How to Look After a Rabbit That Needs Its Teeth Trimmed
To look after a rabbit that needs its teeth trimmed, it's important that you contact your vet as soon as you notice the problem since rabbits can deteriorate quickly with overgrown teeth. Then, while you're waiting to have your rabbit's teeth trimmed, blend up its food in a food processor and give it to it using a feeding syringe. Also, make sure your rabbit has access to fresh drinking water at all times.
Pay attention for warning signs. Like most other prey animals that are hunted in the wild, rabbits are good at concealing pain and injury (so as to not attract predators).  Sometimes it is obvious to the eye that a rabbit has teeth that are too long, but more often you will need to watch carefully for signs of trouble. A mouth infection or even just 24 hours without eating can be potentially fatal to a rabbit. A rabbit with teeth that are too long will have to change its eating habits. It may stop eating a favorite food, have trouble chewing and swallowing, show changes in feces production, or simply not eat anymore. Overly-long teeth frequently cause mouth pain. Watch closely for your rabbit pawing at its mouth, which is a common indicator of pain. Long teeth cause more cuts and scrapes in the mouth, and are harder to keep clean because of the crowding and irregular shapes. All of these can lead to infections. Keep an eye out for mouth swelling, excessive drooling (especially if bloody), and a new foul mouth odor. Call the vet if you sense a problem. If you suspect that your rabbit has long teeth that are causing problems, do not hesitate to call your veterinarian. Even one day can be too long to wait when dealing with a rabbit infection or lack of eating. The vet can give your rabbit's mouth a thorough examination, likely under anesthesia. Depending on what he or she finds, treatments can range from cleanings to tooth-trimmings (by cutting or filing) to tooth removal in severe cases. Feed your rabbit carefully. First and foremost, follow the veterinarian's advice when your rabbit has trouble feeding due to elongated teeth. Generally speaking, though, the feeding advice will probably be similar both before and after action is taken to repair (or remove) the teeth. When your rabbit has trouble feeding, expect to use a food processor and feeding syringe. Ask your vet's advice, but consider the following recipe: Blend together feeding pellets and water into a smoothie-like consistency. You may want to add some cooked oatmeal to help make it smoother. You can also add some banana or papaya to enhance the flavor. Feed small amounts regularly by placing the feeding syringe carefully into the rabbit's mouth and dispensing the mixture slowly. Make sure the rabbit is still drinking plenty of water. This ability should be unaffected by tooth troubles, but your bunny may be lethargic or disinterested. Make fresh water readily available at all times. Shower your rabbit with extra attention. Rabbits are not known for their ability to handle stress — some have been known to drop dead simply from being startled. Mouth pain and/or an inability to eat properly can certainly be a traumatic experience, so be sure to show your love and concern for your furry friend. Make yourself available for extra nuzzling, cuddling, etc., but also follow the rabbit's lead. Some may be more eager for such contact when stressed, while others may experience additional stress from increased contact. Check up on your rabbit more often than normal, and do so in a calm, reassuring manner. Rabbits seem to be good at sensing anxiety in other animals, so try not to show any. Feed your rabbit fiber. Even with domesticated rabbits who lack the benefits of a “wild” diet, most cases of overgrown teeth can be prevented when the proper foods are offered. Food pellets are convenient and have their benefits, but they should not normally be the majority of your rabbit's diet. Rabbits need heavy fiber to continually wear down their always-growing teeth. In the wild, grasses, leaves, and twigs do the trick. For a pet, make sure that you offer a constant supply of fresh hay, which can be found at pet supply stores and elsewhere. Try to mix up the hay varieties if possible. The differing textures and flavors will produce different chewing motions and tooth wear. As according to your vet's advice, offer twigs for your rabbit to chew on as well. Beware that many types of twigs can be poisonous to rabbits, however. Stick to options like orange, lemon, apple, and willow (fresh or dried); maple, ash, and pine (dried only); and de-thorned rose canes. Make sure they have not been treated with pesticides. You can also freeze the twigs overnight in order to kill off any undesirable insects. Wooden chew blocks can help with overgrown front teeth, but will be less useful if your rabbit's back teeth are too long as well. Check its teeth weekly. No, examining the small mouth of a naturally jumpy animal, while navigating the flaps of skin that conceal the mouth and the sharp teeth inside it, is not the easiest thing to do. But it is of vital importance to your rabbit's health. Check for overgrown teeth, cuts or wounds, and signs of infection once a week at least. Giving a rabbit a thorough mouth examination can be an involved process. Consult your vet or the step-by-step instructions at http://www.rabbit.org/journal/3-9/oral-health.html for assistance. Rely on a professional if you need help. If you are unable or unwilling to put in the effort needed to make thorough examinations of your rabbit's mouth, or if your rabbit simply will not permit it, do not ignore this responsibility. Make sure your rabbit's teeth and mouth are checked regularly. Visiting the vet more often may be your best option, but you might also consider a pet groomer who has experience dealing with rabbits. Visit the vet annually at least. Even if you are doing thorough mouth examinations, it is important that a veterinarian examine your rabbit on a regular schedule. Remember, preventing rabbit tooth troubles before they occur is always the best option. No matter how good a job you do checking your rabbit's teeth, the vet has the tools and experience to do it better. Your bunny may need to be sedated, and x-rays may be required to get a complete picture. If problem teeth are caught in early stages, the vet can use special tools to clip or grind them down, again with the benefit of anesthesia if necessary. Some people may want to try to trim their rabbits' teeth on their own, but it is better to rely on a professional. It is very easy to break off a tooth, which can cause infection, among other problems. 
Pay attention for warning signs. Call the vet if you sense a problem. Feed your rabbit carefully. Shower your rabbit with extra attention. Feed your rabbit fiber. Check its teeth weekly. Rely on a professional if you need help. Visit the vet annually at least. 