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:
            gent over time. 
www.drcube.org 
Restored teeth are also at risk of toxic seepage 
through 
the 
phenomenon 
of 
microleakage 
between the restorative material and the cavity 
wall, through capillary action differential thermal 
expansion, and diffusion, fluids containing various 
acidic and bacterial products can penetrate the gap 
between the tooth and restoration and initiate 
secondary caries of the internal cavity walls. 
Bacterial substances can continue diffusion through 
permeable dentinal tubules to reach the pulp, 
putting the tooth at risk for pulpal inflammation 
and sensitivity.  
www.drcube.org 
Restorative techniques with varnishes, 
liners or dentin bonding resin adhesives 
are effective to provide reliably sealed 
margins and sealed dentinal surface. 
No restorative material or technique can 
ensure a complete hermetic seal of the 
restoration-tooth interface, and leakage at 
the gingival (cementum or dentin) margins 
of resin-bonded restorations is commonly 
reported. 
www.drcube.org 
However, the remaining dentin thickness 
is the key determinant of the rate of 
diffusion of gradient into the pulp, 
because 
thicker 
remaining 
dentin 
thickness with provide both smaller 
tubular diameters and greater tubular 
lengths, 
therefore 
thicker 
remaining 
dentin thickness can significantly reduce 
both the adverse toxic effect of restorative 
materials and bacterial irritation to the 
pulp. 
www.drcube.org 
There are also regional differences in dentinal 
permeability. Coronal dentin is much more 
permeable than root dentin. The coronal 
occlusal dentin (pulpal floor of a cavity 
preparation) is inherently less permeable than 
is the dentin around the pulp horns or axial 
surfaces. As a result, only about 30% of the 
subjacent dentinal tubules on occlusal surface 
are patent over their entire length. However, 
prepared proximal boxes or gingival margins, 
which are relatively more susceptible to 
microleakage and development of recurrent 
caries lesions, are located where the dentin is 
most permeable. 
www.drcube.org Sensitivity of Dentin 
Sensitivity of Dentin 
Although dentin is sensitive to thermal, tactile, 
and osmotic stimuli across its (3-3.5 mm) 
thickness.  
Dentin is neither vascularized nor innervated, 
except for about 20% of tubules that have nerve 
fibers penetrating inner dentin by a few microns.  
Also, odontoblastic processes in the dentinal 
tubules reach only the inner third of dentin and 
their cell membrane is not conductive, however 
recent studies suggest that odontoblasts could 
possibly be directly involved in the sensory 
transduction process of the tooth through some 
form of mechanosensory system. 
www.drcube.org Theories of Pulpal Sensitivity 
Theories of Pulpal Sensitivity 
According to direct innervation theory, nerve endings penetrate dentine and extend to 
the dentino-enamel junction. Direct mechanical stimulation of these nerves will 
initiate an action potential. There are many shortcomings of thi

            Quiz: