Because LaTeX2e supports different encodings, definitions of commands for producing symbols, accents, composite glyphs, etc. must be defined using the commands provided for this purpose and described in LaTeX2e Font Selection. This part of the system is still under development so such tasks should be undertaken with great caution.
Also, \DeclareRobustCommand should be used for encoding-independent
commands of this type.
Note that it is no longer possible to refer to the math font set-up
outside math mode: for example, neither \textfont 1 nor
\scriptfont 2 are guaranteed to be defined in other modes.