Luminescence Spectra of Dental Porcelains W. T. WOZNIAK and B. K. MOORE American Dental Association Health Foundation, Research Institute, Chicago, ilinois 60611 The luminescence spectra were obtained for a series of porcelain teeth and powders currently used in this country. Comparison was made between the spectra of these materials and the spectra of plastic teeth and natural tooth structures. It was found that many of the porcelain teeth and powders have strikingly different luminescence characteristics than those of natural teeth. J Dent Res (57(11-12):971-974, Nov.-Dec. 1978
Introduction. In producing artificial teeth the appearance of the final product is an important consideration for the dental manufacturer. As a result, the properties of these synthetic teeth under various types of illumination are of great importance. It is well-known that natural teeth fluoresce bluish-white under ultraviolet lightl-7. The spectrum consists of broad bands with peak emission near 410 nm when the material is illuminated with 340 nm light. The exact nature of the luminescence is still uncertain although it appears that more than one molecule is involved and that both the organic and inorganic portions contribute. However, for enamel it has been suggested that the organic component is most responsible for the luminescence7.
Dental porcelain manufacturers, in order to simulate natural tooth luminescence, have added small amounts of various inorganic oxides, including those of uranium, to the base porcelain. The presence of uranium in such teeth has recently become a some controversy due to its
matter of
radioactivity810.
In this
paper we report the luminescence a series of porcelain teeth cur-
spectra for
rently manufactured and sold in this country. Our objective was to compare the luminescence from these teeth with natural teeth and thus determine if the luminophors now Received for publication February 28, 1978 Accepted for publication April 12, 1978
used are adequate with regard to the wavelength and intensity of their light emission. During the course of this investigation we
examined the luminescence spectra of a variety of artificial teeth, including porcelain and plastic, as well as porcelain powder used for restorations.
Materials and methods. The artificial teeth and porcelain powders were obtained from the dental manufacturers. The teeth were studied either in the form of thin slices or ground into a powder and pressed into a KBr pellet. The concentration of the porcelain tooth or powder in the KBr pellet was approximately 10%
by weight. Intensity of luminescence measurements were made on KBr pellets containing 25 mg of the porcelain powder or ground porcelain
tooth mixed with 300 mg of KBr. A natural tooth was ground in a similar manner and used as a reference point. The intensities were measured from the peak heights at maximum luminescence and normalized to the intensity obtained for the natural tooth which was given the arbitrary value of 10. Luminescence spectra were obtained by means of an Aminco-Bowman spectrophotofluorometer. The sample was positioned in the sample compartment at an angle of 600 with respect to the incident light beam. This angle is preferable to the 450 angle in that specularly-reflected incident-light intensity will be greater at the 450 angle. An incident angle of 300 also appears to be satisfactory for these measurements. The pellet or tooth slice was placed on a black nonfluorescent metal holder and mounted from the back so that an approximately uniform amount of sample was exposed to the incident-exciting beam. A short wavelength cutoff filter was used to reduce Rayleigh scatter caused by the incident beam whose wavelength was usually below 350 nm. All spectra were measured at room temperature. 971
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9 72
JDent Res November-December 1978
WOZNIAK & MOORE
EMISSION
NATURAL TOOTH EXCITATION
IX z z
300
500
400
WAVELENGTH
( NANOMETERS)
Fig. 1. -Luminescence spectrum of powdered natural tooth.
Results and discussion. Figure 1 shows the observed lum spectrum of a natural tooth slice described experimental arrangemtent. The peak of the excitation or absorptteon sTec trum is near 340 nm, while the emispion has its highest intensity at about 410s420 nm. The tail of the emission spe(ctrum extends to the vicinity of 500 nm, alccounting for the bluish-white appearance c of natural teeth in UV light. Therefore, th e general requirements for artificial teeth are arethat that they absorb ultraviolet light in th e vicinity of 350 nm and emit light with an ntensity maximum near 410-420 nm.
