In attempts to substantiate the possible participation of reactive oxygen species, and the significance of the xanthine oxidase system in both post-ischaemic reperfusion necrosis of the island flap and distal necrosis of the pedicle flap, and to develop new pharmacological measures for salvaging flap necrosis, a series of experiments were made using an island flap model and a random-pattern flap model in rats. The results were as follows: (1) Epoxysuccinyl derivative (E-64c), allopurinol and L-SOD salvaged post-ischaemic reperfusion necrosis of the island flaps; (2) E-64c and allopurinol did not salvage anticipated necrosis of the distal region of random flaps but L-SOD did; (3) tissue SOD activity did not reflect the fate of the island flap, but did of the distal region of the random flap. These results demonstrated a possible involvement of ROS in both post-ischaemic necrosis of island flaps and distal necrosis of random flaps. However, xanthine oxidase was significant in producing ROS only in the former.

Allopurinol↗

PubMedDate not supplied

Fatigue resistance of titanium-nickel alloy cast clasps.

In this study fatigue resistance of experimentally prepared titanium-nickel (50.8% nickel and 49.2% titanium) cast clasps was evaluated in a simulated clinical situation. The change in force required to remove the titanium-nickel clasps was recorded under a repeated placement-and-removal test on steel model abutment teeth. Commercially-pure titanium, cobalt-chromium alloy, and gold-silver-palladium-copper alloy clasps were also tested for comparison. The tips of the clasps were located in the 0.25- and 0.50-mm undercut areas of the abutments. No significant changes in the retentive force were found in titanium-nickel clasps in the 1,010 repeated cycles, whereas the other three types of clasp revealed a significant decrease in the force required for removal during the test procedures (repeated analysis of variance P < 0.001). The results suggest that the cast titanium-nickel clasp may be suitable in removable prosthodontic constructions because of its significantly less permanent deformation during service. This report also discusses clinical applicability and some current problems with this new application.

Analysis of Variance↗