Is non-extraction kicking the extraction decision into the long grass?
The debate over whether to extract teeth in orthodontic treatment has been ongoing since the dawn of time. The two main camps seem firmly committed to their positions, and it’s unlikely that the arguments will be resolved soon. However, this new paper presents evidence of the potential harmful effects of non-extraction treatment on the eruption of second molars.
Supporters of non-extraction treatment argue that removing teeth can lead to issues like TMD, flattened profiles, airway problems, and even affect educational attainment. However, there is little evidence to support these claims. Nonetheless, orthodontists and dentists often recommend non-extraction treatment for all patients, suggesting that we can develop the arches to accommodate all teeth. This contradicts our current understanding, which indicates that we cannot significantly grow bone.
Indeed, if it were possible to develop the arches, treating non-extraction should not influence the eruption of the second permanent molars. This research examined this problem.
A team from North Carolina did this study. The AJO-DDO published the paper.
Second molar eruption disturbances in borderline extraction orthodontic patients
Thomas Patrick et al
AJO-DDO Advance access, https://doi.org/10.1016/j.ajodo.2024.06.016
This is an open-access paper, so anyone can read it without subscribing to the journal.
What did they ask?
They asked these questions.
“What is the frequency and severity of second molar eruption disturbances in non-extraction v extraction treatment of patients with borderline crowding”?
And
“What predicted second molar impactions”?
What did they do?
They retrospectively examined case records of patients treated at the Department of Orthodontics and a private orthodontic practice.
The inclusion criteria for the study were orthodontics patients who
- Were aged 10-15 years at the start of treatment with complete dentitions and unerupted second molars.
- They had full records
- The team classified mild crowding as <5mm, borderline was 5-9mm.
They also scored second molar root formation.
At the end of treatment, they classified second molar eruption disturbances using post-treatment panoramic radiographs and photographs. They used several measures to classify the degree and severity of impaction.
Finally, they used univariate statistics to evaluate the data.
What did they find?
The final sample was 535 individual arches from 346 patients.
They classified each arch as
- Mild crowding (<5mm)
- Borderline crowding treated non-extraction (5-9mm)
- Borderline crowding treated with extractions. (5-9mm)
They provided a large amount of data and I looked at the main clinically important information. These were the most important findings.
In the maxilla, 20% of second molars were impacted in the borderline group treated with non-extraction versus only 5.2% when treated with extractions.
In the mandible, 27.6% of second molars were impacted in the borderline group treated non-extraction and 7.1% in the extraction group.
There was no difference in second molar impaction frequency between the non-extraction mild crowding group (18%) and the non-extraction borderline group (27.6%) in the mandible. Similarly, the maxilla had a 15% prevalence of impactions for the mild crowding and 20% for the borderline non-extraction groups.
When they looked at predictors of impaction. They found that a second molar is at a higher risk of impaction if it is apically positioned in the maxilla or associated with reduced posterior arch length and increased mesial angulation in the mandible.
Their overall conclusions were
“In patients with borderline crowding, extraction treatment reduces the risk of second molar eruption disturbances”.
“There is no difference in the frequency of impaction between patients who had non-extraction treatment of borderline crowding compared with those with mild crowding treated non-extraction”.
What did I think?
This paper contains valuable insights. However, we need to be mindful of the potential for selection bias in any retrospective study. We also need to explore alternative study designs. For instance, conducting a randomised trial on this topic is not feasible because it is unlikely that many patients would consent to extraction treatment when they are aware that non-extraction is an option. As a result, we need to interpret the data with caution.
It appears that there was no difference in the frequency of impactions between non-extraction borderline and mild crowding cases. Therefore, we can only conclude that extracting teeth in borderline cases reduces the likelihood of impactions. This finding is clinically valuable.
We should be cautious about these findings because it’s possible that the operators did not bond the second permanent molars. Which would have influenced their final position. However, it’s worth noting that not all operators bond second molars. Additionally, bonding second molars may occasionally lead to the impaction being transferred to the third molars. Furthermore, the authors were not able to provide any details of the mechanics being used in the non-extraction cases. This information would be important when deciding the optimum treatment for these borderline patients.
Final thoughts
As often seen in many papers exploring the decision between extraction or non-extraction, this study raises numerous questions. Nevertheless, I can’t help thinking that blindly adhering to the non-extraction approach for all patients in the hope of bone development is not sound orthodontics. This study provides some evidence to suggest that this approach is likely to simply postpone a space shortage problem.
Years ago , Professor JRE Mills observed that ‘non-extraction treatment’ followed by the extraction of impacted third molars is not actually ‘non-extraction treatment’
Have been a non-extraction -ist (90% – non-exo) since 1986 and of course case selection has prevented second molar impactions and bonding them as required. It must be working otherwise I’d be seeing relapses galore.
Have been a non-extraction-ist (90% non-exo) since 1986.
2nd molars have never been a problem through case selection and bonding them as needed.
I would be in trouble now if relapse was a problem.
