In vitro wear rates of materials under different loads and varying pH.
BACKGROUND
Despite the need for information about the wear characteristics of restorative materials, there have been few systemic studies of the factors that influence the rate of material wear.


OBJECTIVE
This study compared the wear rates of enamel and 3 tooth-colored restorative materials under different loads (0, 3.2, 6.7, and 9.95 kg) and pH levels (1.2, 3.3, and 7.0).


METHODS
An electromechanical tooth wear machine was used so that standard restorations representing 3 materials could be worn by opposing enamel under controlled conditions. The wear rates of enamel, composite (Z100), a conventional glass ionomer cement (Fuji IX), and a resin-modified glass ionomer cement (Fuji II LC) were compared at a range of loads (0 to 9.95 kg) and pH levels (1.2 to 7.0) and also at different sites across each restoration. Ten specimens were randomly assigned to each experimental group. Wear assessment was performed with a modified light microscope to quantify the height changes at defined points across wear facets. Four-way analysis of variance was used to compare wear rates among materials, pH levels, loads, and sites. Post-hoc t tests identified significant differences between specific pairs of experimental conditions (P<.05).


RESULTS
The wear rates of enamel and the other test materials varied significantly with pH (P<.0001), load (P<.0001), and type of material (P<.0001). Enamel wear was influenced most by varied pH, whereas the composite was least affected by acid. The conventional glass ionomer cement was more susceptible than the composite to the effects of varied pH; the acid susceptibility of the resin-modified glass ionomer cement was generally between that of the composite and conventional glass ionomer cement. Enamel and the conventional glass ionomer cement were affected similarly by load. The composite was more resistant than the conventional glass ionomer cement to wear at higher loads; the resin-modified glass ionomer cement exhibited intermediate load resistance.


CONCLUSIONS
Within the limitations of this study, the 3 test materials were more resistant than enamel to acid, with the composite demonstrating the lowest susceptibility to acid. The acid- and load-resistance of the resin-modified glass ionomer cement was consistently less than that of the composite and greater than that of the conventional glass ionomer cement.
Shabanian
Mitra
M
Dental School, University of Adelaide, Adelaide, SA, Australia. mitra.shabanian@adelaide.edu.au
Richards
Lindsay C
LC
D000085:Acetates / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry; D003743:Dental Enamel / Q000502:physiology / Q000648:ultrastructure; D003764:Dental Materials / Q000737:chemistry*; D019554:Dental Restoration Wear; D003793:Dental Restoration, Permanent; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D016555:Matched-Pair Analysis; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D012822:Silicon Dioxide; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D019217:Tooth Attrition / Q000473:pathology / Q000503:physiopathology; D014867:Water / Q000737:chemistry; D016474:Weight-Bearing; D015040:Zirconium
D000085:Acetates; D003188:Composite Resins; D003764:Dental Materials; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; D019279:Resin Cements; D012117:Resins, Synthetic; C083568:Z100 composite resin; C110713:fuji IX; D014867:Water; D012822:Silicon Dioxide; D015040:Zirconium; D006851:Hydrochloric Acid