uinescgenhe
The luminescence emission spectra for the materials investigated in this study are given in Table I. Representative spectra are shown in Figures 24. In Table I we have included the peak emission and excitation positions for not only porcelain teeth and powders but also some representative plastic teeth as well. In general, the emission from these teeth and powders is quite variable with most luminescing above 450 nm. A few porcelain teeth currently being manufactured give emission peaks near that observed for natural teeth; yet there are others, e.g., Lactona porcelain powder, which yield no detectable luminescence. Figure 2 depicts the luminescence spectrum for a porcelain powder manufactured by Myerson Tooth Corporation. This powder luminesces in the yellow-green region with a peak emission at 520 nm. Excitation has a maximum at 330 nm. This spectrum is typical of many of the teeth and powders we have studied. We have observed that the peak of luminescence for uranium oxide and uranium salts usually falls between 550 and 580 nm. Thus it is probable that the principal luminescing agents in these teeth and powders are uranium salts. This is not unexpected since most dental manufacturers use uranium in their porcelain9. A small number of the porcelain teeth and powders we studied showed luminescent characteristics closer to those of natural teeth. The spectrum for one of these mater-
TABLE I MANUFACTURER DENTSPLY
TYPE Porcelain (A) Porcelain (B)
Porcelain (C) HOWMEDICA MYERSON
ASTRON
Vinyl Porcelain Powder Porcelain (A) Porcelain (B) Vinyl
Acrylic SCHWED G-C DENTAL COLUMBUS LACTONA UNITEK
Porcelain Porcelain Porcelain Porcelain Powder Porcelain Acrylic
EXCITATION MAX. (nm) 330 320
325
EMISSION MAX. (nm) 520 530 425, 530 475 520, 535 525 520, 535 485
360 320 320, 435 330 320, 360 350 480 435 330 400 325 380, 530 325, 420 NO DETECTABLE LUMINESCENCE 390 310 475 390
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
LUMINESCENCE SPECTRA OF DENTAL POR CELAINS
Vol. 57No. 11-12
MYERSON
POWDER
EMISSION
EXCITATION
L
0
WAVELENGTH
(NANOMETERS)
9 73
ials is shown in Figure 3. This porcelain tooth material, manufactured by G-C Dental Company of Japan, has a peak in the emission spectrum near 400 nm with excitation peaked at 320 nm. To be complete, we also measured the fluorescence spectrum for a series of plastic teeth, both vinyl and acrylic. Figure 4 is typical of the spectra we obtained for many plastic teeth. For this particular tooth the excitation spectrum shows a peak at 360 nm with a shoulder at 320 nm while the
Fig. 2. - Luminescence spectrum of a com- emission spectrum has a maxima at 480 nm. mercial porcelain powder (Myerson). mercial pocliodMost of the plastic teeth we studied showed the same fluorescence characteristics, which indicated that similar fluorescent species are used in their manufacture. Zinc sulfide phosphors have been known to be used in the synthesis of plastic teeth8. It should G- C DENTAL EMISSION be noted that the manufacturer of plastic EXCITATION F teeth has an opportunity not possible with porcelain teeth - namely the investigation / \ < _ of a large group of commercially available organic phosphors and fluorophors for use in tooth production. The high firing temperatures encountered with the porcelains limit consideration to inorganic materials stable at temperatures in the vicinity of 1 100-12000C. The intensity of luminescence is also an important factor in the aesthetic quality of 300 400 500 an artificial tooth. Therefore, we obtained WAVELENGTH (NANOMETERS) Fig. 3. - Luminescence spectrum of a porcelain approximate relative intensities for a repretooth manufactured by G-C Dental Company of sentative number of the porcelain teeth and powders examined in this study. These inJapan. tensity data are shown in Figure 5. All but one of the samples studied have relative intensity values much lower than that of the natural tooth. These values ranged from 0.05 to 0.5 times the luminescence intensity of the natural tooth. Most of the samples in ASTRON VINYL the lower range had emission peaks above EMISSION 500 nm. The samples fluorescing in the 400EXCITATION z \ 450 nm range had intensity values somewhat closer to that of the natural tooth. One sample (labeled C) had a greater intensity by a factor of about two. Another factor for consideration is the lifetime of the emission: it must be sufficiently short (fewer than 100 milliseconds) 300 avoid afterglow in the dark. Although NANOMIETR SI. WAVcLENGTH quantitative lifetimes were not measured in this study, visual observation indicated Fig. 4. Luminescence spectrum of a typical that the materials investigated were satisfactory in this regard. plastic tooth (Astron Dental Company) z
~~4~to
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
9 74
JDent Res November-December 1978
WOZNIAK & MOORE
mum is higher in wavelength.
