Lathe Cut Research Articles

Evolution of Hydrophilic Lens Fitting in Australia*

The availability of materials suitable for lathe cut manufacturing has provided the Australian contact lens practitioner with an excellent opportunity to research and fit hydrophilic lenses. Generally the trend has been to fit smaller and thinner or aspheric lenses and Hydron has been the most widely used material.

The influence of precondensation mercury content on the transverse strength of amalgams.

The purpose of this investigation was to study the influence of changing the precondensation mercury content (initial mercury content) on the early and final transverse strength of different amalgams. The material consisted of five conventional lathe cut alloys, two of which were zinc free, of one dispersion strengthened and one spherical alloy and of three lathe cut preamalgamated alloys. The amalgam was mixed with mercury using three different alloy-mercury ratios. Thus the precondensation mercury content of Mix I was about 50 per cent, of Mix II about 54 and of Mix HI about 59 per cent for all amalgams except the spherical brand. Rectangular amalgam test pieces, measuring 2 × 2 × 12 mm, were condensed by hand using a load of about 17 kg/cm2. The transverse strength test was performed either after one hour or one week using three point loading. The results show that for some of the amalgams an increase of the precondensation mercury content resulted in a slight reduction of the early strength. Furthermo...