Permeability Effects of Two Dentin Adhesive Systems Scott E. Hansen, D.D.S.” Edward J . Swift Jr., D.M.D., M.S. Keith V. Krell, D.D.S., M.S.
This in vitro study evaluated the effects of two dentin adhesive systems on dentin permeability.The XR-BondingSystem modifiesthe smear layer but does not open dentinal tubules. The Kanca or “total-etch” technique (phosphoric acid, Tenure A and B, Scotchbond 2 Adhesive) removes the smear layer and opens dentinal tubules. Despite these differences, both systems reduced dentin permeability in a similar manner. XR-Bond decreased permeability to 52% of the smear layer value, while total etching reduced permeability to 66% of that value.
B
acterial ingress around the margins of restorations can cause pulpal This is a particular concern with composite resins, because currently available dentin bonding agents do not completely and predictably inhibit microleakage when restoration margins are in dentin or c e m e n t ~ m .How~.~ ever, the potential adverse pulpal effectsof microleakage may be limited somewhat by the presence of smear layers, which form on dentin during cavity preparat i ~ n Smear .~ layers act as a natural “cavity liner” or protective barrier to seal dentinal tubules, reducing permeability and bacterial p e n e t r a t i ~ n .Smear ~ . ~ layers also reduce sensitivityby limitingfluid movementacross dentinal tubules. Recently, a new generation of dentin bonding systems has been introduced. Adhesion of these systems relies on alteration of the dentin surface by a chemical conditioner or primer.8-11These agents react with or remove the smear layer, and therefore could alter dentin permeability. Bowen et al used an acidifled ferric oxalate conditioner, a surface-activeresinmonomer (NTG-GMA),and a resin coupling agent (PMDM)to develop strong bonds between composite resin and dentin in vitro.l 2 . I 3 Pashley et al reported that Bowen’sbonding system, especially the ferric oxalate conditioner, reduces dentin permeability.14 Tenure (Den-Mat Corporation, Santa Maria, CA), a commercialversion of Bowen’s system, is different from the original system tested by Pashley’s group. Tenure
Dentin Conditioner, which contains 2.5% nitric acid and aluminum oxalate, removes virtually the entire smear layer and opens the dentinal tubules.$ The subsequent steps of Bowen’s in vitro bonding sequence have been combined and shortened for clinical convenience.16 Pashley et al recently reported that Tenure Conditioner does not reduce dentin permeability as much as acidified femc oxalate.I7 The effects of other dentin bonding systems on permeability have not been reported. The purpose of our study, therefore, was to evaluate the effect of two representative bonding systems on dentin permeability in vitro. One of the adhesives, the XR-Bonding System (KerrManufacturing Company, Romulus, MI) modifies the smear layer without opening the dentinal tubules. l6 The other system, commonly called the “total-etch” or Kanca technique, uses phosphoric acid to completely remove the smear layer and open the tubules. This version of the “total-etch”technique also includes components of the Tenure and Scotchbond 2 (3M Dental Products Division, St. Paul, MrJl dentin bonding system~.’~,~~
MATERIALS AND METHODS Thirty recently extracted human molars, which had been stored in distilled water and thymol, were randomly assigned to five groups. A section of midcoronal dentin, 1.0 k 0.2 mm thick, was taken from each tooth using a low-speed diamond blade. These dentin sections were etched on both sides for 60 s with 37% phosphoric acid to remove the smear layers created by the diamond saw. The etched dentin discs were mounted in a splitchamber device so that permeability could be measured as a function of hydraulic conductance.20Aphosphatebuffered saline (PBS) solution was forced under pres-
‘Prfvate Practice. Davenport, Iowa
t Associate Professor, Departmentof Operative Dentistry, The Universityof Iowa. Iowa City. Iowa tprlvate Practice, Des Moines. Iowa Address reprint requests to Edward J. Swift Jr.. D.M.D., Department of Operative Dentistry, The University of Iowa, Iowa City. Iowa 52242 8 1992 Decker Periodicals Inc.