I
2C
Acknowledgments.
c
We wish to thank Mr. Edward Smith for his experimental assistance in this study. REFERENCES S. A. MANCEWICZ and K. C. HOERMAN, "Characteristics of Insoluble Protein of Tooth and Bone," Arch. Oral Biol., 9,535 (1964). 2. H. J. HORSLEY, "Isolation of Fluorescent Material Present in Calcified Tissues," J. Dent. Res., 46, 106 (1967). 3. J. J. HEFFERREN, S. M. HEFFERREN, K. C. HOERMAN, and A. Y. BALEKJIAN, "Phosphorescence of Enamel Treated with Stannous Salts," J. Dent. Res., 46, 138 (1967). 4. P. D. FRAZIER, D. W. ENGEN, and S. K. SCAMACK, "X-Ray Induced Light Emission 1.
lC
0
H
from
M. -
.1
.& ..-
_
450 (NM)
WAVELENGTH
-
560
i_560
Fig. 5. - Plot of peak intensity o f luminescence of synthetic teeth relative to peak i:ntensity of natural tooth luminescence, (C = C olumbus, G = G-C Dental, N natural tooth, S== Schwed, M = Myerson, D = Dentsply, H = Howme dica). =
Conclusion. From this study it is appareint that many of the presently available po: rcelain teeth do not match the luminescenci e characteristics of natural teeth with regard to the wavelength of maximum luminesc,ence or the intensity of luminescence. A few samples approach the values obtained for natural tooth structures but most are l inacceptable. where a Peth, Even in the case of plastic te eth, where greater variety of luminesce nt materials should be available for incorp)oration into the tooth material, the lumine scence maxia
Enamel, Bone, and Other Calcium Phos-
phate Materials," JDent. Res., 41, 731 (1967). 5. C. A. MCDEVITT and W. G. ARMSTRONG, "Investigations into the Nature of the Fluorescent Material in Calcified Tissue," J. Dent. Res., 48, 1108 (1969). 6. J. B. HALL, J. J. HEFFERREN, and N. H. OLSEN, "Study of the Fluorescent Characteristics of Extracted Human Teeth by Use of a Clinical Fluorometer," J. Dent. Res., 49, 1431 (1970). 7. D. SPITZER and J. J. TEN BOSCH, "The Total Luminescence of Bovine and Human Dental Enamel,"
Calcif Tiss.
Res.,
20, 201
(1976).
8. M. C. O'RIORDAN and C. J. HUNT, "Radio-
active Fluorescers in Dental Porcelain," National Radiological Protection Board of Great Britain Report No. 25 (1974). 9. M. E. MOORE and W. T. MacCULLOCH, "The Inclusion of Radioactive Compounds in Dental Porcelains," Brit. Dent. J., 136, 101 (1974). 10. J. N. WEAVER, "Alpha and Beta Absorbed Doses from Uranium in Porcelain Teeth,"
J. Dent. Res., B501 (1976).
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
Introduction. In producing artificial teeth the appearance of the final product is an important consideration for the dental manufacturer. As a result, the properties of these synthetic teeth under various types of illumination are of great importance. It is well-known that natural teeth fluoresce bluish-white under ultraviolet lightl-7. The spectrum consists of broad bands with peak emission near 410 nm when the material is illuminated with 340 nm light. The exact nature of the luminescence is still uncertain although it appears that more than one molecule is involved and that both the organic and inorganic portions contribute. However, for enamel it has been suggested that the organic component is most responsible for the luminescence7.
Dental porcelain manufacturers, in order to simulate natural tooth luminescence, have added small amounts of various inorganic oxides, including those of uranium, to the base porcelain. The presence of uranium in such teeth has recently become a some controversy due to its
matter of
radioactivity810.
In this
paper we report the luminescence a series of porcelain teeth cur-
spectra for
rently manufactured and sold in this country. Our objective was to compare the luminescence from these teeth with natural teeth and thus determine if the luminophors now Received for publication February 28, 1978 Accepted for publication April 12, 1978
used are adequate with regard to the wavelength and intensity of their light emission. During the course of this investigation we
examined the luminescence spectra of a variety of artificial teeth, including porcelain and plastic, as well as porcelain powder used for restorations.
Materials and methods. The artificial teeth and porcelain powders were obtained from the dental manufacturers. The teeth were studied either in the form of thin slices or ground into a powder and pressed into a KBr pellet. The concentration of the porcelain tooth or powder in the KBr pellet was approximately 10%
by weight. Intensity of luminescence measurements were made on KBr pellets containing 25 mg of the porcelain powder or ground porcelain
tooth mixed with 300 mg of KBr. A natural tooth was ground in a similar manner and used as a reference point. The intensities were measured from the peak heights at maximum luminescence and normalized to the intensity obtained for the natural tooth which was given the arbitrary value of 10. Luminescence spectra were obtained by means of an Aminco-Bowman spectrophotofluorometer. The sample was positioned in the sample compartment at an angle of 600 with respect to the incident light beam. This angle is preferable to the 450 angle in that specularly-reflected incident-light intensity will be greater at the 450 angle. An incident angle of 300 also appears to be satisfactory for these measurements. The pellet or tooth slice was placed on a black nonfluorescent metal holder and mounted from the back so that an approximately uniform amount of sample was exposed to the incident-exciting beam. A short wavelength cutoff filter was used to reduce Rayleigh scatter caused by the incident beam whose wavelength was usually below 350 nm. All spectra were measured at room temperature. 971
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
9 72
JDent Res November-December 1978
WOZNIAK & MOORE
EMISSION
NATURAL TOOTH EXCITATION
IX z z
300
500
400
WAVELENGTH
( NANOMETERS)
Fig. 1. -Luminescence spectrum of powdered natural tooth.
