Epitaxial growth of diamond on iridium thin films was performed by direct-current plasma chemical vapor deposition with ion irradiation pretreatment of the substrate. Pyramidal epitaxial diamond particles with a number density of ∼108 cm-2 were grown on the iridium film. The epitaxial relation is written as (100) diamond//(100) iridium and [001] diamond//[001] iridium. Tilting of the epitaxial relation, as occasionally observed for diamond on silicon or beta silicon carbide, is scarcely observed. Erosion,as observed for diamond on nickel substrates, is not observed. The effect of the ion irradiation of the substrate is discussed briefly.

We have successfully grown smooth diamond thin films epitaxially on (001) iridium surfaces through a direct-current plasma chemical vapor deposition process with two steps: ion irradiation pretreatment and diamond growth. The epitaxial areas of diamond thin films with a mean thickness of about 1.5 µ m seem to act as optical mirrors. The average roughness (Ra) of the thin film, as measured by atomic force microscopy, is about 1 nm. Confocal Raman spectroscopy was used to investigate the depth profile of the thin film. Raman bands due to nondiamond carbon components were nominal at the diamond/iridium interface or at other depths.

The purpose of this study is to investigate masticatory muscle function in subjects with unilateral cleft lip and palate compared with normal occlusion and the extents of improvement before and after orthodontic treatment. Subjects were twenty pretreatment patients, thirty posttreatment patients and ten controls. Electromyograms were recorded from their masticatory muscles during masticatory movement and tapping movement.Reduction of duration/stroke ratio (D/S) was observed in electromyograms obtained during masticatory movement after orthodontic treatment. The reduction was especially notable in the masseter muscle. In spite of a significant reduction in coefficient of variation (CV) values, a significant difference between the posttreatment group and the control group indicated some persisting irregularity in masticatory movement. Electromyograms taken during tapping movement showed no change in latency in the posttreatment group, but duration of the silent period (SP) was shortened and SP appearance increased. The findings outlined above reveal electromyographically clear improvements in masticatory muscle functions and jaw reflex mechanisms after orthodontic treatment. Nevertheless, parameters for subjects with cleft lip and palate still differed from those for controls with normal occlusion. The influence of plastic surgery in subjects with the defects discussed here causes maxillary retrusion, which in turn results in skeletal malocclusion. Orthodontic treatment should be designed to compensate this dentally and alveolarly. This design and the need to improve masticatory functions would contribute to eliminate the extreme difficulty of the therapeutic process.

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