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Updated: Oct 23, 2025
Author Spotlight: 3D Movement Assessment of Maxillary Posterior Teeth in Clear Aligner Treatment
Published on: February 23, 2024
Measuring tooth movement with treatment using the Dahl principle: An observational study
Kritesh Bhai1, Roy Judge2, Jaafar Abduo3
1Past Prosthodontic Postgraduate student, Restorative Dentistry Department, Melbourne Dental School, The University of Melbourne, Melbourne, Australia.
Statement Of Problem:
Research on the quantification of 3-dimensional tooth movements in patients undergoing treatment using the Dahl principle is lacking.
Purpose:
The purpose of this observational clinical study was to measure the magnitude, direction, duration, and rate of tooth movement occurring in patients to reestablish tooth contact and create restorative space.
Material And Methods:
A total of 104 paired preoperative and postoperative physical and virtual casts from 26 patients were obtained. Commencement and completion dates were recorded to calculate movement duration to reestablish occlusion. Dental casts were digitized, and the 3-dimensional digital casts obtained were superimposed via a surface matching and analysis software program by using the global registration function. Color maps were used to visualize direction, and the annotation feature quantified magnitude of tooth movement in millimeters when specific reference points were selected. Teeth within the arch were categorized as per their location to evaluate their impact on occlusal reestablishment. The average rate of movement was determined by time taken for extrusive and intrusive movements over the treatment duration. Post hoc Tukey tests were applied if a significant difference was present in the magnitude of movement between different tooth categories.
Results:
All participants showed evidence of tooth movement during treatment. Duration of occlusal reestablishment ranged from 3.9 to 28.2 months, with more posterior tooth extrusive movements (56.9%) than anterior tooth intrusive (43.1%) movements occurring. A comparison of magnitude of extrusive or intrusive movement between categories (molar-anterior, premolar-anterior, and premolar-molar) showed that premolar and molar extrusive movements and anterior intrusive movements were significantly different (P<.001). The amount of buccal and lingual movement for molars and premolars was similar. Anterior teeth demonstrated more buccal than lingual movements. All teeth showed more mesial than distal movements. The extrusive and intrusive movement rate was 0.13 and 0.11 mm/mo, respectively.
Conclusions:
Tooth movement occurred in patients regardless of age and sex. The results of this study indicated that tooth movements have a 3-dimensional nature. Occlusal reestablishment mainly occurred via a combination of extrusive and intrusive movements. The study further highlighted the advantages of digital technology such as surface scanners and 3-dimensional software programs that can be used to quantify change in patients undergoing treatment.
