A multi centre randomized controlled clinical trial comparing conventional loading of an overdenture on two implants with a bar to immediate loading of an overdenture on two implants with a bar.

Recent literature shows that implant supported prostheses are a significant
improvement when compared to conventional prostheses. A lower jaw with severe
resorption frequently causes problems, functionally as well as socially.
Several authors describe treatment concepts for the edentulous mandible, such
as an overdenture on two implants, attached by balls or by a bar. In addition,
an overdenture on 4 implants attached by a bar and a rigid bridge on 4 or more
implants are described. There is an agreement in literature that the use of
overdentures on 2 implants is a reliable treatment modality in the edentulous
mandible.
Overdentures on 2 implants interconnected by a bar are an improvement in
patient satisfaction and quality of life when compared to full conventional
prostheses. Moreover, these overdentures seem to be a financially favorable
treatment option when compared to the alternative options mentioned above. A
number of authors even have the opinion that this option is to be preferred
when treating the edentulous mandible.
For a long period, an osseointegration phase of 3 to 6 months was considered to
be essential to accomplish predictable treatment outcomes. Recent clinical and
experimental research regarding early and direct loading have actually revealed
that successful osseointegration can be accomplished. Furthermore, a lot has
been published about topography and chemical additions of the implant surface.
Both aspects are able to enhance osseointegration. Certain surfaces, such as
those of SLActive implants, have a positive effect on primary implant
stability. Possible advantages of shorter healing times prior to implant
loading are a reduction in treatment time, lower costs and higher patient
satisfaction. However, there is still no consensus because of a lack of long
term prospective research.

There is no long term prospective clinical research based on the principle of
direct loading (within 24 hours) of overdentures on 2 implants with a bar in
the mandible. Recently, for the period of 12 months, a pilot study has been
carried out including 64 healthy adults. No complications were revealed.
The good results of the pilot have been the motivation to start a multi centre
randomized controlled clinical trial. Conventional loading (after 6 weeks) of
an overdenture on 2 standard SLA implants with a bar are compared to direct
loading of the similar construction on 2 SLActive implants.
In addition, microbiological and genetic factors are studied that might play a
role in the etiology of peri-implant infections.

A multi centre randomized controlled clinical trial

After selection based on determined criteria, 92 patients are allocated at
random in 2 treatment centres. During several points in time, the following
parameters are registered:
- patient satisfaction
- total treatment costs
- total treatment time
- total prosthetic aftercare
- bone level around implants by the use of standardized x-rays
- periodontal parameters
- implant stability

The estimated extra time amounts to 1 hour a year.