Backface Masking with Sculptris Pro

Backface Masking is incompatible with Sculptris Pro tessellation or tessimation. 

When sculpting with Sculptris Pro enabled, the 'Backface Mask' option for any brush will function normally to protect areas of a mesh behind your sculpting brush draw stroke.  However Sculptris Pro tessellation will be temporarily disabled during this process. 

Once Backface Mask has been turned off for the selected brush, that brush will then provide normal tessellation with Sculptris Pro, allowing you to adjust mesh density in those newly sculpted areas.