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CAMLOG&Science – Chapter 5
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DIFFERENT ANCHORAGE OPTIONS FOR REMOVABLE OVERDEN-
TURES ON TWO OR FOUR IMPLANTS
In a study in 76 patients with edentulous mandibles, Weinländer et al.
(2010) examined the mode of anchorage of overdentures on either two or
four implants. With two implants, a prefabricated round bar was used for
retention, with four implants, either several prefabricated bars were used
or one milled bar. The authors concluded that the anchorage methods had
no impact on treatment success and stability of the periimplant tissue, how-
ever, prosthetic complications were less frequent for the milled bars on four
implants (p<0.01). This finding is supported by Krennmair et al. (2008c),
who demonstrated that a milled bar on four interforaminal implants led to
fewer technical complications than the use of several round bars.
While comparing the treatment success of mandibular overdentures on four
implants retained with milled bars or telescopic crowns in 51 edentulous
patients, Krennmair et al. (2012a) reported that the periimplant conditions
and prosthetic follow-ups were stable for both techniques. Although more
plaque and tartar was observed with the bar constructions, the prosthetic
treatment showed slight benefits with this technique. The authors conclu-
ded that both retention methods were successful and that the clinician
should choose the technique he/she is most familiar with.
In the maxilla, Krennmair et al. (2008a and 2008b) compared retrospec-
tively overdentures retained either by four implants in the anterior region
or by six implants inserted in the posterior regions after augmentation. Af-
ter an average period of three and a half years, 34 patients with 179 im-
plants were examined. The cumulative implant survival rate was 98%.
There was no difference between the two treatment groups. The authors
concluded that with good planning, both concepts allow high implant sur-
vival rates and excellent periimplant conditions. (Tabs. 6 and 7).
EXCELLENT RESULTS INDEPENDENT OF THE RETENTION MODE
USED FOR AN OVERDENTURE
Several publications reported prospectively or retrospectively the influence
of the different mode of prosthetic retention in edentulous maxilla and / or
mandible (tables 7 and 8). Krennmair et al. (2012b) performed a cross-over
prospective study including 20 subjects and reported the patient satisfaction
and preferences for implant-supported mandibular overdentures as well as
the prosthetic maintenances of the two retentionmodes. Each patient received
two mandibular implants. After healing (three months and two-stage surgery),
patients received a newmaxillary denture and an implant-retained mandible
overdenture using either ball or locator attachments in alternating frequencies
of three months each. Thereafter, a longitudinal follow-up of one year was
performed. The study showed a statistically significantly improved satisfaction
for all item scores between baselines (old dentures without implants) and
after the three months of function of the implant-retained overdentures
(p<0.05). No statistically significant difference was noticed between the
two retention modes. However, in terms of prosthetic maintenance, more
aftercare interventions due to more matrix activation were necessary for
the locator abutment in comparison to the ball attachment.
Another prospective study (Krennmair et al. 2006a and 2006b) including 25
patients compared the overdentures retained with ball or telescopic crown
attachments on two interforaminal implants after three years. It was demon-
strated that technical complications with the ball abutments (61%of cases)
occurred much more frequently than with the telescopic crowns (38%,
p<0.01). The five-year follow-up (Krennmair et al. 2011) confirmed the three-
years results in terms of maintenance, however during year four and five no
difference was observed concerning prosthetic complication. Despite this,
implant treatment success in both groups was 100% during five years. The
conditions of the periimplant tissue and treatment satisfaction did not differ
significantly. Similar results and success rates were found by Karabuda et
al. (2008) comparing overdentures with bar and ball abutments on two to
four implants using different implant systems.
MANDIBLE
MAXILLA
Milled Bar
✓
✓
Round bar
✓
✓
Ball abutment
✓
✓
Telescopic crown
✓
Locator abutment
✓
Horizontally screw-retained fixation
✓
✓
Tab. 8:
Overview of the documentation on treatment forms on CAMLOG
®
Implants in the
maxilla and mandible of edentulous patients with different retention techniques