Direct to Print Aligners, are they really different to normal aligners? 8 MINUTE SUMMARY Simon Graf

orthodontics In summary

Join me for a summary of direct to print aligners. This lecture explores the application of a relatively new resin material which can be used for aligner fabrication, without the need of a 3D printed model. The lecture was given by Simon Graf who expertly compared the differences between conventional and direct to print aligners, as well as the clinical application of specific features of direct to print aligners.

Limitations of current aligner material:

1. Only small undercuts

2. Limited aligner thickness to sheet thickness / no selective thickness

3. During the manufacturing process material can get thinner or thicker depending on heat distribution and stretch, 54% change in thickness of the aligner Lee 2022

4. Plastic and resin waste, (122 million aligners and models in 2022 Slaymaker 2024)

Advantages of direct to print aligners

· Select thickness, 0.5-0.7mm, conventional aligners 0.75mm+

· Gingival margin

· Dentist in charge of design, not company

Manufacturing steps of Direct to Print aligners (Tera Harz ‘Graphy’)

1. 3D printing of resin aligner

2. Centrifuge: Spin remove excess resin

3. UV Light cure in Nitrogen chamber

4. Washed twice, hot distilled water

Characteristics of Direct to print aligners

· Greater accuracy: (Zendura, Essix Ace and DTP were compared and DTP were 20-30% more accurate Koenig 2022)

· Less with DTP (Hertan 2022)

o DTP 50% less still (2.59 Vs 5.26 N)

o DTP Less force as strain increases

Shape memory effect

· DTP Polymer chains crosslinked, not case in conventional aligners

o The shape recovers in DTP when strain is removed, which does not occur to the same degree in conventional aligners Lee 2022

o Accelerated by placing in water

Unknowns

· How effective shape memory is remains unclear

· Cytotoxicity – not enough data, although manufacturer protocols, lack of studies

· Changing thickness, unclear how much of a difference in force it makes

Clinical points

Teeth extrusion

Lateral incisors

· Difficult to do with conventional aligners,

· Create ‘wedging’ gingival pressure columns to squeeze the teeth to cause an extrusive force.

Elastic Hooks without loss of force delivery on single tooth

· Hook printed into aligner with DTP, instead of cut out which alters the force of the aligner instantly, maintain tooth control

· Tip aligners and elastics: Still add attachment to tooth to prevent aligner displacing

Mandibular advancement

· Problem of mandibular advancement with aligners

o Wings soft and not maintaining the AP position

o Hard block many breakages

· DTP choice of thickness of block

Bite ramps

Conventional bite ramps: limited length and often too short

DTP no limit to size and thickness, and can be designed to not contact upper palatal surfaces, maintaining full tooth control

In the Transverse

o Palatal coverage can be added as feature, similar to a TPA

o Still being researched how much force can be delivered with palatal coverage

Concluding statement

Enjoy the variability of direct printed aligners.

Contributions

Contents: Abdallah Sharafeldin

Edited and produced: Farooq Ahmed