To extract or not to extract, a debate that is as old as our profession, the first recorded debate was 1911 with Case and Dewey and continues today. The pendulum does not rest, swinging back and forth with protagonists and antagonists with differing beliefs, theories, and limited evidence. Can extractions adversely affect facial aesthetics or enhance them? This blog will explore the arguments from both sides and the evidence.
The classic argument for extractions came from Charles Tweed and Raymond Begg was based on their own treated cases (from their training with Edward Angle). They both observed a lack of stability of their treated cases, protrusive profiles, and loss of interdental papilla. They re-treated their cases with extractions and presented their findings in the 1940s. A pause here to highlight the reflective practice of both, the re-assess their treatment outcomes, label them as poor and re-treated them. Reflective practitioner, the time defying characteristic of excellence.
The original argument against extractions came from Edward Angle was that the jaws can and should fit all 32 teeth for ideal occlusion and esthetics. The premise of Angle’s philosophy was underpinned by Wolff’s law, a 19th century German anatomist who stated bone formation was related to the stress applied, and Edward Angle assumed bone would surround the teeth in their new position. Fast forward to the 1980s and reports began to show flat faces from extraction treatment, TMD and breathing problems, as well as the advent of self-ligating brackets and fixed bonded retainers, resulting in extraction rates declining.
Over the coming blogs we will be exploring some of these key claims, from both a theory and evidence-based perspective, this blog will focus on facial changes through extraction based orthodontics.
A ‘flat face’ refers to the retraction of the upper and lower lips through orthodontic retraction of the upper and lower incisors. Retraction of the lip increases the nasolabial and labiomental fold angle, resulting the ‘flattening’ of the midface. The lips drape over the incisors and are tented or propped forwards by the anterior teeth, however the relationship of dental retraction to lip retraction is not one-to-one.
A recent systematic review explored this topic of facial changes with extractions for orthodontic treatment. A whopping 52 papers and 1876 patients were used in the review Konstantonis 2018. The findings are below for extraction of 4 first premolars:
Konstantonis went one step further and correlated the amount of incisor retraction to lip retraction, for every 1mm of incisor retraction the lower lip is retracted 0.7mm, the upper lip 0.65mm, and the nasolabial angle is increased by 1.6 °. An explanation has been proposed for the disparity between the upper and lower lip movement, the muscle of the lip (orbicularis oris) inserts from the upper lip to the nasal septum, resulting in an additional point of attachment, which the lower lip does not have, and therefore the lower lip is subject to greater effects from dental movements Oomori 2020.
The ‘flattening’ effect also requires context, indeed the face becomes flatter but does it affect facial aesthetics? Within the same review subjective measures of aesthetics by lay people, dentists and orthodontists were very small, enough for the authors to consider the aesthetic changes no different between extractions and non-extraction (interestingly the findings favoured extractions marginally). So the face does become flatter, however the averages presented above had wide range of confidence intervals, in other words the effects of extractions are small, variable, and the effects do not alter perception of aesthetics by lay or professional people.
The above information evidence lips do become more retrusive following extractions. It is important to note that there is a significant range of values associated with mean findings, indicating significant variation between individuals, the authors comment “no consistent predictions of profile response can be made”. This begs the question, what variables affect the response of the lips? This question is explored further in this blog.
Lip shape and size also change through extractions and retraction, the analogy of a squashed balloon being released explains why the lip would change in shape and size, incidentally Farooq’s balloon animals are sight to behold. Facial scans have shown lips became shorter by 2.8mm (total vermillion height upper and lower) and thinner by 1.06-2.05mm following extractions Liu 2019. The upper and lower lip appear to respond differently to retraction, with the upper lip undergoing a clockwise rotation of 5o following extraction and retraction, whereas the lower lip has a linear direction of movement following extraction and retraction. It sounds like another perceived strike against extractions and facial aesthetics, however the paper by Liu also explored the ratio of these changes, and showed the lips remained in a similar ratio, whether extraction or non-extraction. This suggests that facial aesthetics is influenced more by ratios of landmarks rather than quantitative changes.
Konstantonis notes in his paper the degree of unpredictability of lip response, and indicated lip thickness may influence how the lips respond. It has been reported patients with thin lips and high / short lips undergo greater retraction of than patients with thicker lips (Correlation thin lips 0.95 Vs thick lips 0.56 Oliver 1982), However this area of research is sparce and not populated well enough to draw firm associations.
Retraction of the anterior teeth can alter smile aesthetics, mainly with changes to both the smile arc and buccal corridors. Retraction of anterior teeth deepens the smile arc, however there was no clinically significant difference when assessed Mah 2014. Interestingly it was the use of class 2 mechanics felt responsible for the clockwise rotation of the occlusal plane, and deepening of the smile arc, rather than the extraction and retraction mechanics.
Increased size of buccal corridors has been proposed as a consequence of dental extractions. The archform is thought to narrow due to reduced dental units. Janson 2011 investigated this in a systematic review and concluded extractions had no impact on buccal corridors. A tenet of good clinical practice is to maintain the original archform and dimensions, with few exceptions, therefore the with good clinical practice it would be expected that no changes to the buccal corridors would be observed.
There is the component of age-related changes to be considered as an influencing factor of the flat face. All of the components, notably the lips, chin and nose all undergo changes with age.
Lip retrusion occurs by approximately 2.4mm in extraction cases and 3.0 mm in non-extraction cases over a 14 year period following orthodontic treatment Paquette 1992. The lip morphology also changes with a thinning of the lip from the age of 16 Sarver 2010. The nose becomes more protrusive by 3.27mm Sforza 2011, the chin becomes more protrusive in late adolescence by 2.4mm in males and 1.5mm in females Nanda 1990. Paquette’s study is the most notable paper, where long term age related changes over 14 years more significant than treatment changes from extraction or non-extraction cases.
Overall extractions on average have a small effect on the facial profile, the lips do become more retrusive and the lips flatten, however these changes are small and do not affect the perception of aesthetics or smile. As with other aesthetics changes, it appears the ageing process is the greatest factor.
It is to be noted averages have been described in the papers, and there are some factors which can influence the changes from extractions and retraction, such as an initial thin lip or retrusive profile., it is also possible to create significant retrusion with poor planning and mechanics, as it is possible to create a protrusive profile through inappropriate non-extraction treatment. A statement from Peck regarding this topic “Don’t get involved in orthodontic treatment ‘religions.’ Diagnose and treat each patient on an individualized basis. There are no miracle shortcuts for good orthodontics”, Peck 2017. There will not be an appliance nor mechanics which replaces diagnosis (Farooq 2022, after too much coffee).
On the coming blogs, we will discuss the effect of extraction on the health aspects, regarding periodontal problems, TMD, and airways disorders.
Join in the conversation, leave your thoughts, questions and opinions in a comment below.
We hope you have enjoyed this blog, This blog started with a conversation between Kerolos AlHakeem, Farooq Ahmed and James Andrews, to follow more conversations, clinical tips and commentaries on orthodontics please check us out on Instagram / facebook