ORIGINAL ARTICLE
Microleakage evaluation in restorations using different
resin composite insertion techniques and liners
in preparations with high c-factor – An in vitro study
Mirza Mubashir Baig, Mohammed Mustafa
*
, Zaid A. Al Jeaidi,
Mohammed Al-Muhaiza
Dept. of Conservative Dental Sciences, College of Dentistry, Salman Bin Abdulaziz University, Al-Kharj, Saudi Arabia Received 14 December 2012; revised 1 March 2013; accepted 19 March 2013
Available online 14 May 2013
KEYWORDS Microleakage; Resin composite; Insertion techniques; Liners; C factor; Enamel; Cementum
Abstract Objective: To evaluate microleakage in the enamel and cementum walls in preparations with high C factor, using three resin composite insertion techniques and two liners.
Materials & methods: Standard class V cavities were prepared in buccal and lingual aspects of 36 caries free, extracted premolars. The teeth were randomly assigned to three groups of 12 each cor-responding to three different insertion techniques (1) Oblique insertion (2) Horizontal insertion and (3) Bulk insertion and then subdivided into three groups of four each depending on the type of liner used (1) no liner (2) RMGIC liner (GC fuji II LC) and (3) Flowable composite liner (Tetric flow, Ivoclar vivadent). The preparations were etched and restored with an Adhesive (adper single bond 2 3M ESPE), Liner (except for the no liner group) and Microhybrid resin composite (Z100, 3M ESPE). Specimens were isolated with nail varnish except for 2 mm wide rim around the restoration, thermocycled (1000 thermal cycles, 5/55C, 30 s dwell time) and then immersed in an aqueous solu-tion of 50 wt% silver nitrate for 24 h followed by 8 h in a photo developing solusolu-tion and evaluated for microleakage using a stereomicroscope on an ordinal scale of 0–4. The microleakage scores were analyzed by using the chi square test.
Results: Oblique incremental technique coupled with the use of flowable composite liner gave bet-ter results when compared to other groups at the cementum margins.
* Corresponding author. Address: College of Dentistry, PO. Box 153, Al-Kharj 11942, Saudi Arabia. Tel.: +966 532919142; fax: +966 015886240.
E-mail address:ma.mustafa@sau.edu.sa(M. Mustafa). Peer review under responsibility of King Saud University.
Production and hosting by Elsevier
King Saud University
King Saud University Journal of Dental Sciences
www.ksu.edu.sa
www.sciencedirect.com
2210-8157ª2013 Production and hosting by Elsevier B.V. on behalf of King Saud University.
http://dx.doi.org/10.1016/j.ksujds.2013.03.002
Conclusion: None of the insertion techniques nor the use of liners were able to eliminate microleak-age completely; however the use of the oblique insertion technique coupled with the use of flowable composite liner gave better results.
ª2013 Production and hosting by Elsevier B.V. on behalf of King Saud University.
1. Introduction
Although resin composites are the most commonly used di-rect tooth colored restorative material, polymerization shrinkage still continues to be a problem.1–3 This can result in impaired marginal seal providing access to bacteria, oral fluids, molecules and ions at the preparation walls/restor-ative material interface.4,5 This in turn leads to staining at the margins of the restorations, a hastening of the break-down at the margins of the restoration, recurrent caries at the tooth preparation walls and restorative material inter-face, hypersensitivity of the restored teeth and development of pulpal pathology6 all of which endanger the longevity of the restoration.7
Numerous studies support the contention that many of the irritant properties, previously associated with chemical action of filling materials are themselves infact related to bacterial leakage.6,8–10 Although little or no clinical evidence sustains the hypothesis that composite materials with greater polymer-ization shrinkage have poorer clinical performance, laboratory data from several studies support this belief.1,3,11,12
The factors ascribed to marginal microleakage are the adhesive bond strengths to different dental substrates4,13,14 which in turn depend on the histological and morphological characteristics of the enamel, dentin/cementum,15 residual stress created by resin composite shrinkage,16,17 differences among enamel/dentin and restorative materials coefficient of thermal expansion, polymerization source variables, cavity location and C-factor, resin composite insertion techniques all of which aggravate several clinical variables.18
In 1987, Feilzer et al. postulated that the geometric config-uration of the cavity plays an important role in the adaptation of resin composite restorations.19Since then several techniques have been suggested to improve marginal adaptation of high C factor preparations that potentially resists composite shrink-age2,16,17,20,21 like soft curing,1,3,11,12,22 incremental tech-nique,11,19,24 sandwich technique,25,26 use of an intermediate low modulus liner,12,29–31 different cavity preparations,27–30 use of beta-quartz glass ceramic inserts,32use of pre-polymer-ized composites inserts,32 use of self-cure resin as the first increment33 using the protocols for photo-polymerization34 increasing the filler content, increasing the molecular weight per reactive group and use of ring opening monomers.1,35
Considering the resin composite placement methods, some studies have shown that the incremental technique especially the oblique technique tends to improve marginal adaptation by resisting resin composite shrinkage stress.23,29On the con-trary other reports demonstrated that the bulk placement of composite induces less contraction stress, minimizing marginal leakage.36 The use of an intermediate low modulus liner be-tween the margins of tooth preparation and restoration has been advocated by some to provide a homogenous distribution of stress over the adhesive interface.
