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Serial Extractions Is it a serial problem or solution?

This blog explores the concept of interceptive management of the crowded dentition through serial extractions. Although the concept of serial extractions was described in 1947, the once popular interceptive treatment has become a less common in clinical practice. This blog will look at the concept behind serial extractions, the merits of its use, the contentious issues surrounding its use from the evidence, and recent modifications to the classic protocol which aim to re-popularise the same concept, with less extractions.

What are serial extractions?

 

Serial extractions are a sequence of interceptive extractions to resolve crowding in the mixed dentition. The intent to “to avoid the need for active orthodontic treatment or reduce it to a minimum” Hotz 1970. It has been proposed the active treatment times are shorter, treatment is simpler and there is a reduction on the economic burden on the parents. Serial extractions therefore were seen as effective (in terms of final occlusal outcomes) and efficient (reduced treatment period). However ‘active orthodontic treatment’ is one side of a two sided coin, and we will also explore the significant passive or monitoring time required for serial extractions and what ‘minimum active orthodontic treatment’ actually means in terms of clinical practice.

The ideal cases for serial extractions are class 1 cases, with no or minimal skeletal discrepancy. 8-10 mm of crowding, and no significant overbite. 8mm of crowding is more likely to require active orthodontic treatment, O’Shaughnessy 2011, Proffit 2014

The sequence is as follows (Graber 1971):

  1. Extraction of primary canines: The removal of the primary canines immediately creates space to align lateral incisors displaced due to crowding. The secondary outcome is the eruption of the 1st premolar is accelerated. Typically done age 8-9.
  1. Extraction of the 1st primary molar: The removal of the 1st primary molar accelerates premolar eruption ahead of the permanent canine. Usually the removal of the 1st primary molar is done 12 months the extraction of the primary canine.
  2. Extraction of 1st premolar: Once the 1st premolar erupts, it is extracted. The space created allows the canine to drop in distally.

 

Does it work?

Yes, if the outcome of crowding, maxillary alignment and duration are considered. There is a significant reduction in crowding through serial extractions, with the irregularity index reducing from 11.8 to 2.74 Yoshihara 1999. A long-term study over 16 years supports long term stability in irregularity reduction (2.4mm Peterson 2002). However when compared to late extractions there is no difference between occlusal outcomes (PAR mean difference 0.47 p=0.27 O’Shaughnessy 2011). Spontaneous alignment, achieves satisfactory root angulation of the maxillary canine and 2nd premolar without the use of active orthodontic appliances Persson 1989. The duration of active orthodontic treatment with a serial extraction pattern is significantly shorter than conventional late extractions, between 4-12 months shorter. O’Shaughnessy 2011 Little 1990.

However, there are a number of factors outside of crowding, maxillary alignment and duration of orthodontic appliances that need to be considered, and are described below. 

So, what’s not good about it?

 

The mandible. The mandible is less welcoming and predictable with serial extractions. Firstly the natural order of eruption favouring canine eruption before 1st premolar eruption (mandibular canine erupt age 9.5, mandibular 1st premolar erupt age 11 Berkovitz 2009). As a result serial extractions are less predictable in the mandible. Although there is good predictability in the maxillary arch of guided eruption of the 1st premolar  (maxillary premolars erupt age 10.5, maxillary canines erupt age 11.5 Berkovitz 2009). Mandibular spontaneous alignment through serial extractions, or “drift-o-dontics” (we very much wish we had invented this term) is not reliable in achieving root parallelism of the canine and 2nd premolar Persson 1989. As a result the need for active orthodontic appliances is likely in the mandible. Other concerns include increasing the overbite through loss of posterior teeth and counter-clockwise rotation, therefore making patients with deep bites not ideal candidates for serial extractions.

Timing is critical. In order to achieve guided eruption of the 1st premolar there is a window in which removal of the primary tooth achieves this, outside of the window however eruption slows down of the 1st premolar. The window is within 1 year of the  1st premolars natural eruption. However extraction 1.5 years or greater from the 1st premolars natural eruption time results in slowing down the eruption time of the 1st premolar Naragond 2017. As a result close monitoring is required during the age of 8 onwards, and are detailed below.

 

Passive Duration (Monitoring). Although the active treatment in serial extraction is less than late extractions, the average the total duration period for serial extractions is 6.8 years (6.2-7.8 years), with three quarters of the duration spent monitoring and between 12-20 months in active orthodontic appliances Little 1990 O’Shaughnessy 2011. As a comparison late extractions total duration was nearly one third of this (2.6 years).

 

Stability. Charles Tweed was a proponent of serial extractions and stated self alignment should result in improved stability, however Robert Little, arguably one of the greatest contributors to the understanding of stability in orthodontics, tested this idea of serial extraction and late extractions long term, and concluded there is no difference in stability, with both serial extraction patterns and late extractions showing a similar degree of relapse (Little’s index 4.39mm +/- 1.64). Little’s concluding comments on serial extractions were “Unfortunately…not the panacea for our post retention problems of relapse”.

New serial extraction protocol

A new protocol published by O’Shaughnessy sought to reduce the number of extractions needed from 12 to 8, and the approach took advantage of a natural eruption sequence, as well as manage an unfavourable eruption sequence.

  1. Protocol 1st Premolar likely erupt first
    1. Extract the primary canines
    2. First premolar extracted
  1. Protocol If canine likely erupt first
    1. Extract primary first molar
    2. Enucleate first premolar same time

Through this modified serial extraction pattern O’Shaughnessy was able to reduce the number of extractions patients required, yet still achieve reliable guided eruption of the 1st premolar.

Verdict

Serial extractions had once been a popular method of managing crowded cases, reducing the burden of treatment for patients and clinicians. However as advances in straightwire have increased the quality of clinical outcomes, expectations of both parents and clinicians have increased, resulting in a likelihood of orthodontic appliance therapy, even with serial extractions. The parent is now to consider, ‘8 extractions and quicker braces, or 4 extractions and longer braces’, which is unclear as to which option is better. Long-term data suggests no difference in occlusal outcomes or long term stability O’Shaughnessy 2011 Hakuri 1998 Peterson 2002.

Proffit’s comments sum up the positives of what we know about serial extraction as “an adjunct to later treatment and a means to make comprehensive treatment easier and often quicker”. However serial extraction are not more effective (based on occlusal outcomes) than late extractions, and if one considers monitoring duration, far less efficient.

Therefore, the decision for serial extractions lies with the significant variables; case selection, the need to complete active treatment quicker, acceptance of 4 additional extractions and the ability to attend for extended monitoring.

Contributions

Contents: Kerolos AlHakeem

Contents: James Andrews 

Edited/contents: Farooq Ahmed

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

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1 comment
  • If you use routinary serial extraction with right indications on a selected group of patients I declare with my clinical cases and with teaching of Dr Dale that you have many advantages (look at my book about serial extraction by title : guida all’occlusione edit Aries due Milano