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1 ora-eudurado 417 v3.4.intjdc


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1 ora-eudurado 417 v3.4.intjdc

  1. 1. ISSN 0975-8437 INTERNATIONAL JOURNAL OF DENTAL CLINICS 2011:3(4):1-4 ORIGINAL RESEARCH ARTICLE Surface hardness and color change of dental enamel exposed to cigarette smoke Bertoldo.C.E.dos.S, Souza-Júnior.EJ, Aguiar.FHB, Lima.DANL, Ferreira.R.L, Claes.I, Lovadino.JR Abstract Background: Tooth susceptibility to discoloration can be attributed to defects in enamel and dentin due to pigments penetration into the cracks and tubules present in the dental substrates Aims & Objectives: This in vitro study was undertaken to evaluate the microhardness and the color change of dental enamel exposed to cigarette smoke. Materials & Methods: Fifteen bovine enamel fragments (25mm2) were submitted to exposure to the equivalent of cigarette smoke from 50 cigarettes over a period of five days. Initial and final readings of microhardness and colorimetric evaluation were performed. The results were analyzed statistically with the one-way ANOVA and Tukey test (p≤0.05). Results: The samples presented a significant color change and a decrease in the values of microhardness. Conclusion: In conclusion, the exposure to cigarette smoke can significantly alter the microhardness of enamel and its coloring. Key Words: Knoop hardness; Color; cigarette smoke; dental enamel Introduction Tooth susceptibility to discoloration can be attributed to defects in enamel and dentin due to pigments penetration into the cracks and tubules present in the dental substrates. Also, these pigments can be incorporated into their organic content. Possible causes for the discoloration of enamel and/or dentin include food or beverages containing pigments, oral therapies that include chlorhexidine, dental caries, the presence of metals such as iron, and high temperatures. In addition, tobacco can usually cause stains on the enamel surface.(1) Cigarette smoking is a public health problem. Many of the toxic substances present in cigarettes are in the tobacco plant or are produced during burning. Cigarette smoke contains ammonia, formaldehyde, arsenic, carbon monoxide, radioactive polonium, and many other potential disease-causing agents.(2) In addition to affecting the aesthetics of teeth, cigarette smoke contains various chemical agents that may cause surface alterations or structural changes when in contact to enamel, altering many important mechanical properties of the tooth.(3) The literature contains only a few studies (4,5) about the effect of cigarette smoke on the optical properties of esthetic restorative materials and dental structures when compared to the numerous studies(6,7) on the effect of coffee, red wine, tea, and other staining agents. Therefore, this study aimed to evaluate the effects of cigarette smoke on the color and enamel Knoop microhardness of the enamel. The hypothesis tested was that exposure to cigarette ©INTERNATIONAL JOURNAL OF DENTAL CLINICS VOLUME 3 ISSUE 4 2011 smoke alters the microhardness of enamel and would cause color changes in the samples during the time period under study. Materials and Methods Fifteen bovine incisors were cleaned and disinfected with thymol (Dinâmica, Piracicaba, São Paulo, Brazil) and submitted to an initial polishing with pumice (SS White LTDA; Rio de Janeiro, RJ, Brazil) and water. After separating the coronary portion by means of a double-faced diamond disc (KG Sorensen, Ind. Com. Ltda.; Barueri, SP, Brazil), enamel blocks of 25 mm2 were obtained using a precision saw (Isomet 1000; Buehler, Illinois, USA) and a high-concentration diamond disc (4” x 012 x ½, Buehler, Illinois, USA). The fragments were included, without covering the top with a polystyrene resin, to facilitate handling during planning (8,9) using silicon carbide emery-cloth of decreasing granulation (1200, 600, and 400) and surface polishing with felts with a diamond paste of decreasing granulation (1 and ¼ µm), greased with a specific oil (Arotec, Cotia; SP, Brazil). The samples were then washed for 15 minutes in an ultrasonic tub (Marconi, Piracicaba, São Paulo, Brazil) in order to remove any sludge present on the enamel surface, and then immersed in artificial saliva at 37°C.(10) Knoop Microhardness analysis:For the Knoop hardness evaluation, the indentations were made on the enamel surface using a Knoop indenter with a static load of 25g for 5 seconds with a microhardness tester (HMV-2000 Shimadzu, Tokyo, Japan).(11) Five consecutive and equidistant indentations were made in the 1
