Pulp vitality protection after
carious lesions or traumatic injuries is an Inspiring challenge. Pulp-capping
materials are essential demand to protect the pulp from chemical, thermal and'
other toxic stimuli. Basing on these considerations we will illustrate some of
the recent materials introduced in the operative field to protect the
pulp-dentin complex (MTA, Theracal, Biodentin). We will show their composition,
different properties and their indications.
Introduction
Intermediary
materials are materials placed between dentin (sometimes pulp) and restorative
material to provide pulpal protection, they are adjuncts to the restorative
material and together they form the restorative system.
Abase
is any substance placed under a restoration that blocks out undercut in the
preparation, acting as a chemical or thermal barrier to the pulp and' control
the thickness of overlaying restoration.
A
cavity liner is a fluid paste applied in a thin layer as protective between
dentin and restorative material, liners should be used in layers thicker than
0.5 mm.
The
sound dentin is the best barrier between the pulp and restoration, so further
removal of diseased dentin is required the cavity depth increase and the dentin
bridge decrease, so we use intermediary materials to provide pulpal protection
to achieve this the intermediary materials should provide a sedative action to
the pulp, provide no further irritation, compatible with pulp dentin organ,
stimulate reparative dentin formation, improve the marginal sealing and
adaptation to the cavity walls, should possess thermal and electrical
insulating capacity at minimal film thickness, sufficient strength to resist
fracture under mechanical strength, minimum effective film thickness, not
interfere with the setting and adaptation time of restorative material, should
resist the degradation in the oral fluids, be easy to apply and have
adequate workability
Discussion
• MTA:
MTA
was at first presented in the gray form (GMTA), anyway because of staining
capability of the GMTA white type of MTA (WMTA) was presented. Since
initiation, MTA quickly picked up acknowledgment among dentists and has been
broadly explored as a potential material to seal the pathways of correspondence
between the tooth root and the outer surfaces. It is supplied in powder and
liquid. Because of prevalent biocompatibility, bioactivity furthermore, sealing
capacity, MTA is utilized for both.
MTA Mixing |
■ The
Composition: is extensively like
Portland cements. MTA is a complex
synthetic compound
made out of different mineral phases which included basic oxides of different
components. Several investigations assessed the essential elemental composition
of MTA and revealed that calcium, silica, bismuth' and oxygen involve the primary
components present in MTA. As per the MTA patent, calcium and silica are
the fundamental receptive components though bismuth was included for
radiopacity. The Material utilized within the patent comprised of calcium oxide
(50-75 wt %), silica oxide (15-25 wt %) and' aluminum oxide, together these
oxides established 70-95 wt % of MTA. The compositional imaging of the two
types of MTA introduced oxygen appropriation all through crystalline also,
amorphous phases which demonstrated that all components in MTA were available
in their oxide form. Moreover, chemical contrasts between the two types of MTA
that WMTA contained generally fewer contents of iron oxide aluminum oxide
and'. , (2, 3)magnesium oxide.
ü Particle size: and
morphology of a biomaterial is significant because it fundamentally influences
the physical properties. Numerous examinations have researched Particle size
and shape of MTA and revealed that MTA molecule size range is less 1 µm to
around 30 µm in any case, incidentally' particles up to 50 µm were likewise
revealed. The two types of MTA contained irregular particles. WMTA Includes
small irregular particles with some lengthened needle_ like particles though,
GMTA contained huge small particles alongside little just as prolonged
particles
ü The
Solubility: of MTA is affected by the powder/water proportion utilized
for its mixing. A higher measure of water leads to greater porosity and more solubility in the set structure of MTA by causing more calcium discharge.
ü Compressive
strength: Reactive phases of MTA have distinctive hydration rates, C2S hydrates at a slower rate than C3S, accordingly mechanical properties of MTA may take a few days to come to their maximum. MTA shows moderately less compressive strength contrasted with amalgam, G.I cements also, composites which can be impacted by powder/water proportion
utilized, sort of the liquid of the mix, pH of the mixing fluid and' the surrounding environment also, the conditions of storage.
