Tech tip: FAQ about IPR

We sent out a survey recently asking doctors for their questions about IPR.

DrMah.jpegIn this week's tip, we've consulted with our Chief Technology Officer, Dr. James Mah, to get answers to your questions.

IPR and the treatment setup

ClearCorrect's role is to help you create the treatment setup you want for your patient. We can offer recommendations for the course of treatment for your patient, but those recommendations are never absolute. It’s up to you to make any necessary changes to customize an ideal treatment plan for each individual patient.

We can adjust all preferences related to IPR (which teeth, when and how, no IPR, expansion, limited IPR, limited expansion, etc.) or engagers based on your specifications. Just let us know what you want when you submit your case or when you review your treatment setup.

Questions about how much IPR to perform

Why do your IPR instructions always call for 0.3 mm?

If we don’t receive specific instructions from you on the amount of IPR you want done, we will go with our default increment of 0.3 mm IPR per interproximal each step. In some situations, we may recommend smaller increments of 0.1 or 0.2 mm of IPR.

These 3 increments of space can be created predictably if the right tools are used:

  • 0.1 mm of space is predictably created with hand stripping.
  • 0.2 mm can be predictably created with a single-sided diamond disc.
  • 0.3 mm can be predictably created with a double-sided diamond disc.

Doing any more than 0.3 mm of IPR at once to one interproximal is prone to problems. We usually recommend IPR in 0.3 mm increments to account for potential accumulated errors, such as:

  • When IPR is not performed correctly, the diamond disc can flex and create a “V” shape space which appears to be larger than it actually is. 
  • Hand stripping requires some force applied to the strip towards the tooth that needs reduction.  This force will sometimes move the teeth, which will make the space bigger. This space makes it look like the required tooth reduction occurred, when in fact it did not. Instead the teeth just shifted around to create space. When the aligners are put on the teeth, the space will be smaller than what is needed. 
  • A similar problem also happens when doctors force an IPR gauge into a space. They may think there is proper amount of reduction when all they really did was just move the teeth around.

Is it better to do IPR up to a point to correct rotations or to flare out to the labial?

This depends on the patient and the specific teeth. Clinician and patient preferences play a key role in determining the course of treatment. The treatment setup is your treatment plan and you are at liberty to make specific requests related to your individual patient.

How do I know when to do more or less IPR than scheduled?

Again, it depends on the specific situation. When considering IPR and the patient in front of you, you must understand that you are dealing with a biological system as opposed to a manufactured part. There are anatomic, biologic and patient variations at play which produce varying results. You will need to continue to follow what is happening with the patient and oversee treatment to obtain optimum results.

Also, knowledge of dental anatomy is important. Incisors have less enamel than other teeth and do not allow for as much IPR. Intra-oral radiographs can be used to check the amount of available enamel before submitting the case or performing IPR.

How do you measure the amount of IPR?

gauges.jpgThere are a few ways to check the amount of IPR:

  • IPR gauges (such as the ones sold by ClearCorrect) are commonly used.
  • Some dentists use the thickness of the IPR strip as a gauge, knowing that it is 0.1 mm thick. If you fold the strip over, it produces a thickness of 0.2 mm and one more fold results in 0.3 mm.
  • Some dentists use the width of the disc in the same manner.

I occasionally have difficulty with angulation of cuts, overlap, rotated teeth, access, insufficient space and possible over-reduction of one approximal surface vs. another. What should I do about this?

In some situations, it may be necessary to slightly procline the teeth and improve alignment before performing IPR, so that the appropriate tooth surface is reduced. For this reason, some clinicians prefer to perform IPR over several visits.

Scenarios like this are why many doctors do not schedule IPR at the first aligner appointment. Orthodontic tooth movement results in minor tooth mobility which allows for easier IPR.

If access is an issue on posterior teeth, you can request no IPR in posterior areas when submitting your case or reviewing the treatment setup.

What do I do to get exactly the same amount of reduction along the whole interproximal space?

When performing IPR you need to make sure that the strip or disc is completely through and past the contact point, and that the strip or disc is applied uniformly during the process. One common error is excessive tooth reduction above the contact point, leading to a “V” shaped interproximal gap.

