9 & 10- dental ceramic materials

Advantages of ceramics

Excellent aesthetics- good translucent and texture

Biocompatible- non toxic, well tolerated by tissues, minimal allergy compared to metals

Colour stability- resistant to staining and discolouration overtime

High compressive strength- good for load bearing areas

Chemical stability- resistant to corrosion and oral fluids

Low thermal conductivity- protects pulp form temp changes

5 Disadvantages of ceramics

Brittle- low tensile stress- prone to fracture under stress

Technique sensitive

Wears (abrasive to) opposing teeth

Difficult repair

Costly

How can dental ceramics be classified?

Type

Use- denture teeth, metal-ceramics, veneers, inlays, crowns, anterior bridges

Processing method- sintering, casting or machining

Substructure material- cast metal, staged metal, glass ceramic, CAD-CAM, sintered core

Compared to metal ceramics, what are the advantages of all ceramic restorations?(7)

Increased translucency

Improved fluorescence

Greater contribution of color from the underlying tooth structure

Inertness

Biocompatibility

Resistance to corrosion

Low temperature / electrical conductivity

Why do all new types of ceramic have a lower incidence of fracture?(3)

All ceramic restos made of stronger materials + better fabrication

Can be etched and bonded to underlying tooth with new dentin adhesives

Greater reduction means thicker and stronger resto

How can ceramics be classified based on composition?

• Glass-based Ceramics

Feldspathic porcelain

Leucite-reinforced ceramics

Lithium disilicate

• Glass-infiltrated Ceramics

In-Ceram (alumina-based)

• Polycrystalline Ceramics

Zirconia

Alumina

Indications of ceramics?

Anterior Restorations- veneers, crowns

Posterior Crowns- esp with high-strength ceramics like zirconia

Inlays and Onlays- Conservative restorations with good esthetics

Fixed Partial Dentures (Bridges)- Short-span bridges using high-strength ceramics

Implant-supported Prostheses- Zirconia frameworks for implants

Full-mouth Rehabilitation- need esthetics and durability

Contraindications for ceramics?

Parafunctional Habits- Bruxism increases fracture risk

Limited Tooth Structure- Insufficient support may lead to failure

Poor Oral Hygiene- Risk of secondary caries and restoration failure

Deep Subgingival Margins- Difficult bonding and isolation

Heavy Occlusal Forces- May lead to fracture, especially in weaker ceramics

Types of full ceramic crown and their pros vs cons?

Feldspathic- very aesthetic but weaker

Lithium disilicate- good balance of aesthetics and strength

Zirconia- very strong, for posteriors

What are the advantages vs disadvantages of shoulder margin on ceramics and how can you reduce the fracture index?

Very aesthetic, risk of fracture during cementation, use limited to vestibular area of anterior teeth

Need special shoulder, costly

Do perfect impression and tooth prep, avoid using in posteriors, not for bridges, use cemented adhesive

Advantages of ceramic veneers

Colour- stable better control and natural

Bond strength- strong bond between etched veneer to enamel

Periodontal health- glazed surface- less plaque acc

Resistant to abrasion

Strong

Resistant to fluid adsorption

What is the umbrella effect and how can we avoid it?

The lip acts as a umbrella- can see raised margin and dark interdental papilla due to shadow

In veneres- light reflected so avoids it

Disadvantages of ceramic veneers

Time consuming

Repair difficult once luted to enamel

Technique sensitive- indirect

Colour- can’t modify once luted

Need tooth prep

Fragile

Indications of ceramic veneers?

Discoloration- Due to fluorosis, tetracycline staining

Enamel defects- types of enamel hypoplasias and hypocalcification

Diastema- can close

Malpositioned teeth- The esthetic illusion of straight teeth can be developed

Malocclusion- The configuration of lingual surfaces of anterior teeth can be changed to develop incisal guidance or centric holding in malocclusions or periodontally compromised teeth.

Poor restorations

Aging- mask color changes

Wear patterns

Contraindications of ceramic veneers

Need enough available enamel- if tooth mainly dentin and cementum use crowns

Inability to etch enamel- temp teeth or excess fluoride

Oral habits- bruxism or biting foreign objects

3 types of veneer prep

Not exceed incisal edge (contact lens)

Exceeds incisal edge (classic type)

Widely exceeds incisal edge (three quarter type)

What should you consider when doing veneer prep on premolars?

Avoid positioning the contact point of the antagonist directly over the junction between the ceramic veneer and the natural tooth

Advantages of incisal reduction compared to contact lens type?

Reduces angular fractures: thicker ceramic

Greater aesthetics

Allows to change the shape of the teeth

Facilitates changes in dental position

Facilitates the manipulation and cementation of the veneers.

Allows the margin to be placed outside the occlusal impact area (main point)

What’s the name of the bur and when do we use it?

Veneer depth cutting bur for vestibular preparation

Types of retraction cord- disadvantage?

Normal black cord fine thickness, second yellow cord– has to be removed when putting second light silicone in the sulcus

Need someone to help you remove the cord while you pour the silicone

Have to use at least 1 retraction cord

What’s the main problem caused by mixing clay based material with an astringent ?

retraction may not be sufficient and uniform around the tooth- problems with impression material tearing or difficulties reading the margins in the lab

Non cord method- clay based material mixed with astringent (paste) and injected into sulcus

What other non cord method can be used for surgical retraction and their disadvantage?

Laser, trimming bur, electrocautery or radio frequency device- leaves troughs around tooth

May need firmer tissue ablation for hemostasis

But cause trauma to gingiva- may not return to og state

How to bond veneers/prep veneers for bond?

Remove provisional and clean tooth

Try in

Clean and dry veneer- 9.6% hydrofluoric acid 2 mins

Orthophosphoric acid 20secs to clean

Apply silane agent inside veneer for 1 min and dry

Place matrix in interproximal

How do you prep en ale and dentin for a veneer?

Etch 37% orthophosphoric acid 30secs in enamel, 2-secs dentin - wash + dry

Apply dentin adhesive- lightly dry

Place cement on veneer and place

Polymerise each surface for 1 min

Pass floss interdentalkg