Interim fixed or removable which provide esthetics enhancement, stabilization

 

Interim
prosthesis is a mandatory part of fixed prosthodontics treatment. Temporary
crown must be placed from initial tooth preparation till the definitive
prosthesis is fabricated. Temporary restoration is that prosthesis which is
either fixed or removable which provide esthetics enhancement, stabilization or
function over a limited period of time. 20

Provisional restoration plays a key role for
diagnosing the complex prosthodontics treatment related to change in vertical
dimension of occlusion, relationship of centric occlusal contact, anterior
guidance, lip support, length of the tooth, position of the incisal edge,
occlusal plane or plane of incisors. 20

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Prepared
tooth needs protection from all type mechanical, physical, bacterial
contamination and thermal injures and thus the importance of interim
restoration or temporary crown plays a significant role. key1 The
success of a fixed prosthesis is only possible from a good temporary
restoration. Due to increase in high esthetics and cosmetic concern the
temporary restoration have become a diagnostic tool rather than a space
maintainer. 17

Chemical reactions turn the fluid form of the
temporary materials in solid hard substance which is durable and tough enough
to withstand the masticatory load. With different type of composition
temporisation material can be classified in broadly five types they being
28

i)                   
Chemically activated auto-polymerizing
resin.

ii)                 
Heat activated acrylic resins.

iii)               
Light activated acrylic resin.

iv)               
Dual light and chemically activated
acrylic resin.

v)                 
Alloy.

 

Most
prevailing material for fabricating custom provisional restoration is acrylic.
Methyl methacrylate introduced in 1940 is the most widely used temporisation
material which is available in powder and liquid formulations, mixed in
stipulated proportion gives a solid mass by chemical reaction 28.
Researches in the field of material sciences for temporary crown had led to the
introduction of newer temporisation material such as Bis-acryl composite resin (eg.
Protemp 4) Bis-acryl composite nanofilled resin (eg. Structur 3) and Bis-Gma
resins. 28 Superior technology evolving in the field of dentistry
produces fine temporary restorations made from CAD/CAM technology. This
technology use poly-methyl methacrylate of higher strength so that it can
withstand milling process therefore has high strength and better marginal
adaptation. 1

Newer
material arrival make it obvious for a test for mechanical properties mainly
wear resistance, fracture resistance and surface hardness to sustain in the
oral cavity tolerating the force of mastication till the final prosthesis is
fabricated. 23 During mastication the
highest force is applied on the temporary fixed prosthesis, so material must be
of durable quality and have wear resistance and sufficient strength 13
so that it does not break off during loading. 17

In this study newer advanced materials are taken in
to consideration such as CAD/CAM milled PMMA reinforced by methacrylate acid
ester based cross-linked polymer, Self Cure PMMA, Bis acryl composite resin
PROTEMPTM 4, Nanofilled Bis-acryl STRUCTUR 3. The mechanical
properties of the newer advanced materials had been taken in to consideration
such as Wear Resistance, Fracture resistance and surface hardness.

CAD/CAM is a digital procedure where the precision
milling of a block of PMMA or waxes or metal can be milled by a software guided
milling machine. The blocks used for milling in an CAD/CAM machine are
generally industrially made under controlled environment so incorporation of
air void or non-homogeneous mixing of the component of the block are totally
out of question. The mechanical properties of the milled prosthesis also remain
intact. Thus there is no other better alternative to select the CAD/CAM
fabricated PMMA temporary crowns as a control for this study. key1

Wear resistance
being an important property of temporary crown, higher the wear resistance
lesser is the chance of getting perforation.
Fracture
resistance is the property by which a temporary crown withstands the
masticatory load during chewing. Repeated chewing increase the masticatory
loads. More resistant to fracture, more is the longevity of a temporary crown. Surface hardness is that property which able the
temporary crown from getting deformed. If proper occlusal contact is to be
maintained then deformity of the temporary crown cannot be hailed. According to
the conducted study Vickers hardness test was done.

Protemp had undergone many researches, Omid Savabi et al in the year 2013 stated that hardness
and wear resistance of the temporary material has no liaison. However he determined
in his studies Protemp has highest wear resistance. 5 Yilmaz A. et al in the year 2007 suggested that bis-acryl composite material
Protemp revealed higher strength value than autopolymerising PMMA resins. He
also stated that micro hardness of many materials decreased over time but
bis-acryl resin Protemp had a higher microhardness than conventionally
fabricated PMMA temporary crowns. 6 Michael Patras et al in the year 2012
and Ana M.
Diaz-Arnold et al in the year 1999 both mentioned that use of bis-acryl resin as
temporary material has exalted the strengthening effect. 9 10 David G. Gratton et al in the year 2004 stated that Bis – acryl resin composite temporary
material have better micro-hardness than PMMA so better wear resistance. But
fracture resistance is better in PMMA than bis-acryl resin. 20 Jack H. Koumjian et al in the year 1990 studied the
fracture resistance of the materials used for temporisation. He stated that
Protemp being the strongest material in
wet study during his time of study. 4

