Work

Comparison of the Inclination Changes of the Upper First Molars Following Treatment with Two Types of Hyrax Tooth-Borne Expanders: 3D-Printed and Laboratory-Fabricated

Year: 2026

Type: article

Abstract: Background: Rapid maxillary expansion (RME) is widely utilized to correct transverse maxillary deficiency in growing patients, yet traditional tooth-borne appliances frequently induce undesirable dental tipping and anchorage loss. Methods: A two-year non-randomized prospective clinical study evaluated and compared the dentoalveolar changes in the upper first molars following RME using two tooth-borne expanders: a conventional Hyrax expander (CHE; n = 47) and a digitally designed metal-printed tooth-borne expander (DDMPTBE; n = 35). Measurements of jugal width and upper first molar inclinations were performed using cone-beam computed tomography (CBCT) images before treatment and after a three-month retention period. Results: Analysis of covariance (ANCOVA) controlling for baseline variables demonstrated that both appliances achieved comparable, statistically significant increases in jugal width. However, significant differences were observed in molar inclination changes: the CHE group experienced a greater increase in buccal inclination (unadjusted mean (Standard deviation–SD) increase of 6.56° for the left molar and 5.96° for the right molar; adjusted mean (Estimated marginal means–EMM) increases of 7.58° for the left molar and 6.14° for the right molar), whereas the DDMPTBE group exhibited less change in buccal inclination (unadjusted mean (SD) increase of 1.43° for the left molar and 0.32° for the right molar; adjusted mean (EMM) increases of 0.08° for the left molar and 0.07° for the right molar). Conclusions: Although both expanders effectively increase the jugal width, the findings demonstrate a significant association between appliance type and molar inclination changes, with the CHE linked to increased buccal tipping of the anchorage molars, whereas the DDMPTBE is associated with smaller inclination changes.

Source: Applied Sciences

DOI: 10.3390/app162110980

Authors: Mirela Georgieva, Emanuel Emiliyanov, Anzhelina Krasteva, Silviya Krasteva

Institutions: Medical University of Sofia, Medical University Plovdiv

Language: English

Topic: Orthodontics and Dentofacial Orthopedics

Subfield: Orthodontics

Field: Dentistry

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $2,896