Results and discussion. Figure 1 shows the observed lum spectrum of a natural tooth slice described experimental arrangemtent. The peak of the excitation or absorptteon sTec trum is near 340 nm, while the emispion has its highest intensity at about 410s420 nm. The tail of the emission spe(ctrum extends to the vicinity of 500 nm, alccounting for the bluish-white appearance c of natural teeth in UV light. Therefore, th e general requirements for artificial teeth are arethat that they absorb ultraviolet light in th e vicinity of 350 nm and emit light with an ntensity maximum near 410-420 nm.
uinescgenhe
The luminescence emission spectra for the materials investigated in this study are given in Table I. Representative spectra are shown in Figures 24. In Table I we have included the peak emission and excitation positions for not only porcelain teeth and powders but also some representative plastic teeth as well. In general, the emission from these teeth and powders is quite variable with most luminescing above 450 nm. A few porcelain teeth currently being manufactured give emission peaks near that observed for natural teeth; yet there are others, e.g., Lactona porcelain powder, which yield no detectable luminescence. Figure 2 depicts the luminescence spectrum for a porcelain powder manufactured by Myerson Tooth Corporation. This powder luminesces in the yellow-green region with a peak emission at 520 nm. Excitation has a maximum at 330 nm. This spectrum is typical of many of the teeth and powders we have studied. We have observed that the peak of luminescence for uranium oxide and uranium salts usually falls between 550 and 580 nm. Thus it is probable that the principal luminescing agents in these teeth and powders are uranium salts. This is not unexpected since most dental manufacturers use uranium in their porcelain9. A small number of the porcelain teeth and powders we studied showed luminescent characteristics closer to those of natural teeth. The spectrum for one of these mater-
TABLE I MANUFACTURER DENTSPLY
TYPE Porcelain (A) Porcelain (B)
Porcelain (C) HOWMEDICA MYERSON
ASTRON
Vinyl Porcelain Powder Porcelain (A) Porcelain (B) Vinyl
Acrylic SCHWED G-C DENTAL COLUMBUS LACTONA UNITEK
Porcelain Porcelain Porcelain Porcelain Powder Porcelain Acrylic
EXCITATION MAX. (nm) 330 320
325
EMISSION MAX. (nm) 520 530 425, 530 475 520, 535 525 520, 535 485
360 320 320, 435 330 320, 360 350 480 435 330 400 325 380, 530 325, 420 NO DETECTABLE LUMINESCENCE 390 310 475 390
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
LUMINESCENCE SPECTRA OF DENTAL POR CELAINS
Vol. 57No. 11-12
MYERSON
POWDER
EMISSION
EXCITATION
L
0
WAVELENGTH
(NANOMETERS)
9 73
ials is shown in Figure 3. This porcelain tooth material, manufactured by G-C Dental Company of Japan, has a peak in the emission spectrum near 400 nm with excitation peaked at 320 nm. To be complete, we also measured the fluorescence spectrum for a series of plastic teeth, both vinyl and acrylic. Figure 4 is typical of the spectra we obtained for many plastic teeth. For this particular tooth the excitation spectrum shows a peak at 360 nm with a shoulder at 320 nm while the
Fig. 2. - Luminescence spectrum of a com- emission spectrum has a maxima at 480 nm. mercial porcelain powder (Myerson). mercial pocliodMost of the plastic teeth we studied showed the same fluorescence characteristics, which indicated that similar fluorescent species are used in their manufacture. Zinc sulfide phosphors have been known to be used in the synthesis of plastic teeth8. It should G- C DENTAL EMISSION be noted that the manufacturer of plastic EXCITATION F teeth has an opportunity not possible with porcelain teeth - namely the investigation / \ < _ of a large group of commercially available organic phosphors and fluorophors for use in tooth production. The high firing temperatures encountered with the porcelains limit consideration to inorganic materials stable at temperatures in the vicinity of 1 100-12000C. The intensity