            Wear
resistance of ProtempTM 4 is 0.0021% which has calculated by the volumetric
loss after being subjected to the Chewing Simulator which stands the forth position
amongst the other three considered in the study. Fracture resistance tested in
an universal testing machine by 4 point bending test ProtempTM 4 had bagged the third
position with a mean of 42.65N. ProtempTM
4 had a fairly 25.35VHN of surface harndness and is the second best
amongst all the four material concerned.

            Structur 3 showed little better
result in wear resistance of .0019% volumetric loss which is better than
ProtempTM 4, whereas the results for stuructur 3 for facture
resistance is 38N and surface hardness is 17VHN which holds the last postion in
this study analysis table. 

             Self cure PMMA the widely used material for
temporisation and had been studied by various authpors. Surya
Prakash Sharma et al in
the year since 1940 PMMA is widely used temporary restoration material due to
is good wear resistance, durability, good polish ability and esthetic; though
successful its use is gradually fading with the emergence of newer material as
bis acryl resin with the easy mode of manipulation and better esthetics.36
Anil
K Gujjari et al in the year 2013
also stated that bisacryl was prone to damage as its fracture resistance is
less as the PMMA crown which has better fracture resistance. 2 Resin S acryY. I.
Osman et al in the year 1993
studied that highest resistance is offered by PMMA crown than bisacryl resin
and stated that PMMA material are expected to give better results is terms of
fracture resistance than other materials. 37

            In
this conducted study it has been observed that Self cure in wear resistance of
wear resistance is 0.0015% of total volumetric loss which makes it the 2nd
best, fracture resistance being 53.5N which bagged it the second position and
for surface harness it stood third with 21VHN.

            Recent
advanced technology that had been put into the field of dentistry is CAD/CAM
milling of Blocks made of biocompatible materials fabricated by industrial
control. CAD/CAM milled PMMA also available for Interim Restoration purpose.
Mohammad M. Rayyan et al in the year 2015 suggested that resin matrix
composition affects the surface hardness, wear resistance and fracture
resistance of the temporary materials. However he also stated that being
industrially fabricated CAD/CAM PMMA exhibits better mechanical properties than
those of manually fabricated temporary crowns. Hence CAD/CAM fabricated
temporary crowns can be used in long term restorations. key1  Vanessa Alt et al in the year 2011had also
commented that CAD/CAM fabricated prosthesis shows more mechanical strength than
of directly fabricated interim prosthesis even if same material is concerned.
7 Again Isil Karaokutan et al in the year 2015 stated that CAD/CAM fabricated
temporary crowns; the latest trend reduces the risk of failures and chair side
time. CAD/CAM fabricated temporary crowns shows higher fracture strength than
conventionally fabricated PMMA crowns. 8 Ronald D. Perry et al in
the year 2012 suggested that CAD/CAM fabricated temporary crown having better
physical properties can sustain up-to a year in difficult cases too. 11

Claudia Florina Andreescu et al in the year 2017
stated that CAD/CAM fabricated temporary crowns are have good fracture strength
and fracture resistance so they tend not to fracture under load as CAD/CAM
materials have almost zero porosity and homogenisity is very high so they have
high resistance to fracture. 12   Marwa Eltayeb et al in
the year 2014 also said that CAD/CAM fabricated temporary crowns have higher
fracture resistance and wear resistance than the conventionally fabricated
crown. 23

In this
conducted study it has been obtained that CAD/CAM fabricated PMMA
temporary crowns showed the best wear resistance amongst the other group of
0.0081% of volumetric weight loss, 66.20N of fracture resistance and surface hardness of 27.85VHN.

 

Flávia Pires Neves Pascutti et al in the year 2017 also stated that CAD/CAM PMMA temporary crowns
are have less work time, cost-effective and quality control, hence are more
suitable for prolong treatment. 30 More over as per the outcome of the
conducted study it can be said that the second best material to use as
temporary restoration is PMMA made by conventional method. Z Vally et al in the year 2013 also said the same thing that this fracture
resistance makes the Self Cured PMMA 
suitable for day to day practise.32 Mustafa Zortuk1 et al in the year 2010 stated that  fracture resistance of PMMA crowns
are more than that of bisacryl resin making PMMA the the second best
temporisation material. 34

 

Lately it must be
kept in mind that as in-vitro studies are controlled study it is
difficult to co –relate with the inta-oral or clinical performance but an
inference can be drawn about the best suitable material available that can be
used as a interim restoration. 

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