An 81-year-old dentist has had his licence suspended for three months after letting his unqualified son help him run his clinic when he was ill. The Dental Council yesterday found Ho Siu-ming, described as semi-retired, guilty of wilfully or negligently assisting his son, Ho Kwok-sang, 44, a false-teeth technician, to practise dentistry. The council heard that two police officers posing as patients had visited the Lai Chi Kok clinic on August 20 last year and had caught the son after he used a pair of tongs to check one officer's teeth. Under caution, the son, who worked at the clinic, admitted it was the fourth time he had covered for his father. He said he did not want his father to work so hard in hot weather because he had had a relapse of a skin disease that day. Ho Siu-ming arrived later and told the police that he had not known his son had been substituting for him. The son was fined $10,000 by North Kowloon Court in September last year for practising dentistry while not being registered, while Ho Siu-ming was discharged on the grounds of insufficient evidence. Dental Council chairman Dr Jeffrey Tsang Yick-sang said yesterday that 'covering' was a serious offence under the Dentistry Registration Ordinance. 'But we imposed a light punishment considering Ho's old age and that he has no plan to go on with dentistry,' he said.