If you work for a limited company but aren't yourself considered limited, and are paid in dividends, these payments are pensionable.
If a limited company dental practice has mixed income (i.e. part NHS, part private) there is no need to apportion salary / dividends for NHS pension purposes. All salary / dividends paid, up to the contract's ceiling figure, can be allocation as NHS pensionable income.
Further information on the NHS Pension Scheme can be found on the NHS Pensions Website.