- Email: [email protected]
Deposition of corrosion products from dowels on human dental root surfaces measured with proton microprobe technique
Nuclear Instruments and Methods 197 (1982) 209-212 North-Holland Publishing Company
209
D E P O S I T I O N OF C O R R O S I O N P R O D U C T S F R O M D O W E L S ON HUMAN DENTAL R O O T SURFACES MEASURED W I T H P R O T O N M I C R O P R O B E T E C H N I Q U E D. B R U N E NIOM, Scandinavian Institute of Dental Materials, Oslo, Norway
G. B R U N E L L Clinic for Prosthetic Dentistry, Link6ping, Sweden
and U. L I N D H Department of Physical Biology, Gustaf Werner Institute, UniversiO' of Uppsala, Uppsala, Sweden
Distribution of copper, mercury and zinc on human teeth root surfaces adjacent to dowels of gold alloy or brass as well as dowels of brass in conjunction with an amalgam crown has been measured with a proton microprobe using PIXE techniques. Upper limits of the contents of gold and silver on the root surfaces were established. Pronounced concentration profiles of copper and zinc were observed on the root surfaces of teeth prepared with dowels of brass. The dowel of gold alloy revealed only zinc deposition. The major part of copper on the root surfaces is assumed to arise from corrosion of the dowels, and has been transported to the surface by diffusion through the dential tubuli. Zinc in the volume analysed is a constituent of dentin tissue as well as a corrosion product of the brass dowel. Part of the zinc level could also be ascribed to erosion of the zinc phosphate cement matrix. The volumes analysed were (25 × 25 × 25)fire 3. The levels of copper, mercury and zinc on the tooth root surfaces attained values up to about 200, 20 and 600 ppm, respectively.
1. Introduction
Deposition of corrosion products on tooth surfaces originating from screwposts has previously been reported by Arvidson and Wroblewski [1]. Brunell measured the distribution of corrosion products from dowels in various parts of roots using electron microprobe combined with energy dispersive analysis of X-rays, i.e. EDAX technique [2]. The present study comprises the measurement of the distribution of copper, gold, mercury or zinc, on root surfaces, arising from corrosion of dowels of brass or gold alloys using proton microprobe and PIXE techniques. One case refers to a tooth prepared with a dowel of brass in conjunction with amalgam crown leading to galvanic effects, which could essentially influence the corrosion rate. Screwposts composed of copper and zinc in contact with amalgam emerged in saline solutions in vitro have been found to be markedly corroded.
According to the findings of Gjerdet and Espevik [3], zinc was a major corrosion product since this element is preferentially dissolved f r o m the alloy due to the effect of dezincification [4]. Characterization of both depth and lateral topography of inorganic constituents on the tooth surface employing proton microprobe and PIXE technique has been accomplished by Lindh and Tveit [5]. According to their investigation strongly elevated levels of copper and zinc have been found in enamel areas adjacent to amalgam restorations.
2. Experimental 2.1. Teeth
The teeth submitted to various endodontic treatments comprise the following cases: Case I: A first upper molar treated with a brass screwpost in the palatinal root adjacent to an amalgam filling was extracted. The treatment was
0167-5087/82/0000-0000/$02.75 © 1982 North-Holland
III. SAMPLEANALYSIS
210
D. Brune et aL / Deposition of corrosion products
performed 10 years prior to the extraction. Case H: A first lower molar treated with a cast post and core of a gold alloy was extracted. A post was inserted in only one canal. The tooth was extracted after about 8 years. The other canal was filled with guttapercha and zinc phosphate cement. Case III: A first upper molar treated with brass screwposts in two canals was in contact with an amalgam crown. The treatment occurred about 8 years before extraction. 2.2. Nuclear techniques
The proton microprobe arrangement connected to the Studsvik 5.5 MeV Van de Graaff accelerator has previously been described [6,7]. In the present study the teeth were covered with a thin film of carbon in order to avoid charge effects. The specimens were mounted on the target holder and submitted to the proton microbeam with a square intersection of dimensions (25 × 25)/~m2. The beam current was about 10 nA. Five measurements were accomplished, each in a period amounting to 800 s. The proton energy was 2.55 MeV, resulting in an effective analysed volume with a depth of 25 ktm in the dentin tissue [7]. The analytical assay was performed with a semiconductor detector located about 5 cm from the irradiated specimens through registration of K and L X-ray lines. In order to suppress the X-ray yield from the major constituents of dentin, i.e. calcium and phosphorus, different absorbers were placed in front of the detector as described previously [5]. Conversion of the X-ray yield from the specimens to elemental concentration was performed using accurately calibrated thin standards of the elements searched for. In the evaluation of the concentrations a thick target factor was applied according to a method described by Carlsson and Akselsson [8].
