According to a study published in the American Journal of Orthodontics and Dentofacial Orthopedics, incisor crowding stability is similarly achieved with extraction and nonextraction of premolars.
A.E. Erdinc and colleagues at the University of Oklahoma evaluated dental casts and cephalometric records of 98 patients before treatment (T1), at post-treatment (T2), and at postretention (T3). Half of the patients had been treated with extractions, and half were treated nonextraction.
The researchers found that irregularity, as measured by the irregularity index, decreased 5.51 mm in the extraction group and 2.38 mm in the nonextraction group. Mandibular incisor irregularity increased 0.97 mm in the extraction group and 0.99 mm in the nonextraction group, respectively, in the postretention period. They also reported that maxillary incisor irregularity relapse was smaller than mandibular incisor relapse for both groups. Intercanine width expanded during treatment. At T3, mandibular intercanine width decreased in both groups, but the differences were not statistically significant.
At T3, intermolar width was stable, arch depth decreased, overbite and overjet slightly increased, SN mandibular plane angle decreased, and incisor positions in both groups tended to return to T1 values. With the exception of the interincisal angle, no statistically significant differences were recorded between the extraction and nonextraction groups from T2 to T3.
The researchers concluded that no statistically significant correlations were found between any variables studied and mandibular incisor irregularity at T1, T2, and T3.
[www.newsrx.com, August 21, 2006]