Saturday, December 22, 2007

Basic Considerations for Orthodontic Treatment

It is always beneficial to review the basics. A firm understanding of the basic tenets of orthodontic treatment enables the practitioner to achieve excellent results in most cases. The following rules are based heavily on the treatment philosophy of Drs. Bennett, McLaughlin, and Trevisi, who are the architects of the MBT treatment system.

Basic #1- Emphasis on dento-alveolar change
Orthodontic treatment predominately affects dento-alveolar structures. Growth modification (even if accomplished with functional appliances) results primarily in dento-alveolar development. It is true that some patients experience orthopedic changes, but the majority of change is still dento-alveolar.

Basic #2- The use of Light, Continuous Forces
Intermittent forces move teeth inefficiently. Heavy forces have been shown to damage root structure. Therefore, light, continuous forces maximize treatment efficiency. How can a practitioner be sure that he/she is using light, continuous forces? First never, never try to speed up treatment by forcing a wire into the bracket slot. Second, use a light, flexible wire until teeth are completely aligned (one of the most common mistakes I see is practitioners abandoning nitinol before alignment occurs). And third, use a wire progression that provides a slow increase in wire diameter so no wires are forced into the bracket slots.

Basic #3- Leveling and Aligning
If cases are leveled and aligned properly, mechanics become more efficient. About 1/2 the treatment time in a typical case is used to level and align (this includes bite opening or closing-see below). The following techniques aid in the leveling and aligning process:
-Use of nickel titanium archwires to relieve crowding.
-Use of bendbacks and lacebacks to control forward movement of incisors in extraction cases.
-Use of open coil springs to create space for blocked out teeth. When using open coil with the initial archwires, use only enough coil to provide a light force (the coil used is about 2mm wider than the space between the brackets where the coil is used). This will minimize distortion of the arch form.
-Early establishment and maintenance of arch form.

Basic #4- Overbite control
Getting the bite opened to the desired level before initiating other mechanics is a basic that many practitioners do not do. Strict adherence to this basic will really improve treatment results. The following procedures help the practitioner control overbite:
-Differential bracket positioning can account for about 5mm of bite opening, or 3mm of bite closing.
-In deep bite cases, bracket the 2nd molars early in treatment.
-Use of reverse and compensating curve (rocking chair curve) when the overbite is 6-9mm.
-Use tipbacks in a 2x4 or 2x6 set-up when the overbite is 10mm or greater.
-Be aware that in most cases, leveling and bite opening are not complete until rectangular wires have been in place for at least one month.
-Avoid leveling the Curve of Spee in open bite cases. Differential bracket positioning will greatly aid in maintaining the Curve of Spee.

Basic #5- Space Closure
A .019x.025 rectangular wire in a .022 bracket slot enables the practitioner to use sliding mechanics while minimizing archwire deflection and loss of torque control.
In most cases, en-masse space closure is preferred over canine retraction.
Many effective ways of providing force for space closure exist; elastics, chain, coil springs, and tie backs are most commonly used.

Basic #6- Overjet Correction
ClassII correction is accomplished by using a combination of ClassII elastics and functional appliances.
ClassIII elastics work well for mild to moderate ClassIII discrepancies.
Continuous forces on the dento-alveolar processes provide the best opportunity for overjet correction.

Basic #7 Finishing and Retention
Finishing involves correction of mistakes made earlier in treatment, particularly bracket position.
Let cases settle in light wires for at least 6 weeks prior to debanding.
Many practitioners advocate removing archwires for an additional 4-6 weeks to help determine retention needs for the case.
Retention is usually accomplished by using bonded retainers for the lower anterior segment, and acrylic full coverage upper retainers.
Wrap around upper retainers are used in cases that need additional settling; retainers with bite planes are use to retain deep bite corrections.

Final Considerations
#1 Position brackets properly. Pay attention to bracket positioning. Reposition brackets twice during treatment- after leveling and aligning (6-9 months into treatment) and before beginning finishing (4 months before removal).Use a panographic x-ray to evaluate bracket position when repositioning.

