Biomedical subjects

R Janda

Publications and source records attributed to R Janda.

At least 19 recordsLinked to original sources

PubMed2007

Laser-induced fluorescence to discriminate between a dental composite resin and tooth.

PURPOSE: Investigation of laser-induced fluorescence of an experimental pigment (Flu) to discriminate between a filling and the tooth and its influence on the material properties of experimental dental composites. MATERIALS AND METHODS: Three experimental composites (EC) were manufactured. The standard contained no Flu, Flu-0.5 contained 0.5%, Flu-1.0 contained 1%. To judge the extent of fluorescence, specimens and fillings placed in natural teeth were irradiated with an infrared laser (980 nm, 120 mW). Flexural strength, modulus of elasticity, depth of cure, water sorption, solubility, and color (CIE-L(*)a(*)b(*)-values) were measured to investigate the influence of Flu on EC. ANOVA was calculated and the statistical significance was p < 0.05. RESULTS: Strong laser-induced green fluorescence was observed so that fillings and tooth structures were clearly discriminated. No influence of Flu on flexural strength and modulus of elasticity occurred. Water sorption and solubility were far below the limits of EN ISO 4049. Increasing Flu concentrations revealed minor but significant reduction of depth of cure, shifts to more white and red and less yellow. SIGNIFICANCE: Flu provides laser-induced fluorescence allowing an easy discrimination between fillings and teeth. Flu did not severely influence the material properties.

Absorption↗

PubMed2006

Effect of exponential polymerization on color stability of resin-based filling materials.

PURPOSE: To investigate the influence of a halogen light curing device used with constant or exponential polymerization mode on the color stability of contemporary resin-based filling materials. MATERIALS AND METHODS: Eight samples of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) each were light-cured with constant power or with soft-start mode (Translux Energy) for 20, 40 or 60s. The CIE-Lab-values (L(*), a(*), b(*)) were measured prior to and after performing dry aging, water aging or a Suntest (EN ISO 7491) and Delta L-, Delta a-, Delta b-, and Delta E-values were calculated. RESULTS: Statistical analysis (GLM and repetition of measures) showed significant changes (p<0.05) of the color values for each material's curing mode and time after each of the aging processes. Four-way ANOVA revealed significant differences (p<0.05) between Delta L-, Delta a-, Delta b-, and Delta E of the materials in dependence on the curing time and mode and aging condition. Exponentially-cured DU was the most color-unstable material after aging in water followed by the 20s exponentially cured DE and CH samples. After the Suntest, DY showed significant bleaching (negative Delta b) and the largest Delta E for all curing times and modes followed by the DE samples. DU and CH were the most color-stable materials in this test. SIGNIFICANCE: The extent of discoloration depends on the (a) curing time, (b) curing mode, (c) aging condition, and (d) material. For the constant curing mode, 40s curing time for the exponential 60s seems to be appropriate.

Analysis of Variance↗

PubMed2006

Spark erosion as a metal-resin bonding system.

PURPOSE: Resin to metal bond strength of two commercial and one experimental metal-resin bonding system for crown and bridge veneer composites was evaluated. MATERIALS AND METHODS: All specimens were prepared and tested according to ISO 10477 Amendment 1. A high precious alloy (HPA), a Co/Cr-alloy (Co/Cr) and pure titanium (Ti) were wet-ground to a final surface finish of 800 grit and air-dried. Twenty specimens of each metal were treated with Rocatec (RO), 20 with a Silano-Pen (SP), and 20 with the experimental spark-erosion (SE) bonding system. A light-curing opaque and a crown and bridge veneer composite were applied to each metal specimen. Ten specimens of each metal and bonding system were stored in water for 24h at 37 degrees C, 10 were thermocycled (TC) 5000 times in a water-bath between +5 and +55 degrees C prior to measuring shear bond strength (SBS). Scanning electron microscopy (SEM) was used to examine the treated metal surfaces. RESULTS: After 24h SE generated significantly higher SBS values on Ti than RO (p<0.05). SP revealed the highest SBS for Co/Cr. After TC significant decreases occurred for RO on HPA, for SP on Co/Cr and Ti, and for SP on Ti. SE revealed the highest mean bond values for all metals. These results and SEM proved that no sandblasting is required for SE to obtain good bond strength. SIGNIFICANCE: The experimental spark-erosion bonding system is an easy and very effective method for surface-treating alloys to obtain high SBS values for crown and bridge veneer composites.

