More Questions

I want to ask you how to correct a bilateral crossbite in a 42 year-old patient. I do not think I can use a palatal expander. Is there any way to correct it?

These situations are tough. You can't split the palate without surgery; the sutures are too mature. That leaves us with tipping teeth. You can probably get about 3mm per side of expansion by tipping. If the amount of crossbite is 2mm or less, expanding the archwires during the wire progression may do the trick. If the amount of crossbite is approaching 3mm, a Schwarz plate (which I personally don't like to use) or a quad helix (which I like) will get you to your goal. In any adult crossbite case, always consider leaving the patient in crossbite. Sometimes the best answer is the most simple.


One other question: I have some patients' moms discussing ortho in their young kids, who still have many deciduous teeth. Is it usually best to wait until these have exfoliated? I understand that growth curves favor early intervention, but waiting for permanent bis to erupt may prolong treatment. Do orthodontists routinely wait for all the deciduous molars to exfoliate prior to starting ortho? Are there certain malocclusions that most practitioners treat early?

You are touching on a very controversial topic. Many practitioners swear BY early treatment-they say it is always better to treat early- while many practitioners swear AT early treatment- they say it is worthless. The answer is probably somewhere in between. The more severe the malocclusion, the more early intervention seems to help. FYI, most of the orthodontic literature demonstrates there is not a whole lot of value in early (two phase) treatment as compared to more traditional single phase treatment. The bottom line is that with experience you will develop a treatment philosophy that probably will include some early treatment.

When are vertical (triangular) elastics used in the finishing phase? Would that be in weak muscled patients? Do you routinely use elastics for finishing, or mainly rely on settling forces and arch wire bends?

I use finishing elastics in about 20% of my cases. They tend to be helpful on weaker muscled patients, where the muscles are unable to provide adequate settling forces. I try bends before adding elastics in most cases. If the bends provide good interdigitation, I'm done; if not I add elastics.

I am finishing up a case in which all teeth interdigitate well with the molars in solid Class I occlusion. I had the patient use Class II elastics for 3 months. However, some overjet remains in the anterior. Since all teeth are in contact, I do not think it is a good idea to do IPR on the anterior teeth and retract them with chain elastics. I might improve the overjet, but teeth might not interdigitate well as a result. What is your call on this?


I think you are faced with a tooth size discrepancy. Upward of 80% (that's right 80%) of patients have some sort of discrepancy. This case probably has excess tooth structure in the maxillary. This often presents as good posterior interdigitation combined with overjet. In these cases I often do a little ARS in the upper. I usually strip 1mm distal to each cuspid. Then I close the space with 6-6 chain. I find that this retracts the anterior segment a bit without changing the posterior occlusion. Because the space closure is minor, it can be done on the finishing wires (.018st steel), although it is always better to close spaces on .019x.025 stainless steel wires.



I have a case in which I could not close the space of about 1 mm between the bicuspids with elastic chain. I am thinking of using closing coil; however I have never used it. I learned that there are niti and stainless steel closing coils. These coils can be purchased in spools, or in different lengths with hooks at the ends (to engage the hooks on brackets). I prefer spools of stainless steel coil. I have not ordered any and want your recommendation. Please recommend the type and the steps of how to choose the length of the coil for a particular span from one bracket's hook to another. If you happen to recommend the one that comes in a spool, please advise me how to form a "hook" at both ends of the coil, so I am able to engage it on the bracket hooks.


When I use closing coil (which is rarely), I use stainless steel coil off of a spool. I like to stretch the coil about 1.5 times its resting length measured from the distance between the two attachment points. I use a bird beak and grab the last link of the coil, turn it up 90 degrees, and shape it to make a loop at right angles to the rest of the coil. (If you experiment with this, you will find this to be very easy to do.)I then use a Koby hook on the bracket of the teeth to be engaged if it doesn't already have a hook on the bracket. Stretch the coil, and slide the loops over the hooks. Remember, any method of force application should work. I would be more inclined to look at why the space is not closing, not changing the method of space closure. Some possible culprits:
1) overbite is too deep
2)bracket position is off
3) sinus on the upper is low-cortical bone of sinus wall is interfering with root movement
4)friction in space closing set up
Usually, for the last mm or so, friction is the culprit. You could have a bracket whose tie wing is bent, a slot that is a bit constricted, or numerous other issues. I usually will try (if I have eliminated the other above possibilities)going to .020 stainless steel and closing the remaining space on round wire with chain. I know this violates one of my rules, and we are risking the expression of side-effects, but for a mm or so in a stubborn case, the risk is worth it. Remember, you have to know the rules before you can break them.

I have always bracketed all upper teeth at same height from the incisal with the cuspids and centrals .5 mm longer than the laterals. I know you position brackets by finding the center of the teeth. I am just not too comfortable at doing it your way. I read old lectures, not yours, and came across one that said to bracket all teeth at same height from the incisal with the laterals .5 mm shorter. What are your thoughts on these different ways of bracket positioning?

You are touching on the art vs. the science of orthodontics. Any consistent way to get brackets positioned properly is vital to getting a good result. Changing how brackets are positioned will give you different smile lines and esthetics. Understanding this means you are starting to understand the art of orthodontics. Positioning the anterior brackets a little incisally will result in some intrusion and, therefore, a little less tooth display than positioning the anterior brackets more gingivally. So each of these techniques may be appropriate in different situations. Incisal positioning may look a little nicer in a patient who already has excessive gingival display. Gingival positioning may be appropriate for a patient who doesn't show a lot of teeth while talking or smiling.
My point is each case is different, and if you truly want to provide the best results for your patients, you must, at times, deviate from the ideal. Understanding how different bracketing techniques result in different esthetic results will allow you to change bracket positions with confidence.