Fig. I. Extracted tooth. Corrosionproducts appear distinctly in the dark area on the root surface directly below the filling.
Case I: The copper content showed the highest level in the root part close to the dowel (fig. 3). The highest level of zinc was also found in this area. The amounts of copper and zinc in dentin tissue have been reported to be in the range of 0 . 2 - 2 8 ppm and 200-250 ppm respectively according to various investigators [9]. The analytical techniques used were atomic absorption spectrophotometry, emission spectrography or neutron activation analysis [9]. Since the amounts of copper
ENAMEL DENTINALTUBULUS
~ / 3. R e s u l t s a n d d i s c u s s i o n
I" I/
Corrosion products deposited on root surface appear clearly in fig. 1. Fig. 2 presents the longitudinal section of an intact tooth. The distribution of copper, mercury or zinc on the tooth surfaces referring to cases I - I I I is presented in figs. 3-5. The corresponding measurement points are indicated schematically in the figures.
t /
v,;;ll
DENTIN
/1, 1 ¢ ~
PUlp
....
V"~ I l l ~ O0 ALVEOLAR G(~lt][/|l 0 .o
'. I!~!1. o; "~ o,A~.//% • _o O 0 ¢oO~ 0
BONE
HAVERS~AN L,/",I~I/~L
Fig. 2. Longitudinal section of an intact tooth in the jaw.
D. Brune et aL / Deposition of corrosion products
"
BRASS-POST GUTTAPERC~
J,~,~ AMALGAM ZINCPHOSPHATE
\::.~-
CEMENT
211
~ AMALGAM BRASSPOST c;ME.; o wrr. ZINCPHOSPHATECEMENT) \'MEASUREMENTPOINT
2001
ppm
IO0
MERCURY Fig. 3. The figure shows the localization of the brass screwpost in the palatinal canal. The microbeam measurement points are indicated in this figure as well as in figs. 4 and 5. The distributions of copper, mercury and zinc are presented. Note that the measurement points are indicated schematically, and m a y be located differently during the runs of the real teeth.
were considerably higher than the normal levels in the dentin tissue, it was assumed that the copper deposits originated from corrosion of the dowel followed by a diffusion transport through the dentinal tubuli comprising diameters of the order of 1-2 /~m. A major part of zinc shown in fig. 3
~'~ ~\" \ \"" ~"
GOLDALLOY
~ ~ T E
GUrTAF~R~.tA
Fig. 4. The figure shows the localization of the gold alloy post in the one canal. The other canal was filled with guttapercha and zinc phosphate cement. The distribution of zinc on the root surface is presented.
Fig. 5. The figure shows the localization of 2 brass screwposts in conjunction with an amalgam crown. The distribution of copper, mercury and zinc on the root surface is shown.
