Journal of Oral Rehabilitation,
1975, Volume 2, pages 117-124
Adaptation of silicate and Adaptic to the margins of cavities A scanning electron microscope stndy
M. SELA, J. SELA, T. ARAD and M. ULMANSKY Oral Medicine and Pathology, The Hebrew Universitv-Hadassah Medicine and Hadassah Medical School, Jerusalem, Israel
Departments of School of Dental
Summary The effects of etching of the enamel, on the adaptation of silicate and Adaptic to the cavity walls was examined with the scanning electron microscope. Replica methods were utilized to ensure that no shrinkage of the filling materials was caused by the vacuum in the instrument. Tt was shown that following etching of the cavity margins, Adaptic adhered to the enamel with absent, or minimal, fissure formation on one side of the filling, and some on the opposite side. The adaptation of silicate to the margins of the cavities was not improved by etching. Introduction Adaptic,* a composite dental filling material, has been studied to find out its physical and chemical properties in vitro and in vivo (Lee & Swartz, 1970; McLutidie & Murray, 1972; Liatukas, 1972). The material is composed of a resin matrix and an inorganic filler, the latter serving to reduce shrinkage at the stage of polymerization and provide a closer marginal adaptation (Lee & Swartz, 1970). Studies on the marginal fillingcavity relationship with the scanning electron microscope (SEM) revealed an average fissure of 0-5 ^m between the material and the cavity wall. For silicate fillings these gaps were found to be of 3 jxva in width (Lee & Swartz, 1970). An attempt to overcome this disadvantage was made with the introduction of etching techniques. It has been postulated that pretreatment of enamel at the cavity margins with 50% phosphoric acid increases the strength of the attachment of composite filling material to the tooth. Acid etching of normal enamel produces a subsurface with typical prismatic appearance (Johnson, Poole & Tyler, 1971). It has been suggested also that etching Improves adaptation and retention of restorative materials (Buonocore, 1955; Sharp & Grenoble, 1971; Retief, 1973). The purpose of the present work was to study the effects of etching of the enamel on the adaptation qualities of Adaptic as compared to silicate. Materials and methods Twenty sound permanent third molars were used in the present study. After extraction, the crowns were removed and stored in cold physiological saline. Eaeh crown was * Adaptic—Johnson and Johnson, New Brunswick, N.J., U.S.A. Corre.spondence: Dr J. Sela, Department of Pathology. The Hebrew University-Hadassah Medical School, P.O.B. 1172, Jerusalem, Israel.
117
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M. Sela Qtal
sectioned longitudinally into two halves in a mesiodistal plane with a water cooled carborundum disc. Two class five cavities were prepared in each of the resulting forty specimens, with a high speed water cooled inverted cone diamond burr. The cavities were 2-3 mm in diameter and depth. Eorty cavities in twenty of the specimens were then etched with 50% phosphoric acid,* which was applied to the cavity borders for 1 min by means of a cotton pellet and then removed with tap water. The cavities were then dried by air stream, and the right one in each specimen was fviled with Adaptic, while the left ones with a synthetic porcelain.t A cellophane strip was firmly maintained on the surfaces of the fillings until completion of setting. They were then covered with white soft paraffin and polished with rotating fine sandpaper discs to eliminate overflow material: fine polishing was achieved by a rotatory white rubber cap. Einally, the specimens were washed with soap using a soft brush. All the materials were handled according lo the manufacturers instructions. Table I.. Experimental design Fillings Specimens
Ci1 vities
Adaptic
Silicate
Replica specimens
Etching of cavities
20
40
20
20
20
Non etc hing of cavities
20
40
20
20
20
Experimental design. (Table I), the forty specimens were divided into two experimental groups; the first, including twenty specimens with non etched cavities, each specimen having two fillings, one of Adaptic and the other of silicate. The second group was designed in a similar way, the only difference being that the cavities underwent etching. Twenty specimens of both groups were taken at random for preparation of copies by a replica method (Pameijer & Stallard, 1973). Briefly, replication solution was applied to the surfaces of the specimens, then covered by the replicating tape whieh was pressed moderately until drying; after separation of the tape, this was filled with a dental impression.+ Ail specimens and replica models were maintained in saline until they were gold coated in a vacuum evaporator using a rotatory jig,§ and examined with the SEM.^I After examination, the specimens were cut transversely through the fillings, coated again and examined as well. Results A thorough macroscopical examination of the fillings, immediately after polishing did not reveal any particular imperfections. In some instances, specially in Adaptie fillings it was difficult to distinguish the borderline between the filling material and the enamel. However, examination of the filling margins with an optical stereomicroscope (x5 and X 10) revealed marginal gaps. Eurther examination of the specimens with the SEM at low magnifications (x22 and x24) disclosed elear eut fissures between the fillings and the cavity walls. * Liquid for zinc cement improved S.S. White Co. Philadelphia, Pa., U.S.A. t Porcelain filling material S.S. White Co. Philadelphia, Pa., U.S.A. 5 Xantropren, light body Bayer Co., W. Germany. § Microprep 300 coating Unit, Nanotech Ltd, Urmston, Lancashire, England. TJS4-I0 Stereoscan Cambridge Instrument Co. Ltd, Cambridge, England.
