Microleakage and marginal adaptation in conventional and adhesive Class II restorations

Microleakage

and

and

Class II restsrations

adhesive

marginal

ad

on in conve&w3ul

Bernhard Luescher, D.M.D.,* Felix Lutz, M.D., DAD.,* and Hans R. Miihlemann, M.D., D.M.D.** D.M.D.,* Dental Institute, University of Zurich, Zurich, Switzerland

Heinz

Ochsenbein,

u onventional cavity preparation embodies some severe disadvantages. Class II amalgam restorations sacrifice a large amount of sound tooth tissue if the dentist adheres to Black’s principles of cavity preparation. Extension for prevention and resistance and retention forms probably account for most losses of hard tissue. Although composite resin restorative materials have been used for some years, the cavity preparation principles remain largely unaltered despite the fact that the physical properties of composite resins differ from those of amalgam. Therefore, there is no compensation for disadvantages inherent in composite resins, and their advantages are not fully utilized. No restorative material is strongly adhesive to tooth structure unless the hard tissues are conditioned first. Unrelated to the class of cavity, a lack of mechanical bond or adhesion inevitably leads to a poor marginal seal. The consequences of marginal leakage for calcified tissue and the pulp have been discussed elsewhere.le3 Many reports deal with the problem involved in measuring the adaptation of modern restorative materials to tooth structures.1 Static intrusion tests, such as penetration of dyes and radioisotopes, and geometric methods (e.g., microphotography and profiling) h ave been used for the evaluation of the marginal sea1.4-7 It has been demonstrated that etching of enamel surfaces definitely results in improved marginal adaptation of resins to enamel and in less microleakage because of increased wettability of etched enamel. ‘, ’ The question has been raised as to what effect low-viscosity sealants have on the retentive strength of composite materials in tensile tests.1°-13 The results, even in samples of the same brand of composite resin, are highly contradictory, probably due to the use of varying test conditions.1” Nevertheless, the tensile adhesion of most brands to etched enamel apparently is sufficient, irrespective of whether a sealant is applied or not.

300

*Senior Research Associate, Department

of Cariology

and Periodontology.

*“Professor

of Cariology

and PeriodontoIogy.

and

Chairman,

Department

Microleakage

Fig. 1. Adhesive enamel.

cavity

preparation

and marginal

showing

proximal

adaptation

aspect.

Dotted

of restorations

area

shows

301

beveled

In a scanning electron microscope (SEM) study, Meurman and co-worker+ reported that two sealants had filled all the spaces between restoration and etched enamel. On the other hand, Williams and associates’” showed that a variety of polymers will, at some point in time, permit penetration of dye along the enamel/ sealant interface. An unconventional cavity preparation for composite resins has recently been described by Lutz and Burkart. I6 It saves sound, hard tooth tissue and benefits from the advantages of enamel conditioning. This adhesive restoration (AR) technique has been successfully utilized in Classes III, IV, and V cavities for some years.” Additionally, proximal carious enamel and dentin were removed with round burs, producing a round or ovoid cavity. The enamel was undermined and beveled toward the tooth surface along the entire cavity margin with high-speed tungsten carbide burs (Fig. 1) . Occlusal carious dentin was removed with excavators and round burs after opening the fissures with rotating diamond points. The enamel was allowed to remain undermined and was beveled along its outline (Fig. 2, A and B) . It was the aim of this study to test, in vitro, the feasibility of using adhesive restorations in Class III cavities. In addition, the effects of enamel etching and of several variables, such as low-viscosity sealant, insertion, cavity preparation, sealing time, and brand of composite resin, on marginal adaptation and microleakage were investigated. Dye penetration tests were combined with scanning electron microscope observations of the marginal seals. MATERIAL

AND

METHODS

After extraction, 65 maxillary and mandibular caries-free molars were stored for a few days in a 0.2 per cent solution of chlorhexidine. A summary of the different treatments is given in Table I. Conventional MOD cavities were prepared in 30 teeth using a high-speed, watercooled instrument with diamond burs. At the proximal outlines of each molar, a 1 mm. band of cervical enamel was left between the cavity margin and root cementurn. An effort was made to achieve cavity preparations of uniform size. No cavity liners

302

Luescher

Fig. 2. Adhesive cavity B, mesiodistal aspect.

