August 16, 2021

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”?

More importantly

“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.

Impact of early extraction of the deciduous canine on relief of severe crowding: Does it influence later orthodontic interventions?

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:

Participants: 

  • Late mixed or early permanent dentition
  • Previous inclusion in the initial study

Intervention Groups:

Intervention: Removal of all primary canines

Control: Observation only

Main outcomes:

  • 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?

Have your say!

  1. Since hearing Bob Little on the topic of late mixed dentition harvesting of the leeway space, I find space maintenance at this time more palatable to my patient and parent cohort. Putting a young child through extractions is difficult at the best of times and it is the careful management of these youngsters to create adults with a reduced risk of dental phobia that is at the forefront of my decision making. That said, there are times where extractions are a no-brainer but again, delaying this until it can be premolar extractions is probably a kindness. I try therefore to delay incisor alignment unless there are compelling psychosocial reasons to intervene early.

  2. When considering interceptive treatment I always find it useful to ask myself ‘is this going to simplify or avoid later orthodontic treatment?’. If the answer is no, or is unclear then we really have to think about if the early treatment is needed, especially if extractions or invasive treatment are planned. Explained to parents/patients in these terms they are generally quite happy to wait.

  3. What about periodontal health?? We are dentists after all and when considering primary canine extraction not only consider alignment but the developing of healthy supportive tissue as well. We can always align teeth, but can we give them better periodontal support? This is what I ask myself when considering primary canine extractions. THe retrution of the incisors can always be fixed in the second fase treatment to avoid extractions, but isnt this nicer when we have healthy bone to work with???

    • Just what I was thinking. Crowding in mixed dentition can lead to recession or ectopically erupting teeth not having keratonized gingiva on the facial. Could records be reviewed to look at this potential sequela?

  4. “The slightly extraction higher extraction rate in those having interceptive extractions may typify this.”

    There is a typo with the extra word extraction.

    Great review, !!

  5. Not sure if everyone would agree with the notion that “premolar extractions is probably a kindness” under any circumstances. Having said that, since the maxilla is immature at age 8.5yrs, could midfacial development be included in the risks, benefits and alternatives discussion at the time of informed consent – instead of procrastination, as alluded to by the study authors?

  6. Really interesting topic in interceptive orthodontics.Thanks a lot sir fr uploading this topic .

  7. For years I utilized a technique taught to me by and old mentor and friend. Instead of the lower C’s he and I both removed the lower D’s .the results were always as expected , the lowerC’s drifted distally on there own and magically the lower anteriors unraveled, this usually eliminates the need for a lower lingual arch and the deciduous canines still present kept the bite open. One of the consequences of removal of the lower C’s is unwanted bite deepening. Since I rarely extract ,this technique didn’t increase my extraction s at all .I have never seen any articles on this technique , but would love to read any that you know of

  8. What mid-facial development? Is the goal to bring homunculus back?

  9. I would refer readers to an article that addresses the way to handle this conundrum of early crowding of incisors in an effective manner.
    DeBaets, J., Chiarini, M., The Pseudo Class I: A Newly DefinedType of Malocclusion. J. Clinical Orthodontics, 1995. 29(2): p. 73-88.

  10. This further removes the rationale for action. Parents present with what they see as a developing problem. If treatment provides so little difference between the treatment and non-treatment groups then it cannot be justified in terms of cost, trauma to patient. The same applies for much of the early treatments advocated, if a difference after treatment between one and two phase is difficult to determine a couple of years after treatment then the logic of early intervention and probably greater cost must be justified in other ways.
    I have lasted 30 years without requesting deciduous canine extraction for crowding. Any day extractions can be avoided is a good day for a young patient. There are days where permanent extractions are indicated and maxillary deciduous canines to help the permanent canines erupt.

  11. what about extraction of contralateral C to avoid midline shift in cases of early loss of C??

