Wednesday, August 26, 2009

Another Round of Questions

What should be corrected first- overjet, overbite, or midline discrepancies? Do you correct one at a time or all at the same time?

1) Always correct overbite before overjet. Overbite is corrected during the wire progression (.014,.016, and .020 stainless steel). Use curve if the pre-treatment overbite is 6mm or greater.
2) Overjet, midline correction, space closure, and other aspects of the malocclusion (except for overbite, which is done earlier) are corrected in the mechanics phase- after the wire progression. Correct these aspects of the malocclusion in .019x.025 stainless steel, because this wire provides very good control. By following these guidelines, most malocclusions can be corrected efficiently.

I have created enough space by using coil springs and have engaged the crowded teeth. I have used .016 Niti for 3 weeks since coil springs were removed. The lower centrals have flared excessively. This concerns me. I have used .016 Niti for 5 months. Is this too long? Also, should I be doing anything at this point the get those lower centrals back where they belong? How do I do this? Do I use power chain?

You were probably a little too aggressive in your use of coil springs; that is, the coil springs you used may have been a little long. Short term excessive flaring of the lower incisors is usually not a problem, unless anterior gingival recession occurs. If recession has occured, use chain to retract the anteriors. If no recession is apparent, align the incisors (remember to use steel ties if the wire is not fitting passively into the slot when you are using .016 niti), then begin the wire progression. The incisors may settle back on their own. Don't use chain until you are in a much heavier wire (.019x.025 stainless steel is best) because the force levels exerted by chain are very high. Five months is not too long to be in .016niti- a mistake I often see is doctors progress out of niti too quickly. Remember, open coil spring is used to tease the teeth apart; you don't need to pack a lot of coil to gain space. As a general rule, the coil is 2mm longer than the distance between the adjacent brackets. Every month, use a spring that is 2mm longer than the coil used in the previous month. Discontinue coil and engage the tooth when there is enough space in the arch to fit the previously blocked out tooth.

After using 016 niti for 6 months, I started a wire progression on a 13 yr old patient. Everything looks OK on the upper (coil springs to create space). But the lower left lateral, even after all this time, still is rotated. Additionally about 1.5 mm of crowding still exists. I was not sure what to do, so I started a wire progression (.014 ss). The wire is slightly kinked in (I had to push it slightly to fit into the bracket slot). I know that the wire has to be passive to maintain arch integrity. As of now, the crowding will not allow the LL2 to fit in the arch. Did I not create enough space with the open coil? Should I have done IPR before progressing to 014ss? Did I progress to .014stainless steel prematurely? Could I pack coil later, say in .020 stainless steel, and create space? Does this method create space too late? Is it as efficient as creating space in .016 niti?

If, as you say, there is still 1.5mm crowding, you have not yet created enough space to bring this tooth into the arch. Use coil to gain more space. Rotations are nearly impossible to correct if there is not enough space in the arch. If there is enough space, it is much easier to engage the tooth with niti. Then the correction of the rotation will proceed uneventfully.
Many doctors will progress up a wire progression, bypassing severely rotated teeth. Once they get to a heavier wire (.016 stainless steel or heavier), they will pack coil a little more aggressively to create enough space for the rotated tooth. Then after enough space is created they will step back to niti and engage the rotated tooth. This method results in less arch distortion, but it takes a little longer. You never want to kink a stainless steel wire. It will not return to its original shape so it will not move the teeth efficiently.
IPR is an option in this case. If the tooth is thinner, it will fit into a smaller space. The problem with IPR on rotated teeth is the inability to access the contact point, which is the area where you want to do IPR. So do the IPR only after space is created and you can get at the contact point.

After full banding, can we give the patient a bite plane until an anterior crossbite is corrected, or is it OK just to let the braces move the teeth?

In general terms, a bite plane will, because it eliminates interferences, allow the teeth to move more quickly. In my experience, patients in braces don't wear bite planes very well. The teeth move a little, and, as a result, the bite plane doesn't fit. That being said, a lot of orthodontists use bite planes. I prefer to open the bite by bonding composite to the occlusal surface of the lower molars. The bonding can be done quickly, it is not removable by the patient, and it is easily removed by the doctor after the occlusion improves. Kids tolerate the change in occlusion well, but adults hate it. So I'm a bit more discriminating when I'm considering this on adult patients.