Table

.I. Pr D Ma 19

et al.

preparation:

1. List of treatments

A, occlusal

for groups

aspect

showing

Treatment

Legend:

centric

contacts;

groups

IA

IB

2A

28

3A

38

4

5A

5B

6

7

8

9

cv -

cv -

cv f _

cv + -

CY + +

cv + +

cv* + +

ap + +

ap + +

ap + -

ap* + +

ap + +

ap + +t

AAAAAAAAAAACC P I P

I

P

I

P

P

I

P

P

P

P

cu, conventional

preparation;

cotton

I, green

P, ethanol-wetted

occlusal

1A to 9 Treatment

Cavity preparation Etching for 6Oseconds Sealing Restorative material Condensation method

(0)

pellet;

up, adhesive preparation; impression compound.

A,

Adaptic;

C, Concise;

*Modified. tSealant set for 30 minutes. were applied. A matrix band* was placed around every crown. It was fixed cervically with a clamp device in order to simulate the function of an interdental wedge. In the first group, 10 teeth were restored with composite resin? without enamel etching. The composite resin had been mixed according to the manufacturer’s instructions. After insertion, in order to condense the restoration, a load was exerted from the occlusal aspect ( 1) with a cotton pellet moistened with ethanol (five specimens, designated 1A) and (2) with an occlusal impression of green modeling plastic (five specimens, designated 1B). In order to avoid adhesion of the resin to the compound, the composite resin was covered with a 5 ,U thick polycarbonate foi1.S In the second group of 10 molars, also subjected to conventional cavity preparation, the enamel was etched with 37 per cent phosphoric acid for 1 minute and then flushed with tap water prior to the insertion of the restorative material. The condensation method was the same as the two methods already described (five specimens each in subgroups 2A and 2B). *Automatrix, tAdaptic, $Kindly

The

L. D. Caulk

Company,

Johnson

& Johnson,

East Windsor,

N. J.

Leverkusen,

West

provided

by Bayer

AG,

Milford,

Del. Germany.

Microleakage

Fig.

3. Enamel

Fig.

4. Unconventional

beveling

and marginal

and conventional cavity

cavity

preparation

adaptation

preparation

showing

(group

proximal

dent

of restorations

303

4). (group

7).

In the third group, a layer of a low-viscosity sealant* was applied in another 10 etched cavities prior to insertion and condensation of the composite resin by the two different methods (groups 3A and 3B). In the fourth group, the conventional cavity preparation was modified by pronounced beveling of the cervical cavity margins (Fig. 3) in order to increase the enamel surface area. The cavities were then etched, sealed, and filled as described for group 3A. The cavity preparation of the remaining 30 molars (descriptions following) was performed following the principles of adhesive restoration. In the fifth group, 10 AR cavities were etched, sealed, and filled with the composite resin and condensed in two different ways as described for group 3 (subgroups 5A and 5B). In the sixth group, five AR cavities were etched and filled with the restorative material without prior sealing. In the seventh group, the AR preparation was modified: The spherical proxima1 cavity was replaced by simple “dents” as shown in Fig. 4. The five cavities were etched, sealed, and filled according to the procedure for group 3A. In the eighth group, five AR restorations were prepared with another composite resin,? adhering to the procedures used for the fifth group. Finally, in the ninth group, the sealant layer was allowed to set for 30 minutes on the etched enamel prior to insertion of the restorative material. Replica impressions$ for SEM observations were made of each proximal restoration surface immediately after removal of the matrix band. Thereafter, the restorations were polished with 3M discs under a water spray, and replica impressions were again made of either proximal surface in all treatment groups 4 and 7. Subsequently, all 65 teeth were coated with a double layer of uncolored nail varnish, except the proximal surfaces of the restoration, and dipped into a 0.5 per cent aqueous solu-

l Adaptic

bonding

*Concise

enamel

SXantopren

blue,

agent, bond Bayer

Johnson

system, AG,

3M

& Johnson, Company,

Leverkusen,

East Windsor, St. Paul,

West

Germany.

Minn.

N. J.

304

Luescher

J. Prosthet. March,

et al.

II

0 9

58

Fig. 5. Average Table II.)

