November 07, 2022

Careful with that radiation, Eugene.

When should we expose our orthodontic patients to radiation? This post is my personal view on this controversial area. You may or may not agree with me?

Long-term readers of this blog may be familiar with this title. I first posted about studies on CBCT in 2014 and used this title based on the Pink Floyd song. In these posts, I discussed studies that suggested we must be careful using CBCT imaging. I ignited this controversy again when I commented on the routine use of post-treatment CBCT in a recently reviewed paper. As a result, I felt I should discuss this subject in this new post. I know that my views will not be universally accepted!


An excellent place to start is to consider guidelines produced by experts in the field. One of the most extensive is the SEDENTEXCT project. This  European project aimed to develop evidence-based guidelines for using CBCT in dentistry. This was published in May 2012. These were also incorporated into the British Orthodontic Society radiographic guidelines. Unfortunately, I could not find guidelines from the American Association of Orthodontists. As a result, I will first highlight some of the main messages from the SEDENTEXCT and BOS guidelines.

Main messages
  • No exposure to X-ray radiation is completely clear of risk. All ionising radiation has the potential to cause harm.
  • Orthodontic radiographs irradiate children, so the need for judicious use is paramount.
  • Rarely a portion of a chromosome may be damaged and mutated. This may lead to a tumour. There is no threshold below which these effects will not occur.
  • These are stochastic events where the magnitude of the risk, though not the severity of the effect, is proportional to the radiation dose. This makes the distinction between safe and dangerous exposure to radiation impossible.
  • As a result, the justification for radiation exposure is that we do more good than harm. Therefore, radiation doses should be kept low, and all exposures should be minimised and in the patients, best interest.
  • CBCT is not recommended as a standard method of diagnosis and treatment planning in orthodontics.
  • There is no justification for taking radiographs before a clinical examination.
  • It is unethical to take radiographs for medico-legal, administrative or “just in case” if there is no clinical need.
So, what do we do now?


Firstly, we need to consider that, as these are guidelines, following them is not mandatory. Nevertheless, guidelines should be carefully considered. Importantly, we must have good reasons if our practice does not comply with guidelines.

I approached this discussion from the viewpoint of what I would like for me, my family, my children, and my children’s children. The bottom line is that no radiation exposure is entirely free of risk. I then considered the probability of harm, and the answer is that we do not know. As a result, I agree with the recommendations.

Finally, before I became an orthodontist, I was in a dental radiography post. The head of our department often stated, “Never take a radiograph if it is not going to change your clinical decision.” This simple statement provides a great simple message about dental radiographs.

Clinical implications

We now need to think about how this influences our clinical practice.

Firstly, we should only take pre-treatment radiographs if they will be helpful and the benefits to our patients outweigh the risks. Will the information change our clinical decision?

Secondly, it is tough to propose one good reason for taking post-treatment radiographs. This is because post-treatment radiographs are of no benefit to our patients.


I know that many practitioners will disagree with these conclusions. However, I am not sure of the reasons for this disagreement. I often see arguments that the radiation dose is the same as a plane trip. However, the plane journey is a choice and provides a means of getting somewhere or going on a vacation.

Other points put forward are that CBCT views are low dose and perhaps comparable to a cephalogram and panoral view. However, they are not “no dose,” and we must remember this simple fact.

Another argument is that we need radiographs to provide information that may be useful in unplanned retrospective future research. This is simply nonsense. We should only take additional radiographs as part of a planned prospective investigation when we can consent the patient to have the investigation.

I think that have written enough to have a really good discussion in the comments section of this post.

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Have your say!

  1. The American Association of Orthodontists is a member of the Image Gently Alliance. Very many of the recommendations and conclusions that you present are similar to the recommendations of the Image Gently Alliance.

  2. I totally agree with the entire post Prof O’Brien. As low as reasonably possible is a good motto when exposing anyone to ionising medical radiation.

    But on the other extreme, no Orthodontic treatment of any kind must be initiated without a basic pan oral radiographic examination (subsequent to a full clinical Orthodontic assessment of treatment need). Not taking radiographs in the name of reducing radiation is also something that needs to stop completely.

