2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/190527We study Pontecorvo neutrino-antineutrino oscillations both in vacuum and in matter within a field theoretic approach, showing that this phenomenon can occur only if neutrinos have a Dirac-Majorana mass term. We find that matter effects suppress these oscillations and cannot explain the solar neutrino problem. On the contrary, a vacuum neutrino-antineutrino oscillations solution to this problem exists. We analyze this solution and available data from laboratory experiments giving stringent limits on $ν_e$ and $ν_μ$ Majorana masses.11 pages, Latex2eHigh Energy Physics - PhenomenologyAstrophysicstext