The objectives of this study were to evaluate microleakage in the enamel and cementum margins in high C factor prepa-rations when resin composite is placed by three different inser-tion techniques and also to judge the effects of liners on microleakage.
2. Materials and methods
Thirty-six caries free premolars were selected after examina-tion under a stereomicroscope at 10·magnification to detect any enamel cracks or fissures, which could cause errors during microleakage evaluation. The teeth were then stored in an aqueous solution of 0.5% Chloramine at 4C.
Standard high C factor class V cavities were prepared both on the buccal and lingual surfaces of each of the 36 teeth, for a total of 72 cavities. The gingival cavosurface margin of the preparation was deliberately kept below the cementoenamel junction. The preparations were made with a No. 245 carbide bur (SS White) in a high speed standardized handpiece under copious water coolant. After every five preparations the bur was discarded and replaced with a new one.
The final preparation had the following extensions: 3.0 mm Occlusogingivally, 3.0 mm Mesiodistally and 1.5 mm deep. The preparations were re-evaluated at 10·magnification to en-sure the absence of pulp expoen-sure and enamel cracks at the cavosurface margins.
These 36 teeth were then randomly divided into three groups of 12 each corresponding to three different insertion techniques Bulk, Horizontal and Oblique and then further di-vided into three subgroups of four each depending on the type of Liner used (No liner, Resin modified glass ionomer cement (RMGIC) liner and Flowable composite liner).
The preparations were etched with 35% phosphoric acid (Scotch bond Etchant, 3 M ESPE) for 15 s, rinsed with water for 15 s and blot dried, leaving the dentin moist and shiny. An ethanol and water based adhesive system (ADPER single bond 2, 3M ESPE) was applied in two consecutive coats to the entire preparation according to the manufacturer’s instructions, gently air dried to dispense the solvent and light cured for 20 s (LED Gnatus). All the experimental groups were restored with a microhybrid resin composite (Z100, 3M ESPE) shade A2. Each increment in all experimental groups was light cured for 40 s at a curing distance of 0.5 mm and light intensity of 550 mw/cm2, which was con-stantly monitored.
Group I (Bulk technique): Bulk insertion technique group (n= 12). This group was further sub divided into three sub-groups of four each according to the type of liner/no liner used:
- Sub-group A:No liner used (n= 4), teeth in this group were restored with microhybrid resin composite (single increment).
-Sub-group B: RMGIC liner (n= 4) was used and then restored in a similar manner as mentioned above.
-Sub-group C: flowable composite liner (n= 4) was used and then restored in a similar manner as mentioned above.
Group II (Horizontal technique):Horizontal insertion tech-nique group (n= 12). This group was further sub divided into
three sub-groups of four each according to the type of liner/no liner used:
-Sub-group A:no liner used (n= 4), teeth were restored with microhybrid resin composite using three horizontal incre-ments of 1 mm height each placed from the gingival toward the occlusal wall. The first layer was horizontally placed at the preparations in the gingival third. The second layer was Figure 1 Dye penetration scores.
Figure 2 Stereomicroscopic figures: group I (bulk insertion technique). Sub-group A, No liner.
Figure 3 Stereomicroscopic figures: group I (bulk insertion technique). Sub-group B, RMGIC.
