Recent advances in Dental materials-Part 1

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Recent Advances in
Dental Materials
Part - I
Presenter:
Dr. Aastha Subba
Junior Resident
Department of Prosthodontics
And Crown-Bridge

z Dental Materials
§ Dental materials are the specially
fabricated materials, designed for use in dentistry.

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Dental Materials
Preventive Restorative Auxiliary
pit and fissure
sealants, liners,
bases, cement that
primarily release
fluoride
a) direct restorative
materials.
a) indirect restorative
materials.
impression materials,
casting investments,
gypsum cast and model
materials, dental waxes,
acrylic resins

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Development of the new and improvement
of the old - these are two earmarks of
advancement in the field of dental
materials.

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§ New dental materials must satisfy the following perennial,
requirements. They must:
1) Be non-toxic to human cells
2) Be toxic to microbes and fungi
3) Be able to form an excellent seal between the oral
cavity and underlying tooth structure
4) Exhibit an esthetically pleasing appearance

z5. Be sufficiently bioactive to stimulate in vivo repair of
tissues that have been damaged by disease, trauma
or dental treatment
6. Have properties similar to the tissue that is to be
repaired or replaced
7. Exhibit handling properties that allow ease of
manipulation and promote optimal clinical
performance

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N
T
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S
Recent Advances in
A. Impression materials
B. Bite Registration materials
C.Luting Agents
C
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N
T
S

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IMPRESSION MATERIALS
§ According to GPT-9, Impression material is any substance
or combination of substances used for making an
impression or negative reproduction .

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RECENT ADVANCES
IN

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Recent Advances in Alginate
1. Dustless alginates
§ These materials were developed to eradicate silicosis,
which is caused by the presence of diatomaceous earth
in the form of fillers in conventional alginate impression
materials.
§ to increase the density of siliceous fibers, these fibers
were coated with de-dusting agents like glycerin, glycol,
polyethylene glycol, and polypropylene glycol.

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§ Recently, sepiolite (natural mineral fiber-containing
magnesium silicate) are also added to the alginate
materials that helps in holding alginate particles together
to prevent the leaping of dust particles. This reduced the
dust generation from alginate impression materials during
dispension.
§ Numerous manufacturers also incorporate tetrafluoro-
ethylene to avoid the dust particles raising by forming the
cobweb during mixing.

z2. Alginate in the form of two-paste system
§ Alginates were developed in two-paste systems to prevent
the contamination of powder, and inconsistency in
dispensing a certain amount of powder.
§ It consists of base paste and catalyst paste.
§ The base paste contains soluble alginate, water, and
fillers, whereas catalyst paste contains calcium salts,
viscous liquids like liquid paraffin and magnesium
hydroxide as a pH stabilizer

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3. Chromatic alginates
§ Various color indicators are added to the alginate
impression materials.
§ These color indicators change the color of the alginate mix
as setting reaction taking place due to the change in the
pH.
§ This change in the color of the alginate mix facilitates
identification of the ideal consistency to load it into the tray
and make accurate impressions.

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4. Self-disinfected alginates
§ Various literatures have suggested that the conventional
disinfection procedures such as immersion and spraying
methods may lead to the unwanted dimensional changes
in the alginate impression as they are hydrophilic .

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§ Also
1. disinfection involves an overt effort or action;
2. spraying or immersing impression material with disinfectants
may cause a loss of surface detail
3. most of the disinfectants used for spray and immersion
techniques are irritants and, therefore, inhalation of the
disinfectant vapors may present health risks to the dental
team; and
4. toxic disinfectants may also result in the corrosion of metal
trays or abnormal dislodgement of the impression from the
tray.

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Therefore,
§ Numerous researchers have developed alginate
impression materials by incorporating disinfectant agents
in their compositions (mostly in the powder of the
impression material and few attempts into the mixing
liquid).
§ The disinfectant materials incorporated include quaternary
ammonium compounds, chlorhexidine, didecydimethyl
ammonium chloride.

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Conclusion: Chlorhexidine self-disinfecting irreversible
hydrocolloid impression material can exhibit varying degrees
of antibacterial activity without influencing the three
dimensional accuracy, flowability, and setting time.

