Nesreen El Mekawy, Salah Hegazy and Christine Raouf
Purpose: To compare thermo-elastic versus hard acrylic resin denture base regarding tooth retained and supported mandibular overdenture retention with different overdenture abutment preparation.
Materials and methods: Eighteen patients had completely edentulous maxilla against partially edentulous mandible in which only two canines were remaining. The two canines were endodontically treated. Shortened to a level 3-4 mm above gingival margin, cementation of two long metal copings was done. Patients had two mandibular overdentures hard acrylic one and Thermo-elastic one. After two months the two abutments were reshaped and shortened more to have a dome shaped preparation 1-2 mm above gingival margin, the patient had two teeth supported overdenture on short copy. After another two months the same patient received two stud attachments. Retention of both hard and thermo-elastic acrylic mandibular overdenture MOD of each abutment preparation was measured in the same patient after 24 hours and after one month from its insertion date by using a digital forcemeter device.
Results: There was a significant difference between groups, 24 hours and one month after mandibular overdenture MOD insertion. The greatest retention values were recorded with tooth retained MOD with long copings followed by tooth retained MOD with stud attachments and the lowest retention values were obtained with tooth supported MOD with short copings. Retention values of thermo-elastic acrylic resin MOD was greater than hard acrylic resin MOD for all groups, Finally the time factor has an effect on the retentive values, retention values at one day after MOD insertion was greater than values after 30 days of MOD insertion for hard and thermo-elastic acrylic resin MOD.
Conclusion: Within limitations of this study, thermo-elastic acrylic resins showing more retentive values than hard acrylic one especially with the long copying preparation following by stud attachments.
