In Vitro Comparative Study of Retention of Maxillary Kennedy Class I Removable Partial Denture Retained with Four Different Designs of Esthetic Clasps

Abstract

Abstract\rPurpose: To study the effect of clasp, design, material, and amount of retentive\rundercut of esthetic clasp on retention of removable partial dentures restoring\rmaxillary Kennedy class I removable partial denture.\rMethods: Eight standard educational acrylic resin models represent maxillary\rKennedy class I with remaining teeth extending from the right first premolar to\rthe left first premolar teeth were used in the study. Both first premolars teeth of\reach cast were prepared to receive full ceramometal crowns with mesial occlusal\rrest seat, proximal guiding planes, and different mesio-buccal retentive undercuts\rof 0.25 mm for four models, and 0.50 mm in other four models. Four different\rremovable partial denture esthetic clasps on both maxillary first premolar crowns\rwere used; Equipoise clasps, RPA clasps fabricated by cobalt-chromium alloy and\rcovered with Teflon tube, RPA clasps fabricated by polyamide material, RPA clasps\rfabricated by acetal resin material. Metal ring hooks were fabricated, soldered to\rthe occlusal rest of clasp assembly. Each clasp was seated manually to be pulled\rby the jig of the universal testing machine to measure retention of the removable\rpartial denture. Data was collected and statistical analysis was performed.\rResults: RPA clasps covered with Teflon tube recorded the highest retention force\r{mean value (13.92 ± 1.41 N) followed by Equipoise clasps group (5.19 ± 0.59 N)\rthen Polyamide clasps group {(4.99 ± 0.34 N)}, while acetal resin clasps group\rrecorded the lowest retention force mean value (3.33 ± 0.33 N). Regardless to clasp\rtype, it was found that 0.25 mm retentive undercut recorded higher retention\rforce than 0.50 mm undercut.\rConclusion: Within the limitations of this in vitro study, it could be concluded\rthat RPA clasps fabricated by cobalt-chromium alloy and covered with Teflon tube\rrecorded the highest retention force.