633
Chemical Characterization of Lased Root Surfaces Using Fourier Transform Infrared Photoacoustic Spectroscopy Paillette
Spencer, * David J. Trylovich,f and Charles M. Cobbf
Recently lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces. The purpose of this in vitro investigation was to characterize the chemical structure of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS). Cementum samples, 6 mm 2 mm, were cut from the root surface of extracted non-carious, unerupted human molars. The experimental samples were lased with a NdrYAG laser at an average energy of 80 mJ at 10 pulses per second. Total lasing time ranged from 1 minute 45 seconds to 4 minutes. A non-lased cementum sample served as the control. All spectra were recorded from 4000 to 400 cm-1 using the photoacoustic cell attachment on an Analect RFX-65 FTIR Spectrometer. Photoacoustic FTIR spectra of lased cementum samples showed a decrease in the protein/mineral ratio in comparison to the control. Breakdown of protein at the root surface potentially contributed to an ammonium band at 2010 cm-1. The decreased protein/mineral ratio and the potential surface contamination with protein by-products, may ultimately affect cell reattachment at the cementum surface. / Periodontol 1992; 63:633-636.
Key Words: Lasers; tooth root; periodontal diseases/therapy;
The traditional therapy for periodontally diseased root surfaces is scaling and root planing using hand instruments, ultrasonics, or a combination of both. The removal of root surface contaminants with these techniques allows for the elimination of inflammation and possible reattachment of adjacent tissue.1 Recently, lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces.2 It has been suggested that the laser may be capable of sterilizing the diseased root surface and thus, ultimately promoting cell reattachment.3 Much of our understanding about the effect of lasers on the root surface has been derived from morphologic studies of lased enamel and dentin. In these studies lased tooth surfaces characteristically show crater formation with drops of melted dental hard tissue.4-5 There has been little information presented on the changes in the chemistry of the tooth surface as a result of laser exposure.6,7 Identifying and characterizing the chemical structure of the lased root surface may be crucial to understanding cellular interactions at this site. Infrared spectroscopy is a wellestablished tool for studying the molecular structure of bio-
*Department of Pediatrie Dentistry, University Dentistry, Kansas City, MO.
School of
+Department of Periodontics.
of Missouri-Kansas
City
cementum.
logical
materials. Traditional transmission infrared spec-
troscopy possesses certain experimental limitations, however,
when used with opaque samples such as bone or tooth structure. To acquire transmission spectra from such samples requires either grinding of the sample and dispersion in an infrared transparent matrix or embedding and thin sectioning of the sample.8 These preparatory techniques not only potentially alter the chemical structure of the biological material but may also mutilate the surface. Photoacoustic spectroscopy is a unique adaptation of infrared spectroscopy. In this technique, a solid sample is placed in a specially designed closed cell containing a coupling gas, such as helium, and a sensitive microphone. The sample is exposed to modulated infrared (IR) radiation. The IR radiation absorbed by the sample is converted to heat. When the heat propagates to the sample's surface and subsequently to the coupling gas within the photoacoustic cell, it causes pressure fluctuations and generates a photoacoustic signal.810 If a thick biological sample is used only the heat generated within the first few microns of the sample's surface can propagate to the surface and generate acoustic signals. Thus FTIR photoacoustic spectroscopy can be used as a near-surface analytical technique.10 The purpose of this in vitro investigation was to characterize the chemistry of root surfaces following timed ex-
634
J Periodontol July 1992
CHEMICAL CHARACTERIZATION OF LASED SURFACES
posures to
a
Nd:YAG laser.* Fourier transform infrared
photoacoustic spectroscopy (FTIR/PAS) was utilized to determine surface functionality of these samples. This is the
first report of chemical characterization of a lased root surface using a technique that will provide molecular information a few microns into the surface. MATERIALS AND METHODS Samples 6 mm in diameter with a thickness of 2 mm were cut from the root surfaces of extracted non-carious, unerupted human molars. Due to the size of the sample it was necessary to recover each sample from a different tooth. The specimens were exposed to an air-water-powder abrasive spray5 for 10 seconds to remove any tissue remnants. The samples were then rinsed in distilled water and brushed gently to remove any residual powder. The experimental root samples were lased with the Nd:YAG laser using a 320-µ contact optic fiber with an average energy of 80 mJ at 10 pulses per second. Two samples were evaluated at each of the following time periods: 1 minute/45 seconds, 2 minutes/30 seconds, and 4 minutes. Five randomly selected non-lased samples served as the controls. All specimens were stored in a desiccator at 4°C for 1 week prior to
spectroscopic analysis.
