doi:10.5368/aedj.2011.3.4.1.5

THE EFFECT OF FLOWABLE COMPOSITE LINING THICKNESS WITH VARIOUS CURINGTECHNIQUES ON INTERNAL VOIDS IN CLASS II COMPOSITE RESTORATIONS-AN

INVITRO STUDY.

^ Nagalakshmi Reddy S^Baiju Gopalan Nair^ Amarendher reddy.k* pratap kumar.M^Samba Shiva rao

ReaderProfessor and HeadProfessorProfessorReader

' ' Department of Conservative Dentistry and Endodontics ,G.Pulla Reddy Dental College, Kurnool , AndhraPradesh, India.''• Department of Conservative Dentistry and Endodontics, Meghana institute of Dental sciences, Mallaramvillage, nizamabad, Andhra Pradesh, India.

ABSTRACT:Aim of this studv was to compare class II composite restoration using flowable composites as lininq with various thickness andcuring techniques by evaluating internal voids. Fifty intact molars, each prepared with two box-only class II cavities, wererandomly divided into five groups: Group I, P 60 filling alone; Group II, ultra thin flowable composite lining (0.5-1 mm) co-curedwith overlying composite; Group III, thin lininq (1-1.5) co-cured with overlyinq composite; Group IV, ultra thin lininq (0.5-1 mm)precured and Group V, thin lining (1-1.5) precured. Internal voids were recorded in the gingival interface, cervical and occlusalhalves of restorations. Precured techniques for flowable composite lining showed the least number of interface and cervicalvoids where as the co-cured technique of flowable and packable composites showed the least number of occlusal voids.KEY WORDS: Packable composite; flowable composite; precure technique; co-cure technique; ultra thinlining and thin lining.

INTRODUCTION

Packable composite was developed by changing thefiller or matrix phase to increase viscosity for bettercondensation similar to that of amalgam'. However abilityto adequately adapt the internal areas was alwaysquestionable^. So in an attempt to reduce the voids,various incremental techniques, curing techniques andlining materials have been designed\ Flowablecomposites were introduced in late 1996. They are non-sticky and injectable. They have low viscosity andincreased wettability due to lower filler contend. Flowablecomposite as a lining material for class II resin compositesreduced voids'*. Considering the advantages anddisadvantages of various types of composites andtechniques, recently a new technique was introduced byJackson and Morgan 2000 where a thin layer of flowablecomposite is applied to cavity floor which is immediatelyfollowed by packable composite increment and light cured.Most of flowable composite is expelled while placingoverlying composite and its volume will be minimized. Thistechnique offers the advantage of two different compositesincluding intimate adaptation of filling and handlingproperties^. Accordingly this invitro study compared classII composite restorations using flowable composite liningeither with the modified incremental technique or withvarious thicknesses by evaluating internal voids.

MethodologyFreshly extracted fifty human molars were mounted

on dental stone with one premolar and one molar on themesial and distal sides to simulate posterior toothalignment and were prepared with standardized mesioocclusal and disto occlusal box only class II cavitieshaving bucco-lingual width 4 mm, mesio distal width 2mmand occluso gingival depth of 3 mm. Sectional matrix bandwas placed which was stabilized with G-rings and woodenwedges. They were etched with 35% phosphoric acid,washed thoroughly with water for 15 seconds and followedby the application of the two layers of single bond andeach layer was cured with curing light for 10 seconds. The50 molar teeth were randomly divided into 5 groups of 10teeth each. Group I: Cavity preparations were restoredwith posterior composite alone \.e.Pm, Group II: Cavitypreparations were lined with flowable composite (Filtekflow) to about 0.5-1 mm occluso gingival thickness, then1mm thick posterior composite (P6o) was insertedimmediately and cured together (co cured). Group III: Itwas similar to group II except lining thickness was 1-1.5mm, Group IV: Cavity preparations were lined withultra thin layer of flowable composite i.e. 0.5-1 mm andcured for 20 seconds (precured). Remaining cavity wasfilled with posterior composite. Group V: It was similar to

Vollll. Issue 4 Oct-Dec 2011 22

Table.1 Interface voids rating

Groups

Gr. 1Gr. IIGr. IllGr. IVGr. V

Comparisonbetweengroups

No.

4040404040

Gr. MlGr. NilGr. I-IVGr. I-VGr. IHIIGr. II-IVGr. Il-VGr. III-IVGr. Ill-VGr. IV-V

InterfaceVoids -

21 (52.5)34 (85)32 (80)40(100)40(100)t = 9.83)i' = 6.77)f = 24.91t = 24.91ï' = 0.35y '= 6.49y '= 6.49¡r' = 8.89t = 8.89ir'= 0.00

Voids +19(47.5)

6(15)8(20)

00

P = 0.01,SP = 0.01,S

P = 0.001, HSP = 0.001, HSP = 0.56, NSP = 0.05, SP = 0.05, SP = 0.01,SP = 0.01,S

P = 1.00, NS

Table.2 cervical voids rating

Groups

Gr. 1Gr. IIGr. IllGr. IVGr. V

Comparisonbetweengroups

No.

