The debate between extraction and non-extraction orthodontic treatment is long running. Proponents of a non-extraction approach main argument is that tooth extraction would lead to an imbalance in facial harmony and abnormal function due to the change in arch width and form. While those favouring extraction argue that extractions avoid later relapse.

The aim of this review was to compare four first premolar extraction and non-extraction treatment effects on orthodontic outcomes.

Methods

A protocol was registered on the Prospero database. Searches were conducted in the Cochrane Library, DOSS (Dental and Oral Sciences Source) , Medline/PubMed, Scopus, VHL Regional Portal, Web of Science, ClinicalTrials.gov, Goggle Scholar and OpenGrey databases with no date or language restrictions. Study selection and data abstraction was undertaken by two reviewers in duplicate. The ROBINS-I tool was used to assess the quality of the observational with the Cochrane RoB 2 tool being used for randomized trials.

Results

• 30 studies (29 retrospective, 1 randomised controlled trial [RCT]) were included.
• The 1 RCT was considered to be at high risk of bias, 23 of the retrospective studies were assessed as being at high risk of bias and 6 of moderate risk.
• Meta-analyses and sensitivity analyses were conducted for a range of outcomes with contributions from 24 studies (see table below). Statistically significant findings included: –
  • An increase in in mandibular intercanine width was seen in the non-extraction group.
  • A decrease in maxillary and mandibular intermolar width with four first premolar extraction.
  • A shorter treatment duration was noted in the non-extraction group compared with the extraction group.

Variable	Mean difference (95%CI)	Mean difference (95%CI) – Sensitivity analysis
Maxillary intercanine width	0.02 (-0.38 to 0.43)	-0.06 (-0.53 to 0.41)
Mandibular intercanine width	0.68 (0.36 to 0.99) *	0.61 (0.17 to 1.04) *
Maxillary intermolar width	-2.03 (-2.97 to -1.09) *	-1.94 (-3.61 to -0.71) *
Mandibular intermolar width	-2.00 (-2.71 to -1.30) *	-2.09 (-3.17 to -1.02) *
Treatment duration	0.36 (0.10 to 0.62) *	0.38 (0.06 to 0.69) *
US weighted PAR score	0.33 (-0.21 to 0.87)	N/A
Aesthetic score	-0.09 (-0.24 to 0.05)	-0.11 (-0.28 to 0.06)
Maxillary intercanine width/smile width	0.01 (-0.00 to 0.02)	0.01 (-0.00 to 0.02)
Visible dentition width/smile width	-0.00 (-0.01 to 0.01)	-0.00 (-0.02 to 0.02)
Maxillary intercanine width/visible dentition width	0.00 (-0.02 to 0.02)	0.00 (-0.02 to 0.03)

*Statistically significant

Conclusions

The authors concluded: –

Four first premolar extraction results in maxillary and mandibular inter-first molar width decrease and retraction of upper/lower lips. Non-extraction treatment results in mandibular intercanine width increase and shorter treatment duration. There was no significant difference between the two groups regarding maxillary intercanine width, US PAR score, and posttreatment smile aesthetics. Further high-quality focused research is recommended.

Comments

This recent review of extraction v non-extraction orthodontic treatment followed a preregistered protocol searching a good range of databases and included 30 individual studies. A previous review of extraction/non-extraction treatments we reported (Dental Elf – 12^th Mar 2018) included 52 studies. However, with both these reviews the quality of the primary studies very poor with all the studies included in bother reviews being considered to be at high risk of bias. Consequently, it is very difficult to draw any meaningful evidence from the available literature which perhaps goes someway to explaining the long-standing debate on this topic.

Earlier this year a Benson et al published a scoping review of this topic (Dental Elf – 7^th July 2023) which further highlighted the limited low-quality evidence available. Benson et al made available a study protocol (https://doi.org/10.17605/OSF.IO/CQ49Y) to help reduce methodological differences in studies on this topic which would assist future meta-analyses and increase the generalisability of the findings.

Links

Primary Paper

Elias KG, Sivamurthy G, Bearn DR. Extraction vs nonextraction orthodontic treatment: a systematic review and meta-analysis. Angle Orthod. 2023 Oct 30. doi: 10.2319/021123-98.1. Epub ahead of print. PMID: 37899069.

Review protocol in PROSPERO

Other references

Dental Elf – 12^th Mar 2018

Fixed appliance orthodontics: extraction or non-extraction and soft tissue changes

Dental Elf – 7^th July 2023

Extraction vs non-extraction of premolars for orthodontic treatment