Zinc Phosphate Cements PDF Fall 2024

PDD 233 Dental Biomaterials III Fall 2024 Dr.Mohamed M.Abdul-Monem 1 Week Topic 1 Dental Cements (1) 2 Dental Cements (2) 3 Dental Cements (3) 4 Dental Alloys (1)...

PDD 233 Dental Biomaterials III Fall 2024 Dr.Mohamed M.Abdul-Monem 1 Week Topic 1 Dental Cements (1) 2 Dental Cements (2) 3 Dental Cements (3) 4 Dental Alloys (1) Quiz 1 (5) 5 Dental Alloys (2) 6 Dental Amalgam 7 Midterm (25) 8 Dental Ceramics (1) 9 Dental Ceramics (2) 10 Dental Composite (1) 11 Dental Composite (2) 12 Denture base polymers (1) Quiz 2 (10) 13 Denture base polymers (2) 14 Final Practical (20) 15 Final Exam (40) 2  Dental Cements Dr.Mohamed M.Abdul-Monem 3  Content Lecture 1 :  Introduction  Zinc Phosphate cement Lecture 2 :  Zinc Polycarboxylate cement  Glass ionomer cements Lecture 3 :  Zinc oxide eugenol cements  Calcium hydroxide cements Dr.Mohamed M.Abdul-Monem 4  Dental Cements (1) Dr. Mohamed Mahmoud Abdul-Monem Assistant Professor of Dental Biomaterials AIU Fall 2024 Introduction  Dental materials according to Uses Dental materials Restorative Auxiliary Impression materials Gypsum products Waxes Amalgam Composite Direct Glass ionomer Dr.Mohamed M.Abdul-Monem Indirect Removable 7 Fixed Direct restorations Class I , II and IV are stress-bearing areas. Class III and V are non-stress bearing areas. 8 Dr.Mohamed M.Abdul-Monem  Dental Cements  Dental cements Uses Luting cements Bases and Liners Dr.Mohamed M.Abdul-Monem 10 Restorative Dental cements Luting cements Liners Bases Cementation Barrier against Thermal , of restorations chemical mechanical 25 µm (0.025 irritation and electrical mm) 0.2-1 mm insulators Dr.Mohamed M.Abdul-Monem 1-2 mm 11 Requirements of dental cements 1. Non-toxic and non-irritant to pulp and surrounding tissues. 2. Insoluble in saliva. 3. High mechanical properties. 4. Antibacterial. 5. Adhesive properties. 6. Sedative or obtundent effect (Relief pain). 7. Low viscosity (When used as luting cements). 8. Good optical properties for cementation of thin restorations (Veneers) Dr.Mohamed M.Abdul-Monem 12 Classification of dental cements Water-based Oil-based Resin-based Zinc phosphate Zinc oxide eugenol Resin cements Zinc polycarboxylate Glass ionomer Dr.Mohamed M.Abdul-Monem 13 Zinc phosphate cement Zinc phosphate cement  Oldest cement.  Standard by which new cements are compared. Dr.Mohamed M.Abdul-Monem 15 Uses Luting cement Base only NOT Liner ?? Dr.Mohamed M.Abdul-Monem 16 Cementation of orthodontic bands Temporary filling Composition Powder Liquid 1. Zinc oxide (90 %) 1. Phosphoric acid (40 %) 2. Magnesium oxide (9 %) 2. Water (33 %) : Controls ionization of the acid which in turn controls rate of reaction 3. Silicon oxide with the powder. 3. Metallic salts (Aluminum phosphate and 4. Bismuth trioxide zinc phosphate) are added to reduce the reaction rate of the liquid and act as buffering agents to stabilize the pH.  The oxides are sintered at temp. between 1000-1400º C to form a fused mass which is then ground to fine powder.  Sintering reduces the powder reactivity. This is good ?!!!  (Slows setting reaction and 17 increases setting time) Setting reaction of zinc phosphate Zinc oxide + Phosphoric acid Zinc aluminophosphate + Heat (Exothermic) The set cement is a cored structure of unreacted ZnO embedded in a cohesive matrix of zinc aluminophosphate. Dr.Mohamed M.Abdul-Monem 18 Manipulation of Zinc Phosphate cement Instruments needed:  Thick and cool glass slab  Narrow-bladed spatula Dr.Mohamed M.Abdul-Monem 19 Factors affecting working and setting time Controlled by manufacturer Controlled by operator 1. Degree of powder Sintering ?? 1. P/L ratio 2. Particle size of powder ?? 2. Rate of powder incorporation 3. Buffering of liquid ?? 3. Mixing temperature 4. Water content of liquid ?? 4. Manner of spatulation 5. Water content of the liquid. Dr.Mohamed M.Abdul-Monem 20 Factors controlled by the operator 1.P/L ratio : Not acceptable as it affects physical and mechanical properties. 2.Rate of powder incorporation : Divide the powder into increments to generate less heat. 3.Mixing temperature: Use a thick cool glass slab (Most effective method), to absorb heat. 4.Manner of spatulation : Mix over large area to dissipate heat 5.Water content of the liquid : Don’t leave the bottle open for the liquid not to absorb or lose water. Increased water content accelerates the setting reaction due to ionization of phosphoric acid. Dr.Mohamed M.Abdul-Monem 21  Retention of zinc phosphate cement Mechanical retention based on the flow of cement into microscopic irregularities on the tooth and surface of restoration. Dr.Mohamed M.Abdul-Monem 22 Biocompatibility of zinc phosphate  Irritant effect on pulp (Low pH ).  Thus, it is used only as a base underneath which a liner of another cement is used. Zinc phosphate Calcium hydroxide Dr.Mohamed M.Abdul-Monem 23 Zinc phosphate cement Advantages Disadvantages  Sharp, well-defined set, so  Irritant to the pulp. excess is removed easily.  Difficult to control  High compressive strength. exothermic reaction.  No antibacterial effect.  Brittle.  No adhesive properties. Dr.Mohamed M.Abdul-Monem 24  What do you need to know after studying this lecture ? Dr.Mohamed M.Abdul-Monem 25 Thank you