Use of Dental Cements Luting agent = cement Pulp protection = liner or base Temporary restoration Caries control Cavity sealer = varnish Dentin bonding agent
Chemistry of Dental Cements Dental cements are typically a powder/liquid system The liquid is an acid The powder is a base Powder must be insoluble in oral fluids but reactive with acid
Composition of powder Two materials used to make powders for dental cements: Zinc oxide Powdered glass
Zinc oxide The only insoluble, nontoxic, reactive oxide or hydroxide to react w/an acid Common additives are aluminum oxide and magnesium oxide Has some antibacterial effects Reactivity is controlled by manufacturing process
Powdered Glass The chemical form- silicon oxide - is very un- reactive When oxides of sodium, calcium and potassium are added in sufficient quantities, the glass will react with strong acid. Made of small translucent glass particles Contains fluoride to reduce melting temp, improve flow of molten glass, and gives cement ability to release fluoride. Reactivity is determined by composition of glass.
Dental cement liquids Composition or strength of acid determines reactivity of the cement liquid. Composition is controlled by the manufacturer Liquids used in dental cements include: Eugenol Phosphoric acid Polyacrylic acid
Eugenol Organic liquid- weak acid Major component of oil of cloves Derived from phenol Antibacterial Obtundant -- reduces irritation to pulp Inhibits free radical polymerization Inhibits setting of composite restorative materials Ethoxybenzoic acid (organic liquid) added to formulate cements.
Phosphoric acid Used as 2/3 acid and 1/3 water Very acidic and irritating to tissue Amount of water present affects reactivity of liquid by affecting ionization. Different levels of humidity affect it
Polyacrylic acid Aqueous solutions 30-50% polyacrylic acid by weight Very viscous liquid Dispensing Must be very accurate – independent drops important Do not dispense liquid until ready to mix cement Do not store in refrigerator Carboxyl groups bond to calcium in tooth Water hardening cements Zinc oxide or glass powder mixed with anhydrous polyacrylic acid Combined powder mixed with companion liquid (mostly water) Polyacrylic acid dissolves in water then reacts with ZO or glass
Dental cements Combine one of the three cement liquids… Eugenol Phosphoric acid Polyacrylic acid With one of the two powders Zinc oxide powder Glass powder
Most commonly used Calcium hydroxide Used as a base/liner under restorations in deep preps Used as for pulp capping Zinc phosphate Used to lute restorations, ortho bands – also used as a base material under restorations Zinc oxide-eugenol (ZOE) Chalky and white, used when not concerned with aesthetics. Obtundant – kind to pulp Glass ionomer Used for thermal insulation under restorations, luting agent
Zinc Phosphate Cement A.Use 1. Lute inlays, crowns, bridges, ortho brackets, etc. 2. Also used as a base material under restorations. B. Related Information When the powder and liquid are mixed, an exothermic (heat-releasing) reaction occurs. To dissipate the heat of this reaction: 1. A large portion of the glass slab must be used during mixing. 2. The powder must be added in small increments. 3. The mixing time must extend to 1.5 to 2 minutes.
Zinc Phosphate Mixing Set up time is 5-9 min. Add powder to liquid in small increments Zinc phosphate cement/base material
Measure the powder Measure the liquid “fluff powder” Fill scoop; do not pack Divide powder into several small increments Hold bottle vertically Dispense correct # of drops of liquid Mixing for luting consistency Add powder in small increments Should stretch ½ inch
Glass ionomer A. Use 1. Base, luting agent, restorative material 2. Thermal insulating material in deep preps B. Characteristics 1. High strength, low solubility 2. Kind to pulp 3. Chemically bond to tooth structure; release fluoride C. Dispensing systems 1. Powder/liquid systems 2. Disposable capsules – mixed in amalgamator 3. Paste/paste systems
Higher power/liquid ratio Mix Measured in same manner Setting time is ~ 7 min. Mixing time between seconds Add about ½ the powder at first, then the rest Mix is determined by ratio set by manufacturer, not “feel” Clean up with soap and water before cement sets Mixing for base or luting
Liners Used to protect pulp from chemical irritation Stimulate dentin formation or release fluoride Considerations: Do not provide thermal insulation (too thin) Too weak to support restorative materials or condensation forces (dental amalgam) Once used under composites to prevent irritation- not much anymore
Calcium hydroxide liners and bases Promote the formation of secondary dentin Comes as paste/paste system One is calcium hydroxide, one is salicylate. Titanium oxide is an added filter Setting reaction is accelerated by water Sets very quickly on moist dentin
Dycal (Calcium Hydroxide) A. Use Calcium hydroxide may be used in pulp capping and as a base/liner under other dental restorative materials in deep preparations. B. Protective Properties Calcium hydroxide serves as a protective barrier between tooth tissues (dentin and pulp) and acid-containing cements and restorative materials. C. Measuring Dispense small, but equal, amounts on a paper mixing pad D. Mixing Mix thoroughly with the crook of a small, ball-pointed instrument until a uniform color is achieved Mixing should be completed within 10 seconds.
