Microleakage of composite dentin bonding systems Anthony H. L. Tjan, DrDent, James R. Dunn, DDSC Loma Linda University,

resin cores treated

with various

DDS,* Ben E. Grant, DMD,b and

School of Dentistry,

Loma Linda, Calif.

Composite resin post and cores have gained widespread acceptance as an alternative for cast-gold post and core systems. A prefabricated metal post is generally used. Substantial microleakage at the interface between the composite resin core and the dentin substrate may occur. A tight and impervious bond between the dentin and the restorative material is critical for the longevity of core restorations. This study compared the microleakage of composite resin cores treated with various dentin bonding agents, including the recently developed Gluma, Tenure, and Scotchbond 2. The results indicated that Tenure and Scotchbond 2 bonding agents were most effective in reducing microleakage, followed by Gluma and conventional Scotchbond (Dual Cure) bonding agents. Although all proprietary dentin bonding systems used in this study significantly reduced microleakage, no system was capable of preventing microleakage completely. (J PROSTHET DENT 1991;66:24-9.)

P

osts and cores are routinely used for restoring endodontically treated teeth. Composite resin post and core systems used with a prefabricated metal post have become an accepted alternative for cast-gold post and core systems.1e5The procedure is simple, less time-consuming, and is less costly. Available composite resins are not inherently adhesive to tooth structure and do not effectively seal the cavity preparation.6 A previous microleakage study7 demonstrated dye penetration at the interface between the composite resin core and the dentin substrate, as a progression of marginal leakage of the final cast restoration. This leakage is from a microscopic interfacial gap resulting from the lack of adhesion of composite resin to tooth substrate and polymerization contraction. The dentin bonding agent must achieve a bond between dentin and composite resin with sufficient strength to counteract the polymerization contraction force of the composite resin to prevent a contraction gap.8-11The most current dentin bonding systems are Gluma (Columbus Dental, St. Louis, MO.), which is glutaraldehyde-based; Tenure (Den-Mat Corp., Santa Maria, Calif.), a version of Bowen’s formula; and Scotchbond 2 (3M Corp., St. Paul, Minn.), a hydrophylic monomer. This study evaluated and compared the microleakage at the composite resin-dentin interface of Para-Post (Whaledent International, New York, N.Y.) post-retained composite resin cores after the dentinal adherend surfaces had

aProfessor and Director of Biomaterial Research, Department Restorative Dentistry. bProfessor, Department of Restorative Dentistry. CAssistant Professor, Department of Restorative Dentistry. 10/1/22263

24

of

Fig. 1. Diagram of criteria for scoring values of microleakage.

been treated with various dentin bonding agents, including Gluma, Tenure, and Scotchbond 2.

MATERIAL

AND METHODS

Sixty human mandibular premolars stored in tap water since extraction were selected. The tooth apex was sealed by placing an amalgam filling (Dispersalloy, Johnson & Johnson Dental Products Co., East Windsor, N.J.) to prevent leakage through the apex. The coronal portions of the teeth were then removed approximately 2 mm above the cementoenamel junction and chamfer finish margins were established approximately 1 mm from the cementoenamel junction. Residual pulpal tissues were removed using endodontic files. Post spaces were prepared with a twist drill

JULY 1991

VOLUME66

NUMBER 1

MICROLEAKA,GE

OF COMPOSITE

Table I. Dentin

RESINS

bonding systems studied Batch

Product

Scotchbond

Manufacturer/distributor

number

3M Corp., St. Paul. Minn.

Resin: 7AX I,iquid: SBA

(Dual Cure)

3M Corp.

Sce)tchbcnd 2 system Zght Cure Adhesive ‘?entin Primer (Scotch Prep)

SH IP PH 14P Columbus Dental. St. Louis, MO.

819°K 7952H IO42D Tenure Dentjn Bondin,: Dentir conditioner Powder A Powder B -Liquid

Table II. Specimen No.

Core bsse microleakage ---

‘91009 513012 Ci12610 334012

raw score frequencies

Control l-4*

2 3 4 5 6 7 8 9 10

EDTA

12.5)

4-5 5-5 4-4 4-4 4-4

(4.5) (5.0) (4.0) (4.0) (4.0)

1-2 (1.3)

4-4 (4.0) 4-4 (4.0) 1-2 (1.5)

3.580

Mean

Den-Mat Corp., Santa Maria, Calif.

system

4-5 4-4 5-5 2-2 5-5 4-4 2-4 2-4 4-4 4-4

(4.5) (4.0) (5.0) (2.0) (5.0) (4.0) (3.0) (3.0) (4.0) 14.0)

3.85

and mean scores of group Gluma

l-2 (1.5) :3-3 (3.0) :3-3 13.0) l-2 11.5) l-3 (2.0) 4-3 i3.5) 1-l

11.0)

Scotchbond l-2

(1.5)

2-l

(1.5)

2-2 (2.0) 2-3 (2.5) 2-2 (2.0) :3-d i3.0i ‘-1

(1.5)

‘-3 (“.,5i 2-3 (23)

o-2 (1.0)

:3-l 12.n)

Z-1 ;1.sj

2-1 (1.5)

2.d 0.051. However, Scotchbond 2 and Tenure bonding agents werf significantly more effective in reducq

THE

JOURNAL

OF PROSTHETIC

DENTISTRY

ing microleakage than either Gluma or conventional Scotchbond bonding agents at p < 0.05 (Fig. 4). In addition, 20% of the specimens in groups 5 and 6 were totally impervious to basic fuchsin dye.

