leakage of composite resin and glass ionomer cement restorations in retentive and nonretentive cervical cavity preparations Isaac Kaplan, DDS,a Harry H. Mincer, Edward F. Harris, PhQC and J. Steven University

of Tennessee, College of Dentistry,

DDS, MS, PhD,b Cloyd, DDSd

Memphis,

Tenn.

Ketac Fil glass ionomer cement (GIG) and Scotchbond 2 dentinal bonding agent (DBA)/Silux Plus composite resin restorations were inserted in cervical cavity preparations of extracted human teeth. After thermocycling, the specimens were invested and sectioned longitudinally and horizontally through the center of the restoration. Microleakage was evaluated as a ratio of the extent of methylene blue dye penetration at the tooth-restoration interface. Although all restorations exhibited leakage, both the GIC and bonded composite resin restorations recorded less leakage in retentive than in nonretentive cavity preparations. Composite resin restorations in nonretentive cavity preparations showed significantly more dye penetration toward the pulpal chamber than the GIC restorations. Ketac Fil GIC restorations inserted without a matrix strip exhibited less leakage than those with a matrix strip. The most desirable results were recorded with Scotchbond 2 DBAiSilux Plus composite resin restorations in retentive preparations. (J PROSTHET DENT 1992;68:616-23.)

omposite resin and glass ionomer cement (GIC) restorations are indicated for dental cervical lesions. These materials are capable of bonding to tooth structure, but they are also subject to microleakage that allows oral microorganisms, fluids, and chemical substances to migrate through the tooth-restoration interface. Passage of these materials can cause discoloration of the restoration, recurrent decay, sensitivity, and damage to the pu1p.i Polymerization shrinkage and thermal changes of the composite resin can also create a gap in the tooth-restoration interface that encourages leakage.2-6 Various studies have demonstrated that etched enamel and bonded composite resin form a strong micromechanical bond that resists leakage.7-12 However, the capability of the dentin or cementum composite resin bond to resist microleakage remains controversial.7-13 GICs chemically bond to dentin and enamel and liberate fluoride that inhibits decay.14-16 Their coefficient of thermal expansion is similar to that of tooth structure,ls, l6 but their capacity to prevent microleakage is also disputed.7, 12,17-z Various techniques for applying these restorative materials have been described, and some investigators have advocated retentive cavity preparations while others indicated that nonretentive cavity preparations were adequate.

aAssociate bProfessor cProfessor, dAssistant Dentistry 16/l/39920

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Professor, Division of Operative Dentistry. and Director, Oral Pathology. Department of Orthodontics. Professor, Director of Advanced Education Program.

in General

This study determined the microleakage of GIC and a bonded composite resin restoration in retentive and nonretentive cavity preparations of cervical cavities. Ketac Fil GIC (ESPE-Premier, Norristown, Pa.) and Scotchbond 2 dentinal bonding agent (DBA) (3M Co., St. Paul, Minn.) and Silux Plus composite resin (3M Co.) were selected for evaluation.

MATERIAL

AND

METHODS

Extracted intact human premolars and canines were selected for this study, and the teeth were initially stored in 10 % buffered formalin solution. After scaling and cleaning, the teeth were stored in tap water at room temperature. The teeth were divided in two groups. In group A, V-shaped nonretentive cavities were prepared on the facial surface at the cervix of each tooth (Fig. 1, A). Cavities were prepared to a depth of 1.2 to 1.5 mm using a No. 1700 carbide bur in a high-speed handpiece with water spray. In group B, conventional class V cervical retentive cavities were prepared on the facial surface of each tooth (Fig. 1, B). The cavities were prepared with a No. 34 carbide bur to approximate dimensions of 1.5 x 3 x 3 mm. The occlusal (or incisal) cavosurface margins were in enamel, and the gingival margins were in cementum. The enamel margins of retentive composite resin preparations were beveled, while the GIC preparations were finished in butt-joint margins. The teeth in each group were restored according to the manufacturer’s directions with: (1) Ketac Fil GIC without a matrix strip; (2) Ketac Fil GIC using a Uni-Strip (L. D. Caulk Co., Milford, Del.) matrix; or (3) Scotchbond 2 DBA and Silux Plus composite resin.

