JCO Interviews Dr. Thomas D. Creekmore on Torque
JCO How important a factor in torque is bracket position on the tooth?
DR. CREEKMORE It is supposedly very important, but I have not used a constant position of the bracket on the tooth. I find the variation too great from patient to patient. Some patients have very short clinical crowns, especially upper laterals, and you can't place the bracket far enough gingivally. So, there will be cases in which the brackets are placed pretty far incisally. In others they may be in the middle third, where I would prefer them to be. But it doesn't really seem to matter clinically. Torquing capability of the appliance, by just torquing the archwire, isn't hampered even though the bracket is more incisal than normally preferred.
JCO Well, if you are putting 7° of torque in and you want 7° instead of 9°, you could make more of a variation than that just by the way the bracket sits on the tooth.
DR. CREEKMORE But, you probably could not tell the difference between 7° and 9°. Maybe between 7° and 22°, but not between 7° and 9°. The play between the wire and slot alone makes a great difference. The play using an .018 X .025 wire in an .018 X .025 slot is 2°. That is the manufacturing tolerance. If you have two incisors, one inclined labially too much and one inclined lingually too much, if you put an .018 X .025 wire in an .018 X .025 slot, then the one that is inclined labially will come within 2° of where you want it to be and the one inclined lingually will come within 2° of where you want it to be. Without an adjustment, the two teeth will be 4° off from each other. So, even finishing with a full size wire in the slot, adjustments have to be made to compensate for the play of the wire in the slot to get the teeth where they should be.
But, let's look at what some others use. An .018 X .025 wire in an .022 slot has 15° of play. So if you have 7° of torque on the central, 3° on the lateral, -7° on the cuspid, -7° on the bicuspid, and -10° on the molar, none of these teeth would be influenced by an .018 X .025 wire in an .022 X .028 slot as far as torque is concerned, because the play is greater than all the torques you have in the slots. If you go down to an .016 X .022 wire in an .022 slot, there is almost 27° of play. With an .019 X .025 wire in an .022 slot, there is 10½° of play. So again, all of the torques I mentioned are ineffective with an .019 X .025 wire in an .022 slot. With an .0215 X .028 there would be 2° of play and you would begin to have a semblance of a fit.
An .016 square wire in an .018 X .025 slot has almost 17° of play. Using 22° of torque on an upper incisor bracket, at most you would get 5° of effective torque. It is interesting that .017 X .025 wire has 4.5° of play in an .018 slot, whereas an .018 square wire has only 3° of play. So, you would have better torque control with an .018 square than an .017 X .025.
In an .018 slot, an .017 square wire has 8° of torque play, whereas an .016 X .022 has 9° or 10° more play. Yet, the .017 square is more flexible than the .016 X .022 and has more torque control.
Also, the rotational control is enhanced in the square wire. However, the flaring of molars is worse in .017 square because the .016 X .022 is stiffer in that plane.
I use an .017 X .022 wire for closing and opening. It has only 5° of play. As far as flexibility is concerned, the .018 square and .017 X .022 would be almost the same, but the .018 square would have better torque control. The .017 X .022 is stiffer in the rotation plane, .022 versus .018, but about the same in the bending plane.
JCO How does Andrews' work in torque differ from yours, and how does that of Ricketts differ from you both?
DR. CREEKMORE When I devised the New Torqued Technique, my approach to finding the torques was to place bands on extracted teeth and tie them into a flat, 0° torqued, archwire and see where the teeth went. I did the same with the dies of the indirect band technique. I also looked at Andrews' research and generally agreed with what he found. My upper torques are essentially the same as Andrews'. I differ with him to some extent on torques for the lower teeth. Andrews' angulations on both the upper and the lower are different than what I have. Andrews' original non-extraction setup tips lower molars and bicuspids forward 2°, whereas I tip them back. He now has several different setups for different extraction-anchorage situations.
Compared to Andrews and myself, Ricketts' torques are high in the anterior and low in the posterior, and the play between the slot and the wire limits the effectiveness of the torque cut in the slots. His angulations also differ from mine.
