By Jonathan Thatcher

ANSONG, South Korea, Aug 8, (Reuters) By the time North Korean defectors leave this rural retreat in the South they should have a more winning smile. Finding someone to smile back may be more of a challenge.

''Most of them have bad teeth,'' says Choong-won Lee, showing visitors around a large and well-equipped dental surgery in the modern, comfortable centre he heads that is briefly home to the growing number who flee the impoverished North.

Poor dentistry is just one of a host of problems defectors arrive with at this government-run centre which feeds them up and prepares them for the next huge challenge -- life in South Korea.

''They have gone through a dramatic process of defection and they are exhausted, both physically and mentally'' Lee told Reuters.

''Their health is not usually good. Their minds are not stable because of the stress (of escaping) and they lack nutrition.'' Close to 9,000 defectors, an increasingly high percentage of them women, have passed through Hanawon centre since it was set up over six years ago amid rice paddies and mountains, a two-hour drive south of the South Korean capital.

It was set up around the time the two Koreas -- divided by the Cold War over 50 years ago and still official enemies -- shifted towards warm embrace in the hope of eventual unification.

That embrace has turned frigid after North Korea defied international protests by test-firing a barrage of missiles on July 5, sparking questions in the South over whether their government's softly-softly approach to its irascible northern neighbour is such a good idea.

HANAWON PRAISE The Unification Ministry's Hanawon centre wins high praise for helping North Korean escapees make the daunting leap from their Stalinist homeland to life in what has become Asia's third biggest economy and one of its most vibrant democracies.

''They (at Hanawon) are doing a marvellous job,'' said Douglas Shin, a pastor who works with defectors.

For those who do make it -- normally after a hazardous border crossing into China -- the centre is their first home in the South and where they are taught basic skills to help them adapt.

Most, Lee said, were farmers or labourers who flee simply because there is not enough food at home.

International aid officials are warning that heavy flooding in North Korea in July means the normal food shortages will likely get worse.

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