Mohannad Alaa El Din Samy, Amal Rekaby Taha And Ahmed Emad Fayyad,

ABSTRACT


Aim: The Aim Of This Study Was To Compare Between The Stresses Induced Around The Abutments Of Removable Partial Denture Retained By Conventional Extra Coronal Attachments And That Retained By Resin Bonded Zirconia Attachments In Kennedy Class I Cases. Methodology: Two Acrylic Models Representing Kennedy Class I Cases Were Fabricated With Natural Abutments Teeth (firstand Second Premolars) Bilaterally. The Control Model Abutments Were Prepared For Full Coverage Crowns. Conventional Extra Coronal Attachments Were Fabricated By Conventional Casting Of CAD/CAM Designed Wax Pattern. The Intervention Model Abutments Were Roughened Lingually And Distally And A Rest Seat Was Prepared On The Distal Side Of Each Second Premolar, The Zirconia Attachments Were Then Milled From Zirconia Blocks Using CAD/CAM Technology. Metal Framework Partial Dentures Were Then Constructed For Both Models With Nylon Caps Picked Up. A Metal Rod Was Soldered To Each Framework In The Position Of The Firstmolars, Where Universal Testing Machine Was Used To Apply Vertical Load On The Firstmolar Unilaterally And Bilaterally Meanwhile Strain Gauges Were Attached Buccally And Distally Around The Abutments On Both Sides Of The Arch And Connected To A Strain Meter To Measure The Micro Strains Exerted Around The Abutments. The Right Side Of Each Model Was Employed As The Working Side, While The Left Side Was The Non-working Side.

Results: As For The Working Side, The Results Revealed Statistically Significantdifference Between Both Groups, Where The Zirconia Attachment Exerted Almost Half The Strain Exerted By The Conventional Metal Attachment. In Addition, There Was Also Statistically Significantdifference Between Both Groups At The Non-working Side, Where The Zirconia Attachment Exerted Almost One Third That Exerted By The Conventional Metal Attachment. Moreover, As For The Central-bilateral Loading The Results Also Revealed Statistically Significantdifference Between Both Groups. The Zirconia Attachment Showed Less Strain Than That Exerted By The Conventional Metal Attachment.

Conclusions: The Zirconia Attachments Showed More Favourable Stress Distribution Around The Retaining Abutments Under All Loading Conditions Which Encourages Their Use As A Reliable Substitute To Conventional Metal Attachments.