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Biomedical subjects

J Holz

Publications and source records attributed to J Holz.

At least 37 records · Page 2Linked to original sources
PubMed1992

Influence of a new experimental bonding agent on marginal seal of Class V restorations: an in-vitro study.

The performance of a new experimental dentin bonding agent (A.R.T. Bond) was evaluated in vitro. Its influence on the marginal seal of mixed class V restorations made on freshly extracted third molars, using 7 different restoration techniques was studied. When using the new dentin bonding agent, the results of the dye penetration test revealed the least dentinal leakage with the direct inlay technique. Dye penetration scores of bulk and incrementally placed restorations were higher, but not significantly different from the direct inlay. The absence of the dentin bonding agent in incrementally placed restorations resulted in significantly higher leakage values.

Dental Bonding↗
PubMed1992

In vitro evaluation of marginal fit and morphology of fired ceramic inlays.

The marginal adaptation of fired ceramic inlays prepared by three dental technicians in two ceramic materials was evaluated in vitro. The thickness of the sealing gap varied between 46.4 and 57.6 microns, and the percentage of marginal ceramic defects ranged between 8.6% and 25.0% of the total inlay circumference. The incidence of marginal defects increased in areas of complex occlusal morphology. Differences observed in inlay adaptation were related to the technician rather than to the material used. The accuracy of ceramic inlays was comparable to that of metallic and porcelain-fused-to-metal crowns with butt-joint margins and fell within the range of clinically acceptable adaptation.

Aluminum Oxide↗
PubMed1992

[A microscopic evaluation of the marginal adaptation of onlays in gold].

The aim of this in vitro trial was to evaluate the marginal seal and adaptation of gold onlays according to the instrumentation used to prepare the bevels, the quality of margins (as cast vs. polished in the laboratory) and two different finishing procedures (burnishing during or after setting of the cement). For that purpose, 25 freshly extracted human molars were restored with onlays using standardized preparation and fabrication methods. The marginal adaptation of the cemented onlays was evaluated using replicas and scanning electron microscopy. The marginal seal was evaluated on sample sections after a dye infiltration test. In order to improve the marginal fit of gold onlay restorations, it can be recommended to: use diamond burs (Intensiv no. 32 and 37) to prepare the bevels finish and polish restorations in the laboratory except for areas with access to clinically burnish, and polish the margins after setting of the cement.

Crowns↗
PubMed1991

[The in vitro testing of the sensitivity of human cryopreserved pulp cells].

The purpose of this in vitro study was to evaluate the sensibility of frozen human pulp cells, in order to examine the cytotoxicity of dental products. The cell cultures and the biological assessments, using still incomplete human premolars and pulp germs, were achieved according to a standardized method. The sensibility of frozen cells was assessed by comparison of cell reactions before and after 1, 3 and 6 months of congelation, for two dental products called Aquacem and Pulpdent, the cytotoxicity and biocompatibility of which were further confirmed. The behaviour of cells with and without congelation was microscopically evaluated, the growth and morphology of cells were assessed after 7, 14, 21 and 28 days. The comparison of the results showed a similar behaviour between cells with and without congelation, except for few cell alterations in the form of granula which occurred during a short period, probably due to the congelation process. This cell liability offers the opportunity to elaborate a bank of cells available on demand for preliminary cytotoxicity assessments.

Acrylic Resins↗
PubMed1991

[The aging of the human pulp-dentin organ].

239 noncarious human teeth, freshly extracted (from patients aged 10 to 78 years), were prepared in order to examine microscopically the effects of aging on the pulp-dentinal complex at crown and root level. Microscopical observations included the following elements: predentin, odontoblastic layer with capillaries, pulpal volume, fibro-dentin, collagen fibres, blood vessels, cells and pulpal calcifications. Results showed a gradual narrowing of the circumference of the pulp volume with increasing age, due to the continual apposition of dentin. Dystrophic or degenerating calcifications were also noted alongside compression of collagen fibres (giving an appearance of fibrosis). However, the radicular vascularisation is still effective by observing the persistence of an anabolic activity (fibrodentin apposition) at these levels. These findings demonstrate the physiologic and the pathologic evolution of the pulp-dentinal complex.

Adolescent↗
PubMed1991

[A model of an in vitro biological assay controlled by immunofluorescence and scanning electron microscopy].

This study was designed to complete the cell culture test for the cytotoxicity assessment of dental material presented by Christen et al. (1989) and Regad et al. (1989). Two liner materials were selected for this experiment which had already been subjected to both in vivo and in vitro tests. After 2, 7 and 14 days of contact with the test materials, the cell responses were evaluated under the light microscope by their growth pattern and morphological aspects. Cell synthesis of fibronectin and type I and III collagen was studied by immunofluorescence. Surface appearance of the cells in contact with the materials as well as their structures were observed by scanning electron microscopy. This study confirmed the viability of the in vitro cytotoxicity assessment methods with cell cultures. The results also demonstrated the potentials of this method in the early screening of dental materials for their biological compatibility.

Acrylic Resins↗
PubMed1991

[Canal obturation with the Ti-Flex cone. An in vitro trial of its tightness and its adaptation].

