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. 2013:2013:351279.
doi: 10.1155/2013/351279. Epub 2013 Apr 30.

Strain Distribution in a Kennedy Class I Implant Assisted Removable Partial Denture under Various Loading Conditions

Reza Shahmiri  1 , John M Aarts, Vincent Bennani, Raj Das, Michael V Swain
Affiliations

Strain Distribution in a Kennedy Class I Implant Assisted Removable Partial Denture under Various Loading Conditions

Reza Shahmiri et al. Int J Dent. 2013.

Abstract

Purpose. This in vitro study investigates how unilateral and bilateral occlusal loads are transferred to an implant assisted removable partial denture (IARPD). Materials and Methods. A duplicate model of a Kennedy class I edentulous mandibular arch was made and then a conventional removable partial denture (RPD) fabricated. Two Straumann implants were placed in the second molar region, and the prosthesis was modified to accommodate implant retained ball attachments. Strain gages were incorporated into the fitting surface of both the framework and acrylic to measure microstrain ( μ Strain). The IARPD was loaded to 120Ns unilaterally and bilaterally in three different loading positions. Statistical analysis was carried out using SPSS version 18.0 (SPSS, Inc., Chicago, IL, USA) with an alpha level of 0.05 to compare the maximum μ Strain values of the different loading conditions. Results. During unilateral and bilateral loading the maximum μ Strain was predominantly observed in a buccal direction. As the load was moved anteriorly the μ Strain increased in the mesial area. Unilateral loading resulted in a twisting of the structure and generated a strain mismatch between the metal and acrylic surfaces. Conclusions. Unilateral loading created lateral and vertical displacement of the IARPD. The curvature of the dental arch resulted in a twisting action which intensified as the unilateral load was moved anteriorly.

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Figures

Figure 1
Figure 1
(a) Orientation of strain gauges on metal framework and acrylic surfaces. (b) Strain gauges placement on acrylic surface.
Figure 2
Figure 2
(a) Bilateral loading uniform; (b) bilateral loading premolar; (c) bilateral loading molar.
Figure 3
Figure 3
(a) Unilateral loading uniform; (b) unilateral loading premolar; (c) unilateral loading molar.
Figure 4
Figure 4
Maximum mean microstrain values of metal surface for all three bilateral loading conditions (left lateral mesiobuccal area).
Figure 5
Figure 5
An inverse correlation between maximum microstrain of the mesiobuccal area next to the rest versus the distobuccal area next to the implant as the loading point moves from uniform to molar and then premolar.
Figure 6
Figure 6
Comparison of microstrain values in both metal framework and acrylic base (bilateral loading conditions).
Figure 7
Figure 7
Comparison of microstrain values in both metal framework and acrylic base (unilateral loading conditions).
Figure 8
Figure 8
Microstrain-time plot of gauge 1 illustrating preloading, loading, and unloading microstrain behaviour during a bilateral uniform loading cycle.
Figure 9
Figure 9
Lever created by the effort arm in relation to the resistance arm, demonstrating the increase in the lever as it extends anteriorly.
Figure 10
Figure 10
Twisting of the prosthesis around the axis of rotation during unilateral loading of right side.
See this image and copyright information in PMC

References

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