Year : 2005 | Volume
: 8 | Issue : 1 | Page : 52--59
Microleakage in posterior resin composite restoration using different filling, curing and polishing techniques
S Senthil Kumar, Yohan Chacko, L Lakshminarayanan
Department of Conservative Dentistry and Endodontics, Saveetha Dental College and Hospitals, Chennai., India
S Senthil Kumar
Department of Conservative Dentistry and Endodontics, Saveetha Dental College and Hospitals, Chennai.
Composite resins are the most commonly used direct esthetic restorative material. Despite improvement in material properties and restorative techniques a cavity with its margins in dentin/cementum presents many difficulties. Clinical problems like post operative sensitivity and marginal discoloration occur due to microleakage. This in vitro study compares the effect of different techniques of filling, curing, finishing and polishing on reducing microleakage in posterior resin composite restorations.
|How to cite this article:|
Senthil Kumar S, Chacko Y, Lakshminarayanan L. Microleakage in posterior resin composite restoration using different filling, curing and polishing techniques.J Conserv Dent 2005;8:52-59
|How to cite this URL:|
Senthil Kumar S, Chacko Y, Lakshminarayanan L. Microleakage in posterior resin composite restoration using different filling, curing and polishing techniques. J Conserv Dent [serial online] 2005 [cited 2020 Mar 29 ];8:52-59
Available from: http://www.jcd.org.in/text.asp?2005/8/1/52/42703
Dental resin composite is the most frequently used direct tooth colored restorative material.  Mechanical performances, wear resistance and esthetic potential have been significantly increased over the past few years which has permitted their use in posterior teeth with greater reliability. ,
However, polymerization shrinkage still presents certain limitations.  Resulting stresses may lead to clinical problems like marginal discoloration, restoration and /or tooth fractures, solubility of the bonding system and microleakage.
Adhesive bond strength, restorative materials' modulus of elasticity, cavity design, light intensity and curing time are some of the factors that influence the marginal quality of composite restorations. , Some of the techniques proposed to counteract shrinkage and enhance marginal adaptation include - the incremental filling technique, the soft-start mode of polymerization and certain finishing and polishing techniques.
This invitro study evaluated the effect of two light curing modes, two filling techniques and two polishing techniques on microleakage of posterior composite restorations.
MateriaIs and Methods
38 sound mandibular first molars were cleaned, polished and examined under magnification (5X). Teeth with surface cracks, previous restorations, calculus and anatomical abnormalities were excluded. The teeth were stored in distilled water until the restorative procedure.
Class V cavities (3 x 3 x 3mm approximately) with one wall on the enamel and one wall on the root dentin/cementum were prepared at the cervical thirds on both buccal and lingual surfaces using a straight fissure bur rotating in a water cooled high speed turbine. A new bur (MANI, INC. JAPAN) was used for every 5 preparations.
One tooth completely coated with nail varnish served as negative control. One tooth with a prepared class V cavity and not restored served as positive control.
The remaining 36 teeth were randomly divided into two groups of 18 teeth each and were designated as L 1 and L 2.
Restorations in group L 1 were polymerized using a conventional curing unit - Astralis 3 (IVOCLAR VIVADENT -Liechtenstein) (500mW/ cm 2 /40 seconds).Restorations in group L 2 , were polymerized using a soft start polymerization unit Spectrum 800 (Dentsply - Milford, DE, USA) (300mW/ cm-/20 seconds + 500mW/cm 2 /20 seconds).
The 18 teeth designated as L 1 , and 18 teeth designated as L 2 , were further sub grouped as I 1 ,B 1 and I 2 ,B 2 , respectively with 9 teeth in each group.
9 teeth of each subgroup I,, I, were filled in three increments (pulpal-cavo surface) of 1.5 mm (first two increments) and 1.0mm (last increment).9 teeth of each sub group B 1 ,B 2 , were filled in one (bulk) increment of 4mm.
Each of the subgroups I 1 ,I 2 ,B 1 , B 2 , with 9 teeth each were further divided into F 1, F 2, F 3 , groups with three teeth (six cavities) in each group. Finishing and polishing was done after storing all polymerized restorations in distilled water at room temperature for 24hrs.
Group F 1 , were cured against a mylar matrix. (Unident, India)Group F 2 , were finished and polished using impregnated cups (ASTROPOL - IVOCLAR VIVADENT-Liechtenstein) for 10 seconds for each tooth.Group F 3 , were finished using SOF-LEX disks (3M Dental Products, St. Paul, MN 55144).
Each preparation was acid etched with 35% phosphoric acid GLUMA ETCH (HEREAUS KULZER, DORMAGEN) for 15 seconds. The cavities were rinsed for 15 seconds and gently blot dried for 10 seconds. GLUMA COMFORT BOND (HEREAUS KULZER, GmbH & Co., KG, Hanau) was applied and cured according to manufacturers instructions. Posterior resin composite SOLITAIRE 2 (HEREAUS KULZER, DORMAGEN) was used to fill the cavities. Filling, curing and polishing was done according to the specifications of each group and subgroup.
All the surfaces of the teeth were coated with two layers of colored nail varnish leaving a 2mm window around the tooth - restoration interface. The teeth were then immersed in 2% methylene blue solution for 24hours at room temperature. They were then rinsed in tap water, and sectioned with diamond disk longitudinally and leakage evaluated at two areas on each specimen using an intraoral camera and measuring software (Schick Technologies). The data was tabulated and statistical analyses (Mann-Whitney - U - test, Kruskal Wallis test and one-way ANOVA) were performed to test the significance of the mean values obtained.
The negative control did not show any leakage while the positive control showed maximum leakage on both walls thus validating the study protocol.
