Wan 2017.
| Study characteristics | ||
| Methods | 2‐arm parallel RCT | |
| Participants |
Number recruited: 20 Sex (M:F): 7:13 (HR group: 5 men, 5 women; VFR group: 2 men, 8 women) Mean age (years): HR group: 24.6 (SD 2.6); VFR group: 24.1 (SD 3.1) Inclusion criteria: had completed active orthodontic treatment Exclusion criteria: cleft lip or cleft palate, surgical correction of the jaws, dialects, hearing and speech disorders, temporomandibular joint dysfunction syndrome, < 18 years, suffering from serious periodontitis Setting: West China Hospital of Stomatology, Sichuan University, Chengdu, China |
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| Interventions |
2 types of removable retainer
Participants were instructed to wear the maxillary and mandibular retainers full‐time throughout the 3‐month period of the study, except while eating or brushing their teeth |
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| Outcomes | Patient satisfaction: assessment of speech sounds performed objectively using acoustic analysis:
Vowels were analysed in terms of 3 formant frequencies (F1, F2, and F3) Hz Voiceless fricatives were analysed in terms of upper boundary frequency (UBF) Hz Time points: before wearing, immediately after wearing, and at 24 hours, 1 week, 1 month and 3 months Changes in articulation not reported at T5, only number of sound distortions. |
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| Notes | ||
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | The study authors state they used “sortation randomization method”. Not sure what this means |
| Allocation concealment (selection bias) | Low risk | Allocation concealment was achieved with opaque sealed envelopes |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | Operators for clinical procedures and valuators for data collection or analysis were blinded |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | No participants were lost to follow‐up |
| Selective reporting (reporting bias) | High risk | Examples of some mean values for the acoustic analysis data were reported, but not all |
| Other bias | Low risk | No other biases identified |