MATERIALS AND
Ultrastructural Gingival
Two types of preparations were realized on the perio dontal tissues of four beagle dogs. The animals were anesthetized with Nembutal. No local anesthetic was used. All teeth were cleaned and polished according to standard dental prophylactic procedures. The gingiva of the buccal surface of maxillary and mandibular cuspids, bicuspids and first molars was elevated with a full thickness flap and revealing incisions were made in order to expose the root surface and bone margin. In a first series of experiments, after elevation of the flap, the tooth surfaces were pumiced, washed and dried. They were then etched with 50% phosphoric acid for 2 minutes. A pure gold strip 2/100 mm thick was bur nished on the root surface as close to the bone margin as possible and bonded with cyanoacrylate. In a second series of experiments, class V preparations were made across enamel and cementum and were filled with gold foil restorations. Special care was taken in the condensation of the gold cylinders and in the polishing of the surface. In both series the flap was then sutured back in position. Pressure was applied with a sponge and saline solution for 3 minutes. During the whole experimental period, the dogs received a regular diet composed of canned meat and rice. They were not submitted to any special oral hygiene procedure. After 3 weeks, the animals were sacrificed and the marginal periodontal tissues together with bone and dental tissues were removed according to the technic described by Rebstein. After fixation in a 2% phosphate buffered glutaraldehyde solution for 1 hour followed by a 1 hour postfixation in a 2% osmic acid solution in the same buffer, the specimens were embedded in Epon. Nondecalcified thin sections were made with a ServallPorter microtome equipped with a diamond knife. With this latter, the inserted gold strip and the gold foil restorations could be easily sectioned. After uranyl acetate and lead citrate stainings, the observations were made in a Philips EM 200 and in a Jeol 100 B electron microscope.
Reactions to Gold Foil Restorations by ROBERT M . FRANK* MONIQUE BRION† MlCHÉeLE D E ROUFFIGNAC‡ GINGIVAL REACTIONS to dental materials have been studied with the light microscope and contradictory results were obtained. Waerhaug, observing acrylic crowns placed below the gingival margin of dogs, noted that under favorable conditions the epithelium adapted closely to the acrylic crown as around a natural tooth. Studying the effects of rough surfaces upon gingival tissue, Waerhaug suggested that the inflammatory changes observed were due to chemical or bacterial irritation rather than to mechanical irritant. He thought that overhanging edges were not a mechanical irritant and that the dental plaque accumulating over rough areas was the cause of inflammation. For Löe, the roughness of restorations rather than chemical irritation produced periodontal lesions. Studying the effect of different materials in class V preparations extending beneath the crest of the gingiva, App observed that silicate cements and amalgams induced chronic gingival inflammations, whereas cast gold restorations were well tolerated in the gingival sulcus. In response to gold sub- and supragingival restorations places in dogs and monkeys, gingival inflam mation was an almost constant finding in the subgingival cases as contrasted to the favorable response in supragin gival cases. Well polished and adapted restorations produced little harmful effect on the adjacent dog gingiva according to Hosoda et al. From all of these experiments, it appeared that gold seems to be by far the best tolerated material. These findings were confirmed by testing the effect of different dental materials on growth and adhesion of animal cells in vitro. Since no ultrastructural investigations have been conducted on the gingival reactions to dental materials, we studied such reactions to gold foil restora tions in the beagle dog. In previous electron microscopic investigations, clinically normal and inflamed gingi val epithelium and lamina propria as well as subgingival dental plaque have been described in the beagle dog. 1
2
3
13
4
5
6
RESULTS
The surface of the gold foil restorations was either covered by dental plaque (Fig. 1 and 3) or by a pellicle of irregular thickness (Fig. 2). The dental plaque was very similar to the subgingival plaque described by Soames and Davies. Some cocci-like bacteria were often covered by numerous filamentous organisms, per pendicularly oriented to the restoration surface. The sulcular epithelium facing the gold foil restorations showed typical signs of inflammation (Fig. 2) with disintegrated superficial epithelial cells, invaded by bacteria, enlarged intercellular spaces (Fig. 4) with localized rupture of cellular junctional systems (Fig. 4) and the presence of a great number of polymorphonuclear neutrophilic leuko-
7,8,9
10
METHODS
12
11
12
* Centré de Recherches, Faculte de Chirurgie Dentaire, 1 place de l'Hopital, 67000 Strasbourg, France. †Facultéde Chirurgie Dentairé, Universite Paris V. ‡Facultéde Chirurgie Dentaire, Université Paris VII.
