Interimprosthesis is a mandatory part of fixed prosthodontics treatment. Temporarycrown must be placed from initial tooth preparation till the definitiveprosthesis is fabricated. Temporary restoration is that prosthesis which iseither fixed or removable which provide esthetics enhancement, stabilization orfunction over a limited period of time. 20 Provisional restoration plays a key role fordiagnosing the complex prosthodontics treatment related to change in verticaldimension of occlusion, relationship of centric occlusal contact, anteriorguidance, lip support, length of the tooth, position of the incisal edge,occlusal plane or plane of incisors.
20 Preparedtooth needs protection from all type mechanical, physical, bacterialcontamination and thermal injures and thus the importance of interimrestoration or temporary crown plays a significant role. key1 Thesuccess of a fixed prosthesis is only possible from a good temporaryrestoration. Due to increase in high esthetics and cosmetic concern thetemporary restoration have become a diagnostic tool rather than a spacemaintainer. 17 Chemical reactions turn the fluid form of thetemporary materials in solid hard substance which is durable and tough enoughto withstand the masticatory load.
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With different type of compositiontemporisation material can be classified in broadly five types they being28 i) Chemically activated auto-polymerizingresin.ii) Heat activated acrylic resins.iii) Light activated acrylic resin.iv) Dual light and chemically activatedacrylic resin.
v) Alloy. Mostprevailing material for fabricating custom provisional restoration is acrylic.Methyl methacrylate introduced in 1940 is the most widely used temporisationmaterial which is available in powder and liquid formulations, mixed instipulated proportion gives a solid mass by chemical reaction 28.Researches in the field of material sciences for temporary crown had led to theintroduction of newer temporisation material such as Bis-acryl composite resin (eg.Protemp 4) Bis-acryl composite nanofilled resin (eg.
Structur 3) and Bis-Gmaresins. 28 Superior technology evolving in the field of dentistryproduces fine temporary restorations made from CAD/CAM technology. Thistechnology use poly-methyl methacrylate of higher strength so that it canwithstand milling process therefore has high strength and better marginaladaptation. 1Newermaterial arrival make it obvious for a test for mechanical properties mainlywear resistance, fracture resistance and surface hardness to sustain in theoral cavity tolerating the force of mastication till the final prosthesis isfabricated. 23 During mastication thehighest force is applied on the temporary fixed prosthesis, so material must beof durable quality and have wear resistance and sufficient strength 13so that it does not break off during loading. 17In this study newer advanced materials are taken into consideration such as CAD/CAM milled PMMA reinforced by methacrylate acidester based cross-linked polymer, Self Cure PMMA, Bis acryl composite resinPROTEMPTM 4, Nanofilled Bis-acryl STRUCTUR 3. The mechanicalproperties of the newer advanced materials had been taken in to considerationsuch as Wear Resistance, Fracture resistance and surface hardness.
CAD/CAM is a digital procedure where the precisionmilling of a block of PMMA or waxes or metal can be milled by a software guidedmilling machine. The blocks used for milling in an CAD/CAM machine aregenerally industrially made under controlled environment so incorporation ofair void or non-homogeneous mixing of the component of the block are totallyout of question. The mechanical properties of the milled prosthesis also remainintact. Thus there is no other better alternative to select the CAD/CAMfabricated PMMA temporary crowns as a control for this study. key1Wear resistancebeing an important property of temporary crown, higher the wear resistancelesser is the chance of getting perforation.Fractureresistance is the property by which a temporary crown withstands themasticatory load during chewing.
Repeated chewing increase the masticatoryloads. More resistant to fracture, more is the longevity of a temporary crown. Surface hardness is that property which able thetemporary crown from getting deformed. If proper occlusal contact is to bemaintained then deformity of the temporary crown cannot be hailed. According tothe conducted study Vickers hardness test was done.Protemp had undergone many researches, Omid Savabi et al in the year 2013 stated that hardnessand wear resistance of the temporary material has no liaison.
However he determinedin his studies Protemp has highest wear resistance. 5 Yilmaz A. et al in the year 2007 suggested that bis-acryl composite materialProtemp revealed higher strength value than autopolymerising PMMA resins. Healso stated that micro hardness of many materials decreased over time butbis-acryl resin Protemp had a higher microhardness than conventionallyfabricated PMMA temporary crowns.
