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:
            d in equal proportions → polyether rubber. 
• Setting reaction is addition polymerization reaction  with no by-product.  
Presentation: 
• Available as light, medium, & heavy-body consistencies. 
Advantages: 
1. Accuracy & excellent dimensional stability (no by-products)   
so pouring could be delayed up to 7 days, & allow multiple pouring. 
2. Hydrophilic in nature. 
3. Good elastic recovery. 
4. Good compatibility with gypsum.  
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5. Good shelf life. 
6. Short setting time (3 - 5 minutes). 
7. short working time.  
8. It can be used as a single-phase material  
or with a syringe-tray technique. 
Disadvantages: 
1. Most rigid of all the elastomers makes it hard to remove  
(newer polyethers are slightly more flexible).  
2. High stiffness  difficult to remove from the mouth & from the cast. 
To overcome this problem, the manufacturer apply thinner to  stiffness  
&  working time. 
3. Short working time which limit its use in case of multiple abutment. 
4. High tendency to absorbs water  so impression must be kept dry. 
5. Can not be electroplated. 
6. May cause allergy reaction due to sulfonate acid esters.  
7.  its thermal expansion is > polysulfide. 
 Recent impression materials: 
 
1- Alginate Substitutes  
✓ It is an addition silicone impression material that provides a detailed impression.  
✓ Available in double-barrel cartridges for automatic mixing machines 
Advantages: 
1. Excellent elastic recovery,  
2. High tear resistance, 
3. High dimensional stability, 
4. Hydrophilic,  
5. Possible to obtain several models from the same impression. 
Disadvantages 
1. Much more expensive than traditional alginate.  
2. The material sets very hard  difficult to separate from the model.  
Indications:  
1. 1ry impressions 
2. Opposing dentition impressions  
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3.  Interim crown & bridge impressions.   
4. Impressions for orthodontic models   
5. bleaching trays.  
2- Vinyl Polyether Silicone 
(Hybrid Impression Material): 
▪ It was commercially introduced in 2009. 
▪ SENN is a formulation that combines properties of the  
addition silicone (vinyl polysiloxane) & polyether impression material.  
Advantages: 
1. It has dimensional properties similar to those of the addition silicone & polyether.  
2. Although  bulk of an elastomeric impression material →  its accuracy. 
➢ the opposite is true for reversible hydrocolloid impressions. 
➢ In hydrocolloid impressions, dimensional change is caused by water loss / gain 
from the surface of the impression.  
➢ A bulky hydrocolloid impression has a lower ratio of surface area to volume 
→ so  subject to dimensional change. 
3. Hydrophilic properties. 
4. High tear strength.   
5. Resistance to deformation. 
Disadvantages: 
1. Incomplete material mixing with light-body & monophase viscosities that appears 
to be random in nature.  
2.  Possible loss of detail reproduction within incompletely mixed material.  
 
3. Implant impression material: 
Advantages:  
1. Sterility ensures →  post-

            Quiz: