Nonprecious metal alloys for fixed restorative dentistry

Non-noble alloys are available for use in the fabrication of cast restorations. These alloys are not necessarily designed for subsequent application of porcelain. Because they are promoted for use in place of the traditional gold alloys, significant changes in technique and armamentarium are necessary. Casting of acceptable clinical quality can be obtained, but not without additional equipment and personnel training. Obtaining casting of gold alloy quality on a routine basis may not be easily achieved. Casting into detail is possible (see Fig. 5), although greater surface roughness of the casting may be observed with the non-noble alloys. A high polish is possible (Fig. 6), however technicians and clinicians accustomed to and expert in polishing single or multiple gold alloy castings will require time and training to adjust to the somewhat more difficult and time-consuming techniques required in the polishing of non-noble alloys. Well fitting castings of the non-noble alloys require investments capable of greater thermal and/or hygroscopic expansion. The solidification shrinkage in non-noble alloys is greater than that of gold alloys. The clinician may find casting of these alloys to be "tight-fitting" on insertion. At present, because additional time and armamentarioum may be required, laboratory fees for the non-noble metal casting may not be any more economical than those of cast gold alloys. Therefore, the clinician and patient may benefit little with regard to reduced fees for restorations constructed of these alloys. In conclusion, the non-noble metals may find increased use in fixed restorative dentistry as expertise develops to the level at which usage of these products becomes routine. These is still considerable clinical information needed as to the durability and corrosion resistance of these alloys. Some work has been work has been done on the corrosion of these alloys, but much data remains to be obtained. Soldering these alloys is difficult and requires training of the technician in the required usage of special solders. The following facts should be considered in casting and finishing non-noble alloys for single and multiple unit casting in dentistry. 1. Silicate or phosphate bonding investments are required. 2. Recognition of proper casting appearance of the molten alloy is essential. 3. Additional armamentarium is required to obtain casting temperatures necessary. 4. Polishing procedures are more laborious and require harder abrasives. 5...