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Ultrasonic versus high-speed cavity preparation: Analysis of increases in pulpal temperature and time to complete preparation
Ultrasonic versus high-speed cavity preparation: Analysis of increases in pulpal temperature and time to complete preparation Aleska Dias Vanderlei, DDS, MS,a Alexandre Luiz Souto Borges, DDS, MS, PhD,b Bruno Neves Cavalcanti, DDS, MS, PhD,c and Sigmar Mello Rode, DDS, MS, PhDd São Paulo State University at São José dos Campos-UNESP, São Paulo, Brazil; Ibirapuera University, São Paulo, Brazil Statement of problem. The use of ultrasonic tips has become an alternative for cavity preparation. However, there are concerns about this type of device, particularly with respect to intrapulpal temperatures and cavity preparation time. Purpose. The purpose of this study was to analyze pulpal temperature increases generated by an ultrasonic cavity preparation with chemical vapor deposition (CVD) tips, in comparison to preparation with a high-speed handpiece with a diamond rotary cutting instrument. The time required to complete the cavity preparation with each system was also evaluated. Material and methods. Thermocouples were positioned in the pulp chamber of 20 extracted human third molars. Slot-type cavities (3 x 3 x 2 mm) were prepared on the buccal and the lingual surfaces of each tooth. The test groups were: high-speed cavity preparation with diamond rotary cutting instruments (n=20) and ultrasonic cavity preparation with CVD points (n=20). During cavity preparation, the increases in pulpal temperature, and the time required for the preparation, were recorded and analyzed by Student’s t test for paired samples (α=.05). Results. The average pulpal temperature increases were 4.3°C for the high-speed preparation and 3.8°C for the ultrasonic preparation, which were statistically similar (P=.052). However, significant differences were found (P<.001) for the time expended (3.3 minutes for the high-speed bur and 13.77 minutes for the ultrasound device). Conclusions. The intrapulpal temperatures produced during cavity preparation by ultrasonic tips versus high-speed bur preparation were similar. However, the use of the ultrasonic device required 4 times longer for the completion of a cavity preparation. (J Prosthet Dent 2008;100:107-109)
Clinical Implications
Pulpal temperature increases generated by a high-speed handpiece or an ultrasonic tip are not sufficiently high to cause pulp damage. The longer time expended with the ultrasonic tip must be considered when selecting the cavity preparation device. The use of high-speed handpieces has been the primary choice for cavity preparation. However, some dental patients fear this type of cavity preparation device, due to the noise and vibration.1 Additionally, the use
of high-speed handpieces requires professional skill and, if the devices are not used properly, they can harm dental tissues, even when used only on the enamel or dentin.2,3 Pulpal damage during cavity preparation is
a concern because increases in pulpal temperatures above 5.5°C can result in pulpal necrosis.4,5 Heat must be minimized by the use of conservative preparation techniques,6-8 such as intermittent cutting, low loads on the
Resident, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos-UNESP. Assistant Professor, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos CamposUNESP. c Assistant Professor, Biodentistry Postgraduate Program, Ibirapuera University. d Associate Professor, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos CamposUNESP. a
b
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Volume 100 Issue 2 handpiece, new, sharp instruments, and the use of an air-water spray.6,9,10 Recently, new cavity preparation devices have been developed. Among them are lasers that can be used safely11,12 and with increased patient acceptance.1 However, these devices are expensive and are not suitable for all types of preparations, such as those necessary to retain prostheses. Thus, ultrasonic devices are a good alternative, since they do not produce the high-pitched sound that annoys patients and are less expensive than lasers. Although ultrasonic devices have been studied since 1960,13 this type of device has become popular in the last decade, since the newer systems are more efficient and less traumatic.14,15 Associated with the development of ultrasonic devices, a new type of instrument, using chemical vapor diamond deposition (CVD), has been shown to be more efficient and durable.16 This study compared increases in pulpal temperature generated by an ultrasonic cavity preparation with CVD tips to those produced by a high-speed handpiece with a diamond rotary cutting instrument. The time periods required to complete cavity preparations with the 2 cutting systems were also compared. The null hypotheses tested were that neither instrument would cause harmful pulpal temperature increases and that the 2 instruments would require equivalent time to complete cavity preparations.
