Dr Claudia Cruz and Roberto Stadi describe the predicability of aligners, indirect bonding for labial and lingual appliances
Aligners
Factors which reduce the predictability of aligners
- Manufacturing process: 0.1mm
Force delivery
- Thermoforming force decay
- Inconsistent thickness of aligner
- Anatomy of teeth: Rounded teeth (Canines and Premolars / Bicuspids)
How to improve predictability
1. Clinical:
- Increase attachment size, alter attachment orientation, stage movements
2. 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.