169
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, NUMBER 5 September/October 1992
of each disc was different, subsequent permeability values were expressed as a percentage of the maximum value. Thus, each dentin disc served as its own control. The permeability of each treated disc was also expressed as a percentage of its smear layer permeability for further analysis. The data were analyzed using a n analysis of variance of repeated measures with the SAS statistical software package (SAS Institute, Cary, NC). Duncan's multiple range test (alpha = 0.5) was used to rank the permeability effects of the various surface treatments.
sure (15 psi) from a reservoir through polyethylene tubing and a 25-yLmicropipette into the bottom of this split-chamber device. The fluid passed through the dentinal tubules to the top half of the split chamber. Two rubber O-rings limited the tested surface area to 0.178 cm2. The rate of movement (mm/min) of a small air bubble through the micropipette was measured with a millimeter ruler. The fluid movement was measured and recorded at 2-min intervals for 8 min. These measurements were averaged and used to calculate permeability using the hydraulic conductance (Lp)formula described by Pashley.20,21 Standard smear layers were then created on the occlusal surface of each dentin disc by rubbing (handpressure) on 320-grit aluminum oxide abrasive paper in a figure-8 pattern. After measuring the smear layer permeability of each disc, the occlusal dentin surfaces were treated as follows:
RESULTS The results are summarized in Table 1.The permeability values in the table are expressed as percentages of the smear layer values. Smear layers caused an average reduction in dentin permeability of 49.4 k 27.5% from baseline (etched)values. Only one surface treatment increased the hydraulic conductance of dentin. Application of phosphoric acid (Group T-1) increased Lp to 273.9 f 148.6% of the smear layer value or to 134.89 f 89.8% of its baseline level. All of the other surface treatments reduced dentin permeability to some extent. The reductions caused by components of the XR-Bonding System were somewhat greater than those caused by the Kanca technique. However, there was no statistical difference between these surface treatments (at alpha = 0.05). Within the specific treatment groups, only the complete =-Bonding System (Group X-2)showed a statistically signiflcant (p c .02) decrease from its smear layer value.
Group X-1. (n = 6) XR-Primer, an ethanol solution of a phosphonated dimethacrylate resin, was applied to the surface with multiple brush strokes for 30 s. The surface was dried with compressed air, and the primer was cured for 10 s with a Max (L.D. Caulk, Milford, DE) visible light curing unit. Group X-2.(n = 6) m-Primer was applied in the same manner. ThenXR-Bond(phosphonated Bis-GMA) was applied in a thin layer to the surface and light cured for 20 s. Group T-1. (n = 6)The dentin surface was etched with 37% phosphoric acid for 20 s, washed with water for 15 s, and dried with compressed air. Group T-2. (n = 6)After acid-etching in the same manner, components of the Tenure dentin bonding system were used to treat the dentin. Tenure A (NTGGMA in acetone) and Tenure B (PMDM in acetone) were mixed and applied twice to the etched surfaces. Each mixture was left undisturbed on the surface for 15 s. Then the surface was gently air dried to remove unevaporated solvent. Group T-3. (n = 6, etching and application of the Tenure solutions, Scotchbond 2 Adhesive (Bis-GMA and HEMA) was applied in an even layer and light cured for 20 s.