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0B

Fig. 1. Positions of restorations orientation of two saw cuts.

in nonretentive

For the Ketac Fil GIC restorations, Durelon (ESPEPremier) liquid was applied for 10 seconds to remove the smear layer of the preparation, and the cavity was then rinsed with water for 30 seconds and dried with air. After the Ketac Fil GIC capsule was t&mated, the material was inserted and contoured with a plastic instrument. After 1 minute the varnish was applied to the surface and was left undisturbed for 15 minutes. The excessive restorative material was removed with a flame-shaped carbide finishing bur under a water spray, the margins were trimmed with a No. 12 scalpel blade, and the restoration was finished at low handpiece speed with Sof-Lex (3M Co.) disks lubricated with cocoa butter. In the group with a matrix, a Uni-Strip matrix was applied with sustained finger pressure to secure the restora-

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n

(A) and retentive

(B) preparations

and

tion in place for 3 minutes. After removal of the matrix, varnish was applied to the restoration for 12 minutes, and it was then finished. For composite resin restorations, phosphoric acid gel was placed on the enamel for 15 seconds, then rinsed with water for 20 seconds and dried with air. Scotchprep (3M Co.) dentinal primer was applied to dentin for 60 seconds and dried with air. Scotchbond 2 adhesive was then applied to both the primed dentin and the etched enamel, and polymerized with a light curing unit for 20 seconds. Silux Plus composite resin was placed in two increments and each was cured for 20 seconds, with an additional 20-second final cure. The restoration was finished with Sof-Lex disks of decreasing abrasiveness, progressing from coarse to medium and finally to fine grits.

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Fig. 2. Longitudinal (A) and horizontal nonretentive preparation.

(B) cross sections of tooth with restoration

in a

Fig. 3. Longitudinal

(B) cross section of tooth with restoration

in a

retentive

(A) and horizontal

preparation.

All the restored teeth were stored in tap water for 1 week and were then thermocycled 100 times in a water bath between 4’ and 5P C with a l-minute dwell time in each bath. The apex of each tooth was sealed with sticky wax, and the teeth were coated with nail varnish to within 1 mm of the restoration. The teeth were placed in a 5 % solution of methylene blue for 4 hours and then rinsed until the dye was cleared from the surface. 618

ET AL

The teeth were then invested in clear casting resin. Using an Isomet (Bueler Ltd., Lake Bluff, Ill.) slow-speed diamond saw cooled with water, each tooth was sectioned longitudinally through the center of the restoration from the facial to the lingual surface. Each longitudinal section was further sectioned horizontally through the center of the restoration from mesial to distal surface (Figs. 1 through 3). Consequently, four sections resulted, and each OCTOBER

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Table I. Descriptive measurement site* Preparation and site

statistics

NO.

by technique Mean % dye penetration

and Standard error

Table II. Summary results of analysis of covariance for each of the four walls testing for differences between groups (treatments) adjusted for depth” Source

Nonretentive preparations Ketac Fil without matrix 15 Occlusal Gingival 15 15 Mesial 15 Distal 60 All surfaces Ketac Fil with matrix 15 Occlusal Gingival 15 15 Mesial 15 Distal All surfaces 60 Silux Plus and Scotchbond 2 29 Occlusal 29 Gingival 29 Mesial Distal 29 All surfaces 116 Retentive preparations Ketac Fil without matrix Occlusal 10 Gingival 10 10 Mesial Distal 10 All surfaces 40 Ketac Fil with matrix 15 Occlusal 15 Gingival 15 Mesial 15 Distal 60 All surfaces Silux Plus and Scotchbond 2 10 0cc1usal 10 Gingival 10 Mesial 10 Distal All surfaces 40

17.1 66.8 48.2 54.1 46.5

4.88 7.66 7.89 7.85 4.23

22.2 77.9 65.0 70.4 58.9

4.40 5.31 7.49 6.80 4.10

44.6t 59.4 51.2 50.7 51.5

6.60 5.38 7.38 7.76 3.60

4.0 34.9 23.0 20.4 20.6

2.67 10.57 10.05 3.16 4.37

19.7 57.1 41.7 34.4 38.2

6.56 7.18 8.29 0.21 4.01

4.0 1.9 1.9 3.9 2.9

2.18 0.95 1.27 2.06 0.83

“Variables are percentages of the restoration-tooth interface exhibiting staining (leakage). tNo dye penetration at enamel-composite interface itself; penetration was caused by backward leakage.

