October 05, 2020

Removal of two primary teeth per side: A new direction for ectopic canines?

A wise man once told me ‘If in doubt, don’t extract’. I was therefore interested in reading this new clinical trial. This looked at whether we should remove two primary teeth (canine and first molar) to improve the eruption of ectopic palatally-displaced canines (PDCs).

We have seen a welcome improvement in our evidence base relating to interceptive management of ectopic canines in recent years. Much of this research has emerged from Scandinavia. This interesting paper builds on this work. A relatively recent trial using a contemporary methodology and three-dimensional imaging by Nauomova and colleagues has helped to re-affirm the earlier work of Ericsson and Kurol. This suggested that the removal of primary canines may improve the position of ectopic permanent canines.

Currently, clinicians propose a wide array of more invasive alternatives to improve the position (and indeed produce ‘independent’ eruption) of ectopic canines. These interventions include adjunctive use of transverse expansion, arch lengthening with cervical-pull headgears and re-opening of an excess of space with fixed appliance. In addition to the removal of first primary molars primary canines. They base these techniques on the potential benefit of space creation in encouraging favourable movement of the canine. By and large, these more invasive approaches have demonstrated equivocal benefit.

A team based in northern Norway did this study.  The Angle Orthodontist published the paper. I have yet to visit northern Norway; however, my children continue to suggest that we go there some time!

Double vs single primary tooth extraction in interceptive treatment of palatally displaced canines: A randomised controlled trial

Authors: Sigurd Hadler-Olsen; Anders Sjogren; Jeanett Steinnes; Mari Dubland; Napat Limchaichana Bolstad; Pertti Pirttiniemi; Heidi Kerosuo; Raija Lahdesmaki

Angle Orthod. 2020. doi: 10.2319/031920-196.1

What did they ask?

They asked this question;

“Is extracting the primary canine and first molar more beneficial than extracting the primary canines alone in improving the position and eruption rate of palatally-displaced canines (PDCs)”?

What did they do?

They did a two-group randomised controlled trial with a 1:1 allocation (32 participants overall with 48 PDCs) over a 24-month observation period as follows:

  • Aged 9.5 to 13.5 years
  • With one or two PDCs and presence of primary canines and first molars, and permanent lateral incisors
  • Displaced canines in sectors 2-4 based on an accepted classification (Lindauer et al., 1992)
  • With aligned, spaced and mildly crowded arches
Intervention Groups:

Double-extraction group (DEG): With the extraction of both the primary canine and the primary first molar

Single-extraction group (SEG): Involving extraction of the primary canine only.

Primary outcome(s):

The eruption of the canine; and eruption of canine into the correct position

Secondary outcomes:

Positional change of unerupted canine

A panoramic radiograph was available before the study, They took another radiograph every six months until the canine erupted into the mouth. Importantly, if the canine position worsened or did not improve improvement within 12 months, they provided alternative treatment  (surgical exposure and fixed orthodontic appliances).

What did they find?

The groups were relatively well-matched in terms of canine position at baseline. Notably, a significant proportion of the ectopic canines erupted over the 12 months. However, there was no difference between the groups with 16/25 (64%) in the DEG erupting while 18/23 (78%) canines erupted in the SEG (P= 0.283). In total, 64% of the canines emerged favourably in the DEG vs 57% in the SEG. Again, this difference was not significant (P= 0.600).

In terms of the secondary outcomes (positional change based on radiographic analysis), they did not find any significant difference between the two groups for changes in canine angle or sector. Unfortunately, six of the canines deteriorated in position. Four of these were in the DEG and two in the SEG. They also found that the start angulation of the canine and the space conditions at baseline were predictors of positive response to interceptive extractions.

What did I think?

Firstly, I think that this was an interesting study. I am not sure how common the recommendation of loss of two primary teeth per side is; however, this study suggests that this approach is unwise.

From a methodological perspective, the study is very well-executed. Recruitment took place over a prolonged period reflecting the narrow selection criteria. These strict criteria helped to limit the potential for confounding related to the stage of dental development, the position of the canine, and the potential absence of maxillary lateral incisors. Overall, therefore, the authors made a monumental effort and are to be congratulated for seeing this study through.

The percentage of teeth erupting over the observation period (which I believe was two years) was significant (71%). This is mainly in keeping with similar studies.


I note that other studies considered whether removal of the primary canine is of benefit and included an untreated control. These investigators could have included a third group. Nevertheless, because of the consistent findings from previous studies, this is probably unnecessary and would have made the research hard to complete.

A further limitation relates to the use of two-dimensional imaging. However, the authors do focus on the clinically-relevant finding of the eruption (or otherwise) of the canine. They, therefore, provide us with crucial information that is relevant to clinical practice.

What can we conclude?

There does not appear to be an added benefit in recommending extraction of the primary first molar (in addition to the primary canine) in improving the rate of eruption or the position of PDCs.



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Have your say!

  1. Extraction of the primary canine has proven to be useful in these kind of cases to me over and over again.
    Never thought of extracting the first primary molar as well. This may have a (slight) impact on chewing ability.
    Did the authors measure a possible arch shortening?

  2. Are we thinking critically enough about how this sort of treatment feels to our patients?

    I think it’s established that interventional treatment such as extraction of deciduous maxillary canines often improves the position of an unerupted displaced adult maxillary canine from the orthodontist’s point of view – but that is not the same as a guarantee that the canine in question will actually come through where it should – or come through at all.

    Before direct bonding, management of displaced unerupted maxillary canines was a challenge and so the balance of advantage would often be in favour of extraction of a deciduous canine to get some improvement, at least
    After the development of direct bonding, surgical exposure and bonding of canines transformed the situation (provided someone who knew how to bond teeth went to theatre to carry out the bonding!) – and the actual position of the unerupted canine was much less of a ‘make or break ‘ issue.

    I can remember having primary canines and if I can speak for myself and other small children, if I have to go through the extraction of a primary canine, I want the adult tooth to erupt pretty well on target, to make the fear and dismay I am going to go through worth it!
    If the adult canine position merely ‘improves’ from the dentist’s point of view, that’s not good enough from my point of view.

    When I was in practice, I preferred to delay treatment until the patient was older, more psychologically robust and could understand more exactly what the problem was and what needed to be done about it.

    And on another subject, Kevin wonders about taking a trip to Northern Norway. I my opinion, definitely go!

  3. Interesting findings. I look forward to reading the article. My decision to remove 2 teeth vs 1 tooth in this situation hinges more on the position of the premolars rather than any other factor. I find that when the heights of contour of the two premolars are side by side, there is less of a chance for canine eruption than if the premolar heights of contour are at different levels. Extraction of the molar in addition to the canine is to allow the first premolar to erupt thus giving the canine somewhere to go. While the canine does not always fully erupt, I feel that it assumes a more vertical position thus is less problematic to bring into the arch. It would be interesting to check the angulation/position of the canines that did not erupt and see if there is a difference there. I do not doubt the validity of the study, I am just not sure they chose the most clinically relevant selection criteria.

  4. Well Extraction of the primary 1 molar usually hazens the eruption of the 1 premolar rather than guiding the canine into place if done around the age of 9-10 yrs. Rather one could openup some extra space between C and D/4
    Also extracting the first primary molar would result in arch shortening higher risk of canine displacement.

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