4040404040

Gr. NIGr. NilGr. I-IVGr. I-VGr. IHIIGr. II-IVGr. Il-VGr. IIHVGr. Ill-VGr. IV-V

CervicalVoids -4(10)

10(2.5)8(20)

13(32.5)18 (45)

l i ' = 3.11)c' = 1.57y ' = 6.05y' = 12.31 = 0.29y' = 0.55y '= 3.52y.'= 1.61r} = 5.70y ' = 1.32

Voids +36 (90)30 (75)32 (80)

27 (67.5)22 (55)

P = 0.08, NSP = 0.21,NSP = 0.05, S

P = < 0.05, SP = 0.59, NSP = 0.46, NSP = 0.06, NSP = 0.20, NSP = 0.05, S

P = 0.25, NS

Table.3 . Occlusal voids rating

Groups

Gr. 1Gr. IIGr. IllGr. IVGr. V

Comparisonbetweengroups

NO.

4040404040

Gr. l-llGr. l-lllGr. NVGr. I-VGr. ll-lllGr. II-IVGr. Il-VGr. III-IVGr. Ill-VGr. IV-V

OcclusalVoids -4(10)8(20)

7(17.5)5 (12.5)6(15)

y.^=1.57X' = 0.95y = 0.13)f.' = 0.46x' = 0.08y' = 0.83I = 0.35)(' = 0.39y' = 0.09y' = 0.10

Voids +36 (90)32 (80)

33 (82.5)35 (87.5)34 (85)

P = 0.21,NSP = 0.33, NSP = 0.72, NSP = 0.50, NSP = 0.77, NSP = 0.36, NSP = 0.56, NSP = 0.53, NSP = 0.76, NSP = 0.74, NS

Graph.1. Interface voids pattern

Grapli 1 : mtertace Voids Pattern

40

n

0 Interface VOIDS o

a Interf ace VOIDS 1

Grl Gril •>[ I v' l.?\ •

Graph.2. Cervical voids pattern

Graph 2 : Cervical Voids Patttm

10 -,

35 -

25 •

20 -

t5 •

10 -

5 -

0 nnCervtcal VOIDS 0

DCeivical VOIDS 1

Gr I Gr II Gt III CM- IV Gr \'

40

3S

30 •

20

1 5 •

1 0 •

6-

0

Graph.3. Occlusal voids pattern

Graph 3 : Occlusal Voldi Pittarn

n n• OccluMI VOIDS 0

Qcclusal VOIDS I

1

Grl GrII Ql Ul Si IV

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group IV except lining thickness was 1-1.5mm. Therestorations were cured via buccal and lingual aspects for20 seconds. They were mesio-distally sectioned using ahard tissue microtome and were examined under a 50xstereomicroscope. In Internal voids evaluation voids wereseen in three sites - Occlusal half of restorations. Cervicalhalf of restorations. Gingival interface (restorative interfaceof cervical margin). Voids were scored as follows: Novoids = 0, Visible voids = 1. Group wise comparisons aremade by Mann-Whitney test. Categorical data areanalyzed by Chi-square test. For all the tests a p-value of0.05 or less was considered for statistical significance.

Results:

Precured specimens showed less number of voids andcontrol specimens showed maximum number of voids. Ininterface and cervical half on comparison of curingtechniques, precured specimens showed less number ofvoids than co-cured specimens. (Table-I and Table II). Inocclusal half on comparison of curing techniques, co-cured specimens showed less number of voids thanprecured specimens. (Table-Ill). In interface and cervicalhalf on comparison of lining thickness and type of curing.Group IV showed less number of voids than Group V.(Table - 2). In occlusal half on comparison of liningthickness and type of curing. Group V showed lessnumber of voids than Group IV. Group II showed lessnumber of voids than Group III in interface and occlusalhalf. (Graph-1 and 3) Group III showed less number ofvoids than Group II in cervical half. (Grapii-2).

Discussion

With increased patient interest in esthetic alternativesto dental amalgam, the objectives were to modify thehandling characteristics of RBC". Voids are usuallyproduced by the air trapped during mixing or applicationprocedures. It is based on free radical polymerization andcontains redox system which promotes bulkpolymerization inhibition due to high chemical affinity ofatmospheric oxygen for free radicals. It creates surfacediscontinuities, which increases fracture propagation andfailure on loading. Poor marginal adaptation is related tointernal voids. Larger voids will reduce the mechanicalstrength of restoration®. To reduce the internal voids,flowable composites are used as a liner and cured, overwhich the final packable composite is placed and curedincrementally which was suggested as a precured methodof placement^ A study conducted to evaluate the effect offlowable composite lining on microleakage and internalvoids in class II composite restorations revealed fewcervical voids in flowable lining restorations'. Nowrecently, in a new technique called co-cured technique, athin layer of flowable composite is applied to the cavityfloor which is immediately followed by packable compositeincrement and then light cured together. This techniqueoffers the advantage of intimate adaptation of filling andimproved handling properties^. The present study was

conducted to compare class II composite restoration usingflowable composites as lining with various thickness andcuring techniques by evaluating the internal voids.