Marginat adaptation of siticate and A daptic
Fig. 1. Silicate (s) and Adaptic (A) fillings in non-etched cavities (x 24).
ig. 2. Sflicate (s) and Adaplic (AJ fitting in etched cavtjies ( x 22).
119
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M. Sela et al.
Fig. 3. A silicate filling in a non-etched cavity, transversely sectioned, (B, cavity bottom) (x 22).
;. 4. A silicate filling (s) in an etched cavity { x 60).
Marginat adaplation of siticate and Adaptic
Fig. 5. Replicate of the area in Fig. 4 (x 60).
I'ig. 6. Highet magnification of a siiicate fiiiing (s) in an etched eavity (x 1200). 9
121
122
M.
Fig. 7. Replicate of Ihe area in Fig. 6 (x 1200).
Fig. 8. An Adaptic tilling (A) in etched cavity, note particles of Adaplic attached to the caviiy v opposite to imprints in the filling material (arrows) ( x 1200).
Marginal adaptation of silicate and Adaptic 123 All the synthetic porcelain fillings were found to have extensive peripheral fissures (Figs 1 and 2), the formation of which was not prevented by the etching technique. Transverse sections of the porcelain fillings showed similar fissures ail along the cavity walls and bases (Fig. 3). These fissures were also found to be present in the corresponding replica specimens (Figs 4-7). Marginal imperfections in Adaptic fillings could only be identified with SEM higher magnifications. These consisted of narrow fissures between the material and the enamel. However, these gaps were different for the etched as compared with the non-etched cavities. In the latter, the marginal separation was irregular in width and shape, the fissures being narrower and wider along the total circumference of the same filling (Figs 1 and 2). Peripheral fissures around Adaptic fillings in etched cavities revealed a special characteristic, while on one side of the filling no gaps were found, on the opposite side a widefissureexisted. In these instances particles of Adaptic were found to be attached to the cavity wall, while on the filling side of the fissures, imprints of these particles could clearly be seen (Fig. 8). Cross cut sections of the Adaptic fillings confirmed similar filling-cavity relationships. Discussion
The above findings are in agreement wiih the results of recent studies which proved the existence offissuresbetween silicate fillings and the cavity walls (Lee & Swartz, 1970). The present work has in addition proved that etching of the cavity walls does not result in higher adaptability of the silicate filling to the cavity margins. On the other hand, Adaptic has shown a better marginal adaptation as compared with silicate. The marginal adaptation of Adaptic, the composite material used in the present work, has been examined in the past by methods such as isotope leakage and scanning electron microscopy. In cotnparison with other restorative materials it was found to give a closer cavity and marginal adaptation (Lee & Swartz, 1970). The findings reported here confirmed these results. The possibility of shrinkage of the composite material during technical processing was taken into consideration and replica methods were used so far, in order to control the possibility of artifacts. It was observed that fissures between the filling material and the cavity wall were identical to those obtained with the replica method, a characteristic which is not in full agreement with previous studies of Bergvall & Brannstrom (1971). The differences between the width of the fissures in the replicas and those of the original specimens, observed with light microscope by Bergvall & Brannstrom (1971), may be due to technical artifacts produced by their replication method, which was different from ours. This idea is strengthened especially in view of the identity between the original specimen and the replicas, as shown in the present study. Etching of the enamel seems to result in a better marginal bonding and retention of composite materials (Buonocore, 1955; Groper, 1971). The findings give only partial support (o these lasl observations in that the Adaptic adheres to the cavity walls in such a way, that fissure formation is minimal or does not exist on one side of the filling while it is wider than usual on the opposite side. This is probably the result of stronger bonding of the composite material to part of the periphery of the etched cavity than to the opposite side. With shrinkage, the side of the stronger bonds acts as an anchor and the filling material is drawn away from the opposite side resulting in a fissure.