I find that I'm spending a lot of time coordinating my 19x25 stainless steel. When I try to conform the 19x25 steel to my initial wire I use my fingers to match the wire. Do you use pliers to do this? On one case I elected to leave the 19x25 niti because my steel was not accurate. If I do leave the 19x25 niti instead of the steel how long should I wait? If the 19x25 niti fits passively after 2 to 4 months is that a sign that it has served its purpose?


I coordinate .019x.025 st steel with a hollow chop pliers(in the Ortho Organizers cat. it is Endura #201-401). It is tough coordinating these, but with practice, it can be done. In some cases, I don't use .019x.025 stainless steel when there are no mechanics to do. If there is no space closure, midline shift, or Class II or Class III correction, I often skip the .019x.025 st steel and stay in .019x.025 niti. This has to stay in at least 3 months to provide torque expression. When it is passive, it has done its job. However, don't do complex mechanics on niti, because the side-effects of these mechanics are more easily expressed on the low-load deflection archwires.


Thank you for the reply, regarding the wire progression. Mechanics should not be done with any 19x25 niti wire at all? What about space closure and elastics use?

The low load deflection arch wire (niti) is not strong enough to overcome the side-effects of commonly used orthodontic mechanics. For example, if you use Class II elastics, the patient usually hooks the elastic to the hook on the lower 1st molar band. The elastic provides a vertical force on the molar. The low-load deflection niti wire will be overpowered by the elastic, resulting in extrusion of the molar. The result is loss of vertical control. If the same mechanics are done with .019x.025 stainless steel wire, the strong arch wire will prevent extrusion of the molar. The result here is better vertical control.

I have two concerns. First,I have a case which I expanded both upper and lower arches due to severe lingually inclined teeth. After the teeth are uprighted, do I need new upper and lower models to coordinate the wires? How do I coordinate arch wires, lower 3 mm wider than what is indicated on the new model and upper 3 mm wider than lower? Or do I make the lower arch width 6-7 mm wider than what is indicated on the new model,with the upper 3 mm wider than lower?
Second, you said Class II elastics will reduce about 4 mm of overjet. I'm using Class II elastics on a case that needs 8mm of Class II correction. After correcting 4 mm of overjet (I still need 4 mm more of overjet correction),can I hold the bite where it is after the first correction of 4 mm overjet for six months, to give the condyle and the fossa time for bone remodeling and muscle adaptation?. Then, after the rest period,can I use a second round of Class II elastics for the remaining 4 mm of overjet correction? I'm referring only to using Class II elastics, with no other means of Class II correction, such as extraction or ARS.

When coordinating arch wires,I look at how much expansion is needed (for this look at pre-treatment models) and coordinate all my stainless steel arch wires to this position. In the example you gave, I would not take another model just for the purpose of arch wire coordination. If my arch widths are where I want them , I simply continue to coordinate based on the pre-treatment model. Because the arch widths are correct, you are using the correct arch width coordination. There is no reason to complicate matters by changing how you are coordinating the arch wires.

I rarely use Class II elastics for more than 5mm of Class II correction, even in very strong muscled patients. The issue is not a TMJ issue-the condyle and fossa can adapt to the new condylar position. In fact, when using repositioning appliances, we expect condyle and fossa adaptation for even larger horizontal corrections. The issue is the side effects that Class II elastics cause to the occlusion. For example, if you try to correct 8mm of overjet with Class II elastics, the vertical forces placed on the lower molars will extrude them. This will result in occlusal plane tipping and downward and backward rotation of the mandible, tipping of the upper occlusal plane inferiorly in the anterior, which results in increased gingival display. A rest phase does not change the total time you need to use Class II elastics; the net side effects will still be there.
The bottom line is this: Class II elastics are very effective in correcting small and moderate amounts of Class II, especially in strong muscled patients. But, the side effects are real, and can ruin an otherwise nice result. Don't fall into the trap of using Class II elastics in severe Class II situations in an effort to avoid more difficult treatment options that may be better for the patient. Be aware of potential side effects, and understand which patients will not respond well to the elastics. Also understand what specific side effects will be detrimental to the patient that is being treated with Class II elastics, and watch carefully for the first signs of the particular side effects.

Frequently asked questions, part 2

I'm using lacebacks on an extraction case. One question: when the lacebacks are tied in, with the wire on top, is there enough room around the brackets for elastic ties or would you have to use the ligature ties to tie everything in place?

I use elastic ties when engaging the wire. There is plenty of room on the bracket tie wings for both the laceback and the elastic tie.

What kind of burs do you use for IPR?

I use Essix burs. Find them here- http://www.essix.com/orstore/default.aspx . The specific burs I like are the 55000 for anterior reduction and the 699LC and 848MD for posterior teeth.

An issue that I am struggling with is re-bracketing. In the first scenario, a patient breaks a bracket, say in the 020 or rect wire stage. Some tooth movement seems to have occurred since the break. How far do we have to go back in wire progression to catch up? I have found that I'm often using 016 Niti to get the new bracket and tooth in line. But what then? Second, after repositioning for second order movement in mid-course, I'm going to 016 Niti, but then can't seem to get right to the rect niti next month because it won't fit that tooth position. Is there a certain way to reposition brackets that will speed the process? What if a patient is breaking brackets every other appointment? Biting fingernails?

