Deutsche zahnarztliche Zeitschrift最新文献

The influence of a disinfectant solution containing glutaraldehyde on the dimensional stability of 2 alginate and 4 elastomeric impression materials has been investigated. Die models were measured using a computer-controlled method and compared to the master die to assess the three-dimensional change in the impression material. After an immersion time of 10 min, a dimensional change did not occur. When using immersion times longer than 10 min, the accuracy of the alginate materials was generally more affected by the disinfecting solution than that of the elastomeric impression materials.

The tensile bond strengths of six different resin-bonding-systems to the aluminium oxide ceramic In-Ceram were tested. The samples were stored in artificial saliva (37 degrees C) up to 150 days and thermocycled (5 degrees-55 degrees C, 18,750 cycles). After sandblasting or silicoating of In-Ceram the tensile bond strength of the modified Bis-GMA resin Panavia-Ex showed no significant changes within this observation period. Using the conventional Bis-GMA resin Microfill-pontic, silicoating In-Ceram with the Rocatec-system resulted in a better bond strength than the use of a silane. The used etching procedure with boiling 70% sulphuric acid was proven to be unsuitable for a long-term stable bond.

29 children aged between 2 and 16 and suffering from fractures of the condylar process were treated by functional appliances, 15 of them received previous intermaxillary wiring. Clinical and radiological reexamination including nuclear magnetic resonance tomography of the TMJ revealed good results for the use of functional appliances without previous immobilization.

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.

Only in a minority of cases do electronic TMJ tracings allow a clear differentiation between arthrogenous dysfunctions. To us, the major application of this recording technique appears to be the diagnosis of dislocations of the articular disk. Because of the great variability of possible dislocation patterns it is mandatory that the interpretation of electronic jaw tracings be standardized to avoid contradictory interpretations and to enhance the validity of this diagnostic tool. In trying to establish reliable, hardware-independent criteria for the evaluation of joint tracings in TMJ dysfunctions, it is the shape of the condylar inclination, the time-correlation of condylar path changes in all three planes and the direction of these changes, that are of utmost diagnostic significance: Repeated recordings of all functional movements are necessary to ensure tracings of high diagnostic value. The diagnostic potential of three-dimensional electronic jaw tracings can be further enhanced by guided jaw movements, e.g. functional compression, which result in characteristic changes of the tracings.

Ni-59-65Cr26-23Mo11-9 alloys released distinctly lower quantities of nickel in lactic acid/saline solutions at pH 2.3, 4.2, or 6.5 than type Ni66-85Cr15-13Mo7-0 alloys for a period of 1 day and, subsequently, periods of 3 days over a total period of 33 days. While nickel solubility was similarly high at pH 2.3 and 4.2 (varying between 0.1 microns/cm2 d and 222 microns/cm2 d depending on the type of alloy), a maximum of 2 microns/cm2 d of nickel dissolved from all tested alloys at a pH value of 6.5.

Dental alloys coated with (Ti,Nb)ON using the ion are PVD technique exhibit galvanic corrosion current densities of considerably less than Jg = 1 microA/cm2. These measurements were taken on plane surfaces. The results show no signs of local corrosion, which might impair the long-term intraoral stability of dental constructions or the health of the patients. Irrespective of the dental alloys used, the coatings exhibit pores extending down to the alloy. The alloy thus wetted on the one hand, and the coated areas on the other, act as galvanic elements with high source resistances and very low short circuit currents. It may therefore be concluded that the coating will effectively reduce allergic reactions to the components of the dental alloys.

The ceramo-metallic bond strength of cast titanium was tested according to DIN draft 13927. While the specimens failed in the bending tests, they clearly passed the 3-point bending test after removal of the surface reaction layer prior to firing. Light microscopy and SEM showed a satisfactory wetting of the titanium surface by the ceramic material. The result of X-ray analyses suggest that titanium particles are retained in the ceramic material when this layer is broken off its metallic substructure.

Chewing forces were measured in a needle point tracing while the patients could view their actual and the proposed chewing forces (5 N, 10 N and 30 N) on a computer screen (biofeedback). Most probands used less than the proposed forces in the experiments. All probands approached the proposed level of force step by step. Fatigue of the chewing muscles led to a change in the Fourier-transformation of the recorded samples: An increase in short-waved components (frequencies of approximately 1 Hz) was found.

Acrylic, plaster and polyether were evaluated for their accuracy in indexing needle point registration. Additionally, a new experimental system was tested, that permits the dentist do immediately verify the accuracy of the recording. Best results were obtained when the indexes were not removed from the occlusal plane plates. When the indexes were dislodged, acrylic and plaster demonstrated the most accurate results in repositioning the occlusal plane plates. The experimental system demonstrated comparable accuracy to both, acrylic and plaster.