The goal of IPR is to reduce tooth size while maintaining the original morphology of the teeth. In other words, smaller contact points between incisors should remain as such and not be flattened into broad ones. If in doubt, it is easier to carefully go slower with a strip than it is with a rotary disc.

Tight contacts make it difficult to perform IPR and for this reason, some clinicians prefer to start moving the teeth and take advantage of the associated tooth mobility before performing IPR. Another option is to start the IPR with a strip to overcome the tight initial contact and subsequently use the burr or disc.

Do you keep track with the total amount of IPR being performed throughout a case? My only concern is that at times it seems IPR is being done on the same teeth, and I worry about the patient having sensitivity due to loss of enamel.

Screen_Shot_2016-03-11_at_11.55.21_AM.pngClearCorrect represents the amounts and locations of recommended IPR on the treatment plan and treatment setup.

Our technicians usually won't recommend more than 0.3 mm IPR mesial of the canines, or more than 0.6 mm IPR distal of the canines and mesial of the first molars, unless specifically requested by the doctor. We have found that those values are conservative enough to maintain the enamel structure and to satisfy most doctors that have concerns about reducing too much enamel.

These default values are smaller for anterior teeth, because they have less enamel than posterior teeth. These values also take into consideration how the tooth will look at the end of treatment. 0.3 mm of IPR in the anterior is only 0.15 mm on one tooth, if a double-sided diamond disc is used. 0.6 mm of IPR in the posterior is only 0.3 mm on one tooth, if a double-sided diamond disc is used. Since posterior teeth can have more enamel removed, you can go back and round out the square corners by contouring after using the diamond disc.

Besides our recommendations, you should also keep track of the IPR that is actually performed on each patient. We have an IPR Tracking Chart that can help you monitor this. Each time you perform IPR it should be recorded and correlated with specific patient tooth morphology (check intraoral radiographs for thickness of enamel). 

Questions about IPR and spacing

The majority of the time you ask for a 0.3mm reduction but every time I create the 0.3mm, I end up with spaces and have to ask for more trays to close that space. Why is this?

There are several possible reasons that you may have ended up with spacing after doing IPR:

  1. Patient non-compliance.
  2. Teeth can shift unpredictably in treatment. Always be aware of this and only do IPR when it appears necessary, using the treatment plan amounts as a guideline. Your technical expertise and judgment takes precedence over any IPR recommendations.
  3. Technicians are working with digital images vs. the actual patients, so the instructions are an imperfect estimate of the amount of IPR that will actually be needed.
  4. Space closure in deep/heavy bite patients is difficult.
  5. Problems in impressions can result in inaccurate digital images.
  6. More than the required amount of IPR may have been erroneously performed.

Before performing IPR at any stage of treatment, you should check the patient’s mouth to see if treatment has been progressing as planned.

Interproximal contacts should be checked with dental floss at every visit and if the contact is not closing, you can request a digital power chain to close residual spaces.

What if I'm sure I opened the space to the prescribed amount, and when I get a notation to check for closed contacts, it's still open? If patient compliance is not the issue, should we go on to the next step, or try the current aligner for a longer period?

If patient cooperation and aligner fit are not issues, continue with treatment. The periodontal tissues are still remodeling and the residual gap may close later in treatment. Check the contact often and if it remains after alignment is achieved, request a digital power chain to close up residual spaces. 

I am concerned about creating a narrower interproximal space with less space for gingival tissue on some teeth. I still don't find any of the methods to do IPR perfect. They all present risks of iatrogenia and don't allow us to preserve the ideal tooth anatomy.

Generally interproximal tissues will remodel to accommodate the new tooth positions and there will not be any gingival excess. However, in some situations, such as the maxillary midline, this may be an issue requiring gingivectomy. 

However, these issues are all according to your preference. You can specify less IPR or no IPR when you submit the case or evaluate the treatment setup.

The hand system wears out pretty quickly and doesn't always create enough space. Some teeth can be stubborn to move and need more space, especially when the teeth are really crowded. What do I do when this happens?

This could be the result of clinical technique. Reviewing the different IPR techniques might be helpful. It could also be affected by the choice of which strip to use (course/medium/fine). These variables should be considered when performing IPR.

Questions about contouring and IPR

How do I create a natural contour instead of just a flat side?

