In 2008 the Dental Council was made aware of advertising where he described himself as a specialist in craniofacial pain, temporomandibular joint disorder (TMD) and sleep disorders. Zimmerman apologised to the DCNZ and agreed to alter future advertisements to comply.
In 2009 he was found to have neglected to treat a patient appropriately and the dentists' board ordered that he be supervised between November 2009 and June 2010 while a competence review was carried out. The two reviews found he did not meet the required standard of competence.
Conditions on the scope of his practice were made while he undertook a competence programme but in 2014 another three patients laid complaints.
The Dental Council concluded there were fundamental issues and suspended his practising certificate until he had completed the programme and passed the assessment.
ACC later laid a complaint with the Dental Council after finding he had been practising while suspended.
The New Zealand Health Practitioners Disciplinary Tribunal found he had treated and provided advice to five patients between July 24, 2014 and February 2, 2016, despite his suspension.
The tribunal found him guilty of professional misconduct and cancelled his registration as a dental practitioner. The tribunal also censured him and ordered he pay $22,500 in costs.
The tribunal ruled that before Zimmerman could apply for re-registration he needed to complete a course of education or training to satisfy the Dental Council of his competence to practise and his understanding of his professional obligations as a registered health practitioner.