Effect of different implant numbers and locations on strains around implants retaining mandibular overdentures with locator attachments. An invitro strain gauge analysis

Abstract

Aim: This in vitro study was performed to evaluate the effect of different implant numbers and locations on strains around implants retaining mandibular overdentures with locator attachments. Materials and methods:Five implants were inserted in the interforaminal area of mandibular edentulous acrylic model in the following locations; 1) one in midline areas, 2 in canine areas and 2 in premolar areas. Locator attachments were used to connect mandibular experimental overdentures (n=5) to the implants. Two linear strain gauges were bonded at buccal and lingual surface of each implant. According to the implant number and location of the implants, the strain was measured (during unilateral and bilateral loading) using the following implant overdenture designs: Group 1: strains were measured around mid-line implant only, while the other locator attachments were disconnected. Group 2: strains were measured around the 2 canine implants only. Group 3: strains were measured around the 2 premolar implants only, Group 4: strains were measured around the midline and the 2 canine implants only, Group 5: strains were measured around the midline and the 2 premolar implants only.Results: For midline implants during bilateral and unilateral loading, the highest strains were noted with group 1 and group 5, and the lowest strain was noted with group 4. For distal implants during bilateral loading, the highest to the lowest were group 3> group 2> group 4> group 5. For distal implants on the loading and non-loading sides during unilateral loading, the highest to the lowest were group 3> group 2> group 5> group 4. For group, 4 and 5, midline implants recorded the highest strain, then distal implants on the loading sides, and the lowest strains were observed on the distal implants of the non-loading sides. Conclusion:within the limitations of this in vitro study, three implants used to retain mandibular overdentures with locator attachments were associated with reduced peri-implant strains than one or 2-implants regardless placement of posterior implants in canine or premolar areas. However, the midline implants is at increased risk of implant overloading than distal implants. This risk decreased when distal implants are positioned in canine areas.

Effect of Different Denture base Materials on Stresses Transmitted to supporting structures of Implant-supported Mandibular Overdenture

“…The discrepancy in the stress shielding effect was ascribed to the stiffness and elastic modulus of the overdenture. (14,21) .…”

“…Two linear strain gauges (KFG-1-120C1-11, Kyowa Electronic Instruments; Resistance 120.2 0.2, gauge length 1 mm, gauge factor 2.11 1.0%) were affixed close to the crest of the ridge at the buccal and lingual surfaces associated with each implant in order to measure the peri-implant strains during loading. (14) Figure 7. The long axis of each gauge was in line with the long axis of the implants.…”