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:
             closure by the patient.) 
 
 
A, The tray is selected & evaluated. B, The tray is loaded.  
C, Impression material is delivered by syringe. 
       D, Patient closes into MI. E, Completed impression. 
6) Auto-mix Technique: 
• Several manufacturers of addition silicone supply the material in  
prepackaged cartridges (light & medium consistencies),  
• These cartridges are placed in caulking gun-like device,  
• with disposable mixing tip which contain baffles or spirals which force the base & 
the catalyst to be folded over each other as they are extruded from the tip (i.e. 
automatically mixed). 
• The homogeneously incorporated material can be  
placed directly on the prepared tooth & impression tray. 
• Automix material is not available for the polysulfide polymers because 
these materials are too sticky for proper mixing with existing cartridge tips. 
Advantages: 
• No hand mixing on pads, as a result  →   voids in the impression. 
 
122
 
 
• Disadvantages: 
➢ comparatively larger gun systems require a steadier hand to precisely track the 
preparation margin than do the shorter syringe systems.  
➢ Even minor movement of the hand that holds the impression gun →  
air bubbles & voids in the impression. 
 
 
6) Machine-mixing technique: 
• An alternative method for improving impression mixing by using a machine mixer. 
• Advantage: 
1- Produce void-free mix. 
2- Single degree of viscosity is used for the syringe & the tray.  
• N.B: This equipment should be located close to the dental chair →  
to  time loss between mixing & the actual making of the impression. 
 
 
Impression evaluation: 
We should look for: 
1) All prepared teeth walls & details of the preparation.  
2) All adjacent teeth & occlusal surfaces. 
3) Continuity & configuration of the F.L. 
4) Voids in the finish line → remake. 
5) Presence of nodules is corrected by removing it → if small,  
but if large → remake. 
6) Shiny surface of the rubber base → indicates moisture contamination  
i.e. the material didn't accurately contact the tooth surface.  
123
 
 
 
A, On the left, an adequate cuff is formed by  material extending beyond 
the preparation margin. On the right side (arrow), the impression does not 
extend adequately. B, This  impression reproduces an adequate amount of 
the unprepared tooth structure cervical to the preparation margin. 
 
 
The completed impression. Careful technique ensures a complete cuff of 
impression material beyond the  margin & greatly facilitates trimming of 
the die & contouring of the wax pattern. 
  
❖ Disinfection: 
• Disinfection is an essential step for preventing cross infection  
& exposure of laboratory personnel.  
• If it is performed properly, disinfection does not affect the accuracy or surface 
reproduction of the elastomer. 
• After removal of impression from the mouth → rinsed under tap water. 
• dried with an air syringe. 
• Disinfected by using 2% glutraldehyde / or iodoform spray,  
according to the recommended procedures

            Quiz: