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:
            e material 
 The primary disadvantage amalgam restorations are that they are 
metallic and non-esthetic. 
 The preparation for an amalgam restoration typically requires 
90-degree cavo-surface margins specific and uniform axial 
depths, and incorporation of secondary retentive features, all of 
which results in a less conservative preparation than that for 
other esthetic restorative materials. 
 
Clinical technique for class V amalgam preparation 
Initial Clinical Procedures  
Local Anaesthesia  
Isolation (rubber dam recommended) 
Tooth preparation 
I. OUTLINE FORM  
Rounded trapezoid in gingival 1/3.  
Conforms to the tooth shape, typical caries location, and site of 
plaque accumulation.  
Primarily determined by the location and size of the caries/defect or 
old restorative material  
Cavosurface margins should be extended to sound tooth structure 
while maintaining a limited axial depth of 0.5 mm inside the DEJ and 
0.75 mm inside the cementum (when on the root surface) 
4 
  
Using round bur to start entry to the cavity, the direction of the bur 
should be perpendicular to the buccal (or palatal) surface of the tooth , 
then using a tapered fissure bur of suitable size, enter the carious 
lesion to a limited initial axial depth of 0.5 mm inside the DEJ.  
This depth is usually 1 to 1.25 mm total axial depth, depending on 
the 
incisogingival/occlusogingival 
location 
(The 
enamel 
is 
considerably thicker occlusally and incisally than cervically)  
However, if the preparation is on the root surface, the axial depth is 
approximately 0.75 mm.  
Extend the preparation incisally, gingivally, mesially, and distally 
until the cavosurface margins are positioned in sound tooth structure 
providing the desired outline form  
Preparation of the axial wall depth 0.5 mm inside the DEJ results in 
a uniform depth for the entire preparation.  
Because 
the 
axial 
wall 
follows 
the 
mesiodistal 
and 
incisogingival/occlusogingival contours of the facial surface of the 
tooth, it will usually be convex in both directions as shown fig 2.  
The mesial, distal, gingival, and incisal walls of the tooth 
preparation are perpendicular to the external tooth surface to keep the 
cavosurface angle 90 degree and to follow the direction of enamel 
rods, they usually diverge facially.  
Consequently, this form provides no inherent retention, and 
retention form must be provided. 
5 
 
 
 
Fig 2: convex axial wall 
II. Resistance form  
Depth of the cavity is 1.5 mm: the axial wall of the cavity should 
not be flat, if we do so will not have even depth of the cavity because 
of convexity of tooth structure, so the axial wall should be slightly 
convex.  
cavosurface line angle (90-110). 
Rounded internal line angles 
Removal of unsupported enamel  
Occlusal and gingival walls should be perpendicular to the long 
axis of the tooth and parallel to each other, any convergence of these 
walls will create unsupported enamel. 
III. Retention form: 

            Quiz: