Thursday, March 28, 2019
Essay examples --
Ceramics are utilize extensively in dental restorations because of their superior aesthetics and biocompatibility compared to metals (1). However, the brittleness of ceramics can originate wisecrack propagation causing failure of the restoration (2). Resin cements are used for cementing ceramic restorations because of their excellent aesthetics and mechanical properties. The cement penetrates any defects or irregularities on the ceramic surface thitherby preventing propagation of cracks (3, 4, 5). Optimal clinical performance depends on sufficient resin cement polymerisation. Degree of renascence (DC) is affected by the amount of open reaching the cement which in turn, is affected by the opacity and the ponderousness of the ceramic as tumefy as the denselyness of the resin cement work. Insufficient polymerisation influences some(prenominal) mechanical properties and clinical performance of the restoration (2, 5). Aims of this study are to envision how light transmission ( LT) is affected by thickness or opacity of a ceramic and how resin cements thickness affects DC. Hypotheses are (1) LT decreases with increasing thickness or opacity (2) DC would decrease with thicker cement samples. Method timber A1, A2, A3 and A3.5 of Base Dentine VN7 powder (Vita, Bad Sckingen, Germany) were used. Ceramic phonograph recording thicknesses tested ( mensural using digital calliper) were 1.40, 1.00 and 0.60mm.Specimen preparationTwenty ceramics discs, quintette of each shade, were prepared by mixing 0.73g of powder with 0.29mL of Modelling silver (Vita, Bad Sckingen, Germany). The mixture was placed in a 1.60mm thick metal ring on a mould assembly and vibrated for 40 seconds. The surface was levelled using a razor blade before handout the discs in a furnace (Vita Vacumat 40, Bad Sckingen, Germ... ... the disc. LT through a ceramic disc would ultimately affect the polymerisation of resin cements. The second dead reckoning that DC should decrease with increasing resin cement thickness layer is rejected as the graph showed that 1.00mm resin cement thickness had the sterling(prenominal) DC. A higher DC was seen with thinner resin cement specimens because there would be more LT and the photoinitiator in resin cements needs light to initiate the polymerisation reaction. A thicker resin cement layer would allow little light to reach the bottom so there would be slight monomer to polymer conversion and resultantly, lower DC. However, very thin specimens may experience light reflectance which may affect the DC results. ConclusionLT through ceramics was measured and LT decreased with increasing thickness or opacity. DC appeared to increase when thicker resin cement samples were tested.