The first rule in re-bracketing or repositioning is to be efficient. In your 1st case, even if you were in .020, I would re bracket that tooth at the same time I repositioned. If I had time, I'd do it that day. If not, leave the tooth unbracketed and schedule a longer appt. for repositioning in a month. One of the beauties of ortho is you can delay or speed up things depending on your schedule at that particular time. This is not the case with most other dental procedures.
To answer your 2nd question, if you can't go directly to 019x025 niti from 016 niti, use an 016 st steel wire for a month. Again, not all patient's teeth move exactly the same way, so sometimes we have to adjust on the fly. Position the brackets correctly (there is no magic here) and use the wires you need.

Breaking brackets is a whole different issue. Poor coop takes all the fun out of ortho. Look in my "policies" handout which I gave out in the last course. We charge the pt $20 per bracket after they have broken off 10 (most orthodontists start charging after 5). You will be surprised how quickly the situation improves after the parents get a few extra bills.

1) The bracket on LR4 has come off between just about every adjustment; however no other bracket has come off! FYI, I do have a few ortho cases going and haven't had problems with brackets coming off...this is starting to frustrate me! Any troubleshooting advice? (I have even placed a NEW bracket, just to be sure)

2) Do you have any info on how to place koby hooks?

3) According to USDI guidelines, the consolidate stage is to close posterior spacing, so if it's a non-extraction case, do you generally skip this stage? And are lacebacks your preferred method of closing space? I have heard of k-modules, chain elastics, etc. Which ones work best in which situations?

Brackets consistently coming off is a frustrating problem. It's usually related to occlusion. When you re bracket, make sure it is not interfering. You can relieve interferences by adjusting the bracket (usually a tie-wing is the culprit) and by also doing a minor adjustment on the opposing tooth.
I usually place Koby hooks under the archwire. Then you don't have to remove them on every wire change. Just tie it in like you would a steel tie. Be sure to pull tightly on the pigtail as you twist. After tightening, deflect the hook to where you want it to go by using a ligature director. Then tie the wire in as usual over the hook. The Koby hook gains stability when the wire is tied in.
Lacebacks are used early in extraction cases to control anchorage (that is initial retraction of cuspids into the extraction site without any forward molar movement) so, technically, they are not a method of space closure. Any elastic force can be used to close space. Power chains, k-modules, elastics, open coil springs, etc. all work. Use what works best in your hands. Personally, I use elastics (1/4" or 3/16" medium ) until the space is about 2 mm. Then I use power chain. I think the archwire used is more important than the type of force. To maintain good torque control, I like to use heavy rectangular wire during space closure.
Finally, if there is no space to close, consolidation is essentially complete, so, yes, you technically skip this stage in those situations.

What are the things to look for in the prefinishing check list?


Prefinishing Checklist

Name _________________________ Date ___________

Initial bracketing date ____________

1. Goals of treatment
a. _________________________ accomplished yes ___ no ___
b. _________________________ accomplished yes ___ no ___
c. _________________________ accomplished yes ___ no ___
d. _________________________ accomplished yes ___ no ___

Explanation of no answers
__________________________________
__________________________________
__________________________________

2. Static Occlusion – 6 keys
a. molar relationship......acceptable yes ___ no ___
b. tip.....................acceptable yes ___ no ___
c. torque..................acceptable yes ___ no ___
d. rotations...............acceptable yes ___ no ___
e. spaces..................acceptable yes ___ no ___
f. curve of Spee...........acceptable yes ___ no ___

Explanation of no answers
__________________________________
__________________________________
__________________________________

3. Functional occlusion
a. Left lateral working ______ balancing interferences ___________
b. Right lateral working _____ balancing interferences ___________
c. Protrusive ______________ interferences ___________________

Is functional occlusion acceptable yes ___ no ___ CR = CO? yes ___ no ___
Equilibration required yes ___ no ___
If unacceptable, why? _____________________________________________
________________________________________________________________

Ready for de-banding? Yes ___ no ___
If no, how long? ______________
Fee paid yes ___ no ___
If not, how much is owed? ____________



I have some anterior open bite cases I'm treating. In some of these cases the bite closes by just going through the wire progression while others require 019x025 nitinol rocking chair curve (RCS wire) coupled with heavy elastics from upper to lower canines. The problem with this is patient cooperation; patients will not apply the heavy anterior elastics because they hurt and instead of closing anterior bite we now have more bite opening. So, I'm wondering instead of using the RCS wire maybe I can use just a regular 19x25 nitinol with lighter anterior elastics (1 or 2 elastics instead of 3) . So, if the patient doesn’t wear the elastics the open bite won’t worsen. Would this work? What do you think?

Welcome to the wonderful world of ortho. One of the advantages of GP ortho is you get to pick the cases you want (and don't want) to treat. With diagnostic experience comes the ability to pick out these tougher cases before you begin treatment. You can then either charge more or refer.
If you have an open bite in the bicuspid area as well as in the anterior, a flat wire will not easily solve the entire open bite problem. In these cases, there is no way around the difficult mechanics of RCS plus heavy elastics. However, if the bite is closed (or nearly closed) in the bicuspid area, then lighter anterior elastics on a wire without curve should do the job.

