Non-vital 408?

I thought this was an interesting case. The patient is an 8-year-old Thoroughbred mare that was presented for her annual physical examination, vaccination boosters and floating her teeth. The client expressed no complaints. The mare had an acute onset of right ventral mandibular swellings as a 4-year-old. These are the radiographs from 2010:

The treatment at that time was 2 weeks of trimethoprim-sulfa (Uniprim), and the mandibular swellings resolved.

On presentation yesterday, the mare exhibited no mandibular swellling or painful response to mandibular palpation. However oral endoscopic exam revealed defects over all pulp horns of 408

The radiographs reveal abnormal 408 mesial root anatomy, but no apical bone lysis typical of an apical granuloma/abscess:

I think the prognosis for 408 is poor, and anticipate having to extract this tooth within the next 12-24 months.