corresponds to the normal distribution of zinc in dentin. However, since a strong gradient was indicated for zinc on the root surface, having about the same distribution pattern as described for copper, zinc may also have been transported to the surface as a corrosion product from the dowel. Moreover, this zinc deposit may partly originate from erosion of the cement layer surrounding the dowel. The cement matrix contained zinc phosphate cement. Since the inorganic part of dentin is composed mainly of calcium phosphate an additional amount of phosphate from the cement layer could scarcely be detected at the root surface. Consequently, the analytical assay of phosphorous is not feasible to explain the dissolution of the cement layer. Small amounts of mercury even found on the root surfaces were assumed to originate from corrosion of the amalgam crown. Parts of the copper and zinc deposites may also be ascribed to the corrosion of the amalgam crown. Case H: In this case the highes level of zinc was observed on the surface of the root in the part adjacent to the filling of the canal prepared with zinc phosphate cement. Gold and silver were not observed in this case (fig. 4). Detection limits for these elements amount to 10 and 100 ppm, respectively. Gold alloys are well known for their high corrosion resistance. III. SAMPLE ANALYSIS
212
D. Brune et a L / Deposition of corrosion products
Case I I I : I n this case a higher degree of corrosion could be assumed to occur because 2 b r a s s screwposts in contact with a m a l g a m had been inserted in the root canals, resulting in galvanic corrosion (fig. 5). A high level of zinc was also observed on the surface of the root. A major part of this zinc was assumed to represent zinc as a corrosion p r o d u c t of the brass posts. Parts of the zinc deposites also arise from erosion of the cem e n t as well as from corrosion of the a m a l g a m crown. Both copper a n d zinc were approximately h o m o g e n e o u s l y distributed within the parts measured. Also an approximately h o m o g e n e distribution of mercury was observed in these parts. It is assumed that copper on the root surface originates from corrosion of the posts as well as of the crown, while mercury originates from corrosion of the a m a l g a m crown. The various entities have been assumed to have migrated to the root surface by diffusion through the d e n t i n a l tubuli.
References [I] K. Arvidson and J. Wroblewski, Scand. J. Dent. Res. 86 (1978) 200 [2] G. Brunell, in preparation. [3] N.R. Gjerdet and S. Espevik, Swed. Dent. J. 1 (1977) 193. [4] M.G. Fontana and N.D. Greene, Corrosion engineering (MacGraw-Hill, 1967) p. 67. [5] U. Lindh and A.B. Tveit, J. Radioanal. Chem. 59 (1980) 167. [6] D. Brune, U. Lindh and J. Lorentzen, Nucl. Instr. and Meth. 142 (1977) 51. [7] U. Lindh, Int. J. Appl. Rad. Isotop. 31 (1980) 737. [8] L.E. Carlsson and K.R. Akselsson, Nucl. Instr. and Meth: 181 (1981) 531. [9] G.V. Lyengar, W.E. Kollmer and H.J.M. Bowen, The elemental composition of human tissues and body fluids (Verlag Chemie-Weinheim,NY, 1978) p. 116.
209
D E P O S I T I O N OF C O R R O S I O N P R O D U C T S F R O M D O W E L S ON HUMAN DENTAL R O O T SURFACES MEASURED W I T H P R O T O N M I C R O P R O B E T E C H N I Q U E D. B R U N E NIOM, Scandinavian Institute of Dental Materials, Oslo, Norway
G. B R U N E L L Clinic for Prosthetic Dentistry, Link6ping, Sweden
and U. L I N D H Department of Physical Biology, Gustaf Werner Institute, UniversiO' of Uppsala, Uppsala, Sweden
Distribution of copper, mercury and zinc on human teeth root surfaces adjacent to dowels of gold alloy or brass as well as dowels of brass in conjunction with an amalgam crown has been measured with a proton microprobe using PIXE techniques. Upper limits of the contents of gold and silver on the root surfaces were established. Pronounced concentration profiles of copper and zinc were observed on the root surfaces of teeth prepared with dowels of brass. The dowel of gold alloy revealed only zinc deposition. The major part of copper on the root surfaces is assumed to arise from corrosion of the dowels, and has been transported to the surface by diffusion through the dential tubuli. Zinc in the volume analysed is a constituent of dentin tissue as well as a corrosion product of the brass dowel. Part of the zinc level could also be ascribed to erosion of the zinc phosphate cement matrix. The volumes analysed were (25 × 25 × 25)fire 3. The levels of copper, mercury and zinc on the tooth root surfaces attained values up to about 200, 20 and 600 ppm, respectively.
1. Introduction
Deposition of corrosion products on tooth surfaces originating from screwposts has previously been reported by Arvidson and Wroblewski [1]. Brunell measured the distribution of corrosion products from dowels in various parts of roots using electron microprobe combined with energy dispersive analysis of X-rays, i.e. EDAX technique [2]. The present study comprises the measurement of the distribution of copper, gold, mercury or zinc, on root surfaces, arising from corrosion of dowels of brass or gold alloys using proton microprobe and PIXE techniques. One case refers to a tooth prepared with a dowel of brass in conjunction with amalgam crown leading to galvanic effects, which could essentially influence the corrosion rate. Screwposts composed of copper and zinc in contact with amalgam emerged in saline solutions in vitro have been found to be markedly corroded.