124
M. Sela tial
References BERGVALL, O. & BRANNSTROM, M. (1971) Measurements of the space between composite resin fillings and the cavity walls. Swedish Dental Journal, 64, 217. BuoNocoRK, M.G. (1955) A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. Journal of Dental Research, 34, 849. GROPER, J.N. (1971) The etch technique for anterior tooth restorations. Journal of Southern California Dental Association, 39, 756. JOHNSON, N.W., POOLE, D.F.G. & TYLER, J.E. (1971) Factors afFecting the differential dissolution of human enamel in acid and EDTA. A scanning electron microscope study. Archives of Oral Biology, 16, 385. LEE, H.L. & SWARTZ, M.L. (1970) Scanning electron microscope study of composite restorative materials. Journal of Dental Research, 49, 149. LiATUKAS, E.L. (1972) A clinical investigation of composite resin restorations in anterior teeth. Journal of Prosthetic Dentistry, 11, 616. McLuNDiE, A.C. & MURRAY, F.D. (1972) Silicate cements and composite resins—A scanning electron microscope study. Journal of Prosthelic Dentistry, 27, 544. PAMEIJER, C.H. & STALLARU, R.E. (1973) Three replica techniques for biological specimen preparation, scanning electron microscopy ( part HI). Proceedings of the Workshop on Scanning Electron Microscopy in Pathology, p. 357. IIT Research Institute, Chicago. RETIEF, D.H. (1973) Effect of conditioning the enamel surface with phosphoric acid. Journal of Denial Research, 52, 333. SHARP, E.C. & GRENOBLE, D.E. (1971) Dental resin penetration into acid etched subsurface enamel. Journal of Southern California Dental Association, 39, 741.
Manuscript accepted 24 August 1974
1975, Volume 2, pages 117-124
Adaptation of silicate and Adaptic to the margins of cavities A scanning electron microscope stndy
M. SELA, J. SELA, T. ARAD and M. ULMANSKY Oral Medicine and Pathology, The Hebrew Universitv-Hadassah Medicine and Hadassah Medical School, Jerusalem, Israel
Departments of School of Dental
Summary The effects of etching of the enamel, on the adaptation of silicate and Adaptic to the cavity walls was examined with the scanning electron microscope. Replica methods were utilized to ensure that no shrinkage of the filling materials was caused by the vacuum in the instrument. Tt was shown that following etching of the cavity margins, Adaptic adhered to the enamel with absent, or minimal, fissure formation on one side of the filling, and some on the opposite side. The adaptation of silicate to the margins of the cavities was not improved by etching. Introduction Adaptic,* a composite dental filling material, has been studied to find out its physical and chemical properties in vitro and in vivo (Lee & Swartz, 1970; McLutidie & Murray, 1972; Liatukas, 1972). The material is composed of a resin matrix and an inorganic filler, the latter serving to reduce shrinkage at the stage of polymerization and provide a closer marginal adaptation (Lee & Swartz, 1970). Studies on the marginal fillingcavity relationship with the scanning electron microscope (SEM) revealed an average fissure of 0-5 ^m between the material and the cavity wall. For silicate fillings these gaps were found to be of 3 jxva in width (Lee & Swartz, 1970). An attempt to overcome this disadvantage was made with the introduction of etching techniques. It has been postulated that pretreatment of enamel at the cavity margins with 50% phosphoric acid increases the strength of the attachment of composite filling material to the tooth. Acid etching of normal enamel produces a subsurface with typical prismatic appearance (Johnson, Poole & Tyler, 1971). It has been suggested also that etching Improves adaptation and retention of restorative materials (Buonocore, 1955; Sharp & Grenoble, 1971; Retief, 1973). The purpose of the present work was to study the effects of etching of the enamel on the adaptation qualities of Adaptic as compared to silicate. Materials and methods Twenty sound permanent third molars were used in the present study. After extraction, the crowns were removed and stored in cold physiological saline. Eaeh crown was * Adaptic—Johnson and Johnson, New Brunswick, N.J., U.S.A. Corre.spondence: Dr J. Sela, Department of Pathology. The Hebrew University-Hadassah Medical School, P.O.B. 1172, Jerusalem, Israel.