of luminescence is also an important factor in the aesthetic quality of 300 400 500 an artificial tooth. Therefore, we obtained WAVELENGTH (NANOMETERS) Fig. 3. - Luminescence spectrum of a porcelain approximate relative intensities for a repretooth manufactured by G-C Dental Company of sentative number of the porcelain teeth and powders examined in this study. These inJapan. tensity data are shown in Figure 5. All but one of the samples studied have relative intensity values much lower than that of the natural tooth. These values ranged from 0.05 to 0.5 times the luminescence intensity of the natural tooth. Most of the samples in ASTRON VINYL the lower range had emission peaks above EMISSION 500 nm. The samples fluorescing in the 400EXCITATION z \ 450 nm range had intensity values somewhat closer to that of the natural tooth. One sample (labeled C) had a greater intensity by a factor of about two. Another factor for consideration is the lifetime of the emission: it must be sufficiently short (fewer than 100 milliseconds) 300 avoid afterglow in the dark. Although NANOMIETR SI. WAVcLENGTH quantitative lifetimes were not measured in this study, visual observation indicated Fig. 4. Luminescence spectrum of a typical that the materials investigated were satisfactory in this regard. plastic tooth (Astron Dental Company) z
~~4~to
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
9 74
JDent Res November-December 1978
WOZNIAK & MOORE
mum is higher in wavelength.
I
2C
Acknowledgments.
c
We wish to thank Mr. Edward Smith for his experimental assistance in this study. REFERENCES S. A. MANCEWICZ and K. C. HOERMAN, "Characteristics of Insoluble Protein of Tooth and Bone," Arch. Oral Biol., 9,535 (1964). 2. H. J. HORSLEY, "Isolation of Fluorescent Material Present in Calcified Tissues," J. Dent. Res., 46, 106 (1967). 3. J. J. HEFFERREN, S. M. HEFFERREN, K. C. HOERMAN, and A. Y. BALEKJIAN, "Phosphorescence of Enamel Treated with Stannous Salts," J. Dent. Res., 46, 138 (1967). 4. P. D. FRAZIER, D. W. ENGEN, and S. K. SCAMACK, "X-Ray Induced Light Emission 1.
lC
0
H
from
M. -
.1
.& ..-
_
450 (NM)
WAVELENGTH
-
560
i_560
Fig. 5. - Plot of peak intensity o f luminescence of synthetic teeth relative to peak i:ntensity of natural tooth luminescence, (C = C olumbus, G = G-C Dental, N natural tooth, S== Schwed, M = Myerson, D = Dentsply, H = Howme dica). =
Conclusion. From this study it is appareint that many of the presently available po: rcelain teeth do not match the luminescenci e characteristics of natural teeth with regard to the wavelength of maximum luminesc,ence or the intensity of luminescence. A few samples approach the values obtained for natural tooth structures but most are l inacceptable. where a Peth, Even in the case of plastic te eth, where greater variety of luminesce nt materials should be available for incorp)oration into the tooth material, the lumine scence maxia
Enamel, Bone, and Other Calcium Phos-
phate Materials," JDent. Res., 41, 731 (1967). 5. C. A. MCDEVITT and W. G. ARMSTRONG, "Investigations into the Nature of the Fluorescent Material in Calcified Tissue," J. Dent. Res., 48, 1108 (1969). 6. J. B. HALL, J. J. HEFFERREN, and N. H. OLSEN, "Study of the Fluorescent Characteristics of Extracted Human Teeth by Use of a Clinical Fluorometer," J. Dent. Res., 49, 1431 (1970). 7. D. SPITZER and J. J. TEN BOSCH, "The Total Luminescence of Bovine and Human Dental Enamel,"
Calcif Tiss.
Res.,
20, 201
(1976).
8. M. C. O'RIORDAN and C. J. HUNT, "Radio-
active Fluorescers in Dental Porcelain," National Radiological Protection Board of Great Britain Report No. 25 (1974). 9. M. E. MOORE and W. T. MacCULLOCH, "The Inclusion of Radioactive Compounds in Dental Porcelains," Brit. Dent. J., 136, 101 (1974). 10. J. N. WEAVER, "Alpha and Beta Absorbed Doses from Uranium in Porcelain Teeth,"
J. Dent. Res., B501 (1976).
Downloaded from jdr.sagepub.com at UCSF LIBRARY & CKM on December 13, 2014 For personal use only. No other uses without permission.
