Dr Donald Macfarlane should have urgently referred the patient – who died months later – to a specialist but the 3cm ulcer was incorrectly diagnosed as the result of an injury.
Glasgow University, which sends dental students to Dr Macfarlane for work placements, is suspending the arrangement for the next year.
And the dentist, who is employed by NHS Ayrshire and Arran, will have to be supervised by a senior colleague at his practice in Kilmarnock, East Ayrshire.
Dr Macfarlane, from Glasgow, was disciplined for misconduct at a hearing of the General Dental Council (GDC) in London last week.
The GDC said the dentist’s “failings represented a real harm to patients”.
The 54-year-old patient was identified only as a psychologist from Germany who smoked up to 15 cigarettes a day and drank moderately, but was otherwise not identified at the hearing.
The GDC said he “failed to ensure [the patient] was provided with adequate smoking cessation advice”.
Dr Macfarlane also, according to the GDC, “failed to ensure that the patient was urgently referred for specialist opinion”.
The dentist admitted all charges against him but denied the patient complained of swelling in April 2010, the third time he saw him.
The cancer was only uncovered after the patient went to see another dentist.
The patient died in February 2011, and his wife complained about Dr Macfarlane to the GDC.
The GDC panel’s chairman, Kevin Moore, said Dr Macfarlane showed remorse for his actions and had apologised to the psychologist’s widow.
Announcing the panel’s decision to impose a “conditions” order on the dentist, Mr Moore said: “You accept that your failings were serious.
“You failed to adhere to the Mouth Cancer – Referral Guidelines for Dentists.
“The treatment you provided to Patient A in 2010 represents a serious departure from the standards of dentistry that were reasonably expected of you.”
He added: “Although this Committee is only concerned with your deficient practise in respect of one patient, your acts and omissions related to three separate occasions spanning several months.
“You ignored clear relevant guidance.
Mr Moore said the committee had determined that this falling short amounted to misconduct.
He continued: “Your clinical performance was of a standard which fell far below that which the patient, the public and the profession generally were reasonably entitled to expect.
“The failings presented a real risk of harm to patients, and were capable of undermining confidence in the profession.”
The conditions say: “He must place himself and remain under the supervision of a workplace supervisor nominated by him, and agreed by the GDC.”
In addition, he will have to notify the GDC about any new position he takes, and if any formal disciplinary action is taken against him.
A spokesman for Glasgow University said: “Our students would go to his practice and spend time with him.
“Because of the GDC ruling we won’t be placing any students with him.”