stability of changes in mandibular intermolar and intercuspid distances following orthodontic treatment

background: the aim of this study was to determine the pattern and amount of change exhibited in mandibular intercanine and intermolar width during treatment and assessing its stability1-3 years post-retention. materials and methods: the material consisted of 70 cases of which 20 cases were treated without extraction and 30 cases were treated with extraction, which were compared with 20 untreated cases which served as a control group. a series of three measurements were made for each case of the treated group: at the beginning of treatment, end of active treatment and 1-3 years post-retention; and for the control group: at 12, 15 and 18 years of age. the wilcoxon signed ranks test was used to evaluate treatment changes in each group. the kruskal-wallis h test was used to compare the treatment changes between the 3 groups (α = 0.05). spss 16 software (spss inc., chicago, il, usa) was used to evaluate the data. results: mean changes of intercanine width for three groups was −0.5 mm for control group, −0.26 mm for non-extraction group and +0.18 mm for extraction group. intermolar width of the extraction group decreased signifi cantly during treatment. in contrast to the extraction group, the control and non-extraction groups both demonstrated an increase in mean intermolar width which was 0.66 mm and 0.91 mm respectively. conclusion: it was concluded that although mean changes of intercanine and intermolar width were statistically signifi cant but they were not perceptible clinically. key words: intercanine width, intermolar width, mandibular, orthodontic