614
Volume 46 Number 10
Gingival Reactions
FIGURE 1. Dental plaque at the surface of a gold foil restoration (G), consisting in an inner accumulation superficial distribution of filamentous organisms, p = pellicular structure (x 7,000.)
cytes. An intracellular accumulation of glycogen was also noticed in the epithelial cells (Fig. 5). As has been noted by Garant and Mulvihill, in the subepithelial connective tissues of chronically inflamed gingivitis in the beagle dog, we found in the lamina propria facing the gold foil restoration numerous well developed plasma cells (Fig. 6) with an abundant system of granular endoplasmic reticulum. The relationship of the dental plaque and the gold foil restoration is interesting to study. In some cases we found a well differentiated pellicle between the inner layer of bacteria and the gold foil (Fig. 1 and 8), but most often the inner bacterial layer consisting mostly of Gram-negative bacteria (Fig. 7) was directly in contact with the gold restoration. The microorganisms were either densely packed (Fig. 7, 12, 13) or were loosely distributed with an important matrix component (Fig. 1, 8). The gold foil restoration could be satisfactorily sec tioned and it appeared that even well condensed gold foils showed important spaces between them (Fig. 7, 9-12, 14). These spaces, varying from a few Angstroms to 1 n in width, seemed not to be artifacts, since they were filled by an amorphous organic material (Fig. 9 and 14), sometimes delineated by fine membranes (Fig. 9). The diamond knife facilitated performance of a thin section 11
to Gold
of coccal organisms
615
and a
in a gold foil showing its internal lamellar structure (Fig. 15). At the surface of the restoration, a bacterial penetra tion was observed in the superficial space between gold foils when the opening was larger than a micron. One, two or three rows of bacteria could be seen in the superficial openings (Fig. 10, 11), but the bacterial invasion was only located in the first space underlying the superficial gold foil (Fig. 9). Sometimes large elongated crystals, similar to those found in typical dental calculus, were seen obliterating small openings at the surface of the gold restoration (Fig. 12). They apparently prevented bacterial penetration. In one case, the presence of organic material precipitated in the superficial gold foil space maintained the inner bacterial layer at the restora tion surface (Fig. 13). In the cases in which a pure gold strip was burnished on the root surface and bonded with cyanoacrylate, we noted after 3 weeks a good healing of the repositioned flap. The epithelial attachment (Fig. 16, 17, 18) and the lamina propria in contact with the gold were devoid of inflammation and had a normal ultrastructure. N o bacteria was present between the junctional epithelium and the gold. The superficial epithelial cells showed a well developed nucleus with a nucleolus, a rough surfaced endoplasmic reticulum, some free ribosomes and bundles
FIGURE 2. Pellicle of irregular thickness (p) at the surface of a gold foil restoration (G). Severe inflammatory epithelium with bacteria infiltrating superficial desintegrated cells. S = granular material in the sulcus, (x
FIGURE 3. Dental plaque (P) covering a gold foil restoration
(g) and facing a sulcular inflamed epithelium
616
changes in the sulcular 9,000.)
(E). (x
8,400.)
FIGURE 4. Sulcular epithelium (PI), (x 11,000.)
facing a gold foil restoration
FIGURE 5. Cells of the epithelial attachment tonofdament bundles (t). (x 27,000.)
with enlarged intercellular spaces and a migrating neutrophil
with enlarged intercellular
617
spaces (is), accumulation
granulocvte
of glycogen granules (g) and dense
FIGURE 6. Plasma cell infiltration CO = collazen ( x 13,000.)
in the lamina propria
FIGURE 7. Direct bacterial
accumulation
located
under the epithelial
cell attachment,
at the surface of a gold foil restoration
618
e r = endoplasmic
(G). ( x
29,000.)
reticulum.