Calcium Hydroxide, con’t E. Application Use the tip of the ball-pointed instrument to place the mixed material on the floor of the cavity preparation. Avoid placing the mixed material on walls and margins, and avoid placing it in large amounts. F. Setting The setting time of mixed calcium hydroxide is 2 to 3 minutes on the mixing pad at normal room temperature. The setting time for a pulp capping or base/liner will be greatly decreased in the mouth because of the moisture of dentin.
Varnishes Copal Varnish Resins dissolved in a solvent Painted onto entire cavity preparation Solvent evaporates, leaving thin resin layer Used under amalgams NOT used with composites (interferes with adhesion) Cavity Sealer
Cements as Pulp Protectors
Use Protective properties One of the least irritating dental materials 1. Temporary cement 2. Insulating base under permanent restorations 3. Provide obtundant filling for sensitive tooth Thermal trauma Sedative, soothing effect on dental pulp Zinc-oxide eugenol (ZOE)
Powder Liquid Use scoop provided by manufacturer Place 1 scoop of powder onto glass slab or paper pad Dispense 2 drops of eugenol by holding dropper perpendicular to slab/pad Drops should not touch powder, but should be near to it Measuring ZOE
Mixing ZOE cement Hold spatula in “flat” position Draw about half of powder into liquid Use small area of mixing slab/pad Push powder into liquid with quick motion Continue incorporating small portions of powder Mix should be complete in 1.5 minutes Sticky consistency – use for cementing temporary crown Thick, putty-like consistency – use for base or temporary filling
Reinforced ZOE IRM Stronger, less soluble than ZOE Temp restorations Intermediate bases Additives include: Alumina Resins Intermediate Restorative Material
Mixing IRM Measure 2 scoops of powder onto glass slab/paper pad Place 1 drop of liquid onto slab/pad Hold spatula in “flat” position Draw about ½ of powder into the liquid Use small mixing area; spatulate with quick motion Continue incorporating powder into the mix by pressing powder into the mix Mix must be thick, putty-like Complete mix in about 1.5 minutes
Application Gather IRM into one mass on the mixing slab/pad May be rolled with fingers to form a ball Use flat-bladed instrument to carry portions of material to the cavity prep May dip instrument into excess powder to prevent sticking Sets up in about 3 – 3.5 minutes Glass slab may be cleaned with alcohol wipe
Temp Bond Properties High flow to permit ease of seating restoration Strong enough to withstand forces of chewing Allow restoration to be easily removed Temporary Cement
Measuring Mixing Two tubes Catalyst Base Squeeze equal lengths of material onto pad Mix together in 30 sec. Homogenous color Should form a string when stretched from mixing pad Apply thin layer to restoration, sets in 2 min. Temporary Cement
Temporary Crown Temporary crown Crown prep leaves an exposed tooth which can be painful. Temp crowns usually made of plastics and formed in mouth. Also made of metal or plastic formed outside of mouth. Temporary cement used to apply temp crown. Placed at crown prep appointment, lasts few days or weeks.
How Temporary Restorations are used: Remove all or part or decay from tooth, then allow pulp to heal before determining treatment. Patients with many carious lesions (more than 10) to make the oral environment noncariogenic A temporary filling on an “open” tooth in endodontic therapy.
Exposure controls/personal protection with Eugenol Respiratory protection: In well ventilated areas respiratory protection is not normally required. In confined, poorly ventilated area respiratory protection may be necessary Hand protection: Wear impervious gloves Eye protection: Wear eye protection. e.g. Safety glasses/goggles
What you need to know to stay safe As with most dental materials …read the label and look for hazardous or toxic products in the materials Be aware of potential for allergic reactions Follow OHSA exposure limits
Generic and brand names of base materials Bases: Shofu base cement (Shofu) Ketac bond capsules (ESPC) Zinc Phosphate (Mizzy) ZOE B&T (Caulk)- Eugenol-containing material
Generic and brand name Liners Liners:Heavy filled glass ionomers: Fuji IX GP in capsule or powder/liquid form. ESPE: provisional filler, larger non-stress-bearing build ups SHOFU Light cured resin modified glass ionomer Vitre-bond (3M) Fuji Lining Cement LC (G-C)
Group Activity Divide up into 5 groups – about 4 to a group Discuss the case study your group is given, and answer these questions: 1.What material will you select for your patient? 2.Why did you select that material? 3.How will you mix/apply the material? 4.How long would you expect the material to last?