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Definition

A malposition of the teeth that prevents the alignment of the teeth or jaw.

Clinical Signs

The most obvious sign is visible overgrowth or uneven growth of incisors.
A rat with malocclusion may salivate, rub at its mouth with its feet, or exude a foul odor from the mouth. Other signs include inability to chew hard food, weight loss, or sores developing in or near the mouth. Broken upper or lower incisor(s) is a sign that malocclusion may be an issue.

*Note: for additional information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

Rats are monophyodont, having only one set of teeth during their lifetime. Under normal circumstances rats have teeth that consist of 4 opposing incisors, two smaller on top and two longer curved ones on the bottom, as well as, a total of 12 molars towards the back of the mouth, three on each side of the jaw, both upper and lower. The incisors have an open root, unlike its 12 molars, which causes the teeth to grow continuously at approximately 4-5 inches per year. They are covered by a hard yellow enamel on the outside surface of one side , the color of which is due to the presence of an iron-containing pigment. This orange pigment is normal and deepens with age. A rat’s incisors get their chisel like shape through the back and forth movement of the jaw during teeth grinding, which allows the rat to be able to gnaw effectively. The bottom incisors normally appear to have a small gap; this is due to having a hemi-mandibular joint which allows the lower incisors to slightly spread apart to aid in opening seeds and nuts.
In healthy rats the incisors are properly aligned and able to be maintained at a certain length through the process of natural teeth grinding without requiring something hard to chew on.

In a rat with malocclusion, the teeth are not aligned properly and natural grinding cannot take place. The incisor(s) continue to grow and curve, and if not kept trimmed results in trauma to the soft palate, infection, and abscesses, which in turn will eventually lead to the rat starving. Malocclusion may be due to injury (such as loss of a tooth due to root damage or trauma), dental disease, genetics, tumors, or other non infectious reasons.

It is important to check and do a visual exam of your rat’s teeth and mouth on a regular basis to access his oral health. Teeth that are misaligned should be trimmed on an average of every 2 weeks - 2 months (depending on the rate of growth). Infected molars can cause oral abscesses that can go undetected until they actually make their way to the rats epidermis. Abscesses are a concern if a foul odor is present in the rat’s mouth. In such cases the veterinarian may elect to open and debride the abscess and remove the infected tooth.

In cases of oral abscesses, or infections due to malocclusion, it is wise to institute a soft diet during the healing process.

Figures

Photos Showing Both Properly Aligned Teeth and Malocclusion

• Example 1: (From Abscess article) Fig. 5: Oral Abscess
• Fig. 1: Comparing alignment and malocclusion of incisors
• Fig. 2: Gathering supplies to trim teeth
• Fig. 3 Trimming teeth
• Fig. 4 Additional photos of how to trim teeth
• Fig. 5 Teeth damage secondary to trauma

Diagnostics

Based on observation of teeth and mouth.

Obtain history.

Assess for underlying etiology.

Treatment

When trimming teeth, if at all uncomfortable or unsure with procedure the first time, most veterinarians are willing to show you how if you ask.

Any of the following may be used to clip a rat’s teeth such as: toenail clippers, dental bur, or guillotine type dog clippers. However, one may find that the guillotine type clippers may be easier to use on the upper incisors.

Depending upon the growth rate the affected teeth need to be trimmed every two weeks to every 2 months.

Where a misaligned tooth is the result of trauma, the opposing tooth can either be trimmed till the damaged tooth has reached its proper length or removed if the overgrowth is caused by a missing tooth.

In the event of infection, treat aggressively with an antibiotic such a clavamox, and by flushing the infected area several times a day with saline.

For pain management give an analgesic such as infant Tylenol or an anti-inflammatory analgesic agent such as: Metacam (meloxicam) or Banamine (flunixin meglumine).

Refer to the Rat Medication Guide for information pertaining to medications.

Malocclusion caused by cancer has a poor prognosis and surgery is usually not an option. Euthanasia should be considered, and discussed with the veterinarian, where such a condition precludes quality and comfort of life.

Nursing Care

• Assess teeth for proper alignment. In rat’s where malocclusion exists, assess for alignment once a week.
• Use guillotine dog clippers if clipping both upper incisors.
• Use of guillotine dog clippers also helps to prevent brittle teeth from splitting.
• Use care not to twist teeth when clipping in order to prevent any additional damage to teeth.
• Take care to avoid soft tissue of mouth or tongue when trimming teeth. It is advised to have two people involved, one to hold the rat and one to do the trimming.
• If the rat is unwilling to stay still in hands have partner use a towel (like a mummy wrap) to restrain the rat.
• Teeth kept trimmed to ensure nutritional needs are met and that overgrown teeth don’t pierce the soft oral tissue causing infections.
• If pain involved medicate with a pain reliever as necessary to encourage food intake and prevent weight loss.
• Provide soft foods, if oral sores are present and not able to chew recommended diet, to ensure that the rat with malocclusion gets the proper nourishment. Oral area should be checked regularly.
• Weigh rat regularly to monitor for any weight loss. If present, increase caloric content of diet with supplements, e.g., Boost, Ensure, or Nutra-Paste.

Outcome

• Teeth are aligned without splitting.
• Able to chew food without difficulty.
• Maintains weight.
• No mouth sores or abscesses present.
• Infections resulting from malocclusion alleviated, or resolved.

Prevention

• With genetic malocclusion there is no prevention, but rats with this disorder should not be bred.
• Keeping your rat from areas where he will fall will help to prevent injury-related malocclusion. This is especially important when dealing with elderly rats or rats that have disorders that affect balance.
• Checking your rat’s mouth regularly will help you to notice any infection, cysts, or tumors. Look for gum redness, swelling, pus, trouble eating hard food, or a foul odor coming from your rat’s mouth.

Co-authored by Joanne “Bella” Hodges

Posted on June 30, 2003, 10:03, Last updated on April 6, 2010, 19:13 | Digestive