Dentaltown November 2017 - 82

Hydration Reactions (A,B)
A-2[3CaO*SiO2] + 6H2O ➞ 3CaO*2SiO2*3H2O +3Ca(OH)2
B-2[2CaO*SiO2] + 4H2O ➞ 3CaO*2SiO2*3H2O +Ca(OH)2
Fig 4a. Chemistry associated with the hydration reaction of bioceramic material (calcium silicates) with
water (moisture present in canal and tubuli) creates calcium silicate hydrate and calcium hydroxide.

TriCalcium Silicate

Calcium Silicate Hydrate (CSH)

2[3CaO*SiO

] + 6H2O ➞

Calcium Hydroxide

3CaO*2SiO * 3H
2

CSH

O + 3Ca(OH)2

Ca(OH)2

H2 O

Bioceramic Particle

Fig 4b. Precipitation reaction of the bioceramic (calcium phosphate). The hydroxyapatite co-precipitated
within the calcium silicate hydrate phase produces a composite-like structure, reinforcing the set
cement.

Precipitation Reaction
C-7Ca(OH)2 + 3Ca(H2PO4)2 ➞ Ca10(PO4)6(OH)2 + 12H2O
Figs 4c. The bioactivity of the calcium-silicate-based materials has been shown to produce
mineralization within the subjacent dentin substrate, extending deep within the tissues.

Calcium Silicate Hydrate
Gel Calcium Hydroxide

Calcium Silicate
Water
6H2O

2[3CaO*SiO2]2

A scientific paradigm shift
in root filling
3CaO*2SiO2*3H2O +Ca(OH)2

Fig 4d. Setting reaction of the hydrated materials; a cementitous phase that is rich in calcium and silicon
and a radiopacifying material is produced.

NOVEMBER 2017 // dentaltown.com

medicine and dentistry as they are chemically
and dimensionally stable, biocompatible
and osteoconductive.
The properties, in addition to being
non-corrosive, are categorized as:
* Bioinert-non-interactive with
biological systems.
* Bioactive-durable tissues that can
undergo interfacial interactions with
surrounding tissue.
* Biodegradable, soluble or resorbable-eventually being replaced or
are incorporated into tissues.
Bioceramics are ideal for use in endodontics as they are not affected by moisture
or blood contamination and, therefore,
technique sensitivity is not an issue unlike
most other sealers where moisture negates
their performance.20
Being that they are hydrophilic, residual
moisture in the canal and dentinal tubuli
are biochemically a positive factor. In the
context of creating an impervious seal, they
are dimensionally stable and expand slightly
on setting, ensuring a long-term seal due
to the hydration reaction forming calcium
hydroxide and later dissociation into calcium
and hydroxyl ions21-22 (Figs. 4a, 4b).
When setting, the pH of the bioceramic
is above 12, which is due to a hydration
reaction forming calcium hydroxide and
later dissociation into calcium and hydroxyl
ions (Figs. 4c, 4d), which may explain the
antibacterial properties of the bioceramic.
The release of calcium hydroxide and its
interaction with phosphates on contact
with tissue fluids forms hydroxyapatite.
This may explain the osteo-conductive
potential of the material. Bioceramics are
seen as today's material of choice for pulp
capping, pulpotomy, perforation repair,
root-end filling and obturation of immature
teeth with unformed apices.23

Premixed bioceramic sealer is composed of dicalcium and tricalcium silicate,
calcium phosphates (monobasic), colloidal
silica, water-free thickeners and calcium
hydroxide in combination with radiopacifiers

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Table of Contents for the Digital Edition of Dentaltown November 2017