Doha H. Hendawy, Cherif A. Mohsen And Shams W. Amgad,

ABSTRACT
Statement Of The Problem: Restorative Dentistry Has Become An Essential Part In The Modern Clinical Practice. One Of The Conservative Clinical Options Is The Inlay Retained Fixedpartial Denture (IRFPD) But From The Other Hand, It Has A Higher Risk Of Fracture Due To The Minimal Invasive Preparation And Also Debonding.

Purpose: To Compare The Fracture Resistance And Internal Adaptation Of Three Types Of Materials (zirconia Ceramic, Lithium Disilicate And Ceramic Reinforced Polyetheretherketone) Of Two Designs Of Inlay-Retained Fixed Partial Dentures (IRFPDs).Methods:. Sixty Inlay Retained Fixedpartial Dentures Were Constructed, Each Model Including Extracted Mandibular Firstpremolar And Firstmolar Which Were Embedded In A Plastic Cast And Then An Impression Was Taken To Form Epoxy Resin Dies To Receive The Different Preparation Designs. Samples Were Divided Into Two Groups According To Type Of Inlay Preparation Design, Group B (no=30 Inlay Retained Fixedpartial Dentures) Was Designed In Box-shape Design, Group S (no=30 Inlay Retained Fixedpartial Dentures) Was Designed In Slice Shape Design. Then, Each Group Will Be Subdivided Into Three Subgroups According To Ceramic Material Used Into, Group Z (no=10 Inlay-retained Fixedpartial Dentures) Fabricated From Zirconia Ceramic (Katana STML Zirconia), Group L (no=10 Inlay-retained Fixedpartial Dentures) Fabricated From Lithium Disilicate Ceramic (IPS E.max CAD), And Group B (no=10 Inlay-retained Fixedpartial Dentures) Fabricated From Ceramic Reinforced PEEK (bre-CAM. BioHPP). Samples Were Thermocycled. Five Samples From Each Subgroup Were Tested For Internal Adaptation Using USB Digital Microscopy With Bult In Camera, While The Other 5 Samples Were Tested Using The Universal Testing Machine To Measure Fracture Resistance.

Results: For The Internal Adaptation, Regarding The Material Type. The Results Showed A Statistically Significantdifference As The Highest Mean Values Were Recorded For E-max IRFPDs, Followed By Zirconia IRFPDs, While The Lowest Mean Values Were Recorded For Bio-HPP IRFPDs. Regarding The Preparation Design, For Both E-max And Bio-HPP IRFPDs The Highest Mean Values Were Recorded For The Slice-shaped Design Followed By The Box-shaped Design, While For Zirconia IRFPDs, Results Showed Non-significantdifference Between Tested Designs. For The Fracture Resistance Test The Highest Mean Value Was Recorded For Zirconia (2427.8?m ? 163.1 ?m), Followed By Bio-Hpp (2067.9?m ? 219.1 ?m), While The Lowest Value Was Recorded For The E.max (1239.2?m?74.7?m).Conclusion: Internal Adaptation Of The Inlay Retained Fixedpartial Dentures Is Affected By The Material Type And Preparation Design, While The Fracture Resistance Is Affected By The Material Type. Zirconia Ceramics Have The Properties To Be The Most Appropriate Material To Be Used In Construction Of Conservative Inlay Retained Bridges. Lithium Disilicate IRFPDs Show Fracture Strength Above The Clinically Expected Loading Forces And Which Seems To Be Promising To Be Used As Alternative To The Traditional More Invasive Restorations. Bio-HPP Has A Good Internal Fitand Fracture Resistance To Be Used In The Dental Applications. Clinical Recommendation: Further Investigations Need To Be Demonstrated For Internal Adaptation Of Inlay Retained Fixed Bridge