Orthodontic extraction practices: a cross-sectional survey of orthodontists in Australia

The role of the extraction of permanent teeth as part of an orthodontic treatment plan has been controversial since the establishment of the specialty at the beginning of the 20th century.¹ Angle’s belief that successful orthodontic treatment could be achieved without the removal of teeth was challenged as the 20th century progressed.^1,2 Concerns regarding the aesthetic outcomes and the instability associated with non-extraction treatment enabled a gradual acceptance of the extraction of premolar teeth as part of orthodontic therapy.³

Research related to orthodontic extraction frequency and patterns has usually surveyed practitioners regarding their opinions via a questionnaire (with or without reference to specific cases) or the retrospective assessment of clinical records. Studies have shown that extraction rates indicated by orthodontists have fluctuated over the past century. Proffit, for example, found that the extraction rate at the University of North Carolina dental facility more than doubled from 30% in the early 1950s to 76% in 1968 before reducing to almost 28% in the early 1990s.⁴ More recent investigations have also shown similar downward trends in extraction frequency in orthodontic treatment plans over the last few decades.^5–8 The varying rates of first premolar extraction appear to have played a significant role in overall changes in extraction frequency, more so than the extraction of other teeth.^4,5

While the orthodontically prescribed removal of teeth has become an accepted treatment approach for the relief of crowding, and the correction of increased/decreased overjet and overbite, a myriad of (sometimes conflicting) factors contribute to a clinician’s decision to plan extractions.^7,9 For example, the perceived potential deleterious impact on facial aesthetics and the patient- and practitioner-targeted marketing of orthodontic appliances that preclude extractions have made some clinicians reluctant to prescribe extractions.^10–12

However, the possible adverse effects of alternative treatment options to extraction (such as transverse expansion and incisor proclination) on the periodontium invites caution of a non-extraction approach.¹³ Furthermore, the ‘judgmental’ (in which two orthodontists agree on what they see but differ on the treatment) or ‘perceptual’ (in which orthodontists differ on what they perceive) variations in orthodontists’ decision-making processes are also likely to impact on whether extractions are prescribed.¹⁴ Moreover, patient expectations and the acceptance of indefinite retention have further influenced the rates of orthodontic extractions.⁹

A recent survey conducted in the UK found that 95.6% of orthodontists had reduced the number of orthodontic patients prescribed extractions over the previous 5 to 10 years.⁷ In addition, the survey found that facial and smile aesthetics and the greater use of IPR were considerations that significantly influenced the decreasing extraction rates in that country.

To date, there has been little exploration into orthodontic extraction practices and trends in Australia. The aims of the present investigation were, therefore, to survey Australian-based orthodontists regarding their opinions on:

Their current orthodontic extraction practices and

Approval for the study was granted by the Human Research Ethics Committee of the University of Adelaide (H-2021-118). The survey was adapted with permission from a similar questionnaire used in the UK.⁷ Participants were questioned on demographic details related to their principal Australian State/Territory of practice, the number of years since qualifying as a specialist orthodontist and their occupational clinical setting. The participants were questioned regarding the number of recently treated patients with a Class I malocclusion who were considered to require the extraction of permanent teeth as part of the treatment plan. In addition, the extent of crowding that could be comfortably corrected without extractions, was also asked.

Further questions related to the change in the number of patients treated with the extraction of permanent teeth in the previous 5 to 10 years. The survey was considered complete for those who had not been in orthodontic practice for at least 5 years and those who responded with no change in extraction frequency. Those respondents who had not been in practice for at least 5 years were excluded from further analysis.

If participants indicated that they had changed extractions rates, they were questioned regarding the age of the patients to which the changes applied. In addition, information was asked regarding the level a series of factors played in influencing the changes. A final question pertained to a participant’s change in a variety of space-creating approaches used over the previous 5 to 10 years when addressing moderate crowding in patients with Class I crowding. Furthermore, participants were invited to provide further information in free text boxes.

The participants were chosen based on their membership of the Australian Society of Orthodontists (ASO). Only those registered under the specialty of orthodontics with the country’s regulator of health practitioners, the Australian Health Practitioner Regulation Authority (AHPRA) are entitled to be members of the ASO. The ASO is the main professional body of orthodontists in Australia, and approximately 80% of AHPRA registered orthodontists are members of the Society.¹⁵

Pre-piloting followed by piloting of the questionnaire to 4 specialist orthodontists was carried out to validate and to gauge the time required to respond to the later survey sent to all participants in Australia.¹⁶ The electronic (e)-survey was designed using the SurveyMonkey^® platform and was distributed to members of the ASO via e-mail on September 20, 2021. The survey was closed on December 20, 2021.

Data were exported to GraphPad Prism^® (GraphPad Software Inc., La Jolla, Calif, United States) for statistical analyses. Descriptive statistics were computed, and the Mann–Whitney test was carried out to determine differences in the mean number of years in practice of the orthodontists who reported an increase in extraction rates and the orthodontists who responded that they had reduced extraction rates. A Fisher’s Exact Test was carried out to determine whether there were any differences in reported extraction rates between those orthodontists who used a self-ligated pre-adjusted Edgewise system compared to those who used a conventionally ligated pre-adjusted Edgewise system as their primary fixed appliance.

A response rate of 35.05% was recorded which comprised 163 out of 465 potential participating respondents. Not all participants answered all questions. Table I indicates that most participants were male, and the majority worked in a private practice setting.

The mean (SD) number of years practiced by participants as specialist orthodontists was 16.3 (11.03), [Range 1–42; 95% CI: 14.6–18.01]. Twenty-six participants (15.95%) had practiced for less than 5 years. Figure 1 shows that the conventionally ligated pre-adjusted Edgewise fixed appliance was the appliance with which the majority of participants used primarily in their training, and which the majority currently use.

Figure 1.

Respondents estimated that permanent teeth were extracted in a mean 22.06% (SD: 14.26; 95% CI: 19.84–24.27) of the last 50 child/adolescent treated patients who presented with a Class I malocclusion. This compared with their estimation of a mean of 21.03% (SD: 15.92; 95% CI: 18.56–23.5) of the last 50 adult patients presenting with a Class I malocclusion.

Figure 2 shows that most orthodontists were comfortable in carrying out non-extraction treatment in patients with crowding of up to 6 mm.

Figure 2.

Of those respondents who had practiced for more than 5 years, 76 (55.89%) orthodontists considered that the number of patients treated by accompanying extractions was unchanged over the past 5 to 10 years while 47 (34.55%) believed that their prescribed extraction protocol had decreased over the same period. Most of the changes were observed in both adults and children/adolescents (73.33%), followed by children/adolescents only (18.33%) and adults only (8.33%).

The mean (SD) number of years in practice of orthodontists who reported an increased rate of prescribed extractions was 23.92 (7.5) [95% CI: 19.36–28.48] while the mean (SD) number of years in practice of orthodontists who reported a decreased rate of prescribed extractions was 17.26 (9.12) [95% CI: 14.58–19.93]. A Mann–Whitney test indicated that the mean rates were statistically different (p = 0.0102). A Fisher’s Exact Test indicated that orthodontists who used pre-adjusted Edgewise fixed appliances with self-ligated brackets were not more likely to have reduced the number of prescribed orthodontic extractions compared to those who used the same fixed appliance system with conventionally ligated brackets (p > 0.05). Table II outlines the level of influence of various factors on extraction decisions by orthodontists whose prescribed extraction rates had decreased over the past 5 to 10 years. Meanwhile, Table III summarises the level of influence of various factors on extraction decisions by orthodontists whose prescribed extraction rates had increased over the past 5 to 10 years.

Table IV outlines the changes in approach in the management of moderate crowding in Class I patients between orthodontists who considered that they had reduced prescribed extraction rates over the past 5 to 10 years. Table V summarises the changes in approach in the management of moderate crowding in Class I patients by orthodontists who believed that their extraction rates had increased over the past 5 to 10 years.

In addition, 6 (4.37%) participants indicated in the free text box that the frequency of lower incisor extraction had increased in adult patients over the past 5 to 10 years.

The present study aimed to survey the opinions of Australian-based orthodontists on current and recent practices in relation to the extraction of permanent teeth as part of an orthodontic treatment plan. The level of controversy that this topic has aroused highlights the relevance of this investigation.

Although the response rate of 35.05% was disappointing and a potential limitation of the study, it compares favourably with the 13 to 16% observed in similar surveys and 29.5% recorded in a recent study on orthodontic practices of Australian-based orthodontists.^7,17,18 Despite the relatively low response rate, however, participation was relatively evenly spread between the Australian states/territories and the number of years of practice as orthodontic specialists.¹⁶ Additionally, the overall gender divide corresponded with the male/female membership of the ASO.¹⁸ The number of male respondents (71.2%) in the present survey, for example, compared with 71 to 75% recorded in recent surveys and corresponds with the 71% recorded in the ASO database.^15,18 Furthermore, the mean number of years in practice by each orthodontist was 16.3 which compares with a mean of 15.57 years and a median of 18 years per orthodontist in recent surveys of Australian-based orthodontists.^15,18

The orthodontic respondents in the present survey estimated that permanent teeth were extracted in 21.03 to 22.06% of recent Class I malocclusion cases. It compares with the overall extraction rate of 25% in a recent US study documenting orthodontic treatment in 2184 patients over a 10-year period, and 24% in a Belgian survey of orthodontists with greater than 15 years’ experience.^6,19 The slightly higher rate in the former study may be due to the inclusion of all malocclusion classes.

In the present study, 25.8% of respondents routinely used a self-ligation fixed appliance system. This is greater than the 9.1% recorded in the UK study.⁷ However, there was no difference in the extraction rate between self-ligated and conventionally ligated appliance systems reported by orthodontists in the present survey. The claim that self-ligated appliances reduced the need for extractions in orthodontic treatment was not supported by this investigation. The results suggest that orthodontists consider other purported advantages, such as quicker treatment times and shorter adjustment appointments, in their decision to use self-ligation.^20,21

Orthodontic respondents were more comfortable in accepting a greater level of crowding in adult patients compared to children/adolescent patients when undertaking non-extraction orthodontic treatment. This may reflect the perceived difficulties associated with space closure and/or the limited treatment goals in adult orthodontic treatment.⁷ In addition, many adult patients may have had extractions as part of a previous course of orthodontic care and further extractions may be undesirable and/or inappropriate.²² However, the perception that adults are averse to extractions as part of an orthodontic treatment plan is not necessarily supported by the literature.²³

In the present study, over half of the surveyed participants with at least five years orthodontic experience, reported that the proportion of their patients treated by extractions had remained unchanged over the past 5 to 10 years. This may reflect previous conclusions that extraction rates have been relatively constant in some countries over the past 15 years.⁵ However, 34.55% of the orthodontists believed that their extraction rates had decreased over the time-period prescribed in the present survey. This contrasts with 95.6% of orthodontists in a recent UK study.⁷ Nevertheless, it compares with 24% of participants in a survey of members of the American Association of Orthodontists who reported that extractions had reduced over the previous 10 years and a reduction of approximately 20% observed in an analysis of patient records in a Brazilian university clinic over the 30-year period prior to 2011.^8,17

The present investigation determined that more experienced orthodontists were significantly more likely to prescribe the extraction of permanent teeth as part of their orthodontic treatment plan. This corresponds with the findings of a 2017 US survey in which orthodontists with greater than 15 years’ experience chose the extraction of teeth in a series of Class I ‘borderline’ cases significantly more frequently than those with less than 5 years’ experience.¹⁷ Further research is required to determine whether this reflects the influence of the orthodontic teaching principles delivered during the time of their postgraduate education or whether factors related to their greater experience may have influenced their ‘judgmental’ and/or ‘perceptual’ variations.^14,24,25

A move away from the extraction of first premolars was observed in those orthodontists who stated that they had reduced their extraction rates over the previous 5 to 10 years. This is consistent with the views of orthodontists and the outcomes of longitudinal data analyses previously reported.^4,5,7 However, an increased rate of lower incisor extraction in adult patients was indicated by orthodontists who reported increased and decreased extraction rates. This may reflect the increasing acceptance of the extraction of this tooth in specific situations.²⁶

Not surprisingly, alternative ‘space creation strategies’ such as ‘combined’ IPR and arch lengthening in children/adolescents and IPR in adults were commonly adopted by the surveyed orthodontists. Approximately 57% of the orthodontists who reported decreasing extraction rates believed that an increased use of IPR had a moderate-to-major influence on their decision to extract. This compares with 49% recorded in the UK survey and may reflect the acceptance by orthodontists that IPR is a minimally invasive procedure with little long-term adverse effects.²⁷

Interestingly, only 29.57 to 30.96% of those orthodontists who reported decreased extraction rates considered the increased use of bonded retainers a significant influence on their extraction decision. This is almost identical to the 30.7% observed in the recent UK study and suggests that orthodontists considered that there are factors, in addition to the potential instability associated with increased lower incisor proclination, implicated in post-orthodontic treatment relapse.^7,28,29

More than 80% of the orthodontic respondents who reported decreased extraction rates indicated that facial and smile aesthetics had a moderate/major influence on their decision to extract. This suggests that many considered the potential deleterious effects of orthodontic extractions on the patient’s soft tissue profile.¹¹ It reflects the finding of a 2019 survey of Belgian-based orthodontists that the single most important factor governing the extraction of teeth, even more so than crowding, was the soft tissue profile.¹⁹ Nevertheless, this has been (and is likely to remain) a controversial topic with some researchers finding the soft tissue profile responds directly to orthodontic extraction and others concluding that the soft tissue response is less dependent on hard tissue changes.^{11,12,30–32} The latter viewpoint may be noted in the present survey in which only 46% of the orthodontic respondents who stated that their extraction rates had increased indicated that facial aesthetics had a moderate/major influence on their decision to extract.

The limitations of the present study must be recognised. The survey did not investigate extractions associated with orthodontic clear aligner treatment. This may have influenced the responses regarding the participants’ orthodontic extraction practices. In addition, some of the survey’s questions risked introducing memory bias. Participants were asked to recall information that may not agree with a quantitative assessment of their extraction practices. A requirement to provide quantitative data would have ensured a more accurate assessment of orthodontic extraction practices. It, however, would likely have reduced the response rate further. Nevertheless, many of the findings of the present survey are consistent with the outcomes of studies conducted in other countries.

Future research would ideally require a randomised controlled trial with a lengthy post-treatment follow-up.^7,9,33 Notwithstanding the ethical issues surrounding randomising ‘borderline’ cases to extraction and non-extraction therapies, attempting to minimise the potential confounding factors to provide clear answers is likely to prove extremely challenging. Nevertheless, a decision to extract permanent teeth should be part of an orthodontic treatment plan tailored for the individual patient. The plan should take all space requirements and space-creating strategies into account while being cognisant of the relevant evidence base.³⁴