FIGURE 8. A pellicular structure
(P) is interposed
between the dental plaque (B) and the surface of a gold foil restoration,
(x
67,000.)
FIGURE 9. Presence of a pellicular structure (p) at the surface of a gold foil restoration. Some microorganisms (b) have infiltrated the first superficial space between condensed gold foils. The inner spaces are not empty and are filled with an amorphous organic material (o). (x 31,000.)
619
FIGURE 10. Dental plaque in contact with a gold foil restoration. between two gold foils, (x 23,000.)
A few microorganisms
(b) are infiltrating a superficial space left open
FIGURE 11. Bacteria of the dental plaques can infiltrate the spaces between gold foil restoration (x 34,000.)
620
when these spaces are large
enough.
Volume 46 Number 10
Gingival Reactions
F I G U R E 1 2 . Surface of a gold foil restoration (g) covered by a dental plaque. A few dental calculus crystals (c) prevent the bacteria from penetrating in the spaces between the gold foils. (Original magnification x 25,000.)
of tonofilaments (Fig. 16, 17, 18). The intercellular spaces were of normal width, numerous microvilli and different types of intercellular junctions. Generally the plasmalemma of the epithelial cells adjacent to the gold strip was directly in contact with the metal surface without any intervening space (Fig. 17, 18). Sometimes, however, a small extracellular space, 200 to 500 A in width, was seen between the cell membrane and the gold (Fig. 16), but typical hemidesmosomes were not observed.
to Gold
F I G U R E 1 3 . Organic material ( O ) in the spaces between the gold foils prevent the penetration of the deepest bacteria of the dental plaque ( x 30,000).
the dental plaque. In the case of the gold strip inserted along the root surface, the epithelial attachment has a normal ultrastructure, and the superficial epithelial cells adjacent to the gold are not keratinized. The only difference noted with a junctional epithelium related to the enamel surface is the fact that the cell membrane is directly applied to the gold surface. Sometimes however an extracellular space is visible between the plasmalemma and the gold surface but in these cases, no hemidesmosomes as normally d e s c r i b e d have been identified. Having implanted artificial roots made in epoxy resins in alveolar sockets in monkeys, Listgarten observed differentiation of hemidesmosomes along the superficial cell membranes of the epithelium attachment facing the resin. Therefore hemidesmosomes can differentiate along dental material surfaces. In the present study we can only note their absence in our samples. It could well be that our gold strips had some degree of mobility or that the direct contact between gold and cell membranes related to special physiochemical conditions in the interface prevented the differentiation of the hemidesmosomes. The absence of gingival inflammation in the case of the implanted burnished gold strip and its presence over the gold foils restorations is interesting to discuss. There is probably a great difference in surface roughness in the 14,15,16
DISCUSSION
These two types of experiments were complementary. In the presence of dental plaque at the surface of gold foil restorations, typical ultrastructural signs of chronic inflammation were observed in the sulcular epithelium and the underlying connective tissue. It could thus be concluded that gold restorations placed below the gingi val margin induce chronic inflammation. However in our series of experiments, with a gold strip inserted over the dental root, it appeared that gold per se is not responsi ble for the gingivitis and can be well tolerated by the junctional epithelium and the lamina propria, in the absence of dental plaque. Therefore the ultrastructural biocompatibility of the gold with the gingival tissues is demonstrated and inflammation seemed to be initiated by the presence of
621
17
FIGURE 1 4 . Amorphous organic material is seen in the spaces between the condensed gold foils. B = Bacteria at the surface of the gold foil restoration, ( x 56,000.)
FIGURE 1 5 . Ultrathin section in the thickness of a gold foil showing numerous and irregular lamellar structures.