Dear Sir,
As a profession, we are rightly focussed on possible molar impactions and resultant occlusion in non extraction cases, but it would be worthwhile to do a study on residual incisor proclination +/- any labial recession in borderline cases that are treated non-extraction.
Indeed a vast proportion of cases in any cohort can be successfully treated without extraction.
Flat profiles are not desirable but neither are the incisors that procline excessively, possibly affecting canine guidance; not to mention the poor aesthetics and reduced patient satisfaction with such a result where extraction of second premolars would have allowed sufficient AP decompensation in carefully selected cases.
Maybe, we need to have more studies focussed on extraction plans with anchorage planning, and see those finishes to better inform our decision making.
One size never fits all.
Thank you for yet another thought-provoking blog.
Yours sincerely,
Mr Karun Sagar, BDS
Orthodontic Assistant
So very many of these severely crowded cases ultimately end up with gingival recession, relapse and often unfavorable esthetics.
The etiology remains ‘big teeth in deficient alveolar bone – genetics and anthropology’
As a paradigm shift, how about early extraction of usually impacted third molars, SFOT to minimize future recession and relapse, and arch expansion both distally and horizontally.
Bone anchors for distalisation is most effective.
This adds a biological approach to the orthodontic treatment plan.
Colin Richman DMD. (Periodontist)
Dr Richman:
I agree that a biological approach is the way forward. I might modify your statement “The etiology remains ‘big teeth in deficient alveolar bone – genetics and anthropology” to read “The etiology remains ‘teeth in deficient alveolar bone – genetics and epigenetics’. The reason is that according to the human evolutionary record, teeth have been increasing in number, size (number of cusps) and enamel thickness. Homo sapiens have the biggest teeth (and biggest brains). Tooth development is downstream from bone development, according to temporo-spatial patterning. So we can’t “blame the teeth” for being too big. It’s developmental compensation that has historically been labeled as “crowding”. So the approach would be clinical decompensation since stem cell populations can be recruited from the periodontium (which is not a ligament), giving rise to an epigenetic approach that Darwin was unable to capture around the time when orthodontic theory was beginning to emerge.
Thank you for this review. 20% is a high number. Consideration if posterior crowding is essential in orthodontic treatment planning. Ensuring the second molars aren’t impacted is the orthodontist’s responsibility. Sometimes orthodontic treatment is started too early, and finished without evaluating the second molars. They may then become impacted resulting in a need for further treatment.
It may be prudent for the orthodontist to wait for the second molars to erupt, or just begin to erupt, so the second molars are bonded and aligned and if impaction occurs it is managed during treatment.
Why would anyone want to belong to an “ist” group be it extractionist or non-extractionist? Aren’t we all treating, however we are treating, in a manner that its consistent with the patient’s clinical and radiographic presentation, the established goals for treatment, and the mechanotherapeutic approach to achieve those goals? Non-extraction therapy is not a goal; it is a means to achieve a goal, as is extraction therapy; and if extraction is chosen, deciding which dental units are to be sacrificed in each quadrant given the specifics of each case while providing due consideration and care for the consequences of adopting either approach.
If we can’t or haven’t produced high quality research on the ext/non-ext over the last 125 years, shame on us. If we have produced the evidence and it is not being followed, shame on our educational system. If we have adequately taught it and it is being ignored, shame on the ignorant ostriches among us.
Which of the three options do you think we have the evidence for – evidence, education, or action?
Stephen Murray
Swords Orthodontics
AMEN! Extraction is a treatment modality, not a goal!!!
It is a lot easier to sell the case if you say you don’t have to extract!
I don’t have dental training & wonder if the practitioners on this blog can answer a question I’ve always wondered : if a patient with severe crowding has expansion without extraction .. how does expansion of lower teeth in the mandible work?
Many thanks
I’d be interested to hear a few other contributors answer with their perspective, but here’s mine:
Roughly speaking, teeth are arranged on an arch shape when you look at the biting surfaces of the teeth on each jaw. If you move the front teeth forward, the back teeth backward and the side teeth more to the side then you make that arch longer in length/perimeter. That’s basically the same in both jaws.
There are a variety of ways you can achieve this with various appliances in various combinations.*
You can expand the upper arch with expander appliances (clue’s in the name) but that alone is usually moving the side teeth sideways towards the cheeks. Other appliances which don’t have an obvious expansion-suggesting name can create expansionary movements on front and back teeth.
In the lower jaw you don’t usually have an appliance with the word expansion in the name but you get expansionary movements with various appliances that move the teeth on to that bigger arch form. There might be some orthodontists that would suggest surgically splitting the mandible in the midline and bolting on an expansion screw to widen it near the midline at the front, but that wouldn’t be a mainstream sort of treatment.
*when, and why (or whether or not), you should attempt to do this is largely the fundamental cause of discussion here on today’s blog post – though elsewhere many people will spend most of their time debating the best kind of “how”.
Thank you for explaining this ~ much appreciated!
