July 05, 2021

Which is best? Open or closed exposure of palatally impacted canines?

This post is about a new trial that looked at the effects of open or closed exposure of impacted canines.  I thought that this was a well-done trial that adds to our knowledge of these two techniques.  It was fascinating because the authors looked at this from the point of view of the clinical and patient-reported outcomes. The results certainly translate into our clinical decisions.

The treatment of impacted canines is one of our most challenging treatments.  In my clinical experience, it was easy for this treatment to become one long pull on a canine that seemed to last forever.  There were also many ways of aligning the canines, and our first decision was always whether we went for an open or closed exposure.  This decision was always the surgeons.  For some reason, all the surgeons that I worked with preferred an open exposure and bonded chain.  This process seemed to work fine, but we did not have any trials that looked at which technique was best.

Since then, Nicola Parkin has done a Cochrane review. She concluded that in 2017 there was insufficient evidence to recommend either technique. She also pointed out that there were three RCTs underway at the time of publication of her review.  However, I could not find any other reference to these studies in the review.

I presume that this new paper was one of the studies. A team from Orebro, Sweden, did the trial. The EJO published the article.

Open vs closed surgical exposure of palatally displaced canines: a comparison of clinical and patient-reported outcomes—a multicentre, randomised controlled trial.

Margitha Björksved et al. EJO advanced access: DOI: 10.1093/ejo/cjab015

What did they ask?

They wanted to find out if closed or open exposure was better in terms of

  • Treatment duration
  • Patient perception of pain and discomfort
  • Dental fear
  • Treatment complications.
What did they do?

They did a parallel-sided RCT with a 1:1 allocation of the two interventions.  The PICO was

Participants:  Orthodontic patients with uni or bilateral palatally displaced canines planned for surgical exposure and alignment who were not older than 16 years old.

Intervention:  Open exposure of the canine

Comparator:  Closed exposure of the canine.

Outcomes: The primary outcome was treatment duration. Secondary outcomes were patients perception of pain and discomfort,  dental fear that they measured with a dental fear questionnaire and treatment complications.

Treatment complications included root resorption measured from CBCT images.

They enrolled the participants from January 2014 and February 2017.

They gave the patients and parents information about the trial, and they had a week to decide whether they wanted to take part.  The authors used pre-prepared randomisation stratified for the centre. They did an intention to treat analysis.  Their sample size calculation was precise.

What did they find?

One hundred seventeen participants completed the trial.  58 were in the open, and 59 were in the closed exposure group.

They found the following:

  • The eruption time, measured in months from the exposure until the canine crown was visible, was 8.5 months (SD=5.7) in the open group and 11.5 months (SD=5.7) in the closed group. This was statistically different.
  • They looked at the treatment time from the canine being visible to being in position in the arch with good root torque. They found that this was 18.0 months (SD=6.1) in the open  and 14.8 months (SD=6.9) in the closed. (p=0.01).
  • This meant that the total treatment time was 26.4 months in the open and 26.3 in the closed group. This was not statistically or clinically significant.
  • They did not find any other differences for the other outcome measures, apart from pain and discomfort.  Their analysis showed that there was statistically more significant pain in the closed than in the open group.  Unfortunately, they did not mention if this difference was clinically significant.

Their overall conclusions were:

  • The treatments were equally successful. The clinicians aligned all the palatally impacted canines.
  • There were no differences in total treatment time
  • The closed group reported more pain and discomfort than the open exposure group.
What did I think?

I thought that this was a well done and reported trial. The authors included a large amount of information in the results.  I suggest that everyone interested in this subject tries to get hold of a copy of the paper.

The study had a great degree of generalisability as they did it in three centres. It was also great to see outcomes that were associated with our patient’s values.  I do not doubt that treatment duration, pain, and harm are more important than ceph and occlusal index measures to our patients.

We need to consider if this paper will influence clinical practice. Firstly, there is no problem with there being no difference in treatment times.  This means that the type of exposure may still rest with the surgeon and their preferred technique based on their clinical experience.

However, when we look at pain, it appears that open is best.  Unfortunately, I was not too clear on whether the difference was clinically significant.  Nevertheless, we can use this information to provide our patients with the necessary information for consent.

Finally, I thought it was great to see a trial done so well and written up so clearly.

Related Posts

Have your say!

  1. Dear Kevin,
    I did not have the chance to read the paper yet, but the first thought that comes to my mind are the periodontal consequences of these treatment options. In bucally impacted canines we will in general have concerns regarding the esthetic final outcome of treatment. But, in palatally impacted canines, they are usually brought to place through a generous amount of gingival tissue. I would love to know the differences between the groups in this aspect as well. Just a suggestion that I believe the authors do have the data. Thank you for sharing this paper and congratulations to the authors.