117
118
M. Sela Qtal
sectioned longitudinally into two halves in a mesiodistal plane with a water cooled carborundum disc. Two class five cavities were prepared in each of the resulting forty specimens, with a high speed water cooled inverted cone diamond burr. The cavities were 2-3 mm in diameter and depth. Eorty cavities in twenty of the specimens were then etched with 50% phosphoric acid,* which was applied to the cavity borders for 1 min by means of a cotton pellet and then removed with tap water. The cavities were then dried by air stream, and the right one in each specimen was fviled with Adaptic, while the left ones with a synthetic porcelain.t A cellophane strip was firmly maintained on the surfaces of the fillings until completion of setting. They were then covered with white soft paraffin and polished with rotating fine sandpaper discs to eliminate overflow material: fine polishing was achieved by a rotatory white rubber cap. Einally, the specimens were washed with soap using a soft brush. All the materials were handled according lo the manufacturers instructions. Table I.. Experimental design Fillings Specimens
Ci1 vities
Adaptic
Silicate
Replica specimens
Etching of cavities
20
40
20
20
20
Non etc hing of cavities
20
40
20
20
20
Experimental design. (Table I), the forty specimens were divided into two experimental groups; the first, including twenty specimens with non etched cavities, each specimen having two fillings, one of Adaptic and the other of silicate. The second group was designed in a similar way, the only difference being that the cavities underwent etching. Twenty specimens of both groups were taken at random for preparation of copies by a replica method (Pameijer & Stallard, 1973). Briefly, replication solution was applied to the surfaces of the specimens, then covered by the replicating tape whieh was pressed moderately until drying; after separation of the tape, this was filled with a dental impression.+ Ail specimens and replica models were maintained in saline until they were gold coated in a vacuum evaporator using a rotatory jig,§ and examined with the SEM.^I After examination, the specimens were cut transversely through the fillings, coated again and examined as well. Results A thorough macroscopical examination of the fillings, immediately after polishing did not reveal any particular imperfections. In some instances, specially in Adaptie fillings it was difficult to distinguish the borderline between the filling material and the enamel. However, examination of the filling margins with an optical stereomicroscope (x5 and X 10) revealed marginal gaps. Eurther examination of the specimens with the SEM at low magnifications (x22 and x24) disclosed elear eut fissures between the fillings and the cavity walls. * Liquid for zinc cement improved S.S. White Co. Philadelphia, Pa., U.S.A. t Porcelain filling material S.S. White Co. Philadelphia, Pa., U.S.A. 5 Xantropren, light body Bayer Co., W. Germany. § Microprep 300 coating Unit, Nanotech Ltd, Urmston, Lancashire, England. TJS4-I0 Stereoscan Cambridge Instrument Co. Ltd, Cambridge, England.
Marginat adaptation of siticate and A daptic
Fig. 1. Silicate (s) and Adaptic (A) fillings in non-etched cavities (x 24).
ig. 2. Sflicate (s) and Adaplic (AJ fitting in etched cavtjies ( x 22).
119
120
M. Sela et al.
Fig. 3. A silicate filling in a non-etched cavity, transversely sectioned, (B, cavity bottom) (x 22).
;. 4. A silicate filling (s) in an etched cavity { x 60).
Marginat adaplation of siticate and Adaptic
Fig. 5. Replicate of the area in Fig. 4 (x 60).
I'ig. 6. Highet magnification of a siiicate fiiiing (s) in an etched eavity (x 1200). 9
121
122
M.
Fig. 7. Replicate of Ihe area in Fig. 6 (x 1200).
Fig. 8. An Adaptic tilling (A) in etched cavity, note particles of Adaplic attached to the caviiy v opposite to imprints in the filling material (arrows) ( x 1200).