It is interesting that Ricketts uses 22° on the upper central, 14° on the upper lateral, and 7° lingual root torque on the upper cuspids, so the difference between the cuspid torque and the incisor torque is 15°, between cuspid and lateral it is 7° and between lateral and central it is 8°. In Andrews' appliance and in mine, we have 7° on the upper central, 3° on the upper lateral and -7° labial root torque on the upper cuspid. So, there is 14° of difference between cuspid and central, 10° between cuspid and lateral, 4° between upper central and lateral. There is not a great difference among Ricketts, Andrews and myself if you consider the differences in torque on upper centrals, laterals, and cuspids. To evaluate an appliance, not only should one consider brackets, torques, and angulations, but also the archwires used during treatment.
As far as angulations are concerned, if you use a twin bracket appliance, it doesn't make a lot of difference what size wire you finish with. Because the brackets are so wide, there is very little tipping play, and angulation is going to be established even in the smaller wires. Not so for single brackets. Tipping play is excessive in small wires. To capture the tip built in, requires finishing with a full-sized wire for the slot. But for torque, it makes a lot of difference what wires are used in getting torque in finishing, whether you use single brackets or twin brackets. If you are using an .022 slot and finish with an .018 X .025 wire, there is so much play (15°) that the wire must be overtorqued by 15° to get what you want.
JCO How can you give everybody the same torques, when the surrounding structures and the orientation of the denture is so variable?
DR. CREEKMORE You just can't do it. They end up differently, even though you think or try to give everyone the same.
JCO What, then, would you say is the advantage of a pretorqued appliance?
DR. CREEKMORE Basically, you are trying to put the teeth in the ballpark of where you think they should be for a majority of people. But it is not automatic and it is not universal. You still have to treat that individual to give him optimum esthetics. It puts most of the adjustments into the attachments so that your archwire adjustments are minimal and easier to accomplish. It also cuts treatment time and this is an economic factor. For all these reasons, pretorqued and preangulated appliances are a modern trend. But, a sophisticated appliance doesn't help a careless operator. All the built-in effects can be lost, for example, by misplacement of brackets on the teeth.
To me, a pretorqued appliance is an efficiency device by simplifying archwire construction. It doesn't necessarily make the treatment better. It makes it easier. Auxillary personnel can fabricate a closing loop archwire from a preformed, 0° torqued archwire. The orthodontist can make simple individualizing adjustments, if required, and then the wire is tied in. In the finishing wire, you work from a flat preformed archwire, which simplifies archwire construction. If need be, you can individually torque one tooth, or two centrals, or two laterals, or four incisors. Those are the ones you have to torque the most because of the tremendous variation.
JCO Not every set of teeth torqued to the same extent will look the same. How much of a factor is that?
DR. CREEKMORE Your clinical judgment decides on degree of torque. I have pretorque built in, but in every case I have to evaluate the way it looks and adjust for my perception when necessary. Most of the time I may not have to add more torque. But, for example, if lower incisors are too procumbent in a nonextraction case, you have to put labial root torque in to get those teeth where you want them. If upper incisors are too upright and you are moving them forward, you have to add torque. A passive wire isn't going to prevent a molar from rolling mesially. You have to overdo wherever necessary, so it isn't automatic by any means.
JCO The position of the denture in the face and skull can make a great deal of difference in torque requirements.
DR. CREEKMORE Yes. If the occlusal plane is canted down more on one patient than another, to get the incisors relative to the lip and to the face would require a different torque than one in which the occlusal plane is much flatter. This is a factor. But, I think the major factor is where the teeth started and what you are doing in treatment. In some nonextraction cases, the teeth start out pretty good and do not move very far and, consequently, you don't need as much torque. In other cases, you may have to move the teeth a long way. If teeth must be retracted a long way, they will tuck under more and the roots will be more prominent. So, where the teeth started and where you are moving them seems to make the greatest difference in the amount of torquing requirements. If you are opening spaces, incisors will become more procumbent. In closing arch length, incisors tend to tuck under. If you have to retract cuspids a long way, the roots tend to become more prominent. Generally, most torque variation is in the anterior teeth and the farther back you go, the less variable the adjustments are for torque.
JCO How do you control the amount of torque force applied to a tooth?