  3. Kevin
    I almost always agree with what you have to say on various topics but I need to disagree, to a certain degree, with what you had to say about post treatment radiographs. In this blog you stated:
    “Secondly, it is tough to propose one good reason for taking post-treatment radiographs.
    This is because post-treatment radiographs are of no benefit to our patients.”
    A little over 20 years ago I developed “Guidelines” for taking and keeping orthodontic records. I did it, because as you rightfully noted, across the pond here in the USA we didn’t have any. There was one series for academia, where clinical research was being done, and one for clinicians in private practice. The guidelines were identical except for the storage characteristics. Below are the guidelines for post treatment panoramic and cephalometric radiographs. They provide what I, and others, have considered as valid reasons for acquiring this data. Obviously many will disagree BUT for those who need a viable rationale for obtaining these records, here it is.
    Please keep up the good, no great, work you are doing. Orthodontics needs it.

    Lateral Cephalometric Film (post treatment):

    Guideline: A lateral cephalometric x-ray shall be obtained upon the completion of orthodontic treatment for all patients who had an initial lateral cephalometric radiograph taken.

    Rationale: Part of an orthodontic diagnosis and treatment plan is to establish specific treatment goals regarding the positioning and relationship of the teeth and/or jaws to one another and their respective supporting structures. A generally accepted method for quantitative verification of these treatment goals is through the comparison of the patient’s pre and post treatment cephalometric x-rays. Without being able to quantify the treatment results of the orthodontic, orthognathic, and/or orthopedic mechanotherapeutic approach(s) that were employed, the best interests of the patient are not served in that any evaluation of the efficacy of the treatment rendered cannot be reliably assessed. The patient’s right to be informed of their oral health status, as well being able to confirm any expectations associated with having undergone orthodontics and/or dentofacial orthopedic therapy, requires the practitioner to conform with this ethical and clinical imperative. Should a clinically significant degree of compromise or limitation relative to any difference between the treatment goals and the treatment results be discovered, the patient, except in rare instances, should be made aware of this discrepancy. This allows the patient to either accept the degree of correction achieved or chose to pursue additional therapy. In addition, the retention modality chosen, given the final orthodontic result, may vary depending upon how closely the treatment results came to fulfilling the orthodontic treatment goals for any given patient.

    Panoramic Film (post treatment):
    Guideline: A panoramic x-ray shall be taken for every patient at the completion of treatment. If other dental x-ray studies are contemplated or exist, and they are or will be of sufficient diagnostic quality, for maintenance and use by the orthodontic practitioner, the post treatment panoramic film need not be obtained.

    Rationale: A post treatment panoramic radiograph is an important tool for appropriately evaluating a patient’s dental health status. Orthodontic therapy poses unique risks associated with treatment, some of which can only be verified through radiographic studies. The patient’s legal and ethical right to be informed of their oral health status requires that should a degree of compromise, limitation, or negative sequelae be discovered, as a result of having undergone orthodontic treatment, the patient must be made aware of any such consequences. This will allow for the appropriate and timely integration of any necessary interdisciplinary adjunctive treatment that will inure to the benefit of the patient.

    • I follow Larry’s writings and have learnt a lot from them, they are always food for thought. I believe there are legal obligations in some USA states for post-treatment radiographs, if that is the law then acting ethically means acting within the law. I live in Australia not the USA, there is no legal requirement for post-treatment radiographs.
      I believe progress radiographs with appliances still in place are more likely to be used constructively. A post-treatment radiograph where the torque or root angulations are unexpectedly poor involves the discussion of …. we will need to place appliances on again … which will often be rejected by the patient and poorer treatment can be the result. Progress radiographs allow explaining to a patient the improvements possible from extending treatment and is accepted far more often.
      3D radiography is limited to instances such as poorly positioned, unerupted teeth and if their position can be determined by palpation or with the 2D radiographs then the 3D imaging is delayed until prior to surgery. There can be many reasons for 3D imaging but limiting the field of view and minimising exposure to Thyroid, salivary glands and eyes is essential. Radiography on young patients has far greater potential for injury, 3D imaging for pre-teen patients needs to be greatly restricted.
      I have seen ‘low dose’ CBCTs, I found their image quality sub-standard, much higher doses were required for proper visualisation. The photons required to image a page of a book and the photons required for a book are not going to be the same, physics can be like that.
      If there is an issue identified in the progress radiographs this may lead indicate the need for post-treatment radiography, otherwise post-treatment radiographs are requested for dental reasons alone.