According to the findings of Gjerdet and Espevik [3], zinc was a major corrosion product since this element is preferentially dissolved f r o m the alloy due to the effect of dezincification [4]. Characterization of both depth and lateral topography of inorganic constituents on the tooth surface employing proton microprobe and PIXE technique has been accomplished by Lindh and Tveit [5]. According to their investigation strongly elevated levels of copper and zinc have been found in enamel areas adjacent to amalgam restorations.
2. Experimental 2.1. Teeth
The teeth submitted to various endodontic treatments comprise the following cases: Case I: A first upper molar treated with a brass screwpost in the palatinal root adjacent to an amalgam filling was extracted. The treatment was
0167-5087/82/0000-0000/$02.75 © 1982 North-Holland
III. SAMPLEANALYSIS
210
D. Brune et aL / Deposition of corrosion products
performed 10 years prior to the extraction. Case H: A first lower molar treated with a cast post and core of a gold alloy was extracted. A post was inserted in only one canal. The tooth was extracted after about 8 years. The other canal was filled with guttapercha and zinc phosphate cement. Case III: A first upper molar treated with brass screwposts in two canals was in contact with an amalgam crown. The treatment occurred about 8 years before extraction. 2.2. Nuclear techniques
The proton microprobe arrangement connected to the Studsvik 5.5 MeV Van de Graaff accelerator has previously been described [6,7]. In the present study the teeth were covered with a thin film of carbon in order to avoid charge effects. The specimens were mounted on the target holder and submitted to the proton microbeam with a square intersection of dimensions (25 × 25)/~m2. The beam current was about 10 nA. Five measurements were accomplished, each in a period amounting to 800 s. The proton energy was 2.55 MeV, resulting in an effective analysed volume with a depth of 25 ktm in the dentin tissue [7]. The analytical assay was performed with a semiconductor detector located about 5 cm from the irradiated specimens through registration of K and L X-ray lines. In order to suppress the X-ray yield from the major constituents of dentin, i.e. calcium and phosphorus, different absorbers were placed in front of the detector as described previously [5]. Conversion of the X-ray yield from the specimens to elemental concentration was performed using accurately calibrated thin standards of the elements searched for. In the evaluation of the concentrations a thick target factor was applied according to a method described by Carlsson and Akselsson [8].
Fig. I. Extracted tooth. Corrosionproducts appear distinctly in the dark area on the root surface directly below the filling.
Case I: The copper content showed the highest level in the root part close to the dowel (fig. 3). The highest level of zinc was also found in this area. The amounts of copper and zinc in dentin tissue have been reported to be in the range of 0 . 2 - 2 8 ppm and 200-250 ppm respectively according to various investigators [9]. The analytical techniques used were atomic absorption spectrophotometry, emission spectrography or neutron activation analysis [9]. Since the amounts of copper
ENAMEL DENTINALTUBULUS
~ / 3. R e s u l t s a n d d i s c u s s i o n
I" I/
Corrosion products deposited on root surface appear clearly in fig. 1. Fig. 2 presents the longitudinal section of an intact tooth. The distribution of copper, mercury or zinc on the tooth surfaces referring to cases I - I I I is presented in figs. 3-5. The corresponding measurement points are indicated schematically in the figures.
t /
v,;;ll
DENTIN
/1, 1 ¢ ~
PUlp
....
V"~ I l l ~ O0 ALVEOLAR G(~lt][/|l 0 .o
'. I!~!1. o; "~ o,A~.//% • _o O 0 ¢oO~ 0
BONE
HAVERS~AN L,/",I~I/~L
Fig. 2. Longitudinal section of an intact tooth in the jaw.
