Open Access Open Badges Study protocol

Should I eXtract Every Six dental trial (SIXES): study protocol for a randomized controlled trial

Nicola Innes1*, Felicity Borrie1, David Bearn1, Dafydd Evans1, Petra Rauchhaus2, Steve McSwiggan2, Lyndie Foster Page3 and Fiona Hogarth2

Author Affiliations

1 Dundee Dental Hospital and School, Park Place, University of Dundee, DD1 4HN, Dundee, UK

2 Tayside Medical Sciences Centre, George Pirie Way, Ninewells Hospital, DD1 9SY, Dundee, UK

3 Department of Oral Rehabilitation, Faculty of Dentistry, Sir John Walsh Institute, University of Otago, Dunedin, New Zealand

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Trials 2013, 14:59  doi:10.1186/1745-6215-14-59

Published: 27 February 2013



Extraction of lower first permanent molars in children is common. There is uncertainty among clinicians as to whether a ‘compensating extraction’ (removal of the upper first permanent molar to prevent it over erupting) is necessary despite current guidelines recommending this. As a result, unnecessary dental extractions may be carried out or children may be failing to receive extractions required to achieve optimal long-term oral health. In addition, the decision to extract fewer or more teeth affects management options (local anesthetic injections alone, inhalation sedation or general anesthesia) needed to support the child with the surgical procedure(s).

The SIXES (Should I eXtract Every Six) dental trial investigates clinical effectiveness and quality of life for conventional treatment (following the guideline of compensation extraction of the upper first permanent molar) compared with the alternative intervention (removal of lower first permanent molars but no extraction of the upper).


This is a multicenter, two-arm parallel group randomized clinical trial. Allocation will be web-based randomization. Practitioners in primary and secondary care settings, reflecting the points of presentation and treatment of eligible patients, will recruit 400 children, aged 7 to 11 years requiring extraction of lower first permanent molars but who have upper first permanent molars of good prognosis. Baseline measures (prior to treatment) and outcome data (at one and five years, or when the patient reaches 14 years of age) will be assessed through study models and child/parent questionnaires.

The primary outcome measure is degree of tipping of the lower second permanent molar, (favorable outcome is tipping less than 15°).

The secondary outcomes are type of anesthetic/sedation used, residual spacing (between lower second premolar and second permanent molar), orthodontic treatment requirement, quality of life, and over-eruption in the intervention group. Assessors will be blinded where possible.


SIXES dental trial investigates whether compensating extraction of upper first permanent molars should be carried out following loss of lower first permanent molars. Currently dentists and orthodontists face a dilemma in clinical decision-making, relying on the lowest level of evidence - expert opinion. SIXES will provide evidence to support decision-making and inform practices and may result in reduced tooth extractions.

Trial registration

Clinical Identifier: NCT01591265

First permanent molar; Compensating extraction; Orthodontics; Pediatric dentistry; Primary care; Randomized control trial; Dental; Oral health-related quality of life