The randomized shortened dental arch study (RaSDA): design and protocol

Background: Various treatment options for the prosthetic treatment
of jaws where all molars are lost are under discussion. Besides the
placement of implants, two main treatment types can be
distinguished: replacement of the missing molars with removable
dental prostheses and non-replacement of the molars, i.e.
preservation of the shortened dental arch. Evidence is lacking
regarding the long-term outcome and the clinical performance of
these approaches. High treatment costs and the long time required
for the treatment impede respective clinical trials.
Methods/design: This 14-center randomized controlled
investigator-initiated trial is ongoing. Last patient out will be
in 2010. Patients over 35 years of age with all molars missing in
one jaw and with at least both canines and one premolar left on
each side were eligible. One group received a treatment with
removable dental prostheses for molar replacement (treatment A).
The other group received a treatment limited to the replacement of
all missing anterior and premolar teeth using fixed bridges
(treatment B). A pilot trial with 32 patients was carried out. Two
hundred and fifteen patients were enrolled in the main trial where
109 patients were randomized for treatment A and 106 for treatment
B. The primary outcome measure is further tooth loss during the
5-year follow-up. The secondary outcome measures encompassed
clinical, technical and subjective variables. The study is funded
by the Deutsche Forschungsgemeinschaft (German Research Foundation,
DFG WA 831/2-1, 2-2, 2-3, 2-4, 2-5). Discussion: The particular
value of this trial is the adaptation of common design components
to the very specific features of complex dental prosthetic
treatments. The pilot trial proved to be indispensable because it
led to a number of adjustments in the study protocol that
considerably improved the practicability. The expected results are
of high clinical relevance and will show the efficacy of two common
treatment approaches in terms of oral health. An array of secondary
outcome measures will deliver valuable supplementary information.
If the results can be implemented in the clinical practice, the
daily dental care should strongly profit thereof. Trial
registration: The trial is registered at ClinicalTrials.gov under
ISRCTN68590603 (pilot trial) and ISRCTN97265367 (main trial).