FTIR photoacoustic spectra were recorded using an Analect RFX 65 Fourier transform infrared spectrometer equipped with an MTEC Photoacoustics Model 200 photoacoustic cell. All spectra were collected at a resolution of 8 cm-1, with a scan speed of 0.5 cmrVsecond. An improved signal-to-noise ratio was obtained by collecting 1000 scans for each sample. The sample single beam spectra were ratioed against a carbon black reference supplied by MTEC Photoacoustics. The photoacoustic detector is responsive over the spectral range of 400-4000 cm-1. A spectrum was recorded from the surface of each experimental sample twice. Comparison of these spectra showed no change in absorption band position or intensity between these successive spectra. RESULTS The photoacoustic FTIR spectrum of a representative nonlased root surface is shown in Figure 1A. The observed spectrum reveals vibrations of both the organic and inorganic components. The major protein contributions are indicated by the absorption bands at 1650 cm-1 (amide I, C 0), 1550 cm-1 (amide II, N-H, and C-N), and 1240 cm-1 (amide III, C-N, and N-H). Contributions from the mineral phase are the orthophosphate bands at 1030-1160 cm-1 and 600-560 cm-1, and the carbonate band at 870 cm-1. The carbonate band at 1450-1425 cm-1 is overlapped with contributions from the amide II band. A broad O-H absorption band is recorded between 3500 and 3300 =
cm-1.
* American
Dental Laser Inc., Birmingham, MI. 5Prophy-Jet 30, Dentsply International, York, PA.
Figure l.a. Photoacoustic FTIR spectrum of non-lased cementum sample, b. Photoacoustic FTIR spectrum of cementum sample following 4-minute exposure to
a
Nd-YAG laser.
Spectra were recorded from the surface of 4 randomly selected non-lased root samples and compared to the spectrum shown in Figure 1A. Absorption band position and relative intensity of the protein and mineral components were carefully noted in these spectra. Integrated areas of the amide I and phosphate bands provided a relative comparison between these samples. These non-lased root samples taken from different teeth showed no differences in absorption band position and only slight differences in the amide I/phosphate ratio. The FTIR photoacoustic spectrum of a root sample exposed for 4 minutes to the Nd-YAG laser is shown in Figure IB. The absorption band at 2010 cm-1 is tentatively assigned to ammonium.11 The amide III band at 1240 cm-1 is significantly reduced in this spectrum, appearing only as a shoulder on the broad phosphate band. The relative intensity of the phosphate bands is greatly increased in comparison to the intensity of the amide I and amide II bands. The broad O-H band at 3500-3300 cm-1 is also reduced in
intensity.
The FTIR photoacoustic spectrum of a root sample exposed to the laser for 1 minute 45 seconds is shown in Figure 2A. There are minimal differences between this spectrum and the non-lased root surface. Figure 2B is the FTIR photoacoustic spectrum of a root surface exposed to the laser for 2 minutes 30 seconds. There is a weak absorption band at 2010 cm-1 in this spectrum. The relative intensity of the amide I and amide II bands is slightly decreased in comparison to the phosphate bands. DISCUSSION Infrared spectroscopy has previously been used to study the chemical nature of biological materials. However, the present study describes for the first time how the chemical structure of a biological substrate, modified by exposure to a
Volume 63 Number 7
SPENCER, TRYLOVICH, COBB 1037
a. Photoacoustic FTIR spectrum of cementum sample following 1 minute/45 seconds exposure to a Nd-YAG laser, b. Photoacoustic FTIR spectrum of cementum sample following 2 minutes/30 seconds exposure
Figure 2. to
a
Nd-YAG laser.
