Saturday, March 3, 2012

More Questions and Answers

I have a concern about this case. She has 016 nitinol in both upper and lower arches. Her right side looks good. My question involves the slight open bite on the right side. When and how should I correct it? Should I wait until I get to a stiffer rectangular wire, then use elastics?

There are two reasons why the bite is open in the canine area. First, the wire is not completely unloaded. It needs more time to totally straighten. In other words, if you look at the shape of the wire between the lateral and 1st bi, it is not straight, but still slightly rounded. It will be straighter after another 4 weeks, so the lateral open bite will be less. Second, the bracket positioning is contributing to the problem. Overall this is a beautifully bracketed case-clean and accurate. Good job! However the canine bracket is a little too incisally placed for a case that needs virtually no bite opening. Because of this it is not erupted enough. Reposition the bracket 1.5mm to the gingival and your problem will be solved.
The bite opening in the premolar area occurs because Newton’s 3rd law always works. The opposite reaction to pulling the canine down is an intrusive force on the premolars and lateral incisor. This minor movement will resolve when you use stiffer wires. Settling issues such as these are more easily corrected in light wires as opposed to stiffer rectangular wires as you suggested. The stiff wire will overpower the elastics, rendering them ineffective. That is why many times problems such as these are corrected during finishing. The lighter wire, combined with finishing bends, may be enough to help this case settle. If finishing bends alone don’t solve the problem, use finishing elastics in addition to the finishing wire.

Thanks for taking my call the other day; look at this case and note how his bite is not opened sufficiently; additionally he's popping off lower anterior brackets quite frequently. You suggested to return to 016 stainless steel with curves to open the bite. I did this earlier in the treatment and followed the 016 wire with 020 stainless steel with curves. His bite simply won't open (he appears to have strong musculature). I continued treating him with the 50% overbite. I moved on to rectangular wires, placed composite on the lower 1st molars to open the bite, and began space closure. As I close the space, he is still popping a lot of brackets off. At his most recent visit, I placed composite on the 12yr molars to further open his bite. I also removed the composite off of the 6yr molars. This resulted in a posterior open bite. What should I do? On the phone you recommended I go back to 016S with deep curve to open bite...but somehow I don't think it will work. Is bracket positioning the problem?

Your bracket placement is good- the inciso-(and occluso-) gingival position of the brackets on each individual tooth is consistent. Additionally, your bracketing technique appears to be good because the lack of excess cement around the brackets shows that you are cleaning up well. I would probably have placed my upper 3-3 brackets much more incisal- 2 or 3 mm more incisal than you have them- but I don't know if it's worth repositioning all of them at this point. I guess that if all else (see below) fails, I would reposition.
I don't want the uppers to flare so I would not curve the upper wire. (Remember, intrusive forces create the potential for labial crown rotation.) Keep the curved lower wires in until the overbite is 2mm or less. This will take some time. Also, I would bond more composite on the lower molars to open the bite more. This takes occlusal forces out of the game and bite opening will proceed more quickly. Use deep curve in an 016 stainless steel in for a month followed by moderate curve in 020st steel for a month. If this doesn't completely open the bite, increase the curve in the 020 until it is open. Do no upper space closure until the bite is open- that is until the overbite is 2mm or less. Again, NO space closure until the overbite is corrected (don't cheat-it's tempting).
Do you have double buccal tubes on the lower molar bands? If so you may want to consider an overlay utility wire to intrude lower anteriors. This is very complex stuff so it would require a lot of communication between us. Try the curves 1st and evaluate the overbite in 3months.

I have a question regarding molar band and bracket position; especially the second bicuspid brackets. I often find I have problems when I cement molar bands and bond brackets. After I cement the molar bands, I bond the brackets starting with the central incisors and working towards the second bicuspids. I often see large discrepancies of the wire slot height between the molar band and the second bi bracket slot even though the molar bracket slot is positioned close to the middle of the tooth. This happened when I banded and bonded Sarah's teeth today and I had to remove and recement (more occlusally) the molar bands so they were more even with the second bi bracket slot. I do measure the height of the teeth on the model before bracketing so I know how far to bond from the incisal/occlusal aspect. Do I just need to eyeball the molar band position better? Are there any tips or tricks to minimize the molar to second bicuspid discrepancies?

The most important consideration is to use a molar band that is the correct size. Many clinicians use bands that are too large; this causes the band to slide gingivally resulting in the problem you described. If the correct band size is selected, it is much easier to position the band, and hence the bracket, correctly. They just don't slide too gingivally very often (one exception may be when the upper 1st molars have a large 5th cusp). From a mechanical standpoint this is often deleterious to the case because the molar will over erupt and roll in lingually when the bands are too gingivally positioned. This can result in narrowing of the arches which can lead to a whole host of problems (difficulty in ClassII correction comes to mind).
Fitting bands well requires good spacing. Make sure the spacers have worked. If you are forced to wiggle a band through a tight contact, only a band that is too large will get through the contact point because you need "wiggle space". This will result in the band and therefore the bracket being positioned too gingivally. If you don't have space you can bond 5-5 and replace the spacers and reappoint for band seating.
Many clinicians bond in different ways but I like to bond starting with the upper left 5 then work around the arch. I usually seat bands after bonding is complete. That way the patient is "freshest"-most cooperative and not experiencing a lot of salivary flow- when bonding. Finish the bonding, take a break (this is a good time for some hygiene instruction) then band. After all the brackets are placed it is easier to see if the molar band is positioned correctly because you can compare it to the rest of the brackets.
The bottom line is this: a good fitting molar band will automatically result in correct bracket placement. The only way to fit molar bands correctly is to have good spacing. So make sure those spacers are used properly and a lot of problems will be solved.