The result of the present study reveals that internalvoids predominantly consisted of interface and cervicalvoids (Tabie-I and Table II). Group I showed highprevalence of interface and cervical voids (Graph-1 & 2) .The presence of such voids may contribute to deficientcavity adaptation and unavoidable trapping of air whilemanipulating a posterior composite. Group II resultsindicated that the incidence of interface and cervical voidsdecreased when compared to Group I, with the applicationof flowable linings, but remained higher than the precuredgroups (Group-IV&V). The results of the present study arein agreement with a study conducted to evaluate themicroleakage and internal voids in class II compositerestorations with flowable composite lining (precured)showed a reduction in the number of voids as compared tothose in which flowable lining was usecf.Packing thecomposite may cause incorporation of air. A studyconducted to evaluate the incidence of interface voids andmicroleakage of class II box only composite restorationwith ultra thin flowable resin lining showed moderateincidence of interface voids^. A study conducted toevaluate effect of flowable resin composite onmicroleakage and interface voids in class II compositerestorations revealed reduced interface voids and totalnumber of voids were reduced in restoration^ .This is dueto enhanced cavity adaptation, low modulus of elasticity,increased wetting of flowable composites and there byleading to lesser number of voids'*.

The results of the present study are in agreement withanother study which evaluated shrinkage stress reductionon porosity concentration in thin resin layers. This studydemonstrated that reduced contraction stresses could beobtained by using a thin, pore containing lining material.Both the presence of minimal voids and setting inhibitioneffect caused by the oxygen present in these voids couldprovide relief polymerization stress and result in reducedmicroleakage. The study also suggests that care must betaken not to trap air during placement of flowablecomposite. The repeated packing motion followingplacement of overlying composite must be avoided toprevent undue porosity formation^.

From the results of the present study it can beconcluded that the co-cured flowable lining compositerestorations showed greater internal voids when comparedto precured flowable lining composite restoration.

CONCLUSION

An ultra thin lining of flowable composite at the baseof the cavity followed by precuring technique and then theincremental build up of packable composite showed theleast number of interface voids. A thin lining of flowable

Vol ill. Issue 4 Oct- Dec 2011 24

Fig.1. Schematic representation of class II box only cavitypreparation

Fig.3. Class II box preparation ( MO and DO)

Fjg.2. Specimens used in the study

Fig.4. Specimen after sectioning with microtomeFig.5. Specimen showing internal voids

Vollll. Issue 4 Oct-Dec 2011 25

composite at the base of the cavity followed by precuringtechnique and then the incremental build up of packablecomposite showed the least number of cervical voids. Anultra thin lining of flowable composite at the base of thecavity followed by co-curing technique of both the flowableand packable composite showed the least number ofocclusal voids.

References

1. Chuang SF, Liu JK. Effects of flowable compositelining and operative experience on microleakage andinternal voids in class II composite restorations. JProsthet dent 2001 ;85:177-83. PMid: 11208208http://dx.d0i.0rg/i 0.1067/mpr.2001.113780

2. Leevailoj C. Cochran MA, Matis BA, Moore BK, PlateJA. Microleakage of posterior packable resincomposite with and without flowable liners Oper Dent2001;26:302-307. PMid: 11357574

3. Malmstrom H. Schlueter M, Roach T, Moss ME.Effective thickness of flowable resins on marginalleakage in class II composite restorations. Oper Dent2002;27:373-380. PMid:12120775

4. Estafan D, Estafan A, Leinfelder K. Cavity walladapatation of resin based composites lined withflowable composites. J Am Dent 2000;13(4):192-194.

5. Chuang SF, Tin YT, Liu JK, Chang CH, Shieh DB.Influence of flowable composite lining thickness onclass II composite restorations. Oper Dent 2004;29(3):301-308. PMid:15195731

6. Chuang SF, Liu JK, Jin YT. Microleakage and internalvoids in Class II composite restorations with flowablecomposite linings. Operative Dentistry 2001;26:193-200.

7. KorkmazY, Ozel E, Attar N. Effect of flowablecomposite lining on microleakage and intemal voids inclassll composite restorations. Journal of Adhes Dent2OO7;9(2):189-194.

8. Olmez A, Oztas N, Bodur H. The effect of flowableresin composite on microleakage and internal voids inclass II composite restorations. Oper Dent2004;29(6):713-719. PMid:15646229

9. Alster D, Feilzer AJ, de Gee AJ, Mor A, Davidson CLThe dependence of shrinkage stress reduction ofporosity concentration in thin resin layers. Journal ofDental Res 1992;71(9):1619-1622. PMid:1522296http://dx.doi.Ofa/10.1177/00220345920710091401

Corresponding Author

Dr.Nagalakshmi ReddyDepartment of conservative Dentistry

G.pulla Reddy Dental college and HospitalNandhyala road

KURNOOL-518003PH:273360

Mobile:9490197767Email:lakshnni_reddy61 @ yahoo.com.

Vollll. Issue 4 Oct-Dec 2011 26

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