Because his teeth are malloccluded they will always cause this problem and need constant trimming top and bottom. The bottom jaw appears to be pushed slightly sideways so the teeth will never meet to rub against each other and keep them from overgrowing sadly. You could ask the vet to teach you to trim the teeth yourself but it is not easy and a bit risky as you can crack the teeth. You could have the teeth removed totally and feed him soft foods only. Only you can decide if you think he is not happy with life and if you can afford the vet costs every few weeks to trim the teeth. It is a hard choice but made with Coco's welfare in mind then it will be the right choice. A big part of a hamster's enjoyment in life comes from nibbling food and chewing and shelling which he cannot do now and we cannot know if the teeth are causing him pain really. I'm sorry he is going through this
