Software developed in Hong Kong to help surgeons plan jaw-alignment surgery has been hailed as the best in the world. City University's department of computer science and the University of Hong Kong's Department of Dentistry have collaborated to develop the program. The software received a favourable reception when it was introduced to a conference of dentists in Edinburgh, Scotland, last week. 'There are four other software types of this kind in the world,' said Dr Nabil Samman, associate professor of oral and maxillofacial surgery at the University of Hong Kong. 'One is from Canada, one from Germany and two from the United States, but this one is considered the best.' Dental surgeons praised its user-friendliness and high accuracy during clinical tests conducted in Hong Kong, Shanghai and Britain. At Queen Mary Hospital alone, four or five jaw-alignment operations are performed every week, said Professor Henk Tideman, professor of oral and maxillofacial surgery at the University of Hong Kong. 'The surgery is often not for cosmetic purposes but functional,' he said. 'If the jaws are not aligned, the muscles are not in a balanced position, so a patient may not be able to eat properly.' Surgeons previously used tracing paper placed on top of an X-ray to draw and design the surgical changes. But Professor Tideman said this method meant it was difficult to predict how soft tissue would react to jaw changes. 'We are doing thousands and thousands of operations, and with this program it is less likely a surgeon will make a mistake,' he said.