BREEDIN6:WWDDIXON

is used to fabricate the facade, attach the removable partial denture with a cement designed for bonded fixed prostheses (Figs. 12 and 13). REFERENCES 1. McGivney odontics.

GP, Castleberry 8th ed. St Louis:

DJ. McCracken’s CV Mosby,

removable

1989286,

2. Miller EL, Grass0 JE. Removable partial timore: Williams and Wilkins, 1981:67.

partial 238, 127.

prosthodontics.

prosth-

3. Dolder EJ, Durrer GT. The bar-joint Chicago: Quintessence, 1978:40-l. Reprint

requests

denture.

a practical

textbook.

to:

DR. DONNA L. DIXON COLLEGE OF DENTISTRY UNIVERSITY OF IOWA IOWA CITY, IA 52242

2nd ed. Bal-

arginal leakage of class II glass ionomer-composite estorations: An in vitro study Zvia Hirschfeld, DMD,a Akiva Anna Fuks, CDd Hebrew

University-Hadassah

Faculty

Frenkel, DMD,b Daniel Zyskind, DMD,C and of Dental

Medicine,

Jerusalem,

Israel

This in vitro study assessed the sealing properties of two metal-reinforced glass ionomer cements, used as “extended bases” in glass ionomer-composite resin restorations. Two class II cavities were prepared in the proximal surfaces of 30 molars. The gingival margin of one was prepared in enamel and the other in cementum/dentin. Fifteen teeth (30 cavities) were restored with Ketac Silver material used as au extended base (group A). In the remaining 15 teeth (30 cavities), the extended base was in Miracle Mix material (group B). All occlusal surfaces were restored with Estilux Posterior Material. The restored teeth were thermoeycled, immersed in fuchsin, washed in water, embedded, sectioned, and examined under a dissecting microscope. All restorations with margins in cementurn/dentin of group A (Ketac Silver) leaked. No microleakage occurred in 12 of the 30 restorations with margins in cementumldentin of group B (Miracle Mix). In addition, severe microleakage was present in 24 teeth of group A, as opposed to three in group B. It was concluded that the sealing properties of Miracle Mix material are superior to those of Ketac Silver material, in vitro. (J PROSTHET DENT 1992;67:148-53.)

be major disadvantages of conventional glass ionomer cements are low strength and inadequate resistance to wear.‘, 2 Two methods to improve these properties have been introduced. The first consists of adding amalgam alloy powder to the glass ionomer powder to form the socalled miracle mix.3 The second is the result of high heat sintering of metal particles (silver) into the glass to form a “cermet” material.4 The metal-reinforced glass ionomer cement retains the desirable properties of the glass ionomer cement, namely release of fluoride and bonding to tooth structure. Its compressive strength, compressive fatigue limit, and abrasion

BAssociate Professor and Head, Department of Restorative tistry. “Staff member, Department of Restorative Dentistry. CInstructor, Department of Restorative Dentistry. dAssociate Professor, Department of Pedodontics. IO/l/27923 148

Den-

resistance are improved. 5-8 In addition, the setting reaction of the cermet is faster than that of conventional cement.8 Microleakage was observed in class V and tunnel preparations restored with Ketac Silver materiaLg The authors are unaware of any study testing the microleakage of Miracle Mix material. A number of clinical uses bave been proposed for the metal-reinforced glass ionomer cements. These include restorations (class V, small class II, and primary teeth), repair of castings, and temporary or emergency procedures.3, 4 Another suggested indication for their use is as an “extended base,” a partial proximal restoration under a class II composite resin restoration. This modified “samdwith” restoration would combine the esthetic properties of the composite resin, and the bonding properties of the glass ionomer cement to tooth structure, thus solving the problem of microleakage at the gingival margin of posterior composite restorations.lO The aims of this study were (1) to assess the sealing FEBRUARY1992

VOLUME67

NUMBER2

MARGINAL

LEAKAGE

OF RESTORATIONS

properties of two kinds of metal-reinforced glass ionomer cements when used in “sandwich” restorations, with gingival margins in enamel or in cementum/dentin; and (2) to examine the quality of the glass ionomer-posterior composite resin interface. MATERIAL

