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:
            rregular and pitted surface with 
numerous microscopic undercuts, the 
etched enamel has a higher surface 
energy, so resin monomer flows into 
and adheres to the etched depressions 
to polymerize and form retentive resin 
tags. 
www.drcube.org 
Because there are (30,000) to (40,000) 
enamel rods/ mm2 and acid etch 
penetration increases the bondable 
surface area to (10) to (20) folds, 
micromechanical bonding of resin 
restorative materials to E. is significant. 
Acid-etch modification of enamel for 
restoration 
retention 
provides 
a 
conservative, reliable, alternative to 
traditional 
methods 
of 
tooth 
preparation and restorations (retentive 
grooves, pins, and extension for 
prevention...). 
www.drcube.org 
Starting at 1mm from the CEJ, the rods on 
the vertical surfaces run occlusally or 
incisally at approximately a 60-degree 
inclination 
and 
progressively 
incline 
approaching the marginal ridges and cusp 
tips, where the rods are parallel to the 
long axis of the crown.  
The rods beneath the occlusal fissures are 
also parallel to the log axis, but rods on 
each side of the fissure vary up to 20 
degrees from the long axis. 
www.drcube.org 
Loss of enamel rods that form the cavity 
wall of cavo-surface margin of dental 
restorations creates a gap defect, leakage 
of bacteria and their products that may 
lead to secondary caries. 
Therefore, a basic principle of cavity wall 
preparation is to bevel or parallel the 
direction of enamel rods and avoid 
undercutting them. 
www.drcube.org 
In the cervical region of permanent teeth 
enamel rods are oriented outward in a 
slightly apical direction, therefore a 
perpendicular cut to the external surface 
of occlusal walls of preparation on axial 
surfaces compromised enamel, so an 
obtuse enamel cavo-surface angle is 
recommended to closely parallel the rod 
direction and preserve the integrity of 
enamel margin. 
www.drcube.org Properties of Enamel 
Properties of Enamel 
Enamel is the hardest substance of 
human body. The hardness value of 
enamel (HV = 275) is around 4 to 5 times 
higher than that of dentin (HV = 65). 
 Hardness 
1 
Brittleness 
2 
Enamel is very brittle; thus, it requires a 
base 
of 
dentin 
to 
withstand 
the 
masticatory stress. Enamel rods that fail 
to possess a dentin base because of 
caries or improper cavity design are easily 
fractured away from neighboring rods. 
www.drcube.org 
At maturity, enamel is about 90% inorganic 
hydroxyapatite mineral by volume. Enamel also 
contains a small amount of organic matrix and 4% 
to 12% water which is contained in the 
intercrystalline spaces and in a network of 
micropores opening to the external surface. The 
micropores form a dynamic connection between 
the oral cavity and the systemic pulpal and 
dentinal tubule fluids. 
Permeability 
3 
www.drcube.org 
Various 
fluids, 
ions 
and 
low 
molecular weight substance can 
diffuse through the semipermeable 
enamel. Therefore, the dynamics of 
acid 
demineralization, 
carie

            Quiz: