Alaa A. Khodair, Mohsen H. Abi El Hassan And Rasha Haridy,

ABSTRACT
Objective: This Study Was Carried Out To Evaluate The In Vitro Three-body Wear Resistance Of The Recently Introduced Ormocer-based (Ceram X One Universal) And POSS (Artiste) Nanohybrid Resin Composites Which Have Different And Novel Chemistries Of Their Resin Matrices Compared To A Nanohybrid Resin Composite With Conventional Methacrylate-based Resin Matrix (Filtek Z250 XT).

Materials and Methods: The Specimens Were Divided Into Three Main Groups (n=14) According To The Type Of Resin Composite Material. Each Group Was Further Subdivided Into Two Main Subgroups (n=7) Where Each Subgroup Was Subjected To Wear Cycles Representing Different Aging Intervals Which Were: 250000 Cycles/specimen Equivalent To Three Months And 500000 Cycles/specimen Equivalent To Six Months, The Wear Test Was Done By ACTA Chewing Simulator. Wear Assessment Was Done Using Contact Stylus Digital Profilometer (Talysurf CLI 2000, Taylor-Hobson Precision, Leicester, England) For Measuring Vertical Loss.

Results: Showed Significant Differences In Vertical Substance Loss Between The Three Restorative Materials After 250000 Cycle Equivalent To Three Months And After 500000 Cycle Equivalent To Six Months (P< 0.001). The Highest Vertical Substance Loss Was Observed For Di-functional Methacrylate-based Resin Composite (Artiste) (after 250000 Cycle Equivalent To Three Months, And After 500000 Cycle Equivalent To Six Months). The Lowest Vertical Substance Loss For The Restorative Materials Was Detected For Methacrylate-based Resin Composite (Filtek Z250 XT) (after 250000 Cycle Equivalent To Three Months, And After 500000 Cycle Equivalent To Six Months). Conclusion: 1) Methacrylate-based Resin Composite Without Any Modification In Its Organic Matrix Yielded The Highest Wear Resistance Among The Tested Resin Composite Materials. 2) The Modification In The Organic Matrix Of Resin Composite Material, Did Not Improve The Wear Resistance. 3) Load Cycling, Thermocycling, And PH Cycling Have Adverse Effects On The Mechanical And Physical Properties Of All Tested Materials.