laser, was studied using FTIR photoacoustic spectroscopy.
principal advantage of this technique is that the samples may be studied without any additional handling or preparation that might degrade or alter the lased surface. Based on our results, it appears that this technique is an extremely useful tool for evaluating the chemical nature of reactions A
at the root surface. Laser treatment of
the root surfaces at 4 minutes prosignificant changes in the photoacoustic spectrum. In comparing this spectrum with the spectrum of the control sample, the proportion of protein to mineral in these samples was greatly reduced. The decrease in intensity of all the bands attributable to the protein component indicates the reactivity of these groups in response to the lasing condition. These results support previous investigations that reported that the laser ablated the organic material.7'12 In a complex spectrum, such as seen with many biological materials, it may be difficult to precisely assign absorption peaks. The assignment of the band at 2010 cm-1 to ammonium is based upon careful review of spectra from standard materials. The appearance of the ammonium band may be attributable to the breakdown of protein. Such surface contamination could potentially affect cell viability13 and cell attachment.14 Similar changes in the protein/mineral ratio were noted following laser exposure times as short as 2 minutes/30 seconds. The spectrum of this lased root sample suggests some loss of protein at the surface. In contrast, virtually no change was noted in photoacoustic spectra following laser exposure times of 1 minute/45 seconds. In conclusion, one fundamental aspect of our efforts to develop successful periodontal therapies is the identification and characterization of chemical changes produced at the root surface. The effect of lasers on toofh surfaces has been predominately evaluated using morphologic characteriza-
duced
635
tion;4'5 there has been little information6'7 presented on the chemistry of the lased tooth surface. In this study, FTIR photoacoustic spectroscopy was used to examine chemical processes at the root surface following exposure to a Nd:YAG laser. This method offers several advantages in comparison to other spectroscopic techniques. For example, spectra can be obtained from samples that are completely opaque to transmitted light, thus eliminating any structural defects that might be produced by either thin-sectioning or grinding the material.15'16 Because this technique analyzes the molecular structure a few microns into the surface of a root sample, it allows for evaluation of chemical interactions at the site of treatment. Based on the results reported here, laser treatment provokes significant changes in the protein/mineral ratio at the root surface. In addition, following prolonged exposure, the surface may be contaminated with by-products from the breakdown of protein. These factors may ultimately affect cell reattachment at the root surface.
Acknowledgments
The authors are indebted to Ms. Eileen Roach and Ms. Laura Marshall for their expert technical assistance. This project was supported in part by American Dental Laser Inc., Birmingham, MI and USPHS Research Grant Kll DE-00260-03 from the National Institute of Dental Research, Bethesda, MD. REFERENCES 1. Knowles JW, Burgett FG, Nissle RR, Shick RA, Morrison EC, Ramfjord SP. Results of periodontal treatment related to pocket depth and attachment level. Eight years. J Periodontol 1979;50:225-233. 2. Dunlap J. Is there a laser in your future? Dent Econ 1988;78:40-44. 3. Myers TD. What lasers can do for dentistry and you. Dent Manage 1989;29:26-28.
Scanning electron microscopic study of laser-induced morphologic changes of a coated enamel surface. Lasers Surg Med
4. Hess JA.
5.
1990;10:458-462. Myers TD. Effects of a pulsed Nd:YAG laser on enamel and dentin. In: Joffe SN, Atsumi , eds. Proceedings of Laser Surgery: Advanced Characterization, Therapeutics, and Systems II. Bellingham, Washington: SPIE-International Society for Optical Engineering; 1990:425-
436. 6. Kuroda S, Fowler BO. Compositional, structural, and phase changes in in vitro laser-irradiated human tooth enamel. Calcif Tissue Int
1984;36:361-369.
7. Rantola S. Laser-induced effects on tooth structure. V. Electron probe microanalysis and polarized light microscopy of dental enamel. Acta Odontol Scand 1972;30:474-484. 8. Rosencwaig A. Photoacoustic spectroscopy. A new tool of investigation of solids. Anal Chem 1975;47:592A-604A. 9. Adams MJ, Kirkbright GF. Analytical optoacoustic spectroscopy. Part III. The optoacoustic effect and thermal diffusivity. Analyst
10.