side of the cut (slice) was measured. The walls of each section were evaluated on each side of the cut, with a total of eight evaluations. The length of the wall on each side of the cut was measured, and the two readings were averaged and recorded. The occlusal, gingival, mesial, and distal walls were measured for the V-shaped preparation, while the THE

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Occlusal margin Treatments Depth Residual Gingival margin Treatments Depth Residual Mesial margin Treatments Depth Residual Distal margin Treatments Depth Residual

Degrees of freedom

Mean square

5 1 87

4,257 13,962 467

9.17 29.91-

5 1 a7

9,445 12,843 771

12.27 16.6?

5 1 87

6,811 13,601 910

7.5t 14.9t

5 1 87

7,833 8,768 921

8.5t 9.5.f

F ratio

*Depth was entered into the test simply to control for extraneous variation; the critical aspect is the test among treatments. tp

< 0.001.

axial wall length was incorporated with the reading of the respective adjacent wall for the retentive cavity preparation. Each section was examined at 20 power magnification under a binocular microscope. With an eyepiece reticle calibrated in millimeters, the length of the wall and the extent (length) of dye penetration at the tooth-restoration interface were measured. The degree of dye penetration (microleakage) was established as the ratio of the length of dye penetration to the length of the wall. The degree of dye penetration was scored separately for each wall. One-way analysis of covariance was used to control the differences in the depth of the preparation. Depth was the covariate; there was a modest but statistically significant positive association between depth and extent of microleakage (r = 0.26). The values presented have been adjusted for effects of depth, and analyses were performed with the BMDP statistical package (Biomedical Data Package, University of California, Berkeley, Calif.) at the University of Tennessee (Memphis).

RESULTS Descriptive statistics are listed in Table I, while analysis of covariance for group differences at the four tooth surfaces are presented in Table II. 1. Both the GIC (Ketac Fil) and the bonded composite resin (Scotchbond B/Silux Plus) recorded substantially less leakage in retentive cavity preparations (Figs. 4 and 5). The diminished microleakage of Scotchbond 2 adhesive/Silux Plus composite resin and Ketac Fil GIC without a matrix in retentive cavity preparations was statistically significant. The most desirable results were recorded with Scotch619

KAPLAN

0 ci M 0 Ketac F\l WIthout Matrix

I-

0 G M 0 Ketac Fil With Matrix

Non-F:etentive

0 G M II Silux Plus & Scotchbond 2

Preparations

---I

0 0 M II Ketac Fil WIthout Matrix

0

G M 0 K&c FII With Maim

+--Retentive

ET AL

0 G hl 0 SIIUX Plus 8‘ Scotchbond 2

Preparations

-I

Fig. 4. Average percent of dye penetration by type of restoration and form of preparation for each cavity wall. 0, Occlusal; G, gingival; M, mesial; D, distal.

Table

III.

penetration interface

Percentages of teeth exhibiting dye toward the pulp past the tooth-restoration No.

Preparation

technique

(surfaces)

Nonretentive preparations Ketac Fil, without matrix strip Ketac Fil, with matrix strip Silux Plus and Scotchbond 2 Retentive preparations Ketac Fil, without matrix strip Ketac Fil, with matrix strip Silux Plus and Scotchbond 2

NR R Ketac Fil Without Matrix

NR R Ketac Fil With Matrix

NR R Silux Plus & Scotchbond 2

5. Average percent of dye penetration of restorations in nonretentive (NR) and retentive (R) preparations.

Fig.

bond 2 DBA adhesive/Silux Plus composite resin in a retentive preparation (Fig. 4). 2. The occlusal or incisal walls of all Ketac Fil GIC restorations exhibited less leakage than the gingival, mesial, or distal walls (Fig. 4). Dye penetration at the dentinal restoration interfaces of the other three walls reflected comparable differences, but the mesial and distal surfaces showed less leakage than the gingival (Fig. 4). 3. Ketac Fil GIC restorations without a matrix strip exhibited less microleakage than those with a matrix strip (Fig. 4). This was true for both retentive and nonretentive cavity preparations. 4. Scotchbond 2 adhesive/Silux Plus composite resin restorations in nonretentive cavities displayed more leakage on the occlusal or incisal walls than the five other methods (Fig. 4), but this was attributed to the method of