AND

METHODS

Thirty recently extracted noncarious molars were selected and stored in normal saline until used. The teeth were randomly separated into two groups of 15 teeth each. In group A, the teeth were restored with Ketac Silver material (ESPE-Premier, Norristown, Pa.) as an extended base. In the teeth of the second group (group B), Fuji II Lumi alloy or Miracle Mix material (G-C Dental Industrial Corp., Phoenix, Ariz.) was similarly used. In both groups, the occlusal portion was restored with Estilux Posterior material (Kulzer & Co. Gmbh, Dental Division, Friedrichsdorf, Germany.). Cavity

preparation

and restoration

The teeth were cleaned with an aqueous slurry of pumice by use of a soft polishing brush at low speed and were washed with water. Cylindrical diamond burs in a highspeed water-cooled handpiece were used to prepare two conventional Class II cavities (MO and DO) in each tooth, leaving a sound occlusal wall between them (Fig. 1). The gingival margin of one cavity was prepared in enamel, and the gingival margin of the second one was located in cementum/dentin. After completion of the preparation, the cavities were washed, dried with a stream of air, and conditioned with polyacrylic acid according to the manufacturer’s instructions. Celluloid matrix bands were adapted to the teeth and held in place with a universal Tofflemire matrix retainer (Hawe-Neos Dental, Gentilino, Switzerland). In group A, the teeth were restored with Ketac Silver material as an extended base, completely restoring the proximal portion and lining the occlusal wall. Ketac Silver material was dispensed in premeasured capsules, mixed for 10 seconds in a high-speed amalgamator (G-C Dental Industrial Corp., Phoenix, Ariz.), and syringed into the cavity by the Ketac application system. In group B, Miracle Mix material was used in a similar manner. This material, however, is provided as a Fuji II powder, Lumi alloy, and Fuji II liquid. These materials were mixed according to the manufacturer’s recommendations and inserted into the cavity by use of the Miracle Mix application syringe. The glass ionomer cement and the cavosurface enamel were then etched for 60 seconds with a phosphoric acid gel, washed thoroughly with water, and dried with air. The teeth were then restored with Estilux posterior material, with Scotchbond (3M Co. Dental Products Div., St. Paul, Minn.) used as a bonding agent. The composite resin was applied in increments, and the last one was carved according to the tooth anatomy. The material was light-cured for 40 seconds and the matrix bands were removed. The restorations were polished with abrasive disks (Soflex 3M Co. THE

JOURNAL

OF PROSTHETIC

DENTISTRY

Fig 1. Criteria for assessment of microleakage according to degree of dye penetration. A, Cervical margins placed in enamel. B, Cervical margins placed in cementum/dentin. C, Interface between glass ionomer and composite resin.

Dental Products Div.) and the glass ionomer cement was coated with a varnish. The teeth were stored in water and kept at room temperature for 10 days before thermocycling and immersion in the dye. Thermocyeling

and dye immersion

Both groups were thermocycled 200 times between 4’ 2 2O C and 60” f 2’ C, with dwell times of I minute in each bath and l-minute intervals between them. The teeth were coated with a layer of nail polish, melted utility wax, and a second layer of nail polish. The restorations and surfaces approximately 1 mm beyond the margins were kept free of any coating. The coated teeth were immersed in 2 % basic fuchsin solution for 24 hours. After removal from the dye, the coating was removed and the teeth were thoroughly washed in water, dried, and embedded in acrylic resin. Three mesiodistal sections were obtained by reducing the embedded teeth buccolingually, parallel to their axes. As each third of the restoration was exposed, it was polished under running water, examined, and photographed under a dissecting microscope. Each tooth thus presented three sections for examination and photography: one close to the buccal wall, the second through the center of the restoration, and the third close to the lingual wall. Evaluation

of dye penetration

The depth of dye penetration along the cervical margins of the restoration and at the interface between the glass ionomer cement and the posterior composite resin were evaluated according to standardized systems. 149

~IRS~~FEL~

ET AL

Fig 2. Comparison of severe microleakage at gingival margins in enamel and cementum/ dentin between groups A and B.

I. Assessment dye penetration

Table

of marginal leakage by depth of

Depth of penetration* Cervical margins in dentin (15 teeth)

Cervical margiw in enamel (15 teeth)

Interface (30 teeth)

0 I II III

Ketac Silver (mow A) No. of teeth

Miracle Mix (group W No. of teeth

0 0 0 3

6 1 2 3

IV

7

V

5

2 1

0 I II III IV V VI

1 1 1 0 1 3 8

10 4 1

0 1 2 3

15 2 1

11 9

12

0 0 0 0

4 6

*See text for key to ratings.

