Medicaid Dental Benefit Act of 2021 This bill requires state Medicaid programs to cover dental and oral health services for adults. It also increases the Federal Medical Assistance Percentage (i.e., federal matching rate) for such services. The Centers for Medicare & Medicaid Services must develop oral health quality and equity measures and conduct outreach relating to such coverage. Additionally, the Medicaid and Children's Health Insurance Program (CHIP) Payment and Access Commission must report on specified information relating to adult oral health care.