Session 7: Ceramics; Cutting/Polishing/Abrasives

What is Finishing

For occlusal adjustment & anatomy

Improve marginal adaptation

Removing overhangs, sharp edges, roughness

Removing excess material, adjust contours + smoothen rough surfaces

What is Polishing

Smooth surface to a point of high gloss or lusture

Enhance surface, smoothen + shine to reduce plaque accumulation and staining

What is the goal at the end of restorative procedures

TARGET = make restoration as smooth as enamel

What is the objective of finishing + polishing

Reduce plaque accumulation

• Smooth surface accumulate less plaque

Provide more comfort to pt

• Restorations should feel similar to enamel

Reduce tarnish + corrosion

• Amalgam/metal…polishing removes peroxides

Improve aesthetics

Increase biocompatibility with surrounding tissue

• Pt irritation from restoration rubbing on B mucosal

Finishing & polishing with Burs

Fine vs. ultrafine diamond burs

Finishing and polishing- metal burrs

Finishing and polishing - rubber burrs

Paste for polishing

Should you keep replacing restorations

The more you replace restorations, the more harmful it is because you are removing more dental tissue

So sometimes it is possible to just smoothen and polish it!

Abrasive streps

Coarse, neutral, fine —> used for both finishing and polishing

There is…

1. Metal-backed strips

   • Situation where tight proximal contacts are involved

   • Useful for ceramics, metals, amalgams, resin composite

   • More $$$

2. Plastic-backed strips

   • Used primarily for resin-composite, compomers, hybrid ionomers, and resin cements

Resin Composite Finishing

Blades

Carbide burs 12 or 16 fluted

Fine diamond burs (24-45um particle size)

Extra fine diamond burs (15-30um particle size)

Abrasive discs + strips (coarse & medium grit)

Resin composite polishing

Carbide burs 20-30 fluted

Abrasive discs + strips (fine & extra-fine grit)

Impregnated rubber wheels, points, cups ( fine & extra-fine)

Felt discs/points combined with polishing paste (alumina or diamond)

Amalgam Finishing & Polishing

Abrasive particles —> SMALLER

Amalgam finishing burs = slow-speed handpiece

Abrasive-impregnated rubber cups & points (brown, green, blue <fine>)

Pumice in water applied with rotary brush

Tin oxide in water/alcohol applied with rotary brush or felt wheel

What is super important for amalgam finishing and polishing?

Using an abundance of water/air (lubricant) cooling & intermittent contact with amalgam

Prevent excessive generation of heat

Finishing and polishing - amalgam vs composite

Important for finishing and polishing

Use descending abrasiveness order

• Coarse —> Medium —> Fine

Rinse b/w different abrasives

• Residues can stay on restoration so RINSE

Use cooling agent

***Refurbishing restorations= part of minimally invasive dentistry

Dental Ceramics (WHERE THE LECTURE SPLITS)

Crystalline composite material, with superior aesthetics & properties adequate to replace natural dental structures

Currently material of choice for fixed prothesis (crowns & bridges) in diff forms of presentation & combination of other materials

Classification of Dental Ceramics

By application

• Metal-ceramic crowns & fixed partial prosthesis

• All ceramic crowns, inlays, onlays, veneers, fixed partial prostheses

By fabrication method

• Sintering —> process of firing compacted ceramic powder @ high temp

• Slip-casting —> “slip” = aqueous slurry of ceramic particles

• Heat-pressed —> external pressure @ high temperature to sinter + shape ceramic

• CAD/CAM machining —> restorations milled from ceramic blocks

• COMBO OF ABOVE TECHNIQUES

By crystalline phase

• Depending on nature + amnt of crystalline phase & porosity present, mechanical + optical properties of dental ceramics vary

• Increasing crystalline phase=increase resistance to crack propagation, decrease translucency

  • Some can have more glass, more esthetic, less strong

  • Some can have more crystals

    • Dental ceramics do not have a single composition—some are highly glassy for esthetics, while others have crystalline reinforcement for strength.

      The term "crystalline composite materials" refers to ceramics that have crystals embedded in a glass matrix, making them tougher while still being categorized as ceramics.

Metal Ceramic

Stil widely used

• Colour stable

• Tissue-friendly

• Biologically inert

• Chemically durable

**Survival rate of multiunit metal-ceramic fixed prostheses=considerably higher than all-ceramic systems

Metal-ceramic full coverage

Metal ceramic partial coverage

All-ceramic restorations

NO metal as infrastructure…ceramic MUST be stronger

Material for this purpose use wide variety of crystalline phases

• Materials for crowns, bridges etc. use different types of crystals as reinforcement and can be made up of up to 99% crystals.

  The type, amount, and size of these crystals affect how strong and how natural-looking the material is

All-ceramic restorations types

Sintered All-Ceramics

• Alumina-Based Ceramic

• Leucite-Reinforced Ceramic

Heat-Pressed All-Ceramics

• Leucite-Based Ceramic

• Lithium Disilicate-Based Ceramic

Slip-Cast All-Ceramics

• Alumina and Spinel-Based Ceramic

• Zirconia-Toughened Alumina Ceramic

Machinable All-ceramics

• Hard Machining

• Soft Machining followed by sintering

Lithium discilicate-based ceramic

Inlays, onlays, and veneers

Single-unit anterior & posterior crowns

Short-span anterior fixed prostheses

Lithium disciliate-based ceramic

Alumina-Based Slip-Cast Ceramic

Indication: Singe-units and anterior short-span fixed partial prostheses

Machinable All-Ceramics

For veneers, inlays, onlays, crowns, fixed partial prostheses

Using CAD/CAM technology (Computer Aided Design/Computer Aided Manufactured)

Produce resotrations in 1 office visit=possible

Preparation=optically scanned, designed & machined from ceramic block

How do all-ceramic restorations with the machine work