Table of Contents
- 1 Adult Orthodontics
- 1.0.1 Combined Orthodontic/Surgical cases
- 1.0.2 Bands, Brackets, Elastics and Wires: A word about the mechanics of moving teeth.
- 1.0.3 Wires come in two shapes.
- 1.0.4 Bands and brackets
- 1.0.5 A word about Invisalign®
There are lots of reasons that many of us grew up with teeth we consider crooked and ugly. Perhaps our parents could not afford the braces, or perhaps we refused treatment because we were, well, kids. For whatever reason, lots of us wish we could now have what we didn’t get when we were youngsters.
Well, it’s not just for kids any more! The decision that an adult makes to have their teeth straightened is not much different than the decision he or she makes to begin repairing and caring for the teeth that they have neglected over the course of their lives.
It is surprising just how many people are correcting their congenital and developmental deformities in adulthood. With a little care on your part, you can have “perfect teeth” all your life too. (Read my article on Why so many people have such nice teeth.)
And why not? It might cost three to five thousand dollars over a span of about three to five years. It seems like a lot of money, but it is paid over a long contract period and the payments are really much less burdensome than a car payment. But while you will be making car payments all your life, orthodontics is a one shot deal. Once it’s done, with a little care on your part, (and perhaps a lower bonded wire retainer) it stays that way and won’t rust out in the New England weather. How much is it worth to be able to smile during an entire lifetime? What is the value of the quality of your own life?
Adult orthodontics is somewhat different than children’s orthodontics. This is because with adults, unlike children, the bone is not always in a state of flux, and it takes somewhat longer to move the teeth. But they do move, and results like the one above are common. My wife had adult orthodontics when she was 40, and she’s been happy with the results ever since (I won’t say how long, so don’t ask).
No matter how good the orthodontist is, he or she cannot move teeth anywhere the bone will not follow. In instances of extreme deformity, where an adult’s lower jaw is hopelessly inadequate (Class II) to correct with orthodontics alone, or in many cases of lower jaw prognathism (Class III), and frequently in cases of anterior open bite (where only the upper and lower back teeth make contact), it becomes necessary to combine the orthodontist’s skills with that of an oral surgeon to affect a cure. This sort of multidisciplinary approach is becoming more and more common throughout all branches of medicine, and just as I refer to all sorts of specialists in the course of my general practice, an orthodontist makes use of surgeons as well as other specialists on a routine basis
One of the largest advantages of surgery combined with orthodontic treatment is the marked improvement most patients have in their facial appearance after treatment. Andy Gump and Bulldog profiles are reversed overnight. Patients have quick relief from long standing functional disabilities as well. Those who could not chew their food can now eat without difficulty. Patients who could not close their lips around their front teeth now can. Even though I, as a general dentist am not directly involved with this form of treatment, I find these cases to be the most rewarding because the immense improvement in these patients’ lives began with a visit to my office.
Orthodontic movement of teeth involves placing small forces on individual teeth for long periods of time. When the force is applied, an inflammatory reaction develops in the ligaments and adjacent bone surrounding the tooth. The inflammatory reaction is different on opposite sides of the tooth. The bone on the side of the root where the ligament is being compressed begins to resorb (osteoclasts eat away at the bone causing it to disappear and be replaced by soft tissue from the ligament on that side). The bone on the side of the root where the ligament is being stretched begins to build bone (osteoblasts are mobilized and these form new bone on that side). Thus as the tooth slowly moves in the direction in which the pressure is being directed, bone resorbes on one side of the root and reforms on the other side. The movement of the tooth through the bone can be likened to the movement of a boat through water, with the water essentially moving from the bow of the boat to the stern.