Table

dye

II. Definition

penetration

scores

in

treatment

of scores of dye penetration

groups

IA

Dent. 1977

to 9. (Definition

at cavity/restoration

of scores

in

interface

Penetralion

Score 0 I

No

Within enamel thickness Within enamel and into similar depth of dentin Through whole enamel thickness and dentin As in Score 3 and additionally into dentinal tubules Profuse and into dentinal tubules and LWIII

2 3 4 5

tion of basic fuchsin (pH of 5.9). After 20 hours of immersion, the molars were washed in tap water and sectioned mesiodistally with a slowly rotating saw.* The proximal portions in one half of every molar were examined under a stereomicroscope and photographed. The amount of fuchsin penetration along the cavity/restoration interface was determined using the scores listed in Table II. An electron microscopic examination of the proximal cavosurface margins before and after polishing was also made. The total length of the proximal cavity margin was divided into 20 sections of equal size. Each section was observed through the SEM+ and grouped according to one of the following parameters : ( 1) space margin, (3 ) overfilled margin, or between composite resin and tooth, (2) underfilled (4) perfect adaptation. These four qualities were expressed in percentages of the total length of the proximal cavity margin. *Isomet

saw, Buehler,

$Super-Mini-SEM,

Ltd., International

Evanston,

111.

Scientific

Instruments,

Inc.,

Mountain

View,

Calif.

Volume Number

37

Microleakage

3

and marginal

3A

Fig. 6. Micromorphologic underfilled or overfdled percentages of the total ing procedures.

38

adaptation

of restorations

305

5A

quality of marginal adaptation of 11 treatment groups: Fissures, marginal regions, and perfect marginal adaptation are expressed as length of the proximal cavity margin (A) before and (B) after polish-

RESULTS Dye penetration. Dye penetration is shown diagrammatically in Fig. 5. Almost no occurred in groups 5, 8, and 9. In these teeth, the adhesive cavity preparation was combined with enamel etching and the use of a low-viscosity sealant. penetration Absence

of

etching

or

sealing

markedly

enhanced

dye

penetration;

no

differences

were observed between the two condensation methods. Microleakage was not influenced either when the restorative resin was inserted immediately after cavity sealing or when the sealant was allowed to set for 30 minutes prior to bulk placement. Finally, no noticeable differences were found in the tested brands of composite resin. Evaluation of marginal adaptation. The results were in logical agreement with the dye penetration data. Perfect adaptation of filling margins was observed in groups 5, 8, and 9. A diagrammatic summary is given in Fig. 6. It is remarkable that polishing procedures improved marginal adaptation in the conventional preparation groups. DISCUSSION The veloped

findings in groups 5, 8, and 9 suggest that a suitable method to improve marginal adaptation and suppress microleakage

has been dein vitro. The

306

Luescher

Fig. 7. (A) region. (C) micrographs;

adhesive

Marginal Overfilled original

restorations

J. Prosthet. March.

et al.

fissure: E, enamel; marginal region. magnification x560.)

were

leakproof,

R, restorative material. (B) (D) Perfect marginal adaptation.

and

a considerable

amount

Underfilled (Scanning

of

sound

Dent. 1977

marginal electron

tooth

could be conserved when preparing the cavity. Esthetic results were excellent. In vivo work with AR restorations revealed additional advantages. Classes II and III adhesive restorations may have a protective effect against caries because the etched enamel surfaces adjacent to the cavity margins are sealed. This may make extension for prevention unnecessary. In a clinical study by Lutz and associates,” the marginal seal obtained by the application of an unfilled resin under composite restorations was effective in adhesive restorations of Classes III and IV cavities for up to 4 years. Polymerization shrinkage is one of the negative properties of resin restorative materials. In modern composite resins, shrinkage has been reduced by 1.5 to 2.1 per cent by volume.ls Shrinkage is always directed toward the center of material bulk; consequently, the loss of volume is adjusted from the periphery and predominantly from the free surfaces. Clinically, 60 per cent of shrinkage can be compensated for when an occlusal load or condensing force is exerted while the material is setting.‘“. I9 As a consequence of shrinkage, marginal spaces or gaps will occur when the contraction force exceeds the adhesive strength of the material to the ename1.l” Gap formation can be enhanced by poor wettability of cavity walls.6l 8 Microleakage was observed even in well-adapted margins of conventional Class II restorations, probably structure

Microleakage

Fig. 8. Enamel/dentin

and

marginal

adaptation

of

restorations

307

shoulder at the proximal part of the adhesive cavity preparation.

