Types of studies

Randomised controlled trials (RCTs) and controlled clinical trials (CCTs) of orthodontic treatments to correct deep bite and retroclined upper front teeth in children.

Types of participants

We planned to include trials that recruited participants (80% aged ≤ 16 years) receiving orthodontic treatment to correct deep bite and retroclined upper front teeth.

We planned to exclude trials of participants with a cleft lip or palate, or both, or other craniofacial deformity/syndrome, and trials in which participants had received surgical treatment for their Class II malocclusion.

Types of interventions

Active interventions: orthodontic braces (removable, fixed, functional) or head braces with or without extraction of permanent teeth.

Control: no treatment or delayed treatment.

Types of outcome measures

Electronic searches

Cochrane Oral Health’s Information Specialist conducted systematic searches in the following databases for RCTs and CCTs:

• Cochrane Oral Health's Trials Register (searched 13 November 2017) (see Appendix 1);

• Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 10) in the Cochrane Library (searched 13 November 2017) (see Appendix 2);

• MEDLINE Ovid (1946 to 13 November 2017) (see Appendix 3);

• Embase Ovid (1980 to 13 November 2017) (see Appendix 4).

No language, publication year or publication status restrictions were imposed.

Subject strategies were modelled on the search strategy designed for MEDLINE Ovid. Where appropriate, we combined these strategies with subject strategy adaptations of the highly sensitive search strategy designed by Cochrane for identifying RCTs and CCTs, as described in Chapter 6 of the Cochrane Handbook for Systematic Reviews of Interventions (Lefebvre 2011).

Searching other resources

The following resources were searched for ongoing trials:

• US National Institutes of Health Trials Register (ClinicalTrials.gov; searched 13 November 2017) (see Appendix 5);

• World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch; searched 13 November 2017) (see Appendix 6).

We planned to contact all first authors of trials in an attempt to identify any unpublished studies and clarify information about published trials (including missing data, method of randomisation, blinding and withdrawals). We intended to screen the references cited in the included studies for any further trials. We wrote to international researchers potentially involved in Class II division 2 malocclusion clinical trials in an attempt to identify unpublished/ongoing RCTs or CCTs.

A separate search for the adverse effects of interventions used was not performed.

Selection of studies

Two review authors (DTM and CMO or SC) independently scanned the titles and abstracts (when available) of all reports identified. When studies appeared to meet the inclusion criteria, or there was insufficient information in the title and abstract to make a decision, we obtained the full report and two review authors assessed it independently to establish whether the inclusion criteria were met or not. We planned to resolve any disagreements by discussion, consulting a third review author if necessary. We had planned to carry out 'Risk of bias' assessments of all studies meeting the inclusion criteria, to extract relevant data and to record all studies rejected at this or subsequent stages in a table of excluded studies, together with the reasons for exclusion. The review authors were not to be blinded to author(s), institution or site of publication.

Data extraction and management

For each trial, we planned to enter the following information on a customised data collection form.

• Year of publication, country of origin, setting and source of study funding.

• Details on the type of interventions including appliance type.

• Details of the participants including demographic characteristics, criteria for inclusion and exclusion, and sample size by study group.

• Details of the outcomes reported, including method of assessment and time intervals.

• Details of withdrawals by study group.

• Details of outcomes, including measures and timepoints.

Assessment of risk of bias in included studies

We planned for two review authors to independently assess random sequence generation, allocation concealment, blinding of participants, blinding of outcome assessors, incomplete outcome data, selective outcome reporting and 'other issues' for each study, using the 'Risk of bias' tool recommended for Cochrane Reviews (Higgins 2011). For blinding, we would have noted any outcomes where participants self‐assessed. We would have categorised the overall risk of bias for each study as follows.

Measures of treatment effect

We planned to calculate risk ratios, the number needed to treat for an additional beneficial/harmful outcome and corresponding 95% confidence intervals, for dichotomous data, and the mean difference and 95% confidence intervals for continuous data. We would have used the fixed‐effect model for all meta‐analyses unless there were more than three trials included, in which case we would have used a random‐effects model.

Assessment of heterogeneity

We planned to assess heterogeneity using Cochran's test and the I² statistic, which describes the percentage of total variation across studies that is due to heterogeneity rather than chance. We planned to assess clinical heterogeneity by examining the types of participants and interventions for all outcomes in each study.

Data synthesis

We planned to follow Cochrane statistical guidelines. We would have included only studies of similar comparisons reporting the same outcome measures in meta‐analyses. We planned to analyse the data using Review Manager software (RevMan 2014).

Subgroup analysis and investigation of heterogeneity

We planned a subgroup analysis based on the age (stage of dental development) at which treatment was undertaken.

Sensitivity analysis

We planned to conduct sensitivity analysis based on risk of bias (i.e. including studies at low risk of bias only).