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§ However, irreversible hydrocolloids containing
chlorhexidine have been found to exhibit longer gelation
times, and higher concentrations of chlorhexidine are
cytotoxic to human fibroblasts.
§ An additional disinfection process involving conventional
immersion or spraying technique is generally
recommended by the manufacturers even for the self-
disinfectant irreversible hydrocolloids
Kishore Ginjupalli, Rama Krishna Alla, Chaitanya Tellapragada,Lokendra Gupta, Nagaraja
Upadhya Perampalli,Antimicrobial activity and properties of irreversible hydrocolloid impression
materials incorporated with silver nanoparticles THE JOURNAL OF PROSTHETIC DENTISTRY
VOLUME 115, ISSUE 6, P722-728,

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§ Recently, researchers have experimented incorporating
different antimicrobial nanoparticles into alginate impression
materials.
§ Silver nanoparticles have a high surface area and are
nontoxic to the human body at low concentrations.
§ Even at higher concentrations, incorporating silver may not
increase the incidence of tissue irritation or toxicity because
of its low percutaneous absorption and the limited contact
time with the tissues.

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§ Silver nanoparticles have found to exhibit antibacterial
action against several species of bacteria, including some
multidrug-resistant bacteria.
§ They also exhibit antiviral and fungicidal properties.
§ The antibacterial action of silver is attributed to the ability of
positively charged silver ions to interact with negatively
charged bacterial cell membranes leading to increased cell
wall permeability and cell death.

z 5. Extended - pour Alginate
§ Due to syneresis and imbibition, it is unable to store the
alginate impression for a longer duration.
§ Attempts made by the manufacturers to address this
problem led to the development of Extended –pour
Alignate.
§ Cavex color change material can be preserved for about
100hrs and Extend a pour can be preserved up to 4 weeks

Objectives: The present study evaluated the effect of
storage time on dimensional stability of three
alginates: Hydrogum 5, Tropicalgin and Alginoplast.
Conclusion: Immediate pouring of alginate
impressions provides the highest accuracy in
reproducing the teeth and adjacent tissues; however,
this study demonstrated that pouring may be delayed
for up to five days without significant dimensional
changes using extended-pour (Hydrogum 5) alginates.

z6. Alginate with polyacrylamide incorporation
§ On mixing with water, conventional alginates tend to form a
grainy mass with lumps of unmixed material as the water
does not wet the powder easily.
§ A thickening and stabilizing agent such as 0.01- 0.25wt%
polyacrylamide were incorporated into the conventional
alginates resulted in improving the mixing characteristics,
and the formation of smooth alginate sol with water .

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RECENT ADVANCES IN
ELASTOMERIC

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Visible light cured polyether impression material
§ contain a polyether urethane dimethacrylate resin that
contains a diketone initiator and an amine accelerator.
§ The polymerization is photoinitiated by blue light in the
wave- length range of 400 to 500 nm.
§ Added to this is 40 % to 60 % silica filler.

z Advantages
§ long working time,
§ short setting time,
§ excellent dimensional stability,
§ Superior tear strength (6000 to 7500
gm/cm2. Highest among elastomers)
§ and good wettability,

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Alginate alternative impression
materials
§ These are basically addition cure polyvinyl siloxane (PVS)
§ can be stored for longer time before pouring without any
significant distortion in the resultant casts.
§ the accuracy of impressions may be unaltered even after
re-pouring of casts.
§ more accurate with regard to the surface detail reproduction

zCommercially available Alginate
Alternative impression materials

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§ When evaluation and comparison of the surface detail
reproduction and dimensional stability of irreversible
hydrocolloid alternatives with an extended-pour irreversible
hydrocolloid at different time intervals was done, it was
concluded that:
1.The irreversible hydrocolloid alternatives performed better
with respect to the surface detail reproduction and dimensional
change.
2. Irreversible hydrocolloid alternatives were more
dimensionally stable up to 120 h when compared to extended-
pour irreversible hydrocolloids
Kusugal P, Chourasiya RS, Ruttonji Z, Astagi P, Nayak AK, Patil A. Surface Detail Reproduction
and Dimensional Stability of Contemporary Irreversible Hydrocolloid Alternatives after Immediate
and Delayed Pouring. Contemp Clin Dent. 2018;9(1):20-25. doi:10.4103/ccd.ccd_676_17

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Hydrophilised Addition Silicone
§ A significant limitation of VPS impression
materials is their hydrophobicity.
§ This hydrophobicity is due to the presence of
hydrophobic, aliphatic hydrocarbon groups
surrounding the siloxane bond.