  2. Hi Kevin,
    Thank you for another excellent blog and for highlighting a very useful study. I am a fan of the open exposure technique and leave these teeth to erupt spontaneously for 1 year before starting active Orthodontic treatment. I was therefore intersted in the detail of this paper and whilst I acknowledge the open technique will take longer overall, the active Orthodontic phase is shorter.

    I am not usually a pedant but just in case anyone else is looking at the detail in the paper, the treatment time was 8.0 months (SD 6.1) in the open group and 14.8 months (SD 6.9) in the closed group (P = 0.010). I hope you don’t mind me noting this here, just on case anyone else looks at the detail.

    An interesting study and one that will be quoted in exams from now on.

  3. Hi Kevin,

    I just noted that there was a mislabeling of the data in your summary about the T3-T2 time differences. Just confirmed that the overall treatment time that you reported is correct based on the actual online early paper version.

    “They found that this was 18.0 months (SD=6.1) in the closed and 14.8 months (SD=1.9) in the open. (p=0.01).” should be “They found that this was 18.0 months (SD=6.1) in the open and 14.8 months (SD=1.9) in the closed. (p=0.01).”

    In regards to pain/discomfort, the differences seem to be in the 6 to 8% range with quite a difference in the reported ranges (0-28%). So it could be constructed to the patient/family that there is less likelihood of pain/discomfort with the open approach but the expected pain/discomfort levels will be relatively low nevertheless or something around this. Pain/discomfort is a multifaceted construct that is difficult to generalize due to individual pain thresholds too.


  4. unfortunately the i cannot read the original paper, IMHO if tooth was buccal or palatal has a significant influence on the decision
    Palatal I always opt for open (the tooth is erupting though keratinised mucosa which forms a good gingival margin) AND you are at the mercy where the surgeon sticks the chain, which in my experience is palatal and not buccal, meaning you get rotations that need corrected, adding to length of treatment
    Buccal i opt for closed and gold chain to bring the though through keratinised mucosa, and teach them to use Transbond MIP to increase bond strength/reduce failure in a moisture rich environment

    We published this quite some time ago…

    Posttreatment assessment of surgically exposed and orthodontically aligned impacted maxillary canines
    G S Blair 1, R S Hobson, T G Leggat
    Am J Orthod Dentofacial Orthop
    . 1998 Mar;113(3):329-32

    The effect of moisture and blood contamination on bond strength of a new orthodontic bonding material
    R S Hobson 1, J Ledvinka, J G Meechan
    Am J Orthod Dentofacial Orthop
    . 2001 Jul;120(1):54-7

  5. Is it possible there is a typo? When I add up the numbers for the closed versus open, I get 23.3 for the open and 29.5 for the closed.

    While I personally have never made a mistake, I understand they are quite common.

  6. Thank you Kevin for the kind words about our paper.


  7. Hi Kevin,
    Can you please clarify?
    Is something is reversed in the “What did the find section”?
    > Eruption time: Open 8.5 months, Closed 11.5 months
    >Treatment time: Closed 18.0 months, Open 14.8 months
    Total time: Open 26.4 months, Closed 26.3 months.
    It’s 6:30 am and I’m still on my first cup of coffee.

  8. From the reported results, it appears that the opened procedure took 23.8 months (8.5 months+14.8 months) and the closed procedure took 29.5 months (11.5 months+ 18 months). A difference of 5.7 months longer for the closed procedure.

    • Several people have spotted a typo in my first version of this post. I have now changed the text and I am sorry for the confusion.

  9. Several people have spotted a typo in my first version of this post. I have now changed the text and I am sorry for the confusion.

  10. Hi Kevin:

    Extending the concept of impacted teeth, I wonder if anyone has looked at third molars in this respect? The graphic you’ve used to illustrate impacted cuspids also reveals impacted third molars. While I understand the emphasis on the ‘social six’, we prefer a biomimetic approach in an attempt to accommodate 32 teeth encoded by the human genome.

  11. A very interesting paper. I found that the bonded gold chain often detached at just the wrong time with a minimally exposed canine! Very frustrating!

  12. Hi there!
    Thank you for the interest in our paper! Just want to clarify that the VAS score differences of higher pain and discomfort values (and analgesic consumption) in the closed group were statistically significant during all time periods (before eruption, after and totally, see table 2.
    Best wishes!

