Efficacy and predictability of maxillary and mandibular expansion with the Invisalign® system

BACKGROUND: The purpose of this study is to evaluate the efficacy and predictability of upper and lower orthodontic expansion with the Invisalign® system. MATERIAL AND METHODS: From a sample of 167 patients; 64 upper and 51 lower arches were randomly selected from patients who had been treated with plastic orthodontics (Invisalign® aligners, SmartTrack® material). Digital models were extracted at the beginning (ModT1) and at the end of treatment (ModT2) as well as the final ClinCheck® (CkT2). The canine, premolar and molar width was measured at the gingival and cuspid level of both arches, as well as the inclination of the upper first molar. Likewise, both arches were divided regarding the planned expansion at the level of the first molar into mild, moderate and severe. RESULTS: The efficacy of expansion in the upper and lower arches showed a statistically significant difference (p<0.00005). During the measurements of predictability, around 98-100% was achieved at the coronal level and between 85-90% at the gingival level. Analyzing predictability regarding to the magnitude of expansion, superior and inferior moderate expansion, both gingival and cuspid, presented higher values. CONCLUSIONS: The Invisalign® system aligners (SmartTrack® material), proved to be a positive alternative for expansion movement offering high degree of predictability, both in the upper and lower arches. As a result, the most predictable level of expansion was moderate, having being the lower arch more foreseeable at the gingival level than the upper arch. Key words:Predictability, Efficacy, Expansion, Aligner, Invisalign®.