6 Michael Patras et al in the year 2012and Ana M.Diaz-Arnold et al in the year 1999 both mentioned that use of bis-acryl resin astemporary material has exalted the strengthening effect. 9 10 David G. Gratton et al in the year 2004 stated that Bis – acryl resin composite temporarymaterial have better micro-hardness than PMMA so better wear resistance. Butfracture resistance is better in PMMA than bis-acryl resin. 20 Jack H. Koumjian et al in the year 1990 studied thefracture resistance of the materials used for temporisation.
He stated thatProtemp being the strongest material inwet study during his time of study. 4 Wearresistance of ProtempTM 4 is 0.0021% which has calculated by the volumetricloss after being subjected to the Chewing Simulator which stands the forth positionamongst the other three considered in the study. Fracture resistance tested inan universal testing machine by 4 point bending test ProtempTM 4 had bagged the thirdposition with a mean of 42.65N. ProtempTM4 had a fairly 25.35VHN of surface harndness and is the second bestamongst all the four material concerned. Structur 3 showed little betterresult in wear resistance of .
0019% volumetric loss which is better thanProtempTM 4, whereas the results for stuructur 3 for factureresistance is 38N and surface hardness is 17VHN which holds the last postion inthis study analysis table. Self cure PMMA the widely used material fortemporisation and had been studied by various authpors. SuryaPrakash Sharma et al inthe year since 1940 PMMA is widely used temporary restoration material due tois good wear resistance, durability, good polish ability and esthetic; thoughsuccessful its use is gradually fading with the emergence of newer material asbis acryl resin with the easy mode of manipulation and better esthetics.36AnilK Gujjari et al in the year 2013also stated that bisacryl was prone to damage as its fracture resistance isless as the PMMA crown which has better fracture resistance. 2 Resin S acryY. I.
Osman et al in the year 1993studied that highest resistance is offered by PMMA crown than bisacryl resinand stated that PMMA material are expected to give better results is terms offracture resistance than other materials. 37 Inthis conducted study it has been observed that Self cure in wear resistance ofwear resistance is 0.0015% of total volumetric loss which makes it the 2ndbest, fracture resistance being 53.5N which bagged it the second position andfor surface harness it stood third with 21VHN. Recentadvanced technology that had been put into the field of dentistry is CAD/CAMmilling of Blocks made of biocompatible materials fabricated by industrialcontrol.
CAD/CAM milled PMMA also available for Interim Restoration purpose.Mohammad M. Rayyan et al in the year 2015 suggested that resin matrixcomposition affects the surface hardness, wear resistance and fractureresistance of the temporary materials. However he also stated that beingindustrially fabricated CAD/CAM PMMA exhibits better mechanical properties thanthose of manually fabricated temporary crowns. Hence CAD/CAM fabricatedtemporary crowns can be used in long term restorations. key1 Vanessa Alt et al in the year 2011had alsocommented that CAD/CAM fabricated prosthesis shows more mechanical strength thanof directly fabricated interim prosthesis even if same material is concerned.7 Again Isil Karaokutan et al in the year 2015 stated that CAD/CAM fabricatedtemporary crowns; the latest trend reduces the risk of failures and chair sidetime.
CAD/CAM fabricated temporary crowns shows higher fracture strength thanconventionally fabricated PMMA crowns. 8 Ronald D. Perry et al inthe year 2012 suggested that CAD/CAM fabricated temporary crown having betterphysical properties can sustain up-to a year in difficult cases too.
11Claudia Florina Andreescu et al in the year 2017stated that CAD/CAM fabricated temporary crowns are have good fracture strengthand fracture resistance so they tend not to fracture under load as CAD/CAMmaterials have almost zero porosity and homogenisity is very high so they havehigh resistance to fracture. 12 Marwa Eltayeb et al inthe year 2014 also said that CAD/CAM fabricated temporary crowns have higherfracture resistance and wear resistance than the conventionally fabricatedcrown. 23In thisconducted study it has been obtained that CAD/CAM fabricated PMMAtemporary crowns showed the best wear resistance amongst the other group of0.0081% 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 crownsare have less work time, cost-effective and quality control, hence are moresuitable for prolong treatment.
30 More over as per the outcome of theconducted study it can be said that the second best material to use astemporary restoration is PMMA made by conventional method. Z Vally et al in the year 2013 also said the same thing that this fractureresistance 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 crownsare more than that of bisacryl resin making PMMA the the second besttemporisation material. 34 Lately it must bekept in mind that as in-vitro studies are controlled study it isdifficult to co –relate with the inta-oral or clinical performance but aninference can be drawn about the best suitable material available that can beused as a interim restoration.