Related Experiment Video
Updated: Jan 6, 2026
Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment
Published on: February 23, 2024
The effect of clear aligners with posterior occlusal attachments on daytime masticatory muscle activity
Allen Hu1, Fiona Firth1, Hamza Bennani1
1Discipline of Orthodontics, Faculty of Dentistry, University of Otago, Dunedin, New Zealand.
Introduction:
Bite-raising posterior occlusal attachments are integrated into clear aligner treatments to prevent posterior extrusion and promote intrusion by enhancing masticatory muscle activity (MMA) and occlusal forces. However, their effect remains anecdotal. The study aimed to (1) investigate the effect of passive aligners with posterior occlusal attachments on daily MMA compared with control aligners, and (2) determine if bite raising induces transient temporomandibular disorder (TMD); explore whether any early intrusive effects on teeth could be detected.
Methods:
Twelve volunteers participated in a randomized, crossover experiment. MMA recordings (amplitude, duration, frequency, and duty time) were collected using a wearable electromyography device over 5-hour sessions in natural settings while wearing (1) no aligners, (2) passive aligners for 8 days, and (3) aligners with occlusal attachments for 8 days. Participants' freeway space (FWS), occlusal discomfort, perceived stress levels, TMD symptoms, and intraoral scans were monitored. Data were analyzed with linear mixed modeling.
Results:
Bite-raising attachments increased contraction episodes per hour by 55% (95% confidence interval, 12%-67%) from days 1 to 8, but not compared with baseline. Both aligners significantly increased FWS, with bite-raising aligners showing a 114% increase (95% confidence interval, 85%-144%). Significant occlusal discomfort was reported in the first 3 days for both aligner types. No participants were diagnosed with TMD. No discernible intrusion was detected on serial intraoral scans.
Conclusions:
Aligners encroaching into the FWS transiently increase MMA in healthy young adults, despite adaptation and diminishing discomfort. However, we found no convincing evidence to support the hypothesis that occlusal attachments contribute to vertical control or enable intrusion in the short term. More research is needed to assess long-term effects and determine whether intrusions become clinically relevant.
