Effects of Low-energy CO2 Laser Irradiation and the Organic Matrix on Inhibition of Enamel Demineralization

Abstract

In the past two decades, accumulated evidence has clearly demonstrated the inhibitory effects of laser irradiation on enamel demineralization, but the exact mechanisms of these effects remain unclear. The purpose of this study was to investigate the effects of low-energy CO2 laser irradiation on demineralization of both normal human enamel and human enamel with its organic matrix removed. Twenty-four human molars were collected, cleaned, and cut into two halves. One half of each tooth was randomly selected and its lipid and protein content extracted. The other half of each tooth was used as the matched control. Each tooth half had two window areas. All the left windows were treated with a low-energy laser irradiation, whereas the right windows served as the non-laser controls. After caries-like lesion formation in a pH-cycling environment, microradiographs of tooth sections were taken for quantification of demineralization. The mean mineral losses (with standard deviation) of the enamel control, the lased enamel, the non-organic enamel control, and the lased non-organic enamel subgroups were 3955 (1191), 52(49), 4565(1311), and 1191 (940), respectively. A factorial ANOVA showed significant effects of laser irradiation (p = 0.0001), organic matrix (p - 0.0125), and the laser-organic matrix interaction (p = 0.0377). The laser irradiation resulted in a greater than 98% reduction in mineral loss, but the laser effect dropped to about 70% when the organic matrix in the enamel was removed. The results suggest that clinically applicable CO₂ laser irradiation may cause an almost complete inhibition of enamel demineralization.

Keywords

CO2 laser organic matrix enamel demineralization.

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References

Arwill T. , Myrberg N. , Soremark R. (1965). Penetration of radioactive isotopes through enamel and dentin. I. Diffusion of Na22 in fresh and coagulated dental tissues. J Dent Res 44:1299-1303.

Damato FA , Strang R. , Stephen KW (1988). Comparison of solution-and gel-prepared enamel lesions-an in vitro pH-cycling study. J Dent Res 67:1122-1125.

Featherstone JD , Rosenberg H. (1984). Lipid effect on the progress of artificial carious lesions in dental enamel. Caries Res 18:52-55.

Featherstone Jbd , Barrett-Vespone NA , Fried D. , Kantorowitz Z. , Lofthouse J. , Seka W. ( 1995). Rational choice of laser conditions for inhibition of caries progression. In: Lasers in dentistry. Vol. 2394. Bellingham, WA: SPIE, pp. 57-67.

Featherstone Jbd , Fried D. , McCormack SM , Seka W. ( 1996). Effect of pulse duration and repetition rate on CO2 laser inhibition of caries progression. In: Lasers in dentistry. Vol. 2672. Bellingham, WA: SPIE ,pp.79-87.

Featherstone Jbd , Barrett-Vespone NA , Fried D. , Kantorowitz Z. , Seka W. ( 1998). CO2 laser inhibitor of artificial caries-like lesion progression in dental enamel. J Dent Res 77:1397-1403.

Ferreira JM , Palamara J. , Phakey PP , Rachinger WA , Orams HJ (1989). Effects of continuous-wave CO2 laser on the ultrastructure of human dental enamel. Arch Oral Biol 34:551-562.

Fleming S. , Tawashi R. (1977). Dissolution retardation of dental enamel with special reference to the protein matrix. Can J Pharmaceut Sci 12:55-59.

Fowler BO , Kuroda S. (1986). Changes in heated and in laser-irradiated human tooth enamel and their probable effects on solubility. Calcif Tissue Int 38:197-208.

10.

Fox JL , Yu D. , Otsuka M. , Higuchi WI , Wong J. , Powell GL (1992). Initial dissolution rate studies on dental enamel after CO2 laser irradiation. J Dent Res 71:1389-1398.

11.

