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Biomedical subjects

D Nathanson

Publications and source records attributed to D Nathanson.

At least 19 recordsLinked to original sources
PubMed2001

Reduced dental plaque accumulation on composite gold alloy margins.

Restoration of tooth surfaces with materials that inhibit formation of heavy bacterial plaque accumulations could be important in the treatment of patients with existing oral disease or in reducing the likelihood for periodontal disease. Captek is a dental gold composite material used to produce copings for ceramometal restorations that has been reported to inhibit plaque accumulation. In this study, the oral bacteria of nine periodontally healthy subjects with a total of 42 gold composite copings were sampled. Contralateral teeth with normal tooth surfaces were also sampled as controls. The quantitative presence of forty bacteria was determined in each sample by DNA:DNA hybridization. The results indicated that the porcelain/gold composite alloy coping surfaces had significantly fewer bacteria than the control normal tooth surfaces (71% reduction). The percentage composition, however, did not differ significantly between surfaces.

Analysis of Variance↗
PubMed2001

Colour stability of a new light-cured ceramic stain system subjected to glazing temperature.

A light-cured ceramic stain system (Orbit LC) offers promise as an effective method for surface characterization of ceramic restorations. This study evaluated colour change after glazing procedures for six commonly used stains from this novel system. One hundred and five ceramic specimens were made of the same enamel porcelain powder and standardized in size. The stains were applied on ceramic blocks and light-cured according to the manufacturer's recommendations. Porcelain colour was then measured with a calibrated colorimeter before and after each glazing procedure. The CIEL*a*b* colour co-ordinates were obtained as a measure of the direction and magnitude of colour change. Colour changes were noted for all six stains when subjected to the first glazing procedure (DeltaE* = 1.25-4.73). Brown, orange and green stains showed the greatest colour shifts (DeltaE* > 3.3), which might be considered clinically significant. However, the colour change is not of the same pattern in the colour space. Compared with the first glazing procedure, the second and third glazing procedures demonstrated less effect on the colour stability of the stains (DeltaE* = 0.36-1.12). The results provide important information about colour shifts in the system, which require overcorrection during stain application.

Analysis of Variance↗
PubMed2000

Computer imaging versus conventional esthetic consultation: a prospective clinical study.

Computer imaging can be helpful in demonstrating to patients the potential outcome of esthetic dental procedures. The current clinical study assesses the effectiveness of computer imaging by comparing the reactions of patient and dentist to conventional consultations versus the use of computer imaging. The responses from 35 subjects show that computer imaging consultations are more effective in helping patients decide to accept treatment. Patient satisfaction was higher (93.75%) with computer consultations than with conventional methods (83.3%). Computer imaging consultations were easier to conduct but significantly (p < .05) more time consuming.

Adult↗
PubMed1999

Compressibility of two polyvinyl siloxane interocclusal record materials and its effect on mounted cast relationships.

STATEMENT OF PROBLEM: Addition silicones (polyvinyl siloxanes) are universally accepted as accurate and stable impression materials. They have also gained popularity as interocclusal record materials. However, it has not been defined if it is possible to work with polyvinyl siloxanes without changing the recorded maxillomandibular relations. PURPOSE: This study examined the compressibility of 2 addition silicones as interocclusal record materials, analyzing the changes of maxillomandibular relations at the condyle region when different compressive forces are used to stabilize articulated casts. MATERIAL AND METHODS: Sixteen interocclusal records, obtained from the same patient (8 of each polyvinyl siloxane, Blu-Mousse, Fast Set), were interposed between the patient casts in a new measuring system obtaining 48 curves of load versus maxillomandibular positional changes in 3 axes (x, y, z). These curves were compared with curves obtained with the casts in maximum intercuspation without interocclusal records (reference curves). Analysis of variance was used to compare maxillomandibular positional changes among the 3 groups (n = 48 each): Blu-Mousse, Fast Set, and control group or maximum intercuspation without interocclusal record. RESULTS: There was no significant change in maxillomandibular relations when forces up to 1 kgf were applied to stabilize the casts related by means of Blu-Mousse and Fast Set addition silicone interocclusal records. CONCLUSION: It is possible to use these polyvinyl siloxanes as interocclusal record materials without changing the recorded maxillomandibular relations.

Analysis of Variance↗
PubMed1999

In vitro stress analyses of dental implants supporting screw-retained and cement-retained prostheses.