To compare, in vitro, the seal of Ti-Flex and GP cone obturations, to verify the adaptation of the Ti-Flex cone inside the obturated canal and to evaluate the density of the sealer material, eighty-two canals of freshly extracted teeth were manually prepared and obturated with corresponding Ti-Flex cones and with single GP cones. After dye infiltration the roots were transversally sectioned. On the first 5 apical sections (i.e. 3-5 mm from apex), the Ti-Flex obturations presented significantly more leakage than the GP obturations since no cones but only the sealer obturated these sections. The Ti-Flex cones appeared adapted to the walls in the apical and median segments of the canals. The density of the sealer in the Ti-Flex obturations was judged satisfactory in most of the specimens. The seal and adaptation defects of the Ti-Flex demonstrated in this study could be balanced by the limited effect of straightening the canal and thinning its dentinal wall of this anchoring system.

Evaluation Studies as Topic↗
PubMed1991

[An in vitro trial of the chemomechanical treatment of root caries: the Caridex system].

This study was aimed to verify the debridement potential of the Caridex system against radicular cervical caries. 14 freshly extracted teeth with cervical caries were split and the fragments were freed from the dentinal caries using three methods: root planning (with a white stone), conventional excavation with a bur (tungsten) and the Caridex system. The results show that the Caridex system can partially dissolve the decayed dentin but leaves behind smeared surfaces as well as part of dentin infiltrated by bacteria. The root planning treatment smears the dentinal surface and thus blocks the tubules which also appeared to be infiltrated with bacteria. The excavation method allowed for a complete elimination of the decayed dentinal tissue down to the hypermineralized zone.

Dental Caries↗
PubMed1991

[Fissure caries: the correlation of clinical and radiological data].

The goal of this research was to evaluate the conventional means of clinical (mirror and probe examination) and radiological diagnosis (bitewing radiographs) of occlusal caries of first permanent molars during the post eruptive period. These teeth showed colored or non-colored fissures, and none of them had conservative or preventive obturations, or dentinal caries. Four experienced dentists independently evaluated the trials, diagnosed the lesions and advised a treatment. The effective lesions were shown by opening minimal preventive cavities, which were then obturated with amalgam. The results showed the lack of precision for the early diagnostic means of initial pit- and fissures-caries, and differences and errors of evaluation performed by the dental professional with respect to their diagnosis and proposed therapeutic choice. The effective lesions demonstrated the high incidence of pit- and fissure-caries in permanent molars during the post eruptive period.

Adolescent↗
PubMed1990

[6 dentin adhesive products subjected to controls in vitro].

The aim of this in vitro study was to assess of the biocompatibility of 6 adhesive dental products (Cavalite, Dual Cement, Fuji Type II, Gluma, Ketac Bond, Scotch Bond) using cell cultures of human pulps and a standardized method. It was thus possible to improve the scale of biological activity proposed by Regad et al., (1989). The specific behaviour of the cells in the contact and adjacent zones has been added to the assessment of the cellular reactions of the whole culture. These criteria allowed the clear differentiation of the toxicity and the biocompatibility of the products. The following estimations were made: Gluma and Fuji Type II "toxic", Cavalite "acceptable", Scotch Bond "not significant", Ketac bond and Dual Cement "acceptable" and "not significant" with a "toxic" tendency.

Acrylic Resins↗
PubMed1990

In vitro resistance to fracture of porcelain inlays bonded to tooth.

To assess the resistance to fracture of ceramic inlays, extracted sound human molars were restored with different ceramic materials and glass-ionomer or composite resin luting cement. Compression forces were applied to the specimens until they fractured, and maximal force developed, extent and location of fractures, and the micromorphology of the fractured surfaces were studied. Inlays made of Vitadur N with aluminum oxide profile and bonded with composite resin demonstrated the highest resistance among the restorative combinations, but their resistance was still lower than that of intact (control) teeth. The extent of fracture increased proportionally to the fracture resistance of the specimens. Scanning electron microscopic observation confirmed the effectiveness of the adhesion between composite resin and etched ceramic and the absence of sufficient micromechanical anchoring between glass-ionomer cement and etched ceramic.

Cementation↗
PubMed1990

A clinical trial of four light-curing posterior composite resins: two-year report.

A 2-year study of the clinical performance of four posterior composite resins used for Class I and Class II restorations is reported. Seventy-seven obturations were reviewed from the patients selected for a previous 9-month study. Obturations were assessed macrophotographically and by scanning electron microscopic evaluation of marginal quality. The 2-year results were compared to those obtained at 9 months. The macrophotographic evaluation revealed a satisfactory clinical appearance in the majority of restorations. However, scanning electron micrographic observations demonstrated that moderate-to-medium marginal degradation occurred during the first 2 years of clinical service. Therefore the use of the products under investigation should be limited to selected cases in which esthetics is of primary concern.

Acrylic Resins↗
PubMed1990

[Cervical wedge-shaped lacunae and dentin hypersensitivity--a histological and SEM study].

The purpose of this study was to establish a correlation between dentinal hypersensitivity and tissular modifications of the pulp-dentinal complex at the level of cervical abrasions. 65 freshly extracted human teeth (from patients aged 20 to 80 years) presenting cervical abrasions without carious lesions were prepared in order to be examined histologically (31 teeth) and by scanning electron microscopy (34 teeth). Open tubules were present on the abraded surfaces in 83.3% of the specimens with presence of cytoplasmic processes in 78.46% of the cases without any correlation with tooth age and depth of the abrasions. The sensitivity could be partially explained by the persistence of cervical dentinal permeability. This permeable dentin seems to be susceptible to mechanical, chemical and bacterial irritations, no matter how thick the reactional dentin is. In the absence of any reliable and biological product capable to seal efficiently the open tubules, only nonabrasive hygiene methods can preserve the integrity of cervical dental tissues.

Adult↗