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LETTER TO EDITOR Table of Contents   
Year : 2009  |  Volume : 20  |  Issue : 4  |  Page : 516
Comment on 'standards on restoratives'


Department of Mechanical Engineering, Sri Venkateswara College of Engineering, Pennalur, Sri Perumbudur - 602 105, India

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Date of Web Publication29-Jan-2010
 

How to cite this article:
Padmanabhan K. Comment on 'standards on restoratives'. Indian J Dent Res 2009;20:516

How to cite this URL:
Padmanabhan K. Comment on 'standards on restoratives'. Indian J Dent Res [serial online] 2009 [cited 2014 Jul 30];20:516. Available from: http://www.ijdr.in/text.asp?2009/20/4/516/59429
Sir,

I am writing this letter after going through dozens of research articles written and published on the issue of distilled water conditioning and artificial saliva conditioning of dental restoratives containing polymers (at least as a binder). Many important mechanical properties are evaluated after the so called conditioning, like wear, fracture toughness, tensile strength, compressive strength, stiffness and physico-chemical properties to disqualify restoratives, which do not conform to prescriptions and expectations.

In my opinion, some of the investigators neither understand the importance of distilled water conditioning and artificial saliva conditioning nor are they knowledgeable about the implications and correctness of the property evaluations which follow. Polymers take several days to reach a steady state of equilibrium in water or saliva absorption. Any measurement of the qualifying mechanical properties will only be transient if these restoratives are conditioned for a pre-determined duration of just 24 hours or 72 hours and evaluated. [1],[2],[3],[4],[5]

The aspect of water or saliva conditioning should be more clearly understood and transient conditioning followed by testing should not be considered as the numero uno criteria in the design of standard methods for these restoratives, veneers and crowns. The point is that many of these 'transient' investigations are not followed up with research and publications on steady state conditioning and the implications on testing for qualification. Though it cannot be denied that a quick conditioning followed by mechanical testing provides some transient details, they cannot be relied upon for veracity on long term mechanical behaviour. Thus, it becomes important to follow up these investigations with those on long term conditioning.

It is disturbing to note that even publications emerging from NIST (USA) grants, NIDCR (USA) grants and those based on ADA (USA) guidelines ignore the issue of long term characterization with respect to saliva and distilled water conditioning. [6],[7],[8] In one investigation the researchers have used distilled water to identify tribochemical reactions in a restorative that was conditioned for less than 72 hours. [5] As ionomers are present in the restoratives, deionized water should have been used in a closed environment and conditioning carried out to saturation before looking for tribochemical reactions. The results of such transient investigations, thus, cannot be of any significance. Some of these reports even claim that typical oral conditions were maintained even though only transient conditions were maintained during the investigation. The publication list presented here forms only the tip of the iceberg.

Reports of investigations which clearly spell out the implications of steady state conditioning, i.e. post saturation, must gain priority in the design of standard methods for qualification of polymer containing restorative materials and ceramics/glasses which are known to react with water and saliva. Further, according to ISO 7405 guidelines, the restoratives must demonstrate biocompatibility, which can be correctly assessed only upon long term conditioning replicating the oral environment.

 
   References Top

1.Ferracane JL, Mitchem JC. Properties of posterior composite: results of round robin testing for a specification. Dent Mater 1994;10:92-9.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]  
2.Paul SJ, Leach M, Rueggeberg FA, Pashley DH. Effect of water content on the physical properties of model dentine primer and bonding resins. J Dent 1999;27:209-14.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]  
3.Vijayaraghavan TV, Hsiao J. Flexural behavior of visible light-cured composites as a function of temperature under water immersion test conditions. Dent Mater 1994;10:347-52.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]  
4.Kawai K, Leinfelder KF. In vitro evaluation of OCA wear resistance of posterior composites. Dent Mater 1995;11:246-51.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]  
5.Nagarajan VS, Hockey J, Thompson VP, Jahanmir S. Wear mechanisms of a dental composite with high filler content. J Mat Sci 2000;35:487-96.  Back to cited text no. 5      
6.Attota R, Jahanmir S. Effect of interfacial layers on wear behaviour of a dental glass ceramic. J Am Ceramic Soc 2004;83:1831-3.  Back to cited text no. 6      
7.Nagarajan VS, Jahanmir S, Thompson VP. In vitro contact wear of dental composites. Dent Mater 2004;20:63-71.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]  
8.Nagarajan VS, Jahanmir S. The relationship between microstructure and wear of mica containing glass-ceramics. Wear 1996;200:176-85.  Back to cited text no. 8      

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Correspondence Address:
K Padmanabhan
Department of Mechanical Engineering, Sri Venkateswara College of Engineering, Pennalur, Sri Perumbudur - 602 105
India
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DOI: 10.4103/0970-9290.59429

PMID: 20139587

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