#2 Control arch width. Be aware of what you are trying to accomplish with arch width control (expansion, contraction, or maintenance of arch width). Co-ordinate all stainless steel archwires to accomplish your desired goals.


#3 The basic plan for most cases is to first gain control of the teeth (wire progression), then do mechanics, and finally, give up control (finishing and retention). Get the bite open with brackets properly positioned before initiating mechanics. If you follow this general outline, your treatment efficiency and effectiveness will greatly improve.

Friday, November 23, 2007

Anchorage Control in the Early Phase of Bicuspid Extraction Treatment

In extraction treatment, every effort must be made to prevent the anterior teeth from moving forward during initial leveling and aligning. As the teeth are aligned using a flexible low-load deflection wire (such as a nickel-titanium alloy) the teeth tend to move forward (through air) rather than backward (through bone) into the extraction site. In addition, when using a pre-adjusted appliance,the tip built into the bracket is also expressed while using the initial archwire. Tipped teeth take up more space than do teeth that are upright. This space is also gained by the teeth moving forward.
This forward movement and resulting increase in protrusiveness is one of three aspects of the malocclusion that often worsen during the initial phase of extraction treatment.

The second unfavorable side-effect that often occurs early in extraction cases is unwanted bite deepening. The canines often erupt in an upright position in crowded cases. If a light straight wire is placed into a canine bracket when the tooth is upright, placing that wire through the incisor brackets will cause over eruption of the incisors and hence bite deepening. This is contra-indicated in most cases.The figure below demonstrates how this happens.

Third,the molar relationship often drifts toward Class II early in these cases. This is how it happens.
When an archwire is tied in to all the brackets, friction between bracket and wire plus the elastic or steel ties make the entire arch behave as one unit. Since the upper anterior teeth have more total tip than the lower anterior teeth, the upper teeth will move anteriorly more than will the lower anteriors. As the uppers move forward, they drag the molars with them (Remember, friction makes the arch act as one unit. The anteriors and posteriors move together.) The lower anteriors, because they have less tip, don't advance as much as the uppers, so the lower molars don't advance as much as the uppers. As a result, the molar relationship moves toward Class II.
These undesirable movements can be minimized by using anchorage control, which is defined as the maneuvers used to restrict undesirable changes during the initial phase of treatment so that leveling and aligning is achieved without the key features of the malocclusion worsening.
Two maneuvers make up anchorage control. The first technique is called a bendback. To use a bendback, simply bend back the archwire distal to the last banded (or bonded) tooth. This keeps the amount of wire from molar to molar constant, which helps prevent the teeth from advancing.

The second, and more important anchorage control technique, is called a laceback. Lacebacks consist of .010 ligature wire tied in a figure 8 fashion around the bracket on the last bracketed tooth up to the canine. The figure below illustrates how a laceback is engaged.

Lacebacks are tied in before engaging the archwire.Tie in the laceback, then tie in the archwire over the laceback. Tighten the laceback so it exerts pressure on the canine. This pressure not only prevents the canine from tipping forward (which would increase protrusiveness and deepen the bite) but also encourages the canine to move distally against the periodontal ligament.This creates about 1mm of space in the quadrant where the laceback is used.This space is then used as the teeth are aligned and correctly tipped. Clinically, light nickel-titanium archwires are capable of correcting about 2mm of crowding per month. This is exactly the amount of space one laceback in each quadrant will create. The space,because it is close to the crowding, is available for relief of crowding. Clinically, the crowding is relieved by using this readily available space rather than the the teeth moving labially.

After the canine is moved distally, the laceback loses its tension. This gives the teeth a chance to move into the created space. When the patient returns for a 4 week recall, tighten the lacebacks. This will create another millimeter per side (2mm total), that will be used for aligning and tip control. The lacebacks are tightened at 4 week intervals until aligning is complete. When the patient is ready for a wire progression, the lacebacks can be removed.

The net effects of lacebacks are the use of the extraction sites to relieve crowding and to allow the expression of tip, discourage bite deepening, and prevent the molar relationship from becoming more ClassII.

Here is an example of a laceback.