Marginal adaptation of silicate and Adaptic 123 All the synthetic porcelain fillings were found to have extensive peripheral fissures (Figs 1 and 2), the formation of which was not prevented by the etching technique. Transverse sections of the porcelain fillings showed similar fissures ail along the cavity walls and bases (Fig. 3). These fissures were also found to be present in the corresponding replica specimens (Figs 4-7). Marginal imperfections in Adaptic fillings could only be identified with SEM higher magnifications. These consisted of narrow fissures between the material and the enamel. However, these gaps were different for the etched as compared with the non-etched cavities. In the latter, the marginal separation was irregular in width and shape, the fissures being narrower and wider along the total circumference of the same filling (Figs 1 and 2). Peripheral fissures around Adaptic fillings in etched cavities revealed a special characteristic, while on one side of the filling no gaps were found, on the opposite side a widefissureexisted. In these instances particles of Adaptic were found to be attached to the cavity wall, while on the filling side of the fissures, imprints of these particles could clearly be seen (Fig. 8). Cross cut sections of the Adaptic fillings confirmed similar filling-cavity relationships. Discussion
The above findings are in agreement wiih the results of recent studies which proved the existence offissuresbetween silicate fillings and the cavity walls (Lee & Swartz, 1970). The present work has in addition proved that etching of the cavity walls does not result in higher adaptability of the silicate filling to the cavity margins. On the other hand, Adaptic has shown a better marginal adaptation as compared with silicate. The marginal adaptation of Adaptic, the composite material used in the present work, has been examined in the past by methods such as isotope leakage and scanning electron microscopy. In cotnparison with other restorative materials it was found to give a closer cavity and marginal adaptation (Lee & Swartz, 1970). The findings reported here confirmed these results. The possibility of shrinkage of the composite material during technical processing was taken into consideration and replica methods were used so far, in order to control the possibility of artifacts. It was observed that fissures between the filling material and the cavity wall were identical to those obtained with the replica method, a characteristic which is not in full agreement with previous studies of Bergvall & Brannstrom (1971). The differences between the width of the fissures in the replicas and those of the original specimens, observed with light microscope by Bergvall & Brannstrom (1971), may be due to technical artifacts produced by their replication method, which was different from ours. This idea is strengthened especially in view of the identity between the original specimen and the replicas, as shown in the present study. Etching of the enamel seems to result in a better marginal bonding and retention of composite materials (Buonocore, 1955; Groper, 1971). The findings give only partial support (o these lasl observations in that the Adaptic adheres to the cavity walls in such a way, that fissure formation is minimal or does not exist on one side of the filling while it is wider than usual on the opposite side. This is probably the result of stronger bonding of the composite material to part of the periphery of the etched cavity than to the opposite side. With shrinkage, the side of the stronger bonds acts as an anchor and the filling material is drawn away from the opposite side resulting in a fissure.
124
M. Sela tial
References BERGVALL, O. & BRANNSTROM, M. (1971) Measurements of the space between composite resin fillings and the cavity walls. Swedish Dental Journal, 64, 217. BuoNocoRK, M.G. (1955) A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. Journal of Dental Research, 34, 849. GROPER, J.N. (1971) The etch technique for anterior tooth restorations. Journal of Southern California Dental Association, 39, 756. JOHNSON, N.W., POOLE, D.F.G. & TYLER, J.E. (1971) Factors afFecting the differential dissolution of human enamel in acid and EDTA. A scanning electron microscope study. Archives of Oral Biology, 16, 385. LEE, H.L. & SWARTZ, M.L. (1970) Scanning electron microscope study of composite restorative materials. Journal of Dental Research, 49, 149. LiATUKAS, E.L. (1972) A clinical investigation of composite resin restorations in anterior teeth. Journal of Prosthetic Dentistry, 11, 616. McLuNDiE, A.C. & MURRAY, F.D. (1972) Silicate cements and composite resins—A scanning electron microscope study. Journal of Prosthelic Dentistry, 27, 544. PAMEIJER, C.H. & STALLARU, R.E. (1973) Three replica techniques for biological specimen preparation, scanning electron microscopy ( part HI). Proceedings of the Workshop on Scanning Electron Microscopy in Pathology, p. 357. IIT Research Institute, Chicago. RETIEF, D.H. (1973) Effect of conditioning the enamel surface with phosphoric acid. Journal of Denial Research, 52, 333. SHARP, E.C. & GRENOBLE, D.E. (1971) Dental resin penetration into acid etched subsurface enamel. Journal of Southern California Dental Association, 39, 741.
Manuscript accepted 24 August 1974