MATERIAL AND METHODS The methods used here have been previously used in several other studies.5-10 This study was conducted with the approval of the Ethics and Re-
search Committee, São Paulo State University. Twenty extracted human third molars were stored in distilled water until use. Then, the roots were cut off, pulp tissues were removed, and the buccal and lingual surfaces were reduced to standardize all enamel/dentin thickness at 3.0 mm, as measured by a pincer gauge with 0.01-mm accuracy (Bio-Art, São Carlos, Brazil). This gauge had one point inserted in the pulp chamber and the other positioned on the buccal surface of the teeth. All teeth received slot-type preparations in lingual and buccal surfaces, standardized for the width (3.0 mm), length (3.0 mm), and depth (2.0 mm), resulting in 40 preparations, 20 slots for each group. The burs were marked in 2.0-mm increments, allowing for a dentin thickness of 1.0 mm for all teeth after preparation. Preparation width and length were standardized using a template made of carbon copy paper. A type J thermocouple (Ecil, Sorocaba, Brazil) was positioned in the pulp chamber, filled with a heat conductor (Implastec, Votorantim, Brazil). The thermocouple was held in place with provisional cement (Cavit; 3M ESPE, Seefeld, Germany), and the crown segments were placed in putty impression material (Zetaplus; Zhermack SpA, Badia Polesine, Italy) to facilitate handling. Thermocouples were linked to an analog-digital converter (Raynger MX4+; Raytek Corp, Santa Cruz, Calif ) connected to a computer that recorded the readings with specific software (IR Graph, v. 1.02; Raytek Corp). The high-speed cavity preparation was performed with a high-speed handpiece (SUPERtorque 625, KaVo,
Joinville, Brazil) with a mediumcoarse-grit diamond rotary cutting instrument (1093; KG Sorensen, Barueri, Brazil). The preparation technique was ideal,6 with low pressure on the handpiece and intermittent cutting: 1 second of preparation followed by 1 second of rest. The water flow used was 45 ml/min. In the other group, a 28-kHz ultrasonic device (Profi I AS Ceramic; Dabi Atlante, Ribeirao Preto, Brazil) was used. It was cooled with refrigerated water (20 ml/min) and used mediumcoarse-grit CVD points (82137-C12F; CVDentus, São José dos Campos, Brazil). The same operator prepared all cavities and recording of time began, for each preparation, when the bur or tip touched the tooth. The graphs of changes in pulpal temperature versus time generated by the software were analyzed and the initial temperature values (T0) and the maximal temperature values (Tmax) were used, providing the increase in temperature value (∆T), according to the formula: ∆T=Tmax-T0. The increases in pulpal temperature and time expended to prepare the cavity were analyzed by the Student’s t test for paired samples (α=.05).
RESULTS The results of temperature increase and time expended are summarized in Table I. The average temperature increase for the high-speed preparation was 4.27°C and 3.82°C for the ultrasonic cavity preparation. The Student’s t test for paired samples did not demonstrate significant differences between the groups (P=.052). Time to complete the cavity prepara-
Table I. Temperature increase and expended time for each group Time Expended (Min)
Temperature (°C) Mean (SD)*
Min/Max
High-speed
4.27 (0.54)a
3.4/4.9
Ultrasound
3.82 (0.75)a
3.0/4.9
P .052
Mean (SD)*
Min/Max
3.28 (0.60)a
2.6/4.5
13.77 (1.36)b
11.8/15.3
P <.001
*Results of paired t test: values identified by different lowercase letters in same column are significantly different (P<.05)
The Journal of Prosthetic Dentistry
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August 2008 tion was 3 minutes for the high-speed handpiece, while the ultrasonic device required almost 14 minutes. For time to complete the preparation, significant differences were found (P<.001).
DISCUSSION The results of this study do not support rejection of the first null hypothesis, that both instruments produce similar pulpal temperature when used properly. The pulpal temperatures were in the safe range, below 5.5°C.4 However, the second null hypothesis, that there would be no difference in preparation time, was rejected. Cavity preparation can be performed with different types of devices. Most of them result in increases in the intrapulpal temperature. The current study evaluated ultrasonic cavity preparation with CVD points and found that the ultrasonic instrument increased the mean intrapulpal temperature by 3.82°C, and the greatest increase was recorded as 4.9°C, which is not enough to cause pulp damage.5 Moreover, when compared to a highspeed handpiece, it was observed that both devices generated similar amounts of heat, and the greatest value for the high-speed handpiece group was also 4.9°C. Thermocouples are generally used for testing intrapulpal temperature increases, and several studies have shown them to be reliable, with reproducible results.4-12 In the present study, they were used as previously described,12 and the increases in pulpal temperature of 4.27°C are compatible with the literature for high-speed cavity preparation.4,6,7,12 Ultrasonic cavity preparation may be a good option since it produces less noise, provides better access to cavities and cavity cleaning, and demonstrates lower wear of the tips during use. The time required for a complete ultrasonic cavity preparation was sig-
Ozturk et al
nificantly higher than that required for preparation using a high-speed handpiece. In this study, 13.77 minutes were necessary for ultrasonic device preparation, approximately 4 times the time expended for the same preparation with high-speed cutting (3.28 minutes). Certainly, more professional skill is required for the operation of high-speed handpieces, which could have lowered the time expended with this device, but the time factor must be considered, especially if large cavities must be prepared. This study has several limitations. First, in vitro simulation of the clinical situation is difficult, since the absence of pulp tissue and blood flow in vitro prevents the dissipation of the generated heat, causing overestimation of the actual temperature in the tissue. Despite this limitation, it is important that new cutting devices be analyzed to determine their potential to harm the tissues. Thus, studies observing the effects of ultrasound cavity preparation on dentin and enamel, and analyzing the effects of this preparation on restorative procedures, are in progress to complement the present study.
CONCLUSIONS Within the limitations of this in vitro study, it was concluded that the ultrasonic tips induced the same temperature increases as the high-speed handpiece evaluated. However, the time required to complete the cavity preparation was significantly higher (4 times) for the ultrasound group.
REFERENCES 1. Keller U, Hibst R, Geurtsen W, Schilke R, Heidemann D, Klaiber B, et al. Erbium:YAG laser application in caries therapy. Evaluation of patient perception and acceptance. J Dent 1998;26:649-56. 2. Pashey DH, Liewehr FR. Structure and function of the dentin-pulp complex. In: Cohen S, Hargreaves KM. Pathways of the pulp. 9th ed. St Louis: Mosby; 2005. p. 41156.
3. Goodis HE, Pashley DH, Stabholtz A. Pulpal effects of thermal and mechanical irritants. In: Hargreaves KM, Seltzer S, Goodis HE, editors. Seltzer and Bender´s dental pulp. Chicago: Quintessence; 2002. p. 371-88. 4. Zach L, Cohen G. Thermogenesis in operative techniques. Comparisons of four methods. J Prosthet Dent 1962;12:977-84. 5. Zach L, Cohen G. Pulp response to externally applied heat. Oral Surg Oral Med Oral Pathol 1965;19:515-30. 6. Cavalcanti BN, Otani C, Rode SM. Highspeed cavity preparation techniques with different water flows. J Prosthet Dent 2002;87:158-61. 7. Laforgia PD, Milano V, Morea C, Desiate A. Temperature change in the pulp chamber during complete crown preparation. J Prosthet Dent 1991;65:56-61. 8. Ottl P, Lauer HC. Temperature response in the pulpal chamber during ultrahigh-speed tooth preparation with diamond burs of different grit. J Prosthet Dent 1998;80:129. 9. Lauer HC, Kraft E, Rothlauf W, Zwingers T. Effects of the temperature of cooling water during high-speed and ultrahighspeed tooth preparation. J Prosthet Dent 1990;63:407-14. 10.Liao WM, Taira M, Ohmoto K, Shintani H, Yamaki M. Studies on dental high-speed cutting. J Oral Rehabil 1995;22:67-72. 11.Burkes EJ Jr, Hoke J, Gomes E, Wolbarsht M. Wet versus dry enamel ablation by Er: YAG laser. J Prosthet Dent 1992;67:847-51. 12.Cavalcanti BN, Lage-Marques JL, Rode SM. Pulpal temperature increases with Er:YAG laser and high-speed handpieces. J Prosthet Dent 2003;90:447-51. 13.Langeland K, Langeland LK. Cutting procedures with minimized trauma. J Am Dent Assoc 1968;76:991-1005. 14.Banerjee A, Watson TF, Kidd EA. Dentine caries excavation: a review of current clinical techniques. Br Dent J 2000;188:476-82. 15.Schulein TM. The era of high speed development in dentistry. J Hist Dent 2002;50:131-7. 16.Carvalho CA, Fagundes TC, Barata TJ, Trava-Airoldi VJ, Navarro MF. The use of CVD diamond burs for ultraconservative cavity preparations: a report of two cases. J Esthet Restor Dent 2007;19:19-28. Corresponding author: Dr Alexandre Luiz Souto Borges Departamento de materiais dentários e prótese Av. Eng. Francisco José Longo, 777 São José dos Campos – SP 12245-000 BRAZIL Fax: 55-12-3947-9000 E-mail: [email protected] Copyright © 2008 by the Editorial Council for The Journal of Prosthetic Dentistry.