1977;102:281-292. Yang CQ. Comparison of photoacoustic frared spectroscopy
as
near-surface
and diffuse reflectance in-
analysis techniques. Appi Spect
1991;45:102-108. Bellamy LJ. The Infrared Spectra of Complex Molecules.
London: Methuen & Co., Ltd. 1958:75-87. 12. Rantola S, Laine , Tama . Laser-induced effects on tooth structure. 11.
636
J Periodontol
CHEMICAL CHARACTERIZATION OF LASED SURFACES
VI. X-ray diffraction study of dental enamel exposed to a C02 laser. Acta OdontolScand 1973;31:369-379. 13. Rizzo AA. Rabbit corneal irrigation as a model system for studies on the relative toxicity of bacterial products implicated in periodontal disease. The toxicity of neutralized ammonia solutions. / Periodontol 14.
1967;38:491^99. Trylovich DJ. The effect of the Nd:YAG
laser on in vitro fibroblast attachment to endotoxin treated root surfaces. [Thesis]. Kansas City, Missouri: University of Missouri-Kansas City School of Dentistry, 1991:19-35. 15. Mendelsohn R, Hassankhani A, Di Carlo E, Boskey A. FTIR mi-
July
1992
croscopy of endochondral ossification at 20µ spatial resolution. Calcif Tiss Int 1989;44:20-24. 16. Renugopalakrishnan V, Chandrakanaan G, Moore S, Hutson TB, Berney CV, Bhatnagan RS. Bound water in collagen. Evidence from Fourier transform infrared and Fourier transform infrared photoacoustic spectroscopic study. Macromolecules 1989;22:4121^tl24. Send reprint requests to: Dr. Charles Cobb, Department of Periodontics, University of Missouri-Kansas City School of Dentistry, Kansas City, MO 64108.
Accepted for publication February 3,
1992.
Chemical Characterization of Lased Root Surfaces Using Fourier Transform Infrared Photoacoustic Spectroscopy Paillette
Spencer, * David J. Trylovich,f and Charles M. Cobbf
Recently lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces. The purpose of this in vitro investigation was to characterize the chemical structure of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS). Cementum samples, 6 mm 2 mm, were cut from the root surface of extracted non-carious, unerupted human molars. The experimental samples were lased with a NdrYAG laser at an average energy of 80 mJ at 10 pulses per second. Total lasing time ranged from 1 minute 45 seconds to 4 minutes. A non-lased cementum sample served as the control. All spectra were recorded from 4000 to 400 cm-1 using the photoacoustic cell attachment on an Analect RFX-65 FTIR Spectrometer. Photoacoustic FTIR spectra of lased cementum samples showed a decrease in the protein/mineral ratio in comparison to the control. Breakdown of protein at the root surface potentially contributed to an ammonium band at 2010 cm-1. The decreased protein/mineral ratio and the potential surface contamination with protein by-products, may ultimately affect cell reattachment at the cementum surface. / Periodontol 1992; 63:633-636.
Key Words: Lasers; tooth root; periodontal diseases/therapy;
The traditional therapy for periodontally diseased root surfaces is scaling and root planing using hand instruments, ultrasonics, or a combination of both. The removal of root surface contaminants with these techniques allows for the elimination of inflammation and possible reattachment of adjacent tissue.1 Recently, lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces.2 It has been suggested that the laser may be capable of sterilizing the diseased root surface and thus, ultimately promoting cell reattachment.3 Much of our understanding about the effect of lasers on the root surface has been derived from morphologic studies of lased enamel and dentin. In these studies lased tooth surfaces characteristically show crater formation with drops of melted dental hard tissue.4-5 There has been little information presented on the changes in the chemistry of the tooth surface as a result of laser exposure.6,7 Identifying and characterizing the chemical structure of the lased root surface may be crucial to understanding cellular interactions at this site. Infrared spectroscopy is a wellestablished tool for studying the molecular structure of bio-
*Department of Pediatrie Dentistry, University Dentistry, Kansas City, MO.
