Structures present in enamel and there clinical significant Flashcards
What’s Gnarled enamel ?
consists of bundles of enamel rods which entwine in an irregular manner with other group of rods, finally taking a twisted and irregular path towards the tooth surface (Fig. 3.4).
It is seen near incisal, occlusal, and cervical area
Significance of gnarled enamel ?
In these areas, enamel is not easy to break as regular enamel
What’s Hunter-Schreger Bands ?
dark and light strips which occur due to change in direction of rods.
These are seen in large ground sections when viewed under microscope (optical phenomenon).
What’s the Significance H-S bands ?
resist and disperse the strong forces
What’s Enamel tufts ?
ribbon-like structures which run from dentin to enamel.
They are named so because they resemble tufts of grass.
They originate from DEJ and extend into enamel along the long axis of the crown
Significance of Enamel tufts ?
are hypomineralized structure in enamel, thus play role in spread of dental Caries
Which structure of enamel contain organic substances and are caused by “imperfect calcification of enamel tissue” ?
Enamel Lamellae
These are thin, leaf-like defects, originate at enamel surface and may extend to DEJ
Significance of Lamellae ?
at base of fissure provides pathway for bacteria and initiates caries
Which structures in enamel are caries intiators and play role in caries spread ?
Enamel Tufts , lamellae , pits and fissures
Which structures in enamel are caries intiators and play role in caries spread ?
Enamel Tufts , lamellae , pits and fissures
What’s enamel spindles ?
The Odontoblastic processes that sometimes cross DEJ and their ends are thickened and called spindles
why sometimes when enamel is cut, patient complains about pain ?
Enamel Spindles serve as pain receptors in enamel
Which enamel structure represent the rest periods of ameloblast during enamel formation, therefore, also called as growth circles, similar to annual rings on a tree ?
Striae of Retzius
These appear as brownish bands in ground sections and illustrate incremental pattern of enamel
What’s prismless Layer ?
It is a structureless layer of enamel near the cervical line and to a lesser extent on the cusp tip which is more mineralized
Explain the form of Dentinoenamel junction and thickness and mineralization:
is scalloped interface of enamel and dentin.
DEJ is 2–15 μm in thickness and is hypermineralized structure.
It is scalloped in outline in which rounded projections of enamel fit into shallow depressions of dentin.
This helps in better interlocking between enamel and dentin
What’s the significance of Scalloped shape and interlocking of enamel and dentin at dentinoenamel junction ?
prevents tearing of enamel during functions
How does pits and fissures get formed ?
Pits and fissures are formed by faulty coalescence of developmental lobes of premolars and molars (Fig. 3.6).
Difference between grooves and fissures formation ?
Grooves are formed when there is sound union of enamel lobes. These provide an escapeway for food during mastication.
Fissures are faulty union between enamel lobes
How does pits and fissures assist in caries progression?
- Thickness of enamel at the base of pit and fissure is less, causing early spread of caries to dentin.
- Fissures favor the food impaction making them caries prone areas.
In early caries, subsurface enamel porosity results from demineralization, it appears as chalky white spot on drying the enamel , what’s happen when it reaches dentin and in how much time take for this white spot to progress through enamel ?
When demineralization reaches DEJ, this white opacity becomes visible in both dry and wet enamel.
* It takes 4 to 5 years for this white spot lesion to progress through enamel.
* When dentin gets involved, it appears as blue or grayish .
In early caries, subsurface enamel porosity results from demineralization, it appears as chalky white spot on drying the enamel , what’s happen when it reaches dentin and in how much time take for this white spot to progress through enamel ?
When demineralization reaches DEJ, this white opacity becomes visible in both dry and wet enamel.
* It takes 4 to 5 years for this white spot lesion to progress through enamel.
* When dentin gets involved, it appears as blue or grayish .
What’s attrition and the normal wear rate per year ?
What’s the complications of wear ?
It is mechanical wear of enamel on occlusal and proximal surfaces (Fig. 3.7).
Normal physiologic wear rate of enamel is 15–29 μm per year.
Tooth wear causes loss of vertical dimension of tooth which can be counteracted by active tooth eruption and apical cementogensis
How does acid etch works on enamel to form micro and macrotags in enamel which improves bonding between resin and enamel ?
Initially, it removes about 10 μm of surface enamel which does not contain any rod structure,
after this, it exposes rods and interrods.
Dissolution of this rod and interrod substance causes macropororisties
What’s the result from etched enamel ?
high surface energy so resin flows up to 20 μm in depth
why various fluids, pigments, ions, demineralization, remineralization, fluoride intake, and vital bleaching are possible to go through enamel ?
Cause it semipermeable
Hypomineralized areas present in enamel are more permeable than mineralized
Why shade match most be done before rubbber dam placement and in full light spectrum ?
When teeth are dehydrated (during mouth breathing or rubber dam application), enamel appears chalky white and lighter in color
avoid fracture of tooth and restoration, enamel walls should be supported by underlying dentin and preparation walls should be made parallel to direction of enamel rods why ?
Crystals in enamel rods run parallel to length of enamel rods and enamel rods run parallel to the tooth surface.
The preperation most be like that , because enamel rod boundaries are natural cleavage lines through which fracture can occur.
Why remineralization is possible in enamel ?
because of enamel’s permeability to fluoride, calcium, and phosphate (available from saliva or other sources).