Figure 5 Stereomicroscopic figures: group II (horizontal inser-tion technique). Sub-group A, no liner.
Figure 4 Stereomicroscopic figures: group I (bulk insertion technique). Sub-group C, flowable.
subsequently applied at the preparations in the middle third and the last increment at the preparations in the occlusal one third.
-Sub-group B: RMGIC liner (n= 4) was used and then restored in a similar manner as mentioned above.
- Sub-group C: Flowable composite liner (n= 4) was used and then restored in a similar manner as mentioned above.
Group III (Oblique technique):Oblique insertion technique group (n= 12). This group was further sub divided into three sub-groups of four each according to the type of liner/no liner used:
- Sub-group A: No liner (n= 4), these teeth are restored using an oblique layering technique in three increments. The first oblique increment was applied to contact the gin-gival, axial and distal walls. After the first increment was cured, the second oblique increment was inserted to contact the occlusal, axial and mesial walls and then light cured. A third increment was applied to cover the other increments, sealing the cavosurface margins and was subsequently light cured.
- Sub-group B:(n= 4), these teeth are lined with resin mod-ified glass ionomer cement according to the manufacturer’s instructions, light cured and then restored in a similar man-ner as mentioned above.
Figure 6 Stereomicroscopic figures: group II (horizontal inser-tion technique). Sub-group B, RMGIC.
Figure 7 Stereomicroscopic figures: group II (horizontal inser-tion technique). Sub-group C, flowable.
Figure 8 Stereomicroscopic figures: group III (Oblique insertion technique). Sub-group A, no liner.
Figure 9 Stereomicroscopic figures: group III (oblique insertion technique). Sub-group B, RMGIC.
Figure 10 Stereomicroscopic figures: group III (oblique inser-tion technique). Sub-group C, flowable.
-Sub-group C: (n= 4), these teeth are lined with flowable composite liner, and then light cured and restored in a sim-ilar manner as mentioned above.
The restored specimens were stored in distilled water at 37C for 24 h. The restorations were then finished and pol-ished with aluminum oxide disks (Sof-Lex Pop On, 3M ESPE). The teeth were coated with two layers of nail varnish, except for a 2.0 mm rim around the restoration, to allow the contact of the tracing agent with the margin of the restora-tion. The specimens were thermocycled for 1000 cycles at 5 ± 1 and 55 ± 1C with 30 s of dwell time. The specimens were immediately immersed in 50% silver nitrate solution for 24 h, followed by 8 h in a photo developing solution to allow the reduction of silver ions to metallic silver grains. The nail varnish was removed and the specimens sectioned through the center of the restoration with a precision, water cooled slow speed diamond saw (Cir-Saw, Confident Dental Co., India).
Then the restorations were analyzed with a stereomicro-scope at 30·magnification and scored for degree of dye pene-tration along the occlusal and gingival walls by two examiners: Scores: (Fig. 1).
0 =no microleakage.
1 =silver nitrate penetrates up to the dentino-enamel junc-tion (DEJ) or correspondent length at the dentin wall.
2 =silver nitrate penetrates beyond the DEJ or correspon-dent length at the correspon-dentin wall, surpassing half the cavity depth.
3= silver nitrate penetrates beyond half the cavity depth, without reaching the axial wall.
4 =silver nitrate penetrates along the axial walls.
3. Results
When composite restoration was tested for microleakage by using all the three different insertion techniques and without the use of any intermediate liners the dye penetration was significantly higher, as seen in sample Fig. 2, Fig. 5 and Fig. 8.
When RMGIC was used as a liner there was no significant difference in bulk and horizontal insertion tech-niques as seen in sample Fig. 3 and Fig. 6, whereas there was a significant reduction in microleakage when restored using the oblique insertion technique as seen in sample Fig. 9. When Flowable composite was used as a liner there was a statistically significant difference in all the three differ-ent insertion techniques as seen in sampleFig. 4,Fig. 7and Fig. 10.
None of the techniques for composite insertion nor the use of liners were able to eliminate microleakage completely at both the enamel and cementum margins. The lower value at enamel margins was expected as the enamel is a much eas-ier substrate to bond. There was no statistically significant difference at the enamel margins irrespective of the type of insertion technique used or with the use of intermediate liners.
