Movement Of Teeth Is A Perplexing Feat

Push, pull, slow and gentle so teeth move in bone

Recently, I rediscovered plaster dental impressions of my teeth taken by my orthodontist, Dr. Laurence Wright at the onset of treatment as a young teenager. Since I had an overbite known as, “buck teeth” and one front tooth was rotated, my parents sought the opinion of an orthodontist to see if I should have my teeth straightened. An orthodontist is a dentist with additional training in the science of straightening teeth to improve facial appearance and restore proper tooth alignment for chewing. My orthodontist also pointed out that my upper and lower molar teeth were misaligned which could make me ineligible for military service. This clinched the decision for my parents; their son should start orthodontic treatment, called braces.

Orthodontic treatment is a relatively new specialty but a French dentist, Fauchard, in 1723 moved teeth with a thread passing between teeth banded with gold or silver. The famous Greek physician, Hippocrates (460-377 BC), thought “people with crowding of teeth are molested by headaches and otorrhea (draining ears).”

All four of my daughters while teenagers and my wife as an adult had orthodontic treatment in Jamestown. While I watched my teeth years ago and my family’s teeth straighten more recently, the process did not interest me until finding my impressions.

We think of teeth as rigidly fixed but periodontal ligaments, also called the periodontal membrane, surround the entire tooth root attaching it to bone below the gum line. In effect the tooth is suspended as in a hammock, allowing the tooth to move a tiny microscopic amount when stressed during chewing or during gentle persistent stress by orthodontic braces. Moving a tooth is a biomechanical process in which pressure on one tooth compresses the periodontal membrane on the opposite side of the tooth. This stimulates bone cells, called osteoclasts, to resorb or dissolve bone. On the side of pressure, the tooth moves away from bone pulling on the peridontal membrane. This stimulates bone cells, called osteoblasts, to form new bone in the microscopic space created by the tooth moving away from the original pressure. Repetition of pressure at intervals of four to six weeks leads to a slow movement of the tooth by bone resorption on one side of the tooth and new bone formation on the other side. Once positioned satisfactorily, a retaining device is worn while new bone matures. If a tooth is moved with excessive force, circulation may be interrupted causing death of the tooth.

I find it perplexing that orthodontists can move or drag a tooth horizontally in bone when braces are attached to the top or crown of the tooth above the gum line while 2/3 of the tooth is embedded in the bone socket. This is the “secret” orthodontists learn during several years of specialty training. The analogy of a dinner fork, representing a tooth, plunged into a half gallon of frozen ice cream, representing the bone socket, helps to understand the orthodontic process of moving the entire tooth, not just the tooth visible above the gum. If gentle firm force is applied to the fork handle, the fork tips slightly pivoting at the tips of the fork prongs. Hence, the tooth just tips while the root remains in place so the tooth remains crooked. If the fork in the ice cream is grasped with the entire hand, as one grabs a coffee pot handle, then pulled with a force horizontal to the surface of the ice cream, the fork, including the prongs, should move or be dragged ever so slightly, horizontally through the ice cream. You can imagine the fork would have to be pulled steadily to move prongs a fraction of an inch through frozen ice cream while at the same time avoiding a bend in the fork handle. In a similar fashion the orthodontist must move the tooth root as well as the crown which is done with braces consisting of stiff wires, springs and rubber bands attached to brackets bonded to teeth.

I am thankful for effective orthodontic treatment which resulted from directing natural biomechanical processes to straighten teeth.