DISCUSSION Among the important properties of dentin bonding agents are their bond strength to dentin and their effect on microleakage. Conflicting results have been reported in a number of microleakage studies.” Some have reported a significant or potential reduction in microleakage. Results of this in vitro study indicated that the use of dentin bonding agents afforded significant reduction in microleakage at the composite resin core bases. Unfortunately, none of the proprietary dentin bonding agents tested produced predictably and consistently leak-free restorations. Tenure and the new Scotchbond 2 bonding agents were found to be the most effective in reducing microleakage, with 20ci, of the sample completely impervious to dye penetration. Gluma bonding agent performed in a manner comparable with the phosphonate ester-based Scotchbond (Dual Cure) bonding agent and was significantly less effective than Tenure and Scotchbond 2 bonding agents. Obviously, this recently developed agent Gluma, a dentin bonding system that mediates a bond between the organic phase of the dentin and the restorative resin through an interaction of glutaraldehyde with collagen,13 did not perform as well as we had anticipated. This may have been caused by the thermocycling and/or by incompatibility with the composite resin used. Robinson et a1.i4 reported t,hat interchanging of dentin bonding agents with compos-

27

TJAN,

GRANT,

AND

DUNN

Fig. 4. A, Microleakage of specimen treated with Gluma bonding agent. B, Microleakage of specimen treated with conventional Scotchbond bonding agent. C, Microleakage of specimen treated with Scotchbond 2 bonding agent. D, Microleakage of specimen treated with Tenure bonding agent.

ite resins from different manufacturers can produce incompatibility, and may impair performance. In addition, marginal leakage may be reduced more effectively by selecting a material with a coefficient of thermal expansion close to that of tooth structure.15 Microleakage occurs when the force created in the composite resin resulting from polymerization contraction exceeds the bond strength generated by the dentin bonding agent.‘O This leakage results in the composite resin’s pulling away from the dentinal adherend surface and creating an interfacial gap.“j To prevent contraction gap, the dentin bonding agents must achieve a rapid bond between dentin and composite resin that is sufficiently strong to counteract the polymerization contraction force of the composite resin.8-11 Although dentin bonding agents have undergone tremendous improvement and rapid development over recent years, presently available dentin bonding agents are still unable to prevent marginal gaps. This marginal gap can permit bacteria and/or their exotoxins to penetrate into pulp, causing pulpal irritation and secondary caries.17pl8 In core restorations, this microleakage may cause secondary

28

caries and/or may complicate the endodontic treatment, subsequently influencing the longevity of dental restorations. It has been suggested that a clean dentin surface enhances the bonding of a restorative material. A number of agents have been evaluated for their effect on the smear layer, including EDTA. Bowenlgp2o found that bond strength was improved by pretreatment with dilute acid or base or EDTA. Our study found no reduction in microleakage compared with control values by removal of the dentinal smear layer alone using a buffered solution of EDTA.

SUMMARY

AND CONCLUSION

This study evaluated and compared microleakage at the dentin-composite resin interface of Para-Post post-retained composite cores with various dentin bonding agents including the most recently developed Gluma, Tenure, and Scotchbond 2. The results indicated that the use of dentin bonding agents afforded significant reduction in microleakage. However, none of the proprietary dentin bonding systems were able to produce consistently leak-free restora-

JULY

1991

VOLUME

66

NUMBER

1

MICHOLEAKAGE

OF

I’OMPOSI’IE

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tions. Tenure anti Scotchbond 2 bonding agents were the most effective, followed by Gluma and conventional Scotchbond bonding agents

12. ::I.

REFERENC’FS 2 JL Spanauf .4.1. I )owel and core found Itions using the crmpwite .4daptic Quintessence lnt 197%: 1:49-51. Stahl GJ, 0’Neal F1H. ‘I he complrsi e resin dowel and core .I PROS?‘HE? Ikw l975.:u:642 8. Steele GD. Rcinfo,ced ~vmpw;ite resin foundations lor rndodonticall! treat,ed teeth. .I PIIOSTHETDE:NT 1973;30:816-9. Moll JFP, Howe I)F, ivare (‘IV. Cast gold post and o,re and pink retamed composite resin bases: a comparative study in strength. .I

1% 16.

I'RosTH~':~'l&wr 1978;40:fi42-4.

17.

I 1.

.j.

Rzepka H:;, Abrams FL. Simplifiration of cast and composite resin buildups. .J ~'HOs'rHE:I‘IlENT !982;18:544-6. Ii. Howen HI,. Properties of a silira-re nforced polymer for dental rest~~ra tions. d An] Ilent 4~~0~ 196:3;66:57-61. ‘7. Than AHL. C‘hui .J. Microleakage of xze materials for complete cast