Enamel morphology Flashcards
where is enamel thickest and where is it thinnest on an anterior tooth?
thickest at incisal edge.
thinnest at the cervical region.
where is enamel thickest and thinnest on a posterior tooth?
thickest at cusps, thinnest at the cervical region.
which enamel is more mineralised? surface or deeper enamel?
surface enamel is more mineralised than deeper enamel.
where is the best area to etch enamel?
enamel etches the best at the interrod region as you can bind to enamel crystallites better from the side.
what causes striae of retzius?
weekly incremental lines caused by a weekly change in direction of enamel formation. unknown why there is a change.
which area of enamel is most susceptible to caries?
the interrod region is the most susceptible to caries.
what percentage of enamel is composed of organic matrix and what are its functions?
organic matrix is 1% weight and 1-2% volume.
it functions by fitting in beside each crystallite and adds a degree of flexibility to the enamel.
give a description of how enamel crystallites are shaped and organised
Enamel crystallites are organised into a shape by proteins secreted by ameloblasts. These proteins then enucleate the crystallite once it is in shape. The proteins then completely leave the crystallite - caused by ameloblast maturation.
when may a hydroxyapatite crystallite become more susceptible to acid attack?
when ion substitution occurs. when the calcium is exchanged for carbonate or magnesium.
if fluoride is substituted, then becomes less susceptible.
what course do enamel rods run along? What do the periodic changes in the course between adjacent enamel rods cause?
sinusoidal course.
The course changes between adjacent enamel cause hunter-Schreger bands.
what are Hunter-Schreger bands?
bands caused by the sinusoidal course of enamel rods. only found near EDj and not enamel surface.
give 3 examples of enamel malformations along the EDJ
enamel lamellae, enamel tufts and enamel scalloping.
what are enamel tufts?
small projections of hypo-mineralised regions. caused by residual matrix protein at prism boundaries.
what are enamel lamellae?
incomplete maturation of groups of prisms causing a fault line extending through enamel thickness.
what is enamel scalloping? and what clinical sign may show if it is not present?
enamel is rough near the EDJ. This surface allows for a stronger bond and helps resist shear forces.
Abfraction