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§ There are 2 different aspects of the hydrophobic nature of
VPS impression materials.
1. The first aspect relates to the surface free energy of the
solid, polymerized VPS, and the high contact angle that
typically forms when polymerized VPS impressions are
wetted with dental gypsum materials.
2. The second aspect relates to the surface free energy of
the unpolymerized, liquid phase of the impression
material, and the ability or lack of ability of the liquid VPS
to wet oral tissues during impression-making.

z§ To overcome this limitation, manufacturers incorporated
intrinsic surfactants (nonylphenoxypolyethanol homologues).
§ These hydrophilic VPS impression materials have exhibited
increased wettability of the polymerized impression with
gypsum slurries.
§ However, when this impression material was used clinically in
the presence of moisture in the form of water, saliva,
crevicular fluid, or blood, decreased accuracy of the produced
impression was reported

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Sreeramulu Basapogu et al., Dimensional Accuracy of VPS Impression Materials; Journal of Clinical
and Diagnostic Research. 2016 Feb, Vol-10(2): ZC56-ZC59
§ In an invitro study done to compare the dimensional
accuracy of hydrophobic VPS and hydrophilic VPS using
monophase, single mix and double mix impression
techniques, it was concluded that:
1. Hydrophilic VPS yielded more dimensionally accurate
impressions than hydrophobic VPS using one step, two
step putty wash impression techniques.
2. In monophase technique, not much difference was found
between the hydrophilic and hydrophobic VPS impression
materials.

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Vinyl siloxane ether/ Vinyl polyether silicone
§ Vinyl siloxane ether incorporates the natural hydrophilicity
of conventional polyether materials along with the
desirable properties of vinyl polysiloxane materials, such
as elastic recovery and tear resistance.
§ consists of a copolymer of α,ω-divinyl
polydimethylsiloxane and α,ω-divinyl polyether
crosslinked by an organo- hydrogen polysiloxane .

z Advantages
§ Excellent flowability allows the material to get into the
narrowest sulcus crevices while ensuring high stability.
§ Remarkable hydrophilicity with an optimal wetting in a moist
environment and the lowest achievable contact angle (less
than 10° after 1 second).
§ Easy and fast, true-to-detail fabrication of casts without
fracture risk.

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§ It is odorless and tasteless, hence accounts for a
pleasant feel in the mouth.
§ It is compatible with commercially available
disinfectants.
§ gives the operator the option of immediate pouring of
casts or else the impression may be disinfected and
transported to the laboratory for pouring at a later time

zPolyvinyl Siloxane containing nanofillers
§ Recently, silica nanofillers are
integrated in PVS, producing a
unique addition of siloxane
impression materials.
§ The nanoparticles contained inside
the silicone increase its flowability to
reach the less accessible spaces of
the gingival sulcus.

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Advantages
§ Resistance to deformation
§ Excellent elastic recovery
§ High dimensional stability

Laboratory comparative study of wettability,
dimensional changes, flexibility and tear resistance
of two recent elastomeric impression materials.
Sheta MS, El-Shorbagy ZA, Abdel Karim UM, Abd
Alla S.
Tanta Dent J 2017;14:89-95

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Conclusion
§ Contact angle measurement showed VPES and PE which
recorded the highest wettability.
§ PVS containing nanofillers showed the greatest
dimensional stability
§ PE, VPES and PVS recorded higher flexibility than PVS
containing nanofillers
§ PVS containing nanofillers and VPES showed the highest
tear resistance.

Digital Impression
Indirect Digital
Impression
Direct Digital
Impression

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How does direct digital impression making
work?
§ After the tooth preparation is complete and the tissues are
retracted, the tooth is dried and readied for scanning.
§ Scanners use either a series of static images or a stream of
video images to capture the geometry of the tooth
preparation.
§ The scanned data are visualized and design of restorations
are then fabricated.

