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ePaper created 2017-09-29, 09:04:12 | version 1.38.0
literature review _ CAD/CAM material and systems dent) and Paradigm C that according to the man- ufacturer (3M ESPE) is a 30 to 45 percent leucite reinforced glass ceramic with a fine particle size.10 To overcome aesthetic problems of most CAD/CAM blocks having a monochromatic res- toration, a dif ferent version was developed as a multicoloured ceramic block, which was called VITA TriLuxe (Vident) and also IPS Empress CAD Multiblock; the base of the block is a dark opaque layer, while the outer layer is more translucent; the CAD software allows the clinician to position or align the restoration into the block for the de- sired outcome of the restoration.11,12 In 2014, the Enamic (VITA) material was re- leased as a ceramic network infiltrated with a re- inforcing polymer network that has the benefits of a ceramic and resin in one material, but no clinical data are available.14 _Alumina-based ceramics Alumina blocks (Vitablocs In-Ceram Alumi- na, VITA) are available for milling with the CEREC system (Sirona Dental) and now compatible with other milling machines as well. Due to the opacity of alumina-based ceramic materials, the In-Ceram Spinell (VITA) blocks were developed as an alterna- tive for anterior aesthetic restorations; it is a mix- ture of alumina and magnesia. Its flexural strength is less than In-Ceram Alumina, but veneering with feldspathic porcelain for a more aesthetic result could follow it after the milling process.14,15 Nobel Biocare developed Procera material; for its fabrication high purity aluminum oxide is compacted onto an enlarged die that is fabricated from the scanned data.16 The enlarged fabricated core shrinks to the dimensions of the working die when sintered at 1,550 °C; this material offers a very high strength core for all-ceramic resto- rations; the crown is finished with the application of feldspathic por celain.17 More recently, In-Co- ris AL (Sirona Dental) has been introduced as a high-strength aluminum oxide block with similar mechanical properties as Procera.18 Fig. 1 Fig. 1_Number of steps comparison between traditional methods of all- ceramic restorations and CAD/CAM restorations. _Lithium disilicate Lithium disilicate is composed of quartz, lith- ium dioxide, phosphor oxide, alumina, potassi- um oxide and other components. According to Saint-Jean (2014) the crystallisation of lithium disilicate is hetero genous and can be achieved through a two or three stage process depend- ing if the glass ceramic is intended to be used as a mill block (e-max CAD) or as a press ingot (e-max press). Lithium disilicate blocks (Fig. 3) are partially sintered and relatively soft; they are easier to mill and form to the desired res- toration compared to fully sintered blocks; af- ter this process the material is usually heated to Fig. 2 Fig. 2_Vita Mark II block. Fig. 3 Fig. 3_In-house milled crown from an E-max block. 2_2017 17