A photoelastic and strain gauge analysis was performed to evaluate the stress transferred to implants through the provisional-cement-retained, the permanent-cement-retained, and the screw-retained prostheses. The deflections of the prostheses at the time of the loading were also measured. In the single crown test, the provisional-cement-retained crowns transferred less stress. In the two-unit fixed partial denture test, there were no differences between the three different prostheses. In the two-implant supported distal cantilevered prostheses, the screw-type and the permanent-cement-retained prostheses developed more stress around the apex of both implants. The permanent-cement-retained prostheses acted almost the same as the screw-type.

Birefringence↗
PubMed1998

Splenectomy in a child with chronic Mycobacterium avium complex infection and splenic sequestration.

Mycobacterium avium complex infections (MAC) are being reported with increasing frequency in immunocompromised patients. When these infections become resistant to standard antibiotic therapy, treatment with interferon-gamma (IFN-gamma) can be helpful. Pain, fever, splenic enlargement, and cytopenias caused by splenic sequestration developed during IFN-gamma treatment in a 9-year-old boy and were successfully treated by splenectomy. The development of IFN-gamma-induced splenic sequestration and cytopenias in MAC-infected patients represents a new indication for splenectomy.

Anti-Bacterial Agents↗
PubMed1997

In vitro elution of leachable components from dental sealants.

Recent concerns have been raised about the possibility that estrogenic chemicals, in particular bisphenol-A, or BPA, might be leached out of dental sealants. This study aimed to identify and quantify BPA and other components released from seven light-cured fissure sealants in vitro. None of the tested sealants was shown to have released BPA; however, the investigators identified other eluted components that should be investigated for their biological effects.

Acetonitriles↗
PubMed1997

Vital tooth bleaching: sensitivity and pulpal considerations.

For some patients, sensitivity and discomfort follow vital tooth bleaching. Clinical observations, however, suggest these are reversible episodes with no irreversible long-term effects. Using milder peroxide formulations or gels diminishes postoperative discomfort. The author recommends careful treatment when patients have large restorations, cervical erosion or enamel cracks. Fluoride treatment, sealing restorations and premedication may lessen discomfort.

Animals↗
PubMed1996

Re-entry into the cell cycle is required for bFGF-induced oligodendroglial dedifferentiation and survival.

Remyelination in the CNS following demyelinating disease may be accomplished by surviving mature oligodendrocytes that dedifferentiate, proliferate, migrate, and finally regenerate myelin. We previously reported that basic fibroblast growth factor (bFGF) induces oligodendrocytes in primary mixed glial cultures to dedifferentiate and synthesize DNA (Grinspan et al.: J Neurosci Res 36:672-680, 1993). We now show that this effect is direct and not mediated through the effects of bFGF on other cell types, because we were able to demonstrate similar changes in oligodendrocyte phenotype in enriched oligodendrocyte cultures prepared by immunopanning. The bFGF-induced reversion to the precursor stage of the oligodendroglial lineage can be blocked by agents that inhibit entry to the cell cycle; thus oligodendroglial dedifferentiation is dependent on proliferation. We also report that 2 days of bFGF treatment inhibits oligodendroglial apoptosis. However, when oligodendroglia are prevented from entering the cell cycle in the presence of bFGF, apoptotic cell death is increased. Thus, bFGF induces oligodendroglial dedifferentiation if oligodendroglial DNA synthesis can occur but causes oligodendroglial apoptosis when oligodendroglial DNA synthesis is prevented.

Animals↗
PubMed1996

Effects of titanium on transcriptional and post-transcriptional regulation of fibronectin in human fibroblasts.