ü Push out
strength: MTA has lower push out strength. Because C2S has Hydraulic nature and the hydration rate is slow makes pushes out the strength of MTA liable to be influenced by pH, humidity, time after mixing 'and storage conditions.
ü Radiopacity: Bismuth
oxide_ make MTA radiopaque, which is adequate to make MTA conspicuous on radiographs .In any case, the radiopacity of MTA is less than amalgam and gutta_ percha.
ü Porosity: in
a set structure of MTA is influenced by powder/water proportion,expansion of
bismuth oxide, entrapment of air during mixing material and' pH
ü Sealing
capacity and marginal adaptation: of endodontic filling materials' is of
central significance since leakage of irritants from contaminated root canals to
encompassing periradicular tissues represents a larger part of endodontic
disappointments. The sealing capacity of MTA was broadly assessed by (leakage
of dyes, liquid filtration, protein what's' more, bacterial leakage) and had
indicated a predominant sealing capacity for MTA contrasted with amalgam, IRM
and super EBA. The setting reaction of MTA is followed by expansion which may
lessen gaps at MTA interface.
ü The setting
reaction of MTA: is a complex procedure contingent upon the specific extents of mineral phases, their temperature 'and purity of the mix. On hydration calcium silicates present in MTA experiences hydrolysis furthermore, produce calcium silicate hydrate and calcium hydroxide.
(CaO+H2OCa(OH)2) On
hydration' any abundance calcium oxide promptly reacts and forms calcium
hydroxide. (2(3CaO.SiO2) + 6H2O 3CaO2.SiO2.3H2O+ 3Ca (OH)2) While C2S and C3S
react with water to create calcium silicate hydrate (C-S-H) and calcium
hydroxide. The C3S is the most significant mineral in MTA and takes part in the
arrangement of C-SH to give early strength. Then again, C2S reacts slowly and
result in the final strength of the set material.
ü Biological
properties: MTA is a non-neurotoxic and non-mutagenic material which doesn't apply unfavorable impacts on microcirculation, along these lines; it is considered as the least cytotoxic dental material. MTA has great interaction with mineral tissue forming cells and result in collagen release. MTA goes about as an organically dynamic substrate for bone_ forming cells and upregulates the production of interleukin and shows insignificant or no inflammatory reaction when setting in contact with soft tissues. On account of MTA, the formation of hard dentin bridge is quicker thick and with good structural integrity in correlation with calcium hydroxide .the enlistment of mineral tissue formation by MTA is credited to its fantastic sealing capacity, biocompatibility, alkalinity and other material qualities
Disadvantages:
The principle disadvantages of MTA incorporate a discoloration potential incorporation of toxic components in the material composition, difficult handling, long setting time (this makes MTA cannot be applied in 1 visit), high material cost, nonattendance of a known dissolvable for this material. To overcome these disadvantages, efforts have been made; But, adding or removing any different components may influence MTA's optimal characteristics.
ü Clinical
applications: MTA is a material of decision for various endodontic
applications such as pulpotomy, apexification (MTA has a fruitful impact for
the treatment of teeth with necrotic pulps and open apexes. GMTA requires less
time to form apical barrier contrasted with calcium hydroxide), perforation
repair, root_ end filling, pulp capping.
There
are other recent types based on MTA. From these types, we will take about: -
MTA Fillapex Sealer. It is a new endodontic sealer that combines between the
Advantages of MTA and superior canal obturation. It is supplied in two pastes.
MTA Which is found in MTA fill apex is more stable providing a continuos
release of calcium Ions for the remeneralization process and maintain PH, so
has antibacterial effect. It does not cause discoloration to the tooth
structure. Indications: It is indicated in root canal filling with of permanent
teeth. The boiling point of it is (150 deg.ce.), so it can be used in thermal condensation
technique with gutta-percha. Advantages: Excellent flow, it can penetrate and
fill lateral canals. Easy handling and insertion. Allow adequate working time.
Biocompatibility, allowing formation of new tissue without causing any
inflammation. TheraCal LC: It is light-cured introduced in a single paste
calcium silicate-based material advanced by the maker for use as a direct and
indirect pulp capping material and as a defensive base and liner for use with
cements , restorative , or other base materials .