  2. 2. ISSN 0975-8437 INTERNATIONAL JOURNAL OF DENTAL CLINICS 2011:3(4):1-4 central region of each specimen at two times: before exposure to smoke and after exposure to smoke. To verify the microhardness, the specimens were positioned perpendicular to the indenter. The average of the five indentations was calculated and submitted to ANOVA and Tukey test (alpha of 0.05). Colorimetric Analysis: The color of each sample was measured with a spectrophotometer CM-700d (Konica Minolta Sensing Americas, Ramsey, New Jersey, USA) coupled with a cabin light (MM-1eUV/D65) and the data were subjected to interpretation by software OnColor QC Lite at two times: before and after exposure to tobacco smoke. The device was calibrated according to the manufacturer's instructions, and for each measurement, the sample was dried for 3 seconds with the help of absorbent paper in order to maintain the surface condition similar to that found in a clinical situation. (12) The color was measured by placing the sample on a black background with a color and brightness pattern, simulating a clinical condition.(13) Simulation of the act of smoking: For the smoke cigarette group the study employed the smoking machine developed by Department of Restorative Dentistry, Piracicaba Dental School - 2011 (registered under #01810012043 INPI – National Institute of Industrial Property) and permitted impregnation of pigments contained in cigarette smoke in the specimens of dental structures and restoration materials, in order to reproduce in vitro the smokers mouth cavity conditions. The machine works as it aspires and conducts smoke through glass cannulas aiming to allow it to circulate and deposit the chemical products on the specimen. This cycle is programed within a span of time that simulates smoke aspiration normally performed by a smoker with the duration of 3s. The temporizer permits the ambient air to be inhaled every 10s, simulating smoke exhaustion and afterward smoke elimination. The standard was the use of one pack of Marlboro (Philip Morris Brazil Ind. e Com. Ltda., Santa Cruz do Sul, RS, Brazil) cigarettes a day for each specimen during the period of 5 day. In the interval between one simulation and the other, the specimens were kept in artificial saliva at a constant temperature of 37°C. Every 24h, the specimens were washed with 250 mL of distilled water and reimmersed in fresh solution of artificial saliva to prevent sedimentation. After exposure to cigarette smoke, the samples were subjected to a prophylaxis ©INTERNATIONAL JOURNAL OF DENTAL CLINICS VOLUME 3 ISSUE 4 2011 procedure with pumice (SS White LTDA, Rio de Janeiro, Brazil) and water immersion in an ultrasonic tub (Marconi, Piracicaba, SP, Brazil) for 15 minutes.(10) Results Analysis of the Knoop microhardness: The final reading (T2) significantly differed from the initial reading (T1), which presented the lowest hardness values, as shown in Table 1. Time Average micro hardness (Pattern Error) Inicial 373.64 (22.99) A Final 315.16 (24.45) B Table 1: Means (SD) of the Knoop microhardness evaluation before and after exposure to smoke * Means followed by distinct letters differ by Tukey test (p ≤ 0.05). CIE Lab Colorimetric Analysis: After exposure of the samples to cigarette smoke, the values of color increased, as shown in Table 2. Color change ΔE (Pattern Error) Enamel 4.4* (1.6) * Indicates unacceptable value of color change (ΔE * ≥ 3.3) Table 2: Mean (SD) of color change ΔE evaluation before and after exposure to smoke Discussion In this study, a decrease in enamel microhardness after exposure to cigarette smoke was observed. Researchers have speculated that a change occurs in the spatial arrangement of hydroxyapatite crystals.(14) According to Palamara,(15) heat can modify the structure and morphology of crystals. During the act of inhaling cigarette smoke, the combustion can generate heat up to 950°C16, and the smoke generated is composed of thousands of toxic substances, such as carbon monoxide, ammonia, nickel, arsenic, and heavy metals,(2) which in addition to altering the color of dental materials and substrates may alter the surface hardness, as shown by the results of this study. The smoke of a cigarette contains on average 1 to 2μg of cadmium, and it is estimated that 0.1 to 0.2 mg per cigarette is inhaled. This chemical is not present naturally in the human body, so any concentration may be dangerous to one’s health,(14) and perhaps its presence in the oral cavity can alter the ultrastructure of dental tissues, maybe because some type of chemical bonding occurs. This could be an important factor that causes a decrease in the microhardness of enamel. This research also recorded the color changes in the enamel surface, as measured by the CIE Lab system. This system represents a 2
  3. 3. ISSN 0975-8437 INTERNATIONAL JOURNAL OF DENTAL CLINICS 2011:3(4):1-4 uniform color space with equal distances, corresponding to equally perceived color differences. (17) Many authors have reported that values of ΔE in the range of 2 to 3 are noticeable and that the value of 3.3 is critical for visual perception.(3) For colorimetric evaluation, the samples were subjected to prophylaxis with pumice and water so that no interference occurred in the readings caused by superficial sludge present after the test exposure to cigarette smoke.