The forces on each individual tooth are provided by a series of arch wires. Each arch wire starts out with the general shape of the desired arch, and is modified by the orthodontist with numerous additional bends to accommodate the individual teeth. In its relaxed state each succeeding arch wire will more closely approximate the desired shape of the arch. (An “arch” here refers to the positions of all the teeth in either the upper or lower jaw. When looked at from the “top” of the teeth, the top teeth form one arch and the bottom teeth form another.) When it is first placed on the brackets, however, the wire is NOT in a relaxed state. The wire naturally wants to assume its relaxed state, and consequently, it places forces on the teeth until they move into a position which allows the wire to relax. Once the first wire is no longer placing forces on the teeth, then the orthodontist bends a new wire to begin the process again. The orthodontist does this until the teeth eventually straighten out into the desired arch form.
Wires come in two shapes.
Wires with round cross sections fit the brackets on the teeth loosely. Round wires are used during the first part of the orthodontic treatment. Their job is to TILT the teeth so that the crowns of the teeth come into approximately the correct position in the arch. Round wires work well during this stage of the orthodontic procedure because their job is simply to position the coronal portions of the teeth (the parts of the teeth above the gums). The roots are simply dragged along passively, without much concern for their angle in the bone. This part of the orthodontic procedure moves along fairly quickly since the orthodontist is concerned merely with tilting the teeth into position, and the amount of bone affected by the forces is relatively small. In many cases, the teeth look fairly straight after a relatively short time in braces because the crowns of the teeth have come into a close approximation of their final position.
Square or Rectangular wires
Unfortunately, even if the teeth look fairly straight, the roots are still crooked. In other words, the long axis of the teeth are parallel with the forces they will encounter when the patient eats or clenches his teeth. If orthodontics is stopped at this stage, the teeth will move back to their original positions (relapse) once the braces are removed.
Thus, the second stage of orthodontics involves the use of wires with square or rectangular cross sections. These wires engage the brackets on the teeth firmly, and the angle of the wire’s cross section places a torque on the tooth such that the long axis of the root tilts into an angle which places it parallel with the biting forces. This “finishing” procedure takes a much longer time than the initial round wire positioning phase because the roots must move through a larger amount of bone than they did during the initial stage, and because the movement must be slow in order to avoid shortening of the tooth root.
Bands and brackets
Orthodontic brackets are very small metal, plastic or ceramic brackets that are attached to the buccal (facing the lips or cheeks) surfaces of each tooth. Before the advent of bonding, each bracket was attached to the outside of a band, which is a ring of metal that is placed around the tooth and cemented in place. Since it became possible to bond metal to tooth surfaces, brackets can be attached directly to tooth structure without the use of a band to retain them. Banded brackets today are used mostly for large teeth like molars.
The brackets are always placed on the teeth so that the groove that holds the wire is perpendicular to the long axis of the tooth. As long as the groove is perpendicular to the root, the orthodontist knows that the angle of the wire where it engages the bracket will place pressures on the tooth so that the root will move where he or she wants it. In the image on the left, the bracket contains a groove for a square wire. Note that this type of bracket may be used to contain a round wire during the initial phase of treatment, and then a square wire for torquing the roots later in the treatment.
Glancing at the image of the bracket above, you can see that a relaxed wire may sit inside the wire groove without a problem, but how is an active wire applying all sorts of forces supposed to remain in the groove without slipping out? The answer lies in the external shape of the bracket. Note that both brackets possess vertical lugs creating, in effect grooves at the top and bottom of the bracket. These grooves provide retention for a wire or elastic ligature which is placed over the wire/bracket assembly to keep the wire in its own groove. The image below shows colorful elastic ligatures retaining a round wire. The round wire infers that the treatment is in its first phase, and indeed, it is apparent that the teeth have not yet been tilted into approximate position. In some instances, an orthodontist will choose to use very fine wire as a ligature instead of elastics.
A fairly recent development in orthodontics is the development of brackets which do not require separate elastic or wire ligatures. These brackets have tiny “trap doors” or other mechanical mechanisms for locking in the arch wire. The image above shows a self-ligating bracket. Self-ligating brackets have the advantage of catching less food when eating than brackets that have regular ligatures. Food that catches in the brackets is more easily rinsed off with water during the meal, which makes eating more comfortable.