622
(x
20,000.)
Volume 46 Number 10
Gingival Reactions
to Gold
623
FIGURE 16. Epithelial cell (ep) in contact with a subgingivally implanted gold strip. On the right (arrows) the cell membrane is directly in contact with the gold foil. On the left, an intercellular space is visible (is), but no hemidesmosome is present at the surface of the cell membrane, ( x 62,000.)
FIGURE 17. Presence 18,000.)
of noninflamed
epithelial
cells along a subgingivally
two situations. In the first case, the surface is smooth and as a result the epithelium in contact with the metal is normal. In the second situation, the surface of the condensed gold foil is not even and probably explains the absence of cellular adhesion and the subsequent ingrowth of dental plaque. The importance of well polished and smooth surfaces of dental materials in contact with
implanted
gold strip, n = nucleus, o = nucleolus,
(x
Despite the great care in condensing the gold foils, it is surprising to see that relatively broad spaces, filled by amorphous organic material, existed in the restoration. This organic material is probably of salivary origin. The bacterial penetration in these spaces is only very superfi cial and does not represent a clinical problem. All of the inflammatory changes of the epithelial and
624
J. Periodontol. October, 1975
Frank, Brion, De Rouffignac
FIGURE 18. Direct contact of the cell membrane root surface, ( x 56,000.)
of a superficial
study are identical to the lesions described in the beagle d o g or in m a n during gingivitis. 11
16
SUMMARY
In the case of class-V gold foil restorations prepared below the gingival sulcus in beagle dogs after elevation of a flap, chronic inflammatory changes were observed after 3 weeks in the adjacent epithelium and connective tissue of the gingiva with the presence of dental plaque between the gold restorations and the sulcular epithe lium. However no inflammation was observed in the junctional epithelium and the subjacent connective tissue 3 weeks after implantation of a gold strip burnished and bounded to the root surface after elevation of a flap. The cell membranes of the superficial epithelial cells were either directly applied to the gold surface or were separated from the latter by an extracellular space about 200 to 500 A in width. N o hemidesmosomes were seen. The different responses noted in the two experiments are related to the presence or absence of dental plaque and probably to the surface difference of the gold resto rations. ACKNOWLEDGMENTS
W e wish to thank Professor Edward Housset, Directeur de recherche a T I . N . S . E . R . M . who allowed us to undertake this work in his laboratory. M a n y t h a n k s are due to Pierre Steuer and Michelle Dubois for their efficient technical assistance. REFERENCES
1. W a e r g h a u g , J.: Tissue reactions around artificial crowns. J Periodontol 2 4 : 172, 1953. 2. Waerghaug, J.: Effects of rough surfaces upon gingival tissue. J Dent Res 3 5 : 323, 1956. 3. Loe, H.: Reactions of marginal periodontal tissues t o
epithelial
cell along a gold strip (g) implanted
subgingivally
along a
restorative procedures. Int Dent J 18: 759, 1968. 4. App, G. R.: Effect of silicate, a m a l g a m and cast gold on the gingiva. J Prosthet Dent 11: 522, 1961. 5. Karlsen, K. Gingival reactions t o dental restorations. Acta Odontol Scand 2 8 : 895, 1970. 6. Hosoda, H., H a r a , K., H a n a r i , M., and M a t s u n o , H.: Gingival responses t o class V restorations m a d e of various alloys, on the basis of biochemical analysis of the gingiva exudate. Jap J Conservative Dent 12: 284, 1970. 7. Helgeland, K., and Leirskar, J.: A further testing of the effect of dental materials on growth and adhesion of animal in cells in vitro. Scand J Dent Res 8 0 : 206, 1972. 8. K a w a h a r a , H., Y a m a g a m i , A., and N a k a m u r a Jr. M.: Biological testing of dental material by means of tissue culture. Int Dent J 18: 443, 1968. 9. Sisca, R. F., T h o n a r d , J. C , Lower, D. A., and George, W. A.: Responses of epithelial-like cells in tissue culture t o implant material. J Dent Res 4 6 : 248, 1967. 10. G a r a n t , P. R., and Mulvihill, J. E.: T h e ultrastructure of clinically normal sulcular tissues in the beagle dog. J Periodont Res 6: 252, 1971. 11. G a r a n t , P. R., and Mulvihill, J. E.: The fine structure of gingivitis in the beagle. I I I . Plasma cell infiltration of the subepithelial connective tissue. J Periodont Res 7: 161, 1972. 12. Soames, J . V., and Davies, R . M.: T h e structure of subgingival plaque in a beagle dog. J Periodont Res 9 : 333, 1975. 13. Rebstein, F.: La Jonction entre l'épithélium et l'émail chez F H o m m e . Etude histologique et histochimique. Parodontol Ac Rev 1: 207, 1967. 14. Listgarten, M . A.: Electron microscopic study of the gingivodental junction of men. Am J Anat 119: 147, 1966. 15. Schroeder, H . E.: Ultrastructure of junctional epithe lium of the human gingiva. Helv Odontol Acta 13: 65, 1969. 16. F r a n k , R . M . , and Cimasoni, G.: Ultrastructure d e l'épithélium cliniquement n o r m a l du sillon et de la jonction gingivo-dentaires. Z Zellforsch Mikrosh Anat 109: 356, 1970. 17. Listgarten, M . A., and Lai, C. H.: U l t r a s t r u c t u r e of the intact interface between a n endosseous epoxy resin dental implant and the host tissues. J Biol Buccale 3 : 13, 1975.
Ultrastructural Gingival
Two types of preparations were realized on the perio dontal tissues of four beagle dogs. The animals were anesthetized with Nembutal. No local anesthetic was used. All teeth were cleaned and polished according to standard dental prophylactic procedures. The gingiva of the buccal surface of maxillary and mandibular cuspids, bicuspids and first molars was elevated with a full thickness flap and revealing incisions were made in order to expose the root surface and bone margin. In a first series of experiments, after elevation of the flap, the tooth surfaces were pumiced, washed and dried. They were then etched with 50% phosphoric acid for 2 minutes. A pure gold strip 2/100 mm thick was bur nished on the root surface as close to the bone margin as possible and bonded with cyanoacrylate. In a second series of experiments, class V preparations were made across enamel and cementum and were filled with gold foil restorations. Special care was taken in the condensation of the gold cylinders and in the polishing of the surface. In both series the flap was then sutured back in position. Pressure was applied with a sponge and saline solution for 3 minutes. During the whole experimental period, the dogs received a regular diet composed of canned meat and rice. They were not submitted to any special oral hygiene procedure. After 3 weeks, the animals were sacrificed and the marginal periodontal tissues together with bone and dental tissues were removed according to the technic described by Rebstein. After fixation in a 2% phosphate buffered glutaraldehyde solution for 1 hour followed by a 1 hour postfixation in a 2% osmic acid solution in the same buffer, the specimens were embedded in Epon. Nondecalcified thin sections were made with a ServallPorter microtome equipped with a diamond knife. With this latter, the inserted gold strip and the gold foil restorations could be easily sectioned. After uranyl acetate and lead citrate stainings, the observations were made in a Philips EM 200 and in a Jeol 100 B electron microscope.