The criteria for evaluation of the cervical margins in enamel were as follows (Fig. I, A): 0 = No dye penetration I = Penetration of dye into enamel only II = Penetration of dye into the first third of the proximal portion beyond the dentinoenamel junction III = Penetration of the dye into the second third of the proximal portion beyond the dentinoenamel junction IV = Penetration of dye to the gingivoaxial line angle V = Penetration of dye to the pulpoaxial line angle VI = Penetration of dye beyond the pulpoaxial line angle I50

3. Modified “sandwich” restorations using Ketac Silver and Estilux Posterior materials. Cervical wall in enamel(a) and cementum/dentin (b). Severemicroleakage is seen at cementum/dentin margin (degree IV) and at enamel margin (degree VI). No microleakage is seen at glassionomer-composite resin interface (c).

Fig

ScoresI to IV wereconsideredmildmicroleakagewhereas V and VI were rated as severe. The criteria for evaluation of the cervical margins in cementum/dentin were asfollows (Fig. 1, B): 0 = No penetration of dye I = Penetration of dye into the first third of the mesiodistal depth of the proximal portion II = Penetration of dye including two thirds of the mesiodistal depth of the proximal portion. III = Penetration of dye to the gingivoaxial line angle IV = Penetration of dye into the pulpoaxial line angle V = Penetration of dye beyond the pulpoaxial line angle

ScoresI to III wererated asmild microleakageand scores IV and V as severe. The degreeof dye penetration at the interface between FEBRUARY

1992

VOLUME

67

NUMBER

2

~~ARG~~AL

LEAKAGE

OF RESTORATIONS

4. “Sandwich” restorations using Miracle Mix and Estilux Posterior materials. Minimal leakage(degreeII) at the cementum/dentin margin (b). No leakageat the cavosurface enamelgingival margin (a). Air spacesare noted in the Miracle Mix material (c). Fig

Fig

5. Ketac Silver and Estilux

Posterior

material

resto-

rations with minimal leakage(degreeII) at the cementum/ dentin margin (b) and no leakage at the enamel gingival margin (a).

the glassionomer cement and the compositeresin wasassessedas follows: (Fig. 1, C) 0 = No dyepenetration 1 = Penetrationof dye up to the middle of the mesiodistal depth of the proximal portion (mild microleakage) 2 = Penetration of the dye to the level of the pulpoaxial line angle (mild microleakage) 3 = Penetration of the dye beyond the level of the pulpoaxial line angle (severe microleakage)

The highest degreeof dye penetration observedin one of the three sectionsexamined wastaken asthe final scoreof the margin examined.

RESULTS The degreeof microleakageof the different restorations assessed is summarizedin Table I. Fig. 2 graphs the severity of microleakage. Considerabledifferenceswere observedin restorationsof the two groups when the cervical margins were placed in cementum/dentin. All of the restorations in group A (Ketat Silver) leaked, whereasno microleakage(score = 0) occurred in six teeth of group B (Miracle Mix). Mild microleakage (scoresI to III) was evident in six teeth of group B and three teeth of group A. In addition, severemicroleakageat the cementum/dentin gingival margin (scoresIV and V) was present in 12 teeth of group A, as opposedto only three teeth in group . The differences were even more pronounced in the restorations with the gingival margins in enamel. Only one tooth of group A showedno dye penetration (degree0), asopposedto 10 teeth in group B, at the gingival margin in enamel. Mild microleakage (scoresI to IV) was present in three teeth of group A and in five teeth of group B. Severe microleakage (scores V and VI) was evident in I1 teeth in group A, none of the teeth in group B showed high scores. THE

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6. Miracle Mix and Estilux Posterior materials with excellent sealat the cervical margins (a). No dye penetration. Note cracks in the Miracle Mix material (b). Fig

The differences

in dye penetration

at the glass ionomer-

compositeresin interface were not statistically significant. Severe microleakage(score3) wasobserved in three teeth in group A and six teeth in group B. Mild microleakage (score1 and 2) wasfound in three of the interfaces in group A and 13 teeth in group B. In addition, 15 teeth in group A showedno penetration of dye at the interface of the two materials, as opposedto 11 teeth in group B. Representative restorations of both groups are presented in Figs. 3 through 6. The severemicroleakagedata were subjectedto statistical analysisby t-test. A significant difference (p < 0.01)was observedbetween groupsA and B at the gingival margins. A significant difference (p < 0.05) wasobservedin group B between restorations with gingival margins placed in enamel and restorations with gingival margins in cementurn/dentin.

