Pressure dependent highly enantioselective hydrogenation of unsaturated beta-amino acid precursors.
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Amino Acids↗
Biomedical subjects
J Holz
Publications and source records attributed to J Holz.
A 26-year experience with surgical management of tetralogy of Fallot: risk analysis for mortality or late reintervention.
BACKGROUND: Over the past decade repair of tetralogy of Fallot (TOF) in infancy has gained favor. It is still uncertain what effect early complete repair will have on survival or late reoperation on the right ventricular outflow tract. METHODS: To assess these outcomes, we reviewed our experience (1971-1997) with 294 patients undergoing operation at one institution. Median follow-up was 10.6 years (range, 0.1 to 26 years), and was complete for 90.2% patients. RESULTS: Primary complete repair was done in 199 patients (68%), and a staged repair in 62 patients (21%). Thirty-three patients had only a palliative procedure. Sixty-eight patients (23.1%) had complex pathologic processes, including pulmonary atresia in 53. Hospital mortality for primary repair was 11.1% (22/199), for staged repair was 17.7% (11/62), and for palliative procedures was 15.5% (16/103 procedures). Since 1990 mortality has been 2.1%, 11.8%, and 0% respectively (p < 0.001), despite younger age at repair (0.6+/-0.1 versus 2.1+/-0.2 years; p < 0.001). Multivariate analysis identified longer period of hypothermic circulatory arrest, pulmonary artery patch angioplasty, earlier year of operation, and closure of the foramen ovale as risk factors for hospital death. For hospital survivors 20-year survival was 98%+/-3% for TOF with pulmonary stenosis and 88%+/-9% for TOF with pulmonary atresia (p=0.09). Reintervention on the right ventricular outflow tract was needed in 14.1% (37/261) patients. Freedom from reintervention on the right ventricular outflow tract at 20 years was 86%+/-4% for TOF with pulmonary stenosis and 43%+/-16% for TOF with pulmonary atresia (p=0.001). For the subgroup TOF with pulmonary stenosis, this was 85%+/-5% after primary repair and 91%+/-8% after staged repair (not significant). At 15-year follow-up, this was 78%+/-10% for patients not older than 1 year at operation compared with 88%+/-4% for older patients (not significant). CONCLUSIONS: Early mortality after primary repair of TOF has significantly improved and late survival is excellent. Primary repair in infancy does not increase risk for reintervention on the right ventricular outflow tract.
Adolescent↗
The influence of dentine permeability on cytotoxicity of four dentine bonding systems, in vitro.
Dentine adhesives are often placed directly on dentine from which the smear layer has been removed, the thickness of the dentine is minimal and the potential for diffusion of adhesive components into the pulp is greatest. The permeability of the dentine is one factor that should be critical to whether sufficient diffusion of adhesive components occurs to cause damage to pulpal cells. Dentine discs were prepared and divided into those with low-, medium-, and high-permeability. They were then treated with four different dentine adhesives, after which the pulpal side of the dentine was placed in contact with 1 mL of cell-culture medium. The medium was collected at 24 h intervals for 168 h, and was then placed on monolayers of human pulpal fibroblasts for 24 h. The response of the cells was assessed by succinic dehydrogenase activity (MTT method). The results showed that four dentine adhesive systems released sufficient components to cause suppression of cellular metabolism through dentine. High-permeability dentine generally allowed more diffusion of these components, but the effect of dentine permeability depended on the material. On the other hand, the time interval between the application of the bonding agent and collection of the eluant was consistently important for all materials. Materials were most cytotoxic at early intervals, and were generally less cytotoxic at later intervals, although there were exceptions and there was persistent (> 15%) suppression of cellular metabolism even at late (168 h) intervals. The results suggest that application of these materials to dentine, and particularly dentine with high permeability, poses a potential risk to the health of pulpal tissues.
Analysis of Variance↗
In vitro cytotoxicity and dentin permeability of HEMA.
An in vitro diffusion chamber was used to measure the diffusion of 2-hydroxyethyl methacrylate (HEMA) through etched human dentin disks. Concentrations of HEMA, which diffused through dentin, were measured by ultraviolet spectroscopy, and the effect of initial HEMA concentration, dentin thickness, and back pressure on diffusion were assessed. The cytotoxicity of HEMA was determined using BALB/c 3T3 mouse fibroblasts in direct contact with HEMA for 12 or 24 h. HEMA diffused rapidly through dentin under all conditions, but increased thickness, back pressure, or decreased initial concentration all reduced diffusion. The permeability coefficient of HEMA was approximately 0.0003 cm/min, and diffusion through 0.5 mm of dentin reduced the HEMA concentration by a factor of approximately 6,000 (with 10 cm of H2O back pressure). It was concluded that the risk of acute cytotoxicity to HEMA through dentin was probably low, but that decreased dentin thickness, lack of polymerization, or extended exposure times might increase the risk significantly.
