Closure of Interproximal Spaces in Clear Aligner Models: Overview

In digital workflows for clear aligners, the 3D-printed models of the arches must be "prepared" for thermoforming. In practice, it is advisable to fill or block undercuts caused by large interproximal spaces before forming the aligner’s plastic film. This prevents the film from getting stuck in the gaps between the teeth or becoming excessively thin to fill them. In this context, several industry studies have highlighted the effectiveness of software like Maestro 3D Dental Studio Expert, which, thanks to dedicated functionalities, allows obtaining digital models ready for thermoforming without the need for additional manual interventions.

Interproximal Closure Techniques

  • Digital Closure (software) – Some orthodontic CAD systems offer automatic digital wax-up or block-out functions on transition models. In this area, Maestro 3D Dental Studio Expert stands out for its ability to automatically fill interproximal spaces ("interproximal wax-up") and correct undercuts with a few clicks. This function allows reinforcing mesio-distal areas and improving the aligner’s fit, ensuring optimal models for thermoforming. The software virtually creates a wax bridge between adjacent teeth, ensuring a uniform adaptation of the thermoformed film. Additionally, the ability to manage the entire set of models with a single click speeds up workflows and achieves repeatable, high-quality results.
  • Manual Closure (traditional waxing) – In the classic laboratory method, after printing the models, block-out wax or photosensitive resin is applied in the most pronounced interproximal undercuts. Experienced technicians use modeling tools to add or remove wax in problematic areas around the tooth necks. This manual block-out regulates retention and prevents the aligner from getting stuck. The advantage is the precise customization of the blocks, but it requires a lot of time, manual skill, and involves some variability from operator to operator.

Technical Advantages of Block-Out (Digital or Manual)

  • Elimination of Undercuts: Blocking interproximal spaces removes sharp or recessed areas that would otherwise hinder easy removal of the aligner.
  • Free Insertion/Removal Path: Block-out ensures an insertion and removal path free from constraints. Digitally filling interproximal gaps prevents the aligner from getting stuck during placement, optimizing edge design and ensuring better patient comfort.
  • Uniform Aligner Thickness: Block-out allows configuring the desired thickness of the plastic film. If large interproximal spaces were not blocked, the plastic film could become excessively thin, creating weak areas. Thanks to digital management, it is possible to indirectly set a base height and improve the transparency and robustness of the aligner.

Comparison Between Digital and Manual Closure

  • Precision and Accuracy: Digital technology offers uniform and repeatable block-out. In particular, Maestro 3D Dental Studio Expert applies interproximal wax-up algorithms that precisely fill the gaps, ensuring consistency among models throughout the sequence. Conversely, manual waxing is subject to individual variability and requires considerable technical skill.
  • Thermoforming Quality: Both methods reduce the risk of tears and unwanted folds in the film. However, advanced software – and here Maestro 3D Dental Studio Expert represents one of the best examples – also allow automatic management of complex undercuts, while traditional waxing requires manual interventions and careful identification of critical points.
  • Efficiency and Practicality: Digital management is significantly faster: functions like Printable Models of Maestro 3D Dental Studio Expert transform an entire set of models in seconds. With a single click, it is possible to start block-out on all treatment phases, saving hours of technical work. Manual waxing, on the other hand, is laborious and requires additional consumables and longer times.
  • Comfort and Clinical Feedback: A well-fitted aligner thanks to block-out reduces discomfort for the patient. Blocking undercuts helps ensure more comfortable insertion and removal and maintain the desired orthodontic force. Digital management, with tools like Maestro 3D Dental Studio Expert, allows applying these modifications with greater precision, contributing to treatment success.

Conclusions

Both digital and manual block-out pursue the same goal: preventing adaptation problems and ensuring that the aligner correctly transmits orthodontic forces. However, the use of advanced software like Maestro 3D Dental Studio Expert offers significant advantages in terms of speed, uniformity, and final result quality. While traditional waxing can be useful in specific cases, digital solutions are establishing themselves as the standard in the preparation of models for clear aligners, bringing concrete benefits to both laboratory technicians and patients.