Combination Active Anteriors and Passive Posteriors (CAAPP) combines early incisor control with ligated twin brackets and decreased resitance to sliding with passive self-ligating brackets on canines and bicuspids. Ligated incisors allow complete alignment with the smallest round archwires and also offer young patients what they want, coloured ligatures. See the article below for more on CAAPP.
"Compared with conventional brackets, self-ligating brackets produce lower friction when coupled with small round archwires in the absence of tipping and/or torque in an ideally aligned arch." 18
"Clinically effective torque can be achieved in a 0.022 inch bracket slot with archwire torsion of 15 to 31 degrees for active self-ligating brackets and of 23 to 35 degrees for passive self-ligating brackets with a 0.019 X 0.025 inch stainless steel wire." 19
Dr. Badawi 22, with help from the Department of Mechanical Engineering at the University of Alberta has built the most advanced orthodontic simulator to date. It generates real-time 3D displays of forces acting on every tooth simultaneously. They compared passive self ligated brackets to traditionally ligated twin brackets in a high canine malocclusion. "The total resistance to sliding in the brackets posterior to the maxillary right canine was less than the resistance mesial to the canine; this meant that the wire will preferentially slide through the canine, first premolar, and second premolar brackets rather than sliding through the brackets from the maxillary right lateral incisor to the left second premolar." This supports the CAAPP system of brackets.
The goal of "Incisor Targeting" is to align the teeth as quickly as possible with the lightest round archwire available (currently .012 nickel titanium) and then gain third order control of the incisors with a full sized stainless steel arch wire. In this "race to fill the slot" we make the track shorter by using an .018 slot and "shifting gears" only twice, from round wire to .014X.025 nickel titanium, and then to .016X.025 stainless steel. If the second molars require a lot of movement we use an .018 nickel titanium transition wire between the .012 nickel titanium and the .014X.025 nickel titanium arch wires. (Dr. Ricketts was doing essentially the same thing when I began studying orthodontics thirty years ago.)
"All or None Ligation" involves maximum deflection of the lightest nickel titanium archwire by ligating it to the base of the incisor bracket slots. Initial tooth movement often involves incisor proclination as well as canine and bicuspid expansion due to "U" shaped archwires. This movement requires archwire feeding through the canine and bicuspid convertible tubes and the molar tubes with as little resistance to sliding as possible. There is still periodic binding friction due to the archwire contacting the bracket slot as the tooth tips and uprights. Occlusal forces and the "jiggling" of teeth is probably the reason that we can move incisors rapidly with only 50 grams of force from a .012" niti archwire 14 when in theory the 50 gram per tooth ligation force should prevent tooth movement with an archwire that light.
Resistance to sliding in a ligated twin bracket with a small round archwire = braking friction from ligatures + binding
Resistance to sliding in a passive self-ligating bracket with a small round archwire = binding
The goal of lighter forces is increased patient comfort and decreased root resorption. Clinical tooth movement involves orthodontic forces as opposed to physiologic or natural eruptive forces. We can get an idea of how much heavier orthodontic forces are compared to physiologic forces by measuring root resorption 20. Harris 9 found that the mean cube root volumes of the resorption craters in the light force (25 grams) and heavy force (225 grams) groups were about two and four times greater than in the control group, respectively. In another study from the University of Sydney, Barbagallo 13 found the light-force teeth had approximately five times more resorption than the control teeth. The heavy-force teeth had about nine times more root resorption than the controls. The lightest arch wire available is the .012 nickel titanium which delivers a force of approximately 50 grams or twice what the above studies considered a light force. The .014x.025 nickel titanium arch wire is the lightest arch wire available which "begins to fill" the slot in the edgewise dimension. It delivers approximately 328 grams of horizontal (in/out) force which is greater than the "heavy" force in the above studies. Current orthodontic forces are not physiologic forces.
The following is an example of rapid proclination and alignment of lower incisors with an .012" nickel titanium archwire in .018" slot CAAPP.
______________________________After 2 months with .012 niti, day of .018 niti placement____After 1 month of .018 niti, day of .014X.025 niti placement
Extraction vs Non-Extraction
In a bicuspid extraction case retract the canines with elastic chain on the lightest (.012 ") niti archwire. The low-force deflection of the .012 niti archwire causes less binding than a larger archwire. The canine is distalized by the elastic chain but there is still first and second order control, mainly from the molar but also to a lesser degree from the bicuspid and incisors. If a larger archwire is used the binding increases and the canine has to tip to decrease binding before it distalizes unless the elastic chain force is high enough to overcome the binding.
The following is a bicuspid extraction case showing rapid alignment with an .012 niti and light elastic chain. We did not want to procline incisors with the shallow overbite.
Initial
1. Indirect bonding 2. Extractions 3. .012 niti archwires placed
3 weeks later. Begin light elastic chain under the .012 niti archwire.
6 weeks later. Day of change to .018 niti archwires and begin light vertical elastics from upper canines to lower canines and first bicuspids.
4 weeks later. Day of change to .014X.025 niti archwires. Continue light vertical elastics. Note incisors are completely aligned before rectangular wires are placed. The rectangular niti wires are used to develop arch form, expand the bicuspids in a non-extraction case, begin torque control, and prepare for the .016X.025 stainless steel archwires
The above patient is an obvious four bicuspid extraction case. The more difficult cases from a treatment planning point of view are borderline extraction. In these cases we often begin non-extraction and consider extracting four bicuspids late in treatment if there is too much lip protrusion. This adds approximately 6 months to the treatment time to close extraction spaces. The following photos are the before and afters of Case 3 in the following article from the Cerum Orthodontic Insight newsletter . This is an example of a borderline extraction case where we did not extract based on lip fullness. Total treatment time was 16 months.
The next patient is an example of a borderline extraction case where we decided to treat non extraction based on the esthetics of the smile, archform, and the deep overbite. The lower archform is constricted so expanding the archform allowed us to treat that arch non-extraction. This may be less stable but permanent retention is probalbly indicated whether we extracted or not. Treating the lower arch non-extraction results in proclining the lower incisors which helps reduce the deep overbite. Expanding the upper arch advanced the lateral incisors to bring them into the same plane as the central incisors which is important for the smile. Treatment time so far is 9 months.
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The following article is reprinted from the Cerum Orthodontic Insight newsletter.