Remember, a little (1 to 1.5mm) lateral open bite may respond to differential bracket position. Get those bis bracketed gingivally, and eruption (and hence lateral open bite closure) may occur. That being said, RCS plus heavy elastics is still one of the most reliable methods of open bite closure.

Frequently asked questions

In space closure, if after a couple of months of space closure, we still have a couple of mm of space in the upper anteriors and no spacing in the lower arch, the occlusion is a solid ClassI with little or no overjet, is it correct to assume that we have a tooth size discrepancy? There seems to be 2 ways to deal with this remaining space, either bond composite to the upper teeth to close it or perform ARS on the lowers? What would you do in this situation?

Studies show that in 60% of cases, there is a tooth size discrepancy where there is more tooth mass on the lower arch than on the upper. This is usually due to small upper laterals or large lower laterals. We call this the 60% problem. The solution to this is to do what you suggest. In 20% of all cases, there is excess tooth mass on the upper. This is called the 20% problem; it can also be corrected by IPR, but in this situation, it is the upper arch that is reduced. In my practice, I often do the ARS on the premolars because stripping in that area does not affect the esthetics as much.
The interesting point about this discussion is that only 20% of all cases have no tooth size- arch length discrepancy, so the problem you describe is present in a lot of cases. However, in many cases with a discrepancy the problem is too small to be clinically relevant, so not all of the cases with a discrepancy need interproximal tooth reduction or bonding.


If we are to call the diagnostic arch length the existing mandibular form, taken from the molar buccal cusp tips and anterior incisal edges, and not expand, how do we substantial crowding?
Another way to put my question-when we unwind all of the crowding, don't we need a longer arch length, or distal drive the molars? Creating a Roman arch form and advancing anteriors will not strictly maintain this existing arch length, right?

If you keep your arch length the same, the only way you can relieve crowding is to remove tooth structure. Tweed wrestled with this problem 70 years ago and ended up extracting 4 bis in 90% of his cases.
We base our arch width on a line 3mm wider than the cusp tips/incisal edges to account for bracket thickness. We can change arch form (expand or labially advance teeth) to relieve crowding. How much of this can you do? Different practitioners will alter arch form different amounts. The more you change arch form, the less stable the final result will be, but the more you alter arch form, the less extractions you have to do.
From a philosophical standpoint, I am not a big fan of distalization, especially on the lower. I don't like pre-determined arch forms, and I don't like to do a lot of expansion. This is why I extract teeth. Over the last 15 years, I extracted some combination of bicuspids in a little over 21% of my cases. This is a little bit lower than the 26% national average as reported by the AAO, but as a GP doing ortho, I do refer some of the more difficult cases that present in my office. These difficult cases are usually extraction cases, so factoring in these cases to my overall percentage would bring my extraction percentage closer to the national average.


I have evaluated cases involving Class II elastics and I remember what you said about the use of Class II elastics,that is, Class II elastics really work but if you use them you may be "selling your soul because of some of the side effects that may occur”. I've looked at a few of my cases and I think you meant Class II elastics may distort everything we've worked to achieve up to this point in treatment. I see mostly lateral open bites, especially molars out of occlusion. So what should or could we do to remedy the ill effects of Class II elastics? Do we use single elastics on each side and use less aggressive means (I've been using 2 elastics on each side 3/16 med full time wear)? Do we accept this problem as side effects of Class II elastics and deal with it after the Class II has been corrected? I'm thinking using Class II finishing elastics with vertical elastics on the 6's or maybe even bracketing the 7's. What are your thoughts on this matter?


There are certainly many side effects associated with Class II elastics. To minimize the side effects, I try to use them only in .019x.025 st steel with the bite opened to the desired level. Then,the elastics act as minor repositioning devices. This, hopefully, will eliminate the lateral open bite problem. If lateral open bite still occurs, go to a lighter wire after the Class II is corrected and the occlusion should settle.
I like to use ¼” medium elastics, with full time wear. This provides a constant repositioning force and maximizes the speed of correction. If correction doesn’t occur with this force, I increase the force by using 2 elastics per side, but this may lead to the side effects you described, especially in weak muscled patients. Vertical finishing elastics are a good way to close lateral open bites; bracketing the 7’s in cases that can tolerate the bite opening will also help.
The bottom line is Class II elastics are a good way to correct Class II, IF you can stand the side effects. Many ways exist to handle the side effects, but these ways may be a bit mechanically complex.

I noticed that a case of mine has a tooth size discrepancy, with wide mand lateral incisors, and wide mand second bi's. Much more crowing exists on the lower than the upper, and the molars are Class I, but with only 2 mm of overjet in the anteriors. Initial leveling and aligning will probably advance the lower anteriors. Do we wait to do IPR on these type of cases after crowding and rotations are relieved, or can do IPR before initial aligning? She is not a weak muscled patient, but I still would prefer not creating edge to edge in anteriors and opening the bite. But I guess that it comes with the territory that the teeth may look worse before they look better.

Good job in picking out the tooth size discrepancy before treatment starts. I like to align before I do IPR, even if it means the occlusion will be edge to edge for awhile. The reason I do it this way is because when the teeth are aligned, it is easier to strip the contact points and shape the teeth correctly. When crowding exists it is tough to get at the contact points accurately. In addition you never quite know how the leveling and aligning will play out, so I always like to get things lined up before I do something irreversible. So, get into at least .016st steel before doing any reduction.

