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Biomedical subjects

J Holz

Publications and source records attributed to J Holz.

At least 55 records · Page 3Linked to original sources
PubMed1990

[Root canal obturation based on Sealapex calcium hydroxide. A clinical and radiological follow-up after 1 year].

To assess the efficiency of a calcium hydroxide containing root canal sealer (Sealapex), 227 obturated canals were examined clinically and radiologically after one year. When compared to a previously published study (Verdon & Holz 1988), the results show a decline of radiopacity within the canals and an almost complete resorption of the cement overfillings. It was also noted a slight improvement in the radiologic appearance of the periapical lesions.

Calcium Hydroxide↗
PubMed1989

The effectiveness of different endodontic irrigation procedures on the removal of the smear layer: a scanning electron microscopic study.

To compare the effectiveness of different irrigation procedures on the removal of the smear layer, 40 curved canals were manually prepared in vitro under copious irrigation with 3 per cent NaOCl. Ten canals served as controls. The remaining 30 were equally distributed in three experimental groups and subsequently irrigated with the following: ultrasound with NaOCl; EDTA; ultrasound with EDTA. In the scanning electron microscope, the appearance of the smear layer was rated over the distribution of dentinal tubule openings for the coronal, middle and apical segments of the canals. Irrigation with NaOCl produced consistently smeared surfaces. Ultrasonic stirring of NaOCl removed the smear layer moderately, while EDTA produced almost smear-free surfaces. Ultrasound in association with EDTA did not enhance the dissolving capability of this chelating agent. A definite decline in the efficiency of the irrigation procedures was also observed along the apical part of the canals.

Dentin↗
PubMed1989

[Dental adhesive and sealing products submitted to biological in vivo control].

To assess the biocompatibility of 5 dental materials (Gluma, Scotchbond Light Cured, Fuji Type II, Aquacem and Dual Cement), 40 standardized class V restorations were repaired in vivo in human premolars due to be extracted for orthodontic purposes. Histological observation revealed that Gluma, Scotchbond Light Cured and Fuji Type II were eliciting "slight" to "severe" pulpal responses alongside altered odontoblastic layers and inhibited dentinogenesis. These alterations were observed after periods up to 50 days. Aquacem and Dual Cement elicited "moderate" to "severe" reactions. From these results it is concluded on the one hand that the tested products should not be placed without the systematic interposition of a calcium hydroxide liner and on the other hand that the luting agents Aquacem and Dual Cement should not be used on vital teeth.

Adolescent↗
PubMed1989

[Substitute model of an in-vitro biological trials. I. Standardized method using human pulp cells].

To ascertain the biocompatibility of dental materials, an in vitro biological test using cultures of human pulp cells was designed as an alternative to the in vivo method using human teeth. The cells were cultured from fresh explants of pulp germs and the 4th generation of cells (P4) was shown to be very similar to the controls. The comparison between the results of the in vitro cell cultures (obtained by rating the cells' growth and the histomorphology) and those of the controls (histologic rating of the pulpal response) indicated that the developed cell culture method was suitable for the preliminary evaluation of pulpal protective materials.

Biocompatible Materials↗
PubMed1989

[Substitute model for in-vitro biological testing. II. Quantitative evaluation of the biocompatibility of dental products].

A biological model for evaluating pulpo-dentinal capping materials is described. The model uses cultures of human pulp cells which are explanted to form cell monolayers. Four products already tested in vivo on teeth subsequently extracted for orthodontic reasons were laid directly over these cultures and observed after 7, 14, 21 and 28 days, corresponded to the in vivo test periods. The growth and morphology of the cells were similar for both test systems, indicating comparability between the two biological models as well as the validity of the developed in vitro method. A preliminary scale of biological activity is proposed which could be useful for preliminary screening of materials.

Biocompatible Materials↗
PubMed1989

[Clinical and radiologic follow-up of coronal restoration with a standard radicular retainer].

The purpose of this study was to assess clinically and radiographically at mid-term the anchoring of custom posts in flat and curved roots. The results were compared to those of a similar study done in vitro (Brustlein-Rathle et al. 1988). 342 root canals from 143 premolars and molars were treated with standardized procedures by undergraduate students at the "Section de Médecine dentaire" of the University of Geneva. The results, which corroborated the above-mentioned in vitro observations, confirmed that the endodontic preparation as well as the canal widening for the post insertion straightens and thins the canal walls in 60% of the round and curved roots and in 25% of the flat and curved roots, also named root at risk. The study also demonstrated the difficulties of estimating and visualizing radiographically the weakening and possible cracks within the root wall because of radicular and osseous radiographic superimposition.

Bicuspid↗
PubMed1988

[Action of a CO2 laser on dental tissues].

In order to investigate the effect of a CO2 laser on dental tissues, 51 healthy human teeth were lased and prepared for macroscopic, histological and SEM examination using standardized methods. The alterations induced by the thermic shock varied according to the tissue's composition and the lasing's intensity. The effects generally appeared as cracks with fragmentation of the superficial enamel, and a carbonization of the cavity. The underlying pulp showed a disintegration of the odontoblastic layer and an oedema, the severity of which depended on the residual dentinal thickness and the lasing's intensity. The study's results, divergent from those often found promising in the abundant literature, bring to light the biological incompatibility of this type of hard laser regarding the dental organ and suggest caution concerning eventual therapeutic indications.

Adolescent↗
PubMed1986

Clinical evaluation of four amalgam alloys: a five-year report.

In this study 96 teeth of 12 patients were restored with either the conventional alloy Premix, the blended non-gamma 2 amalgam Dispersalloy, or one of the spherical alloys Sybraloy and Tytin. To ascertain an objective comparison of the clinical performance of these alloys, two different alloys were used in each of at least two dental arch quadrants in the same patient and consequently were placed in the same oral environment. Clinical performance of the restorations was evaluated by macrophotography and scanning electron microphotography of replicas made after placement and 2, 3, and 5 years thereafter. Standard criteria were used for the evaluation of anatomic form, surface condition, and marginal adaptation of the fillings. In addition, the filling-enamel interface was assessed from the microphotographs. The three high-copper alloys performed better clinically than the conventional alloy, and the spherical alloys had the best qualifications. In addition to visual examination and photographic evaluation of restorations, the micrometric assessment of replica photographs from the scanning electron microscope may render clinical trials of amalgam alloys measurable and less subjective.

Chemical Phenomena↗