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.

Saturday, August 8, 2009

Still More Questions

I'm treating a 12 yr old female with mild crowding, ClassI dental and skeletal, deep overbite, some rotations, and a low mandibular plane angle. I've bracketed and banded, with differential bracket placement, and propped the bite open slightly with composite on the occlusal surface of the lower molars to accommodate the mandibular brackets. I’ve used 016 Niti for a couple of months. Now I notice the second molars are in crossbite. Do I bracket these now or wait? Any problems with merely bracketing these 7s at the next appointment? Or should I make some type of temporary bite plate to unlock the occlusion while I move them?

I would bracket the 7's asap, because not much will happen as far as correction of the deep bite/crossbite until you have control of the 7's. This happens a lot, and bracketing the 7's will solve the problem. There are no problems with waiting a month, but you are just not making any progress toward finishing if you don't bracket.

I have a question regarding differential bracket placement. I noticed that there is a line in McLaughlin's book outlining this, but in general he does not routinely use this procedure. Don't we want the brackets to be placed ideally relative to the incisal edge at the end of treatment to achieve a flat curve of Spee and ideal marginal ridge alignment? His technique seems to imply that ideal placement will usually flatten the curve and open the bite appropriately by that procedure only, perhaps followed by reverse curve in rectangular ss if needed. Is there a disadvantage to placing brackets differentially at the start of treatment?

McLaughlin does not use differential bracket positioning as much as I do. However, the last time I saw him speak (18 mo ago) he said he was leaning toward more differential bracket positioning, especially in the anterior. If you wait long enough, a flat wire with ideal bracket position will level the curve. In strong muscled patients, this may take a long time. I don't like curving rectangular wire (this does level the curve very quickly) because of the side-effects it produces.
I have found no disadvantages to differential bracket positioning. I continue to use this technique as I have for the last 20-plus years. In fact, I probably place my anterior brackets a little incisally on most cases, even those that do not require bite opening. My bias toward incisal anterior bracket positioning is due to the fact that the more incisally the bracket is placed, the more torque (positive labio-lingual inclination) is expressed. Since torque expression is the "weak link" of the pre-adjusted appliance, this incisal bias results in helping solve the most difficult problem (torque expression) in using the pre-adjusted appliance.

I heard a comment at a seminar regarding "round tripping”. I'm thinking that I should have used more bendbacks to inhibit the mandibular incisors from flaring forward. Do bendbacks inhibit open bites and excessive anterior flaring? If we want to control the mandibular arch length and shape, maybe bendbacks are appropriate. McLaughlin mentions bendbacks, and also mentions IPR. Perhaps he is thinking about preventing flaring of the mandibular incisors.
If we do bendbacks, how do we correct rotations and crowding especially if we use open coil springs? The space has to be gained somewhere! Maybe he's doing an arch length analysis, then IPR immediately in non-extraction cases, rather than gaining space through anterior tipping of the incisors, unless a more protrusive appearance is called for. You have said that you like to be in control. Maybe I need to control this incisor position more effectively, particularly in the mandibular arch during the first step. But how is this done?

When you treat a case non-extraction, you must be willing to accept the fact that to unravel the crowding, the teeth will move forward. If you don't want the teeth to move forward, then you must gain some space some way- stripping, extraction, expansion and/or distalization. Each of these modalities has problems associated with it. Moving teeth forward to unravel crowding is not round tripping, because, if the diagnosis is correct, you will not plan on moving the teeth back to their original position.
The big issue is diagnosis-where will the teeth end up with the plan you choose and is this right for the patient? There are many ways to get the teeth where you want to get them, but figuring out where they belong is the most important part.

I just started a case with an RPE. Last week the appliance fell out and the patient waited a couple of days to come in the office. I had a very difficult time recementing the appliance. Is this due to relapse? Patient activated appliance for 2 weeks and it is now passive. The appliance may fall out again. What should I do in this situation?

If you can' t get the appliance to fit well, first determine if the problem is lack of space for the molar bands. You could try placing spacers for a day or so before attempting recementation. If the actual expansion relapsed, turn the screw backwards for a couple of turns, then recement. If you are satisfied with the amount of expansion you currently have, make a Hawley retainer. Have the patient wear it full time for a few months. Then, bracket as usual.

I have a question regarding reverse and compensating curve. I placed curve in the maxillary arch. A month later, after I took out the 014ss there was no curve on the wire. Does the curve disappear after a month? Is there supposed to still be a curve after I take it out? There is a small space between 8 and 9; I take it that is from the flaring so I assume that the curve did do something. I tried to think back to your lectures but could not remember if you mentioned what the wire would look like after removing it.

Often the lighter wires will straighten out a little because they are held in a straight position (tied in) for a month. I would be more concerned with results- reduction of overbite- than how the wire looks when it is removed. That being said, the biggest problem most doctors have when using curve is they don't put enough curve into the wires, especially the lighter wires. Bottom line- what you have is probably OK. Just make sure you curve the .014's enough.

I'm working on a 4-bi extraction case. One of the max 2nd molars is partially buried with a 45% angle to the distal of the first molar. Do I attempt to bracket this now, and upright with Niti, or wait until space closure? Should I use another uprighting procedure? Will this issue resolve itself with slight mesial movement of the molar during space closure?

If the case is moderate anchorage, close the extraction space and the space gained in the posterior will allow for eruption. If it needs to be aligned, bracket the 7 during finishing.

I have a question regarding intraoral elastics. For Class II correction, what size do you usually use?

I most often use 1/4" medium, 1 elastic per side, full time wear, patient changes elastics every 12hrs, and eating with them in is optional.

When is the correct time to start the wire progression? What if brackets are improperly positioned? Do you reposition brackets before starting the wire progression?

Begin the wire progression when the niti arch wire fits passively into all slots. If brackets are improperly positioned, don't worry yet. You will reposition after a few months of wire progression. Your goal is to progress to larger arch wires. When the bracket slot is full (or nearly full), you will be able to see malpositioned brackets. It is much more efficient to reposition all brackets that need it at once, rather than doing one now, one next month, etc.

I find that I'm spending a lot of time coordinating .019x.025 st. steel. When I try to conform the 19x25 st. steel to my initial wire I use my fingers to shape it. Do you use pliers to do this? Because I am having a hard time accurately coordinating these wires, on one case I elected to leave the 19x25 niti in for the mechanics phase. If I do use 19x25 niti instead of the steel how long should I use it? 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 hollow chop pliers. (In the Ortho Organizers cat. it is Endura Pliers #201-401) It is tough coordinating these, but with practice, it can be done.
Often, I don't progress to rectangular stainless steel when there are no mechanics to do. If, for example, there is no space closure, midline shift, or Class II or Class III correction to do, I often skip the .019x.025 st steel and stay in .019x.025 niti. This has to stay in about 3 months to provide torque expression. When it is passive, it has done its job. However, don't get into the habit of doing complex mechanics on niti, because the side-effects of these mechanics are more easily expressed on the low-load deflection archwires.