Lacebacks not only inhibit forward canine movement, but they are an effective way of distalizing the canines. This occurs because the lacebacks tip the canines at the gingival aspect of the alveolar crest. Due to the leveling effect of the archwire,the tooth rebounds as the roots tip distally.(1) A study by S N Robinson of 57 extraction cases showed lacebacks result in a net distal movement of incisors during resolution of crowding. This movement averaged over 1mm (remember, crowding was also relieved).In extraction cases without lacebacks the incisors moved forward almost 2mm.
The bottom line is that lacebacks make additional molar support (headgear, TPA's, or lower molar anchorage) unnecessary in most cases. Six to seven mm of arch length discrepancy can be corrected using this technique.

1) If the force exerted by a laceback cause the canines to move distally, why don't the molars move mesially because of the reciprocal force?
Answer- Clinically, it has been found the molars just don't move forward. The force level provided by the laceback is not enough to affect the large molar teeth.

2) Why not just use a chain elastic? It sure is a lot easier to tie in a piece of chain instead of having to manipulate the long steel ligature tie.

Lacebacks are effective because they don't produce continual forces. The space is created, then they stop working until they are re-activated. This light, intermittent force is probably the reason the molars are unaffected. Also, the heavier forces produced by chain will cause teeth to tip into the extraction sites (see photo). Lacebacks do not cause this worsening of the malocclusion.

1. McLaughlin,RP and Bennett,JC:The transition from standard edgewise to pre-adjusted appliance systems, JCO. 23:142-145,1989.

Wednesday, November 14, 2007

A new, innovative product

Ortho Organizer's Ortho-Shield Safe-T-Tie elastic ligatures (1-800-547-2000 or have the potential to be a very useful addition to an orthodontic practice. These are elastic ties with anti-microbial properties. The ties have an anti-microbial silver with a timed release mechanism built into the elastic tie.
First, I'd like to address my concerns.The product information sheet calls the anti-bacterial product a "naturally occuring silver." What does this mean?
Second, the justification for using the product is based on a couple of case studies, not any scientifically justified documentation. How about doing a double blind study, measuring plaque reduction compared to a set of controls? I realize that the economic pressure to bring a new product to market is high, but we are obligated to our patients to be sure the products we use perform as advertised.
Concerns aside, I did try this product. We all know that decalcification as a result of poor hygiene is one of the biggest problems in orthodontics. If a way can be found to minimize decalcification, many patients will benefit. When I used these ties, the results were stunning. I used them on a couple of my poorest brushers, and checked them a couple of weeks later. Less plaque and better looking gingival tissue were apparent. I'll keep you posted as I see more results from this product.
Thes ties cost only between 5 and 10% more than regular elastic ties. They are light-activated, so you must keep them out of direct light during storage. They do come in special containers that keep the light out. They are only available in a couple of colors, but the company says more colors are on the way.
Please let me know if you have tried this product. If anyone is interested in helping design and participating in a study, contact me and maybe we can put someting together.

Tuesday, November 6, 2007

Arch Width Control

Along with good bracket positioning, good arch width control is one of the most important parts of quality orthodontic treatment. Proper arch width control starts with a good diagnosis. Does the patient require arch expansion, arch contraction, or maintenance of the existing arch form? Once this question is answered, some simple steps performed throughout treatment allow the practitioner to reach the treatment goals.

I alter all stainless steel archwires to help give the patient the desired arch form. If no expansion is desired, here is how I co-ordinate archwires.

1. Draw a line on the lower pretreatment model from the
buccal cusps of the posterior teeth through the incisal
edges of the anterior teeth

2. Co-ordinate the lower wire so it is 3mm wider than this line throughout
the circumference of the wire.

3. Co-ordinate the upper wire with the lower.
If no expansion is desired, make the upper
wire 3mm wider than the lower.

4. About 6mm of expansion (3mm per side)can be obtained with archwires alone. Simply expand each stainless steel wire used to the desired amount of expansion. If expansion in only one arch is needed (for example, correction of a narrow upper arch), just expand the archwires for that particular arch.

