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At least 919 records · Page 51Linked to original sources
PubMedDate not supplied

Fracture resistance of teeth with Class 2 silver amalgam, posterior composite, and glass cermet restorations.

This article reports the fracture resistance of maxillary premolars in which ideal class 2 mesio-occlusal or disto-occlusal cavities were prepared and restored with silver amalgam, posterior composite, and glass cermet. Sound teeth and teeth with prepared but unrestored cavities were also studied for comparison. Dentin-bonded posterior composite resin produced the best tooth fracture resistance, followed by glass cermet, intact teeth, silver amalgam, and unrestored-prepared teeth, in that order.

Composite Resins↗
PubMed1989

[Normalizing method for determining the mode of crack-propagation in amalgams and composite resins].

A normalizing method for determining the mode of crack-propagation in a phase or component of a dental amalgam or composite resin was devised. The results calculated using the method were found to be satisfactory when the method was applied to the materials. Furthermore, details of the mode of crack-propagation in the materials which cannot be seen using pictures of the cross-section structure of the materials are revealed using the method.

Composite Resins↗
PubMed1989

[Optical and scanning electron microscope study of gingival microleakage in Class II composite restorations].

It has been studied the gingival microleakage and the polymerization contraction gap in composites class II restorations. The influence of two different composites, a microparticle [Heliomolar (Vivadent)] and a high filled one [P-50 (3M)], has been compared with different adhesion systems: a) gingival enamel acid-etch technique. b) Dentinal adhesives [Gluma (Bayer) and Scotchbond 2 (3M)]. c) A adhesive varnish [Dentin Protector (Vivadent)]. The gingival microleakage is only prevented when a microparticle composite [Heliomolar (Vivadent)] and a adhesive varnish [Dentin Protector (Vivadent)] are used together.

Acid Etching, Dental↗
PubMed1989

[Effect of surface treatment and thermal stress on the adaptation of Germadent amalgam fillings].

Surfaces of amalgam-fillings (Germadent) applied to extracted human teeth were treated in four variants. The adaptation of the fillings to the cavosurface margins was measured with SEM before and after thermal stress. Burnishing lead to a clear reduction of leakages, in contrast to carving. Fillings polished after carving, and especially after burnishing, have smallest marginal leakage. Thermal charges cause a small deterioration of marginal adaptation.

Alloys↗
PubMed1989

[Marginal gaps of combined composite and glass ionomer cement fillings in different preparations in vitro].

In 34 extracted molars with class V cavities (coronal margin in the enamel, apical margin in the dentin) a shoulder or a shoulder with bevel were prepared on the apical aspect. The dentin was covered with glass ionomer cement (GIC) and after beveling the neighboring enamel composite material was applied on top with enamel etching. 24 other cavities filled with either composite or glass ionomer cement served as controls. The specimen were exposed to 2000 alternating thermal tests (1 min. at 8 degrees C, 1 min at 60 degrees C) and alternations of the filling margins were recorded quantitatively using replicas in the SEM. After the alternating thermal tests GIC controls showed statistically significant better margin in enamel and dentin with shoulder preparations alone than the combined or pure composite fillings. Combined fillings with beveled apical cavity margins were superior to shoulder preparations alone. Glass ionomer cement seems to be better for the treatment of class V cavities in terms of margin tightness than composite alone or in combination.

Composite Resins↗
PubMed1989

[Flexural strength tests of repaired amalgam specimen].

Test results of four types of alloys: Flexural strength declined significantly with increasing age of the specimen, however, differently for the tested alloys. The increase in mercury content of the repair amalgam did not influence flexural strength. The combination of materials with each other demonstrated that none of the amalgams was particularly suitable as a repair amalgam.

Dental Alloys↗
PubMed1989

[Risks and benefits of polymeric inlays].

