Bond strength of metal-ceramic systems in three-point flexure bond test.

This study deals with a three-point flexure test for the metal-ceramic bond involving geometrically simple specimens (alloy strips partly coated with ceramic) that can be fabricated with reasonable expenditure and sufficient reproducibility. The calculation of the stress distribution in such specimens with the aid of the finite-element method (FEM) is presented. The aim of this numerical analysis is: to investigate the stress distribution in a ceramometallic specimen with dimensions that, in a large number of experiments, have proven to lead to debonding at one end of the ceramic veneer instead of a crack in the middle of the veneer; and to assign a bond strength to the measured critical bending force that takes into account the influence of the Young's modulus of the alloy as well as a possible deviation of the thickness of the metal substrate from the standard value.

[Tensile strength of dental porcelains].

Flexural, compressive and tensile strength as well as the modulus of elasticity of 15 different dental ceramics were evaluated. Conventional dental ceramics differed insignificantly in their mechanical properties. By testing new products like Cerec 2 and especially In-Ceram there was found an evident increase in inner strength.

[Nickel release of dental alloys as a function of the pH value of the corrosive solution].

Ni-59-65Cr26-23Mo11-9 alloys released distinctly lower quantities of nickel in lactic acid/saline solutions at pH 2.3, 4.2, or 6.

[Mechanical strength of ceramic materials for fusing on titanium restorations].

Bending, splitting tensile, and bond strengths of four ceramic systems for veneering titanium frameworks as well as the fatigue strength of the complete metal-ceramic crown were evaluated. The mechanical properties of ceramo-metallic systems are comparable with those of conventional dental ceramics. A slight increase in bending, tensile, and bond strengths when using higher firing temperatures was observed, although this did not result in an increased endurance strength of the complete system.

[Nickel solubility and metallic taste].

Main causes for metal taste may be deficiency diseases (especially deficiency of zinc), medication or dental restorations. Saliva of probationers with partial dentures was analyzed for their nickel contents. The solubility behavior in saliva of the alloys studied was related to metal taste and burning sensation.

[Bond between wash elastomers and putty silicones].

Areas of elastomeric impression materials are deformed when impressions are removed from undercuts in the mouth. Bond strength between low and high viscosity impression materials is considered to be higher than the adhesion between impression material and teeth or gum (up to 50 N/cm2). Otherwise failure of impression may be due to failure of the bond between putty and wash elastomers.

[Nickel solubility of dental alloys in the immersions-test and in the mouth].

The nickel solubility of 7 different nickel-alloys was tested in vivo and in vitro. The results revealed that the solubility of the alloys, after encasing them in lactic-acid solution of pH 4.2 for a period of seven days, allows to find out those alloys, which will also clinically dissolve small amounts of ions only.

[Solubility of nickel from dental alloys in saliva].

Dental students in the clinical courses of prosthodontics manufactured maxillary cast partial dentures from 6 nickel-containing alloys according to set guidelines. Prior to insertion as well as up to 7 days after insertion resting saliva samples were collected and analyzed for their nickel contents with the aid of atomic absorption spectrometry (AAS) using a graphite tube. 20 min after insertion the salivary nickel levels were above the blank value.

[Testing the solubility of dental alloys].

Solubility of dental non-precious alloys was investigated. In the first few days of immersion high concentrations of dissolved metal ions were observed. For some alloys the rates increased, for others they decreased with time, when the immersion bath was replaced by a freshly prepared one.

[Corrosion resistance and bond strength of dental alloys].

Investigated Ni-alloys, which showed extensive solubility of Ni particles in corrosion bathes due to DIN 13927, also revealed pronounced lost of bond strength to ceramic veneers when immersed into corrosion bathes of equal constitution. Noble metal alloys with a gold concentration more than 50 percent, however, showed no such large lost of bond strength. Pd alloys showed a lost of bond strength which increased with their Ga concentration.

[Injury-free removal of cemented crowns and bridges].

Seven methods for removing crowns and bridges were studied in in vitro tests. Systems gripping the crowns on both sides led to the best results. Cemented crowns were loosened by ultrasound.

[Compressive strength of metal-ceramic occlusal veneers].

Ceramometallic specimens, circular in section, of varying thickness and manufactured by means of different procedures, have been tested to destruction of the ceramic layer under a once-through continuously increasing force at defined points. Identical specimens were used to determine the number of load cycles under increasing continuous stress of 430 N until the ceramic layer failed. The fatigue strength increased with the thickness of the metallic layer and was further increased by a high inherent strength of the ceramic layer.

[Solubility of dental alloys in saliva].

Five dental probationers each of the clinical courses for prosthodontics manufactured maxillary cast partial dentures from 7 nickel-bearing alloys according to given guidelines. Prior to insertion as well as after 20 min, and in some cases 3 h, resting secretion saliva samples were collected and analyzed for their nickel contents with the aid of atomic absorption spectrometry (AAS) using a graphite tube. Further saliva samples were collected following the insertion of plates inactivated in lactic acid and saline, and after intensive polishing and reinsertion.

[Lightweight construction--sense and nonsense].

Lightweight construction techniques make sense as long as certain basic principles are observed. This requirement is best met by the shell construction technique. Lightweight constructions using the ultralite foil technique have considerable shortcomings, and it is only in rare cases that they may be used on a long-term basis.

[Estimation of usefulness of metal-ceramic restorations].

Many factors are responsible for the quality and the usefulness of the denture: form and dimension of the construction, the distribution of the compound materials in the size, the strength of the compound and the particular materials and their plastic-elastic behaviour, the impact of different manufacturing processes. The paper describes how these factors are influencing one another and presents and discuss testing methods for sampling comparable results. Instructions will be given to the examination of the application of new methods (Ceraplatin*-crown, ceramical faced galvanic crown, metal saving crown and bridge constructions).

First experiences with resin-bonded bridges and splints--a cross-sectional retrospective study, Part II.

This second report establishes that the success of treatment with resin-bonded bridges was dependent upon many factors. Factors controlled by the clinician, such as case selection and treatment planning greatly influence the clinical success. It was possible to show that framework preparation and the amount of available enamel were significant factors, whereas isolation technique, type of retention mechanism and type of adhesive used were of less importance.