At the cementum margins the oblique insertion technique gave the best results which are statistically significant when
compared to other insertion techniques with no liner group. The use of an intermediate flowable composite liner reduced the dye penetration even further when it was coupled with the oblique insertion technique.
3.1. Statistical analysis
The data were submitted for thechi square test (p< 0.5)to compare the difference in microleakage scores among different resin composite insertion techniques with and without the use of liners.
Enamel – No liner.
Groups
Bulk Horizontal Oblique Total 0.00 Count 2 2 0 4 % 25.0 25.0 00.0 16.7 1.00 Count 5 4 8 17 % 62.5 50.0 100.0 70.8 2.00 Count 1 2 0 3 % 12.5 25.0 00.0 12.5 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 5.529,p= .237 (not significant). Enamel – RMGIC. Groups
Bulk Horizontal Oblique Total 0.00 Count 3 4 0 7 % 37.5 50.0 00.0 29.2 1.00 Count 5 3 8 16 % 62.5 37.5 100.0 66.7 2.00 Count 0 1 0 1 % 00.0 12.5 00.0 4.2 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 8.089,p= .088 (not significant). Enamel – Flowable. Groups
Bulk Horizontal Oblique Total 0.00 Count 2 2 4 8 % 25.0 25.0 50.0 33.3 1.00 Count 5 5 4 14 % 62.5 62.5 50.0 58.3 2.00 Count 1 1 0 2 % 12.5 12.5 00.0 8.3 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 2.143,p= 0.71 (not significant).
Note. There were no statistically significant differences seen at the enamel margins irrespective of the type of insertion technique used or with the use of intermediate liners.
Cementum – No liner.
Groups
Bulk Horizontal Oblique Total 0.00 Count 0 0 3 3 % 00.0 00.0 37.5 12.5 1.00 Count 1 3 4 8 % 12.5 37.5 50.0 33.3 2.00 Count 2 0 1 3 % 25.0 00.0 12.5 12.5 3.00 Count 4 3 0 7 % 50.0 37.5 00.0 29.2 4.00 Count 1 2 0 3 % 12.5 25.0 00.0 12.5 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 15.565,p= .05 (significant). Cementum – RMGIC. Groups
Bulk Horizontal Oblique Total 0.00 Count 2 2 0 4 % 25.0 25.0 00.0 16.7 1.00 Count 5 4 4 13 % 65.0 50.0 50.0 54.2 2.00 Count 1 2 2 5 % 12.5 25.0 25.0 20.8 3.00 Count 0 0 2 2 % 00.0 00.0 25.0 8.3 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 6.554,p= .364 (not significant). Cementum – Flowable. Groups
Bulk Horizontal Oblique Total 0.00 Count 0 0 6 6 % 00.0 00.0 75.0 25.0 1.00 Count 4 3 2 9 % 50.0 37.5 25.0 37.5 2.00 Count 3 3 0 6 % 37.5 37.5 00.0 25.0 3.00 Count 1 2 0 3 % 12.5 25.0 00.0 12.5 Total count 8 8 8 24 % 100.0 100.0 100.0 100.0 X2 = 17.667,p= .007 (highly significant).
Note: statistically significant difference was seen when the oblique insertion technique was used, and there was a highly significant difference seen with use of flowable composite liner.
4. Discussion
It has been known for many years that conventional restor-ative materials and techniques produce dental restorations that
do not provide a complete marginal seal and numerous studies have demonstrated that leakage of fluid will occur between the filling and the prepared tooth surface.6,37Marginal void for-mations are leading causes of failure in resin based restoration The longevity of resin based composite restorations is compro-mised when bonding between the resin and the interior cavity walls fails to prevent marginal microleakage.38
To ensure outstanding marginal adaptation of an adhesive restoration some restorative aspects must be considered such as preparation design39–42composite shrinkage36,43,44and den-tal adhesive bonding strengths.39Restoring a box-shaped prep-aration with incremental placement of resin composite has been suggested based on the concept of reducing the volume of resin to be photopolymerized.16,19,20,23,29 This incremental technique improves certain aspects such as density, adaptation, thoroughness of cure and hardness of the composite.24,45
It has been suggested that if all composite increments were perfectly standardized, the horizontal technique would possi-bly show less microleakage.46However perfectly standardized increments are unachievable clinically. Studies have shown that the incremental technique especially the oblique technique tends to improve marginal adaptation by resisting resin com-posite shrinkage stress.23,29 On the other hand few authors advocate the bulk increment as a safe restorative technique be-cause it fills the total volume of the preparation and creates less residual shrinkage stress than the incremental technique.36,43,44 But as this concept is based on the elastic deformation of the restorative material flowing toward the free surfaces, more residual stresses should be expected.36
The results of this study when comparing different insertion techniques are in accordance with the study conducted by Hansen et al.23and Lutz et al.29which indicates that the obli-que insertion techniobli-que shows less microleakage at the cemen-tum margins which is statistically significant. At the enamel margins the results were not statistically significant which was expected as enamel is a better substrate to bond when compared to cementum.
To eliminate or to reduce the shrinkage stress or to make the adhesive bond resistant to its damaging effects several investigators proposed that a more flexible intermediate liner between the dentin and the resin composite will preserve the dentin bond during the polymerization process. This is com-monly referred to as Elastic bonding or the Elastic wall con-cept. A low viscosity material has been suggested as a liner to fill irregular internal surfaces and proximal boxes before placing the more viscous material as it can better wet and adapt to the tooth surface, thus sealing it, which may lead to a subsequent reduction in post-operative sensitivity.20,40,47
The application of an intermediate layer of either a low vis-cosity resin or glass ionomer cement between dentin and restorative resin has been shown to relieve polymerization con-traction stress by 20%–50%.20,48A 41% reduction in the vol-umetric contraction of resin composite restorations lined with a resin modified glass ionomer cement has been reported.48,49 Resmodified glass ionomers have higher early strength, in-creased fracture toughness and improved bond strength to tooth structure compared to conventional glass ionomers.50,51 The rationale of using flowable composite is to improve marginal adaptation while decreasing internal voids, ulti-mately resulting in a reduction in marginal leakage. Flowable composite creates an intimate union with the microstructural defects in the floor and the walls of the cavity preparation.
The lower elastic modulus of flowable composites (1–5 GPa) indicates a greater ability to flex with the tooth to accommo-date the inherent modulus of the tooth, which will eliminate gap formation and subsequent microleakage.52
The results of this study when comparing different liners show that the use of flowable composite liner at the cementum margin showed less microleakage when compared to resin modified glass ionomer cement, which is statistically significant.
The limitations of this study are that the restorative mate-rials when tested in vitro fail to stimulate the dynamic intra oral thermal changes induced by routine eating and drinking. Thermocycling is often employed in laboratory experiments to simulate stresses in the oral cavity however the absence of outward flow of the dentinal fluid and the completely altered dentinal surface due to extraction lead to a poor correlation between in vivo and in vitro conditions.52,53However micro-leakage studies can provide some initial information needed for the comparison of different new restorative materials.52
The silver nitrate method of measuring microleakage is an acceptable technique however it is a very severe test because the silver ion is extremely small (0.059 nm) when compared to the size of a typical bacterium (0.5–1.0lm) and thus is more penetrative. Therefore it may be assumed that any system that prevents the leakage of the silver ion will also prevent leakage of the bacteria.54
5. Conclusion
It can be concluded from the results that the use of the oblique insertion technique and use of an intermediate liner of flowable composite resin should always be employed when the cemen-tum margins are involved.
Source of support Nill. Conflict of interest None declared. Uncited references [14,21]. References
1. Yammazaki PCV, Bedran-Russo AKB, Pereira PNR, Swift Jr EJ. Microleakage evaluation of a new low-shrinkage composite restorative material.Oper Dent2006;31:670–6.
2. Nikolaenko SA, Lohbauer U, Roggendorf M, Petschelt A, Dasch R, Frankenberger R. Influence of C-factor & layering technique on microtensile bond strength to dentin. Dent Mater 2004;20:579–85.
3. Yoshikawa T, Nakaoki Y, Takada T, Burrow MF, Tagami J. Effect of light-curing method and irradiation time on marginal sealing and cavity wall adaptation of resin composite restorations. Am J Dent2003;16:63A–7A.