Clinical Implications
Pulpal temperature increases generated by a high-speed handpiece or an ultrasonic tip are not sufficiently high to cause pulp damage. The longer time expended with the ultrasonic tip must be considered when selecting the cavity preparation device. The use of high-speed handpieces has been the primary choice for cavity preparation. However, some dental patients fear this type of cavity preparation device, due to the noise and vibration.1 Additionally, the use
of high-speed handpieces requires professional skill and, if the devices are not used properly, they can harm dental tissues, even when used only on the enamel or dentin.2,3 Pulpal damage during cavity preparation is
a concern because increases in pulpal temperatures above 5.5°C can result in pulpal necrosis.4,5 Heat must be minimized by the use of conservative preparation techniques,6-8 such as intermittent cutting, low loads on the
Resident, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos Campos-UNESP. Assistant Professor, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos CamposUNESP. c Assistant Professor, Biodentistry Postgraduate Program, Ibirapuera University. d Associate Professor, Department of Dental Materials and Prosthodontics, São Paulo State University at São José dos CamposUNESP. a
b
Vanderlei et al
108
Volume 100 Issue 2 handpiece, new, sharp instruments, and the use of an air-water spray.6,9,10 Recently, new cavity preparation devices have been developed. Among them are lasers that can be used safely11,12 and with increased patient acceptance.1 However, these devices are expensive and are not suitable for all types of preparations, such as those necessary to retain prostheses. Thus, ultrasonic devices are a good alternative, since they do not produce the high-pitched sound that annoys patients and are less expensive than lasers. Although ultrasonic devices have been studied since 1960,13 this type of device has become popular in the last decade, since the newer systems are more efficient and less traumatic.14,15 Associated with the development of ultrasonic devices, a new type of instrument, using chemical vapor diamond deposition (CVD), has been shown to be more efficient and durable.16 This study compared increases in pulpal temperature generated by an ultrasonic cavity preparation with CVD tips to those produced by a high-speed handpiece with a diamond rotary cutting instrument. The time periods required to complete cavity preparations with the 2 cutting systems were also compared. The null hypotheses tested were that neither instrument would cause harmful pulpal temperature increases and that the 2 instruments would require equivalent time to complete cavity preparations.