D. Brune et aL / Deposition of corrosion products
"
BRASS-POST GUTTAPERC~
J,~,~ AMALGAM ZINCPHOSPHATE
\::.~-
CEMENT
211
~ AMALGAM BRASSPOST c;ME.; o wrr. ZINCPHOSPHATECEMENT) \'MEASUREMENTPOINT
2001
ppm
IO0
MERCURY Fig. 3. The figure shows the localization of the brass screwpost in the palatinal canal. The microbeam measurement points are indicated in this figure as well as in figs. 4 and 5. The distributions of copper, mercury and zinc are presented. Note that the measurement points are indicated schematically, and m a y be located differently during the runs of the real teeth.
were considerably higher than the normal levels in the dentin tissue, it was assumed that the copper deposits originated from corrosion of the dowel followed by a diffusion transport through the dentinal tubuli comprising diameters of the order of 1-2 /~m. A major part of zinc shown in fig. 3
~'~ ~\" \ \"" ~"
GOLDALLOY
~ ~ T E
GUrTAF~R~.tA
Fig. 4. The figure shows the localization of the gold alloy post in the one canal. The other canal was filled with guttapercha and zinc phosphate cement. The distribution of zinc on the root surface is presented.
Fig. 5. The figure shows the localization of 2 brass screwposts in conjunction with an amalgam crown. The distribution of copper, mercury and zinc on the root surface is shown.
corresponds to the normal distribution of zinc in dentin. However, since a strong gradient was indicated for zinc on the root surface, having about the same distribution pattern as described for copper, zinc may also have been transported to the surface as a corrosion product from the dowel. Moreover, this zinc deposit may partly originate from erosion of the cement layer surrounding the dowel. The cement matrix contained zinc phosphate cement. Since the inorganic part of dentin is composed mainly of calcium phosphate an additional amount of phosphate from the cement layer could scarcely be detected at the root surface. Consequently, the analytical assay of phosphorous is not feasible to explain the dissolution of the cement layer. Small amounts of mercury even found on the root surfaces were assumed to originate from corrosion of the amalgam crown. Parts of the copper and zinc deposites may also be ascribed to the corrosion of the amalgam crown. Case H: In this case the highes level of zinc was observed on the surface of the root in the part adjacent to the filling of the canal prepared with zinc phosphate cement. Gold and silver were not observed in this case (fig. 4). Detection limits for these elements amount to 10 and 100 ppm, respectively. Gold alloys are well known for their high corrosion resistance. III. SAMPLE ANALYSIS
212
D. Brune et a L / Deposition of corrosion products
Case I I I : I n this case a higher degree of corrosion could be assumed to occur because 2 b r a s s screwposts in contact with a m a l g a m had been inserted in the root canals, resulting in galvanic corrosion (fig. 5). A high level of zinc was also observed on the surface of the root. A major part of this zinc was assumed to represent zinc as a corrosion p r o d u c t of the brass posts. Parts of the zinc deposites also arise from erosion of the cem e n t as well as from corrosion of the a m a l g a m crown. Both copper a n d zinc were approximately h o m o g e n e o u s l y distributed within the parts measured. Also an approximately h o m o g e n e distribution of mercury was observed in these parts. It is assumed that copper on the root surface originates from corrosion of the posts as well as of the crown, while mercury originates from corrosion of the a m a l g a m crown. The various entities have been assumed to have migrated to the root surface by diffusion through the d e n t i n a l tubuli.
References [I] K. Arvidson and J. Wroblewski, Scand. J. Dent. Res. 86 (1978) 200 [2] G. Brunell, in preparation. [3] N.R. Gjerdet and S. Espevik, Swed. Dent. J. 1 (1977) 193. [4] M.G. Fontana and N.D. Greene, Corrosion engineering (MacGraw-Hill, 1967) p. 67. [5] U. Lindh and A.B. Tveit, J. Radioanal. Chem. 59 (1980) 167. [6] D. Brune, U. Lindh and J. Lorentzen, Nucl. Instr. and Meth. 142 (1977) 51. [7] U. Lindh, Int. J. Appl. Rad. Isotop. 31 (1980) 737. [8] L.E. Carlsson and K.R. Akselsson, Nucl. Instr. and Meth: 181 (1981) 531. [9] G.V. Lyengar, W.E. Kollmer and H.J.M. Bowen, The elemental composition of human tissues and body fluids (Verlag Chemie-Weinheim,NY, 1978) p. 116.