Dental ceramics / orthodontic seminars

Dental ceramicsDental ceramics
Silicate ceramics and oxidceramicsSilicate ceramics and oxidceramics
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Images from KaVo Everest CAD/CAM system

Why use
ceramics
 Biocompatibility
 Aesthetics
 Durability
The biocompatability issue is essential to prevent adverse
reactions within the patients
The use of dentally coloured glasses can provide
replacement structures that can be made to imitate tooth
structure in both colour, translucency and response to
different lighting sources.
Improvements in fracture toughness, wear resistance,
machinability, solubility and flexural strength

Ceramics used in dentistry
 Fillings
 Veneering metal frameworks
 All ceramic restorations
 Denture teeth
 Implants
 Orthodontic brackets

Silicate ceramics
ESTHETICS
 Feldspathic porcelain
Veneering ceramics –
sintering
 Glass Ceramic
Castable glasses-Dicor
Pressed leucite system-
IPS Empress
Oxid ceramics
STRENGTH
 Glass infiltrated Alumina
system
In-ceram Alumina
In-Ceram Spinell
In –Ceram Zirconia
 Policrystal
ceramics:CAD/CAM
Cercon Base
DC-Zirkon
Lava Frame etc.www.indiandentalacademy.com

Glass matrix + Crystals
An overcooled
liquid
Not crystalline, but
still ordered structure
Silica tetrahedron
network
Glass modifiers
built in network
Most important crystals:
 Leucit
 Fluormica
 Aluminium
 Spinell
 Zirconia
They determin the
physicalphysical, chemicalchemical and opticaloptical
properties of the ceramics
(their composition varies in each type of ceramic)
Basic structure of dental ceramics
Two different phases built by metallic (Al,Ca, Mg, K etc) and non-metallic (Si, O,
B, F etc.) elements:

First ceramic material in dentistry
Feldspathic Porcelain:
derived from the natural mineral feldspar
 75%feldspar,22-25% quartz, 0-3% kaolin
 Feldspar:
Provides for transparency and influences the flow characteristics of the
ceramics.
 Quartz (silicon oxide):
Provides for adequate strength and also for transparency.
 Kaolin:
Provides for the necessary opaque properties.
 Fritting:-cleaning and mixing raw materials, heating, melting, sudden
cooling and grinding to fine powder
 Sintering:powder mixing with liquid, firing, powder particles stick
together
 Shrinkage:appr. 30 vol%
 Structure: leucite crystals in silica glass matrix
 Disadvantage:brittle,hard,rigidwww.indiandentalacademy.com

Image from Bego Virtual Academy
Veneering metal frameworks

Image from Bego Virtual Academywww.indiandentalacademy.com

Metal-ceramic restorations:
•Ceramic material is veneered (sintered) onto a metal
frame in several firing processes
Esthetic consideration

Veneering ceramics
 Used for the porcelain-fused-to-metal technique
 Based on modified feldspathic porcelain
 Binding oxides for metal-ceramic bond
 Leucite content:thermal expansion coeff.
 Fusing temperature 200-250 C lower than metal framework (low fusing
ceramics)
Synthetic ceramics (metal –ceramics)
No natural raw materials
Made of high purity chemicals
Tempering:guided heating process, to
form certain type, size, amount and
dispersion of crystals (micro-leucite
crystals
Standard physical, chemical and optical
properties
Standard quality
Low or ultra-low fusing temperature
Hydrothermal ceramics
• tempering and fusing in high pressure
steam
• Hydroxil ions built in glassy matrix
• Compact and homogenous structure
• Better fracture toughness and lower
hardness
• Leucite content allows veneering
frameworks
• Ultra-low fusing temp. Can be achieved
• Pure glass can be used for dental
purposes (one and only among dental
ceramics)www.indiandentalacademy.com

The bonding of ceramic
materials to alloys
follows four principles:
 Shrinking the ceramic onto the metal frame -
coefficient of thermal expansion
 Chemical bond The bond is formed by means of
oxygen bridges between the silicon atoms of the
ceramic and the metal oxides of the alloy.
 Mechanical retention is created through finishing and
blasting of the frames-surface enlargement also takes
place.
 Bonding through adhesion takes place via
intermolecular forces (VAN DER WAAL forces)www.indiandentalacademy.com

All ceramic restorations

 driving forces for developments:
 Public perception that metal-free restorations are more
aesthetic
 Disadvantages of the metal ceramic systems include
radiopacity, some questions centring around metal
biocompatibility and lack of natural aesthetics
 Difference in reliability between metal-ceramic systems
and all-ceramic systems

All ceramic restorations
Laboratory processing
 Silicate ceramics
o Sintering
o Casting
o Pressing
o CAD/CAM
 Oxidceramics
o infiltration and /or CAD/CAM technology

SinteringSintering is a method for making objects from powder, by heating the
material (below its melting point) until its particles adhere to each other
The base-material for heating ceramic on:The base-material for heating ceramic on:
- platinum foilplatinum foil (removable heat-resistant cap
from the gypsum cast)
- Heat resistant investment material madeHeat resistant investment material made
castcast
- Hydrothermal glass/ Duceram LFCHydrothermal glass/ Duceram LFC
SinteringSintering
under vacuumvacuum to prevent
porositieswww.indiandentalacademy.com

 Casting (Dicor)
CastingCasting is a process by which a
material is introduced into a mold
while it is liquid, allowed to solidify in
the shape inside the mould, and then
removed producing a fabricated
object
Cast using lost-wax investment method
followed by heat-treatment to
precipitate a crystalline phase
 Pressing (Empress)
PressedPressed ceramic technology produces
consistently precise crowns by
eliminating shrinkage, porosity and
the inconsistency of brush build-upswww.indiandentalacademy.com

Glass Ceramic
 first a glassy matrix is produced
 precursors of crystals are in glassy matrix, crystals
produced by tempering (heating),
 “bonded” to the remaining tooth structure using a dental
BisGMA based composite resin

Glass infiltration
Oxidceramics
 Glass infiltrated Alumina system
In-ceram Alumina
In-Ceram Spinell
In –Ceram Zirconia
Slip-cast slurry in porous mould-sintered
— infiltration by low viscosity glass —
veneered with more translucent
feldspathic frit
Slip-cast slurry: A fine particle ceramic dispersed in an
aqueous liquid medium is poured into a porous mould
which rapidly extracts the liquid causing the formation
of a close-packed but weak ceramic particle structure.www.indiandentalacademy.com

Polycrystal Oxid ceramics
 High strength underlying core to support veneering
porcelain which gives the final shape and aesthetic
attributes required for the restoration.
 Yttrium stabilized Zirconium -dioxide ceramics:
ZrO2 95%+ 5% Yttrium
More to come: lecture on CAD/CAM systems

Dental ceramics / orthodontic seminars

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