Hello , Thanks for writing in . may I know his age ? The primary cause for this would be the age related gum disease . Teeth get mobile because of underlying bone loss due to poor oral hygiene and periodontal disease . When a person is suffering from severe gum disease, the dental alveolar bone will recede and the teeth will lose support and become loose. I would suggest to go to the dentist and get a mouth x ray done ( OPG)

Well your question are not very clear, but as per I understand that, there are several number of reasons for teeth are fallen naturally so consulting with an dentist would gave him a proper solution. Thanks

Hi dear....as what can b made out of ur father's brief history, is dat he is suffering from Chronic Generalised adult Periodontitis ... Generally called as Pyrrohea where gums get infected n loose their attachment wid d teeth resulting is loosening of teeth..... In such kind of condition pt. has to undergo regular scaling ( cleaning ) sessions n Gum treatment...