I've been putting second molar brackets on my patients, and find that they report a lot of soft tissue irritation. I know about using ortho wax, and I always encourage patients to use it to intercept problems before irritation occurs. Do you have soft tissue problems with second molar brackets, and do you use the smaller ones, or the larger first molar brackets to get more surface area for bonding?

I usually use the smaller bracket because of irritation issues. Remember, on the upper it's OK to use 1st and 2nd molar brackets interchangeably, but on the lower it is not. The prescription is different on the lower 1st and 2nd molars-more lingual crown torque is present in the lower 2nd molar brackets than the lower 1st molar brackets.

How do I change the molar relationship from a full cusp (8mm) ClassII relationship to a ClassI molar relationship in a non-growing patient?

In a non-growing patient, it is very difficult to change a full cusp (8mm) Class II molar relationship to ClassI molar relationship. So most of the time we don’t try (don't fight molar relationship, especially in non-growers, is a statement with which most orthodontists would strongly agree). Usually in these kinds of cases, keep the molars in ClassII. Do this by taking out only the upper 1st bicuspids and retracting the anterior segment. The molars stay in ClassII, but the canines end up in ClassI and the overjet is corrected. Typically in these cases, the upper anteriors are protrusive, so taking out upper bicuspids provides space for retraction of the upper anteriors. Often, problems arise with these cases if the bite is deep. It is more difficult to open the bite in extraction cases than in non-extraction cases.
Anchorage control is very important in upper bicuspid extraction cases. The molar relationship is ClassII, so additional mesial movement of the upper molars is contraindicated. In addition to lacebacks in the initial stage of treatment, some method to prevent this forward upper molar movement must be used during space closure. Trans-Palatal Arches, Nance buttons, headgear, and banding or bonding the upper 2nd molars are all treatment modalities that are used to increase posterior anchorage during space closure.

What do you use to rotate a tooth? Recently, I bought some rotation wedges. Do you recommend using these and how do you use them?

I'm not a fan of rotation wedges. They are tough to put in and they don't stay in very well.I prefer to create space with coil, then after space is created, while still using a flexible arch wire such as .016niti, tie the tooth in tightly with a steel tie.

I have a case where tooth #7 was in lingual cross-bite. I brought the crown into the arch, but the root did not translate- that is,the root is still facially inclined. First, I repositioned the bracket several times and I placed a .016x.022 stainless steel wire, but the lingual root torque has not occurred. How do I correct the root torque? I think some doctors place the lateral brackets upside down in these situations. I did that for a few months in the .016 niti, but the root just did not move lingually. This is very frustrating. Do you have any thoughts on this?

You need lingual root torque on the lateral. The lateral incisor bracket that I use has 10 degrees of labial crown torque (which is the same as -10 degrees of lingual root torque) so the bracket will not move a root lingually very easily (the bracket prescription does not encourage lingual root movement). If you put the lateral bracket on upside down, the torque changes to -10 degrees, which results in a situation that encourages lingual root movement. Remember, for torque to be expressed, you must use a rectangular wire. You cannot torque teeth on a round wire. Even a .016x.022 does not fill the slot enough to affect torque very quickly. Get into .019x.025 (preferably stainless steel) and torque will be expressed.

I have a patient that started with 7mm of overbite. I curved the upper wires, and the bite has not opened enough. Should I use .016x.022 rectangular wire with curve?

As a rule, I don't like to curve rectangular wire. If the bite needs further opening, try curving the .020st steel a little more, and use .020 stainless steel with a little deeper curve on the lower as well. Stubborn deep bites are the result of an incomplete leveling of the curve of Spee. Lower curves will solve this. If, after a couple of months, the bite is not open, bracket the 7's (I usually direct bond them). Erupting 2nd molars often is the best way to get the bite opened. A word of advice: do not do any other mechanics until the bite is opened. Do what it takes (and be patient!) to get the bite opened before progressing in the case. You will save a ton of time in the long run.

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