Temporary Anchoring Devices or mini implants are something we've never talked about. They are gaining in popularity among orthodontists. Are you currently using them? Do you think this will decrease treatment time? What kind of cases are they indicated, deep bites cases, open bite cases ?
What are your feelings towards TAD?

TAD's are all the rage these days. They are easy to insert and remove and provide reliable anchorage. They are used for space closure, distalization, intrusion, as well as attachment points for interarch elastics so the mechanical advantage of the elastics is greater. They are often used for bite opening and bite closing. I see their use greatly increasing over the next few years.

Important Orthodontic Studies

For anyone practicing orthodontics, keeping up with the literature is essential. There are many ways to do this, but one of the easiest methods is to subscribe to Practical Reviews in Orthodontics. ( http://www.cmeonly.com/programdetails.cfm/2/44/2) Each month you receive an audio CD and a written synopsis of the most germane orthodontic articles from all the major orthodontic journals. The reviewers do a great job of summarizing all that is new and important in the orthodontic literature. Try this service; you will not be disappointed.

The orthodontic practitioner should not only keep abreast of current orthodontic literature, but also be aware of the studies that have shaped how orthodontics is practiced today. I believe the study performed by Professor Arne Bjork while he was the chairman of the Orthodontic Department of the Royal College of Dentistry in Copenhagen is the single most valuable study ever done in the field of orthodontics.

Professor Bjork practiced orthodontics for about 20 years before accepting the previously mentioned teaching position in 1950. For the next 15 years, he worked on this study. Bjork placed titanium implants in the maxillas and mandibles of 240 children. He then took yearly records, performing no other treatment on these patients. This research is valuable because it can never be duplicated. Today’s medical ethics prevent researchers from placing implants for observation only. In addition it is now unethical to watch and not treat severe malocclusions. Because the scope of medical ethics was so different in the 1950’s than it is today, Bjork was able to provide the orthodontic community with a valuable body of data.

So, what’s the big deal? Why is this information so precious? Well, by superimposing cephalometric x-rays on the implants, Bjork was accurately able to determine how faces changed with growth. When superimposing cephs without implants, it is nearly impossible to discern the difference between growth and bone remodeling.

Interpretation of Bjork’s data lead to some interesting conclusions. The driving force responsible for facial growth seems to be the condyles. If cellular proliferation is near the anterior surface of the head of the condyle, the mandible rotates in a forward direction (counter- clockwise, if one views the chin in profile). See figure below.

If cellular proliferation is near the posterior surface of the head of the condyle, the mandible rotates in a backward (clockwise) direction. See figure below.









As the mandible moves due to the cellular proliferation, the sling of muscles that encapsulate the mandible are responsible for pressures and tension directed onto the bone. These forces result in apposition and resorption of mandibular bone. Therefore, mandibular morphology is different for forward and backward mandibular rotation.

Because of the way the muscles act (as well as some other factors), forward rotators are referred to as strong muscled patients, and backward rotators are called weak muscled patients. Almost all orthodontic mechanics result in extrusive forces on the teeth. Strong muscled patients resist this extrusive tendency, while weak muscled patients tend to not resist this tendency. This leads us to a very important concept: the same brackets, bands and wires will produce different treatment results in different patients. Muscle strength (which can vary by a factor of 6 between strong and weak muscled patients) is the main reason for these variable treatment responses.

So, how do we use this knowledge to improve treatment? Weak muscled patients tend to be open bite patients; the extrusive component of orthodontic mechanics is often expressed. Conversely, it is often very difficult to open the bite in strong muscled patients (who tend to be deep bite patients). By looking at the shape (morphology) of the mandible, the practitioner can determine if bite opening or closing will be a problem. A specific treatment plan for the individual patient can then be devised.

Some other facts stemming from Bjork’s work are very important. First, the distribution of growth cells on the head of the condyle follows a bell shaped curve. That is, not all patients are entirely strong or weak muscled. About 85% of patients are predominately strong muscled (good thing, because weak muscled, open bite patients are difficult to treat). Many patients have some strong and some weak muscled characteristics. The most difficult cases are the very strong, and especially very weak muscled patients. These cases are often easy to pick out because the mandibular morphology is very diagnostic. The difficult part is to monitor the borderline cases to see if vertical control becomes problematic. Graber states in his textbook that controlling vertical dimension in borderline patients is one of the most important aspects of good treatment.

Second, forward or backward rotation is a highly genetic phenomenon. Condylar growth direction depends on the location of the growth cells; this is an inherited trait. However, growth patterns can be affected by the environment. For example, airway blockage, habits, allergies, etc. can change the normal position of the mandible, allowing different parts of the growth center to be more fully expressed. So, according to Bjork, environment influences growth while genetics controls it.


Bjork used knowledge of apposition and resorption of bone based on muscular pressures and tensions to determine muscle strength based on mandibular morphology. I like to use five characteristics to point out the morphological differences between strong and weak muscled patients. Not all these characteristics are visible on all patients, and previous growth direction does not insure that future growth will continue in the same direction. But despite these limitations, mandibular morphology is a useful predictor of both future growth and response to treatment mechanics.

