Extracting primary canines intercepts permanent canine impaction!
The impaction of permanent canine teeth is a real problem. We frequently try to intercept this by extracting primary canines. But is this effective?
There have been surprisingly few trials that have looked at this treatment. In this blog I have previously discussed a Cochrane review that was published in 2012. These authors concluded that there was no evidence that the removal of the primary canines was effective. Then in 2015 Julia Naoumova published a really nice trial. She concluded that the removal of the primary canine was of benefit. As a result, I feel that there is still some confusion about this treatment. Therefore, I was interested to see two new systematic reviews into this problem. It is worth having a look at them.
Firstly, I will look at the one done by Naif Almasoud. The Angle Orthodontist published this paper. It is open access so you can have a look at it.
Naif N. Almasoud a
Angle Orthod. On line DOI: 10.2319/021417-105.1
He set out to discover if removing the primary canines intercepted the palatal impaction of permanent canines. He did a standard systematic review. The PICO was
Participants: Children with at least one palatally displaced permanent canine
Intervention: Removal of the primary canine
Control: Non extraction of the primary canine
Outcome: Eruption of the permanent canine.
What did he find?
He only included randomised trials and identified four studies. Two had been recently carried out. One was by Naoumova (2015) ( I have posted about this one) and the other was by Bazargani et al (2014). I must have missed this one! The other two studies were by Baccetti and Leonardi.
At this point, I would like to mention that the studies by Baccetti and Leonardi were reviewed in the Cochrane review. The authors of this review did not include the data from these studies because they were at high risk of bias and the interpretation of the data was not clear. Dr Almasoud also felt that these studies were at high risk of bias. As a result, I am not going to include this data in my interpretation.
I would now like to look at the other new review.
Ameirah Saeed Alyammahi et al
European Journal of Orthodontics, 2017, 1–8 DOI:10.1093/ejo/cjx042
The European Journal of Orthodontics published this paper. Unfortunately, it is behind a paywall, so unless you are a member of the EOS or have access through a library, you cannot read it…
A team from Dubai did this review. They set out to answer the same question and used the same PICO. They assessed bias using the Cochrane Risk of Bias tool.
What did they find?
This time they found five RCTs. These were the same studies that Dr Almasoud found, but they included another study by Baccetti. As with other reviews, they found high risk of bias in the studies by Baccetti and Leonardi. As a result, they analysed the studies with high and low risk of bias separately. In effect, the Naoumova and Bazargani were the only studies that provided good evidence.
What can I conclude?
I will only include the data from the recent high quality studies. I have put the relevant data into this table.
|Study||Eruption after extraction (%)||Eruption after non-extraction (%)||Risk Ratio (95% CI)|
The results clearly show that removing the primary canines increases the chance of eruption of palatally places permanent canines.
Interpretation of this type of data can be tricky. I have discussed this in a previous post. We can conclude the following:
- If we extract the primary canines when we see a palatally displaced canine there is a 25-30% increase in eruption of the permanent canine, when compared to no treatment.
- The risk ratio means that the patients who had primary canines removed had 1.6/1.7 times the chance that their permanent canines would erupt, when compared to no treatment.
What did I think?
I feel that we can conclude that there is clear evidence that the extraction of primary canines leads to an increase in the eruption of palatally displaced permanent canines. Nevertheless, we need to appreciate that success is not guaranteed. The data from these studies is very helpful to our patients when we explain the treatment to them.
Finally, I would like to make a comment on the reviews. In a previous post I concluded that we may have too many systematic reviews. I cannot help thinking that these reviews are a good example of this problem.
We now have a Cochrane review and two other reviews into the same clinical issue. I am not surprised that the recent reviews have come to the same conclusions. I am also sure that when the Cochrane review is updated, this will reinforce these findings. (It would be great to see this one updated soon…). This must represent a waste in research resource and perhaps we should stop duplicating reviews?
Emeritus Professor of Orthodontics, University of Manchester, UK.