Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment

Abstract

The purpose of this study was to evaluate the treatment and posttreatment changes in the facial and dental parameters in two groups of patients with Class II, Division 1 malocclusions. In one group (n = 46), the patients were treated with a nonextraction approach, whereas in the second group (n = 45), the treatment included the extraction of four first premolars. The treatment groups were compared with matched untreated normals (n = 35) from the Iowa Growth Study. Lateral cephalograms and dental casts were evaluated at three stages: pretreatment, posttreatment, and approximately 2 years after treatment. Student's t tests were used to compare the extraction and nonextraction groups. Significance was predetermined at p < or = 0.05. The cephalometric findings indicate that before treatment, the subjects treated with four first premolar extractions had more protrusive upper and lower lips and a larger tooth size-arch length discrepancy. After treatment the upper and lower lips were more retrusive in the extraction groups, and more protrusive in the nonextraction groups. The extraction groups tended to have straighter faces and slightly more upright maxillary and mandibular incisors, whereas the nonextraction groups had the opposite tendencies. The average soft tissue and skeletal measurements for both groups were close to, but on opposite sides of, the corresponding averages derived from the Iowa normative standards. The findings from the dental arch measurements indicate that after treatment both the extraction and nonextraction groups experienced an increase in tooth size-arch length discrepancy and a reduction in arch length. In general, extractions did not significantly alter the direction of the overall posttreatment trends. Furthermore, the trends in the posttreatment changes were similar in male and female patients, as well as in the maxillary and mandibular arches. The current findings suggest that the extraction/nonextraction decision, if based on sound diagnostic criteria, does not have a systematic detrimental effect on the facial profile. But clinicians should be aware of the trends introduced by the two treatment modalities to avoid accentuating undesirable profile characteristics.