Stress analysis of mandibular Kennedy class I partial overdenture submitted to different implant length and clasp designs – An in vitro study

Abstract

PurposeTo analyze the distribution of stresses for mandibular Kennedy class I removable partial overdentures submitted to different implant lengths and clasp designs.Materials and MethodsTwenty‐seven heat‐cured acrylic resin casts with a uniform soft acrylic layer were constructed from models representing the mandibular Kennedy class I removable partial denture with the first premolars terminal abutment on both sides. The casts were grouped into a control group, group I, and group II with three casts of each for designing a different clasp on the last abutment with Rest, Proximal plate, Aker circumferential (RPA), Rest, Proximal plate, I‐bar (RPI), and wrought wire (WW). All casts were submitted to vertical load for stress analysis after preparing channels at the buccal/distal surface of abutments, the crest of the ridge, and the buccal/lingual of the implant for placement of uniaxial strain gauges that can convert the electro‐signals to micro‐strain by using the software. Kolmogorov–Smirnov normality test, independent t‐test, and one‐way anlysis of Variance (ANOVA) test followed by Tukey`s Post Hoc for multiple comparisons test were used for statistical analysis.ResultsThe control group results revealed more significant stresses on the ridge with RPA and RPI clasps but on the abutment with WW clasp as P < 0.05. In group I, the ridge was significantly stressed more than the implant followed by the abutment when the RPA clasp was used while there was insignificance on the implant with RPA and RPI as p > 0.05. In group II, the stresses were more on the abutment with RPA, RPI, and WW clasps followed by lower on the implant and lowest on the ridge.ConclusionsProper implant and clasp type selection are critical for stress distribution on the ridge, abutment, and implant when using removable partial overdenture. The stresses on longer implants are tolerated and more widely distributed than shorter ones.