Idealy the canal should be filled to the apical end as there is chances of infection. These days very good endodontic instruments are availabl which can  be used in  the bend canals. But if your dentist is sure thsat tooth is asymptomatic and there is no infection then you can go for this biut if the canal is not fully prepared the chances of root canal faiure are there. For more info on root canal failure you can visit the folowing link.... www.identalhub.com/article_what-if-root-canal-treatment-fails-303.aspx