INVISALIGN FUNDAMENTAL PRINCIPLES
So let’s start with the actual principles and then slowly describe and define what I mean by them. The basic fundamental principles of using Invisalign are as follows:
- NO. 1: ALIGNERS ONLY WORK BY PUSHING TEETH; THEY DON’T PULL
- NO. 2: MULTIPLE MOVEMENTS AT THE SAME TIME
- NO. 3: ANCHORAGE IS REQUIRED FOR EFFICIENT MOVEMENT
- NO. 4: OVER-ENGINEERING CLINCHECK IS A MUST
- NO. 5: TEETH NEED SPACE TO MOVE
PRINCIPLE NO. 1: ALIGNERS ONLY WORK BY PUSHING TEETH; THEY DON’T PULL
What does that mean? Isn’t the idea behind orthodontics that we’re pull- ing teeth in different directions? In the case of clear-aligner treatment and what you’re trying to do requires an understanding about one key thing:
It’s very important to recognize the push surfaces on either the teeth themselves or on the attachments placed on teeth to get the desired movement. We need the interaction of an aligner surface with the tooth or active surface of an attachment to achieve movement. Pulling won’t work — an aligner surface that is pulling will simply disengage from the tooth. So remember, we’re pushing NOT pulling. It’s one of the main rea- sons that extrusion of maxillary lateral incisors is so challenging — there is essentially nowhere for the aligner to “grab” on either the labial or pal- atal surface. We will look at this problem in depth in the chapter on verti- cal control of teeth and I will offer solutions to improve maxillary lateral incisor tracking, but the fundamental concept is this: If you can develop an appropriate push surface on a tooth, the chances of the tooth moving in the desired direction increase greatly.
So think PUSH, and you are on your way to looking at ClinCheck in an entirely new way.
CASE STUDY NO. 1 — PUSH SURFACE
This was a teen patient treated in one year with no refinements. The teeth tracked very well because of the large push surfaces. Look at image 1-3 and notice the upper canines. See the broad, flat labial and palatal sur- faces? The aligners were able to produce a set of opposing push forces on each tooth, and the upper canines tracked well (image 1-4)
PRINCIPLE NO. 2: MULTIPLE MOVEMENTS AT THE SAME TIME
The second principle, multiple movements at the same time, speaks to one of the benefits of the Invisalign system — its efficiency. In the sam- ple ClinCheck (see sequence of photos, images 1-5 through 1-7), you can observe that you can simultaneously torque teeth, rotate and align them. Let’s take a look at Erin.
CASE STUDY NO. 2 — ERIN
Let’s take an example of what we mean by multiple movements at the same time. In this case study we have a patient named Erin. She present- ed with a Class I malocclusion, which you can observe in image 1-8, a deep overbite and cross-bite of the upper-right canine. Erin’s case illustrates multiple movements being done at the same time. As you can see in the sequence of ClinCheck photos the work being done is to simultaneously intrude the upper-right and the upper-left central incisors while at the same time correcting her cross-bite.
The ClinCheck plan actually shows what is happening with this pro- cess. Observe intrusion of the two upper-front teeth to level the smile arc. This procedure is done at the same time that the upper-right canine is being moved buccally out of cross-bite.
The key takeaway: The orthodontist does this all at the same time — and that is what I mean by the efficiency of the process.
Here is the final picture at the end of Erin’s treatment (image 1-9). She has a normal occlusion, and we have achieved a good final result.
PRINCIPLE NO 3: ANCHORAGE IS REQUIRED FOR EFFICIENT MOVEMENT
The term “anchorage” is used all of the time with conventional fixed appliances.
I use the term a little differently for the Invisalign system. When I refer to anchorage, a good example of that would be Haley’s case (image 1-10). Haley presents with a significantly deep overbite. In her case, the goal is to correct the deep overbite with a combination of 30-percent intrusion of the upper incisors and 70 percent of lower incisors.