Showing papers on "Dental Soldering published in 2002"

Orthodontic soldering techniques: aspects of quality assurance in the dental laboratory.

Abstract: Background: In Germany, the dental technician is required by the Medical Products Act (MPG) to produce workpieces of high safety and quality and to document these properties. Soldering continues to be the prevailing joining technique in the dental laboratory, although problems arise from the susceptibility to corrosion and the low strength of soldered joints. This study aimed to reveal sources of defects in dental laboratory workpieces in order to achieve optimization in terms of quality assurance. Material and Methods: The joints were produced by various dental technicians using three different soldering techniques. These joining techniques were investigated for their quality and their corrosion properties during immersion in ferric chloride, orthodontic appliance cleanser, and artificial saliva. Observance of the soldering instructions by the dental technicians was checked. Corrosion attack was confirmed by scanning electron microscopy and by measuring the ion concentrations of copper, silver and zinc in the corrosive agents, using atomic emission spectroscopy with stimulation by inductively coupled plasma (ICP-AES analysis). Results and Discussion: Incomplete filling of the soldering gap, porosities resulting from the production process, poor corrosion properties, and in particular a high variability of the measured values point to insufficient reliability of two soldering techniques. Variations in quality were also detected among the technicians' modes of operation. Conclusion: The analyses confirm the need for quality assurance of soldering techniques and for increased support for alternative joining techniques such as laser welding in the future. The results of the studies on laser welding are presented in a separate publication.

Radiological examination of dental castings – a review of the method and comparisons of the equipment

Abstract: The mechanical stability of crowns or bridges as well as frameworks for removable partial dentures depends on factors like thickness and metal structure. The biological compatibility can be influenced by porosities and soldered joints. Radiological testing is a non-destructive method to check defects in dental castings. As dental precious metal alloys have high X-ray absorption, testing of high gold alloys should be performed with a suitable X-ray machine at a tube voltage of 120 kV since the X-ray penetration of dental X-ray units using a tube voltage of 70 to 80 kV is not high enough for these alloys. As the absorption of Co-Cr alloys and of titanium is much lower, these materials can be tested with a dental X-ray apparatus. The radiographs show location and size of metal defects. They enable an examination of metal thickness and content of porosities. Metal defects reducing the biological compatibility or cast stability can be detected prior to clinical fitting.