Composition: it contains around
45% wt mineral material (type III Portland cement), 10% wt radiopaque part, 5%
wt hydrophilic thickening agent (raged silica) and about 45% resin. The resin
contains hydrophobic part like ( BisGMA , triethylene glycol dimethacrylate
(TriEDMA or TEGDMA ) and urethane dimethacrylate (UDMA), furthermore it
contains a hydrophilic part like (polyethylene glycol dimethacrylate (PEGDMA)
and (HEMA)
physical
and mechanical properties: Out
of the blue, TheraCal end up being a material ready to release calcium and
hydroxyl particles for a time of at least 28 days , which is significantly more
than MTA and huge amounts of Ca particles could activate ATP, which assumes a
noteworthy role in the process of mineralization. It is suggested that the
resin part of TheraCal (involving hydrophobic and hydrophilic monomers) can
advance Ca what's more, OH ions discharge inside the wet operating site (on the
pulp of tooth or dentine) and could support the cooperation of the definition
with the hydrophilic tooth dentine. The hydrophilic part in TheraCal permits a
few water retention that's likely responsible for the start of the hydration
reaction of the Portland cement particles with subsequent formation calcium
hydroxide ( 8) Hydroxyl ions release during the hydration process result in
alkalinization of the surroundings makes an unfavorable condition for bacterial
endurance and multiplication .These antibacterial properties are basically
required at the dentine/ restoration interface where remaining microbes could
additionally increase the danger of re-contamination and secondary caries,
specifically when utilizing dental composites which loss any antimicrobial
action. The diminish in hydroxyl particle discharge from TheraCal following
7–14 days moving toward the physiological pH may make an ideal domain for the
vitality of pulp cell also, metabolic activity with the development of new
/reparative tertiary dentine.
Solubility: One of the
significant disadvantages of the conventional self-cure CaO and Ca(OH)2-based
materials is high solubility and disintegration after some time (inside 1–2
years after application) in tissue liquids, in this way neglecting to give a
changeless seal against bacterial intrusion. TheraCal demonstrated low
solubility esteems, though the high dissolvability of ProRoot MTA was likely
identified with its long setting time, with resulting crumbling of unset
material.(8) TheraCal LC is answered to have an appetite-forming capacity.
Resultant "apatite covering" assumes a key role is the repair of
dentine and mineralization. Its capacity to actuate the arrangement of
hydroxyapatite-like crystals could help in the chemical attach to dentine and
gives a good biological seal to protect the pulp.
The bond strength: between theraCal LC
and composite utilizing the totaletch method showed better bond quality values
when contrasted to the selfetch primer. TheraCal LC had higher bond strength
than Biodentine when layered with composite materials that are exceptionally
translucent influencing last restoration esthetic. Producer suggests setting it
in 1 mm layers and for 20 seconds by light curing.
Biological
properties:
theraCal prompted a broad pulp inflammatory response unlike MTA or Biodentin ,
which causes a higher level of irritation and it is poisonous to pulp
fibroblasts .The study credited this to the acrylic monomer Bis-GMA present in
the material
Clinical
applications:
Theracal received a great modification to overcome the disadvantages of MTA due
to the light curing ability and achieving the concept of '' single visit''.
Excellent Handling properties, good Sealing ability and good antimicrobial
property, make it a good choice as a pulp capping agent and also it is used as
base help to reduce sensitivity of dentin and providing a thermal barrier .
• BioDentin: Biodentine is calcium
silicate-based inorganic restorative cement can be used as direct and indirect
pulp capping material furthermore, publicized as' bioactive dentine
substitute'. It is supplied in pre proportioned capsule .The material is
guaranteed to have better physical and biological attributes looked at to other
tricalcium silicate cements, as (MTA) and Bioaggregate .
Conclusion:
Based on the previous studies we can say that, these materials have a promising
future and great demand because of its satisfactory advantages. It has also low
cost in comparison with root canal treatment; As DPC is not always the most
effective choice, But it is never the most costly option. (14) We expect demand
on these recent materials to increase and to receive a significant development.
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