Dent Mater8:305-309,September,1992
Protection hypothesis for composite wear S.C. Bayne, D.F. Taylor, H.O. Heymann Department of Operatwe Dentistry, School of Dentzst~, Unwerszty of North Carohna, Chapel Hill, NC 27599-7450 USA
Abstract. SJgnrficant occlusal wearoccurson poster,orcomposite restorations in areas wfthout direct contact w~th opponent teeth (contact-free wear) in add,tton to wear at the contacts. Recent research has ,ndicated that all occlusal posterior composite surfaces wear, and those surfaces show decreas,ng wear rates over time. Thts prowdes more ewdence for an earlier theory proposed by Jorgensen etal. (1979) that composite contact-free wear ,s a funct,on of access and attritton caused by small parttcles in the food bolus. This hypothesis is now called the "protect,on theory" or "protection hypothesis" for wear Macroscopic protection or "sheltenng" from wear fs provided by cavity preparation walls. Microscop,c protection agafnst res,n matrix wear Jsprowded by filler particles that are close together. Chnical ewdence supportmg the protection hypothesis comes from recently confirmed low wear rates for mlcrofill and hybrtd composites. The objective of th,s work was to calculate the mtn,mum inter-particle spacing required for microscopic protection (wear resistance) for composites based on assumptions of packing fractions (0.68) with small particles (0.02 ~m radius) for dispersed versus agglomerated condittons An inter-particle spacing (IPS) of
Protection hypothesis for composite wear S.C. Bayne, D.F. Taylor, H.O. Heymann Department of Operatwe Dentistry, School of Dentzst~, Unwerszty of North Carohna, Chapel Hill, NC 27599-7450 USA
Abstract. SJgnrficant occlusal wearoccurson poster,orcomposite restorations in areas wfthout direct contact w~th opponent teeth (contact-free wear) in add,tton to wear at the contacts. Recent research has ,ndicated that all occlusal posterior composite surfaces wear, and those surfaces show decreas,ng wear rates over time. Thts prowdes more ewdence for an earlier theory proposed by Jorgensen etal. (1979) that composite contact-free wear ,s a funct,on of access and attritton caused by small parttcles in the food bolus. This hypothesis is now called the "protect,on theory" or "protection hypothesis" for wear Macroscopic protection or "sheltenng" from wear fs provided by cavity preparation walls. Microscop,c protection agafnst res,n matrix wear Jsprowded by filler particles that are close together. Chnical ewdence supportmg the protection hypothesis comes from recently confirmed low wear rates for mlcrofill and hybrtd composites. The objective of th,s work was to calculate the mtn,mum inter-particle spacing required for microscopic protection (wear resistance) for composites based on assumptions of packing fractions (0.68) with small particles (0.02 ~m radius) for dispersed versus agglomerated condittons An inter-particle spacing (IPS) of