620

Percent

60 60 116

20 12 40*

40

5 12 0

60 40

“This frequency is significantly higher than that of the other two preparations (x2 = 17.8; 2 df; p < 0.001). There is no difference among the three retentive preparations (x2 = 5.6; ‘2 df; p = 0.06).

scoring dye penetration. The staining resulted from leakage of the mesial, distal, or gingival surfaces and not through the enamel; the gingival, mesial, and distal walls exhibited similar dye penetration (Fig. 4). The dye did not penetrate the enamel-restoration interface from any direction. 5. Both restorations recorded microleakage, but (1) the restorations in retentive cavities leaked significantly less than those in nonretentive preparations and (2) retentive bonded composite resin restorations leaked less than retentive GIC restorations (Fig. 5). 6. Significantly more teeth with nonretentive composite resin restorations exhibited dye penetration in the dentin toward the pulp than teeth with similar GIG restorations (Table III).

DISCUSSION The groups of restorations recording excessive leakage were verified by preparing and processing additional samples. These samples displayed leakage that was similar to that manifested by the original group. There were minor

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Fig. 6. Composite resin restoration with leakage at dentin interface but not at enamel interface (“backward leakage”). E, Enamel; D, dentin; C, composite.

Fig. 7. Glass ionomer cement restoration and voids.

differences in depth of the cavities and a modest association between the depth and the extent of microleakage noted, but the values in the results were adjusted for various depths. Scotchbond 2 DBA adhesive/Silux Plus bonded composite resin restorations in nonretentive preparations recorded leakage in all surfaces, including the occlusal interface. This was also attributed in part to the method of scoring dye penetration, because dye penetration along any surface of a wall was recorded regardless of origin. Nevertheless, there was no leakage at the enamel-restoration interface; this leakage originated at the gingival, mesial, or distal cementum-restoration interface and continued through the dentin-restoration interface toward the enamel (“backward leakage”) (Fig. 6). Even backward leakage stopped at the dentinoenamel junction; no leakage was apparent at the enamel-restoration interface. A suitable marginal seal at the etched enamel and bonded composite resin interface has also been documented in previous studies, while microleakage at the dentin and bonded compos-

ite resin interface has varied according to reports.7-1” Small voids or channels were occasionally observed in the GIC restoration at 20 power magnification (Fig. 7), and using a matrix strip did not minimize the voids and channels. The voids probably originated from air bubbles trapped during trituration of the capsule. It was not clear if the channels were caused by crazing during placement and finishing of the restoration or whether they occurred during thermocycling. Leakage of dye through these channels was noted in certain instances. Glass ionomer restorations were occasionally discolored by the dye. This could have resulted from penetration of the dye through the material, despite the absence of leakage at the tooth-restoration interface. The composite resin restorations recorded no dye discoloration and microscopically appeared more homogenous than the GIC. Although some microleakage occurred with bot,h materials, composite resin restorations in nonretentive cavity preparations recorded more specimens with dye penetrating toward the pulpal chamber through the dentin past the

