Anterior tooth alignment and arch dimensions changes: 37-year follow-up in patients treated with and without premolar extraction

Association between arch width changes and long-term stability 20 years after orthodontic treatment with and without extractions

“…However, different dental arches show different levels of stability, as demonstrated in previous studies. [1][2][3][4][5][6][7] It had been claimed that a longer period of posttreatment time (more than 10 years) shows greater instability. 2 According to past research, biological or treatmentrelated factors, such as periodontal tissue, muscular imbalance, jaw growth, mandibular rotation, mandibular intercanine width, and mandibular incisor position, can have an impact on long-term stability.…”

“…A recent study by Cotrin et al showed there was no difference in the long-term change in anterior alignment and transverse arch dimensions between patients treated with and without extractions; however, there was clinically unsatisfactory Little's irregularity index measures in the long-term period in both arches (.3.5 mm). 6 In the current literature, no predictors of long-term stability after orthodontic treatment have been identified. This study aimed to investigate the effect of arch widths and their changes during treatment on the longterm stability of dental arches.…”

Authors’ response

“…This result was discussed in the article, in which one of the causes for this improvement may have been due to dental attrition, but also studies with shorter follow-up indicate that there is an improvement in the positioning of marginal ridges after treatment. 6,7 This paper is part of a broad study, which also gave rise to another publication, 8 in which crowding and dental arch dimensions were assessed. In this study, 8 we also discussed the extraction decision, especially in patients with different malocclusions.…”

“…6,7 This paper is part of a broad study, which also gave rise to another publication, 8 in which crowding and dental arch dimensions were assessed. In this study, 8 we also discussed the extraction decision, especially in patients with different malocclusions. Naveda et al 9 recently showed that the actual extraction decision is determined by greater dental and labial protrusion, unlike extraction decisions in patients treated in the 1970s, commonly based on the dogma of the mandibular incisors' final position and to finalize in a Class I molar relationship.…”

Comparison of the tooth alignment stability using canine-to-canine retainers bonded in two different forms

“…The sample size calculation was based on an alpha significance level of 5% and 80% test power to detect a mean difference of 0.85 mm, with a standard deviation of 0.89 for the Little irregularity index. 29 Thus, the sample size calculation showed the need for 16 subjects in each group.…”