Pretend you are a teacher preparing a quiz for the text I will provide. 
            Each quiz question should follow the format below. 
            Ensure that you carefully recheck the questions and answers for accuracy. 
            The output should be a ready-to-use list of dictionaries for the Python eval function:

            [

                    "question": "WRITE THE QUESTION HERE",
                    "options": ["A) OPTION_1", "B) OPTION_2", "C) OPTION_3", "D) OPTION_4"],
                    "answer": INDEX_OF_CORRECT_ANSWER_IN_OPTIONS_LIST,
                    "explanation": "EXPLAIN WHY THE ANSWER IS CORRECT"

            ]

            Text:
            fe. 
95
 
 
Classification of impression material: 
Classified according to their Chemistry (setting behavior) into: 
 
  In-elastic                                                    Elastic 
➢ Plaster                                                   
➢ Waxes 
➢ Impression compound                                                 
➢ Zinc-oxide /Eugenol              Hydrocolloids                        Elastomeric  
                                                                                                    (Rubber-based)                             
                                                                                                 1st Poly-sulphide  
                                                                                                 2nd Condensation Silicone      
                                                                                                 3rd Polyether 
                                     1st Agar-Agar         Alginate             4th Addition Silicone 
Based on Setting Reaction 
1. Reversible (physical): impression waxes, impression compound, & agar.  
2. Irreversible (chemical): impression plaster, alginate, & elastomeric impression. 
Based on the State of the Impression Material After Setting in the Oral Cavity 
1. Rigid: impression plaster, impression waxes, impression compound, ZnO eugenol 
2. Elastic: alginate, agar, polysulfides, addition & condensation silicones, polyether 
Based on Use 
1. For 1ry impressions, e.g., impression compound, alginate, & elastomeric putty. 
2. For 2ry impressions, e.g., light body elastomers & zinc oxide eugenol. 
Based on Compression of Underlying Tissues 
1. Mucostatic: impression plaster & light-body elastomers. 
2. Mucocompressive: impression compound & putty elastomers. 
 
96
 
 
Classification of Elastomeric impression material Based on 
Consistencies (Viscosity) 
1. Light (Low) body: is used in thin section (2 - 4 mm) in custom trays → 
                                to ↓ polymerization shrinkage.  
2. Medium (Regular) body 
3. Heavy (High) body 
4. Putty (Very High): contain ↑ amount of fillers 75%  
                                  is more dimensionally stable than light bodies. 
➢ Each material has advantages & disadvantages, 
& none is entirely free of shortcomings. 
➢  However, they all share one important characteristic: 
When handled correctly, they can produce casts of sufficient accuracy & surface 
detail for the fabrication of clinically acceptable FDPs.  
 
 
➢ In comparison, Irreversible hydrocolloid (alginate) is not sufficiently accurate for 
fabrication of precisely fitting restorations. 
Nevertheless, there are reasons for selecting one material over another: 
1- If it becomes necessary to store the impression before a cast is made,  
     the polyether & addition silicone are preferable, 
because they exhibit sufficient long-term dimensional stability.  
➢ The hydrocolloids & condensation silicone must be poured immediately. 
➢ 

            Quiz: