| Objective: The purpose of this in vitro study was toevaluate and compare the wear of Au-Pu alloy, four kinds ofdental ceramics widely used in clinical and natural enamel. Thevolume loss of the tested materials as well as natural enamel andopposing steatites were measured to compare the wearproperties and the wear to natural tooth. The wear mechanismswere discussed to provide experimental reference for selectingproper restorative materials to protect opposing natural enamelin clinical.Methods: 1.Specimen preparation: PMMA (polymethylmethacrylate) dies simulating crown core were producedaccording to the standard of the pin-on-plate two-body wearmachine. Four kinds of ceramics: SHOFU, D.SIGN,hydrothermal low-fusing ceramic, nanoceramic and Au-Pu alloywere fabricated into twenty-five uniform specimens, fivespecimens in each group, from group A to E. The occlusal areaof each specimen was a square of 8.0×8.0mm, which wasparallel with the bottom of the die. All the procedures werecarried out according to the manufactures, recommendations. 2.Five recently extracted maxillary third molar of adults wereembedded in PMMA as a control group (group F), remaining8.0×8.0mm occlusal area of enamel which was parallel with thebottom of the die.3.Thirty steatites were fabricated into discswith the diameter of 25mm and thickness of 2.0mm to act ascountersample materials. 4. The wear test was carried out inartifical saliva to simulate the oral environment. Each specimenwas tested under a standard load (40N), rate (80 cycles/minute),and for 25,000 cycles totally. 5. The mass loss of each specimenand the opposing steatite were weight by an electric balance(weight to a precision of 0.0001g), and the density of eachspecimen was tested by the method of measuring the mass andvolume of prepared standard specimen. The volume loss of thespecimen and opposing steatite were calculated by the mass lossand density.6. The volume loss of the materials and opposingsteatites were analyzed by SPSS11.5 and the difference wascompared. 7. Scanning electron microscope (SEM) was used toanalyze the microstructures of the wear surface of specimensand the wear mechanism was discussed.Results: 1.The volume loss of specimens from group A togroup F was: group A 6.0508±1.0416mm-3, group B7.0769±1.2517mm-3, group C 11.8146±2.2163mm-3,group D16.3134±1.9581mm-3,group E 5.1781±0.4470mm-3,group F19.3886±2.2223mm-3.The ranking of the volume loss of fiverestorative materials and enamel from the least to the most was:group E, group A, group B, group C, group D, group F. GroupE was the least, no significant difference was found amonggroup A, group B and group E (P>0.05). Significant differencewas found between group E and the other groups (P<0.01). Thevolume loss of Au-Pd alloy, SHOFU and D.SIGN were notstatistically different. Group F was the most, significantdifference was found between group F and all the other groups(P<0.01). The volume loss of natural tooth was significantlymore than the tested materials. Among group C and other groups,group D and other groups, significant differences were found(P<0.01). In each group, the volume loss of the restorativematerials was less than the group of natural tooth, the volumeloss of the nanoceramic was the most, followed by hydrothermallow-fusing ceramic, and Au-Pd alloy, SHOFU, D.SIGN werethe least.2.The volume loss of the steatites caused by thespecimens: group A 28.9235±0.6964mm-3, group B25.0444±0.8720mm-3, group C 21.5066±1.0202mm-3, group D20.3886±0.9732mm-3, group E 18.9756±0.3359 mm-3, group F17.7183±1.1671mm-3.The ranking of volume loss of the steatitecaused by the material from the least to the most was: group F,group E, group D, group C, group B, group A. Group F was theleast, difference was found between group F and all the othergroups (P<0.05). The volume loss of steatite caused by naturaltooth was significantly less than the tested materials. Group Awas the most, significant difference was found between group Aand all the other groups (P<0.01). The volume loss of steatitecaused by SHOFU was significantly more than the othermaterials. No significant difference was found between group Cand group D. Among group C and other groups, significantdifference were found (P<0.01). Difference was found betweengroup D and group A, B, E, F (P<0.05).The volume loss of thenatrual tooth and the oppoing steatite was not siginificantlydifferent (P>0.05). The volume loss of steatite caused by Au-Pdalloy was significantly more than natural tooth but less than theother materials. Among the five restorative materials, Au-Pdalloy created the least wear, followed by nanoceramic andhydrothermal low-fusing ceramic, and the group of SHOFU wasthe most.3. The result of scanning electron micrograph (SEM):In group A, the scars and big cracks were obvious, abrasivebrittle chipping fractures and many protuberances exposed, andthe surface was rough. In group B, the surface exhibited rougherand wider scars than group A. Abrasive pores with irregularshapes and large cracks could obviously be seen. In group C,thescars were not obvious and the surface was homogeneous, smallpores with regular shapes were occasionally seen, while smallcracks and large pores were scarcely seen.In group D, Thesurface showed fine grain of crystal sizes and homogeneousstructure; small pores with regular shapes scatteredly distributedwere visible. Large cracks could not be seen and the lacuna wasfew. In group E, the wear surface showed homogeneousmicrostructure, and the scars were not obvious. Fewprotuberances in the scars were occasionally seen.Conclusions: Under the condition of this study thefollowing conclusions could be drown: 1. The five materialswere more resistant to wear than natrual tooth. Au-Pd alloy,... |
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