When contouring, knowing the various IPR techniques available to you and using the one most applicable for the case at hand is important to achieve the desired result. Using hand strips after use of a diamond disc can help with rounding out some corners.

It also may be necessary to slightly procline the teeth and improve alignment before performing IPR so that the appropriate tooth surface is reduced, and then perform IPR over several visits.

General concerns about performing IPR

I get worried about the accuracy of the proposed design.

This is why it is important to see patients on a regular basis to oversee their treatment progression. Additionally, this is a concern of many doctors when first performing IPR. With more cases, treatment, and experience, this concern fades.

I find using diamond saws very scary. It’s easy to create a bloody mess in a blink of an eye. The patients really dislike the sound of the diamond blade hacking away at their dentition. It takes a lot of effort to even start the pass thru. The feel of grit and the taste of blood make them want to run.

Knowing the various IPR techniques available to you and using the one most applicable for the case at hand is important in scenarios where you have a nervous or scared patient. There are multiple available techniques for IPR (manual strips, discs) that doctors can choose from. Dentists have varying levels of comfort with each system. The choice to perform IPR or not is entirely up to you. You can always make custom requests regarding IPR when you submit your case or review the treatment setup.

How do I reassure my patient I'm not hurting or damaging the teeth when I do IPR?

Discuss enamel thickness and dental anatomy with the patient. You can let the patient know that occlusal enamel reduction through everyday chewing is a normal occurance that happens as the patient gets older. If this is a significant issue for the patient, one alternative is arch expansion to reduce or eliminate IPR. However, there are also compromises and risks involved in arch expansion.

I would like to know more about when it is appropriate to do a little unscheduled IPR to help prevent teeth from getting off track.

During every visit you can check for excessively tight contacts with dental floss. If you find that tight contacts are an issue, you can perform a little hand stripping to help keep treatment from going off track.

Should the IPR gauge fit tightly or passively?

It should be fairly passive as a tight fit will result in compression of the PDL and natural tooth mobility may be confused with available space.

We hope you found this information helpful! There's lots more where this came from—check out our Help Center, which is filled with useful information for treating your patients with clear aligners.

Also, don't miss our upcoming advanced training webinar on IPR or our advanced training series of webinars on various topics related to clear aligner treatment.

Until next time…

Tech Tip: Using IPR to avoid case revisions

This tech tip is an oldie, but a goodie.

Sending in a case revision before doing some troubleshooting can waste money and chair time. We see a lot of case revisions submitted when unpredictable tooth movements (such as extrusions and rotations) just aren't happening. Teeth need space to complete any type of movement, and when they don't have enough, it can cause tracking or fitting issues. These tight contacts are common and can appear at any time in treatment, due to the nature of teeth and the patient's physiology.

Even if you follow the treatment plan to a T, and the patient is completely compliant, you may still need to perform IPR.

You can avoid submitting an unnecessary case revision by using these IPR techniques:

  • Always check for tight contacts before submitting a case revision. You can easily alleviate tight contacts by hand stripping, as demonstrated in our IPR tutorial video.
  • Take IPR into your own hands! The recommended amounts of IPR in the treatment setup and treatment plan are for guidance only. You are the doctor, and are the one ultimately treating the patient. Small amounts of unscheduled IPR can get treatment back on track much quicker than submitting a lengthy case revision.
  • Use your good sense -- don't perform IPR in a spot where there's already space, even if it's recommended on the treatment plan. Too late? Don't worry, it's an easy fix. At the end of treatment, the spaces caused by doing too much IPR can be closed with a digital power chain in a refinement.
  • If you still have questions, we have articles in our Help Center dedicated to performing IPR and troubleshooting other related issues. Or, you can alway contact a knowledgeable support rep; they will help you review your patient's treatment so you can decide what to do next.

We hope you found this information useful!

Also, don't miss our upcoming advanced training webinar on IPR or our advanced training series of webinars on various topics related to clear aligner treatment.

Until next time...

Tech Tip: Tight Contacts

What are tight contacts?

Tight contacts exist when there is tension between two teeth and it is undetected by impressions and 3D models. 