because of poor mechanical bonding between composite resin and tooth structure. On the other hand, the results have demonstrated that certain techniques improve composite resin adaptation and inhibit microleakage. Pronounced leakage and poor micromorphologic marginal adaptation were found in group 1: These cavities were filled without etching and sealing. Polymerization shrinkage and inferior wettability might have been responsible for the improper marginal seal. In conventional cavities, neither was dye penetration decreased nor marginal adaptation improved when enamel margins were etched only or beveled before conditioning (Fig. 3)) regardless of whether a sealant was applied or not. However, marginal seal was improved in test groups 1 to 4 by polishing. A possible explanation for this unexpected result may be that after polishing abraded composite resin had entered the gap at the margin, leading to an improved micromorphologic adaptation. The best results in marginal adaptation and resistance to microleakage were obtained when AR cavity preparation was combined with enamel etching and use of a lowviscosity sealant. In these specimens, the interface between enamel and composite resin was barely detectable under the scanning electron microscope (Fig. 7, D) . When cavity sealing was omitted in adhesive restorations, resistance to microleakage and the quality of marginal adaptation markedly deteriorated. In conventional restorations, marginal adaptation was rather poor (Fig. 7, A to C) . In the literature, the use of low-viscosity sealants in connection with composite restorations is highly controversial, especially with respect to their retentive strength. The present study has shown that, under in vitro conditions, sealant application is necessary for a perfect marginal adaptation and minimal microleakage. It is rather improbable that this will not be the case clinically. A certain load must be exerted from the occlusal aspect onto the restorative material during setting in order to condense the material and to counteract polymerization shrinkage and formation of marginal gaps.*O The packing methods used in the present study were equally efficacious. Adaptation and microleakage were not influenced when the sealant was allowed to set for 30 minutes prior to restoration. Nevertheless, it was noted that the set sealant layer was remarkably thicker in these specimens than in cavities restored

308

Luescher

et al.

J. Prosthet.

March.

Dent.

1977

immediately after sealant placement. It has been proposed that only minute amounts of a sealant should be applied because of disturbances originating at the sealantcomposite resin interface due to the differences in physical properties of filled and unfilled resins.*” Also, a thick sealant layer is likely to endanger the esthetic result in anterior restorations. Sealant setting before placement of the restoration offers no advantage. The good results with adhesive restorations probably were due not only to the conditioning of enamel and the use of a low-viscosity sealant but to the new cavity design (AR preparation) which reduced shrinkage because of decreased cavity volume. In addition, the preparation of an elevated enamel/dentin shoulder (Fig. 8) seemed to prevent the overlapping cervical part of the restoration from being drawn away from the cavity margin by polymerization shrinkage. Oversimplification of proximal AR cavity form by the preparation of proximal dents without shoulders (Fig. 8) was associated with pronounced leakage. This was also the case in conventional Class II cavities where shrinkage toward the center probably exceeded the mechanical adhesion even if the bonding enamel surface was widened by beveling (group 4). The adhesive restoration method is being tested in a clinical study. Preliminary findings are encouraging. The relatively low wear resistance of composite resins does not seem to pose problems in AR restorations, owing to the small surface of the restorations which allows the. occlusal and functional contacts to remain on sound enamel surfaces. For similar reasons, the method will fail in advanced dentinal caries or in the replacement of conventional MOD restorations. In such large restorations, the use of composite resin is contraindicated due to its low wear resistance. References 1. Going, R. E.: Microleakage Around Dental Restorations: A Summarizing Review, J. Am. Dent. Assoc. 84: 1349-1356, 1972. 2. Brlnnstr6m, M., and Nyborg, H.: The Presence of Bacteria in Cavities Filled With Silicate Cement and Composite Resin Materials, Sven. Tandlak. Tidskr. 64: 149-155, 197 1. 3. Nelsen, R. J., Wolcott, R. B., and Paffenbarger, G. C.: Fluid Exchange at the Margins of Dental Restorations, J. Am. Dent. Assoc. 44: 288-295, 1952. 4. Letzel, H., Vrijhoef, M. M. A., and Driessens, F. C. M.: Geometric Measurements of Adaptation. Dental Tissues and Materials, International Symposium, Nijmegen, Netherlands, 1970. 5. Bergvall, O., and BrHnnstrijm, M.: Measurements of the Space Between Composite Resin Fillings and the Cavity Walls, Sven. Tandlak. Tidskr. 64: 217-226, 1971. 6. Meurman, J. H., Asikainen, M., and Nevaste, M.: Adaptation of Some Dental Restoratives to Cavity Walls as Observed With the Scanning Electron Microscope, Proc. Finn. Dent. Sot. 71: 36-44, 1975. 7. Tani, Y., and Buonocore, M. G.: Marginal Leakage and Penetration of Basic Fuchsin Dye in Anterior Restorative Materials, J. Am. Dent. Assoc. 78: 542-548, 1969. 8. Sela, M., Sela, J., Arad, T., and Ulmansky, M.: Adaptation of Silicate and Adaptic to the Margins of Cavities. A Scanning Electron Microscope Study, J. Oral Rehabil. 2: 117-124, 1975. 9. Al-Hamadani, K. K., and Crabb, H. S. M.: Marginal Adaptation of Composite Resins, J. Oral Rehabil. 2: 21-33, 1975. 10. Meurman, J. H., and Nevaste, M.: The Intermediate Effect of Low Viscous Fissure Sealants on the Retention of Resin Restoratives in Vitro, Proc. Finn. Dent. Sot. 71: 96101, 1975.