Chromium Alloys↗

PubMed2006

The effects of thermocycling on the flexural strength and flexural modulus of modern resin-based filling materials.

OBJECTIVE: Evaluation of flexural strengths and flexural moduli of hybrids, packables, ormocers, compomers and flowables prior to, and after, thermocycling. MATERIALS AND METHODS: Twenty specimens, size (25 +/- 2) mm x (2 +/- 0.1) mm x (2+/-0.1) mm, of Herculite (HE), Point 4 (P4), TetricCeram (TC), Miris (MI), TetricCeram HB, (HB), Solitaire 2 (SO), Surefil A (SU), Definte (DE), Admira (AD), Dyract AP (DY), Compoglass (CO) and TetricFlow (TF) were made according to ISO 4049. A three-point-bending test was carried out for the first 10 specimens after 24 h water storage at 37 degrees C and for the second 10 specimens after 30-day water storage at 37 degrees C, followed by 5000 thermocycles between +5 and +55 degrees C. For each test series flexural strengths and flexural moduli were calculated. Statistical significance was p < 0.05. RESULTS: Flexural strengths of DY and CO missed the 80 MPa limit of ISO 4049 for occlusal fillings prior to and after thermocycling. AD missed it after thermocycling. HE, P4, TC, MI, HB, SO, SU, DE and TF did not significantly differ prior to and after thermocycling. Flexural strength of SO and AD significantly decreased after thermocycling. No change of the flexural moduli could be observed for any of the test materials. Only SU exceeded 10,000 MPa prior to and after thermocycling. SIGNIFICANCE: Only DY and CO missed the flexural strength limit of ISO 4049 for occlusal fillings. Only SU exceeded a flexural modulus of 10,000 MPa prior to and after thermocycling.

Analysis of Variance↗

PubMed2003

[Blood loss and absorption in TURP vs. TUVRP under low pressure and high pressure conditions].

This study analyzes the causes of different fluid absorption and loss of blood in TURP (transurethral resection of the prostate) and also compares TURP with TUVRP (transurethral vaporesection of the prostate). Continuous intraoperative, intravesical pressure measurement and registration of the extent of fluid absorption (measurement of C(2)H(5)OH in the patient's expiratory air) and precise intra- and postoperative analysis of serum and ASTRUP analysis made it possible to differentiate between high- and low-pressure TUR. In addition positive and negative characteristics of TUVRP could be examined. When fluid absorption was registered, a clear correlation between C(2)H(5)OH absorption and decrease in serum concentration of sodium could be seen, making sodium in serum a good marker of fluid absorption. Neither the duration of the operation nor the size of the adenoma had an influence on fluid absorption and loss of blood, but sinus bleeding and capsular lesions, especially in high-pressure TUR, had a significant influence. An advantage of low-pressure TUR, especially in "low compliance bladder," could be clearly seen. No benefit concerning fluid absorption and loss of blood was seen in cases of total resection by TUVRP. In cases of palliative, planned TUR (elderly patients with multiple risk factors) a TUVRP is recommended.

Aged↗

PubMed2003

A new adhesive technology for all-ceramics.

OBJECTIVES: Evaluation of a new surface treatment method to obtain a good bond strength between a luting composite and several ceramics. METHODS: Specimen preparation and test procedure were done according to ISO 10477 Amendment 1. The surfaces of Empress II, InCeram-Alumina, InCeram-Zirconia and Frialit (ZrO2) were ground under water-cooling with 400 grit grinding paper, afterwards polished with 800 grit and air-dried. Each ceramic material investigated was divided into three groups of 10 specimens each. Group 1 was flame-treated with the PyrosilPen for 2.5 s, group 2 for 5 s and group 3 for 10 s/cm(2). After the flame treatment, a methacryl silane was applied followed by a luting composite. Prior to measuring shear bond strength, the specimens were thermocycled 5,000 times in a water-bath between +5 and +55 degrees C. Furthermore, SEM- and Fourier-transform infrared spectrophotometer (FT-IR)-investigations were done. As a control, Empress II etched and silaned was used. RESULTS: Shear bond strength measurements indicated that the optimal treatment time was 5 s/cm(2). Regarding this time the following bond strength values between the luting composite and the various ceramics were obtained: Empress II 23 (5)MPa, InCeram-Alumina 23 (5)MPa, InCeram-Zirconia 13 (8)MPa, and Frialit 16 (6)MPa. The control achieved 27 (6)MPa. On all surfaces of the flamed specimens Si could be detected by FT-IR.Significance. The PyrosilPen-Technology is an easy and effective method for surface-treating silicate, aluminum oxide and zirconium oxide ceramics to obtain good bonding to luting composites.