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How does indirect digital impression making
work?

zAdvantages of Direct Digital Impression
§ Less patient discomfort
§ Time-efficient
§ Simplified clinical procedures
§ No more plaster casts
§ Better communication with the dental technician
§ Better communication with patients

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Disadvantages of Direct Digital
Impression
§ Difficulty detecting deep marginal lines of prepared
teeth
§ Learning curve
§ Purchasing and managing costs

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Advantages of Indirect Digital Impression
§ Not affected by oral conditions such as saliva, blood,
limited spacing, preparation shape, and scanning
position which may affect the accuracy of the
impression made.

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In vivo marginal gaps after intraoral and
extra oral scanning
§ Considerable studies indicate that the marginal gaps
obtained with intraoral scanners are equal to or better
than those obtained with extraoral scanners.
§ Ahrberg et al. reported that the marginal fit of fixed dental
prostheses was more accurate after direct digitalization
than after indirect digitalization.

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Examples of Intra-oral scanners
§ 3Shape - TRIOS 4
§ Dentsply Sirona - CEREC Primescan
§ Medit - i500
§ Align – iTero Element 5D
§ Carestream Dental - CS 3600
§ Planmeca - Emerald S

zAre optical impressions as accurate
as conventional impressions?
§ The main feature an IOS should have is accuracy.
§ To date, the scientific literature considers the accuracy of
optical impressions clinically satisfactory and similar to
that of conventional impressions in the case of single-
tooth restoration and fixed partial prostheses of up to 4–5
elements.

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§ However, optical impressions do not appear to have
the same accuracy as conventional impressions in
the case of long-span restorations such as partial
fixed prostheses with more than 5 elements or full-
arch prostheses on natural teeth or implants
Mangano et al. Intraoral scanners in dentistry: a review of the current
literature BMC Oral Health (2017) 17:149

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Conclusions
• The digital impression technique was more efficient than the
conventional impression technique.
• When compared with the conventional impression technique,
the digital impression technique was accepted as the preferred
and effective technique, according to the subjects’ perception.
• The treatment comfort of the digital impression technique was
higher than that of the conventional impression technique
when it was performed by an experienced operator.

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Inter-occlusal recording materials
§ According to GPT 8: “The inter-occlusal record is a
registration of the positional relationship of the opposing
teeth or arches.”

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§ The ability of the practitioner to relate and mount casts
may have more impact on the quality of the restoration
and the efficient use of clinical time.
§ An error of the former will likely result in inter-cuspal as
well as excursive occlusal discrepancies.

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RECENT ADVANCES
IN
INTER-OCCLUSAL
RECORDING MATERIALS

z T-Scan
§ T-Scan is a digital occlusion analysis system that records
and measures tooth contact, force, and timing in real-time
using a thin, flexible, pressure-sensitive bite transducer
embedded in a dental arch-shaped recording sensor.

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§ The occlusal data obtained from T-Scan can be displayed
graphically for analysis in two or three dimensions or as a
dynamic movie that can be analyzed stepwise.

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Advantages
§ It can measure location and timing of tooth contact and
occlusion in 3D.
§ Premature contact and interferences can be identified in the
dynamic occlusion instead of static occlusion.
§ Distribution of force per tooth and distribution of forces in two
halves of the jaw can be calculated.
§ Symmetry of force relationships can be analyzed in the
dental arch

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Drawbacks
§ the sensors do not have the same accuracy among
themselves and have fewer contacts than
conventional methods such as articulating papers.
§ The sensitivity of the T-scan sensors has been
reported to decrease or disappear when the sensors
are used more than once.

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§ Moreover, the thickness of the sensors is 0.1mm
which is as thin as possible for a sensor but still
relatively thicker compared to other occlusal
indicators like articulating silk which may inhibit
proprioception.

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Applications of T-Scan
§ T-Scan helps identify premature contacts, stability issues, and
causes of sore spots when the dentures are being delivered.

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§ T-scan warn users if the implant is sustaining a large percentage of
occlusal force or hitting early in the bite sequence thus, protecting
implants from damaging occlusal forces before it becomes a
problem.

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§ It helps the dentist analyze the
patient’s occlusion before, during
and after splint therapy and
makes it easier to identify areas
that need adjustment in order to
ensure patient comfort, a
balanced appliance, and a
harmonized occlusal scheme.

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§ T-Scan helps to analyze the
occlusion of a patient
undergoing restoration
procedures and aids in
identifying regions of
excessive or non-uniform
force, giving the dentist
knowledgeable control over
the adjustment process.

