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Objective: The purpose of the present study was to compare ethylenediaminetetraacetic acid conditioning and phosphoric acid conditioning of dentin in combination with two principally different commercial dentin bonding systems., Method and Materials: Twenty-one extracted human third molars were used. All teeth were caries free, and no teeth were root filled. In total, 29 pairs of dentin surfaces were obtained from 21 teeth. One dentin surface in each pair was etched with a 32% phosphoric acid gel for 15 seconds, and the opposite surface was etched with a 24% ethylenediaminetetraacetic acid gel for 3 minutes. One experimental group of 15 dentin surface pairs was subsequently bonded with All-Bond 2, a two-component system, and the other group of 14 pairs was bonded with Prime & Bond NT, a one-bottle adhesive. A flowable resin composite was inserted in the experimental cavity and light cured. Shear bond strength testing was performed according to the protocol of the International Organization for Standardization., Results: The combination of conditioning with ethylenediaminetetraacetic acid and bonding with All-Bond 2 was significantly better than all other combinations, providing a shear bond strength that was 61% to 123% greater., Conclusion: Use of ethylenediaminetetraacetic acid in combination with All-Bond 2 resulted in a significantly greater bond strength to dentin than did conventional acid etching.

The accuracy of rubber impression materials was evaluated by taking impressions of a steel model, pouring it with stone and comparing certain measurements between steel and stone models. It is assumed that acceptance is achieved when the difference in measurements is within permissible limits, defined by clinical criteria. A mathematical formulation of these criteria will lead to the concept of probability of acceptance. The probability is affected when the limits are changed. The particular case of satisfying two acceptance criteria that contain variables which are not statistically independent is considered, leading to the application of the bivariate normal distribution in the evaluation of acceptance probability.

Residual strains are important for dimensional accuracy of impression materials. When these strains are being calculated, knowledge of thermophysical constants is needed. This paper describes determination of thermal diffusivity, thermal conductivity, specific heat, heat of polymerization rate, and total heat of polymerization. The first two constants mentioned were obtained from an experiment in which transient heat conductivity was studied. The evaluation was based on an analytical solution of this problem. The remaining constants were derived by means of standard differential scanning calorimetry, DSC. Results from accurate, cost-efficient methods are given for three silicones and one polyether.

Retentive strength of the metal-composite interface was studied with tensile tests for 10-mm and 4-mm diameter specimens. In both series nonperforated and perforated metal surfaces with various numbers of holes were used. The specimens were tested after 1 day of storage in air and after thermocycling in water at 7 degrees C and 60 degrees C, respectively. The nonperforated specimens had the highest retentive strength values for both small and large specimens. The retentive strength decreased with increasing number of perforations and for nonperforated specimens with large retentive area. Thermocycling reduced the tensile force required to break the specimens by 4% to 50%. The fracture surface was mostly located close to the metal surface, indicating that this is the zone of stress concentration. With increasing length of the bond edge a reduction of the retentive strength was observed.