Class I inlays were produced according to the direct method using six white light-cured composite, one inlay material and one veneer acrylic. They were subjected to extraoral heat treatment at 125 degrees C for 150 s. In addition, heat-cured inlays were produced according to the indirect method. In all cases heat treatment resulted in a considerable increase in transverse strength and modulus of elasticity as well as a material specific decrease in the specimen volume between 0.15% and 1.05%, and it facilitated finishing. With one exception heat-treated and heat-cured inlays could be inserted without open margins; even 5000 threshold load cycles of 500 N failed to cause marginal defects. However, these inlays also had no open margins when inserted without previous heat treatment. While in the case of four materials this resulted in no measurable reduction in fatigue strength, it reduced this value to a maximum of 100 N in three materials. Swelling of the polymeric inlays due to high water absorption resulted in extensive enamel cracks with one of the materials tested.

Acrylic Resins↗
PubMed1989

[Fatigue strength and marginal adaptation of composite fillings].

Threshold load tests have shown that the fatigue strength of Class I composite fillings may be increased up to 150 N by the application of a base material. This effect varied only with the consistency of the composite, not with the type of base material used. However, differences were found in the depths at which losses of marginal adaptation occurred: where glass ionomer cement base (polyalkenoate) was used, marginal leakage demonstrated by pigment penetration tests stopped at the interface between filling and base, while in those cases where phosphate cement was used as base material, pigment penetration was shown to extend down to the floor of the cavity. Mesiodistal sections through Class II MOD restorations with the same combinations of materials after 24 hours of storage in pigment solutions and without loading revealed that a close marginal fit in the area of the cervical step can be obtained with the use of glass ionomer cement as base material. In contrast to this observation the use of phosphate cement as base material is associated with marginal leakage down to the area of the floor of the cavity in about one half of the restorations.

Composite Resins↗
PubMed1989

[In vitro studies on the quality of proximal margins of Cermet fillings in posterior teeth].

Since Cerment-cement has been recommended also for Black's Class II cavities in posterior teeth, it was the goal of this study to compare its marginal adaptation with that of amalgam after alternating thermal loads. Black's Class II cavities were prepared in extracted premolar teeth and filled with amalgam or Cermet. Three different application techniques were used for the Cermet fillings: 1. syringe only, 2. syringe and amalgam plugger, 3. individual occlusal plugger. Before and after alternating thermal loads the proximal margins were studied by SEM using replicas. The poorest results were found in the Cermet fillings applied with the syringe only. In the other three groups the results were comparable. These findings suggest that cermet cement should not be applied with exclusive use of the syringe, but should always be additionally adapted with a plugger.

Bicuspid↗
PubMed1989

[Alternative filling methods for premolars and molars].

Extensive research and development work produced tooth-colored filling materials for premolars and molars which, although their indications are limited, provide for satisfactory treatment of cavities. But on account of their special properties these materials are unlikely to replace amalgam altogether. This would need products of a different nature. Currently available materials are at best complementary, but cannot be regarded as a true alternative.

Bicuspid↗
PubMedDate not supplied

Mechanical resistance of extensive amalgam "restorations" anchored with the aid of threaded pins and amalgapins.

This study dealt with laboratory tests (oblique force application of 45 degrees to check the fracture strength), in order to compare two types of dentin pins: threaded metallic TMS Whaledent pins and amalgapins. It was used multiple number of these elements, with or without thermal cycling. The statistical analysis has indicated a highly significance difference between these pins, where the amalgapins provide to be more efficient than the steel one. As the resistance with the use of 3 or 4 amalgapins are similar, is up to the professional to choose the number of pins. It was also observed that the use of 2 or 3 steel pins had the same results. In this study it was observed that almost all of the specimens were able to resist to oblique load of more than 70 kgf. This value is higher than any force occurring in the mouth (HELKINO & INGERVALL 10). Hence, the results in vitro indicate that extensive amalgam restorations may well work in the oral cavity. Clinical studies must be conducted in order to check if really these mastication, since it is practically impossible to duplicate these natural condition in a laboratory environment.

Dental Amalgam↗