fabrication of orthodontic brackets. The purpose of this study was to test the bonding strength between titanium brackets treated with 5 different opaque and non-opaque coatings and a 2-phase adhesive. Five coating methods were tested: N1 (Dentaurum), N2 (Dentaurum), Rocatec (Espe), Sebond (Schütze), Silicoater Standard (Kulzer). After bonding the brackets with a mix adhesive, they were thermocycled and then the shear bonding strength established. Silicoated titanium bracket bases showed clinically acceptable bonding values with the exception of those coated with Sebond without opaquer layer. While the silicoating methods N1, N2, and Rocatec demonstrated minimum bonding strength using the opaquer Visio-Gem, the bonding strength of the bracket bases coated with Sebond MKV, Silicoater Standard and the opaquer appropriate to each was significant increased. Among all the coated surfaces, methods N1, N2, and Rocatec appear to establish the optimum bonding strength values. In addition, the thin opaquer layer (Visio-Gem) used together with these methods offers a good surface adaptation of the bracket to the tooth surface.

Dental Bonding↗
PubMed1992

[The effect of the different metal components on bracket adhesive strength in the Silicoater procedure].

This study was undertaken to test the theory that different kind of metal alloys can influence the bond strength of the silane treated bracket bases. Seven different types of brackets, each with different metal properties, were tested. 20 brackets of each type were used, half of them were silanated with a special Silicoater treatment. The following conclusions can be made: 1. The silane coated plain bracket demonstrated a higher bond strength than all the tested untreated brackets; 2. the brackets of the company Dentaurum demonstrated a statistically significant higher bond strength than the brackets of all the other companies.

Dental Alloys↗
PubMed1991

[Bonding strength of brackets with and without silane coating].

This study was undertaken to show that a silane treated bracket base can provide a better bonding to the enamel than conventional bonding bases commercially available. Five different types of metal brackets, each with different retentive properties, were tested. 20 brackets of each type were used, half of them silanated with a special silicoater treatment. The brackets were bonded to the surface of the teeth with Concise Enamel Bond and were then tested to failure in an Instron testing machine after 28 days. The following conclusions can be drawn from the study: 1. Silane-coated bracket bases demonstrated a higher bonding strength than the conventional bases, 2. silane treatment of plain bases is an effective method for the bonding of brackets to teeth, similiar to non-silane-boated brackets with additional mechanical retentive devices.

Acrylic Resins↗
PubMed1990

[Studies on the composite joint in Cerec inlays].

In an in vitro study 32 ceramic restorations were constructed using the Cerec system and adhesively fixed in cavities prepared in extracted teeth with Dual Cement according to the supplier's instructions. The restored teeth were then histologically prepared and the joints between cement and inlay morphometrically evaluated at eight defined sites. The measurements showed average values of 118 microns with a standard deviation of 53 microns. It is particularly interesting to note the extremely great range of variation between the lowest and the highest value. The measured widths of the joints must be considered as a weakness of the system, because clinically they may result in wash-outs and material collapses in the long run. So far, no long-term studies have been conducted yet to investigate this effect.

Composite Resins↗