The Journal of the Dental Association of South Africa = Die Tydskrif van die Tandheelkundige Vereniging van Suid-Afrika最新文献

This in vitro study determined the effect of bonded and non-bonded cast, serrated, tin plated, parallel gold posts on the fracture resistance of surrounding dentine walls. Specimens were divided into two groups. One group's posts were luted with zinc phosphate cement and the other group's posts were tin-plated and adhesively bonded with an adhesive resin cement. Three different dentine wall thicknesses, namely 0.5 mm, 0.75 mm and 1.0 mm were prepared, subdividing the specimens of each main group into three subgroups. Specimens were subjected to a 50 degrees oblique force. The force required to fracture the dentinal walls was registered. There was no statistically significant differences in the fracture resistance of dentine with the two different cements or of the different dentine wall thicknesses.

Surface analysis of similar titanium screw implants from four manufacturers (Brånemark System, 3i, Impla-Med and Restore) showed considerable differences in the composition of the surface oxides. Brånemark System implants had a markedly higher surface content of the natural oxide forming elements: titanium and oxygen. These implants also had a lower content of all contaminants (except boron) and significantly less variation in composition between different samples and points of analyses.

An increase in light intensity is known to produce greater surface hardness of composite resin. The purpose of this study was to determine the depth of cure produced by two light-curing units with different light intensity outputs. Two light-curing units were selected, the one producing 600 mW/cm2 and the other 300 mW/cm2. Five metal plates with thicknesses 1, 2, 3, 4 and 6 mm were selected and 20 holes of 5 mm diameter were drilled through each plate. Each hole was slightly over filled with composite resin (Z100, 3M), covered with a polyester strip, compressed, and light-cured; 10 samples on each plate with the 300 mW/cm2 unit and 10 samples with the 600 mW/cm2 unit. The bases of all samples were subjected to Vickers Hardness testing immediately and one hour after curing. Results were analysed with the Student-t-test. There was a decrease in Vickers Hardness with every increase in depth. Significant differences were found between all the immediate and one hour groups, between the 300 and 600 mW/cm2 light intensities at 2 mm depth and the 2 mm and 3 mm groups. Increments of light-curing composite resin should not exceed 2 mm; optimal hardness only developed after one hour; at a depth of 2 mm an increase in light intensity produced a significant increase in Vickers Hardness; beyond 2 mm depth the increased light intensity did not produce a significant increase in Vickers Hardness.

Various techniques have been described to extrude the roots of fractured teeth to facilitate prosthetic restoration. Many of these have the disadvantage of poor aesthetics, they require skill in fabrication and fitting, and there is often inadequate control over the amount of extrusion. With the technique described, root canal therapy is completed initially and a cast gold post is cemented into the root canal. The post has a channel extending from the labial to the palatal aspect. A temporary acrylic crown is fitted to restore aesthetics, and the channel is extended though the palatal and labial surfaces. An orthodontic wire framework with a horizontal strut at the level of the original incisal edge of the fractured tooth is then bonded to the adjacent abutment teeth. The amount of extrusion required is estimated and a corresponding reduction is made in the length of the acrylic temporary crown. An elastic threaded through the channel and looped over the horizontal strut of the framework provides the extrusive force. A 6 week retention period is required following the extrusion. Periodontal surgery is then carried out if necessary, and a new provisional crown is placed. The final porcelain restoration is fitted after 6 months.