When we are resolving crowding we have to take into account the patient’s periodontal condition. A short list of things to consider are as follows:
Tissue type — does the patient have thick or thin periodontal tissue? As a rule of thumb patients with thick tissue can withstand more expan- sion and more proclination than a patient with thin, friable tissue.
Recession — does the patient present with areas of gingival recession? In these cases, one has to ask, “How far can I move this tooth labially in the presence of gingival recession before the situation becomes worse?”
Mucogingival Problems — if a patient presents with zones of inad- equate attached gingiva we have to consider whether we can procline or move teeth labially or expand buccally at all. In these cases, would pretreatment gingival grafting change the treatment plan?
Fenestrations — could labial movements in the presence of bony fen- estration of the labial plate invite disaster? Patients who present with significant gingival recession on the facial surface of the teeth have the potential for compromised amounts of labial bone as well. In patients that present with bony fenestration, wanton or unlimited expansion in the posterior or anterior part of the mouth can be disastrous, leading to worsening of the periodontal issues.
When we are thinking about resolving crowding we also have to think about how the upper teeth are going to occlude with the lower teeth. Things we have to consider are setting up patients for:
- Incisal guidance
- Canine guidance
- Fremitus — we want to set up patients so their occlusion has no ab- normal fremitus at the end of treatment.
- Abfraction — does the patient present with any cervical abfraction lesions, which may be related to abnormal occlusion?
- Non-working interferences
- Centric relation where in these cases we are looking to create a cen- trically related occlusion.
The best way to think of esthetic implications is to consider the den- ture setup. When denture teeth are being set up, traditionally the first teeth to be set are the upper central incisors. We have a very good reason for this consideration. We want to set up the upper incisors for the best esthetics — Incisal display both at rest and while smiling, as well as for lip support. In addition, the upper incisors are set for ideal phonetics.
In a denture setup as well as an orthodontic setup, we want to accom- plish the following:
- Set up patients with a pleasing amount of gingival display not either excessive or insufficient.
- Gingival margins to be level and symmetric.
- The smile arc of the upper incisors should follow the curvature of the lower lip.
- Limited amounts of negative space for a full smile.
- The position of the anterior teeth should support the upper and lower lips.
It’s no different with Invisalign treatment. The final position of the teeth are dictated by the same esthetic considerations as the denture set up. Just as if a lab prescription for a denture would be inappropriately worded, “Please set up straight teeth,” the ClinCheck instructions must be precise and specific to achieve optimal esthetics for the Invisalign patient.
Additionally, when we are treating patients orthodontically, we also want to take into consideration areas of papilla loss/dark triangles. We will discuss this in detail in the chapter on IPR.
At the beginning of this chapter, I made the statement that the in- structions, “Level, align and de-rotate all teeth” should be eliminated from your lexicon. I hope that the proceding brief discussion of the ma- jor implications to consider when resolving a patient’s dental crowding illustrate this point.
What does “level, align and de-rotate teeth” even mean? To me, these instructions are not only vague and imprecise, they also do not help your technician to understand how the teeth will align and where they will wind up in their final position. Your technician is very skilled at setting up your ClinCheck plan, and the more specific your instructions are the better they will be able to produce a ClinCheck treatment plan to achieve the results you want. It is incumbent upon the doctor to make the critical treatment planning decisions and then communicate these decisions effectively to the technician. Fundamentally, this is one of the central themes of this book.
As for planning unlimited expansion and proclination into every ClinCheck treatment plan without IPR, please consider the following brief literature review.
In 1997, Burke and Associates published the paper, “A meta-analysis of mandibular inter-canine width in treatment and post-retention” in The Angle Orthodontist. The authors looked at 26 different studies all essen- tially asking the same question:
If the distance between the mandibular canines is expanded during or- thodontic treatment what happens during retention and what happens in post-retention?
The authors concluded, “Regardless of treatment modality, if man- dibular inter-canine width is expanded during treatment, it will contract during post-retention and return to the pre-treatment dimension.” Based on these findings, if we endeavor to improve the chances of long-term stability for our patients, maintenance of the mandibular inter-canine width should be a central component of the routine ClinCheck set up.
What about posterior expansion distal to the canines? In a brief re- view of the literature, consider these papers:
- Walter, American Journal of Orthodontics, 1962
- Shapiro, American Journal of Orthodontics, 1974
- Gardner and Choconas, Angle Orthodontist 1976
- Glenn, Sinclair and Alexander, American Journal of Orthodontics, 1987 These four articles discuss long-term stability where teeth posterior
These four articles discuss long-term stability where teeth posterior to the canines were expanded. My interpretation of the data indicates that although all expansion tends to relapse, inter-canine width expansion shows the least stability while expansion of the premolars and molars shows the potential for less post-retention relapse. Ideally, we don’t want to expand cases at all, but in cases where we feel compelled to do it, we are going to at least invite the possibility of improved long-term stabil- ity when we expand the teeth posterior to the canines and not expand inter-canine width at all.
If look at your Invisalign Doctor’s Site (IDS) there are “Clinical Preferences” where you can set your default arch expansion parameters. Go into your Clinical Preferences on the homepage of the Invisalign Doctor’s Site. Here are my recommendations:
Select: Increasing the arch width between premolars and molars only (based on research that shows we have a fighting chance of better stability there).
Click on: 2+ mm per quadrant
CASE STUDY NO. 1 — JESSICA
Jessica was a teenage patient who presented with a CL I malocclu- sion, with moderate upper and lower crowding. Note the severely ro- tated upper canines. She has moderate lower anterior crowding and a normal profile (images 3-1 through 3-3). I would consider Jessica to be “Invisalign Teen low-hanging fruit”. She is a high school student who does not want braces for the prom or class pictures. These patients tend to be very compliant with Invisalign Teen.
Here is the ClinCheck list in reference to Jessica’s crowding.
- I have determined that Jessica will be treated non-extraction.
- The crowding will be resolved from a combination of the following:
- Posterior expansion
- Incisor proclination
One of the beauties of 3D controls in ClinCheck Pro is that the doctor can dial in different amounts of expansion, proclination and IPR to get the de- sired results. You have the ability to virtually treat the patient and custom- ize the ClinCheck set up before treatment begins. This truly revolutionary technology allows you to control the final outcome as well as the path the teeth travel from beginning to end. In Jessica’s case, I want to maintain her mandibular inter-canine width to try and improve her chances for long-term stability. Based on this, I made the decision to balance posterior expansion, anterior proclination, and IPR to resolve the crowding.
CLINCHECK TREATMENT PLAN
Her ClinCheck plan was set up with posterior expansion, proclination of select lingually positioned lower incisors and anterior IPR from canine to canine to resolve the crowding. If you look at the position (image 3-4) initially of the lower right central incisor you can note that tooth is placed somewhat labially out of the arch. Since this tooth is too far to the labial, the treatment plan is to move this tooth lingually during treatment.