MATERIAL AND METHODS The methods used here have been previously used in several other studies.5-10 This study was conducted with the approval of the Ethics and Re-
search Committee, São Paulo State University. Twenty extracted human third molars were stored in distilled water until use. Then, the roots were cut off, pulp tissues were removed, and the buccal and lingual surfaces were reduced to standardize all enamel/dentin thickness at 3.0 mm, as measured by a pincer gauge with 0.01-mm accuracy (Bio-Art, São Carlos, Brazil). This gauge had one point inserted in the pulp chamber and the other positioned on the buccal surface of the teeth. All teeth received slot-type preparations in lingual and buccal surfaces, standardized for the width (3.0 mm), length (3.0 mm), and depth (2.0 mm), resulting in 40 preparations, 20 slots for each group. The burs were marked in 2.0-mm increments, allowing for a dentin thickness of 1.0 mm for all teeth after preparation. Preparation width and length were standardized using a template made of carbon copy paper. A type J thermocouple (Ecil, Sorocaba, Brazil) was positioned in the pulp chamber, filled with a heat conductor (Implastec, Votorantim, Brazil). The thermocouple was held in place with provisional cement (Cavit; 3M ESPE, Seefeld, Germany), and the crown segments were placed in putty impression material (Zetaplus; Zhermack SpA, Badia Polesine, Italy) to facilitate handling. Thermocouples were linked to an analog-digital converter (Raynger MX4+; Raytek Corp, Santa Cruz, Calif ) connected to a computer that recorded the readings with specific software (IR Graph, v. 1.02; Raytek Corp). The high-speed cavity preparation was performed with a high-speed handpiece (SUPERtorque 625, KaVo,
Joinville, Brazil) with a mediumcoarse-grit diamond rotary cutting instrument (1093; KG Sorensen, Barueri, Brazil). The preparation technique was ideal,6 with low pressure on the handpiece and intermittent cutting: 1 second of preparation followed by 1 second of rest. The water flow used was 45 ml/min. In the other group, a 28-kHz ultrasonic device (Profi I AS Ceramic; Dabi Atlante, Ribeirao Preto, Brazil) was used. It was cooled with refrigerated water (20 ml/min) and used mediumcoarse-grit CVD points (82137-C12F; CVDentus, São José dos Campos, Brazil). The same operator prepared all cavities and recording of time began, for each preparation, when the bur or tip touched the tooth. The graphs of changes in pulpal temperature versus time generated by the software were analyzed and the initial temperature values (T0) and the maximal temperature values (Tmax) were used, providing the increase in temperature value (∆T), according to the formula: ∆T=Tmax-T0. The increases in pulpal temperature and time expended to prepare the cavity were analyzed by the Student’s t test for paired samples (α=.05).
RESULTS The results of temperature increase and time expended are summarized in Table I. The average temperature increase for the high-speed preparation was 4.27°C and 3.82°C for the ultrasonic cavity preparation. The Student’s t test for paired samples did not demonstrate significant differences between the groups (P=.052). Time to complete the cavity prepara-
Table I. Temperature increase and expended time for each group Time Expended (Min)
Temperature (°C) Mean (SD)*
Min/Max
High-speed
4.27 (0.54)a
3.4/4.9
Ultrasound
3.82 (0.75)a
3.0/4.9
P .052
Mean (SD)*
Min/Max
3.28 (0.60)a
2.6/4.5
13.77 (1.36)b
11.8/15.3
P <.001
*Results of paired t test: values identified by different lowercase letters in same column are significantly different (P<.05)
The Journal of Prosthetic Dentistry
Ozturk et al
109
August 2008 tion was 3 minutes for the high-speed handpiece, while the ultrasonic device required almost 14 minutes. For time to complete the preparation, significant differences were found (P<.001).
DISCUSSION The results of this study do not support rejection of the first null hypothesis, that both instruments produce similar pulpal temperature when used properly. The pulpal temperatures were in the safe range, below 5.5°C.4 However, the second null hypothesis, that there would be no difference in preparation time, was rejected. Cavity preparation can be performed with different types of devices. Most of them result in increases in the intrapulpal temperature. The current study evaluated ultrasonic cavity preparation with CVD points and found that the ultrasonic instrument increased the mean intrapulpal temperature by 3.82°C, and the greatest increase was recorded as 4.9°C, which is not enough to cause pulp damage.5 Moreover, when compared to a highspeed handpiece, it was observed that both devices generated similar amounts of heat, and the greatest value for the high-speed handpiece group was also 4.9°C. Thermocouples are generally used for testing intrapulpal temperature increases, and several studies have shown them to be reliable, with reproducible results.4-12 In the present study, they were used as previously described,12 and the increases in pulpal temperature of 4.27°C are compatible with the literature for high-speed cavity preparation.4,6,7,12 Ultrasonic cavity preparation may be a good option since it produces less noise, provides better access to cavities and cavity cleaning, and demonstrates lower wear of the tips during use. The time required for a complete ultrasonic cavity preparation was sig-
Ozturk et al
nificantly higher than that required for preparation using a high-speed handpiece. In this study, 13.77 minutes were necessary for ultrasonic device preparation, approximately 4 times the time expended for the same preparation with high-speed cutting (3.28 minutes). Certainly, more professional skill is required for the operation of high-speed handpieces, which could have lowered the time expended with this device, but the time factor must be considered, especially if large cavities must be prepared. This study has several limitations. First, in vitro simulation of the clinical situation is difficult, since the absence of pulp tissue and blood flow in vitro prevents the dissipation of the generated heat, causing overestimation of the actual temperature in the tissue. Despite this limitation, it is important that new cutting devices be analyzed to determine their potential to harm the tissues. Thus, studies observing the effects of ultrasound cavity preparation on dentin and enamel, and analyzing the effects of this preparation on restorative procedures, are in progress to complement the present study.