4. Perdigao J, Lambrechts P, Van Meerbeek B, et al. The interaction of adhesive systems with human dentin.Am J Dent1996;9:167–73.
5. Prati C, Chersoni S, Cretti L, Mongiorgi R. Marginal morphology of class V composite restorations.Am J Dent1997;10:231–6. 6. Alani AH, Toh CG. Detection of microleakage around dental
restorations: a review.Oper Dent1997;22:173–85.
7. Qvist V, Qvist J, Mjor IA. Placement and longevity of tooth coloured restorations in Denmark. Acta Odontol Scand 1990;48:305–11.
8. Brannstrom M. The cause of post restorative sensitivity and its prevention.J Endo1986;12:475–81.
9. Patterson RC. Bacterial contamination and the exposed pulp.Brit Dent J1976;140:231–6.
10. Browne RM, Tobias RS, Crombie IK, Plant CG. Bacterial microleakage and pulpal inflammation in experimental cavities.Int Endo J1983;16:147–55.
11. Ferracane JL. Developing a more complete understanding of stresses produced in dental composites during polymerization. Dent Mater2005;21:36–42.
12. Lim BS, Ferracane JL, Sakaguchi RL, Condon JR. Reduction of polymerization contraction stress for dental composites by two-step light-activation.Dent Mater2002;18:436–44.
13. Soderholm KJM. Does resin based dentine bonding work? Int Dent J1995;45:371–81.
14. Yoshiyama M, Sano H, Ebisu S, et al. Regional strengths of bonding agents to cervical sclerotic root dentin. J Dent Res 1996;75:1404–13.
15. Yoshiyama M, Carvalho R, Sano H, Horner J, Brewer PD, Pashley DH. Interfacial morphology and strength of bonds made to superfacial versus deep dentin.Am J Dent1995;8:297–302. 16. Carvalho RM, Pereira JC, Yoshiyama M, Pashley DH. A review
of polymerization contraction: the influence of stress development versus stress relief.Oper Dent.1996;21:17–24.
17. Swift Jr E, Perdigao J, Heymann HO. Bonding to enamel and dentin: a brief history and state of the art. Quintessence Int. 1995;26:95–110.
18. Torstenson B, Brannstrom M. Contraction gap under composite resin restoration: effect of hygroscopic expansion and contraction stress.Oper Dent1998;13:24–31.
19. Feilzer AJ, De Gee AJ, Davidson CL. Setting stress in Composite resin in relation to configuration of the restoration.J Dent Res. 1987;66:1636–9.
20. Kemp-Scholte CM, Davidson CL. Complete marginal seal of class V restoration effected by increased flexibility. J Dent Res 1990;69:1240–3.
21. Davidson CL, De Gee AJ, Feilzer AJ. The competition between the Composite-Dentin bond strength and the polymerisation contraction stress.J Dent Res.1984;3:1396–9.
22. Mehl A, Hickel R, Kunzelmann KH. Physical properties and gap formation of light cured composites with and without soft start polymerization.J Dent1997;25(3–4):321–30.
23. Hansen EK. Effect of cavity depth and application technique on marginal adaptation of resins in dental cavities. J Dent Res. 1986;65:1319–21.
24. Versluis A, Douglas WH, Cross M, Sakaguchi RL. Does an incremental technique reduces polymerization shrinkage stresses? J Dent Res.1996;75:871–8.
25. Dietrich T, Losche AC, Losche GM, Roulet JF. Marginal adaptation of direct composite and sand wich restorations in Class II cavities with cervical margins in dentin. J Dent 1999;27(2):119–28.
26. Lutz E, Krejci I, Oldenburg TR. Elimination of polymerization stresses of posterior composite resin restorations: a new restorative technique.Quintessence Int1986;17(12):777–84.
27. Mixson JM, Eick JD, Moore DL, Tira DE. Effect of two dentin bonding agents on microleakage in two different cavity designs.J Prosthet Dent.1992;67:441–5.
28. Barnes DM, Thompson VP, Blank LW, McDonald NJ. Micro-leakage of class-V composite resin restorations: a comparison between in vivo and in vitro.Oper Dent.1993;18:237–45.
29. Lutz F, Krijci I, Barbakow F. Quality and durability of marginal adaptation in bonded composite restorations. Dent Mater 1991;7:107–13.
