Okla. Stat. tit. 70 § 17-105.1
In the event the total retirement payments made to a retired member and the retired member's joint annuitant, if any, are less than the member's accumulated contributions with interest as credited at the time of retirement under Section 17-105 of this title, the difference shall be paid to the member's designated beneficiary, or if no designated beneficiary survives, then to the member's estate. This provision shall apply to retired members dying on or after July 1, 1979. After paying unpaid accumulated contributions to any designated beneficiary or the member's estate pursuant to this section, the Teachers' Retirement System of Oklahoma is discharged and released from any and all liability, obligation, and costs. The System is not required to inquire into the truth of any matter specified in this section or into the payment of any estate tax liability.
Okla. Stat. tit. 70, § 17-105.1