5. Any cases requiring more than 5-6mm of expansion need an expansion appliance (RPE,quad helix, or Schwarz plate). This should be determined during the initial diagnosis.
6. Molar area expansion is much less reliable than is bicuspid area expansion when using only archwires. A future posting will describe techniques for expanding the molar area with archwire bends.
7. Use a hollow chop pliers (or finger
pressure) when forming the wires. The
hollow chop is shown here.

Good arch width control techniques result in good interdigitation of teeth as the treatment progresses. Less elaborate finishing techniques and faster treatment will be the end result if these techniques are used.

Monday, November 5, 2007

Blocked out teeth

It is important to create space for blocked out teeth and get them into the arch very early in treatment. I start all my fully bracketed cases in either .014 or .016 nickel titanium archwires. I pack coil (.010x.030 stainless steel) to create space for any tooth that does not have enough space to fit into the arch.
Before I go into the details of packing coil, let's discuss this space creation. When packing coil, space is created by allowing the teeth to move anteriorly in the arch. If you are treating a case non-extraction, you must be willing to accept the fact that space will be gained at the expense of anterior teeth moving forward. For every millimeter that teeth move forward, about 2mm of space will be gained. If you decide to use a non-extraction treatment approach, you must understand and be comfortable with the fact that the anterior teeth will move forward during the initial aligning. If you are comfortable with this forward movement, non-extraction therapy is a good choice.

So, how do you pack coil? Here are the steps.
1. Visualize the arch from an occlusal view. If a tooth doesn't have enough space to fit in the arch form, you need to pack coil in that area.
2. Pack a section of coil that is 2mm longer than the distance between the adjacent brackets. For example, if the lower right lateral incisor is blocked out, pack a piece of coil that is 2mm longer than the distance between the distal of the bracket on the central, and the mesial of the bracket on the canine.
3. See the patient in 4 weeks and evaluate. If the space create can accommodate the tooth, engage the tooth. If the space is not big enough, pack a piece of coil that is 2mm longer than the one previously used.
4. Repeat step 3 until enough space is created.

Sunday, November 4, 2007

The Basics

Two of the most important aspects of orthodontic treatment are bracket positioning and arch width control. First, let's discuss bracket positioning.

Bracket Placement Review

A prominent orthodontic educator recently stated that "In the 1960's, the best orthodontics was done by the best wire benders. Today, the best orthodontics is done by the best bracket positioners." I couldn't agree more with this statement.

•Horizontal Positioning of Brackets
Visualize center of tooth directly from the facial surface, then look down long axis of the tooth
May need to use a mirror for bicuspids
Placement errors lead to rotations

•Rotational(axial) errors
Cause unwanted tipping
Keep incisal edge of bracket parallel to incisal edge of tooth
use same visualization techniques as for horizontal placement

•Excess bonding agent under the bracket
may cause rotational errors
To avoid these, push bracket firmly onto tooth

•Vertical errors
Cause excessive extrusion or intrusion
Check the same tooth on the other side of the arch and make sure the inciso-gingival position is the same on both sides- this prevents occlusal plane tipping

•Mesio-distal position
–Position bracket on the mesio-distal center of the tooth for all upper and lower centrals, laterals, and cuspids

-In most cases, position the brackets in the mesio-distal center of all molar and premolar teeth

Inciso-gingival position

•Deep bite patients
–Position brackets 1 to 2 mm incisal to the center of the tooth
•Open bite patients
–Position brackets 1 to 2 mm gingival to the center of the tooth

The pictures on the right show ideal anterior bracket placement for

average bite (top), deep bite (middle), and open bite (bottom).

Occluso-gingival placement of premolars

•Deep bite cases
–Position brackets 1 to 2 mm gingival to the center of the tooth
•Open bite cases
–Position brackets 1 to 2 mm occlusal to the center of the tooth

Upper molar bracket (or band) position
•Anterior portion of bracket bisects the MB cusp
•Final band seat is accomplished with lingual pressure
•Bracket in the occluso-gingival center for all cases

Lower molar bracket (or band) position
•Bracket always placed in the center of tooth
•Final band seat is accomplished with buccal pressure