3T3 Cells↗
Improved marginal adaptation of ceramic veneers: a new technique.
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Adult↗
Esthetic restorations for posterior teeth: practical and clinical considerations.
The current abundance of posterior esthetic restorative materials and techniques may be confusing. This paper describes a simple and logical global concept that assists clinicians in choosing the appropriate therapeutic modality according to well-defined clinical criteria. Practical considerations about cavity preparation, base-lining, filling, luting, and finishing procedures are reviewed.
Bicuspid↗
Dentinal fluid dynamics in human teeth, in vivo.
Cavities were prepared in human premolars scheduled for extraction for orthodontic reasons. The smear layer was removed from the dentin surface by acid etching, and the cavity was sealed using a hollow chamber. The chamber was filled with sterile saline solution and connected via tubing to a hydraulic circuit featuring an adjustable pressure reservoir and a device that measures fluid movement across dentin. In the absence of any exogenous pressure, all cavities exhibited an outward fluid flow rate of 0.36 microliters min-1 cm-2. As exogenous pressure was applied to the cavity, the outward flow slowed. The exogenous pressure that stopped outward fluid flow was taken to be equal to normal pulpal tissue pressure. The mean value was 14.1 cm H2O in five teeth. This simple method permits measurement of dentinal fluid flux, the hydraulic conductance of dentin, and estimates pulpal tissue pressure.
Adolescent↗
Marginal adaptation and seal of direct and indirect Class II composite resin restorations: an in vitro evaluation.
The aim of this in vitro study was to evaluate the marginal adaptation and seal of posterior composite resin restorations made with direct (three-sited multilayering) or indirect (extraoral inlay) techniques. The influence on the marginal quality of the cervical finishing design (butt or beveled) and residual enamel height (0.5, 1.0, and 1.5 mm up to the cementoenamel junction) was also evaluated. This trial was performed on sound, freshly extracted human molars. When residual enamel was less than 1.0 mm in height or 0.5 mm in thickness, indirect restoration resulted in superior marginal quality. For preparations with sufficient residual enamel height (greater than 1.0 mm), beveling of gingival margins appeared mandatory for good adaptation of direct restorations and beneficial to the adaptation of indirect restorations. Residual gingival enamel height and thickness demonstrated an influence on marginal quality only in indirect restorations with butt margins.
Acrylic Resins↗
Bonded to tooth ceramic restorations: in vitro evaluation of the efficiency and failure mode of two modern adhesives.
Dentinal seal and the internal adhesive interface of bonded tooth ceramic overlays were evaluated in vitro, using a dye infiltration test and direct-indirect SEM observations. The new adhesives such as Optibond or Scotchbond MP demonstrated better performances in dentin bonding than former adhesives. With the large cementing space (300 microns), a rigid set-up restraining compensatory phenomena between the restoration and the tooth proved again to negatively influence the dentinal seal of bonded ceramic overlays. In the present test conditions, dentin bonding of the new adhesives remains perfectible, even if the total etch technique is applied. Failure modes of Optibond and Scotchbond MP showed some specific features. For both brands, bonding failures occurred mainly between the hybrid layer and the overlaying resins; these are not of an artefactual nature, as was demonstrated by indirect SEM observations. The cohesiveness of the adhesive interface does not appear optimal at the present time; the need for stress reduction in the cementing space therefore remains of primary concern in dentin bonded restorations.
Ceramics↗
Influence of the restorative technique and new adhesives on the dentin marginal seal and adaptation of resin composite Class II restorations: an in vitro evaluation.
The aim of the present in vitro study was to evaluate the marginal adaptation and seal of direct and indirect (inlay) Class II resin composite restorations made with Z100/Scotchbond MP or Herculite/Optibond. The quality of margins in dentin was assessed for restorations made with or without a lining of glass-ionomer cement or resin-modified glass-ionomer material. The restored teeth were submitted to thermocycling and then to replication for scanning electron microscopic observation and to a dye infiltration test. In the present test conditions, the inlay technique proved its superiority over the direct restorative method. The quality of the dentinal margin of restorations made with Z100/Scotchbond MP appeared also slightly better. Both the glass-ionomer cement and the resin-modified glass-ionomer material, when applied as a lining, increased leakage and downgraded marginal adaptation. The full bonding with modern adhesives appeared to be the most efficient way to enhance the marginal quality of both direct and indirect restorations.
Analysis of Variance↗
Comparison of the color stability of ten new-generation composites: an in vitro study.