CONCLUSIONS Within the limitations of this in vitro study, it was concluded that the ultrasonic tips induced the same temperature increases as the high-speed handpiece evaluated. However, the time required to complete the cavity preparation was significantly higher (4 times) for the ultrasound group.
REFERENCES 1. Keller U, Hibst R, Geurtsen W, Schilke R, Heidemann D, Klaiber B, et al. Erbium:YAG laser application in caries therapy. Evaluation of patient perception and acceptance. J Dent 1998;26:649-56. 2. Pashey DH, Liewehr FR. Structure and function of the dentin-pulp complex. In: Cohen S, Hargreaves KM. Pathways of the pulp. 9th ed. St Louis: Mosby; 2005. p. 41156.
3. Goodis HE, Pashley DH, Stabholtz A. Pulpal effects of thermal and mechanical irritants. In: Hargreaves KM, Seltzer S, Goodis HE, editors. Seltzer and Bender´s dental pulp. Chicago: Quintessence; 2002. p. 371-88. 4. Zach L, Cohen G. Thermogenesis in operative techniques. Comparisons of four methods. J Prosthet Dent 1962;12:977-84. 5. Zach L, Cohen G. Pulp response to externally applied heat. Oral Surg Oral Med Oral Pathol 1965;19:515-30. 6. Cavalcanti BN, Otani C, Rode SM. Highspeed cavity preparation techniques with different water flows. J Prosthet Dent 2002;87:158-61. 7. Laforgia PD, Milano V, Morea C, Desiate A. Temperature change in the pulp chamber during complete crown preparation. J Prosthet Dent 1991;65:56-61. 8. Ottl P, Lauer HC. Temperature response in the pulpal chamber during ultrahigh-speed tooth preparation with diamond burs of different grit. J Prosthet Dent 1998;80:129. 9. Lauer HC, Kraft E, Rothlauf W, Zwingers T. Effects of the temperature of cooling water during high-speed and ultrahighspeed tooth preparation. J Prosthet Dent 1990;63:407-14. 10.Liao WM, Taira M, Ohmoto K, Shintani H, Yamaki M. Studies on dental high-speed cutting. J Oral Rehabil 1995;22:67-72. 11.Burkes EJ Jr, Hoke J, Gomes E, Wolbarsht M. Wet versus dry enamel ablation by Er: YAG laser. J Prosthet Dent 1992;67:847-51. 12.Cavalcanti BN, Lage-Marques JL, Rode SM. Pulpal temperature increases with Er:YAG laser and high-speed handpieces. J Prosthet Dent 2003;90:447-51. 13.Langeland K, Langeland LK. Cutting procedures with minimized trauma. J Am Dent Assoc 1968;76:991-1005. 14.Banerjee A, Watson TF, Kidd EA. Dentine caries excavation: a review of current clinical techniques. Br Dent J 2000;188:476-82. 15.Schulein TM. The era of high speed development in dentistry. J Hist Dent 2002;50:131-7. 16.Carvalho CA, Fagundes TC, Barata TJ, Trava-Airoldi VJ, Navarro MF. The use of CVD diamond burs for ultraconservative cavity preparations: a report of two cases. J Esthet Restor Dent 2007;19:19-28. Corresponding author: Dr Alexandre Luiz Souto Borges Departamento de materiais dentários e prótese Av. Eng. Francisco José Longo, 777 São José dos Campos – SP 12245-000 BRAZIL Fax: 55-12-3947-9000 E-mail: [email protected] Copyright © 2008 by the Editorial Council for The Journal of Prosthetic Dentistry.