~“ll$; 11. 12. 13. 14. 15.

16. 17. 18. 19. 20.

r

“3’

Microleakage

and

marginal

adaptation

of restorations

309

Strengths of Acid-Etched Retained Mitchem, J. C., and Turner, L. R.: The Retentive Resins, J. Am. Dent. Assoc. 89: 1107-1110, 1974. Rock, W. P.: The Effect of Etching of Human Enamel Upon Bond Strengths With Fissure Sealant Resins, Arch. Oral Biol. 19: 873-877, 1974. Jedrychowski, J., and Reisbick, M. H.: Selection of a Resin System for Anterior Fracture Treatment, J. Dent. Res. 54: 284-289, 1975. Stevens, L.: Retention With Specific and Mechanical Adhesive Lutes, Amt. Dent. J. 20: 112-l 14, 1975. Williams, B., v. Fraunhofer, J. A., and Winter, G. B.: Microleakage in Fissure Sealants as Determined by Dye Penetration and Zero Resistance Current Measurement Studies, Br. Dent. J. 139: 237-241, 1975. Lutz, F., and Burkart, R.: Das Concise-Enamel-Bond-System, eine Alternative? Schweiz. Monatsschr. Zahnheilkd. 84: 1113-l 129, 1974. Lutz, F., Ochsenbein, H., and Liischer, B.: Nachkontrolle von mehrjahrigen AdhlisivFiillungen, Schweiz. Monatsschr. Zahnheilkd. (In press.) Lee, H., and Orlowski, J.: Handbook of Dental Composite Restoratives, South El Monte, Caiif., 1973, Lee Pharmaceuticals. Lee, M., and Orlowski, J.: Adhesive Dental Composite Restoratives, South El Monte, Calif., 1974, Lee Pharmaceuticals. Jacobsen, P. H.: Clinical Aspects of Composite Restorative Materials, Br. Dent. J. 139: 276-280. 1975. DR. LUESCHER THE UNIVERSITY OF CONNECTICUT SCHOOL OF DENTAL MEDICINE FARMINCTON, CONN. 06032

HEALTH

CENTER

DR. LUTZ, OCHSENBEIN, AND M~LEMANN DENTAL INSTITUTE UNIVERSITY OF ZURICH P.O. Box 163 CH 8028 ZURICH, SWITZERLAND

ARTICLES

TO APPEAR IN FUTURE

A new articulator determinants Charles

H. Gibbs,

Vinyl

chloride

Oscar

N. Guerra,

Preparation restoration James

Ph.D.,

emphasis

and Harry

concentrations M.S.P.H.,

D.D.S.,

of endodontically

L. Gutmann,

An evaluation Charles Jerome

with

B. Horton, J. Rudolph,

on

ISSUES centric

occlusion

and

the

anterior

J. Derda

in maxillofacial and Kenneth

treated

prosthetics J. Kronoveter,

teeth

to receive

laboratories M.S.

a post-core

D.D.S.

of commercial D.D.S., D.D.S.,

Helen M.S.D.

pastes for finishing composite resin surfaces M. Paulus, D.M.D., George B. Pelleu, Jr., Ph.D., and