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