  13. I am a fan of the open technique, especially in cases where the canine is tucked well in behind the lateral. In these cases, the mechanics regarding direction of pull is more complicated since one can not pull directly to the buccal arch wire. This takes more chair time and I would think is part of the increased discomfort. In all cases, (in my opinion) the open technique reduces uncertainty on multiple levels and increases control of the treating orthodontist regarding things like bond failures of attachments, potential ankylosis etc. A tooth I can see is always easier than a tooth I can’t see.
    I would also be interesting to know if there were any teeth that failed to erupt and in which group they were in. Also, It would be interesting to know how much chair time was involved between exposure and when the tooth was in the arch able to take a standard bracket and arch wire. This would speak to the uncertainty/complexity issues that might be different between techniques.

    Finally, Kudos to the authors for undertaking such an arduous and clinically relevant study. Impacted canines are always long(er) and more labor intensive cases and I am ready to be rid of them by the time I am finished. The thought of tracking and managing data on dozens of these cases over many years makes me shudder and want to drink to excess. Hats off to them.

    • Dear Dr.McDonald,
      Thank you for the encouraging words! I’m sorry for the late response. In this trial, also reported in the article, all canines were successfully aligned. We experienced two re-exposures in the open group and none in the closed group, neither did we have any attachment failures. I’m glad to please anyone who wonders about chair time etc, that there is a cost-minimization study included in the series of studies on this RCT, which will soon be published.

  14. As in Ross Hobson’s comments I have also moved to open for palatal over the years. Both obviously work but there seem to be more complications with closed. It would be interesting to know if they had any in the trial patients. These are usually, chain glued on palate so tooth rotates and, having to expose again in an open manner since the tooth can’t force through the palatal mucosa. Also it depends on, not only where the chain is glued but also where it exits, directly above the crown is probably best but often it is exited through the gingival sulcus or crestal ridge incision making vertical eruption tricky. Closed seems to offer no benefits really for palatal canines.

  15. Its a nice rct, there is two points not mentioned as i thought first one is the accumulation of plaques or food which is related to o.h.
    Second one no any information about result og the gingiva at the end of treatment

    • Dear nabard,
      Information of the gingival and periodontal health (gingivitis, probing depth, gingival recession, alveolar bone height) before and after interventions, are included in the article.

  16. Great study, nice to see another RCT on this subject, the last one was carried out 10 years ago by our Sheffield/ Derbyshire group a decade ago. The findings were similar both for duration and patient response. We used periodontal health as our primary outcome but duration would have been better – this is most important to our patients.
    I agree with Grant Macintyre, leaving plenty of time for canines exposed with an open procedure to erupt autonomously. For medially placed canines (sector 3 plus) I use an open exposure and then leave until the canine is fully erupted in the palate (this often takes 9 -12 months) and then bond the braces. You can then see what you are doing, the direction you are pulling. This study (and ours) made an error in not waiting long enough before placing the fixed braces. It is too early to bond an attachment and apply traction ‘when enough canine tip is visible’.
    Schmidt & Kokich discussed this in their 2007 article. I suspect if the authors of this trial had used the same methodology as S & K then the total time to align the canine difference between the two groups would be both statistically and clinically relevant.
    T1, the eruption time should have been zero in the open group as braces do not need to be placed until 1/3 to 1/2 of the canine crown is visible. Time from T2 to T3 might be longer in the open group as space may need to be created and the canine will need to be dragged over the mucosa and in to position.

    • Hi Nicola,
      thank you for your important and interesting series of previous papers in the same subject!
      We totally agree with the PDC management where the PDC is allowed to erupt spontaneously with an open exposure, with no rush for bonding attachments.
      We had no restrictions according to malocclusions in our trial, aiming to do clinical relevant treatments according to ”real life” clinical settings, why fixed appliance was inserted in some crowding cases (both open and closed exposures) to create space. If this had not been done, there could have been a risk of PDC ”over-eruption” before it was possible to pull the canine into its place in the dental arch. Our experience is that this could be an issue – especially in deep bite cases – where it may be some difficulties to pull a well-erupted PDC over the lower dental arch. Timing is one of the challenges in these cases. Depending on the case, the clinicians might want to start to pull the PDC as soon as possible or to wait. In the current trial we therefore bonded the PDC on the buccal aspect when it had erupted 1/3-1/2 of its crown to have a same time reference in both groups in regard to bonding the attachments.

      Best wishes,
      Margitha and Farhan

Leave a Reply

Your email address will not be published. Required fields are marked *