Let’s explore the specific morphological characteristics I use. First,
the gonial angle will be more acute in strong muscled patients and more obtuse in weak muscled patients. Second, the shape of the lower border of the mandible is a good predictor. In weak muscled patients, apposition below the symphysis and resorption anterior to the gonial angle produces a concavity throughout the lower border. In strong muscled patients, anterior rounding is absent. In addition, notching occurs anterior to the gonial angle. This results in an "S" shaped curve on the lower border. The third predictor I like to use is the density of bone at the symphysis. A thick symphysis indicates strong muscles, while a thin symphysis means the muscles are weak. Fourth, the inclination of the symphysis is a reliable predictor of muscle strength. In strong muscled patients, the inclination is relatively acute, while the norm for weak muscled patients is a more obtuse inclination. The final indicator I use is the inclination of the condyle.In strong muscled patients, the condyle will incline anteriorly, while in weak muscled patients, the condyle will have a posterior inclination. This trait is not always visible on the ceph because of superimposition of structures over the condyle on ceph x-rays.

There are many other predictors of mandibular growth rotation.Many clinicians rely solely on mandibular plane angle to predict muscle strength (and, hence, treatment response). Although weak muscled patients usually have higher mandibular plane angles than do strong muscled patients, this measurement can be deceiving. If the clinician uses more than one measurement to arrive at a diagnosis, the diagnosis will probably be more accurate. Using all the available data will help insure that the patient will receive the best diagnosis possible.


In addition to maxillary and mandibular growth rotation (the maxilla follows the same basic rotational pattern as the mandible), Bjork also described the intramatrix rotation. He defined the intramatrix as the maxillary and mandibular teeth and alveolar processes. Bjork described three types of intramatrix rotation, two which can occur in strong muscled patients, and one which occurs in weak muscled patients. To understand intramatrix rotation, one must understand Bjork's definition of the fulcrum. The fulcrum is simply the most anterior contact point of teeth in occlusion.
Type I intramatrix rotation occurs in strong muscled patients when the fulcrum exists at the incisal edges of the maxillary and mandibular anterior teeth. This combination of mandibular and intramatrix rotation leads to normal downward and forward growth of the cranio-facial complex. This results in the best possible growth for the patient.
Type II intramatrix rotation occurs when mandibular rotation is forward without an incisal edge fulcrum. This lack of incisal edge fulcrum often results from tongue or lip habits, or from early exfoliation of primary teeth.The fulcrum now exists in the middle of the arch. This pattern leads to over eruption of maxillary and mandibular anterior teeth, a deep bite, and collapse (lingual movement) of the maxillary anterior segment-a classic Class II, Division II malocclusion.
Type III intramatrix rotation occurs in weak muscled patients where the fulcrum is on the posterior teeth. If sufficient eruption occurs in the anterior segments, the result is a long face with good occlusion. If something (tongue, lip, fingers) interferes with anterior eruption, an open bite results.

Understanding cranio-facial growth rotation leads to many interesting diagnostic conclusions. In Type I and Type II intramatrix rotation, teeth move forward and laterally on the alveolar processes. The opposite occurs in Type III intramatrix rotation. Therefore, expansion and arch length gaining treatment may be more successful in Type I and II intramatrix rotation than in Type III intramatrix rotation. Crowding that can be corrected by expansion in a strong muscled patient may require extractions in a weak muscled patient. In fact, every decision you make regarding a patient's treatment will be influenced by the patent's muscle strength. Extraction vs. non-extraction, bracket position, composition of arch wires used, and type of retainer used are all greatly influenced by a patent's muscle strength. It is clear that an understanding of Bjork's research will change the way you look at orthodontic diagnosis.

Comments on Space Closure

I often receive questions on space closure mechanics; I will take this opportunity to address issues regarding space closure.
First, and most important, the biology of tooth movement is more important in determining the rate of space closure than the particular technique used. Osteoclasts and osteoblasts must do their job; human premolar and molar roots can move bodily through bone at the rate of about 1mm per month. In most cases, movement faster than this amount means teeth are tipping into the extraction site. This type of movement is usually counter-productive.

Second, the arch must be completely leveled before space closure can occur. That means the practitioner must leave the working wires (usually .019x.025 st.steel in a .022 slot) in the arch passively for at least a month. Once the arch is leveled, space closure can commence.

Third, many practitioners inform me they prefer to close space on a round working wire (most commonly .020 st. steel in a .022 slot). They claim that friction due to the rectangular wire filling the slot inhibits space closure. I believe this is false. Closing space on round wire is usually not indicated for the following reasons:
1) Loss of torque control. Torque is the weak link of the pre-adjusted appliance. Closing space without torque control uprights anterior teeth. This gives the completed extraction case a “rabbitted” appearance- the teeth end up too upright. This is especially problematic in upper bicuspid extraction cases, as the uprighted maxillary anteriors can occlusally interfere with the lower anteriors.
2) Speed of space closure. The rate of ostoblastic and osteoclastic activity, not the amount of friction, determines the speed of space closure. (1) Controlled force levels on a rigid wire eliminate nearly all of the potentially deleterious side-effects associated with space closure mechanics. Remember, if the rate of space closure exceeds 1mm per month, the teeth are probably tipping into the extraction site. This is detrimental to the orthodontic result.

Fourth, many practitioners ask what is the best force system to use. Many systems work well, as the big issue is to provide adequate amounts of force after the arch has been leveled. I prefer en-masse space closure (moving the 6 anterior teeth as 1 unit) to canine retraction. En-masse closure takes full advantage of the principle of sliding mechanics, which is one of the big advantages of the pre-adjusted appliance. As for force application, many effective methods exist. Nitinol coil springs or active tie-backs are very effective. However, I like to use elastics. The proper force is usually provided by ¼" medium Class I elastics when the exraction site is larger than 4mm.When the site is 2-4 mm wide, switch to 3/16" medium. For the last mm or 2 of space closure, use chain elastic. My patients wear the elastics full time and change them every 12 hours. They attach the elastic from the hook on the canine bracket to the hook on the last bracketed molar. The anterior 6 teeth are held together (as 1 unit) by chain elastic or a figure-8 steel ligature tie.

