Lithium Disilicate

lithium disilicate

type of glass ceramic that can be layered or monolithic
- can be milled or pressed
- flexural strength of 360-400 MPa
- esthetics (light reflection + scattering)
- composition = quartz, lithium dioxide, phosphor oxide, alumina, potassium oxide

360-400 MPa

what is the flexural strength of lithium disilcate

aluminum oxide

what minimizes chemically solubility in lithium disilicate

potassium oxide

what lowers the viscosity in lithium disilicate

phosphorous pentoxide

what is the nucleating agent and helps in bulk crystallization process in lithium disilicate

zinc oxide

what improve chemical stability + optical translucency in lithium disilicate

magnesium oxide

what increase the viscosity of glass matrix in lithium disilicate

ingots

round cylinders of lithium disilicate

pressed lithium disilicate

produced according to a unique bulk casting production process to create the ignots

microstructure consists of ~70% needle like lithium disilicate crystals embedded in a glass matrix, 3-6 microns in length

pressed technique (ignots)

utilizes in lost-wax hot-pressing technique in which lithium metasilicate in ingots are converted to lithium disilicate

ingot pressed into mold at 850C for 20-25 minutes to form 70% volume of crystalline lithium disilicate

heat-pressed technique must be done in a lab (> manufacturing time + technical skills)

press furnace

machine where you insert the ingot and plunger in into investment after preheating it

computer-aided design + computer-assisted manufacturing

what does CAD-CAM stand for

milling

fabrication process that used CAD-CAM technology charge-coupled camera device to make a 3D impression of the tooth + crown is designed --> block altered based on digital info

40%

what volume % of crystals are embedded in a glass matrix (mostly lithium metasilicate, small amount of lithium orthophosphate and lithium disilicate) of a non-fired blue block

milled LD

require intermediate crystallization to ensure blocks can be milled efficiently in an intermediate bleu phase

intermediate process leads to formation of lithium metasilicate crystals --> 40% embedded in glass, 0.2-1 microns, flexural strength 130 MPa

130 MPa

what is the flexural strength of milled LD

70%

what is the crystal microstructure percentage of fine grained lithium disilicate in milled LD after crystallization (after firing)

blue

what is the color of the intermediate crystalline stage of a lithium disilicate block

pressed

what produces larger, stronger crystals for LD

milled

what produces shorter, weaker crystals for LD

veneers
inlays, onlays, overlays
single crowns in anterior + posterior areas
3 unit bridges in anterior + premolar areas

what are some indications for LD

very deep subgingival preparation
4 units or multiple unit bridges
patients with severely reduced residual dentition
parafuncction (bruxism)

what are some contraindications for LD

conventional + digital impression techniques
adhesive, self-adhesive, or conventional cementation options
high esthetics (mimic shade of natural tooth)
wide range of indications
biocompatiblity, less plaque accumulation
can be intraorally repaired in case of chipping

what are some advantages of LD

most difficult to machine among glass ceramics for intra-oral adjustments
thermal processing can influence strength of LD
intrinsic brittle behavior
superficial wear of LD sensitive to environmental pH
lack of literature discussing long-term survival + outcomes

what are some disadvantages of LD

2mm

what is the incisal reduction for #9 LD prep

1.0-1.2mm

what is the lingual fossa reduction for #9 LD prep

1.0mm

what is the lingual cervical reduction for #9 LD prep

1.0mm

what is the facial cervical reduction for #9 LD prep

1.0-1.5 mm

what is the incisal facial reduction for #9 LD prep

856-016 + football bur

what burs do you use for the #9 LD prep

3-5 degree taper

what is the taper of the axial walls of a #9 LD prep

2-3mm

what height should you maintain on the lingual cervical wall of your #9 LD prep

Ferrule effect

1.5 - 2 mm of tooth structure is sufficient to ensure the transmission of the forces of mastication to both post and tooth.

ferrule

a metal cap or band placed on a wooden pole to prevent splitting or wearing

dental ferrule

a band that encircles the external dimension of tooth structure

1.0mm

how wide should your uniform rounded shoulder be for your #9 LD prep

zirconium oxide

nucleating agents and helps promote surface crystallization in LD