This “fear” of treating cases with extraction usually stems from one or more of three reasons
1.Inability or unwillingness to understand or accept the established scientific literature that has debunked all the mythical horrors attributed to premolar extractions. Individuals who persist in this form of erroneous reasoning are often afflicted with a high degree of cognitive dissonance
2. Failure to recognize or diagnose incisor protrusion, posterior crowding and space requirements. Those who “shoot from the hip” usually do so because they have not bothered to establish Tx goals for where the teeth should be positioned.
3. Poor understanding or incompetent execution of mechanics in extraction cases. Situations requiring premolar exos necessitate skillful application of far more complex biomechanics, than the average non-extraction case.
Thus, you have the many acolytes of Dunning and Kruger, who proudly don the Epaulette of being a Non-Extractionist. Needless to say, such doyens of premolar protection also never bother to put the plaster on the table, or present superimpositions. However, they are being honest when they say that “they” cannot do this. Those who can, Do. Those who can’t, Make Excuses. Be it due to ignorance or ineptitude.
Non extraction is surely not an option in cases of moderate to severe crowding? Just expanding everything and proclining teeth, often through the alveolar plate, leads to dehiscences and fenestrations and associated perio problems later on? What then?
An interesting paper but only borderline cases being considered limits its usefulness.
This is like the Democrat v. Republican argument. Each case is different. Though I tended to the non-extraction side of the argument, things like anatomy, age of inititation of treatment, and others made some cases definitely, extraction. Did not have a problem with that. I agree with the above observation that I saw about the same percentage of impacted 2nd molars with both Parties. If I did my due diligence, I treated appropriately. Dehiscenses, fenestrations occurred, very infrequently thankfully, both ways. Gingival problems were often avoided or recognized for appropriate treatment the less stupid I got with age. Having treated two generations (some three) I have no regrets. I was a non-extractionist, but sometimes you have to vote for the other guy.
I think I’d need to hear more about the participants. If someone is 15 and doesn’t have second molars erupted when they start treatment I wouldn’t be as surprised if they had impacted second molars regardless of how they were treated. Also, it’s not clear what teeth were extracted. I think impacted second molars are a lot less likely if first molars were extracted compared to first premolars or no extractions.
Stephen Murray
Swords Ortho
This article is further evidence that we should be developing the deficient arches of patients earlier/younger than the subjects in this study. Their subjects were 10-15yo with “complete dentitions.” So the treatment, by definition, is reactive at that point since you’re trying to cram erupted teeth into a small/deficient foundation. Of course you’re going to have an impact on 2nd molar space! That’s not news.
Crowding is almost always due to small jaws, NOT large teeth. McNamara, O’Connor, and Howe published a great article on this in AJO in 1983, as did Mills in Angle in 1964. As orthodontists and dentofacial orthopedists, we are more than capable of normalizing the growth of young jaws/faces. And when you do, your patients won’t end up having “borderline” crowding in the complete dentition because your growth modification (if you do it correctly, which is a separate issue) will make space for the teeth. McNamara concludes this very thing in his 1983 paper. It’s honestly not very complicated and I’m shocked that we continue to oppose taking a more proactive approach to our treatment. I literally can’t think of another medical or dental profession that is opposed to trying to prevent disease, likes to wait until it gets really bad to try and clean up the mess, and then argues about who cleans it up “less badly.” We should be (and do) better than that!
It’s long past time that our profession transitions from a reactive approach where we argue about whether or not to extract teeth once patients are in the “complete dentition,” to a proactive approach where we normalize deficient growth in preadolescent patients to minimize the severity of crowding/malocclusion. The crazy thing is, Angle, Bogue, Holtzman, and others were saying this very thing over 100 years ago! Even Tweed acknowledged this when in 1963 he stated, “Knowledge will gradually replace harsh mechanics and, in the not too distant future, the vast majority of orthodontic treatment will be carried out in the mixed dentition period of growth and development, prior to the difficult age of adolescence.” I bet he never would have believed that over 60 years later we’d still be arguing about how to cram normal-sized teeth into small jaws at the “difficult age of adolescence.” Thank you for posting an article that proves the point I so often try to make!!
Thanks for giving us an insight into the thoughts and evidence underpinning the concept of arch development.
Results of study we did a number of years ago:
Impaction of permanent second mandibular molars in patients undergoing nonextraction via E-space preservation with a passive lingual arch is 10 to 20 times more prevalent than that observed in the general population. Risk of impaction is best predicted by the pretreatment intermolar angulation between first and second permanent mandibular molars.
E-space preservation: Is there a relationship to mandibular second molar impaction?
Andrew Sonis; Marc Ackerman
Angle Orthod (2011) 81 (6): 1045–1049.
https://doi.org/10.2319/030711-165.1
I have looked at the comments on this post and they raised several important points. As a result, I have decided to try to condense these into one simple concept.
This is that we should not be non-ex or extraction orthodontists. This is because our “tribe” is not important or relevant. We need to simply decide on the end goals of our treatment. This should be based on a combination of research evidence and clinical experience. This then should let us decide whether we are going to extract or not. This is a simple concept that is probably followed by most orthodontists. It is just the fringe who either do not understand or are unwilling to follow science who need or want to form their own “tribe”.