Wednesday, June 17, 2009

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.