Fried D. , Glena R. , Featherstone Jbd , Seka W. ( 1995). Multiple pulse irradiation of dental hard tissues at CO2 laser wavelengths. In: Lasers in dentistry I. Vol. 2394 . Bellingham, WA: SPIE, pp. 41-50.

12.

Heilman JR , Jordan TH , Warwick R. , Wefel JS (1997). Remineralization of root surfaces demineralized in solutions of differing fluoride levels. Caries Res 31:423-428.

13.

Higuchi WI , Mir NA , Patel PR , Becker JW , Hefferren JJ (1969). Quantitation of enamel demineralization mechanisms. 3. A critical examination of the hydroxyapatite model. J Dent Res 48:396-409.

14.

Holcomb DW , Young RA (1980). Thermal decomposition of human tooth enamel. Calcif Tissue Int 31:189-201.

15.

Hsu J. , Fox JL , Higuchi WI , Otsuka M. , Yu D. , Powell GL (1994). Heat-treatment-induced reduction in the apparent solubility of human dental enamel. J Dent Res 73:1848-1853.

16.

Hsu J. , Fox JL , Wang Z. , Powell GL , Otsuka M. , Higuchi WI (1998). Combined effects of laser irradiation/solution fluoride ion on enamel demineralization. J Clin Laser Med Surg 16:93-105.

17.

Law S. , Wertz PW , Swartzendruber DC , Squier CA (1995). Regional variation in content, composition and organization of porcine epithelial barrier lipids revealed by thin-layer chromatography and transmission electron microscopy. Arch Oral Biol 40:1085-1091.

18.

McCormack SM , Fried D. , Featherstone JD , Glena RE , Seka W. ( 1995). Scanning electron microscope observations of CO2 laser effects on dental enamel. J Dent Res 74:1702-1708.

19.

Moreno EC , Zahradnik RT (1974). Chemistry of enamel subsurface demineralization in vitro. J Dent Res 53:226-235.

20.

Nelson DG , Wefel JS , Jongebloed WL , Featherstone JD (1987). Morphology, histology and crystallography of human dental enamel treated with pulsed low-energy infrared laser radiation. Caries Res 21 :411-426.

21.

Oho T. , Morioka T. (1990). A possible mechanism of acquired acid resistance of human dental enamel by laser irradiation. Caries Res 24:86-92.

22.

Palamara J. , Phakey PP , Rachinger WA , Orams HJ (1987). The ultrastructure of human dental enamel heat-treated in the temperature range 200 degrees C to 600 degrees C. J Dent Res 66:1742-1747.

23.

Pogrel MA , Muff DF , Marshall GW (1993). Structural changes in dental enamel induced by high energy continuous wave carbon dioxide laser. Lasers Surg Med 13:89-96.

24.

Sato K. ( 1983). Relation between acid dissolution and histological alteration of heated tooth enamel. Caries Res 17:490-495.

25.

Silness J. , Hegdahl T. , Gustavsen F. (1973). Area of the organic-inorganic interface of dental enamel. Acta Odontol Scand 31:123-129.

26.

Stern RH , Sognnaes RF (1972). Laser inhibition of dental caries suggested by first tests in vivo. JAm Dent Assoc 85:1087-1090.

27.

Tagomori S. , Iwase T. (1995). Ultrastructural change of enamel exposed to a normal pulsed Nd-YAG laser. Caries Res 29:513-520.

28.

Travis D. , Glimcher M. (1964). The structure and organization of, and the relationship between the organic matrix and the inorganic crystals of embryonic bovine enamel. J Cell Biol 23:447-497.

29.

Vogel GL , Carey CM , Chow LC , Gregory TM , Brown WE (1987). Ultramicro analysis of the fluid in human enamel during in vitro caries attack by hydrochloric acid. Caries Res 21:310-325.

30.

Yu D. , Fox JL , Hsu J. , Powell GL , Higuchi WI (1993). Computer simulation of surface temperature profiles during CO2 laser irradiation of human enamel. Optical Engineering 32:298-305.