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tooth-restoration interface than did the glass ionomer restorations. This suggested that the dentinal tubules were sealed better at the tooth-restoration interface by glass ionomer cements. The extent of the dye penetration was not measured pulpally, and only the number of specimens showing penetration of dye through the tubules was recorded. Different dyes penetrate dentinal tubules at varying rates, so it is possible that once the dye invades the tubules it will eventually reach the pulp. The retentive cavity preparations for both composite resin and GIC restorations exhibited less leakage than the nonretentive cavity preparations. This is in agreement with the finding of Monteiro et al. 21that composite resin restorations in conservatively prepared cavities were adequately sealed. Although their study did not support the performance of glass ionomer restorations, our study confirmed improved sealing with the retentive glass ionomer restoration. Levy et al. 22recommended that standard retention be included in composite resin and glass ionomer restorations for root surface caries because a number of nonretentive restorations were displaced during their clinical study. These results also indicated that retentive preparations were preferable for both composite resin or glass ionomer cervical restorations. Leakage of the cervical composite resin restoration may be attributed to (1) a contraction gap that forms under the restoration from polymerization shrinkage2 and (2) expansion and contraction with temperature changes, because the coefficient of thermal expansion of composite resins is different from that of the dental hard tissues.4 Polymerization shrinkage may create substantial microleakage even before thermal cycling,” and changes in temperature can accelerate leakage.6 Staninec et a1.3discovered that marginal microleakage correlated with the presence and size of interfacial spaces.They demonstrated that the space at the occlusal and cervical walls generally increased in the cold state, indicating shrinkage of the restorative material. The space in the axial wall expanded during the hot state, indicating expansion of the material and movement in a facial direction.3 It would appear that a retentive cavity preparation restricts the movemen.t of composite resin restorative material. Conversely, GIGS exhibit limited shrinkage during setting16 and their coefficient of thermal expansion is similar to that of dentin,la, l6 so their leakage cannot be explained by the same reasons. Their inability to seal may be attributed to two factors: (1) the material is sensitive to moisture during placement and early set and (2) dehydration after the set may result in crazing and cracking.14-l6 Loss of water may cause the restoration to crack or shrink and stress newly forming ionic bonds, possibly leading to loss of adhesion.14Thermocycling may also cause crazing and cracking. The disparity of temperatures from thermocycling may weaken the already low bond strength of Ketac Fil GIC to tooth structure, resulting in microleakage at the toothrestoration interface,20 622

ET AL

Ketac Fil GIC restorations inserted without a matrix strip exhibited less microleakage than those restored with a matrix, and this was evident for both retentive and nonretentive cavity preparations. In all comparisons, restorations inserted without a matrix strip exhibited less staining on average than those inserted with a matrix strip. These consistent results indicated that using matrix strips for cervical GICs was unwarranted. CONCLUSIONS 1. Both the GIC (Ketac Fil) and the bonded composite resin (Scotchbond 2/Silux Plus) restorations exhibited some leakage. 2. Both types of restorations displayed considerably less overall leakage in retentive than in nonretentive cavity preparations. 3. The most desirable results in this study were recorded with Scotchbond 2 adhesive/Silux Plus composite resin in retentive cavity preparations. 4. Ketac Fil GIC restorations inserted without a matrix strip exhibited less leakage than those inserted with a matrix strip. 5. More teeth with nonretentive composite resin restorations showed dye penetration in the dentin toward the pulp than teeth with corresponding glass ionomer restorations. REFERENCES 1. Bauer JG, Henson JL. Microleakage: a measure of the performance of direct filling materials. Oper Dent 1984;9:2-9. 2. Tortenson B, Branstrom M. Contraction gap under composite resin restorations: effect of hygroscopic expansion and thermal stress. Oper Dent 1988;13:24-31. 3. Staninec M, Mochizuki A, Tanizaki K, Fukuda K, Tsuchitani Y. Interfacial space; marginal leakage, and enamel cracks around composite resins. Oper Dent 1986;11:14-24. 4. Bullard RH, Leinfelder KF, Russell MC. Effect of coefficient of thermal expansion on microleakage. J Am Dent Assoc 1988;116:871-4. 5. Crim GA, Garcia-Godoy F. Microleakage: the effect of storage and cycling duration. J PROSTHET DENT 1987;57:574-6. 6. Eakle WS. Effect of thermal cycling on fracture strength and microleakage in teeth restored with a bonded composite resin. Dent Mater 1986;2:114-7. 7. Retief DH. Are adhesive techniques sufficient to prevent microleakage? Open Dent 1987;12:140-5. 8. Gwinnett AJ. Interactions of dental materials with enamel. Tram Acad Dent Mater 1990;3:30-54. 9. Eakle WS, Nakamoto DK. Microleakage in MOD resin composite with three dentin bonding agents. Dent Mater 1989;5:361-4. 10. Grim GA. Influence of bonding agents and composites on microleakage. J PROSTHET DENT 1989;61:571-4. 11. Sparrius 0, Grossman ES. Marginal leakage of composite resin restorations in combination with dentinal and enamel bonding agents. J PROSTHET DENT 1989;61:678-84. of several 12. Gordon M, Plasschaert AJM, Stark MM. Microleakage tooth-colored restorative materials in cervical cavities. A comparative study in vitro. Dent Mater 1986;2:228-31. 13. Wenner KK, Fairhurst CW, Morris CF, Hawkins IK, Ringle RD. Microleakage of root restorations. J Am Dent Assoc 1988;117:825-8. for 14. Mount GJ. Restoration with glass-ionomer cement: requirements clinical success. Oper Dent 1981;6:59-65. 15. Charbeneau GT. Principles and practice of operative dentistry. 3rd ed. Philadelphia: Lea & Febiger, 1988304.9. 16. Albers HF. Tooth colored restoratives. 7th ed. Santa Rosa, Calif.: Alto Books, 1985:chap l;l-13.

