Modern medical research is moving away from the use of animals where possible as new testing technology and methods become available, and as more people question the ethics and effectiveness of animal testing.
As we strive for better approaches to research and experimentation, we should not overlook animals’ contributions to the development of medications and medical treatments. Some species have proven particularly effective in advancing our knowledge of and designing treatments for a spectrum of diseases and physical conditions. Sheep, for example, have been instrumental in our understanding of temporomandibular joint disorder (TMJ), which causes chronic pain and is thought to afflict tens of millions of Americans.
The Science of the Lambs: Sheep and TMJ
A recent article in the French medical journal Morphologie discusses sheep’s role in TMJ research. Sheep have long been employed in medical research, but they possess traits that scientists find especially desirable for studying TMJ.
Sheep have certain anatomical structures in the connective region between the jaw and the skull that work with the temporomandibular joints and are similar to their human counterparts:
- Condylar process: The protrusion on the top of each side of the mandible where the temporomandibular ligament attaches; the condylar process also interacts with the articular disk on each side of the jaw to provide smooth movement and distribute bite forces.
- Mandibular fossa: The depression on each side of the skull’s temporal bone, where the mandible connects to the skull; in conjunction with the temporomandibular joints and other connective components, the mandibular fossa helps the jaw open widely.
These anatomical similarities, according to the article, make sheep good guinea pigs for TMJ research. These shared traits have also made sheep popular in developing oral and facial surgery methods, although TMJ can usually be treated without surgery.
Looking Baa-ck: Prior TMJ Research
Sheep provided an early model for studying TMJ-related ankylosis. Ankylosis is joint stiffness; in the case of TMJ, ankylosis may be caused by trauma, rheumatoid arthritis, abnormal bone structure, poor connection between the joint and bone, or infection.
A 1999 study examined the effects of ankylosis in sheep. Scientists removed key elements, including the articular disks, from one side of each subject’s jaw then evaluated range of jaw motion and the onset of ankylosis. Researchers found that ankylosis develops rapidly after damage to or removal of the articular disks and their corresponding surfaces. The study also indicated that TMJ impairs jaw movement and can affect how those who suffer from it eat; two of the five sheep in the study lost substantial body weight as their jaw movement decreased.
In 2012, researchers conducted a detailed anatomical study of the temporomandibular joints in sheep. The authors of that research, whose findings appeared in the Open Journal of Veterinary Medicine, found sheep to be “an excellent experimental model” for TMJ study due to structural likenesses and movement parallels in the joints between sheep and humans.
Last year, scientists at Columbia University’s College of Dental Medicine provided a peek at ongoing research into the potential for growing new cartilage and bone. Early trials for a technique to regenerate cartilage in sheep proved successful, and while the study didn’t focus on TMJ, it paved the way for additional research that could have applications for repairing bone and cartilage deterioration associated with TMJ.
Don’t be Sheepish about Seeking Help for TMJ
Sheep have helped us understand the effects of TMJ, develop new methods for evaluating TMJ, and devise new TMJ treatments. But the only way to find relief from TMJ discomfort is to seek help.
You should consider talking to a neuromuscular dentist about potential TMJ if you experience the following symptoms:
- Chronic jaw pain or tenderness
- Recurring, migraine-like headaches
- Difficulty opening and closing the jaw
- Jaw clicking or popping
- Persistent neck, shoulder or back pain
Denver neuromuscular dentist Dr. Kevin Berry has helped many patients find long-term relief from TMJ pain. Please call the TMJ Therapy & Sleep Center of Colorado at (303) 691-0267 to schedule your appointment.