Why is MARC™ Needed?
 

Growing use of Resins

• The use of amalgam is decreasing and it is predominantly being replaced by resin-based composites. (Burke, McHugh et al. 2003; Burke, McHugh et al. 2004; Sunnegardh-Gronberg, van Dijken et al. 2009)
   
• The use of resin has grown to the point that 116 million resin fillings were placed in the US in 2005 and many believe that use of amalgam fillings will disappear within ten years. (ADA 2005; Christensen and Child 2010)

 
Emerging Concerns

• There is considerable variability in how restoring teeth with resin is taught. (Lynch, McConnell et al. 2006; Lynch, McConnell et al. 2006; Lynch, McConnell et al. 2006; Lynch, Shortall et al. 2007)
   
• Resin fillings are demonstrating inconsistent longevity, and are not lasting as long as amalgam, or as long as they should. (Hickel and Manhart 2001; Brunthaler, Konig et al. 2003; Van Nieuwenhuysen, D'Hoore et al. 2003; Bernardo, Luis et al. 2007; Mitchell, Koike et al. 2007; Opdam, Bronkhorst et al. 2007; Soncini, Maserejian et al. 2007; Kovarik 2009; Simecek, Diefenderfer et al. 2009; Sunnegardh-Gronberg, van Dijken et al. 2009; Christensen and Child 2010)
   
• There are indications of excessive variability in the amount of energy delivered, both between dentists and between different curing lights. (Price, McLeod, Felix 2010)
   
• There are real risks associated with over-curing resin. If too much energy is delivered to the tooth this may cause thermal damage to the pulp and oral tissues. (Bouillaguet, Caillot et al. 2005; Millen, Ormond et al. 2007; Bagis, Bagis et al. 2008; Durey, Santini et al. 2008; Guiraldo, Consani et al. 2008; Santini, Watterson et al. 2008; Baroudi, Silikas et al. 2009)
   
• Conversely, there are real risks associated with under-curing the resin which:

- adversely affects physical properties (Ferracane, Mitchem et al. 1997; Caldas, de Almeida et al. 2003; Vandewalle, Ferracane et al. 2004; Correr, Sinhoreti et al. 2005; Lohbauer, Rahiotis et al. 2005; Kim, Lee et al. 2006; Staudt, Krejci et al. 2006; Xu, Sandras et al. 2006)

- reduces bond strengths (Kim, Lee et al. 2006; Staudt, Krejci et al. 2006; Xu, Sandras et al. 2006)

- increases wear and breakdown at the margins (Ferracane, Mitchem et al. 1997; Vandewalle, Ferracane et al. 2004)

- decreases biocompatibility (de Souza Costa, Hebling et al. 2003; Franz, Konig et al. 2003; Uhl, Volpel et al. 2006; Sigusch, Volpel et al. 2007; Knezevic, Zeljezic et al. 2008; Brambilla, Gagliani et al. 2009)

NOTE: See European Union Health and Consumer Protection Scientific Committee Report on the "Safety of dental amalgam and alternative dental restoration materials".


Limitations of Current Resin Curing Practices

• Currently, dentists have no way of knowing when they have delivered enough energy to adequately cure the resin.
   
• Clinicians are unable to judge the depth of cure intra-orally. Scraping the resin at the top of the restoration gives little or no indication how well it is cured at the bottom.

Limitations of Laboratory-based Findings

• There are considerable differences between the laboratory and clinical settings. In laboratory tests, the curing light is held stationary at 90° in very close proximity to the resin. This does not happen clinically where the distance between the cusp tip and the base of the interproximal box can exceed 7 mm. (Yearn 1985; Price, Dérand et al. 2000; Froes-Salgado, Pfeifer et al. 2009) This distance will reduce the light intensity available for the photo-activation of the resin.(Felix and Price 2003; Corciolani, Vichi et al. 2008)
   
• The hardness or depth of cure is usually only measured at the center of the specimen. This gives little indication how well the entire specimen is cured. From this type of research publications have reported that a range of 6 to 36 J/cm2 is required to adequately cure a 2-mm thickness of dental resin. (Yap and Seneviratne 2001; Fan, Schumacher et al. 2002; Lovell, Newman et al. 2003; Calheiros, Kawano et al. 2006 ; Calheiros, Daronch et al. 2008; Schattenberg, Lichtenberg et al. 2008) This amount of energy is affected by the choice of resin and the curing light. Price et al. have developed a hardness mapping technique that measures the extent of cure over a larger area of the restoration and gives a better comparison of curing lights. (Price, Felix et al. 2006; Price, Fahey et al. 2010)

Limitations of Information Currently Available to Dentists

• Resin manufacturers and light manufacturers often do not give specific instructions on how much energy is required to adequately cure the resin to meet the manufacturers' specifications. Instead, dentists must rely on manufacturer “recommended curing times”, but many of these include “fine print” details, (e.g., shade, increment thickness, distance from light source to the resin, light output) the implications of which may not always be fully understood.
   
• Clinicians are unable to accurately judge the output of their curing light because the dental radiometers they use are inaccurate. (Leonard, Charlton et al. 1999; Roberts, Vandewalle et al. 2006; Dhaliwal, 2005) In addition, dental radiometers do not report the irradiance or energy received by the resin restoration: only the irradiance at the tip-end of the curing light. Consequently dentists have no way of knowing how much energy they are delivering to their restoration, or the resin which may be 6 - 8 mm from the tip-end.