The electric guitar is not a standard instrument in traditional Cuban dance music. It was, however, in the first line-up of Los Van Van (1969), and in pilón and in some charangas it plays guajeos alongside the piano.
When Juan Formell founded Los Van Van in 1969, according to Wikipedia the band had two electric guitarists: José Luis Martínez and William Sánchez. The award jury that later honoured the band explicitly named the electric guitar as part of the new sound, alongside violins, flute, trombones, drums, bass and keyboards.
According to Wikipedia, bands such as La Charanga Habanera and Bamboleo sometimes play a few melodic notes from songs by Earth, Wind & Fire or Kool & the Gang. The main instrumental innovations in timba, though, were the drum kit and the synthesizer.