Our pilot study has also shown that the transport portion is more important than the support portion for bearing occlusal force, so lengthening the transport portion may also benefit the entire distribution of stress. In the case of severe alveolar atrophy the residual alveolar height is limited, and therefore the dimension of the DI device must be minimised to be applicable in such cases. It is therefore important to find an optimal balance between the lengths of the transport and support portions so that the DI can work better.