Edge-bevel fracture resistance of three direct-filling materials.

Edge strength is defined in this study as the resistance to fracture of the beveled extension normally located at the cavosurface margin of a dental restoration. The edge strength of direct-filling alloy restorations plays an important role in maintaining the integrity of margins at tooth-alloy interfaces during functional loading. The purpose of this study was to determine the relative strength of an experimental consolidated silver material in comparison to other direct filling materials. The method used was designed as a simulation for relative edge-strength clinical properties. Stainless steel dies were formed from disks 5 mm thick, each with a centered hole tapered (1/48) toward the bottom side of the disk. A 41 degrees bevel, 0.5 mm wide as viewed from above, was placed on the top-side of the disk. Dispersalloy (D) or Unison (U) amalgam, Z-100 composite (C), hand-consolidated silver powder (HAg), or pneumatically consolidated silver powder (PAg) was used to fill the die opening. Excess was polished from both sides of the disk with 600-grit abrasive paper. The sample was loaded from the beveled side with a 3 mm-in-diameter flat-ended plunger at a rate of 1.0 mm/minute until failure. Failure load and total energy to failure were recorded and compared. Tukey's multiple comparison test (p < 0.05) ranked the materials (U) > (HAg) > (D) > (PAg) > (C) for fracture strength and (HAg) > (D) > (U) > (PAg) > (C) for fracture energy.

The indirect aesthetic inlay/onlay.

Tooth-colored inlays and onlays for posterior restorations have gained in popularity, replacing time-honored amalgam or cast gold restorations in patients with high aesthetic concerns. This article discusses the available types of indirect inlay/onlay systems and compares them in relation to their marginal integrity, wear, and overall esthetics. A basic preparation outline is discussed.

Comparison of casting ability of castable ceramic and type III gold.

This study compared the property of castability of a castable ceramic to an American Dental Association-certified type II casting alloy. A wax pattern was made with a manifold-type structure from which monofilament lines projected approximately 5 to 6 mm. The diameter of the nylon lines ranged from 132 micron to 1270 micron. Each pattern was invested and cast according to the manufacturer's specifications. Each casting was divested and measured for length of casting of the monofilament on a measuring microscope. The castable ceramic and type II gold cast completely at diameters of 1270 micron, and 724 micron, but only type II gold cast completely at the 152 micron and 132 micron diameters.

Intracoronal pressure during crown cementation.

A model system was developed which recorded the intracoronal pressure during crown cementation at three locations simultaneously. Peak pressures and residual pressures were greatest with zinc phosphate cement. The zinc oxide-eugenol cement generated the smallest amount of peak and residual pressures. The polycarboxylate cement exhibited an intermediate pressure intensity. The uneven intracoronal pressure in the cement suggests a complex flow pattern capable of developing the separation of phases that earlier work reported. However, the small residual pressure indicates that these internal back pressures appear to play a limited role in preventing a complete seating of a crown.

The relationship of bevels to the adaptation of intracoronal inlays.

The elongation of Types II and III gold alloys ranges from 20 to 35 per cent. It has therefore been proposed that a nonbeveled margin could be "pulled" (elongation) to close the margin. However, in clinical practice, it is difficult to pull gold over an unsupported space to close the margin. Furthermore, the thin area of gold that would be pulled toward the margin could easily be sheared or abraded during finishing. Malleting or swaging a beveled margin is a more sucessful technique of adapting cast gold to the cavosurface angles.