Interceptive removal of primary canines to address incisal irregularity: A nail in the coffin?
This post is about the early removal of primary canines to attempt to resolve dental crowding. We report on the results of a very ambitious long term RCT into this common clinical decision.
International practice concerning the timing of orthodontic treatment is very variable. However, most of us feel that correction of crowding is best performed in the late mixed or early permanent dentition. Nevertheless, crowding can become apparent earlier. As a result, we recommend the removal of primary canines as a means of reducing irregularity in the incisor region. Unfortunately, this intervention may merely re-locate the crowding (more posteriorly) and might also lead to an unwanted marginal increase in the extent of crowding.
This leads us to several clinical questions.
“Does the removal of primary canines help to improve the appearance of crowded incisors”?
“Does interceptive removal of primary canines have long-term benefits”?
We considered a systematic review on this topic last year. The authors highlighted a limited benefit and made the customary plea for ‘further high-quality studies with long-term follow-up’. This clinical trial may help in answering this call to action.
A team from the Karolinska Institute in Stockholm did this study. I was fortunate enough to spend two months there as a bright-eyed dental student and highly recommend a visit.
Authors: Mhanna A. Aljabab; Muteb Algharbi; Jan Huggare; Farhan Bazargani
Angle Orthodontist. doi: 10.2319/020621-109.1
What did they do?
They carried out a follow-up of a previous clinical trial involving random allocation of participants in the early mixed dentition (mean age approx. 8.5 years) to the removal of the lower primary canines or observation only. All children had a pre-treatment lower inter-canine width of 26mm or less, lower incisor crowding of more than 3mm (approx.) and upper incisor crowding of 4mm or more. The follow-up study involved two parallel groups with a 1:1 allocation as follows:
- Late mixed or early permanent dentition
- Previous inclusion in the initial study
Intervention: Removal of all primary canines
Control: Observation only
- Orthodontic treatment need, complexity and outcome: Using the Index of Complexity, Outcome and Need (ICON);
- Treatment duration and number of visits: Based on a review of clinical notes;
- Permanent tooth extraction: Based on notes with one or more extraction recorded as permanent tooth extraction
The investigators based their analyses on patient models and clinical records.
What did they find?
They were able to include forty-six of the original 71 patients in the study. There were 23 per group and, of these, 36 had orthodontics while ten did not. There was no significant between-groups difference concerning either treatment need or potential treatment complexity based on the ICON scores.
For those subjects who did have comprehensive orthodontic treatment, the authors did not find a difference in treatment time (20.3 and 21.5 months in the control and extraction groups, respectively). In addition, they could not find a difference in the number of required visits. Six subjects in the control group had extractions, while ten who had had previous primary tooth extractions also underwent permanent tooth extraction. This difference was also not significant.
What did I think?
I liked this study. This research was challenging to do because it spanned a decade or more. We should congratulate the authors for their persistence in seeing this through to completion. The previous study did show little difference between the groups in the short term. It is therefore intuitive that they would not find important differences at this later time-point. Nevertheless, I do feel that this more prolonged follow-up is well worthwhile.
From a practical perspective, it is tough to avoid drop-out and loss of data given the longitudinal nature of the study here. However, this fact does mean that the study may be underpowered, with some possible associations not proving statistically significant. The slightly extraction higher extraction rate in those having interceptive extractions may typify this.
While the findings here point to a lack of effectiveness of loss of primary canines, it is worth highlighting that the interceptive removal of primary canines can be augmented with anchorage support to limit associated space loss. It would be fascinating to see a further study evaluating whether this combination may offer any additional benefit. It would be excellent if the researchers who undertake this future project give the present paper and the original article a very careful read.
What can we conclude?
Based on this follow-up study, it does appear that the value of interceptive removal of primary canines to alleviate incisor irregularity is questionable at best. I think the author’s rhetorical question puts it very nicely indeed:
‘… is it necessary to interfere in the early mixed dentition with an invasive treatment such as removal of four intact primary canines, or could practitioners wait for their spontaneous exfoliation?’
If the initial study was a ‘nail in the coffin’ for interceptive extraction of primary canines, this follow-up might have hammered that nail home?
Professor of Orthodontics, Queen Mary University of London, UK