IADR Abstract Archives
3D-Printed Model Shell Thickness Affects Accuracy of Thermoformed Orthodontic Aligners
Objectives: A digital dental model may be 3D printed as a shell of a desired thickness to support fabrication of thermoformed aligners. While thinner shells can reduce the time and cost of model printing, the shell must be of sufficient thickness to withstand the force of thermoforming. Otherwise, deformation of the model during thermoforming might affect the dimensional fidelity and clinical utility of the appliance. The objective of this study was to investigate the effect of model shell thickness on the dimensional deviation of thermoformed clear aligners.
Methods: Dental models with uniform thicknesses of 1.0, 1.5, 2.0, 2.5, and 3.0 mm, and a solid control were 3D printed (n=10/thickness). Baseline surface scans were recorded for each dental model prior to thermoforming an Essix 0.030” aligner on each arch. Once thermoformed, the aligners were removed from the models and another scan was taken. The intaglio surface of the aligner was filled with light-bodied impression material, which was then removed and scanned by the same method. Digital superimpositions compared the scans for a given model/aligner pair. Statistical analyses applied generalized linear models and post-hoc Tukey Contrasts.
Results: Dimensional deviation generally decreased as the shell thickness increased. Comparison of the pre- and post-thermoformed models showed the percent out of bounds of clinical acceptance (±0.25 mm) decreased from 63.86 ± 11.81% for the 1.0 mm group to below 1% for the remaining groups (p<0.001). The comparison of pre-thermoformed models and intaglio aligner casts showed the same trend, except that the 1.5 mm group had 7.07 ± 1.76% out of bounds (p<0.001).
Conclusions: 3D printed dental model shell thickness affects the dimensional fidelity of a thermoformed aligner under the conditions investigated. To ensure minimal dimensional deviation and promote clinical utility of the aligner, a shell thickness of at least 2.0 mm should be used.
Methods: Dental models with uniform thicknesses of 1.0, 1.5, 2.0, 2.5, and 3.0 mm, and a solid control were 3D printed (n=10/thickness). Baseline surface scans were recorded for each dental model prior to thermoforming an Essix 0.030” aligner on each arch. Once thermoformed, the aligners were removed from the models and another scan was taken. The intaglio surface of the aligner was filled with light-bodied impression material, which was then removed and scanned by the same method. Digital superimpositions compared the scans for a given model/aligner pair. Statistical analyses applied generalized linear models and post-hoc Tukey Contrasts.
Results: Dimensional deviation generally decreased as the shell thickness increased. Comparison of the pre- and post-thermoformed models showed the percent out of bounds of clinical acceptance (±0.25 mm) decreased from 63.86 ± 11.81% for the 1.0 mm group to below 1% for the remaining groups (p<0.001). The comparison of pre-thermoformed models and intaglio aligner casts showed the same trend, except that the 1.5 mm group had 7.07 ± 1.76% out of bounds (p<0.001).
Conclusions: 3D printed dental model shell thickness affects the dimensional fidelity of a thermoformed aligner under the conditions investigated. To ensure minimal dimensional deviation and promote clinical utility of the aligner, a shell thickness of at least 2.0 mm should be used.