No significant

differences

at the interface

were

observedbetweenthe two groupsor in group A betweenthe restorations with gingival margins placed in enamel and those in cementumldentin. 151

~IR$~~FELD

The results of the present experiment confirm earlier studies demonstrating that the sealing qualities of Ketac Silver Material are Iow.~, l1 Robbins and Cooleyg reported that microleakage was observed in an in vitro study of tunnel preparations and class V restorations with Ketac Silver material. Guelmann et aLI1 compared microleakage of class II restorations in primary teeth using the glass ionomer cermet Ketac Silver with composite coverage. Severe leakage was observed at the cervical margins of all the restorations. The comparison between Ketac Silver and Miracle Mix materials showed clearly that, in vitro, the sealing qualities of Ketac Silver material were inferior to those of Miracle Mix material. The differences were more pronounced in restorations with cervical margins in enamel, but were still significant in restorations with cervical margins in cementurn/dentin. Gwinne@ demonstrated that in the cervical area of teeth, where enamel prisms do not extend to the surface, etch patterns are characterized by surface loss without exposure of underlining prisms. He found a better etch pattern on surfaces perpendicular to the prism direction than on surfaces parallel to the prisms. Greater leakage was found at the cervical margins of composite restorations in primary teeth when compared with that in permanent teetb.‘3-15The difference could possibly be attributed to prism direction between the two types of teeth, or to the presence of greater enamel thickness at the gingival margins in permanent teeth. These factors may also play a role in the superior adaptation of glass ionomer cements to enamel than to the cementumjdentin margin for both materials tested in the present study. Similar to the findings of Guelmann et al.,ll microleakage was evident in the present report at the cementum/dentin margins restored with Ketac Silver material, but almost half of the teeth restored with Miracle Mix material did not leak in these areas. It would be interesting to observe the adhesion of this material in primary teeth. The poorer performance of Ketac Silver material compared with Miracle Mix material in the present study could be attributed to weaker bonding properties of Ketac Silver material to dentin or to its inadequate resistance to thermocycling. It is difficult to find a precise explanation for the presence of severe microleakage in three Miracle Mix material restorations. NO significant differences were observed in the adaptation of both glass ionomer cements to the composite resin, and leakage occurred at the interface of the restorations in both groups. At the time this study was done, the recommended etching time of the glass ionomer extended base was 1 minute. Recent findings, however, point to the possibility that this etching time results in small, weak, and soluble glass ionomer particles. Presently, the recommended etching time is limited to 25 seconds. The result-

152

ET AL

ing particles are larger and stronger, with a low solubility rate and probably with better sealing properties. It is POSsible that the l-minute etching time used in this study is the reason for the observed leakage at the interface in both groups.*

CONCLUSIONS The results in the present investigation show the following. 1. Sealing of Miracle Mix material at enamel and cementurn/dentin margins was superior to that of Ketac Silver material. 2. There was no significant difference in microleakage at the glass ionomer-composite resin interface between Ketac Silver and Miracle Mix materials. 3. Higher levels of microleakage occurred at gingival margins in cementum/dentin than in enamel. In vitro studies do not reproduce exactly the conditions present in the oral cavity. Hence, extrapolation of in vitro experiments to in vivo conditions should be made with reservation. We wish to mention the late Prof. R. Grajower, Head of the Dental Materials Laboratory, with gratitude, for his invaluable assistance in evaluating the project’s results.

REFERENCES 1. Fuks AB, Shapira J, Bielak S. Clinical evaluation of glass ionomer cement used as class II restorative material in primary molars. J Pedod 1984;8:393-9. 2. McKinney JE, Antonucci JM, Rupp NW. Wear and microhardness of ionomer cements [Abstract]. J Dent Res 1985;64(special issue): 371. 3. Simmons JJ. The miracle mixture: glass ionomer and alloy powder. Tex Dent J 1983;100:6-12. 4. McLean JW, Gasser 0. Glass cermet cements. Quintessence Int 1985;16:333-43. 5. Thornton JB, Retief DH, Bradley EL. Fluoride release from and tensile bond strength of Ketac-fil and Ketac-silver to enamel and dentine. Dent Mater 1986;2:241-5. 6. Tjan HL, Morgan DL. Metal-reinforced glass ionomers: their flexual and bond strengths to tooth substrates. J PROSTHET DENT 1988;59:13741. 7. Marker VA, Ferracane JL, Miller D, et al. Characterization of metal-reinforced glass ionomer restorative materials [Abstract]. J Dent Res 1985;64(special issue):297. 8. Walls A W G, Adamson J, McCabe JF, Murray JJ. The properties of a glass polyalkenoate (ionomer) cement incorporating sintered metallic particles. Dent Mater 1987;3:113-6. 9. Robbins JW, Cooley RL. Microleakage of Ketac-Silver in the tunnel preparation. Oper Dent 1988;13:8-11. 10. Donovan TE, Daftary F. Clinical use of glass ionomer restorative materials. Compend Contin Educ Dent 1987;8:180-90. 11. Guelmann M, Fuks AB, Grajover R, Holan G. Marginal leakage of class II glass ionomer-silver restorations with and without a posterior composite coverage [Abstract]. J Dent Res 1988;67:‘714. 12. Gwinnet AJ. Human prismless enamel and its influence on sealant penetration. Arch Oral Biol 1973;18:441-4. 13. Fisbein S, Holan G, Grajower R, Fuks AB. The effect of VLC Scotch-

*Christensen 1988.