Here's an example of tight contacts:

0.3mm of IPR is requested between teeth 8 & 9, but there is tension (hidden pressure) between 9 &10.  When space was created with 0.3mm of IPR, the pressure was released between 9 & 10 now creating normal contact levels since tooth number 9 has been given space to move over. This means depending on how much tension was between 9 & 10, the IPR space is now smaller, 0.2 or 0.1mm, but still not the amount required by the treatment plan.

Causes

Tight contacts between teeth exist naturally due to the patient's dentition (crowding in the arch) which will then cause the teeth to become active (spring loaded) once space is created during orthodontic treatment.

One of the consequences of tight contacts is that the planned treatment may go off track. Or in the case of the last aligner, you may still need some slight movement to get them into their final position.

Solutions

How to check if you have tight contacts

When flossing between teeth if the floss has a hard time popping in and out then you know that you have a tight contact. (If the floss pops in and out easily then this is light to moderate contact.) 

What to do with tight contacts

When you have tight contacts, you do not necessarily need to request a case revision, which could be lengthy and delay treatment. Try the following actions:

  • Floss between the suspect teeth (areas of misalignment) to check for tight contacts as described above.
  • If tight contact exists, you can do some  hand stripping to create approximately 0.1mm of IPR. 
  • If there are no tight contacts (but there is some misalignment), you can still do a little IPR (0.1mm) to help create some needed space.
  • If you have tried the above, and feel you've created sufficient space, but still have misalignment, at this point you may need to submit a revision.

Note: IPR is done at your discretion. We advise doing hand stripping which creates 0.1mm of space. If you do 0.1mm of IPR at a time, any excess space created by additional hand stripping (not on treatment plan), will be fairly easy to close at the end of treatment with a revision by requesting a digital power chain.

Tech tip: Undesirable undercuts

Desirable vs. undesirable undercuts

Mosby's Dental Dictionary defines an undercut as "the portion of a tooth that lies between its height of contour and the gingiva, only if that portion is of less circumference than the height of contour." Aligners rely on these naturally-occuring desirable undercuts for normal retention.

Undesirable undercuts, however, are too retentive, making it difficult to remove impressions or aligners. Some common causes of undesirable undercuts include:

  • Gingival recession creating a notch at the cementoenamel junction
  • Under-restored dental implants and bridges
  • Anomalous tooth morphology
  • Overcontoured restorations

How to deal with undesirable undercuts

One of the most common techniques for dealing with undesirable undercuts is to block them out:

  • Before taking impressions, fill in the undesirable undercuts with a soft material that will not bond to the impression (like wax). This will make the impression easier to remove, and also eliminate those undercuts from the resulting 3D model, making the aligners easier to remove as well.

Another technique is to trim the medium body material:

  • Between the first and second steps of a two-step impression, use a knife to trim away the impression 2 millimeters above the gingival in the medium body material. This will ensure that the only material covering the undercuts is the flexible light body material, allowing the impression to be removed easily.

Note that if you use this technique (or if you take intraoral scans), the undesirable undercuts are still likely to show up in the 3D model and aligners. In these situations, you may want to ask ClearCorrect to block them out digitally:

  • When you submit the case, use the additional instructions section to describe any undercuts that you want ClearCorrect's technicians to digitally fill in. When you get the treatment setup, inspect these areas of the 3D model carefully to ensure that they meet your expectations.

We hope this information was helpful to you!

Until next time...

Tech tip: Fitting & tracking issues

How can I tell whether an aligner fits?

A properly fitting aligner should cover the teeth and fit snugly against the patient’s teeth. It will probably feel a little tight at first.

  • The aligner should usually cover the gingival by at least 0–2 millimeters. (Aligners may be trimmed differently to compensate for undercuts, black triangles, recession, bridges, etc.)
  • The incisal edges of the teeth should fit flush against the aligner without any gaps.
  • The aligner should fit snugly over the distal surfaces of the rearmost molars, if the aligner extends that far back.


Properly fitting aligners

Fitting issues

There are a few possible causes for fitting problems:

  • If the first step doesn't fit, the most likely cause is an inaccurate 3D model. This can be caused by distortions in the initial impressions or scans.
  • If the fit of the aligners gets worse over time, the teeth may not be "tracking"—in other words, the aligners are progressing as originally planned in the treatment setup, but the actual teeth aren't keeping up due to lack of space or insufficient pressure.
  • In rare circumstances, an aligner may be distorted due to physical damage or a manufacturing defect.