  4. Having done IRMER and a CBCT course in the last 18m I totally agree with your view. I have seen enough unexpected short roots to be sure that we need to have some sort of pre-treatment radiographic evaluation, an OPT usually works well here. CBCT has been a useful adjust in ectopic teeth but it is not routinely needed, especially in children. I rarely take Cephs any more (though in a private practice I see less severe skeletal issues)

    I also struggle to see why end of treatment radiographs are needed. The previously stated purpose of seeing root parallelism is rubbish as I care about the clinical appearance and not the roots. I suppose you could argue we don’t know the incidence of our root ‘s resorption, but would it really change anything? If it’s for ‘dental health’ reasons as per Laurance’s post above then surely bitewings would be sufficient and the GDP should be doing these as it would be them who would act on it?

  5. I agree with you Kevin. On the various Radiography courses I attended during my Practicing career, the acronym “ALARA” (As Little As Reasonably Allowable”) was used, as close as you can get to ALARM! CBCT was after my time but I never took post treatment OPT’s and Cephs routinely as it simply wasn’t justified. Radiographs, being 2 dimensional representations of a 3D object….No benefit to the patient and little if any benefit to the orthodontist at the end of treatment.

  6. Ugh, I agree with all yet you say about post-debond CBCTs, though still feel some obligation to at least partially play the part of the opposite side in this debate.

    First, let me start with where I agree. In the vast majority of cases, it seems hard to find justification for CBCT as a routine procedure post-debonding. Yes, there may be the occasional need to take a post-treatment CBCT, perhaps to ascertain the prognosis for a compromised resorbed root or to help in ideal implant placement. Though that seems more the rare except rather than the rule.

    More, I believe that perhaps the biggest difference is in the routine use of post-treatment cephalometric radiographs. With these, I will first agree that the vast majority of the time these are of no to little clinical benefit to the patient on which they are taken. However, do believe that there is still sufficient justification for post-treatment cephalometric radiographs to be taken.

    This is because post-treatment cephalometric radiographs can most strongly benefit the subsequent patients that an individual practitioner will treat. The logical extension of that point is, IMO, not taking routine post-treatment cephalometric radiographs can actively harm the subsequent patients that a particular practitioner treats.

    Said otherwise, the benefit that we as practitioners personally gain from looking at our post-treatment cephalometric radiographs helps our future patients so much, that it is worth taking these on patients to whom they are of little or no benefit. Our future patients can be hurt so badly by our not knowing the true results of our treatment, that this utilitarian perspective is justified.

    A cephalometric radiograph can sometimes quickly display the mistakes that we made on a case. As the negative effects of less-than-ideal or even iatrogenic orthodontic care may sometimes not present themselves for a decade or more, this instant knowledge can be invaluable. For example, in a class II case, it is too easy for us to flare the lower incisors and cause dehiscence, fenestrations, or even place the roots completely outside of the bony base without knowing. The negative consequences of this may not fully express themselves for decades. With a post-treatment cephalometric radiograph, seeing the results of our having pushed the biological limit too far helps us to avoid the same mistake in future patients.

    This is not a theoretical argument. In this age where some corporations and KOLs are still pushing non-extraction at all costs, with their magic braces and magic appliances, this direct knowledge of what is and is not being done can be invaluable. One example is the current push by corporations and KOLs for the latest generation of clear aligners combined with mandibular advancement. One corporate claim is that these appliances control facial tipping of the mandibular incisors. However, how will we know if the cost of that is or is not translation of the mandibular incisor roots outside of the bony base if post-treatment cephalometric radiographs are not taken? Maybe this latest iteration of an old idea will be superior. However, maybe the claimed advantages will actually be harmful to patients. Without post-treatment cephalometric radiographs, we just will never know.

    A sports analogy may be a helpful example. Imagine a “striker” or “attacker” on a soccer (US) or football (the rest of the world) team who never gets to see the results of their kick on goal. Immediately after every shot on goal they are instantly blinded and made deaf. Worse, they are not allowed to see, hear, or know the results of any shot on goal until years or decades later. What effect would that have on that particular player’s technique or accuracy?

