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Biomedical subjects

D Dietschi

Publications and source records attributed to D Dietschi.

At least 37 records · Page 2Linked to original sources
PubMed1995

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↗
PubMed1995

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↗
PubMed1995

Free-hand composite resin restorations: a key to anterior aesthetics.

The success of free-hand bonding in anterior teeth depends on a harmonious integration of various elements, including a thorough understanding of natural function, aesthetics, characteristics of current materials, and restorative techniques. The selection of composite brands which offer a variety of shades and provide several opacities is mandatory. By utilizing an anatomic stratification with successive layers of dentin, enamel, and incisal composite, a natural-appearing aesthetic result can be achieved in a relatively simple and predictable manner. Attentive use of finishing methods is still necessary for surface quality and natural appearance of the final restoration. Direct composite bonding remains an adequate therapeutic modality in traditional Class III to Class V and localized cosmetic restorations. It can satisfy most aesthetic demands, and it offers an affordable alternative to more invasive procedures, such as veneers and crowns. The learning objective of this article is to review anterior free-hand bonding utilizing composite restorative materials.

Composite Resins↗
PubMed1994

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↗
PubMed1994

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↗
PubMed1993

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↗
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↗
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↗
PubMedDate not supplied

Indications and potential of bonded metal-ceramic fixed partial dentures.

Recent progress in restorative dentistry has dramatically modified contemporary treatment concepts, which are typified by the preservation of healthy tissues, recognition of aesthetic expectations, and the search for simplified prosthetic solutions. While this shift in focus has justified the increasing interest in implantology, it has also resulted in the expansion of adhesive and conservative treatment options. This article reviews the various means available to replace missing anterior teeth, as well as the periodontal and surgical procedures that are associated with the optimization of biological, functional, and aesthetic results.

Ceramics↗
PubMedDate not supplied

Marginal and internal adaptation of stratified compomer-composite Class II restorations.

Different approaches have been proposed to improve the adaptation of Class II restorations, including applying low-elasticity modulus base liners. This in vitro fatigue test (or study) evaluated the influence of the compomer base-lining configuration on restoration adaptation. Direct Class II MOD box-shaped composite restorations with or without base and lining (n=3x8) were placed on intact human third molars with proximal margins 1 mm above or under the CEJ. The compomer (Dyract) was applied as a 1 mm-thick lining or as a base, closing proximo-gingival margins. Marginal adaptation was assessed before and after each phase of mechanical loading (250,000 cycles at 50N, 250,000 cycles at 75N and 500,000 cycles at 100N); internal adaptation was evaluated after test completion. Gold-sputtered resin replicas were observed in the SEM and restoration quality evaluated in percentages of continuity (C) at the margins and within the internal interface after sample section. Mechanical loading did not influence adaptation to enamel, while it adversely affected restoration adaptation to dentin for the full composite and compomer-base restorations (C varied, respectively, from 95.2 to 75.3% and from 98.0 to 10.6%). The internal adaptation quality showed the same general trend, however, with reduced scores of continuity. In this experimental condition, application of a low elasticity modulus layer under the restorative material proved advantageous but the compomer should not contact the gingival margins.

Bisphenol A-Glycidyl Methacrylate↗