Some common types of fitting issues are shown below. Click a photo for detailed troubleshooting information.

Incisal gaps 


Aligners that are too big or too small


Aligners that fit on only one side

Tracking issues

Even if the aligners do appear to fit comfortably, that doesn't guarantee that the teeth are actually moving as intended. Here are some tips for identifying unseen tracking issues before the treatment goes too far off the rails:

  • Any patient non-compliance can lead to tracking issues. Educate your patient on the importance of wearing their aligners at least 22 hours per day. Signs of non-compliance include missed appointments, unusually clean aligners, and a persistent tight fit after weeks of wear. Make sure your patients know they should contact you immediately if their aligners no longer fit.
  • Saliva buildup or saliva bubbles inside the aligner often indicates that there is a significant gap between the aligner and the teeth. This will most likely be seen at the trim line.
  • Blanching of tissues indicates soft tissue impingement. This could be the result of inaccurate capture of these areas in the impression or the result of a frenum that extends towards the gingival margins.
  • If the aligners are slightly ill-fitting when you give them to your patient, but the patient calls back a few days later saying that they now fit, don't rely on that self-assessment. Do a follow-up visit to confirm the quality of the fit before advancing to the next step.
  • Even if the aligners are fitting during check-up appointments, you should check the treatment setup and paperwork to see which teeth are moving and if those teeth appear to be on course. If you see that a tooth is not moving as planned, don't wait, take immediate action. If you continue with treatment in hopes that it will correct itself later on, it may get worse.

We hope you found this information helpful!

Looking for something?

We have a great online store filled with useful tools to help you in treating your patients with clear aligners. Everything from IPR Kits and Chewies to Webinars. Check out our store at store.clearcorrect.com.

Until next time…

Tech Tip: Video - How to Take Photos & X-rays

We've created a video giving some helpful tips on how to take good photos of patients' teeth before submitting a case to ClearCorrect. Check it out!

We hope you found this video helpful! Feel free to check out our Help Center which is filled with useful tips, tricks and information to help you in treating your patients with ClearCorrect.

Until next time...

Tech Tip: Support Tips

We know that occasionally you can run into issues during treatment (aligner errors, a rotation not occurring as planned, fitting issues, occlusal gaps, etc.)

Our support representatives are here to assist you with any trouble you run into. We thought we would offer up some tips to assist you in getting your issue resolved as quickly and efficiently as possible.

Take a picture

We believe that sometimes a picture is worth a thousand words. Taking a picture of the problem you're having and sending it to one of our experienced support representatives can speed up the process and makes a huge difference in being able to resolve issues with certainty.

We'll need a close up clear picture of the occlusal, right and left lateral views of the arch in question both with and without the aligners.

So, if you can, take a picture of the problem you're having and send it to support@clearcorrect.com.

Give support all the information

When getting assistance from a support rep, they need to know as much information about the issue you're having as possible in order to better assist you. When you send in a support request be sure to give the following information:

  • Verify the step and case # marked on the aligner that the patient is trying on.
  • Confirming when and what step the issue started.
  • Was there any troubleshooting already done to correct the issue?
  • If yes, what troubleshooting techniques did you already try?
  • Is the patient compliant?

Fitting issues

Before you call support about any fitting issues, you may want to review the options you have available to you first:

  • Checking and breaking tight contacts in the area where the fitting issue is present.
  • If there are difficult movements present in the area with the fitting issue you can try backtracking with a fresh aligner, dimples, auxillaries, and chewies to get it back on track.
  • Reiterating patient compliance.

We hope you found this information useful!

Until next time...  

2015: Year in Review

Happy New Year!

2015 was a fantastic year and we've got an even better year planned for 2016 (our tenth anniversary). In case you missed them, here are a few of the highlights of 2015.

    

  • We went international! ClearCorrect is now available in Canada, Australia, and New Zealand, with more countries coming soon.

    

  • We created our new and improved Help Center, including live chat with support representatives directly from ClearComm.