30. Ferdianakis K. Microleakage reduction from newer esthetic restorative materials in permanent molars.J Clin Pediatric Dent 1998;22(3):221–9.
31. Tung FF, Estafan D, Sherer W. Microleakage of a condensable resin composite: an in vitro investigation. Quintessence Int 2000;31(6):430–4.
32. Eichmiller FC. Clinical use of glass ceramic inserts.Compendium 1992;13:568–74.
33. Peutzfeldt A, Asmussen E. Composite restorations: influence of flowable and self-curing resin composite linings on microleakage in vitro.Oper Dent2002;27:569–75.
34. Koran P, Kurschner R. Effect of sequential versus continuous irradiation of light-cured resin composite on shrinkage, viscosity, adhesion degree of polymerisation.Am J Dent.1998;11:17–22. 35. Weinmann W. Thalacker C & Guggenberger.Siloranes in dental
composites. Dental materials2005;21(1):68–74.
36. Winkler MM, Katona TR, Paydar NH. Finite element stress analysis of three filling techniques for class V light cured composite restorations.J Dent Res1996;75:1477–83.
37. Going RE, Massler M, Dute HL. Marginal penetration of dental restorations by different radioactive isotopes. J Dent Res 1960;39:273–84.
38. Van Nieuwenhuysen JP. D Hoore W, Carvalho J, Qvist V. Long term evaluation of extensive restorations in permanent teeth.J Dent2003;31(6):395–405.
39. Yoshikawa T, Sano H, Burrow MF, Tagami J, Pashley DH. Effects of dentin depths and cavity configuration on bond strength.J Dent Res1999;78:898–905.
40. Armstrong SR, Keller JC, Boyer DB. The influence of water storage and C factor on dentin – resin composite microtensile bond strength and debond pathway utilizing a filled and unfilled adhesive resin.Dent Mater2001;17:268–76.
41. Yaman SD, Sahin M, Aydin C. Finite element analysis of strength characteristics of various resin based restorative materials in class V cavities.J Oral Rehab2003;30:630–41.
42. Rees JS, Jacobsen PH. The effect of interfacial failure around a class V composite restoration analyzed by finite element method. Oral Rehab2000;27:111–6.
43. Katona TR, Winkler MM, Huang J. Stress analysis of a bulk filled class V chemical cured dental composite restoration. J Biomed Mater Res1996;31:445–9.
44. Katona TR, Winkler MM. Stress analysis of a bulk filled class V light cured composite restoration.J Dent Res1994;73:1470–7. 45. Yap AU. Effectiveness of polymerization in composite restoratives
claiming bulk placement: impact of cavity depth and exposure time.Oper Dent2000;25(2):113–20.
46. St Georges A, Wider AD, Perdigao J, Swift Jr E. Microleakage of class V composites using different placement. and curing tech-niques. An in vitro study.Am J Dent2002;15:244–7.
47. Kemp-Scholte CM, Davidson CL. Marginal integrity related to bond strength and strain capacity of composite resin restorative systems.J Prosthet Dent1990;64:658–64.
48. Svizero NR, D’Alpino PHP. MH Silva e Souza Junior, RM Carvalho. Liner and light exposure: effect on in-vitro class V microleakage.Oper Dent2005;30(3):325–30.
49. Tolidis K, Nobecourt A, Randall RC. Effect of a resin modified glass ionomer liner on volumetric polymerization shrinkage of various composites.Dent Mater1998;14(6):417–23.
50. Sidhu SK, Watson TF. Resin modified glass ionomer material. A status report for the.Am J Dent1995;8(1):59–67.
51. Gallo JR, Burgess JO, Ripps AH, Walker RS, Ireland EJ, Mercante DE, et al. Three year clinical evaluation of a compomer and a resin composite as class V filling materials. Oper Dent 2005;30(3):275–81.
52. Attar N, Turgut MD, Gungor HC. The effect of flowable resin composites as gingival increments on the microleakage of poster-ior resin composites.Oper Dent2004;29(2):162–7.
53. Pashley DH. Clinical considerations of microleakage. J Endod 1990;16(2):70–7.
54. Abdalla AI, Davidson CL. Comparison of the marginal integrity of in vivo and in vitro Class II composite restorations.J Dent 1993;21(3):158–62.
