FDI Worldental Daily

Science & Practice Wednesday, 28 August 2013 D uring the past decades, restorative treatments in den- tistry have changed remark- ably. Growing interest in aesthetic restorations in the posterior region and the alleged adverse health ef- fects and environmental concerns re- garding the release of mercury gave rise to controversial discussions about the use of amalgam in several countries.Alongwiththeintroduction of new and improved resin materials that offered adhesive properties and the principle of minimal invasive in- terventions, this has led to a change from the use of amalgam towards the use of composite resins in posterior teeth. Restoring a Class II preparation with composite resin can be challeng- ing. Open contacts, poor anatomical contour, and an inadequate marginal sealarejustsomeoftheproblemsthat clinicians have to deal with. Initially, theseissuescanbelinkedinparttothe useofamalgammatrixsystems. The ideal matrix system creates a tight interproximal, anatomically cor- rect contact with minimal flash and a seamless marginal seal. It has been shown that composite resin provides little internal force to counteract the forcefromthematrix.Therefore,unlike amalgam,whichhasaveryhighresist- ance to deformation, composites are easily forced back into their original position by a tight circumferential ma- trix band, thus resulting in open con- tacts.Thisproblemistheresultofsev- eral factors, including that composite cannot be condensed like amalgam, which leads to an insufficient adapta- tionofthematrixtowardstheadjacent tooth,thepolymerisationshrinkageof the composite material, and the ef- fects on tooth position owing to the elasticbehaviouroftherubberdam. Proximal contact plays an impor- tant role in the stomatognathic sys- tem. Inadequate contact may result in impactedfoodandleadtoperiodontal disease and tooth movement. Re- searchers have sought to overcome these problems by improving material characteristics and application tech- niques. The choice of matrix systems and separation techniques is an im- portant factor. In order to improve the proximal contacts, instruments were designed to allow the tightening of contact during curing. Other tech- niques advocated the use of cured composite or ceramic inserts that would provide predictable contacts and proper physiological contour. Heavy-bodied composites were intro- duced in an attempt to mimic the han- dling characteristics of amalgam and createmorefavourablecontacts.How- ever, researchers have demonstrated thatitisthematrixsystemandnotthe handling characteristics of the com- posite that determines a favourable contact. Composite resin is a tech- nique-sensitive material that requires itsownuniquematrixsystem. In response to these frustrating clinical problems, the sectional matrix and contact ring matrix retainer were developed, providing significant im- provements to previous devices. In modern dentistry, traditional circum- ferential matrix systems are very pop- ular, but they have shortcomings with regard to their improper proximal ma- trix form and establishing tight proxi- mal contacts. The circumferential matrix systems showed significantly looser proximal contacts in studies on Class II cavities, which might be ex- plained by the thickness of the matrix when placing a two-surface restora- tion.Inrecentinvitroandinvivostud- ies,sectionalmatrixsystemsincombi- nation with separation rings were proved to generate proximal contacts withareliabletightnessintwo-surface Class II cavities.The use of a sectional matrix system for restoring two-sur- faceClassIIcavitiesresultedinsignifi- cantly tighter proximal contacts than the use of the circumferential matrix systemsdid. Prof. Dilek Tağtekin is a researcher in the Department of Restorative Den- tistry at Marmara University’s Faculty ofDentistryinIstanbul.Today,shewill be presenting a paper titled “Reasons for failure of approximal restorations andnewmatrixsystems”duringoneof thethemorningsessionsaspartofthe 2013FDIAWDCscientificprogramme. It’s all about the matrix ByProf.DilekTağtekin,Turkey 10 www.fdiworldental.org AD IProf.DilekTağtekin,Turkey