IM0410

I research _ dental surfaces _Cerabien—alumina framework specific porce- lain (Noritake™)—“C” in results tables and graphs. _Willi Geller Creation AV—for use with alu- minium oxide cores, InCeram Spinell and InCe- ramZirconiacorematerial(JensenIndustries™) —“J” in results tables and graphs. _VITA Alpha 900 – alumina specific porcelain (VITA Zahnfabrik™)—“V” in results tables and graphs. The test porcelains in Groups 1 and 2 (CZR Cerabien and Cerabien) are both designated “C”. Most porcelain systems have enamel porcelain as the final layer when fabricating a crown. However, Noritake™hasdesignedtheCZRCerabienandCer- abien systems to use a second distinct layer of su- per-fine particle sized enamel porcelain on top of the basic enamel porcelain in an attempt to im- prove the wear characteristics of the restoration. This layer is called the Luster porcelain. It is not an over-glaze. The rational behind the development oftheLusterporcelainisthattheglassparticlesize is more important than the hardness of the porce- lain in determining the wear characteristics of the material. The Luster layer utilized in both the CZR Cerabien and Cerabien is the same material form- ing the final surface finish of the restoration. For this reason only one set of test samples was fabri- cated from the Luster porcelain. The results pro- duced by the wear study would apply to both porcelains as the Luster layer undergoes any and all surface treatments. Therefore, the designation “C”isgiventoboththeCZRCerabien(zirconiaspe- cific) and Cerabien (aluminous) porcelains. The polished surface treatment was the only surface treatment that the dental porcelains and the zir- conia core material experienced so only this data will be presented here. The type IV gold control sample was polished to high shine finish using goldpolishingcompoundsandabuffingwheelat- tachedtoapolishinglathe.Aproprietarypolishing system (Dialite®) was used to polish the porcelain and zirconia samples. The system consists of a se- ries of colour coded, diamond impregnated, abra- sive wheels of increasing fineness, blue—course, red—intermediate, grey—extra-fine. Once the Di- alite® polishing sequence was completed a final polishwascarriedoutusing1microngritdiamond polishing paste (Ultradent™) and a flannel cloth wheel (Brasseler™). A motor driven wear machine was fabricated to simulate the accelerated wear of human enamel against various surfaces (Fig. 4). The wear machine consistedofavariablespeedmotorconnectedtoa rotating drum by a belt driven bearing assembly throughwhichaseriesofabraderrods,ontowhich the enamel samples were attached, could be fed. The test sample blocks were positioned beneath the rotating drum within a water bath. The water bathcontainedasolutionconsistingof50%Glyc- erine and 50 % Ethanol which was also the storage medium used to preserve the enamel samples. Theabraderrodswereheldinpositionbyahold- ing sleeve that passed through the rotating drum parallel to the rotational axis of the drum but off centre. This resulted in the abrader rods producing acircularpathofmotionwithaninnerdiameterof 7 mm and a maximum outer diameter of 12 mm. The variable speed motor allowed the wear ma- chine to run at a frequency of 0–100 rpm. All test sampleswererunatafrequencyof65rpm.A500 g external load was applied to each enamel abrader samplebymeansofaweightplacedontheabrader rod and all samples were run for a total of 10,000 cycles(Figs.5&6).Newlyextracted,cariesfreehu- man third molars were used to obtain adequate enamel specimens. All teeth were stored in a solu- tion consisting of 50 % Glycerine and 50 % Ethyl alcohol to avoid desiccation and maintain enamel integrity. A trephine bur (used to biopsy bone) was used to score the enamel surface to aid cutting samples of similar dimensions. All cutting was completedwithhigh-speeddiamondburswithco- piousirrigationtopreventoverheatingtheenamel and desiccating the samples. The enamel was cut into 3 mm diameter cylinders that extended at least 5 mm into dentine and placed in the storage medium.Theenamelcylinderwasthenattachedto the reference end of an abrader rod with a small drop of cyanoacrylate resin and reinforced with polymethyl methacrylate resin (Fig. 7). The dentine side of the enamel sample was pressed against the flat end of the abrader rod leaving the enamel exposed to wear. All enamel measurements (Fig. 8) were made using a digital travelling micrometer (Mitutoyo™) accurate to 0.001 mm as follows. At the reference end of each abrader rod a fine line was scribed around the cir- cumference of, and 10 mm from the end of, the abraderrod.Asecondsetoflineswerethenscribed parallel to the long axis of each abrader rod bisect- ing the initial scribe line at 90 intervals to produce four cross-hair marks. One of the cross hair marks had a further “dot-mark” placed and this was des- ignated “reference position 1” (Fig. 8). Measure- ments of enamel length were made from each ref- erence position to the edge of the enamel with the digital travelling micrometer. The arithmetic mean of these four readings per samplewastakentobetheoverallsamplelength.By subtracting the post wear measurement from the 16 I implants4_2010 Fig. 10