  • We introduced several new features, including:
    • You're not obligated to pay until you approve a treatment setup
    • You can ask us to recommend a case type
    • We're shipping up to 12 steps at a time
    • You can customize your wear schedule
    • We added a number of new features for retainers, including making multiple sets of retainers available for purchase
    • Discounts are available for case submissions using intraoral scans
    • Volume discounts start at just 5 cases per quarter
    • Limited revisions are a flat rate of $120 plus shipping, instead of $240 per phase
    • We started offering daily, weekly, or instant email notifications, so you can keep up with your cases however works best for your office.

  

Hope your 2016 is off to a great start! Until next time...

Tech Tip: Setups based on old impressions or scans

When you evaluate a treatment setup, you have four options:

  1. Approve the setup and start the case
  2. Decline the setup and ask for changes
  3. Decline the setup and submit new impressions or scans
  4. Decline the setup and cancel the case

If it's been a while since you took the impressions or scans, you’ll need to evaluate whether they’re still accurate. Only approve a setup if you’re confident it accurately represents the current position of the patient’s teeth. Otherwise, you’re likely to have fitting problems, starting with step 1.

Here's what our Chief Technology Officer, Dr. James Mah, has to say on the subject:

Dr. James MahIt is best practice to promptly revise and approve the setup as the patient's dentition may change over time. The amount of change and the time frame depends on the individual patient. The dentition is not immune to the effects of wear and aging and is more dynamic than most people appreciate.

Practically, patients may be classified in the stable group where any changes are undetectable or subtle enough that there is no effective difference over many months. These dentitions typically have all teeth present in an adult, healthy periodontium, no habits, neuromuscular problems or parafunction and no unusual amounts of dental wear/attrition. A good rule of thumb for these patients is to take new impressions/scans after three months have elapsed to avoid the possibility that changes have occurred.

On the other hand, patients may have unstable dentitions where the teeth may change sufficiently to impair fit of the aligner. A common situation is following extraction of a tooth. Adjacent teeth often shift and the opposing tooth may super-erupt. For this reason, extraction treatments with aligners almost always have the extractions performed only after the aligners are available. In situations involving extractions, there is great variation and in some patients changes over a short period of time such as 2 weeks is enough to cause the aligners to not fit.

Another group that experiences tooth shifting are patients with ongoing periodontal disease. Active periodontal disease is often associated with unintended tooth movement. It is best to manage the periodontal disease and re-evaluate to determine whether orthodontic treatment is even a possibility.

Patients that clench and grind or other situations where there may be loss of tooth structure such as bulimia may also end up with poor fitting aligners depending on the severity of the problem and the amount of resultant enamel and dentin loss.

Unfortunately, in these situations of instability, there are no general rules to follow as each patient is different with different etiologies and severity. Certainly, much is up to the discretion of the doctor but change of some degree is anticipated. For this reason, these treatments have additional complexity and the patient should be informed of the issue. If treatment is elected, the best practice of promptly revising and approving the setup is recommended, rather than allowing the teeth to potentially shift for months before approving.

We hope you found this information helpful.

Until next time...

Tech Tip: Popping TMJ

What should I do if my patient’s TMJ pops when she uses Chewies?

It's possible that the Chewies could be creating a fulcrum point in the patient's occlusal plane, resulting in joint stress and positional changes.

A conservative joint management approach is recommended:

  1. Discontinue Chewies and ask the patient to help seat the trays by pushing up/down with fingers instead.
  2. Ensure the clinical TMJ exam is complete including joint films (CBCT) and a radiologist report. (You need to rule out degenerative joint disease and pathology.)
  3. Continue to clinically monitor the patient's TMJ signs and symptoms at every visit. If pain or limitation of jaw movement is noted, consider pausing treatment and remaining in the previous step until symptoms resolve with conservative therapy (Motrin, no gum chewing, soft diet, limit wide openings, etc.).
  4. Consider a one-year TMJ radiographic examination—if there are no changes from baseline, consider a 3-5 year radiographic follow-up.

Hopefully the patient's joint popping or pain will diminish. If they do, continue on with the patient's aligner treatment. (Steps #2-4 above could also apply to aligner patients who suffer from TMD.)

Don't forget about our Help Center and support representatives—they're chock-full of useful information, and we love hearing from you.

Until next time…