ALL CERAMIC CROWNAn extracoronal restoration covering the prepared clinical crown and restoring

ALL CERAMIC CROWN Gives superior cosmetic effect But Ceramic is a brittle substance, so more susceptible to fracture Newer development porcelain reinforced with Alumina, Dicor cast glass ceramic, Hi-ceram, In-ceram & IPS Empress

Advantages

DisadvantagesBrittle

Indications

Fractured anterior teeth

Discolored anterior teeth

Lemoncitric damage

Tetracycline discoloration

Bilateral proximal and facial decay

Realign malposed or rotated teethbefore after

Closing diastema

Contraindications when a more conservative restoration can be used.

Superior strenght is required ex: deep ,edge to edge bite.

Contraindications Short clinical crown-inadequate tooth support-half moon fracture. Patients with parafunctional habits e.g: clenching and bruxism.

Patients with High risk of fractures as contact sport athletes.

Aims of the preparation 1mm shoulder finish line providing a flat seat which resists forces. The incisal edge: 2mm reduction with 45 degree inciso-gingival bevel to provide support for the ceramic which is a brittle material. Labial aspect-------- 2 plane reduction.

Axial reduction------ 1-1.5 mm Palatal clearance- 1 mm at least

Centric contact --- limited to the middle third of the lingual surface (case selection). Opposing axial walls converge minimally with 5-10 degree taper. Roundation of all sharp line angles.

ARMAMENTARIUM High- and low-speed handpieces Flat-end tapered diamond Small wheel diamond Long needle diamond End cutting diamond Finishing stones and carbides

Incisal reduction Incisal grooves---- 2 mm Done with flat-end tapered diamond Incisal edge flat & placed 45 degree inclination toward the linguogingival area to meet forces on the incisal edge & prevent shearing

Labial reduction Depth-orientation grooves are placed on Labial Surfaces ----- to gauge the depth of preparation Labial grooves 1.2 1.4 mm 3 grooves parallel to gingival one-third. 2 grooves parallel to incisal two-third Two plane reduction to achieve good esthetics without encroaching the

pulp

Labial reduction First incisal two third preparation Then the one-third : this reduction extends around the labioproximal line angles

End of diamond point will create shoulder finish line, while axial reduction is done by sides of the diamond

palatal reduction Is done by Small Wheel or football diamond Overshortening the lingual wall will decrease the retention of the preparation palatal Axial Reduction by Flat-end tapered diamond Radial Shoulder margin (1mm)--- smooth continuation of labial & proximal shoulder

Proximal reduction Opposing proximal walls converge incisally 5-10 degrees Instrument----- tapered with flat diamond stone Depth of reduction ----- 1-1.5 mm Shoulder F.L 1 mm in depth

Avoid injury of neighbouring tooth by matrix band Enamel lip Correct direction of the handpiece

GINGIVAL FINISH LINE Shoulder (d) of uniform width (approx 1 mm) is used as a gingival finish line --- to provide flat seat to resist forces directed from the incisal area.

a) Knife edge,

b) Bevel,

c) Chamfer, d) Shoulder,

e)

Shoulder with bevel

Finishing the preparation All sharp line angles & point angles should be rounded to avoid stress concentration Smoothening is done with Diamond of fine grit Finishing burs Sandpaper discs

Principles of Tooth Preparation

Vertical palatal wall (resistance&retention)

Concave lingual reduction (structural durability)

Shoulder F.L Marginal integrity Structural durability Periodontal preservation

Axial reduction Resistance & retention Structural durability

Rounded angles Structural durability

Common errors Short preparation

Sharp incisal edge

Sharp line angles

Excessive taper

Improper long axis of the tooth preparation

Mechanics Aesthetics Preservation

Mechanics Aesthetics Preservation

Mechanics Aesthetics Preservation

Various types of all ceramic system Castable ceramic centrifugal casting (Dicor) heat pressed (Empress) Slip casting (Inceram) Machinable CAD/CAM Precision Copy Milling (Celay)

1- Castable ceramicscentrifugal casting (dicor) heat pressed ceramics Empress 2

IPS Empress

A.dicor A polycrystalline glass ceramic material

The crystalline phase is composed of tetrasilicic flouoro mica which provides strength Fabrication method uses lost wax & centrifugal tech Applied as : inlays Onlays laminate veneers crowns

B.Heat pressed ceramicsIPS Empress (leucite based pressable core) Supplied as precerammed cylinders in various shades using a high temp 1100 c they are pressed after softening into a mold made by lost wax tech and held under pressure to allow complete and accurate filling Empress restoration are translucent and have strength 160-180 Mpa

Excellent marginal adaptation

Empress 2 (Li-disilicate pressable core) Crystalline phase ---- lithium disilicate Strength------ 350 Mpa Indication: 3 units anterior premolar bridges molar crowns

2-slip casting(glass infiltration ceramics) Inceram Inceram spinell Inceram zirconia Core is strengthened by addition of zirconia to the alumina More opaque than inceram spinell Recommended for posterior bridges

Core of alumina is filled with lanthanum aluminosilicate glass One of the strongest ceramics 350-500 Mpa

2nd generation More translucent core made from magnesium alumina powder Strength 350 Mpa

3-Machinable ceramics

CAD/CAM SYSTEMpossibility to design and fabricate all ceramic restorations in a single appointment

Advantages

saving timeeliminate the possibilities of inaccuracies developed with indirect techniques Cut the chain between dental clinic and laboratory

CAD/CAM (Cerec) The dentists takes an optical impression of the preparation using an intraoral camera A design of the restoration is made from the acquired data, using the computer

The restoration is milled from a ceramic block using diamond stones by milling machine

Cerec systemsCerec I : the occlusal anatomy& contacts were developed by grinding intraorally -------- Had poor marginal fit Cerec II : the occlusal surface is also milled produce crowns,inlays,onlays & veneers Cerec III : data obtained is 3-D -------- more marginal accuracy

Procera system The die is mechanically scanned by the technician & data is send to procera lab Data is processed & enlarged 20-30 % to compensate for ceramic shrinkage Procera can produce posterior crowns & FPD due to high flexural strength 650 Mpa

B-Precision copy milling system (Celay) Precision milling machine that mills ceramic material but not computer driven. Celay machine consists of two integrated but separate components copying tool pantograph cutter A resin pattern is fabricated intraorally or on the die The replica is mounted on the scanning side & ceramic block on the milling side