I do not have 100% cpu with skype video conference, but 80%... but even that is too much for my old laptop which easily arrived to 90ºC.
What I did (and do) is to scale down the cpu frequency using cpufreq tools. Now, changing the cpu governor to "powersave" the cpu goes to its minimum speed and the temperature during skype video conferences do not pass 48ºC. As far as I can see, video performance is not affected.
I wrote this small script:
(you need one cpufreq-set command for each core: -c 0 for the first core and -c 1 for the second) and run it, through a desktop file, with kdesu. You may need to check with cpufreq-info which are the available governors on your system. To return to normal, I have a second script with "ondemand" instead of "powersave".
cpufreq-set -c 0 -g powersave
cpufreq-set -c 1 -g powersave