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Photo-Occlusion
§ In this system, a thin photoplastic film layer is applied on the
occlusal surface of the teeth; the patient then is asked to
occlude on the film layer.
§ The film layer is removed from the mouth and inspected
under a polariscope light. The results are transferred to a
graphic occlusal scheme.

z Occlusion Sonography
§ It detects tooth contact by the sounds generated during
mouth closure.
§ The relationship between graphic records of sounds of
occlusion and the types of tooth contact which produced
them was investigated by rotating prism camera at
approximately 1,000 frames per second
§ The sliding of the teeth over each other was seen on the
films as low amplitude vibrations and the tooth impacts as
high amplitude .

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Transparent Acetate Sheet
§ It is based on occlusal sketch
technique that aims to provide a
simple and reliable means of
recording and transferring
information about the location of
marked occlusal contacts.
ontacts. The sketch consists of an acetate sheet on which a
hematic representation of the teeth is drawn, including the
cclusal surfaces of the posterior teeth, the palatal surfaces
the maxillary anterior teeth and the labial surfaces of the
andibular anterior teeth. The same authors concluded that
is technique demonstrated interoperator
intraoperator reliability in recording
lusal contacts in vitro. The aim of the
lusal sketch technique is
rovide a simple and reliable means of
rding and transferring information about
location of marked occlusal contacts.
may also be used by the technicians to verify occlusal
ontacts when articulating casts and fabricating indirect

z
§ the sketch consists of an acetate sheet
on which a schematic representation of
the teeth is drawn, including the
occlusal surfaces of the posterior teeth,
the palatal surfaces of the maxillary
anterior teeth, and the labial surfaces
of the mandibular anterior teeth.
RESULTS
Fig. 1 The occlusal sketch acetate sheet marked on a 1mm2 grid

2 399
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TYPEWRITER RIBBON
§ Ziebert and Donegan used typewriter ribbon to mark
supra-contacts or occlusal interferences in their
patients for occlusal adjustments.
§ Interferences were marked with typewriter ribbon and
contacts verified with 0.00l-inch shim stock

z Digital Bite Registration
§ CAD/CAM systems have been introduced that incorporate
a new optical bite registration method to determine the
occlusal relationship between the abutment tooth and its
antagonist using CAD software.
§ With these systems, an intraoral camera can be utilized
for optical bite registration as well as optical impressions
of the dentition.

z
§ Optical bite registration is based on optical impressions
of the buccal surface of the dentition from the buccal side
during clenching at the intercuspal position, without any
bite registration materials.
§ These optical impression data are used to fabricate
restorations at the chair-side, and it is possible to replace
the restorations on the same day.

z Scannable Bite Registration Material
§ In most cases, once isolation of the prepared tooth is
achieved, the digital data-capturing step is accomplished
with the acquisition camera.
§ There are certain situations where the clinician finds it
difficult to obtain the required data intraorally.
a. difficulty in achieving sufficient isolation for powdering
b. inaccessibility of the acquisition camera due to limited
opening of the mouth

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§ Scannable bite registration materials are basically
addition-reaction polysiloxane (vinylpolysiloxane) with the
fillers incorporated.
§ The filler make the polymer more opaque and prevent light
scattering. Therefore, images of the bite registration can
be captured directly with a laser scanner.

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Triple Tray Impression Technique
§ The procedure is alternatively called closed-mouth
impression, dual-arch impression, or double-arch
impression.
§ Three-way trays have several advantages, a main one being
the saving in time and money.

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§ Closed-mouth impressions are 80% more comfortable
than open-mouth techniques. This is especially important
for patients who have gagging problems.
§ Patients may prefer this technique because impression
material is in their mouth only once as the one impression
yields a master cast, the opposing cast and an inter-
occlusal record.

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§ Use of the 3-way tray impression
technique should be limited to single
units.
§ The relation to the condyles is not
maintained when casts are mounted
using 3-way trays, thus limiting the
use of 3-way trays to those cases
where the patient has canine
disocclusion.

