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.


1 comment:

Blogger said...

I've just installed iStripper, and now I can watch the hottest virtual strippers on my desktop.