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A Prospective Clinical Trial of Arch Width Changes Evaluated through Dental Casts in Consecutively Treated Non-extraction and Extraction Cases

Marcio Rodrigues de Almeida*,Renata Rodrigues de Almeida-Pedrin,Renato Rodrigues de Almeida,Carlos Flores-Mir

Objective: To compare the dental arch width changes in consecutively treated extraction and non-extraction Class I patients.
Materials and methods: Anterior and posterior arch widths of the maxillary and mandibular arches of 21 patients treated by 4 first-premolar extraction and 20 patients treated without extractions were measured on study models using a digital caliper.The initial mean ages were 13.4 ± 1.02 years for the extraction group and 13.1 ± 1.7 years for the non-extraction group. Mean treatment time was 2.7 ± 0.6 years for the extraction group and 2.4 ± 1.0 years for the non-extraction group. The maxillary and mandibular crowding were −5.2 ± 2.8 and −5.9 ± 3.1 mm for the extraction group and −4.1 ± 2.7 and −3.3 ± 2.5 mm for the non-extraction group, respectively. To compare the changes between groups, independent samples t-tests were performed.
Results: At the end of treatment, no differences were found between the groups in maxillary intercanine width. The maxillary and mandibular intermolar widths decreased significantly for the extraction group (-0.74mm and -1.59mm, respectively) compared with non-extraction (1.30mm and 0.37mm, respectively). The mandibular intercanine width increased significantly for the extraction group (1.48mm) compared with non-extraction group (0.52mm).
Conclusions: Orthodontic treatment with extractions of four first premolarsin Class I patients provided no significant difference in maxillary intercanine width after treatment compared to nonextraction. However, nonextraction treatment produced significantly larger values in maxillary and mandibular intermolar widths than that in the extraction group.