Reactions to Gold Foil Restorations by ROBERT M . FRANK* MONIQUE BRION† MlCHÉeLE D E ROUFFIGNAC‡ GINGIVAL REACTIONS to dental materials have been studied with the light microscope and contradictory results were obtained. Waerhaug, observing acrylic crowns placed below the gingival margin of dogs, noted that under favorable conditions the epithelium adapted closely to the acrylic crown as around a natural tooth. Studying the effects of rough surfaces upon gingival tissue, Waerhaug suggested that the inflammatory changes observed were due to chemical or bacterial irritation rather than to mechanical irritant. He thought that overhanging edges were not a mechanical irritant and that the dental plaque accumulating over rough areas was the cause of inflammation. For Löe, the roughness of restorations rather than chemical irritation produced periodontal lesions. Studying the effect of different materials in class V preparations extending beneath the crest of the gingiva, App observed that silicate cements and amalgams induced chronic gingival inflammations, whereas cast gold restorations were well tolerated in the gingival sulcus. In response to gold sub- and supragingival restorations places in dogs and monkeys, gingival inflam mation was an almost constant finding in the subgingival cases as contrasted to the favorable response in supragin gival cases. Well polished and adapted restorations produced little harmful effect on the adjacent dog gingiva according to Hosoda et al. From all of these experiments, it appeared that gold seems to be by far the best tolerated material. These findings were confirmed by testing the effect of different dental materials on growth and adhesion of animal cells in vitro. Since no ultrastructural investigations have been conducted on the gingival reactions to dental materials, we studied such reactions to gold foil restora tions in the beagle dog. In previous electron microscopic investigations, clinically normal and inflamed gingi val epithelium and lamina propria as well as subgingival dental plaque have been described in the beagle dog. 1
2
3
13
4
5
6
RESULTS
The surface of the gold foil restorations was either covered by dental plaque (Fig. 1 and 3) or by a pellicle of irregular thickness (Fig. 2). The dental plaque was very similar to the subgingival plaque described by Soames and Davies. Some cocci-like bacteria were often covered by numerous filamentous organisms, per pendicularly oriented to the restoration surface. The sulcular epithelium facing the gold foil restorations showed typical signs of inflammation (Fig. 2) with disintegrated superficial epithelial cells, invaded by bacteria, enlarged intercellular spaces (Fig. 4) with localized rupture of cellular junctional systems (Fig. 4) and the presence of a great number of polymorphonuclear neutrophilic leuko-
7,8,9
10
METHODS
12
11
12
* Centré de Recherches, Faculte de Chirurgie Dentaire, 1 place de l'Hopital, 67000 Strasbourg, France. †Facultéde Chirurgie Dentairé, Universite Paris V. ‡Facultéde Chirurgie Dentaire, Université Paris VII.
614
Volume 46 Number 10
Gingival Reactions
FIGURE 1. Dental plaque at the surface of a gold foil restoration (G), consisting in an inner accumulation superficial distribution of filamentous organisms, p = pellicular structure (x 7,000.)
cytes. An intracellular accumulation of glycogen was also noticed in the epithelial cells (Fig. 5). As has been noted by Garant and Mulvihill, in the subepithelial connective tissues of chronically inflamed gingivitis in the beagle dog, we found in the lamina propria facing the gold foil restoration numerous well developed plasma cells (Fig. 6) with an abundant system of granular endoplasmic reticulum. The relationship of the dental plaque and the gold foil restoration is interesting to study. In some cases we found a well differentiated pellicle between the inner layer of bacteria and the gold foil (Fig. 1 and 8), but most often the inner bacterial layer consisting mostly of Gram-negative bacteria (Fig. 7) was directly in contact with the gold restoration. The microorganisms were either densely packed (Fig. 7, 12, 13) or were loosely distributed with an important matrix component (Fig. 1, 8). The gold foil restoration could be satisfactorily sec tioned and it appeared that even well condensed gold foils showed important spaces between them (Fig. 7, 9-12, 14). These spaces, varying from a few Angstroms to 1 n in width, seemed not to be artifacts, since they were filled by an amorphous organic material (Fig. 9 and 14), sometimes delineated by fine membranes (Fig. 9). The diamond knife facilitated performance of a thin section 11
to Gold
of coccal organisms
615
and a
in a gold foil showing its internal lamellar structure (Fig. 15). At the surface of the restoration, a bacterial penetra tion was observed in the superficial space between gold foils when the opening was larger than a micron. One, two or three rows of bacteria could be seen in the superficial openings (Fig. 10, 11), but the bacterial invasion was only located in the first space underlying the superficial gold foil (Fig. 9). Sometimes large elongated crystals, similar to those found in typical dental calculus, were seen obliterating small openings at the surface of the gold restoration (Fig. 12). They apparently prevented bacterial penetration. In one case, the presence of organic material precipitated in the superficial gold foil space maintained the inner bacterial layer at the restora tion surface (Fig. 13). In the cases in which a pure gold strip was burnished on the root surface and bonded with cyanoacrylate, we noted after 3 weeks a good healing of the repositioned flap. The epithelial attachment (Fig. 16, 17, 18) and the lamina propria in contact with the gold were devoid of inflammation and had a normal ultrastructure. N o bacteria was present between the junctional epithelium and the gold. The superficial epithelial cells showed a well developed nucleus with a nucleolus, a rough surfaced endoplasmic reticulum, some free ribosomes and bundles
FIGURE 2. Pellicle of irregular thickness (p) at the surface of a gold foil restoration (G). Severe inflammatory epithelium with bacteria infiltrating superficial desintegrated cells. S = granular material in the sulcus, (x
FIGURE 3. Dental plaque (P) covering a gold foil restoration
(g) and facing a sulcular inflamed epithelium
616
changes in the sulcular 9,000.)
