Aims and objectives: The aim and objective of this observational study was to evaluate the dental arch width changes in Angle Class I malocclusion of all four first premolar extraction cases treated with MBT PEA mechanotherapy. Materials and Methods: The study was performed on pre treatment and post treatment study models of 20 subjects.   The intercanine   arch width measurements were measured using a digital calliper of 0.01 accuracy.  Paired samples t–test was used to evaluate the treatment changes within each group.  Results: Mandibular intercanine widths   were increased but the values were statistically insignificant.  There was a statistically significant increase in Maxillary intercanine arch width from 35.08+ 3.08 mm to 36.573+ 2.26 mm (t = –2.501 P <0.02)  Conclusions:  The intercanine distance increased in maxillary arch   and the difference was statistically significant.