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§ A 3-way impression technique is indicated only when the
desired final treatment position for the teeth is in MIP.
§ When the impression is poured, the weight of the die stone
may distort the impression and result in an inaccurate die.

z
Luting Agents
§ According to the Phillips Science of Dental Materials
luting agent is a viscous cement-like material that fills a
gap between bonded materials.

z§ Luting agents can be classified
I. According to the length of time they are expected to stay
in function: provisional or definitive luting agents.
II.According to setting mechanism,
§ luting agents those presenting an acid-base reaction
§ those setting by polymerization

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RECENT ADVANCES
IN
LUTING AGENTS

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I. Resin modified Glass ionomer Cement
§ To create a longer working time yet quick setting time, the
concept of resin-modified glass ionomer (RMGI) was
introduced.
§ RMGIC maintain the benefits of fluoride ion release and
adhesion of glass ionomer cements while overcoming their
disadvantages with the more favourable attributes of resin-
based composites.

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The essential components of true RMGIs are as follows

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Setting Reaction
of
GIC vs RMGICs

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Setting Reaction of Resin modified GIC

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§ RMGIC suffer from a disadvantage inherent in all light curing
systems. All light-curing systems allow the penetration of
visible light to only a limited depth.
§ Biocompatibility of Resin modified GIC
§ The key component that is known to be released from resin-
modified glass-ionomers is HEMA.
§ HEMA has the potential to be systemically distributed from
its location in the mouth and to be the source of adverse
effects in patients.

z
§ Dental personnel, too, are at risk, as manual contact with
unprotected skin can lead to allergic reactions, ranging
from the relatively mild (i.e. contact dermatitis) to the
severe.
§ Since HEMA is volatile, there is also a risk of inhalation of
HEMA vapor.

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Clinical handling of resin-modified glass-ionomers
1. Ensure that the work space is well ventilated;
2. avoid inhalation of HEMA vapor;
3. touch unset material only with instruments, never hands,
even when wearing gloves;
4. avoid contact of resin-modified cement (set or unset) with
the oral mucosa of the patient;

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5. use with a liner to prevent diffusion of HEMA to the
pulp;
6. build-up restorations in increments to enable each
increment to be properly through-cured, thereby
reducing the amount of HEMA available for release;
7. light-cure unused remnants of cement before
disposal, to reduce the possibility of exposure to
volatile HEMA vapor.

z Tri-Cure Glass Ionomer Cement
§ Tri-Cure Glass Ionomer System overcomes the
disadvantages of light cured glass ionomers while
maintaining all their advantages.
§ Tri-Cure Glass Ionomer System has the following three
distinct curing reactions:
1. Acid-base glass ionomer reaction (initiated when powder
and liquid are mixed and can proceed in the dark).

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2. Photoinitiated free radical methacrylate cure (initiated
when the powder/liquid mix is exposed to light and
occurs only where light penetrates).
3. Dark cure free radical methacrylate cure
(initiated when powder and liquid are mixed and can
proceed in the dark).

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Nanotechnology in GIC
§ Nanotechnology involves the use of systems,
modifications or materials which have the size in the range
of 1–100 nm.
§ It is proposed that the incorporation of nanoparticles into
glass powder of glass ionomers leads to wider particle size
distribution, which results in higher mechanical values.

z
§ De Caluwé et al. showed that doping conventional GICs
with nano-sized glass particles can decrease the setting
time and enhance the compression strength and elastic
modulus.
§ When compared to conventional GIC the nanoleakages as
well as microleakages between material dentin interface is
less in nanoparticles incorporated GIC as new crystals of
hydroxyapatite forms at the interface of tooth and
nanoparticles incorporated GIC.

z
§ Various types of nano-size powders have been incorporated
to the glass powder component
a) Modification Using Nano-Apatite
b) Modification with Nano-Sized HAp/Zr, CaF2 and TiO2
Particles
c) Nano-Filled Resin-Modified Glass Ionomer Cements

z
§ However, commercially available nano-filled RMGIC
(Ketac Nano) does not hold any significant advantage in
terms of flexural strength and tensile strength and
bonding properties of nano-filled RMGIC are still a
matter of concern.
§ And only few studies focusing on the nano-modification
of GIC have concentrated on effects they might have on
the pulpal cells.

z
§ Hence, more mechanical, biological studies, and
eventually, clinical trials are needed and essential to
ascertain the status of nano-modified GICs in clinical
practice.

