Basically, the SDA concept (shortened dental arch) is fine
SDA concept or shortened dental arch concept is the concept of a dental arch (upper or lower jawbone) that does not have the back teeth or molars.
Many studies continue to show that individuals without these back teeth have little impact on things including chewing, speaking, TMJ health, and general feeling about the health of their mouth.
EBD 2015 Levey RPD v SDA measured results all the same.
TMJ health : “The findings provide no evidence that SDA causes overloading of the joints and the teeth, which suggests that neuromuscular regulatory systems are controlling maximum clenching strength under various occlusal conditions.” Hattori 1982 Witter 1994 Witter 2007 Fueki 2011
Witter 2001 “we conclude that shortened dental arches can provide long-term occlusal stability. Occlusal changes were self-limiting, indicating a new occlusal equilibrium.”
Kanno 2006 A review of the shortened dental arch concept focusing on the work by the Käyser/Nijmegen group. Deals with masticatory ability, signs and symptoms of temporomandibular disorders, migration of remaining teeth, periodontal support, and oral comfort.
Experiment showing why SDA works and NTi too (May, B.M. and C. Garabadian, Reducing condylar compression in clenching patients. Crit Rev Biomed Eng, 2000) May 2000
Similar study Becker 1999 JPD 1999
Carlsson 2009 Dogmas – cool article
Second molar missing research is not quite SDA but still relevant to this post.
90% of chewing function is first molar and bicuspid region according to Broadbent 2000.
Nam 2014 Implant supported second molars will improve masticatory ability and patient satisfaction.
Kim 2011 also shows second molar implants increase chewing function.
No the SDA concept or shortened dental arch is worse than full dentition
Other studies show that masticatory function and patient satisfaction is better with full arch of teeth.
Some Japanese research shows SDA is worse, in terms of patient satisfaction, especially if BOTH molars missing. Fueki 2007 post 89 Fueki 2010 and 2011
al-Ali 2007 chewing performance is reduced by removing posterior teeth
De Oliveira 2014 Software study which I never care much for BUT shows decreased number of teeth increases amount of displacement of renaming teeth – again not sure this at all clinically relevant
Schwahn 2013 IJCardio 9 or fewer teeth is when death risks increase across all categories, but ironically takes 9 years for this to show.
It seems the bite force adapts to SDA. Does it matter? Meena JOR 2014
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