Aluminum Oxide↗

PubMed1999

[New direct restorative materials].

People worldwide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials. Amalgam and its potential toxic side effects (still scientifically unproven) continue to be discussed with increasing controversy by the media in some countries. Consequently, new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so-called 'amalgam substitute' or 'amalgam alternative'. From a critical point of view some of the new direct restorative materials are good with respect in aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and longterm clinical behaviour.

Biocompatible Materials↗

PubMed1998

New direct restorative materials. FDI Commission Project.

People worldwide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials. Amalgam and its potential toxic side effects (still scientifically unproven) continue to be discussed with increasing controversy by the media in some countries. Consequently, new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so-called 'amalgam substitute' or 'amalgam alternative'. From a critical point of view some of the new direct restorative materials are good with respect to aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and longterm clinical behaviour.

Biocompatible Materials↗

PubMed1995

Preparation of extracted natural human teeth for SEM investigations.

Direct and indirect (replica) methods for investigating natural hard tooth tissues by scanning electron microscopy have been compared. The direct method requires an effective dehydration and drying procedure to avoid artefacts. A simple, fast and very effective procedure is described in this investigation. This recommends dehydration with differently concentrated mixtures of water/ethanol followed by mixtures of ethanol/acetone so that critical point drying can be avoided with regard to hard tooth tissues. The indirect method is carried out by taking impressions of the tooth surfaces with an addition-type polysiloxane. A positive model is manufactured from this impression using an epoxy resin. When investigated by scanning electron microscopy, the epoxy model reflects only very obscure pictures of the original tooth surface. The indirect method can only be recommended in cases where direct investigation is impossible. For instance, when non-extracted teeth are investigated or when extracted teeth are expected to be influenced by the dehydration and drying process.

Biocompatible Materials↗

PubMed1993

Pharmacokinetics of dirithromycin in patients with impaired hepatic function.

Dirithromycin is a new macrolide antibiotic. A non-blinded, non-comparative study was performed in patients with mild, (Pugh and Childs Grade A) chronic, stable, impaired hepatic function (CSIHF) to determine the single- and multiple-dose pharmacokinetics and safety in such patients. Eight volunteers had disease affecting primarily the hepatic parenchyma, eight had primarily biliary system diseases and five healthy volunteers served as the control population. CSIHF patients and healthy volunteers all received a single dose of dirithromycin 500 mg po and 2 weeks later a 10-day course of dirithromycin 500 mg po once a day. Blood and urine samples were obtained with single dose administration and on days 1 and 10 of multiple-dose administration. The area under the serum concentration versus time curve (AUC) was higher with multiple-dose administration than with single-dose administration in all three treatment groups; however, the difference was not statistically significant between the treatment groups. With multiple-dose administration, peak serum concentrations (Cmax) were 0.69 +/- 0.74, 0.34 +/- 0.15, and 0.78 +/- 0.25 mg/L and the AUC0-24 were 6.45 +/- 6.27, 4.05 +/- 1.59, and 6.60 +/- 2.89 mg.h/L in normal, parenchymal, and biliary volunteers, respectively. Cmax and AUC were consistently lower in subjects with parenchymal disease than those with biliary disease or normal volunteers but the reason for this is unclear. Statistically significant differences in clearance, due to lower non-renal and renal clearances in the biliary volunteers with single- or multiple-dose administration were found between the groups but these differences were not thought to be clinically or pharmacokinetically relevant for short-term antibiotic administration. With dirithromycin administered for 14 days or less, no dosage adjustment should be necessary in patients with mild hepatic insufficiency.

Adolescent↗

PubMed1992