WordPress 3.9 is now using TinyMCE 4.0, they did a big upgrade. Perhaps your old buttons are not compatible and need some refactoring.
See: http://make.wordpress.org/core/2014/01/18/tinymce-4-0-is-in-core/ as a starting point
문제
It works fine when im using wordpress 3.8. But when i update it to 3.9 version, my custom buttons which i created on tinymce editor are disappeared. Anyone knows how to fix it? Please?
해결책
WordPress 3.9 is now using TinyMCE 4.0, they did a big upgrade. Perhaps your old buttons are not compatible and need some refactoring.
See: http://make.wordpress.org/core/2014/01/18/tinymce-4-0-is-in-core/ as a starting point