(E). (x
8,400.)
FIGURE 4. Sulcular epithelium (PI), (x 11,000.)
facing a gold foil restoration
FIGURE 5. Cells of the epithelial attachment tonofdament bundles (t). (x 27,000.)
with enlarged intercellular spaces and a migrating neutrophil
with enlarged intercellular
617
spaces (is), accumulation
granulocvte
of glycogen granules (g) and dense
FIGURE 6. Plasma cell infiltration CO = collazen ( x 13,000.)
in the lamina propria
FIGURE 7. Direct bacterial
accumulation
located
under the epithelial
cell attachment,
at the surface of a gold foil restoration
618
e r = endoplasmic
(G). ( x
29,000.)
reticulum.
FIGURE 8. A pellicular structure
(P) is interposed
between the dental plaque (B) and the surface of a gold foil restoration,
(x
67,000.)
FIGURE 9. Presence of a pellicular structure (p) at the surface of a gold foil restoration. Some microorganisms (b) have infiltrated the first superficial space between condensed gold foils. The inner spaces are not empty and are filled with an amorphous organic material (o). (x 31,000.)
619
FIGURE 10. Dental plaque in contact with a gold foil restoration. between two gold foils, (x 23,000.)
A few microorganisms
(b) are infiltrating a superficial space left open
FIGURE 11. Bacteria of the dental plaques can infiltrate the spaces between gold foil restoration (x 34,000.)
620
when these spaces are large
enough.
Volume 46 Number 10
Gingival Reactions
F I G U R E 1 2 . Surface of a gold foil restoration (g) covered by a dental plaque. A few dental calculus crystals (c) prevent the bacteria from penetrating in the spaces between the gold foils. (Original magnification x 25,000.)
of tonofilaments (Fig. 16, 17, 18). The intercellular spaces were of normal width, numerous microvilli and different types of intercellular junctions. Generally the plasmalemma of the epithelial cells adjacent to the gold strip was directly in contact with the metal surface without any intervening space (Fig. 17, 18). Sometimes, however, a small extracellular space, 200 to 500 A in width, was seen between the cell membrane and the gold (Fig. 16), but typical hemidesmosomes were not observed.
to Gold
F I G U R E 1 3 . Organic material ( O ) in the spaces between the gold foils prevent the penetration of the deepest bacteria of the dental plaque ( x 30,000).
