TADs is success in science or practice‪?‬ orthodontics In summary

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%

Understanding

·     
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

·     
Ideal torque range – 10 Ncm Shantavasinkal 2016

o  
Study of buccal tads

·     
Sebastian’s empirical experience between
10-25Ncm depending on site

 

Rules:

·     
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

o   zone
of opportunity

 

Target zones and site

o  
No roots

o  
Consistent cortical bone

o  
More tolerant to higher torque

o  
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

o  
= 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

 

Understanding

o  
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

o  
58% (reduced by 33%) Park 2006

o  
 44.2%  (reduced by 36%) Uesugi 2017

o  
58.1% 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:

https://tadchallenge.com/tad-certification-course

 

I have no financial interest