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Calcium aluminate GIC
§ It is a hybrid composition of
Calcium Aluminate and glass
ionomer, that when combined
with its liquid, undergoes an
acid-base reaction.

z
§ The main ingredients in the powder of this hybrid
cement are calcium aluminate, polyacrylic acid,
tartaric acid, strontium-fluoro-alumino-glass, and
strontium fluoride.
§ The liquid component contains 99.6% water and
0.4% additives for controlling setting.

z
§ The glass ionomer components of the cement are
responsible for the properties such as viscosity, setting time,
and strength.
§ The calcium aluminate contributes to a basic pH during
curing.
§ The poly-acrylic acid has a dual function:
a. it is cross-linked by Ca2+ ions leached from both the
soluble glass and the calcium aluminate.
b. acts as a dispersing agent for the calcium aluminate.

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§ pH of the cement~ 8.5 after 3-4 hours of setting time.
§ This mild, lasting alkalinity allows continuous formation
of apatite when adjacent to phosphate containing
solutions of dentin.
§ Additionally, the alkalinity prevent the ionomer glass from
continuously leaking over time.
§ It also helps with pulpal compatibility and also has
antimicrobial effect.
Advantages

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§ Resin cements are low-viscosity versions of
restorative composites.
§ The success of attaching unfilled resin to etched
enamel gave rise to the concept of using resins to
bond fixed prostheses to abutments.

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Classification of Resin cements
I. According to the process of matrix formation
Ø self-cured,
Ø light cured, and
Ø Dual cure

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II. According to the adhesive technique
Ø total etch (acid + adhesive + cement),
Ø self-etching (Primer+ cement)
Ø Self adhesive (No etching, priming and
application of bonding agent)

z
Composition
a) Organic polymer matrix: crosslinked matrix of
dimethacrylate monomer (Bis-GMA and UDMA)
b) Inorganic Fillers: Quartz, glass
c) Coupling agents: Organosilanes
d) Initiator and Accelerator system: Camphoroquinones,
peroxides and amines

z
Setting Reaction
§ Occurs in 3 stages:
1) Initiation stage
2) Propagation stage
3) Termination stage

z
Advantages
§ Versatility
§ Adequate tensile and
compressive strength
§ Low solubility
§ Esthetics
§ Hard to remove excess
cement
§ Technique sensitive
adhesive technique
§ High cost
Disadvantages

z
Self Adhesive Resin Cements
§ These cements have evolved as a result of the
desire of clinicians/operators to simplify the luting
procedures for resin cements and, more
importantly, to shorten their ‘window of
contamination’.

z
§ SACs are dual-cured resin
cements which can bond to an
untreated tooth surface that is
neither micro-abraded nor pre-
treated with an etchant, primer or
bonding agent.

z Composition
§ The basic components of a SAC consist of an organic matrix
which is a blend of polymerizable methacrylates,
dimethacrylates and polymethacrylates, along with acid
functionalized monomers, predominantly methacrylate
monomers with either carboxylic acid groups, as with 4-
META and PMGDM, or phosphoric acid groups, as with 10-
methacryloxydecyl dihydrogen phosphate (MDP)

z
Bonding mechanism
§ The bonding mechanism is based on chemical interaction
and micro-mechanical retention with the adhesive
substrate, along with the simultaneous
demineralization/infiltration of the smear
layer and the underlying tooth structure.
§ The multifunctional monomers create a low pH on
contacting water or moisture from the tooth.

z
§ Like self-etch adhesives, the pH of a freshly mixed
cement may range from 1.5–3.
§ This low pH etches the tooth structure (enamel and
dentine) and the cement penetrates the etched tooth
surface, creating a micromechanical bond with the tooth
when the cement polymerizes.

z
§ In the initial reaction, as the cement sets, water is
formed which produces the cement’s initial
hydrophilicity that improves the marginal adaptation
and the pH increases to neutrality.
§ During the secondary setting reaction, the produced
water is consumed by the forming cement matrix,
developing a hydrophobic matrix, which has low
solubility, low expansion and long-term stability

z
Self Adhesive Resin Cement
Vs
Resin and Conventional
cements

z
§ The physical properties of SACs can be considered
equivalent to, or slightly lower than, the non self-adhesive
resin cements, but greater than the non resin-based
cements.
§ The bond strength of SACs is less than the total-etch but
is equivalent to self-etch cements and greater than resin-
modified glass ionomers.

