Sunday, November 7, 2010

Question: On a deep bite patient, I can't put brackets on the lower anterior teeth because the bite is too deep. Do you usually open up the bite by using bite opening techniques on the upper arch before bracketing the lower, or do you open up the bite using occlusal composites and bracket the lower at the same time as the upper?

Answer: I usually bond composite to the occlusal surface of the lower molars and bracket the lowers, then gradually reduce the amount of composite as the bite opens.

Question: Often, when I finish a case I have overbite problems. Why is this happening? I am bracketing 4.0 mm from the incisal edge on all teeth except for upper laterals, on which I place 3.5mm from the incisal edge. Do you think that is my problem?

Answer:It is probably more a mechanics problem than a finishing problem. Brackets must be positioned based on the characteristics of the case, not some pre-set number. If the bite is deep pre-treatment the anterior brackets must be placed incisally and the premolar brackets must be positioned gingivally. This will allow you to open the bite and keep it open. During the wire progression, slightly overcorrect the overbite. Get it to 1 or 2mm. This is impossible to do if you position the brackets in the center when the pretreatment overbite is deep. Often many docs place the lower incisal brackets too gingivally in an effort to prevent occlusal interferences. This cannot be done; the bite will deepen. To avoid interferences, bond composite to the occlusal surfaces of the lower molars. Successful resolution of many aspects of malocclusions depend upon getting the bite open before progressing to other mechanics. If you are not getting overbite corrected, you will have difficulty in correcting other aspects (overjet, midline, spacing) of the malocclusion.

Question: When I bonded a LR3, the patient felt it interfering. Should I lower the bracket for now or should I open the bite temporarily by placing occlusal composite? Where should I place it?

Answer: Do not change bracket position. NEVER compromise bracket position. A small amount of composite bonded to the occlusal surface of the lower molars will help clear the bite.

TMJ/Ortho relationship statement (references available upon request)

1) There is no evidence to show that any type of orthodontic treatment done reasonably well has anything more than a minor effect on the health of the TMJ.
2) There is no evidence available that shows that performing orthodontic treatment for the main purpose of improving TMJ health is a valid reason to do treatment. Orthodontic treatment does not seem to predispose subjects to TMD problems nor is it indicated as an initial therapy for TMD patients.
3) The connection between occlusion and TMJ problems is a very weak connection. Patients should be told the following statement: I don't want to lead you to believe that straightening teeth will eliminate jaw problems. However, people with straight teeth do have fewer problems.
4) There are some occlusal factors that show a higher risk for future TMD problems. They are
Skeletal open bite
Overjet greater than 7mm
CR/ICP discrepancy greater than 4mm
Unilateral cross bite
6 or more permanent teeth missing
Absence of anterior guidance is also linked (weakly) to future TMD probs.
To help make sure the patient has the best odds of not developing future TMD problems, if possible these malocclusions with one or more of these characteristics should be corrected. But, to say a particular type of treatment is better from a TM health standpoint is not a valid statement.

Question: In extraction cases, why do you go through all of the wire progression before doing mechanics? I have heard some practitioners suggest to do mechanics at .020ss stage, then continue on with .019x.025 niti and stainless steel after the mechanics are complete. Also what is the difference if I use a posted wire and K-module from lateral hook to the molar hook to retract the anterior teeth vs. using chain elastics 3-3 and then hooking the
K-module to the canine hook and the molar hook? Which is better?

Answer: Wire progression is one of the hot topics in orthodontics today. Personally, I like to do all (or most) of my mechanics on rectangular wire because of the torque and arch width control it provides. Some docs prefer space closure on 020 because it is quicker and requires less anchorage control. They say that there is less friction with a round (as compared to a rectangular) wire (anecdotal evidence supports this statement, but no well designed studies have shown a significant difference in friction between the two methods). Those who close space on rectangular wire believe the arch width and torque control that filling the slot provides is more important than reducing friction. Take your pick (choose on a case by case basis) but know that most orthodontic graduate programs teach rectangular wire space closure.

The force system you use really doesn't matter as long as it is the correct force. I like 200-250g for space closure. Power chain starts off with an initial force that is too strong for efficient space closure. Then the force level rapidly decays, which is why my use of it is limited to areas where I don't have to stretch it too much. K modules provide a more consistent force over a long period of time, so the system you described is a good way to close space
No space closure method is necessarily better, but each system has advantages and disadvantages. Your job is to understand these and choose the method of space closure accordingly.

Question: I am trying to close a 1mm diastema in between 8 and 9 on a 30 year old patient. Can I bracket 3-3 only or do I have to band the molars as well? Also, do I have to go through all of the wire progression?

Answer: Bracketing 3-3 (or 2-2 or even 1-1) only is often appropriate when closing a diastema. A limited wire progression is also OK. Finally, an occlusally directed gable bend placed between the centrals when closing the space will help place the roots in a position where relapse may not as easily occur.

Question: After bonding a LR2 I could not deflect the wire enough to engage the wire fully into the slot. Can I bypass this tooth and pack open coil to create a little more space?

Answer: Bypassing teeth on initial tie-in is an OK thing to do. You could also try a lighter wire (014 or 012 niti) instead of 016 niti.

Question: I have a 18y/o female patient who has a deficient maxilla and high palate. She has a bilateral posterior crossbite, and has Class I molars. I plan to use rapid palatal expander. Is it appropriate? If so, how many turns of screw are necessary?

Answer:I don't think it is appropriate to use an RPE in a physically mature patient, unless you perform surgically assisted rapid palatal expansion. If you must expand, use an appliance that tips teeth, as that is all you are going to get anyway. I like the quad helix for this situation.

Question: To perform an arch width analysis on the mandible, what is the distance I should measure according to USDI guidelines? Do I measure at the first or second premolars?

Answer: USDI guidelines for ideal upper arch width use buccal pit to buccal pit the first bicuspids. The measurement is 6 to 8 mm wider (depending on facial type) of the sum of the width of 4 incisors compared to the width of pit to pit. Width of the mandibular arch is more controversial. Not a lot of quantitative measurements exist. My personal opinion (supported by the vast majority of ortho literature) is that mandibular expansion in an adult (in fact, on any child over 9 years old) is not indicated. If you choose to expand the lower arch, you should prescribe lifetime retention.

1 comment:

John Moran said...

The article states that due to the high cost of the machine, doctors are forced to take scans on many patients that don't need them. So, they are giving you only that what your teeths really want.

Michigan Dentist