Dr Claudia Cruz and Roberto Stadi describe the predicability of aligners, indirect bonding for labial and lingual appliances

Summary

Aligners

Factors which reduce the predictability of aligners

· Manufacturing process: 0.1mm

· Force delivery

o Thermoforming force decay

o Inconsistent thickness of aligner

· Anatomy of teeth: Rounded teeth (Canines and Premolars / Bicuspids)

How to improve predictability

Clinical:

· Increase attachment size, alter attachment orientation, stage movements

Technological – not achieved yet!

· Use actual root information (CBCT), control thermoforming features, calculate forces required and ideal attachment for tooth movement

Indirect labial bonding

· Up to 1mm error in bracket placement in indirectly

· Up to 1 mm error in robotic archwire formation

· Outcomes worse than conventional direct bonding

· Tooth morphology anterior 2-2 will usually require manual wire bending

Lingual appliance

· Accurate to 40 and up to 1 mm

· Torque discrepancies manifest in greater 2nd order error than labial

· Extraction cases: more critical to control moment force ratio, if not = greater retroclination / loss of torque of upper labial segment

Conclusion:

New technology have discrepancies which the clinician should factor into treatment planning

References

Customised labial brackets accuracy

Alford, T.J., Roberts, W.E., Hartsfield Jr, J.K., Eckert, G.J. and Snyder, R.J., 2011. Clinical outcomes for patients finished with the SureSmile™ method compared with conventional fixed orthodontic therapy. The Angle Orthodontist, 81(3), pp.383-388.

Morphology of teeth and outcomes of orthodontics

Miethke, R.R. and Melsen, B., 1999. Effect of variation in tooth morphology and bracket position on first and third order correction with preadjusted appliances. American Journal of Orthodontics and Dentofacial Orthopedics, 116(3), pp.329-335.

Effectiveness of aligners

Papadimitriou, A., Mousoulea, S., Gkantidis, N. and Kloukos, D., 2018. Clinical effectiveness of Invisalign® orthodontic treatment: a systematic review. Progress in orthodontics, 19(1), p.37.

Accuracy of lingual appliances

Grauer, D. and Proffit, W.R., 2011. Accuracy in tooth positioning with a fully customized lingual orthodontic appliance. American Journal of Orthodontics and Dentofacial Orthopedics, 140(3), pp.433-443.

Loss of torque affects,labial and lingual

Liang, W., Rong, Q., Lin, J. and Xu, B., 2009. Torque control of the maxillary incisors in lingual and labial orthodontics: a 3-dimensional finite element analysis. American Journal of Orthodontics and Dentofacial Orthopedics, 135(3), pp.316-322.