OBJECTIVES: The aim of this in vitro study was to evaluate the color stability of modern light-cured composites when subjected to various physico-chemical and staining conditions. METHODS: Ten brands were evaluated including hybrids, microfine hybrids and microfilled composites. Some universal shade samples underwent only staining tests, while others were subjected to one of the following experimental conditions: thermocycling, postcuring, polishing or a 1 wk immersion in saline, prior to staining. The coloring solutions used for the staining tests were: coffee, E 110 food dye, vinegar and erythrosin. A colorimetric evaluation according to the CIE L*a*b* system was performed after experimental periods of 1 and 3 wk. RESULTS: Erythrosin caused the greatest color change for the composites tested. A reduced susceptibility to staining was observed where surfaces had been polished. Low water sorption, a high filler-resin ratio, reduced particle size and hardness, and an optimal filler-matrix coupling system were related to improved composite resistance to discoloration. SIGNIFICANCE: Resistance of modern composites to discolorations still depends on their structure and manipulation.
Absorption↗
[Restoration of the anterior teeth. The principles, indications and limits of the treatment technics].
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Color↗
[Amalgam under suspicion].
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Chemical Phenomena↗
Recent trends in esthetic restorations for posterior teeth.
The increase in the demands made by patients for esthetic or metal-free restorations, together with the ever-growing interest shown by the dental profession for tooth-colored materials and techniques, led to the current development of posterior adhesive restorations. This paper reviews critical elements such as adhesion to dental hard tissues as well as current properties of bases/liners, filling materials, and luting materials. A rationale for the successful use of currently available restorative systems is presented.
Bicuspid↗
[The evaluation of the cytotoxicity of 2 dental adhesives using human pulp cells in culture].
This in vitro study was designed to ascertain the cytotoxicity of two new dentin systems, Scotchbond MP (3M) and A.R.T. Bond (Coltène), on cultured cell monolayers prepared from fresh explants of human pulp tissue and placed in contact with the materials according to two methods. In a direct method, the two components (primer, adhesive) of each bonding system were placed directly on the cell layers. In an indirect method the bonding agents were placed on dentin slices of 0.3 and 1.0 mm thickness, that were interposed between agents and cells. After 8 days the cytotoxicity was quantitatively assessed by counting of the remaining living cells. The results indicate that the different primer solutions, when placed in direct contact with the cells, are more cytotoxic than the adhesive resins. In indirect contact through dentin, both bonding systems exhibited a similar cytotoxicity. The cytotoxicity appeared to be considerably diminished with a thick dentin slice interposed. These data confirm the role of dentin as a diffusion and buffer membrane for bonding materials. This kind of experiment could in the future improve the correlation between in vitro and in vivo results.
Cell Count↗
An in vitro study of parameters related to marginal and internal seal of bonded restorations.
The wall-to-wall contraction of the cementing layer of bonded restorations is compensated for mainly by elastic and plastic tooth substrate-cement deformation but may result in adhesive fracture. Occlusally flattened teeth and corresponding computer-designed onlays, both positioned in a special device, were used to study marginal and internal seal of the adhesive interface with respect to four variables: rigidity of the restoration-substrate setup, cement thickness, adhesive configuration (enamel-dentin ratio and bonding agent), and luting agent. The results of dye infiltration tests revealed the significant influence of the adhesive configuration and rigidity of the setup. A high enamel-dentin ratio, use of a dentinal adhesive on dentinal margins and relative restoration-substrate "mobility" are required to preserve satisfactory marginal seal. However, in the present experimental conditions, no statistically significant differences were found among the diverse cement thicknesses or the luting agents evaluated.
Composite Resins↗
Pharmacokinetics of high-dose etoposide after short-term infusion.
The pharmacokinetics of high-dose etoposide (total dose, 2100 mg/m2 divided into three doses given as 30-min infusions on 3 consecutive days) were studied in ten patients receiving high-dose combination chemotherapy followed by autologous bone marrow transplantation. In addition to etoposide, all subjects received 2 x 60 mg/kg cyclophosphamide and either 6 x 1,000 mg/m2 cytosine arabinoside (ara-C), 300 mg/m2 carmustine (BCNU), or 1,200 mg/m2 carboplatin. Plasma etoposide concentrations were determined by 252Cf plasma desorption mass spectrometry. In all, 27 measurements of kinetics in 10 patients were analyzed. According to graphic analysis, the plasma concentration versus time data for all postinfusion plasma etoposide values were fitted to a biexponential equation. The mean values for the calculated pharmacokinetic parameters were: t1/2 beta, 256 +/- 38 min; mean residence time (MRT), 346 +/- 47 min; AUC, 4,972 +/- 629 micrograms min ml-1 (normalized to a dose of 100 mg/m2); volume of distribution at steady state (Vdss), 6.6 +/- 1.2 l/m2; and clearance (CL), 20.4 +/- 2.4 ml min-1 m-2. A comparison of these values with standard-dose etoposide pharmacokinetics revealed that the distribution and elimination processes were not influenced by the dose over the range tested (70-700 mg/m2). Also, the coadministration of carboplatin did not lead to significant pharmacokinetic alterations. Although plasma etoposide concentrations at the time of bone marrow reinfusion (generally at 30 h after the last etoposide infusion) ranged between 0.57 and 2.39 micrograms/ml, all patients exhibited undelayed hematopoietic reconstitution.
Adult↗