Resilient Stud Versus Bar Attachments for Inclined Implants Supporting Mandibular Overdentures. An In Vitro Study of Loading and Dislodging Strains.

Abstract

To evaluate strain around resilient stud and bar attachments for inclined implants supporting mandibular overdentures during loading and dislodging. A mandibular edentulous model was printed using the laser sintering technique. Two vertical implants and two 30-degree distally inclined implants were placed in canine and premolar areas, respectively. Overdentures were attached to the implants with either a resilient stud (Locator, group 1) or a bar/clip (group 2) attachment. Three strain gauges were mounted at the buccal, lingual, and proximal surfaces of each implant. Microstrains were registered during vertical loading and dislodging force applications and compared between attachments (resilient stud and bar) and implant positions (vertical and inclined). For canine implants, bar overdentures recorded significantly higher microstrains than Locator overdentures during vertical loading. For premolar (inclined) implants, Locator overdentures recorded significantly higher microstrains than bar overdentures during vertical dislodging. For both groups (during loading) and the bar overdenture group (during dislodging), canine (vertical) implants showed significantly higher microstrains than premolar (inclined) implants. Within the limitations of this in vitro study, canine (vertical) implants may be at risk of increased stresses during loading if bar attachments are used for vertical and inclined implants supporting mandibular overdentures, and premolar (inclined) implants may be at risk of increased stresses during dislodging if Locator attachments are used. For both attachments, canine implants showed significantly higher microstrains than premolar implants during loading and dislodging.