Non-extraction Treatment in Mixed Dentition Patients: Rationale & Long-term Stability

Orthodontists make every possible effort to create full smiles, and non-extraction treatments are becoming increasingly popular among patients. However, dimensional changes of the dental arch tend to relapse, and this instability is one of the main reasons why non-extraction treatment remains an open question. Key factors in choosing between extraction and non-extraction are mainly the amount of crowding and aesthetic concerns. Therefore, non-extraction treatment is indicated in patients with moderate crowding who may benefit from increased lip support. This presentation focuses on the rationale of non-extraction treatment and its long-term stability. Data was collected from dental models and lateral cephalograms of patients treated consecutively with a non-extraction approach, Transpalatal arch (TPA) in the upper arch and Lip Bumper (LB) in the lower arch, during the mixed dentition phase followed by fixed appliances in the permanent dentition and recalled after an average follow-up of 6 years. Arch-widths, perimeters, and lengths, as well as crowding and incisor proclination were assessed and compared with those of a matched untreated control sample, at the start of treatment, after non-extraction treatment, after fixed appliance treatment and at the follow-up. In the treated group, after the non-extraction treatment phase with TPA and LB, the arch widths and perimeters increased significantly while crowding was significantly reduced in both the upper (90%) and lower (80%) arch. After the fixed appliance treatment, only small increases in arch widths and perimeters were reported, and crowding was completely corrected in both upper (10%) and lower (20%) arch. Arch length increases and incisor proclination did not contribute to the crowding correction. At the follow-up, arch widths and perimeters remained mainly stable, showing only a slight decrease associated with a small increase in crowding, a maximum of 0.5-mm, considered clinically irrelevant. The best predictors of relapse and long-term stability were also evaluated. The best predictor of relapse was the amount of crowding before treatment, confirming the need to avoid non-extraction treatment in patients with severe crowding The best predictors of stability were the increase in intermolar and interpremolar widths, suggesting that the best way to gain space in mixed dentition is by transversal arch expansion.