Using elastics to close space provides the practitioner the flexibility to deal with many situations that arise during space closure. For example, if the molars are a little Class II, space closure can be accomplished by applying the elastics in a Class II direction. In fact, the practitioner can apply the elastics in virtually any configuration to close the space in the manner required in the individual case.

Delays in space closure
A couple of reasons exist which can cause delays. Often, upper premolar brackets are placed too gingivally. This results in over eruption of the premolars, resulting in occlusal interferences. Also, gingival tissue can build up in the extraction site, causing delays. In addition, dented or bent tubes or bracket slots can inhibit sliding. So if the space is not closing appropriately, check these three items. Chances are, you will discover the problem.

Reference
1. Miles PG 2007. Self ligating vs conventional twin brackets during en-masse space closure with sliding mechanics. American Journal of Orthodontics and Dentofacial Orthopedics. 132:223-225

Basic Considerations for Orthodontic Treatment

It is always beneficial to review the basics. A firm understanding of the basic tenets of orthodontic treatment enables the practitioner to achieve excellent results in most cases. The following rules are based heavily on the treatment philosophy of Drs. Bennett, McLaughlin, and Trevisi, who are the architects of the MBT treatment system.

Basic #1- Emphasis on dento-alveolar change
Orthodontic treatment predominately affects dento-alveolar structures. Growth modification (even if accomplished with functional appliances) results primarily in dento-alveolar development. It is true that some patients experience orthopedic changes, but the majority of change is still dento-alveolar.

Basic #2- The use of Light, Continuous Forces
Intermittent forces move teeth inefficiently. Heavy forces have been shown to damage root structure. Therefore, light, continuous forces maximize treatment efficiency. How can a practitioner be sure that he/she is using light, continuous forces? First never, never try to speed up treatment by forcing a wire into the bracket slot. Second, use a light, flexible wire until teeth are completely aligned (one of the most common mistakes I see is practitioners abandoning nitinol before alignment occurs). And third, use a wire progression that provides a slow increase in wire diameter so no wires are forced into the bracket slots.




Basic #3- Leveling and Aligning
If cases are leveled and aligned properly, mechanics become more efficient. About 1/2 the treatment time in a typical case is used to level and align (this includes bite opening or closing-see below). The following techniques aid in the leveling and aligning process:
-Use of nickel titanium archwires to relieve crowding.
-Use of bendbacks and lacebacks to control forward movement of incisors in extraction cases.
-Use of open coil springs to create space for blocked out teeth. When using open coil with the initial archwires, use only enough coil to provide a light force (the coil used is about 2mm wider than the space between the brackets where the coil is used). This will minimize distortion of the arch form.
-Early establishment and maintenance of arch form.

Basic #4- Overbite control
Getting the bite opened to the desired level before initiating other mechanics is a basic that many practitioners do not do. Strict adherence to this basic will really improve treatment results. The following procedures help the practitioner control overbite:
-Differential bracket positioning can account for about 5mm of bite opening, or 3mm of bite closing.
-In deep bite cases, bracket the 2nd molars early in treatment.
-Use of reverse and compensating curve (rocking chair curve) when the overbite is 6-9mm.
-Use tipbacks in a 2x4 or 2x6 set-up when the overbite is 10mm or greater.
-Be aware that in most cases, leveling and bite opening are not complete until rectangular wires have been in place for at least one month.
-Avoid leveling the Curve of Spee in open bite cases. Differential bracket positioning will greatly aid in maintaining the Curve of Spee.

Basic #5- Space Closure
A .019x.025 rectangular wire in a .022 bracket slot enables the practitioner to use sliding mechanics while minimizing archwire deflection and loss of torque control.
In most cases, en-masse space closure is preferred over canine retraction.
Many effective ways of providing force for space closure exist; elastics, chain, coil springs, and tie backs are most commonly used.

Basic #6- Overjet Correction
ClassII correction is accomplished by using a combination of ClassII elastics and functional appliances.
ClassIII elastics work well for mild to moderate ClassIII discrepancies.
Continuous forces on the dento-alveolar processes provide the best opportunity for overjet correction.

Basic #7 Finishing and Retention
Finishing involves correction of mistakes made earlier in treatment, particularly bracket position.
Let cases settle in light wires for at least 6 weeks prior to debanding.
Many practitioners advocate removing archwires for an additional 4-6 weeks to help determine retention needs for the case.
Retention is usually accomplished by using bonded retainers for the lower anterior segment, and acrylic full coverage upper retainers.
Wrap around upper retainers are used in cases that need additional settling; retainers with bite planes are use to retain deep bite corrections.

Final Considerations
#1 Position brackets properly. Pay attention to bracket positioning. Reposition brackets twice during treatment- after leveling and aligning (6-9 months into treatment) and before beginning finishing (4 months before removal).Use a panographic x-ray to evaluate bracket position when repositioning.

#2 Control arch width. Be aware of what you are trying to accomplish with arch width control (expansion, contraction, or maintenance of arch width). Co-ordinate all stainless steel archwires to accomplish your desired goals.