The effects of commercially pure titanium (Ti) on the regulation of fibronectin gene expression and synthesis were investigated in early-passage human gingival fibroblasts. The fibroblasts were cultured on 50 nm Ti-coated silicon wafers treated with radio-frequency glow discharge prior to use and on Falcon tissue culture plastic (TCP) dishes as a control. Northern hybridization analysis revealed that fibroblasts cultured on Ti reduced the fibronectin mRNA level by 58% at 16 h, but increased it by 2.6-fold at 90 h, although the cell numbers and house-keeping gene GAPD mRNA levels on these two surfaces were essentially the same. The amount of total RNA was slightly less on the Ti surface. While the total [35S]methionine incorporation was essentially unaltered, the amount of [35S]methionine-labeled fibronectin was significantly increased in cells cultured on a Ti surface in early cultures but decreased in the late cultures. The apparent discrepancy between the increased fibronectin mRNA levels and decreased translation could be explained by a 30% reduction in fibronectin mRNA half life in cells cultured on Ti. The distribution of fibronectin between the medium and the cell layer also was altered on Ti surfaces, with a approximately 100-fold increase of fibronectin assembled in extracellular matrix at 16 h, but a 36% reduction at 90 h. In contrast, the amount of fibronectin recovered in the medium was essentially unchanged. The total amount of protein assembled into the extracellular matrix by cells on Ti increased 2.1-fold at 16 h but decreased by 19% in 90-h cultures. These significant changes in fibronectin gene activity and gene product distribution by cells cultured on Ti surfaces demonstrate that the surface chemistry of biomaterials can selectively regulate the cellular behavior at the molecular level and, conversely, that molecular biological techniques provide sensitive indicators of the molecular biocompatibility of implant materials.

Adult↗
PubMed1996

Reproducibility and condylar position of a physiologic maxillomandibular centric relation in upright and supine body position.

Better understanding of the physiologic features of the masticatory system has led to the evolution of the concept of maxillomandibular centric relation from the mechanical to physiological bases. However, the reproducibility of physiologic methods for centric relation determination has been criticized. In this clinical study the swallowing technique was modified to establish a physiologic centric relation in a reproducible manner. Condylar and disk positioning and reproducibility of the proposed modified swallowing technique (MST) were compared with the same parameters of a traditional technique, namely, the chin point guidance technique (CGT). Both techniques were studied with the patient in the upright and supine positions. Three interocclusal records were obtained for each technique-position combination for each of the 30 patients. The recorded maxillomandibular relations were analyzed on the three-dimensional analyzer. MST positioned the condyles in a more superoanterior position than did CGT, which was interpreted as a better seating of the condyles and disk in the articular fossae. There was no significant difference in reproducibility between MST and CGT on x, y, or z axes (p > 0.05), indicating that it is possible to establish a physiologic centric relation in a reproducible manner. The term "functional centric area" was proposed in this study to define a neuromuscularly determined centric occlusal scheme.

Adult↗
PubMed1995

In vitro shear strength of bonded amalgam cores with and without pins.

This study compared the shear bond strength of resin-bonded amalgam with and without pins. The coronal third of 240 embedded posterior teeth was removed to expose a flat, nonretentive surface. Three Minikin pins were placed in the dentin in a triangular pattern 1 mm apart. Amalgam was condensed into a Delrin mold (4.2 mm in diameter and 3 mm in height) positioned over each tooth. The adhesives Amalgam-bond, All-bond, Amalgambond with high-performance additive, Panavia EX, and Panavia with Photobond were the materials used to bond the amalgam to the dentin. Half of the samples were immersed in normal saline solution for 7 days and the others for 30 days. Shear bond strengths were recorded as the maximum load per cross-sectional area of the bonded surface with a testing machine with 1 kN load cell and crosshead speed of 0.5 mm/min. A three-factor analysis of variance and Student-Newman-Keuls test (p = 0.05) identified Amalgambond with high-performance additive as the strongest adhesive in this study. The use of pins with or without adhesives increased the shear strength of amalgam samples significantly more than samples that used adhesives alone.

Analysis of Variance↗
PubMed1995

Tissue management and retraction technique combined with all-ceramic crowns: case reports.

The need to preserve the gingival health during impression making for laboratory fabricated prostheses has been emphasized in literature and clinical practice. This article presents the placement of all-ceramic crowns utilizing a relatively new soft tissue retraction material, a polymer, cut into 2 mm wide strips. The sponge-like texture of the material expands with moisture and exerts gentle pressure on the gingival tissue, effecting a retraction for impressions. The gingival tissue returns to its original position within 24 hours. The learning objective of this article is to share the experience and observations of this procedure and the materials utilized. Several case reports are presented to illustrate the clinical procedure and the results obtained.

Adult↗
PubMed1994

CAD-CAM ceramic inlays and onlays: using an indirect technique.

A time-sharing technique for a CAD-CAM unit can avoid scheduling difficulties and lengthy appointments. Dentists can also share the cost of expensive equipment and involve staff in learning the steps of this computer-aided design and manufacture.

Cementation↗