School of
+Department of Periodontics.
of Missouri-Kansas
City
cementum.
logical
materials. Traditional transmission infrared spec-
troscopy possesses certain experimental limitations, however,
when used with opaque samples such as bone or tooth structure. To acquire transmission spectra from such samples requires either grinding of the sample and dispersion in an infrared transparent matrix or embedding and thin sectioning of the sample.8 These preparatory techniques not only potentially alter the chemical structure of the biological material but may also mutilate the surface. Photoacoustic spectroscopy is a unique adaptation of infrared spectroscopy. In this technique, a solid sample is placed in a specially designed closed cell containing a coupling gas, such as helium, and a sensitive microphone. The sample is exposed to modulated infrared (IR) radiation. The IR radiation absorbed by the sample is converted to heat. When the heat propagates to the sample's surface and subsequently to the coupling gas within the photoacoustic cell, it causes pressure fluctuations and generates a photoacoustic signal.810 If a thick biological sample is used only the heat generated within the first few microns of the sample's surface can propagate to the surface and generate acoustic signals. Thus FTIR photoacoustic spectroscopy can be used as a near-surface analytical technique.10 The purpose of this in vitro investigation was to characterize the chemistry of root surfaces following timed ex-
634
J Periodontol July 1992
CHEMICAL CHARACTERIZATION OF LASED SURFACES
posures to
a
Nd:YAG laser.* Fourier transform infrared
photoacoustic spectroscopy (FTIR/PAS) was utilized to determine surface functionality of these samples. This is the
first report of chemical characterization of a lased root surface using a technique that will provide molecular information a few microns into the surface. MATERIALS AND METHODS Samples 6 mm in diameter with a thickness of 2 mm were cut from the root surfaces of extracted non-carious, unerupted human molars. Due to the size of the sample it was necessary to recover each sample from a different tooth. The specimens were exposed to an air-water-powder abrasive spray5 for 10 seconds to remove any tissue remnants. The samples were then rinsed in distilled water and brushed gently to remove any residual powder. The experimental root samples were lased with the Nd:YAG laser using a 320-µ contact optic fiber with an average energy of 80 mJ at 10 pulses per second. Two samples were evaluated at each of the following time periods: 1 minute/45 seconds, 2 minutes/30 seconds, and 4 minutes. Five randomly selected non-lased samples served as the controls. All specimens were stored in a desiccator at 4°C for 1 week prior to
spectroscopic analysis.
FTIR photoacoustic spectra were recorded using an Analect RFX 65 Fourier transform infrared spectrometer equipped with an MTEC Photoacoustics Model 200 photoacoustic cell. All spectra were collected at a resolution of 8 cm-1, with a scan speed of 0.5 cmrVsecond. An improved signal-to-noise ratio was obtained by collecting 1000 scans for each sample. The sample single beam spectra were ratioed against a carbon black reference supplied by MTEC Photoacoustics. The photoacoustic detector is responsive over the spectral range of 400-4000 cm-1. A spectrum was recorded from the surface of each experimental sample twice. Comparison of these spectra showed no change in absorption band position or intensity between these successive spectra. RESULTS The photoacoustic FTIR spectrum of a representative nonlased root surface is shown in Figure 1A. The observed spectrum reveals vibrations of both the organic and inorganic components. The major protein contributions are indicated by the absorption bands at 1650 cm-1 (amide I, C 0), 1550 cm-1 (amide II, N-H, and C-N), and 1240 cm-1 (amide III, C-N, and N-H). Contributions from the mineral phase are the orthophosphate bands at 1030-1160 cm-1 and 600-560 cm-1, and the carbonate band at 870 cm-1. The carbonate band at 1450-1425 cm-1 is overlapped with contributions from the amide II band. A broad O-H absorption band is recorded between 3500 and 3300 =
cm-1.
* American
Dental Laser Inc., Birmingham, MI. 5Prophy-Jet 30, Dentsply International, York, PA.
