TADs is success in science or practice?

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Farooq Ahmed

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Join me for a summary looking at miniscrews, looking at where the answer to successful TAD placement lies, in research or clinical practice. The reasons for higher failure rates than others with TADs was explored through 3 key factors; insertion torque, site selection and root proximity. Evaluation of both scientific and clinical processes were described by Sebastian Baumgartel at the British Orthodontic Conference, as the Northcroft lecture.


Is torque a factor in TAD success?

Torque study – compression during insertion Motoyoshi 2006

  • High torque – 60%
  • Low torque = 72%
  • Medium torque – 92%


  • Low torque = low compression, low primary stability – early failure as not engagement with screw
  • High torque = high compression, early success, but greater resorption after insertion, remodelling results in a resorption process
  • Medium = best of both = sufficient compression for primary stability, not high enough to cause resorption remodelling


  • Ideal torque range – 10 Ncm Shantavasinkal 2016
    • Study of buccal tads
  • Sebastian’s empirical experience between 10-25Ncm depending on site



  • Aim for medium torque
  • Target 10Ncm
  • Exceed 10Ncm on palate acceptable


What is the best site for TAD insertion?


Keratinised gingiva

  • Evidence – states no difference Lim 2009, Chen 2008, Park 2006, Cheng 2004
  • Non Keratlised – depends on mobile or non mobile, with non-mobile higher success rate Viwattanatipa 2009
  • 2mm apical to muco-gingival junction
    • zone of opportunity


Target zones and site

  • No roots
  • Consistent cortical bone
  • More tolerant to higher torque
  • Attached gingiva with low mobile mucosa



Is there ideal bone?

  • = if ideal torque = ideal cortical plate thickness
    • 1-1.5mm cortical plate thickness
  • CBCT can be overkill, using research sites for average sites



Ideal site:

  • 1st premolar region (transverse)  Sebastian 2009
  • 2 mm away from mid-palatal suture
    • = creates ideal zone ‘Mx1’


Evidence of site selection success

  • 98% Vs buccal 71% Houfar 2017
  • 84% Trainee success Sebastian 2020
  • Success of Sebastian anterior palate 100%, maxillary buccal lowest 85%


Does root proximity influence TAD success?

  • Not just contact with roots, but proximity to root also causes failure Kuroda 2007, Asschericks 2008, Chen 2008



  • Increase root and PDL proximity = bone stress increases = increase bone turnover = increase failure of TAD
  • 4mm interradicular distance needed (depending on size of tad) to achieve 1 mm clearance from roots
  • Most buccal sites have less than 4mm (resolve through diverging roots, or sites with no roots)


What happens if TADs fail and we try again?

  • Secondary insertion success
    • 58% (reduced by 33%) Park 2006
    • 2%  (reduced by 36%) Uesugi 2017
    • 1% buccal (reduced by 21%), 88.9% palatal (increased by 4%) Uesugi 2018
      • Uesugi 2018 showed buccal failure increases for secondary insertion, but palatal insertion increases success


For more education see Sebastian’s TAD course:


I have no financial interest




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