About 50 per cent of Hong Kong's five-year-olds suffer from tooth decay while more than 97 per cent of adults have oral health problems. A Health Department survey released yesterday also found most dental problems are left untreated. Department of Health dental surgeon Joseph Chan said about a third of adults aged 35 to 44 neglected treatment, while this rose to 90 per cent of the five-year-olds suffering from decay. Most adults did not perceive the need for regular dental check-ups, the survey of 6,000 people found. 'Most of them had experienced various oral health problems such as bad breath, bleeding gums, sensitivity to hot and cold, and pain that disturbed sleeping,' Dr Chan said. 'Almost half of our adult population had gum disease. The percentages of them seeking dental treatment for these conditions were relatively low - from four to 47 per cent.' The percentage of the adult population with untreated dental problems had risen from 90 per cent in 1984 to 97.5 per cent last year. Among children whose parents rated them as having good oral health, almost 40 per cent had tooth decay, and up to 10 per cent of them had more than three decayed teeth.