11 & 12- fixed partial dentures + cad/cam

What is a fixed partial denture (/bridge) and its parts?

Prosthesis that replaces 1 or missing teeth- permanently attached to remaining teeth

Abutment- tooth that supports bridge

Pontic- artificial tooth suspended between abutements

Retainers- restorations (crowns) that are cemented to prepared abutments

Connector- junction between Pontic and retainer

What is the importance of dental losses in anterior area?(8)

Loss of aesthetic smile

Lip support: shrinkage

Alteration in the axes of the teeth

Midline deviation

Antagonist tooth extrusion

Alteration in phonetics

Decreased volume buccal bone plate

Gingival tissue modifications

What are 4 problems of restorations with metallic core?

High opacity

Corrosion of the chromium-nickel alloy

Decreased gingival biocompatibility

Greyish gingival margin: umbrella effect- has disadvantages and therefore other materials are used

What are 7 therapeutic options for loss of anterior teeth?

1. Scaling and cleaning

2. Obturations (many caries to treat)

3. Conventional porcelain fused metal (PFM) bridge

4. Endo-osseous implant- depends on bone availability, adjacent gingival tissues, operator ability

5. Aesthetic bridges

6. Removable prosthesis

7. Auto transplantation ??

What is the process of making a ceramic?

SINTERED or by layers/coats

• Over metal core

• Over ceramic core

• Over refractory material

▪ INJECTION OR CERAMIC CASTING

▪ MECHANIZED- done by either copying system or cad cam

How are aesthetic bridges classified by material?

1. Zirconium oxide (zirconia). NON–SILICA-BASED CERAMICS

2. Aluminium ceramics (procera all ceram)

3. Lithium disilicate

4. Modified porcelain fused metal (PFM) – has ceramic shoulders

5. Ceramic–Composite Hybrid (Resin Matrix Ceramics)

Properties of zirconium oxide (zirconia)-

polycrystalline ceramic

Composed of highly sintered zirconium oxide (95%), partially stabilized by yttrium oxide (5%)

High hardness because its microstructure is totally crystalline

Classification of zirconia?

1. Structures: only the internal structure (framework) is milled and is covered by various techniques with conventional ceramics.

2. Monolithic: the restoration is milled in its entirety.

We can only use zirconia in the framework + add conventional ceramic to do the external structure

or the whole structure can be made of monolithic zirconia

How is a bridge manufactured using CAD/CAM? (6 stages)

1. Scanning

2. Design

3. Milling

4. Colour adjustment

5. Sintered

6. Final bridge

What 3 different steps does all CAD/CAM systems consist of?

Scanner- digitalization tool that transforms geometry into digital data that can be processed by the computer

Design software- processes data, depending on the application- produces a data set for the product to be fabricated

Processing device- production technology that transforms the data set into the desired product

What materials can be used in Cad/cam?

Metals: Cobald Chrome and titanium- Precious metals cannot be machined

Ceramics such as zirconium oxide

Zirconia

Resin materials

7 Advantages of using CAD/CAM?

Digital impressions - no discomfort , no lab

No provisional restorations are needed

Single visit treatment

Natural restoration shades - as the ceramic block used allows light to pass through- gives resemblance of the patients' enamel

More precision and accuracy

Improved patient safety - as CAD/CAM systems use sculpted porcelain, avoiding the use of metal

Longer lasting restoration and esthetically pleasing - more durable

3 disadvantages of using CAD/CAM systems?

Higher cost for dentist- need optical scanner, CBCT for 3D imaging and CAD/CAM system

Higher cost for patient- 20% more than traditional resto

Need to spend time and money training courses

Why do we use monolithic zirconia over zirconium oxide?

To avoid chipping and fractures

3 Properties of aluminium ceramics?

Very opaque- use for internal structures then cover with conventional porcelains for good aesthetics

Lower flexural strength than polycrystalline

Less resistant

Lithium disilicate (ips e max) used for…, properties

Injection technique- for making bridges

Most aesthetics- has diff shades and opacities

Low flexural strength

What is modified porcelain fused metal and its advs?

Consist of bridges with a metal structure where the covering of the same on the abutment tooth ends

1.5-2mm from the chamfer, giving a more translucent porcelain margin, increasing light diffusion to the soft tissue

Greatly avoids the umbrella effect

The reduced structure does not decrease the mechanical resistance

In longer stretches with aesthetic commitment

Can be used in cases of cast metal post and core.

Shoulder ceramics with a higher melting temperature than conventional ones on metal are used

For cementing, use adhesive techniques and silanization

5 Advantages of ceramic composite hybrid (resin matrix ceramics)

Materials like“hybrid ceramics” (a mix of ceramic + resin)

Flexible → less brittle than pure ceramics

Absorb stress better (helpful in younger teeth)

Used in CAD/CAM systems for same-day crowns

Wear resistance similar to that of natural teeth

Long-lasting aesthetics: Due to its greater resistance

How do you choose the material for a fixed partial denture?

Occlusion- favourable or unfavourable

Substrate (abutment tooth)- suitable to unsuitable

What are 4 combinations to consider when selecting material for fixed partial denture?

Favourable occlusion + suitable substrate = IPS e.max, zirconia, aluminium

Favourable occlusion + unsuitable substrate = zirconia, aluminium.

Unfavourable occlusion + suitable prosthetic space = zirconia, modified PFM

Unfavourable occlusion + insufficient prosthetic space = modified PFM