It was found from the results that there was higher leakage scores in dentin margins than enamel margins [Table 1].
Comparison between different combinations of light curing and filling techniques within each method of finishing showed significantly lower leakage at enamel margins when restorations were finished with mylar matrix, filled in bulk and cured using conventional light source. However, no other combinations were statistically significant.[Table 4],[Table 5] Comparison between the filling techniques showed significantly higher leakage at enamel margins with the incremental filling technique. [Table 6]
When light curing modes were compared significantly lower leakage means were noted when conventional light source was used for curing.[Table 7]
Comparison between different methods of finishing showed no significant differences in either enamel or dentin margins.[Table 2],[Table 3]
In today's restorative dentistry, composite resins play a major role. The use of composites has many advantages namely; esthetics, low thermal conductivity and preservation of tooth structure. Among other factors, the longevity of composite restoration is directly related to the quality of marginal adaptation. Marginal adaptation is influenced by various factors like cavity preparation, restorative material, restorative procedure, finishing procedure .
Polymerization shrinkage remains the single most important factor in achieving a better marginal seal.
Various methods have been proposed for reducing polymerization shrinkage and enhancing marginal adaptation. This includes the incremental placement technique based on the C-factor concept. The theory is that increments of resin layered on each other will distribute the polymerization shrinkage throughout the layers, reduce the C-factor and allow the composite to contract freely to the adhesive surface.
Controlling the polymerization process by various curing methods include the recently introduce soft-start mode of curing. The aim of this technique is to prolong the time prior to reaching the gel point by using low light curing intensities and increasing the flow capability of the material. Subsequently high intensities are necessary for complete polymerization. 
Variation in finishing and polishing techniques has been shown to affect the ability of restorative materials to resist leakage. 
It was found from the results that there was higher leakage in dentin margins than enamel margins in agreement with the literature. Dentin is less mineralized and contains more moisture which makes it a less favourable bonding substrate. ,,
The difference in plasticity of the densely filled posterior resin composite (Solitaire - 2) would have made close adaptation less consistent. The interlocking particle technology inherent in these materials would have decreased the capacity for these composites in helping to compensate for shrinkage stresses.
Greater volume of composite in the bulk filling technique would obviously produce larger stresses when they undergo volumetric shrinkage due to polymerization.  While greater enamel bond strengths would have tolerated the shrinkage stresses, the weaker dentin/cementum bond strengths did not.
Higher leakage in the incremental filling technique can be attributed to factors like incorporation of voids, bonding failure between increments and possible contamination between increments. Also, the C-factor for the last increment was approximately 6.
The results of the present study speculate that the initial lower intensity may not have activated sufficient number of initiator molecules for an adequate polymerization reaction. Therefore the final cure of the nearly unpolymerized material may have corresponded to an immediate full intensity curing. The beneficial effect of low intensity curing may therefore be nullified by the high intensity final cure.
The results of this study did not show any significant differences between the methods of finishing. The overhangs created by mylar matrix, heat generated locally resulting in plastic deformation in the restorative material when using dry disk polishing and deeper scratches at the tooth restoration interface produced by diamond impregnated rubber cups could have resulted in higher leakage scores.
Considering all these factors a resin composite demonstrating lower polymerization shrinkage and restorative technique that minimizes or eliminates microleakage could clinically be preferred.
Within the limitations of this study it can be concluded that:
None of the techniques evaluated could successfully eliminate microleakage at the tooth restoration margin.Enamel margins proved to be less prone to microleakage.Better enamel margins were obtained when the restorations were filled in bulk, cured with conventional light source against a mylar matrix.[Figure 1],[Figure 2]
|1||Applequist EA & Meiers JC : Effect of bulk insertion, pre-polymerized resin composite balls, and beta-quartz inserts on microleakage of Class V resin composite restoration. Operative Dentistry, 1996 . 27(4) : 253-258.|
|2|| Coli P & Brannstrom M : The marginal adaptation of four different bonding agents in Class 11 composite resin restorations applied in bulk or two increments. Quintessence International, 1993 ; 24(8) 583 - 591.|
|3|| Derhami et al : Microleakage in Class II composite resin restorations. Operative Dentistry, 1995 ; 20: 100 - 105.|
|4|| Eick JD & Others : Current concepts on adhesion to dentin. Critical reviews of oral biology and medicine, 2000 ; 8(3) 306 - 335.|
|5|| Friedl KH, Schmalz G, Hiller KA & Markl A : Marginal adaptation of Class V restorations with and without soft-start polymerization. Operative Dentistry, 2000 ; 25 (1) : 26-32.|
|6|| Lambrechts P, Braem M & Vanherle G Evaluation of clinical performance for posterior composite resins and dentin adhesives. Operative Dentistry, 1987 ; 12 (2) : 53 - 78.|
|7|| Leinfelder KF, Bayne SC & Swift EJ Jr Packable composites : Overview and technical considerations. Journal of Esthetic Dentistry, 1999 11(5):234-249.|
|8|| Manhart J, Kunzelmann K-H, Chen HY & Hickel R : Mechanical properties and wear behavior of light-cured packable composite resins. Dental Materials, 2000 ; 16(1) : 33-40.|
|9|| RC Carvalho& JC Pereira A review of polymerization contraction : the influence of stress development versus stress relief. Operative Dentistry, 1996 : 21 : 17 - 24.|
|10|| Roulet JF : Benefits and disadvantages of tooth colored alternatives to amalgam. Journal of Dentistry, 25 : 459 - 473.|
|11|| Taylor M.J & Lynch : Marginal adaptation. Journal of Dentistry, 21, 265.|
|12|| Unterbrink GL & Muessner R: Influence of light intensity on two restorative systems. Journal of Dentistry, 1995;23(30):l83-189.|