A dentist botched a wisdom tooth extraction by erroneously cutting open a patient's jaw, a tribunal ruled yesterday. Dr Lam Kwok-pun, who runs a surgery in Mongkok's Argyle Centre, was found guilty of professional misconduct while operating on university student Chan Man-yan, now aged 23, on September 12, 1997. The Dental Council tribunal ordered that his name be struck off the registry for two months, but suspended the sentence for 12 months. The tribunal failed to find adequate proof on a second charge - that the botched extraction caused numbness and discomfort to the patient's tongue. Ms Chan underwent surgery with the impression a wisdom tooth on the upper right side and an impacted one on the lower right side would be extracted, the tribunal heard. Yesterday Dr Lam said: 'After injecting anaesthetic and numbness had set in, I made two incisions [in the lower right side] and raised a flap. But then I noticed the bone was flat ... I looked at the X-ray and checked again. I realised I'd made a mistake and immediately told the patient.' The tribunal was told Dr Lam relied on X-rays taken about two years earlier in October 1995. He had not used Ms Chan's dental records from the same date. Ms Chan told the tribunal: 'I didn't return to Dr Lam because I believed there had been professional misconduct. I lost confidence in him and went to see another dentist.' Expert witness Professor Cheung Lim-kwong, of Hong Kong University's department of oral and maxillofacial surgery, told the hearing partial numbness on the right side of Ms Chan's tongue was likely to be permanent, and was due to Dr Lam wrongly cutting into the gum. 'The assumption the lower right wisdom tooth was there was due to misinterpretation of X-rays of the lower and right and left jaw . . . such basic knowledge is expected of registered dentists,' he said. 'When a decision is made to do surgery, the dentist should use existing clinical and X-ray evidence.'