LITHIUM DISILICATE PPT in dentistary non metallic crown

non metallic crown restoration lithium dislicate

1. Non METALLIC CROWN RESTORATION LITHIUM DISILICATE

2. Introduction The most common aesthetic restorative material used in day to day practice for crown and bridge work is porcelain fused to metal (PFM) because of its excellent mechanical properties In order to overcome the unaesthetic metallic hue seen in PFM restorations, dental research began to be directed towards metal-free ceramic restorations to improve the aesthetic outcome Research and development led to the creation of many metal-free ceramic systems. Non-metal  dental crowns The most popular non-metal dental crown choices are porcelain crowns and ceramic crowns. Both of these types of dental grounds are often preferred because they offer a much more natural look, which tends to be important to every dental patient. superior aesthetic outcome of metal-free ceramic restorations has led to their increasing popularity, especially in the anterior regions of the mouth .

3. LITHIUM DISILICATE Lithium disilicate (LS2) is classified as a glass-ceramic, in the class of particle-filled glass materials. Introduced on the market in the 90s with the commercial formulation named “IPS Empress 2” ( Ivoclar Vivadent , Schaan, Liechtenstein), it was composed of 65 vol% lithium disilicate , small needle-shaped crystals (3–6 μm × 0.8 μm ) embedded in a glass matrix At first, this material was made commercially available as ingots, to be utilized according to the “heat-pressing” fabrication procedure, similar to the classic “lost wax” technique for metal-alloy casts, aimed at producing cores, hot pressed into a mold. In order to get an appealing reproduction of the optical characteristics of natural teeth, the cores are lately veneered with a very translucent fluorapatite ceramic, containing 19–23% of fluorapatite crystals (Ca5(PO4)3F) embedded in a glassy matrix

4. E –max preferred for its long lasting, aesthetic qualities Crown is made from a single block of lithium disilicate ceramic. This is top grade material which has been harvested for its toughness, durability and opaque qualities which makes it a highly prized crown. Considered to be the best match with your own natural teeth No metal inside the crown so it means no gray line around the gum line. Less risk of chipping to zirconia crown. The most common reason for the ceramic to fracture is inadequate material thickness.

5. Ivoclar's recommended tooth reduction for E-max posterior crowns At least 1.5 mm occlusal reduction for cusp tips and the central groove. 1.5 mm on the axial walls circumferentially in the occlusal one-third. At least 1.0 mm deep flat shoulder margin. Chamfer or feather edge finish lines are contraindicated. Although similar in functionality with dioxide, the difference between E-max and Zirconia crowns is that E-max is more translucent than Zirconia. The translucency of E-max crowns allows in more light. This creates a more lifelike crown that requires no stain

6. Recent advances the widespread, increasing implementation of C AD-CAM technologies has led to the introduction of ceramic blocks aimed at the production of restorations by milling devices (IPS. EMax CAD), also suitable for chairside production of Restorations. Partially, pre-crystallized blocks are manufactured in a “blue state”, containing 40% of Metasilicate (Li2SiO3) in addition to lithium disilicate crystal nuclei .

7. Such blocks are characterized by moderate flexural strength of ~ 130 Mpa , resulting in higher cutting efficiency, easier and faster workability and lower wear of the milling tools. The milling procedure is performed in this pre-crystallized state and, after its completion, it is followed by a heating cycle (840°-850 °C for 10 min) that turns metasilicate crystals into lithium disilicate , increasing the flexural strength up to values, together with a fracture toughness.

8. Zirconia reinforced-Lithium silicate ceramics Enhance translucency: a glassy matrix, containing a homogeneous crystalline structure made of lithium silicate crystals, is reinforced with tetragonal zirconia fillers (10% by weight) allowing higher strength values than LS2. The higher mean translucency, together with proper biaxial flexural strength values, make such material a proper choice for minimally invasive, single tooth esthetic restorations, like inlays, onlays , partial crowns, veneers, anterior and posterior crowns, both tooth- and implant supported.

9. Conclusion: Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate . More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration. Within the limitations of the study, it can be concluded that high translucency lithium disilicate is the most translucent material amongst the materials studied lithium disilicate . Further research is needed on improving the microstructural features of zirconia materials in order to enhance their translucency.

10. Preparation

11. Cementation Of Lithium DiSilicate Veneers and Full Coverage Crowns

12. Preparation of veneer/crown surface : E tching with 5% hydrofluoric acid for 20 seconds or an alternative is 9% (such as Porcelain Etch from Ultradent ) for 90 seconds. Rinsing of the veneer surface followed by air-drying of the surface. Silane coupling agent is applied on the internal surface for 60s and air-dried.

13. Preparation of tooth surface : The teeth and the adjacent tissues are isolated. Etching of the prepared tooth is performed by application of 37% Phosphoric acid for 15s, followed by rinsing the tooth surface and air drying the surface. This is followed by application of Bonding agent( Ivoclar / Vivadent ), gentle air-drying and polymerization for 40s. Dual cure resin cement is used for luting. The excess is removed using an explorer . The luting cement is polymerized using light- emiting diode for 40s. Cement margins are finished and polished using flexible Aluminum Oxide disks