The effect of electrochemical milling on margins of MOD inlays

Marginal fidelity of four methods of swaged metal matrix crown fabrication

The swaged metal matrix provides a method for rapidly making a metal substructure for ceramic crowns. This study determined the vertical and horizontal marginal fidelity of swaged metal substrate crowns made with four methods. No significant difference in vertical or horizontal marginal fidelity was found for metal margin crowns formed with either a plastic spacer or a paint-on die spacer. The vertical marginal fidelity was significantly better in crowns made with a metal margin (37 microns) than in crowns made with a porcelain facial margin (62 microns), and the latter were significantly better than crowns made with a 360-degrees porcelain margin (86 microns). Crowns made with all four methods were overcontoured by 46 to 82 microns. The 360-degrees porcelain margin was technically more difficult and time-consuming to make.

Effect of air abrasives on marginal configurations of porcelain-fused-to-metal alloys: an SEM analysis

Air abrasion of castings for metal ceramic crowns is a routine procedure in ceramics laboratories for cleaning, seating, and preparing casts for porcelain application. This technique can result in damage to the margins of castings. This investigation evaluated the extent and significance of this procedure. Marginal abrasion ranged from 5 to 110 microns. ANOVA, followed by Tukey's post hoc evaluation revealed no difference between abrasives, but significant differences were noted among alloys and margin configurations (p less than 0.05). Marginal loss by alloy was as follows: [Jelenko O] greater than [Olympia = Cameo] greater than [Jelstar] greater than [Genesis II]. Marginal loss by marginal configuration was as follows: [beveled shoulder] greater than [chamfer = shoulder]. Significant marginal damage can occur during air abrasion of dental castings.

The effects of etching on the margins of cast gold restorations

1. Any etching, either chemical or electrical, sufficient to remove an adequate bulk of metal from the tissue surface of a casting will have a measurable and, hence, adverse effect on the margins of the restoration. 2. During any etching process, all margins and contact and occluding surfaces should be protected. 3. For aqua regia etching, Type 2 inlay wax appeared to provide sufficient protection. For electrochemical milling, fingernail polish appeared to provide sufficient protection. 4. Ceramco gold exhibited more resistance to the action of both electrochemical milling and aqua regia etching than did the "C" bridge alloy. 5. Aqua regia etching required more time than electrochemical milling on the two types of gold tested.