    • Chris, please give us a study to confirm that removal of the contralateral primary canine results in less midline shift. I cannot find any and have looked for a long time. Here is a study looking at early loss of a single primary canine versus those that had late loss of the primary canine. Not much difference…

      Christensen RT, Fields HW, Christensen JR, Beck FM, Casamassimo PS, McTigue DJ. The effects of primary canine loss on permanent lower dental midline stability. Pediatric dentistry. 2018 Jul 15;40(4):279-84.

      • thanks for this! i definitely see movt and skewing of incisors towards the side of C loss but good to know it’s self correcting. cheers

  12. You should read The articles written by dugoni. And from the researchers at the University of the Pacific. I was taught to extract lower D’s 30 plus years ago. Along with a lingual holding arch. Long-term stability studies of this technique are excellent. Good luck David

  13. Generally, in the upper arch canines erupt after the first premolars, while in the lower arch, canines erupt before the first premolars. Extracting upper deciduous canines, ahead of schedule is likely to increase the chances of ‘blocked out canine’, as the first premolars will migrate to the empty space of extracted deciduous canines. In view of the above, I humbly submit that simultaneous(premature)extraction of both upper and lower deciduous canines, is biologically and chronologically not a rational decision in a majority of children. However after careful evaluation of Ortho Pantomo Gram,(OPG) this may be done only in a very small spectrum of cases. (I am aware of the Ericson & Kurol recommendations, but beg to defer)

  14. Severity of crowding specifically in that region is primary concern. More severe the crowding, better prognosis with c extrn. I think it’s worth to extract the c especially to relieve a upper lateral erupting into a cross bite. Additionally the case has to be followed up and if needed a serial extrn.

  15. It is ludicrous to attempt to avoid premolar extractions by trying these futile measures. Save the patient unnecessary Tx and just deal with crowding when appropriate and with exo.

  16. Well I have to disagree with most of you. I offer extraction of c’s to patients for the following reasons. If the extractions are timed right, the lateral incisors will significantly improve their position. The patients are happier with the appearance of their teeth, and there is less pressure to do two phase orthodontic treatment, or to even start treatment early. I also find that the permanent canines will be pushed buccally as they erupt, and I believe this results in more buccal bone development. In contrast, if the lateral incisors are palatally displaced, especially if they are in crossbite, there is poor development of their labial bone, and once corrected I believe there is often very little bone on the labial of the lateral incisor roots. Lastly, I find that once corrected, a canine that was buccally displaced is more stable than lateral incisors that were palatally displaced.
    So I explain these differences to my patients, and I give them the choice. I don’t push it, as I don’t like unnecessary extractions, but patients and parents have a right to be informed and to make their own decisions.

    • If the buccal bone develops with buccal movement of the canine why doesn’t it happen when you move the lateral buccally as well? Just wondered. Also are you sure that buccal canines are more stable than palatal incisors or is it just a feeling?

      • I am not convinced that when we move a tooth buccally, then we will get buccal bone grow over it. There is a lot of wishful thinking in this respect, but it is not confirmed with CBCTs, to my knowledge. However as teeth erupt in more buccal positions, and most of the maxillary teeth grow down more buccal or labial than the deciduous teeth, the arch form widens because we are getting buccal bone development which I believe is a direct result of the tooth eruption. So I am not saying we move a canine buccally and have extra bone grow. I am saying that if the canine erupts in a more buccal position, then I believe we are more likely to get buccal bone development. I cannot quote a study, but does anyone disagree with this concept?

        • The other point I forgot to make is that many orthodontists say the inter canine distance is fixed, or close to it. If we can persuade the canines to erupt in more buccal positions, the intercanine distance will be greater, and so we can be more confident of our outcome if we do some expansion.

  17. It would be interesting to investigate the lower incisor stability (i.e. relapse) with and without early removal of primary lower canines. I was always taught that allowing the lower incisors to align ‘naturally’ through extraction of the C’s allowed for greater long-term stability.

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