Incisor retraction may result in lip retraction, interlabial gap closure and increase of the nasolabial angle but a clear consensus on the effect of incisor retraction on facial aesthetics has not yet been achieved. Despite current evidence being weak, it seems to indicate that in a well-managed orthodontic case, with or without extractions, the soft-tissue and facial aesthetic changes are generally favourable or clinically insignificant.

Objectives: To compare the immediate three‐dimensional (3D) perioral soft‐tissue changes and impact on speech induced by clear aligners and fixed appliances.Materials and Methods: In this repeated‐measure experimental study, stereophotogrammetric 3D photographs of 40 participants were recorded before and immediately after the introduction of clear aligners and fixed appliances. The 3D surface meshes were registered to quantify changes in the direction and magnitude of nine soft tissue landmarks located on the upper and lower lips. Self‐reported speech disturbance was evaluated using a questionnaire. Data were analysed using repeated‐measures analysis of variance.Results: In the vertical plane, the clear aligners induced inferior displacement (range 0.4‐1.5 mm) for all nine landmarks (P < .01), whereas fixed appliances induced inferior displacement only of A‐point (0.4 ± 0.9 mm), right crista philtri (0.5 ± 1.1 mm) and left crista philtri (0.7 ± 1.1 mm). The clear aligners induced greater vertical changes than fixed appliances for all landmarks (P < .05). In the sagittal plane, both clear aligners and fixed appliances slightly advanced all perioral landmarks, except subnasale. Fixed appliances caused greater changes than clear aligners for right cheilion (+0.8 mm), left cheilion (+0.8 mm) and labrale inferius (+0.9 mm) (P < .01). Both orthodontic appliances had a significant self‐perceived effect on speech, with clear aligners affecting speech to a greater degree.Conclusion: Clear aligners and fixed appliances produced immediate effects on perioral soft tissues, which are most evident in the vertical plane for clear aligners, and in the sagittal plane for fixed appliances. Speech was affected by both appliances.

Although dental practitioners orthodontically move teeth on a daily basis, questions persist regarding the complex biological mechanisms involved. The importance of knowledge about the mechanobiology of tooth movement is ever‐increasing as orthodontics is undergoing a shift from a focus on ‘biomechanics’ to ‘biology’. As in other areas of healthcare, practitioners aspire to provide individualised treatment, as well as potentially accelerate tooth movement and attenuate adverse effects. In vitro and in vivo models of tooth movement research, including those which have been conducted in New Zealand, will be described, with a vision toward future directions.