Retentive force of Different
Overdenture Stud Attachments in Various Dislodgement. In
Vitro Study Mizutani H, Destine D,
Rutkunas V*, Nakamura K**, Ishikawa, S***
Lithuania Vilnius
University Institute of Odontology
**
***
Ishikawa Dental Clinic
e-mail:mztn.rpro@tmd.ac.jp
1. The overdentures have already proved
themselves to be a preferable method to preserve oral function and to delay
or eliminate future prosthodontics problems. A
properly constructed overdenture has to provide retention, stability,
distribute occlusal loads evenly.
Crucial factors are: 1.
status of abutments 2.
proper extension of bases 3.
type of attachment
2.
2. Selection of overdenture attachment has
proved to be an important factor influencing, support, retention, stability
of overdentures. Magnetic attachments could be the only option
left for periodontal compromised abutments or implants with insufficient
length or diameter constant retentive forces. There are three important
characteristics describing retention of attachments: maximum retentive
force, range of retention and retentive energy. Dynamics of retentive force
changes during dislodgement is also believed to be important. As we see
these characteristics are quite different for magnetic and mechanical
overdenture attachments. On the dislodgement graph of magnetic and mechanical
attachments we can see maximum retentive force, range of retention and
retentive energy which is equal to all area below the curve.
3. Plenty of studies have measured retentive properties of magnetic
attachments by anterior dislodgement tests. However pure anterior
dislodgments rarely occurs intraoraly, while
rotational dislodgements are more common. Different dislodgment patterns
could result in different levels of retention. Therefore the aims of the
study were: 1.
to evaluate maximum
retentive force and energy of different overdenture attachments during
anterior, posterior and lateral dislodgment. 2.
to compare retentive
characteristics between different types of attachments and types of
dislodgements.
4. The types of attachments
tested were: – Magnedisk 500, Magfit EX
600W, Root keeper (dome shaped), Hyperslim 4013
and Hyperslim 4513;
5. In addition, we have mechanical O-P anchor, Root Locator
(pink), Era Overdenture (white and orange). Twelve specimens of each type
of attachment were tested.
6. The model was constructed
for the evaluation of maximum retentive force and energy during anterior dislodgement.
A cast canine model was embedded into acrylic block and periodontal
ligament with 1mm thickness of impression material imitated. And a
mandibular model with two cast canine was made to evaluate the maximum
retentive force and energy during rotational anterior posterior lateral
dislodgement. Periodontal ligament and mucosa were imitated by silicone
with corresponding thickness of 1 and 4 mm. A mandibular overdenture was
also fabricated on this model in ordinary way.
7. The dislodgement slides
were performed by two chains attached in; Two canines for anterior dislodgement (left) Second molar for posterior (center) Canine and second molar denture area for lateral dislodgement (right) Different attachments were interchanged by means of autopolymerizing resin.
Results
8. Maximum retentive force
and retentive energy measurements were made by universal testing machine
AGS-H and software interface Trapezium. Measurements performed with cross
head speed of 50 mm/min. The statistical analysis was made by SPSS for
Windows software. The means and standard deviations were calculated, and
statistical comparison was made using a one-way analysis of variance.
Significance of differences between each group had been evaluated.
9. The graph represents means of maximum retentive force with
standard deviations during anterior dislodgements. Magnetic attachments
came up with lower but constant maximum retentive force, while mechanical
ones had a higher but more variable.
10. Maximum retentive force for posterior
dislodgement, attachments are listed by the highest maximum
retentive force to the lowest. As we see, insignificant differences were
limited to magnetic attachments group.
11. For mechanical attachments, maximum retentive force of
lateral dislodgement is much more lower than anterior and posterior dislodgement.
In magnetic, lateral is between anterior and posterior.
12. For anterior dislodgement similar results represent retentive
energy means during different patterns of dislodgements. Dramatic change could
be noticed for O-P anchor which had the lowest maximum retentive force but
one of the highest retentive energy value.
13. For magnetic attachments the energy between anterior and
posterior dislodgement have no difference. However, for mechanical
attachments, retentive energy of posterior is bigger than that of anterior.
14. For lateral dislodgement retentive energy is between anterior
and posterior in both magnetic and mechanical attachments
Only maximum retentive
force cannot define retentive properties of attachment devices. Magnetic
attachments owing low retentive energy inherently have comparatively small
range of retention. Retentive energy represents energy transferred to
abutment during dislodgement. However the exact value of load or energy
tolerable by abutments is unknown and depends on multiple factors.
Retentive characteristics strongly depend on pattern of dislodgement.
1.
Magnetic attachments having adequate
retentive force have low retentive energy 2.
Retentive properties depend on dislodgment
pattern 3.
Understanding of retention dynamics aids in
proper prescription of different attachments 4.
Magnetic attachments provide constant and
easily prescribed retention. Low retentive energy of magnetic attachments
could aid abutment preservation
Q & A