the dental plaque. In the case of the gold strip inserted along the root surface, the epithelial attachment has a normal ultrastructure, and the superficial epithelial cells adjacent to the gold are not keratinized. The only difference noted with a junctional epithelium related to the enamel surface is the fact that the cell membrane is directly applied to the gold surface. Sometimes however an extracellular space is visible between the plasmalemma and the gold surface but in these cases, no hemidesmosomes as normally d e s c r i b e d have been identified. Having implanted artificial roots made in epoxy resins in alveolar sockets in monkeys, Listgarten observed differentiation of hemidesmosomes along the superficial cell membranes of the epithelium attachment facing the resin. Therefore hemidesmosomes can differentiate along dental material surfaces. In the present study we can only note their absence in our samples. It could well be that our gold strips had some degree of mobility or that the direct contact between gold and cell membranes related to special physiochemical conditions in the interface prevented the differentiation of the hemidesmosomes. The absence of gingival inflammation in the case of the implanted burnished gold strip and its presence over the gold foils restorations is interesting to discuss. There is probably a great difference in surface roughness in the 14,15,16
DISCUSSION
These two types of experiments were complementary. In the presence of dental plaque at the surface of gold foil restorations, typical ultrastructural signs of chronic inflammation were observed in the sulcular epithelium and the underlying connective tissue. It could thus be concluded that gold restorations placed below the gingi val margin induce chronic inflammation. However in our series of experiments, with a gold strip inserted over the dental root, it appeared that gold per se is not responsi ble for the gingivitis and can be well tolerated by the junctional epithelium and the lamina propria, in the absence of dental plaque. Therefore the ultrastructural biocompatibility of the gold with the gingival tissues is demonstrated and inflammation seemed to be initiated by the presence of
621
17
FIGURE 1 4 . Amorphous organic material is seen in the spaces between the condensed gold foils. B = Bacteria at the surface of the gold foil restoration, ( x 56,000.)
FIGURE 1 5 . Ultrathin section in the thickness of a gold foil showing numerous and irregular lamellar structures.
622
(x
20,000.)
Volume 46 Number 10
Gingival Reactions
to Gold
623
FIGURE 16. Epithelial cell (ep) in contact with a subgingivally implanted gold strip. On the right (arrows) the cell membrane is directly in contact with the gold foil. On the left, an intercellular space is visible (is), but no hemidesmosome is present at the surface of the cell membrane, ( x 62,000.)
FIGURE 17. Presence 18,000.)
of noninflamed
epithelial
cells along a subgingivally
two situations. In the first case, the surface is smooth and as a result the epithelium in contact with the metal is normal. In the second situation, the surface of the condensed gold foil is not even and probably explains the absence of cellular adhesion and the subsequent ingrowth of dental plaque. The importance of well polished and smooth surfaces of dental materials in contact with
implanted
gold strip, n = nucleus, o = nucleolus,
(x
Despite the great care in condensing the gold foils, it is surprising to see that relatively broad spaces, filled by amorphous organic material, existed in the restoration. This organic material is probably of salivary origin. The bacterial penetration in these spaces is only very superfi cial and does not represent a clinical problem. All of the inflammatory changes of the epithelial and
624
J. Periodontol. October, 1975
Frank, Brion, De Rouffignac
FIGURE 18. Direct contact of the cell membrane root surface, ( x 56,000.)
of a superficial
study are identical to the lesions described in the beagle d o g or in m a n during gingivitis. 11
16
SUMMARY
In the case of class-V gold foil restorations prepared below the gingival sulcus in beagle dogs after elevation of a flap, chronic inflammatory changes were observed after 3 weeks in the adjacent epithelium and connective tissue of the gingiva with the presence of dental plaque between the gold restorations and the sulcular epithe lium. However no inflammation was observed in the junctional epithelium and the subjacent connective tissue 3 weeks after implantation of a gold strip burnished and bounded to the root surface after elevation of a flap. The cell membranes of the superficial epithelial cells were either directly applied to the gold surface or were separated from the latter by an extracellular space about 200 to 500 A in width. N o hemidesmosomes were seen. The different responses noted in the two experiments are related to the presence or absence of dental plaque and probably to the surface difference of the gold resto rations. ACKNOWLEDGMENTS
W e wish to thank Professor Edward Housset, Directeur de recherche a T I . N . S . E . R . M . who allowed us to undertake this work in his laboratory. M a n y t h a n k s are due to Pierre Steuer and Michelle Dubois for their efficient technical assistance. REFERENCES
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