Figure l.a. Photoacoustic FTIR spectrum of non-lased cementum sample, b. Photoacoustic FTIR spectrum of cementum sample following 4-minute exposure to
a
Nd-YAG laser.
Spectra were recorded from the surface of 4 randomly selected non-lased root samples and compared to the spectrum shown in Figure 1A. Absorption band position and relative intensity of the protein and mineral components were carefully noted in these spectra. Integrated areas of the amide I and phosphate bands provided a relative comparison between these samples. These non-lased root samples taken from different teeth showed no differences in absorption band position and only slight differences in the amide I/phosphate ratio. The FTIR photoacoustic spectrum of a root sample exposed for 4 minutes to the Nd-YAG laser is shown in Figure IB. The absorption band at 2010 cm-1 is tentatively assigned to ammonium.11 The amide III band at 1240 cm-1 is significantly reduced in this spectrum, appearing only as a shoulder on the broad phosphate band. The relative intensity of the phosphate bands is greatly increased in comparison to the intensity of the amide I and amide II bands. The broad O-H band at 3500-3300 cm-1 is also reduced in
intensity.
The FTIR photoacoustic spectrum of a root sample exposed to the laser for 1 minute 45 seconds is shown in Figure 2A. There are minimal differences between this spectrum and the non-lased root surface. Figure 2B is the FTIR photoacoustic spectrum of a root surface exposed to the laser for 2 minutes 30 seconds. There is a weak absorption band at 2010 cm-1 in this spectrum. The relative intensity of the amide I and amide II bands is slightly decreased in comparison to the phosphate bands. DISCUSSION Infrared spectroscopy has previously been used to study the chemical nature of biological materials. However, the present study describes for the first time how the chemical structure of a biological substrate, modified by exposure to a
Volume 63 Number 7
SPENCER, TRYLOVICH, COBB 1037
a. Photoacoustic FTIR spectrum of cementum sample following 1 minute/45 seconds exposure to a Nd-YAG laser, b. Photoacoustic FTIR spectrum of cementum sample following 2 minutes/30 seconds exposure
Figure 2. to
a
Nd-YAG laser.
laser, was studied using FTIR photoacoustic spectroscopy.
principal advantage of this technique is that the samples may be studied without any additional handling or preparation that might degrade or alter the lased surface. Based on our results, it appears that this technique is an extremely useful tool for evaluating the chemical nature of reactions A
at the root surface. Laser treatment of
the root surfaces at 4 minutes prosignificant changes in the photoacoustic spectrum. In comparing this spectrum with the spectrum of the control sample, the proportion of protein to mineral in these samples was greatly reduced. The decrease in intensity of all the bands attributable to the protein component indicates the reactivity of these groups in response to the lasing condition. These results support previous investigations that reported that the laser ablated the organic material.7'12 In a complex spectrum, such as seen with many biological materials, it may be difficult to precisely assign absorption peaks. The assignment of the band at 2010 cm-1 to ammonium is based upon careful review of spectra from standard materials. The appearance of the ammonium band may be attributable to the breakdown of protein. Such surface contamination could potentially affect cell viability13 and cell attachment.14 Similar changes in the protein/mineral ratio were noted following laser exposure times as short as 2 minutes/30 seconds. The spectrum of this lased root sample suggests some loss of protein at the surface. In contrast, virtually no change was noted in photoacoustic spectra following laser exposure times of 1 minute/45 seconds. In conclusion, one fundamental aspect of our efforts to develop successful periodontal therapies is the identification and characterization of chemical changes produced at the root surface. The effect of lasers on toofh surfaces has been predominately evaluated using morphologic characteriza-
duced
635
tion;4'5 there has been little information6'7 presented on the chemistry of the lased tooth surface. In this study, FTIR photoacoustic spectroscopy was used to examine chemical processes at the root surface following exposure to a Nd:YAG laser. This method offers several advantages in comparison to other spectroscopic techniques. For example, spectra can be obtained from samples that are completely opaque to transmitted light, thus eliminating any structural defects that might be produced by either thin-sectioning or grinding the material.15'16 Because this technique analyzes the molecular structure a few microns into the surface of a root sample, it allows for evaluation of chemical interactions at the site of treatment. Based on the results reported here, laser treatment provokes significant changes in the protein/mineral ratio at the root surface. In addition, following prolonged exposure, the surface may be contaminated with by-products from the breakdown of protein. These factors may ultimately affect cell reattachment at the root surface.