When you make an occlusally directed gable bend, is the apex or tip directed occlusally (as in an upside down triangle)? Why can’t I just close the spaces on a rectangular wire to avoid detorquing problems? At what stage of the wire sequence can I start closing anterior diastemas? I have a case where I am using .020 stainless steel wires with rocking chair curve on the lower to open the bite. The patient has upper anterior spacing from 3 to 3 (spaces were present pre-treatment). Can I close these spaces at the same time while I am opening the bite with the .020 SS? What is the best way to close the spaces? Can I also correct midline discrepancies at this stage of the wire sequencing while opening the bite?

If the space is small (3mm or less) I usually close on 020stainless steel. Close larger spaces on rectangular wire. The reason for this is a lot of space closure on round wire may result in detorquing of the upper anterior teeth, which may be unaesthetic. There is much less loss of torque when closing spaces on large (019x025) rectangular wire. Detorquing is always a problem with chain on round wire. Therefore, if the space is too big, closing on rectangular wire is a good idea. For large (greater than 4mm) diastemas, close the space on large rectangular wire until the space remaining is 2mm. Then use .020stainless steel with a gable bend between the centrals. When closing diastemas on round wire, I often place an occlusally directed gable bend (center bend) between the centrals. The apex of the "V" is directed gingivally. This separates the roots and brings the crowns closer together (tips the roots distally and the crowns mesially) which makes the space closure more stable. Root position is very important for long term stability of the space closure. Closing only a couple of millimeters on round wire with chain doesn't significantly affect the torque. Use chain to close spaces (3-3 for small spaces and 6-6 for larger spaces. Use 6-6 to prevent spaces from opening distal to the canines).
If there is spacing, midlines can be aligned at the 020 stage by shifting teeth if the midline shift is only 1 or 2 millimeters. If the spacing and/or midline shift required is more than 2mms, use chain on rectangular wire to make the correction. Again, prevent loss of torque by closing more than 2mm of space on rectangular wire. Use chain for this procedure. If no spacing exists, use some combination of ClassII, ClassIII, and oblique elastics to shift the midline. When doing this, remember to “skew” the archwire (expand the side of the wire in the direction you want the midline to shift).

I repositioned the lower right 2 about 1 mm gingivally to help lock in the occlusion. I used .016 nitinol on the lower and .016 stainless steel on the upper. I want to increase the overbite by 1 to 2mm. Should I reposition the upper anteriors gingivally or can I use a triangular elastic to bring them down? Also, the lower right 6 is tipped lingually. How do I upright this? Will this be corrected once I shift to rectangular wire? Do I still need to use rectangular wire if I don’t need to change the torque of the teeth?

The bite is slightly open because the bicuspid brackets(especially the upper) are a little gingivally positioned, which results in a small amount of bite opening. I wouldn't reposition brackets because the bite will settle and deepen a little after removal. Finishing (step up bends in the lower anterior and step down bends in the upper anterior) combined with finishing elastics on a finishing wire (I like 018 stainless steel) will increase the overbite by 1 to 2mm.
The lower 6 often rolls in (rotates lingually) because the bracket is positioned too gingivally. That causes extrusion and therefore lingual rotation (remember any extrusive force has the potential to create a lingual rotational tendency, or moment). The bracket must be repositioned 2mm towards the occlusal. Either use direct bond a bracket or fit a new band.

After I change the band on the 6, should I use a .016 nitinol or I can go straight to a finishing wire (.018 stainless steel)? How long before this molar uprights? After removal of the braces, will the bite settle if I use both upper and lower full coverage plastic retainers? If no torque change is required, do I need to use rectangular wire?

Reposition the band, go to 016 nitinol for a month, then to finishing wires. The molar will take 6 weeks to upright. If it doesn't upright as a result of bracket repositioning, use rectangular wire (019x025 nitinol is effective)for 6 to 8 weeks. You will need torque control (rectangular wire) in this situation about half of the time. No rectangular wire is necessary if the torque is OK, provided you don’t have to do any mechanics such as Class II correction or space closure. Applying elastics or chain may cause a loss of torque so do these mechanics on rectangular wire, even if the torque is acceptable. Remember, it is far more difficult to reestablish torque than it is to maintain it.
Finishing bends are used to resolve minor settling issues. One of the reasons I like a lower 3-3 lingual bonded retainer is because settling can occur. Essix (clear plastic full coverage)upper and lower retainers don't allow this. Many clinicians make a lower 3-3 Essix to solve this problem. I don’t like these retainers because of their size (they are so small that they don’t seem to fit as well as the full coverage retainers). They are also tough to make. However, the Essix manual does recommend lower 3-3 plastic retainers so it may be something you want to try.