z
§ SACs can withstand more fatigue cycles than the zinc
phosphate but no significant difference is noted
between the SACs and the other resin cements
§ Unlike the total-etch resin cements, SACs show less
incidence of post- operative sensitivity.
§ Self-adhesive resin cements have expansion rates less
than resin- modified glass ionomers but higher than
total-etch resin cements

z
§ Marginal adaptation/fit of restorations luted with SACs is
observed to be better than the resin-modified glass
ionomer and the compomer cements and equivalent to
the conventional total-etch and self-etch resin cements.
§ The retentive values for crowns cemented with SACs is
reported to be greater than the conventional cements and
equivalent to that of self-etch resin cements

z
References
§ Restorative Dental materials:G Craig & John M Powers-11th edition2002.
§ Phillips Science of dental materials: Anusavice; 11th edition
§ Alaghari, Sahithi & Velagala, Surekha & Alla, Rama Krishna & Av, Ramaraju.
(2019). Advances in alginate impression materials: a review. International
Journal of Dental Materials. 1. 55-59. 10.37983/IJDM.2019.1203.
§ Kishore Ginjupalli, Rama Krishna Alla, Chaitanya Tellapragada,Lokendra
Gupta, Nagaraja Upadhya Perampalli,Antimicrobial activity and properties of
irreversible hydrocolloid impression materials incorporated with silver
nanoparticles THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME
115, ISSUE 6, P722-728,

z
§ Wang J, Wan Q, Chao Y, Chen Y. A self-disinfecting irreversible
hydrocolloid impression material mixed with chlorhexidine
solution. Angle Orthod. 2007;77(5):894-900. doi:10.2319/070606-277
§ Rohanian A, Ommati Shabestari G, Zeighami S, Samadi MJ,
Shamshiri AR. Effect of storage time of extended-pour and
conventional alginate impressions on dimensional accuracy of casts. J
Dent (Tehran). 2014;11(6):655-664.
§ Kusugal P, Chourasiya RS, Ruttonji Z, Astagi P, Nayak AK, Patil A.
Surface Detail Reproduction and Dimensional Stability of
Contemporary Irreversible Hydrocolloid Alternatives after Immediate
and Delayed Pouring. Contemp Clin Dent. 2018;9(1):20-25.
doi:10.4103/ccd.ccd_676_17

z
§ Sreeramulu Basapogu et al., Dimensional Accuracy of VPS Impression
Materials; Journal of Clinical and Diagnostic Research. 2016 Feb, Vol-
10(2): ZC56-ZC59
§ Laboratory comparative study of wettability, dimensional changes,
flexibility and tear resistance of two recent elastomeric impression
materials. Sheta MS, El-Shorbagy ZA, Abdel Karim UM, Abd Alla S.
Tanta Dent J 2017;14:89-95
§ Mangano et al. Intraoral scanners in dentistry: a review of the current
literature BMC Oral Health (2017) 17:149
§ Zirconia: cementation of prosthetic restorations. Literature review. M.
GARGARI, F. GLORIA, E. NAPOLI, A.M. PUJIAORAL & Implantology -
Anno III - N. 4/2010

z§ Dr.Rohit Dhoot, Dr.Sarvesha Bhondwe, Dr.Vishal Mahajan, Dr.Sourabh
Lonare, Dr.Kuldeep Rana. Advances in Glass Ionomer Cement (GIC): A
Review. IOSR Journal of Dental and Medical Sciences (IOSR-JDMS)e-ISSN:
2279-0853, p-ISSN: 2279-0861.Volume 15, Issue 11 Ver. III (November.
2016), PP 124-126.
§ Nicholson JW, Czarnecka B. The biocompatibility of resin-modified glass-
ionomer cements for dentistry. Dent Mater. 2008;24(12):1702-1708.
doi:10.1016/j.dental.2008.04.005
§ Deepthi, B. & Rakshagan, V. & Jain, Ashish. (2018). Recent interocclusal
record material for prosthetic rehabilitation - A literature review. Drug
Invention Today. 10. 2004-2009.
§ Pesun IJ, Swain VL. Three-way trays: easy to use and abuse. J Can Dent
Assoc. 2008;74(10):907-911.
§ pyakurel, Hema. (2013). Mechanism, accuracy and application of T-Scan
System in dentistry-A review.

Recent advances in Dental materials-Part 1

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