(Nov 21) When the left side of his mouth began throbbing three years ago, Mr Lim Tek Pin (above), 76, thought it was just a toothache.

But a visit to his dentist revealed a far more serious condition. There was a lump on the roof of his mouth.

He was referred to National University Hospital (NUH) where tests showed that it was a malignant tumour.

'I thought it was just an ordinary toothache. I didn't even realise there was a lump,' said Mr Lim. 'But I wasn't really afraid.'

He had an operation to remove the tumour in August 2004 which left a hole - about 3cm wide and 2cm deep - in the roof of his mouth.

The surgeon could have patched this by partially detaching a muscle under the temple from the side of the head, and folding it downwards and inwards into the cavity.

But Mr Lim decided against this as he is diabetic and he was worried that his wounds would not heal well or become infected. Now, he wears a prosthesis which has been moulded to the roof of his mouth. A protruding cylinder plugs the hole.

The father of four and grandfather of five said: 'After the operation, my mouth hasn't hurt at all.

'I just can't drink water too fast or it will flow out of my nose. And I can't taste certain foods properly. But I can still sing!' He proved that by breaking into song - the first lines of a Mandarin evergreen.

Mr Lim is among some 150 to 200 patients diagnosed here with oral cancer every year. An estimated 75 to 90 per cent of these cases are attributed to the high consumption of cigarettes and alcohol.

Oral cancer can also be the result of infection by certain viruses such as the human papilloma virus (HPV) which causes cervical cancer, and the Epstein-Barr virus, which has been linked to nose and throat cancers.

Mr Lim used to be a social smoker. He started puffing at the age of 18 and stopped only at 56, when he retired from his job as a manager in a rubber trading company. He drank alcohol too, especially in the course of his work, while entertaining clients. But he gave that up too after retiring.

His surgeon, Dr Victor Fan, a consultant at NUH's department of oral and maxillofacial surgery, said that it was lucky Mr Lim felt some pain. It led him to see a dentist and the cancer was detected early.

Dr Fan, who is both a medical and a dental surgeon, said that most mouth cancer patients do not experience any symptoms until it is too late.

Some danger signs: ulcers that take longer than 10 days to heal, abnormal lumps or bleeding in the mouth, white or red patches in the mouth, and loose and shaky teeth.

Most patients are diagnosed only when the cancer is advanced and have to undergo more disfiguring operations with higher chances of relapse and death.

Sometimes the cancer has spread so far, half the patient's jaw and even an eye might have to be removed, Dr Fan said. In many severe cases, the cancer often recurs in less than six months.

Nine in 10 patients survive beyond five years when the cancer is detected early. But when it is caught at an advanced stage, this figure drops to fewer than two in 10.

Finding out early also meant that Mr Lim did not need to undergo any chemotherapy or radiotherapy - unlike patients who are diagnosed later.

He also does not need medication. He just goes for regular checks to make sure the cancer has not returned.

Mercifully, it has not and his chances look good, Dr Fan said.

For more success stories like MrLim's, Dr Fan, who is also president of the Association of Oral and Maxillofacial Surgeons here, launched Mouth Cancer Awareness Week last year.

Modelled after a similar one in Britain, the campaign aims to create awareness of the condition within the public and among dentists and general practitioners.

It also urges people to go for regular checks even when they feel well, so that any cancer can be picked up early.

Dr Fan said: 'It's very sad when patients turn up too late, because it's very difficult to change the outcome.'