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#3 The basic plan for most cases is to first gain control of the teeth (wire progression), then do mechanics, and finally, give up control (finishing and retention). Get the bite open with brackets properly positioned before initiating mechanics. If you follow this general outline, your treatment efficiency and effectiveness will greatly improve.

Anchorage Control in the Early Phase of Bicuspid Extraction Treatment

In extraction treatment, every effort must be made to prevent the anterior teeth from moving forward during initial leveling and aligning. As the teeth are aligned using a flexible low-load deflection wire (such as a nickel-titanium alloy) the teeth tend to move forward (through air) rather than backward (through bone) into the extraction site. In addition, when using a pre-adjusted appliance,the tip built into the bracket is also expressed while using the initial archwire. Tipped teeth take up more space than do teeth that are upright. This space is also gained by the teeth moving forward.
This forward movement and resulting increase in protrusiveness is one of three aspects of the malocclusion that often worsen during the initial phase of extraction treatment.

The second unfavorable side-effect that often occurs early in extraction cases is unwanted bite deepening. The canines often erupt in an upright position in crowded cases. If a light straight wire is placed into a canine bracket when the tooth is upright, placing that wire through the incisor brackets will cause over eruption of the incisors and hence bite deepening. This is contra-indicated in most cases.The figure below demonstrates how this happens.





Third,the molar relationship often drifts toward Class II early in these cases. This is how it happens.
When an archwire is tied in to all the brackets, friction between bracket and wire plus the elastic or steel ties make the entire arch behave as one unit. Since the upper anterior teeth have more total tip than the lower anterior teeth, the upper teeth will move anteriorly more than will the lower anteriors. As the uppers move forward, they drag the molars with them (Remember, friction makes the arch act as one unit. The anteriors and posteriors move together.) The lower anteriors, because they have less tip, don't advance as much as the uppers, so the lower molars don't advance as much as the uppers. As a result, the molar relationship moves toward Class II.
These undesirable movements can be minimized by using anchorage control, which is defined as the maneuvers used to restrict undesirable changes during the initial phase of treatment so that leveling and aligning is achieved without the key features of the malocclusion worsening.
Two maneuvers make up anchorage control. The first technique is called a bendback. To use a bendback, simply bend back the archwire distal to the last banded (or bonded) tooth. This keeps the amount of wire from molar to molar constant, which helps prevent the teeth from advancing.








The second, and more important anchorage control technique, is called a laceback. Lacebacks consist of .010 ligature wire tied in a figure 8 fashion around the bracket on the last bracketed tooth up to the canine. The figure below illustrates how a laceback is engaged.




Lacebacks are tied in before engaging the archwire.Tie in the laceback, then tie in the archwire over the laceback. Tighten the laceback so it exerts pressure on the canine. This pressure not only prevents the canine from tipping forward (which would increase protrusiveness and deepen the bite) but also encourages the canine to move distally against the periodontal ligament.This creates about 1mm of space in the quadrant where the laceback is used.This space is then used as the teeth are aligned and correctly tipped. Clinically, light nickel-titanium archwires are capable of correcting about 2mm of crowding per month. This is exactly the amount of space one laceback in each quadrant will create. The space,because it is close to the crowding, is available for relief of crowding. Clinically, the crowding is relieved by using this readily available space rather than the the teeth moving labially.












After the canine is moved distally, the laceback loses its tension. This gives the teeth a chance to move into the created space. When the patient returns for a 4 week recall, tighten the lacebacks. This will create another millimeter per side (2mm total), that will be used for aligning and tip control. The lacebacks are tightened at 4 week intervals until aligning is complete. When the patient is ready for a wire progression, the lacebacks can be removed.

The net effects of lacebacks are the use of the extraction sites to relieve crowding and to allow the expression of tip, discourage bite deepening, and prevent the molar relationship from becoming more ClassII.

Here is an example of a laceback.













Lacebacks not only inhibit forward canine movement, but they are an effective way of distalizing the canines. This occurs because the lacebacks tip the canines at the gingival aspect of the alveolar crest. Due to the leveling effect of the archwire,the tooth rebounds as the roots tip distally.(1) A study by S N Robinson of 57 extraction cases showed lacebacks result in a net distal movement of incisors during resolution of crowding. This movement averaged over 1mm (remember, crowding was also relieved).In extraction cases without lacebacks the incisors moved forward almost 2mm.
The bottom line is that lacebacks make additional molar support (headgear, TPA's, or lower molar anchorage) unnecessary in most cases. Six to seven mm of arch length discrepancy can be corrected using this technique.

Questions
1) If the force exerted by a laceback cause the canines to move distally, why don't the molars move mesially because of the reciprocal force?
Answer- Clinically, it has been found the molars just don't move forward. The force level provided by the laceback is not enough to affect the large molar teeth.

2) Why not just use a chain elastic? It sure is a lot easier to tie in a piece of chain instead of having to manipulate the long steel ligature tie.




Lacebacks are effective because they don't produce continual forces. The space is created, then they stop working until they are re-activated. This light, intermittent force is probably the reason the molars are unaffected. Also, the heavier forces produced by chain will cause teeth to tip into the extraction sites (see photo). Lacebacks do not cause this worsening of the malocclusion.

1. McLaughlin,RP and Bennett,JC:The transition from standard edgewise to pre-adjusted appliance systems, JCO. 23:142-145,1989.