Prince Philip Dental Hospital in Sai Ying Pun will raise orthodontic treatment charges by 17 to 20 per cent next month. But a spokesman for the city's only dental teaching hospital said the new fees would still not cover all costs. He said a study had revealed that the current fees covered only 55 to 59 per cent of costs. 'The fee revision is in line with the 'user pays' principle. The hospital regularly reviews and streamlines procedures to reduce costs,' he said. Charges for orthodontic appliances will increase by HK$100 to HK$1,200 while general dental bills will not change.