6. Dentistry update course, Tel Aviv, Israel, June

FEBRUARY

X992

VOLUME

67

NUMRER

2

Reprint

bond and au incremental filling technique on leakage around class II composite restorations. J Dent Child 1988;55:29-33. 14. Holan G, Fuks AB, Grajower R, Chosack A. In vitro assessment of the effect of Scot&bond on the marginal leakage of class II composite restorations in primary molars. J Dent Child 1986;53:188-92. 15. Fuks AB, Grajower R, Koenigsberg S. Filling techniques for posterior composites [Abstract]. J Dent Res 1988;67:712.

akage

between

A. A. Suliman,a

BDS,

MS,

University

College

of Dentistry,

of Iowa,

and

K.

C. Chan,b City,

DDS,

to:

P.O. Box 1172 JERUSALEM ISRAEL

different Iowa

requests

DR. ZVIA HIRSCHFELD HEBREWUNIVERSITY-HADASSAHFACULTYQFDENTALMEDICINE

types of base materia MS

Iowa

This study investigated the sealing properties of various combinations of base materials. Three chemically cured and three light-activated base materials were eombinationally used to make 15 sample groups. The samples were thermocycled and immersed in 0.05% crystal violet solution for 1 hour. They were then embedded in clear casting resin, sectioned, and photographed. The interfaces of the samples were digitized. The ratio of the total interface length to the penetration of leakage was calculated and compared. The results indicated that the combination of Cavalite and VLC Dycal materials had the least microleakage and was significantly d.ifferent from the other 14 groups. (J PROSTHET DENT 1992;67:153-6.)

n dental practice, it is uncommon that the cavity must be extended beyond ideal to completely remove decay. Dependent on the depth of the cavity, different types of base materials can be used to protect the health of the dental pulp. It is believed that zinc oxide and eugenol provide sedation to an inflamed pulp1 and calcium hydroxide stimulates the formation of irregular secondary dentin.” Although these materials are still used, there are many new base materials such as glass ionomers and light-activated base materials. Because of the fluoride-releasing effect of the glass ionomers and the short working time of the light-activated materials, their use has become popular. In the normal situation, when the cavity is slightly deeper than ideal, the use of a single type of base material is sufficient to protect the pulp. When the cavity is de’ep, a combination of base materials is recommended.3, 4 Pashley et aL5 and Cox et aL6 stated that microleakage of restorations allows bacteria and bacterial toxins to enter a cavity preparation through the margins and irritate the pulp causing postoperative sensitivity. The sealing property of the base material placed beneath the restoration is important to the health of the pulp.

aPhD candidate, Biomedical Engineering/Operative bProfessor, Operative Dentistry. 10/1/29633

THE JOURNAL

OF PROSTHETIC

DENTISTRY

Dentistry.

The sealing property of base materials to dentin have been studied, but microleakage between basing materials has not been examined. This study investigated microleakage between different types of base materials. MATERIAL

AND

METHODS

A split Plexiglass (Rohm and Haas Co., Philadelphia, Pa.) mold was made with five cylindrical holes with a diameter of 3 mm and a depth of 4 mm. Six base materials were used. Life (Kerr, Romulus, Mich.), Cavitec (Kerr), and Ketac Bond (ESPE-Premier, Norristown, Pa.) were chemically cured. VLC Dycal (Caulk, Milford, Del.), TimeLine (Caulk), and Cavalite (Kerr) were light-activated. Fifteen groups of specimens with five samples for each group were prepared (Table I). The samples were prepared by placing one material in the hole of the mold to a height of approximately 2 mm and allowing it to set in air for 24 hours. Another material was then placed on top of the set material to the level of the surface of the mold. All of the chemically cured materials were mixed according to the manufacturer’s instructions and all of the light-activated materials were polymerized with a Visilux Curing Light unit (3M, St. Paul, Minn.) for 60 seconds. The prepared samples were removed from the mold and stored in 100% relative humidity at room temperature for 24 hours. The samples were thermocycled in water between 3” C and 60” C for 180 cycles with a dwell time of 30 seconds. The samples were then immersed in 0.05% crystal violet solution

153