A person who has been partially retired under this system pursuant to Article 1.7 (commencing with Section 19996.30) of Chapter 7 of Part 2.6 or pursuant to Sections 21110 through 21115 may be reinstated from partial retirement by the board as provided in this article, and thereafter may continue to be employed on a full-time basis by the state, in the same manner as a person who has not been so retired.