請英文達人~幫幫忙吧

INTRODUCTION Dental calculus appearance and formation are not well understood yet. A well-known theory of calculus formation1 considers that precipitation of calcium salts from supersaturated saliva is a result of an increased pH caused by the loss of carbon dioxide from saliva. The colloidal precipitation2 theory... show more INTRODUCTION
Dental calculus appearance and formation are not
well understood yet. A well-known theory of calculus
formation1 considers that precipitation of calcium salts
from supersaturated saliva is a result of an increased
pH caused by the loss of carbon dioxide from saliva.
The colloidal precipitation2 theory assumes that colloidal
substances in saliva become viscous and form
the matrix for the precipitation of calculus. Apparently,
the bacterial presence plays an important role
through chemical and enzymatic actions.3 Also, external
factors like dietary, salubrity, and hygienic habits,
among others, which vary from one individual to
other, act on calculus release. Probably a combination
of all these issues mediates in calculus appearance. In
addition, an individual dependence exists because
two different subjects with similar healthy status, in
the same environment, can have a very different
proneness to form calculus. Similar to the mechanisms
of calculus appearance, the structural phase changes
during calculus maturation are not well known. Understanding
these phase changes and the actions of
the agents that participate in them would contribute to
understand the mineralization processes and gather
the problem of calculus inhibition.
Dental calculus on teeth consists mainly of four
different calcium phosphate4 phases: hydroxyapatite
[Ca10(PO4)6 (OH)2], brushite (CaHPO4 2H2O), whitlockite
or tricalcium phosphate [(Ca,Mg)3 (PO4)2], and
octacalcium phosphate (Ca8H2(PO4)65H2O). From a
thermodynamics point of view, a system where several
phases coexist, as is the case of calculus, is a
complicated issue in physics. In addition, these crystals
can incorporate and exchange anions and cations
with the liquid media (saliva, plaque, and crevicular
fluids), which are rich in ions. Hydroxyapatite (HA)
allows the substitution of many ions (K, Na, Mg2,
F, Cl, CO3
2, HPO4
2, etc.),
1 answer 1