    While this is an extreme example, I believe that it is valid. I can personally attest that I have changed my treatment techniques and philosophies more than once during my career, as a result of looking closely at my post-treatment records which include a cephalometric radiograph. I am not happy about the treatments I believe that I could have done better. I am very happy that I have changed my technique and philosophy so that I make these mistakes less often.

    Thanks for posting. I believe that this is a great topic to consider.

  7. Sir,

    If I worked in a practice where I was asked to take post treatment radiographs routinely for Orthodontics or if I saw that being a regular practice, I would just quit working there. If the patient is not uppermost in our considerations then please can we just work in areas where one only has to deal with ‘clients’ and not ‘patients’.

    Some post treatment radiographs may be necessary, for example, to determine the location of the roots prior to implant placement etc. but routine post treatment radiographs for Orthodontics for the sake of medicolegal defence in future will itself lead to medicolegal proceedings against the practitioner in the UK in my view.

    I am happy to be corrected if I am wrong.

    Thank you.


  8. Just yesterday I was justifying to two Canadian orthodontist friends why I should continue to take post-treatment pans. After reading the above USA comments, I now understand why my two friends had that look like: Are you really buying into your own BS? Now I think I will stop irradiating my patients at no benefit to them. Even if it opens me up to some small legal liability. I’m setting the controls for the heart of the sun.

  9. I have come to the conclusion that the vast majority of lateral ceph X-rays are totally pointless as I don’t recall ever changing my treatment plan due to a number on a tracing. I do use CBCT but only for ectopic teeth (mostly canines), but do not see their routine use as seems to be becoming common as acceptable.

  10. I think this is a philosophical discussion relating to medicine. The maths and science have no answers.

    Only the logic of value judgement can help us.

    This is why the answer varies according to one’s value judgements.

    One must consider what is important to each individual case. A generalisation will not provide a universal answer. A guideline may help us wirh our logical thought.

    The question actually asks, …

    “What is the proper radiation cost one should expend to to satisfy a particular individual wish or need”?

    This is actually an economic cost-benefit question.

    It’s not different to asking
    “What is the proper price to pay, well, for anything”?

    The principle is always the same.
    As Low As Reasonably Achievable?
    What I would like to pay for my house, car, bicycle, and of course, orthodontic treatment?
    Does the ALARA answer what is the right price for what l want?

    Does knowing that low price *may* be better, help?
    Can we afford a low price if it risk giving us a wrong outcome? Too low a price carries risk.

    What is that amount?d ALARA?

    How does stating this obvious principle really help informed decision making on the value of dispensing any kind of therapeutic agent?
    All therapies have costs and undesirable side effects.

    Could no radiation be the best choice?
    Depending on the situation, YES

    Could pre treatment CBCT at the start of braces be the best choice? Depending on the situation, YES. It may help us to get roots inside alveoli bone.

    The answer will turn on what is important to each situation. It will be different, case by case.

    Several good arguments have been put forward to use radiography for a couple of different situations.

    But the situations vary much more than this.

    I think certain stakeholders may benefit as follows.

    Pre-Treatment x-ray of any type…

    1. Patient gets a better diagnosis
    2. Patient gets a more accurate, safer treatment plan, better planned tooth movements.

    Post treatment x-ray of any type…

    1. Patient gets a more purposeful, safer, post-treatment plan. After all, life goes on!
    2. Community gets a better understanding of tx efficacy from collective practitioner experience.

    Is there is a “Lack of Evidence” to say that benefit flows from various dental radiographies? Yes.

    If the studies on the definitive value of radiology techniques haven’t been done to answer our clinical questions, then we still need to use one of the lowest ranking justifications for what we do, which is our experience and our clinical judgement.

    We will need to rely on this until the available scientific data actually matches our clinical questions.

  11. Thank you for sharing your valuable feedback.
    Something that intrigues me, and I would like to read your opinion, is how much imaging changes the treatment decision.
    Assuming there is an effect, we should assume that there has been a considerable change from when there was less access to panoramic and tele to now that we even have CBCT and MRI.
    Secondly, it is now common for many orthodontists to purchase this expensive equipment. Are there any studies that show the ordering rate of exams among clinicians who own equipment vs those who don’t and must order externally?
    Finally, what is the utility of exams with more exposure? For example, I have now seen that 3D cephalometry has become popular. Still, I am unsure what evidence supports this migration from 2D to 3D cephalometry.
    Thank you for your time in sharing your thoughts.

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