%0 Journal Article
%T Strain Distribution in a Kennedy Class I Implant Assisted Removable Partial Denture under Various Loading Conditions
%A Reza Shahmiri
%A John M. Aarts
%A Vincent Bennani
%A Raj Das
%A Michael V. Swain
%J International Journal of Dentistry
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/351279
%X 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 (¦̀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 ¦̀Strain values of the different loading conditions. Results. During unilateral and bilateral loading the maximum ¦̀Strain was predominantly observed in a buccal direction. As the load was moved anteriorly the ¦̀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. 1. Introduction A well-constructed removable partial denture (RPD) can be an adequate treatment option for the partially edentulous patient [1, 2]. The prosthesis is supported by the framework via teeth contact and by the distal extension base. The loading of the Kennedy class I is complicated by the mismatch of tissue resiliency and the abutment teeth which have different viscoelastic responses. The soft tissue under load has a displacement range of 350¨C500£¿¦̀m, whereas a sound tooth has a displacement of 20£¿¦̀m under the same load [3]. This mismatch of support will result in the transmission of torque forces to the abutment teeth via a rotational movement of the RPD [4]. In 1984 Watt and MacGregor [5] linked tooth mobility to the torque forces that are developed against the abutment teeth. In addition, the rotational movement of the RPD is directed towards the underlying soft tissue, and as a result the torque force in the soft tissue is then transmitted as a shearing force, which progressively causes resorption of residual ridges [6]. One of the recurrent problems associated with a bilateral distal extension RPD stems from the loading of the edentulous
%U http://www.hindawi.com/journals/ijd/2013/351279/