Note that the arch wire in the image above is not yet engaging the bracket on the canine tooth and the orthodontist is in the process of using an active elastic ligature to extrude the tooth toward the wire. In this case, a ligature elastic is being used for double duty. It not only attaches the bracket to the wire, but it also puts downward pressure on the tooth in order to extrude it it. Power elastics are used in other ways as well. While the arch wire by itself can be used to move teeth up and down or in and out, it is not effective for moving a tooth forward or backwards along its length. Elastics are often used to move teeth along the length of the arch wire. An elastic may be attached to several large teeth and then stretched along the wire to move a smaller tooth backwards or forward. Or a longer elastic may be attached between an upper tooth and a lower arch wire to extrude a tooth.
Remember that orthodontists don’t simply move teeth. They actually manipulate bone. In class II or Class III situations in which the upper and lower jaws of incomparable sizes, the movement, or prevention of movement of the entire jawbone during growth phases may correct this situation. To this end, orthodontists use headgear, attaching large elastics to devices which use the entire skull to apply appropriate pressure to an entire arch of teeth. When this is done, the bone supporting the teeth actually moves along with the teeth.
Headgear comes in all sorts of shapes and sizes depending on their intended use. Children with large lower jaws may wear a chin strap to retard the growth of the lower jaw while children with receding chins may wear a headgear designed to actually accelerate the growth of the lower jaw.
Sometimes called “invisible braces”, Invisalign has become a very popular innovation in straightening teeth. This technique uses a series of thin plastic trays to move the teeth gradually from their initial undesirable position to the final finished straightened position. These trays are designed and manufactured using computerized assisted design techniques. The trays have indents for each tooth. The indent for each tooth that is to be moved is in a slightly different place in each succeeding tray, so that a gradual movement of the teeth is brought about.
This technique can be quite effective in some cases, and it is quite popular with patients because the trays are nearly invisible so most observers will not be able to tell that the patient is in “braces”. If an orthodontist has suggested that you go into an Invisalign treatment plan, then you will probably be quite pleased with the process, and most likely with the results. There are, however a number of hidden “snakes in this garden” and the prospective patient should be aware of these when considering treatment. The following information has been gleaned from conversations with a number of board certified orthodontists who use this technique in their practices.
Invisalign works best when it is used to close unwanted spaces, and for minor crowding situations. It is not useful for the congenital skeletal malocclusions discussed above (especially Class II and Class III). While it may successfully intrude teeth (push them into the gums), It is not generally successful at extruding them. It is useful in all instances in which teeth can be tilted into position, but it cannot move them bodily (that is to say keeping the roots parallel, as can be done with brackets and wires). It is also very difficult to torque teeth (twist them).
If your case requires that the dentist find more room for a substantially crowded dentition, Invisalign is not good at closing spaces created by extracting teeth. (This would require bodily movement.) Space may sometimes be gained by “expanding the arch”, but this technique can lead to overly tilted teeth which may be unstable after treatment, since Invisalign provides no way to “finish” the alignment of the roots.
Can a general dentist do Invisalign?
As long as your orthodontics is diagnosed and treated by a properly trained orthodontist, then if he or she suggests Invisalign, you can be assured of good results. No matter what happens during treatment, these specialists are trained to use other standard orthodontic techniques to supplement the )nvisalign
Unfortunately, not all dentists offering Invisalign have extensive training in diagnosing and treating orthodontic cases. Some of the cases that these dentists will accept for Invisalign treatment may yield disappointing results. Here’s why:
The procedure for doing an Invisalign case involves simply taking impressions and sending models of the teeth to the Invisalign lab where the lab technicians essentially create a treatment plan using these models alone. In general, no diagnostic cephalometric x-rays are submitted to the lab. Any treatment planning associated with the position of the tooth roots and the underlying bony structure of the skull must be done by the dentist himself prior to submission of the models. While some general dentists may have acquired this training during their careers, a majority have not. If the dentist has not properly vetted the case, he WILL receive back a set of trays in spite of the fact that the case is not appropriate for the Invisalign technique. The patient is assured of proper treatment planning only in the office of a board certified orthodontist.