(10) In this study, exposure to cigarette smoke promoted a staining of the enamel surface in the range of 4.4 ΔE, which is considered to be a clinically unacceptable color change. These results are consistent with those of other studies, (6,18) which reported that staining by cigarette smoke was higher when compared to other types of pigments. According to Sulieman,(19) the distribution and intensity of staining is dependent on the type, amount, and duration of exposure to a pigmenting agent. In this study, the exposure of each sample to the smoke of 50 cigarettes over 5 days was sufficient to produce clinically noticeable color changes. Unfortunately, there is a paucity of published data that indicates a protocol for the time and amount of exposure to smoke in order to compare results. The hypotheses of this study were proven once the enamel surface microhardness was accepted, and a superficial enamel color change was observed after exposure to cigarette smoke. Conclusions Cigarette smoke led to a decrease in enamel microhardness and altered the color of the enamel, which was darker than a clinically acceptable condition. Authors Affiliations: 1. Mr. Carlos Eduardo dos Santos Bertold, DDS, MS, 2. Mr. Diogo de Azevedo Miranda, DDS, MS, 3. Mr. Eduardo José SouzaJúnior, DDS, MS, 4. Mr. Flávio Henrique Baggio Aguiar, DDS, MS, PhD, Full Professor, 5. Dr. Débora Alves Nunes Leite Lima, DDS, MS, Ph.D., Full Professor, 6. Rodrigo Lessa Ferreira, DDS, 7. Mr. Igor Claes - Undergraduate student of Dentistry, 8. Dr. José Roberto Lovadino, DDS, MS, PhD, Full Professor, Piracicaba Dental School, State University of Campinas, UNICAMP, São Paulo, Brazil. References 1. Kleter GA, Damen JJ, Buijs MJ, Ten Cate JM. Modification of amino acid residues in carious dentin matrix. Journal of Dental Research 1998;77(3):488-95. 2. Polydorou O, Mönting JS, Hellwig E, Auschill TM. Effect of in-office tooth bleaching on the ©INTERNATIONAL JOURNAL OF DENTAL CLINICS VOLUME 3 ISSUE 4 2011 microhardness of six dental esthetic restorative materials. Dental Materials 2007;23(2): 153-8. 3. Schulze KA, Marshall SJ, Gansky SA, Marshall GW. Color stability and hardness in dental composites after accelerated aging. Dental Materials 2003;19(7):612-9. 4. Bagheri R, Burrow MF, Tyas M. Influence of food-simulating solutions and surface finish on susceptibility to staining of aesthetic restorative materials. Journal of Dentistry 2005;33(5):389-98. 5. Satou N, Khan AM, Matsumae I, Satou J, Shintani H. In vitro color change of composite-based resins. Dental Materials 1989;5(6):384-7. 6. Raptis CN, Powers JM, Fan PL, Yu R. Staining of composite resins by cigarette smoke. Journal of Oral Rehabilitation 1982;9(4):367-71. 7. Rossie KM, Guggenheimer J. Thermally induced 'nicotine' stomatitis. A case report. Oral Surgery Oral Medicine Oral Pathology 1990;70(5):597-9. 8. Caldwell RC, Muntz ML, Gilmore RW, Pigman W. Microhardness studies of intact surface enamel. Journal of Dental Research 1957;36(5):732-8. 9. Newbrun E, Timberlake P, Pigman W. Changes in microhardness of enamel following treatment with lactate buffer. Journal of Dental Research 1959;38(2):293-300. 10. Lima DA, Silva AL, Aguiar FH, Liporoni PC, Munin E, Ambrosano GM, Lovadino JR. In vitro assessment of the effectiveness of whitening dentifrices for the removal of extrinsic tooth stains. Brazilian Oral Research 2008;22(2):106-11. 11. Fragoso LS, Lima DA, de Alexandre RS, Bertoldo CE, Aguiar FH, Lovadino JR. Evaluation of physical properties of enamel after microabrasion, polishing, and storage in artificial saliva. Biomedical Materials 2011;6(3):035001. 12. Lee YK, Lim BS, Powers JM. Color changes of dental resin composites by a salivary enzyme. Journal of Biomedical Materials Research Part B Applied Biomaterials 2004 ;70(1):66-72. 13. Buchalla W, Attin T, Hilgers RD, Hellwig E. The effect of water storage and light exposure on the color and translucency of a hybrid and a microfilled composite. Journal of Prosthetic Dentistry 2002;87(3):264-70. 14. Takeuchi CY, Corrêa-Afonso AM, Pedrazzi H, Dinelli W, Palma-Dibb RG. Deposition of lead and cadmium released by cigarette smoke in dental structures and resin composite. Microscopy Research and Technique 2010. 15. Palamara J, Phakey PP, Rachinger WA, Orams HJ. The ultrastructure of human dental enamel heat-treated in the temperature range 200 degrees 3
  4. 4. ISSN 0975-8437 INTERNATIONAL JOURNAL OF DENTAL CLINICS 2011:3(4):1-4 C to 600 degrees C. Journal of Dental Research 19. Sulieman M. An overview of tooth discoloration: 1987;66(12):1742-7. extrinsic, intrinsic and internalized stains. Dental 16. Craig RG & Powers JM. 2002. Restorative dental Update 2005;32(8):463-4, 466-8, 471. materials. St. Louis: Mosby. Address for Correspondence 17. Joiner A. Tooth colour: a review of the literature. Dr. Eduardo José Souza-Junio Department of Restoraive Dentistry, Journal of Dentistry 2004;32 Suppl 1:3-12. Dental Materials Area, 18. Wasilewski Mde S, Takahashi MK, Kirsten GA, Piracicaba Dental School, de Souza EM. Effect of cigarette smoke and State University of Campinas, whiskey on the color stability of dental São Paulo, Brazil. composites. American Journal of Dentistry Email: 2010;23(1):4-8. Source of Support: Nil, Conflict of Interest: None Declared ©INTERNATIONAL JOURNAL OF DENTAL CLINICS VOLUME 3 ISSUE 4 2011 4