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22. Levy SM, Jensen ME, Doering JV, Sheth JJ. Evaluation of a glass ionomer cement and a microfilled composite resin in the treatment of root surface caries. Gen Dent 1989:37:468-72.

17. Co&y RL, Robbins JW. Glass ionomer microleakage in class V restorations. Gen Dent 1988;36:113-5. 18. Alperstein KS, Grover HT, Herold RCB. Marginal leakage of glass-ionomer cement restorations. J PROSTHET DENT 1983;50:803-7. 19. Charbeneau GT, Bozell RR. Clinical evaluation of glass-ionomer cement for restoration of cervical erosion. J Am Dent Assoc 1979;98: 936-9. 20. Thornton JB, Retief DH, Bradley EL. Marginal leakage of two glass ionomer cements: Ketac-Fil and Ketac-Silver. Am J Dent 1988;1:35-8. 21. Monteiro S Jr, Sigurjons H, Swartz ML, Phillips RW, Rhodes BF. Evaluation of materials and techniques for restoration of erosion areas. J PROSTHET DENT 1986;55:434-42.

Enhancement preliminary

of antimicrobial report

Curt Goko, DDS,a Ft. Lewis, Wash.

and Gerald

R. Aaron,

Reprintrequeststo: DR. ISAAC KAPLAN UNIVERSITY OF TENNESSEE, MEMPHIS COLLEGE OF DENTISTRY DEPARTMENT OF GENERAL DENTISTRY 875 UNION AVE. MEMPHIS, TN 38163

properties DDS,

of cavity

varnish:

A

MSb

Bacterial contamination beneath amalgam restorations has been a problem in restorative dentistry. Cavity varnish improves the marginal seal but possesses no antibacterial properties, and chlorhexidine gluconate is a known antimicrobial substance. This study investigated the efficacy of a chlorhexidine gluconate/cavity varnish mixture against Streptococcus mutans, S. salivarius, and Escherichia eoli. The in vitro results indicated that the addition of chlorhexidine gluconate to cavity varnish improved its antimicrobial properties. (J PROSTHET DENT 1992;68:623-5.)

ne of the long-standing problems in the placement of amalgam restorations is bacterial contamination between the alloy and the cavity preparation. This bacterial contamination is implicated in recurrent decay and pulpal inflammati0n.i Microorganisms under the amalgam are attributed to either bacteria present in the 1 to 5 pm smear layer of the cavity preparation or to marginal microleakage at the cavosurface margin of the amalgam restoration.2-7 The problem of microleakage is partially resolved by using resin varnishes before the placement of the amalgam. However, these cavity varnishes are not completely effective in preventing microleakage, and bacterial contamination still occurs at the restoration-tooth interface.s-l1 The problem of bacterial contamination in the cavity preparation has not presently been resolved despite the increased use of a rubber dam.2 Although th(ey are bactericidal, cavity preparation cleansers are also traumatic to the exposed dentin, open the dental tubules, and cause pulpal kyperemia.12

Fig. 1. Inhibitory zone equals average of two perpendicular diameters of area depicting inhibition, minus diameter of paper dot sample.

The opinions expressed herein are those of the authors and are not

to be construed as official or as reflecting the views of the U. S. Army or the Department of Defense. aMajor, U.S. Army, DC; Pediatric Dentistry. bColonel, U.S. Army, DC; Pediatric

Dentistry.

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Chlorhexidine gluconate possesses proven antibacterial capabilities13, I4 and binds with organic and inorganic components of the tooth to precipitate pentose and pkosphorus in a bacterial cytoplasm.15 This study evaluated the

623