Effects of Preheated Composite on Micro leakage-An in-vitro Study

Abstract

IntrOductIOnDirect composite restorations are gaining an increased popularity over the conventional amalgam restorations due to esthetic demands and concerns regarding mercury in amalgam [1]. The clinical success of the composite restorations is very much dependent on its polymerization and degree of conversion. Highly viscous composites are very hard to adapt accurately to cavity preparations and may leave behind unwanted voids, hence, more flowable composites with less filler content were introduced. There are many factors which affect the viscosity of resin.One of the greatest limitations of direct resin composite restoration is linked to its high polymerization shrinkage. During polymerization, it changes from a pre gel phase to a post gel phase. During the pregel stage, the reactive species can rearrange themselves without generating much internal and interfacial stresses to compensate for any volumetric shrinkage [2][3][4]. However, in the post gel stage the resin has partially set and can no longer undergo plastic deformation to compensate for any volumetric shrinkage. As a result, tensile stresses are generated at the resin tooth interface and causes pulling of the material away from the tooth surfaces [5,6]. C-factor, also known as configuration factor is the ratio of unbonded to bonded surface which affects the polymerization shrinkage of the restoration. During polymerization of resin composite, any volumetric shrinkage will be compensated by rearrangement or flow of the resin composite. Only free surfaces of a restoration are able to act as a reservoir for plastic deformation in the pre gel stage. Thus, if clinically the C-factor can be decreased, the polymerization shrinkage may be decreased as well.Composites with less viscous consistency were introduced because it increases adaptation and decreases micro-leakage along the restoration tooth interface. Many attempts have been made including incorporating flowable composites, fiber inserts, or chemical and laser treatments of dentin [7][8][9][10][11][12][13]. Chairside warming of composite resins before photopolymerisation is seen to reduce viscosity and increase flowability by increasing the degree of conversion. When temperature increases, both the radical and monomer mobility increases resulting in a more highly cross-linked polymer network [14]. With this increase in conversion, mechanical and physical properties of the resin are also increased. Also, preheated composites have a better surface hardness and greater depth of cure [15,16]. A study by Bortolotto and Krejci showed that when temperature was raised from 5°C to 40°C, there is a significant increase in the Vickers Hardness at a curing depth of 0.5mm [17]. AImThe aim of the study is to determine the effect of temperature on the degree of micro leakage in resin composite restorations. mAtErIALS And mEtHOdSThe study was conducted in Saveetha Dental College, Chennai, India and was approved by the Scientific Review Board Committee. A total of 60 extracted non carious premolars, previously stor...

Pre-Heating Effect on Monomer Elution and Degree of Conversion of Contemporary and Thermoviscous Bulk-Fill Resin-Based Dental Composites

“…Meanwhile, DC is influenced by several factors, such as light exposure conditions, composition, shade, opacity, and thickness of the RBC, pre-cure temperature also plays an important role in the polymerization process [ 5 , 6 ]. As the success of RBC restorations depends on their polymerization and DC, the influence of temperature has become one of the central issues of several studies [ 7 , 8 ].…”

“…As reported by several investigations, pre-heating may have a beneficial impact on marginal adaptation, gap formation, and microleakage by reducing the viscosity of RBCs [ 7 , 14 , 15 ]. Improved handling properties, such as flowability can facilitate the application of the filling material, consequently making the procedure less time-consuming.…”

Preheated composite: Innovative approach for aesthetic restoration

“…Nevertheless, studies have found that rise in pulpal temperature only by 0.8 • C after placement of a 60 • C preheated composite resin while an increase of 5 • C pulpal temperature is seen after 20s of light curing. 12 Daronch et al found that after removing composites from heating device, 50% of the temperature attained will be lost after 2 minutes and almost 90% will be lost after 5 minutes. • Light of dental unit chair can also be used clinically in order to warm composites.…”

Degree of Monomer conversion for different resinous materials used to lute ceramic laminate veneers (in vitro study)

“…Nevertheless, studies have found that pulp temperature is raised only by 0.8°C after placement of a 60°C preheated composite resin while 20s of light curing increases pulp temperature by 5°C. 10 The term "Degree of Conversion" (DC%), can be defined as the monomeric carbon-carbon double bonds conversion into polymeric carbon-carbon single bonds, the importance of increasing the conversion and thus increased crosslinkage results in improvement in properties as higher surface hardness, flexural strength, fracture toughness, and tensile strength. 11 Low degree of conversion can affect mechanical properties of the cement and results in increase in solubility, water sorption and subsequently affect its color stability 12 .…”