Directly printed aligners showed a more stable OPG response in a pilot study
A pilot study in only eight adult patients measured significantly lower RANKL at weeks 4 and 6 and consistently higher OPG with directly printed clear aligners (p < 0.05). Given the sample size, the finding needs confirmation in larger groups.
Two kinds of aligner, two biological responses
Orthodontic tooth movement rests on remodelling of alveolar bone, and the RANKL/OPG axis governs it. Clear aligners are made in two ways today, thermoforming over a model and direct 3D printing, which differ in material and in how force is delivered. The team around Lakshmanan asked whether the biological response differs as well.
In a prospective randomised pilot study, eight healthy adults aged 18 to 40 were randomly allocated to thermoformed or directly printed aligners. Gingival crevicular fluid and unstimulated saliva were collected at baseline and at weeks 1, 2, 3, 4 and 6, and RANKL and OPG were measured by ELISA.
The curves diverged. With thermoformed aligners, RANKL in crevicular fluid peaked at week 3 and then fell by week 6. With directly printed ones the decline was gradual, with significantly lower RANKL at weeks 4 and 6 (p < 0.05). OPG in the direct-print group was consistently higher at every time point, in saliva and in crevicular fluid alike (p < 0.05). The authors describe that pattern as a trend towards a more stable response weighted towards OPG.
A second finding concerns the sampling method: salivary OPG correlated strongly with that from crevicular fluid at baseline and at weeks 3 and 6, while correlations for RANKL were higher in later phases of treatment. That makes saliva a usable non-invasive source of biomarkers.
Limitations
Eight participants is pilot-level evidence, and the authors themselves ask for caution in interpretation and for larger longitudinal studies. Biomarkers of bone remodelling were measured, not a clinical outcome; neither the speed nor the quality of tooth movement was compared.
For the practice
- The finding does not change the choice of aligner for a patient: the difference was measured in biomarkers, not in the clinical outcome of treatment.
- To a patient who asks whether a printed aligner is better, the honest answer is that so far there is a difference in biological markers without a demonstrated clinical advantage.
- If you follow patients at periodontal risk, the finding that saliva reflects crevicular fluid OPG opens up simpler sampling in future monitoring protocols.