Acknowledgments
The authors are indebted to Ms. Eileen Roach and Ms. Laura Marshall for their expert technical assistance. This project was supported in part by American Dental Laser Inc., Birmingham, MI and USPHS Research Grant Kll DE-00260-03 from the National Institute of Dental Research, Bethesda, MD. REFERENCES 1. Knowles JW, Burgett FG, Nissle RR, Shick RA, Morrison EC, Ramfjord SP. Results of periodontal treatment related to pocket depth and attachment level. Eight years. J Periodontol 1979;50:225-233. 2. Dunlap J. Is there a laser in your future? Dent Econ 1988;78:40-44. 3. Myers TD. What lasers can do for dentistry and you. Dent Manage 1989;29:26-28.
Scanning electron microscopic study of laser-induced morphologic changes of a coated enamel surface. Lasers Surg Med
4. Hess JA.
5.
1990;10:458-462. Myers TD. Effects of a pulsed Nd:YAG laser on enamel and dentin. In: Joffe SN, Atsumi , eds. Proceedings of Laser Surgery: Advanced Characterization, Therapeutics, and Systems II. Bellingham, Washington: SPIE-International Society for Optical Engineering; 1990:425-
436. 6. Kuroda S, Fowler BO. Compositional, structural, and phase changes in in vitro laser-irradiated human tooth enamel. Calcif Tissue Int
1984;36:361-369.
7. Rantola S. Laser-induced effects on tooth structure. V. Electron probe microanalysis and polarized light microscopy of dental enamel. Acta Odontol Scand 1972;30:474-484. 8. Rosencwaig A. Photoacoustic spectroscopy. A new tool of investigation of solids. Anal Chem 1975;47:592A-604A. 9. Adams MJ, Kirkbright GF. Analytical optoacoustic spectroscopy. Part III. The optoacoustic effect and thermal diffusivity. Analyst
10.
1977;102:281-292. Yang CQ. Comparison of photoacoustic frared spectroscopy
as
near-surface
and diffuse reflectance in-
analysis techniques. Appi Spect
1991;45:102-108. Bellamy LJ. The Infrared Spectra of Complex Molecules.
London: Methuen & Co., Ltd. 1958:75-87. 12. Rantola S, Laine , Tama . Laser-induced effects on tooth structure. 11.
636
J Periodontol
CHEMICAL CHARACTERIZATION OF LASED SURFACES
VI. X-ray diffraction study of dental enamel exposed to a C02 laser. Acta OdontolScand 1973;31:369-379. 13. Rizzo AA. Rabbit corneal irrigation as a model system for studies on the relative toxicity of bacterial products implicated in periodontal disease. The toxicity of neutralized ammonia solutions. / Periodontol 14.
1967;38:491^99. Trylovich DJ. The effect of the Nd:YAG
laser on in vitro fibroblast attachment to endotoxin treated root surfaces. [Thesis]. Kansas City, Missouri: University of Missouri-Kansas City School of Dentistry, 1991:19-35. 15. Mendelsohn R, Hassankhani A, Di Carlo E, Boskey A. FTIR mi-
July
1992
croscopy of endochondral ossification at 20µ spatial resolution. Calcif Tiss Int 1989;44:20-24. 16. Renugopalakrishnan V, Chandrakanaan G, Moore S, Hutson TB, Berney CV, Bhatnagan RS. Bound water in collagen. Evidence from Fourier transform infrared and Fourier transform infrared photoacoustic spectroscopic study. Macromolecules 1989;22:4121^tl24. Send reprint requests to: Dr. Charles Cobb, Department of Periodontics, University of Missouri-Kansas City School of Dentistry, Kansas City, MO 64108.
Accepted for publication February 3,
1992.
