Untreated Normal Occlusions Kept Changing From Age 13 to 62 in 50-Year Study

Edited by Orthotown staff

Arch dimensions in people who never received orthodontic treatment continued to change from adolescence into their sixties, according to a 50-year longitudinal study published Sept. 11 in Progress in Orthodontics.

Thirty orthodontically untreated subjects with normal occlusion, 11 men and 19 women, were examined at mean ages of 13, 16, 31, and 62. They were recruited through the public dental health care system.

Stone casts of the maxillary and mandibular arches at each time point were digitized with a high-resolution 3D scanner. Eleven variables were measured: overjet, overbite, intercanine width, intermolar width, arch depth, palatal height, curve of Spee, clinical crown height, arch length, space deficiency, and irregularity index. Changes across time points were analyzed with the Wilcoxon signed-rank test.

Sagittally, overjet held steady while arch depth decreased significantly in both arches. Vertically, overbite decreased significantly and clinical crown height increased significantly in both arches. Palatal height increased significantly through age 31, and the curve of Spee flattened significantly by age 16.

Transverse dimensions were largely stable. Maxillary and mandibular intermolar widths and maxillary intercanine width showed no significant change, but mandibular intercanine width decreased significantly.

Space showed the clearest trend. Arch length decreased significantly in both arches at every time point, accompanied by significant increases in space deficiency and in mandibular incisor irregularity throughout the observation period.

Anas Basim, Julia Naoumova, Klara Leffler, Kristina Johansson, Maurits Persson, and Nameer Al-Taai conducted the study at Mohammed Bin Rashid University in Dubai, the University of Gothenburg, the University of Copenhagen, and Umeå University. Naoumova is an associate editor of the journal and was excluded from the editorial evaluation and peer review of the manuscript.

The sample was 30 people, so the study’s value rests on the length of follow-up rather than its size. The authors concluded that occlusion remains dynamic throughout life and offered the measurements as reference data for diagnosis, treatment planning, and long-term retention strategies.

Sources:
Progress in Orthodontics, “Digital analysis of age-related dentoalveolar changes: a 50-year longitudinal study,” published Sept. 11, 2026: doi.org/10.1186/s40510-026-00643-0
PubMed record, PMID 42726424: pubmed.ncbi.nlm.nih.gov/42726424