DR. CREEKMORE The force value that you obtain when you engage the wire depends on how far the wire deflects and the interbracket width. The greater the distance between brackets, the more the wire can be deflected and still produce the same force.
JCO Do you ever use a key to engage a wire for torque?
DR. CREEKMORE Oh yes. A key or a Tweed plier.
JCO Do you ever feel that this is too much force?
DR. CREEKMORE In my technique, I don't get to an .018 X .025 wire until I have been through a round and an .017 X .022. In the .017 X .022 wire in a single .018 bracket, you can put 20° or 30° of deflection and engage the wire without a great deal of force. Remember, an .017 X .022 wire in an .018 slot only has 5½° of play, so we are getting a lot of effective torque. But, overall, I have not really found that you put too much torquing force on teeth. If you can deflect the wire enough to engage it without taking a set, you are not putting too much force on; and, if the wire takes a set, it reduces the force.
JCO Does the amount of force you put on one tooth affect the torque you get on adjacent tooth or teeth?
DR. CREEKMORE It has to. If you get an action on one tooth, you get a reaction on the adjacent tooth.
JCO How long should torque take?
DR. CREEKMORE It depends how far you have to go. Generally, in an .018 X .025 archwire, if the teeth are not obviously tucked under, the torques will be passive in four weeks. I am not in finishing wires very long. If I am not where I want to be in four weeks, I adjust the torque and, in another four weeks, I should be there. If teeth are tucked way under and you need to torque 5-7°, that may take three months to accomplish. You can insert the wire and let it go. The force will be effective for three months.
JCO What about relapse of torque? Do you overtreat torque to account for some rebound?
DR. CREEKMORE I don't purposefully overtorque a noticeable amount. Generally, the amount of rebound I expect is only the amount of space closure. My tendency is to put more in the archwire than is needed and let it run until it gets where I want it and then I stop it. Torque to me is a clinical judgment. You assess it visually. You palpate the roots.
JCO How about unwanted movements resulting from torque?
DR. CREEKMORE I tie back the archwire in the finishing stage when spaces are closed. If I do not tie back in the finishing stage, the teeth will space. As far as extrusion is concerned, I think it is minimal in the finishing stages. Torquing the four incisors with an arch that spans back to the molars would give you molar extrusion. But, if you have the cuspids and bicuspids tied in, the force is distributed over the whole arch and the molars can't extrude. So, with a full strap-up, torquing movements have virtually no ill effects that I can observe clinically as far as extrusion and intrusion is concerned. You would have to change the cant of the entire occlusal plane.
JCO Unless, of course, you got hung up on the cortical plate and established some anterior anchorage.
DR. CREEKMORE If you have teeth tucked way under and have to do a lot of lingual root torque, then there definitely is a mesial component of force and you have to resist that with headgear or Class II elastics or let it slide forward.
JCO Are you being successful torquing bonded brackets?
DR. CREEKMORE Yes. I can handle torquing just about the same with bonded brackets as with bands. The archwire should be inserted into the slots and then tied rather than pulling the archwire into the slot with the tie wire. Another difference in technique with bonded brackets is in the first wire. You have to use a little softer tie, because initially you are rotating and a rotating force is a straight outward pull on the bracket--the weakest link for bonded brackets. The relative force value with a single bracket compared to a twin is also evident in bonding success. With a single bracket, you cut the force value by a third for the same size wire. So fewer bonds are broken on the very first wire.
JCO Are there occlusal considerations such as cuspid rise and anterior guidance that influence torquing in a certain way?
DR. CREEKMORE I think so. My rationale on torque is, first give the teeth the normal look. If you study untreated good occlusions that are esthetically pleasing, they also function well, so we emulate that. However, good esthetics does not insure good function. It's easy to straighten the upper teeth on the upper jaw and the lower teeth on the lower jaw, but if the upper and lower teeth don't harmonize with each other when the mandible is in centric relation then function will be poor. This is the most difficult part of orthodontics, harmonizing the upper and lower teeth to each other with the mandible in centric relation. If this harmony is established then the natural "settling-in" of the teeth after the appliances are removed will produce good function in most cases. Exceptions to this are open bite type cases which don't "settle-in". Therefore their finished occlusion with appliances should be more precise.