DISCUSSION As expected, smear layers decreased the permeability of dentin specimens. Etching of the specimens with phosphoric acid, the initial step in the Kanca technique, removed the smear layer and increased dentin permeability to approximately three times its smear layer value in our study. Hydraulic conductance Table 1. Effects of Multiple-StepDentin Bonding Systems on Denin Permeability
Group
The permeability of each disc was measured again after surface treatment was completed. The overall effect of each system on permeability was shown by the data from the two groups which represented the entire dentin bonding systems (groups X-2 and T-3). Permeability data for each intermediate step provided information regard% the Of that step to the overall effect of the bonding system. The hydraulic conductance value of each etched dentin disc was considered the maximum (i.e., 100%) permeability of that sample. Because the permeability
X-1 X-2 T-1 T-2 T-3
Treatment XR-Primer XR-Primer, XR-Bond H,P04 H,PO,. NTG-GMA + PMDM H,P04. NTG-GMA + PMDM, Bk-GMA + HEMA
Dentin Permeabilitv
Duncan Growid
76.4f 22.2 52.1 f 43.8. 273.9f148.6t 85.9f 68.3 65.7f 62.5
A A
B A A
Permeabllltyvaluesareexpressedas percentagesof smear layer permeabillty. 'Significantly less than smear layer value (p < ,021. t Slgnlficantly greater than smear layer value (p < ,051. t Group with same letter are not slgnkantly dfferent (p > .05).
170
Permeability of Two Dentin Adhesive Systems
was even greater than the baseline Lp value. This was one-half to two-thirds of the smear layer permeability. due in part to thinning of the dentin discs when the Kanca's total-etch technique, which removes the smear sections were abraded to create standard smear laylayer and opens the dentin tubules, had a n effect ers." similar to that of the XR-Bonding System, which does Subsequent application of NTG-GMA and PMDM not open the tubules. The effects were similar despite reduced permeability to 85.9%of the smear layer value. the fact that the first step of the Kanca technique is NTG-GMA and PMDM polymerize spontaneously to phosphoric acid etching of dentin, which greatly inform a thin resin coating of the dentin ~ u r f a c e . ~The ~ " ~ creases permeability. complete Kanca technique, which also includes Scotchbond 2 Adhesive, reduced permeability further, Acknowledgment to 65.7%of the smear value. Scotchbond 2 Adhesive is This project was supported by Henry Schein. Inc. as a 1989 a relatively hydrophilic bonding agent (Bis-GMA and American Association of Dental Research (AADR) Student ReHEMA),which copolymenizeswiththe NTG-GMA/PMDM search Fellowship. resin l a ~ e r . ~ O , ~ ~ The XR-Bonding System modifles the smear layer, REFERENCES but does not aggressively open the dentinal tubules. Both the primer and adhesive components are lightactivated resins that coat the dentin surface.l 6 The XR1. Brsinnstr6m M. Communication between the oral cavity Bonding System also decreased dentin permeabilityand dental pulp associated with restorative treatment. to 52.1% of the smear layer value. The primer and Oper Dent 1984: 9:57-68. 2. BrsinnstrGm M. The cause of postoperative sensitivity and bonding resin contributed similar percentages of this its prevention. J Endodont 1986: 12:475-481. overall reduction. Crim GA. Chapman KW. Prevention of marginal leakage by 3. Our results indicate that both dentin bonding sysfour dentinal adhesives. Gen Dent 1986 34:235-236. tems decrease dentin permeability. Although the XR4. Barkmeier WW. Cooley RL.Resin adhesive systems: invitro Bonding System may have been slightly more effective, evaluation of dentin bond strength and marginal the Kanca technique also reduced fluid flow through microleakage. J Esthet Dent 1989; 1:67-72. dentin. 5. SchuleinTM.The smear layer on dentin. A status report for The use of phosphoric acid for deliberate etching of the American Journal of Dentistry. Am J Dent 1988: 1:264270. dentin is a controversialtopic that has recently attract6. Vojinovic 0, Nyborg H. BriinnsMm M. Acid treatment of ed widespread attention. Some early clinical reports cavities under resin fillings: bacterial growth in dentinal and in uitro data indicate that etchingmay be a safe and tubules and pulpal reactions. J Dent Res 1973: 52: 1189effective means to facilitate dentin adhesion.18~192627 1193. Many clinicians are currently using the Kanca method 7. Pashley DH. Smear layer: physiological considerations. or other adhesives that rely on phosphoric acid etching Oper Dent 1984; Suppl3:13-29. of dentin, such as ClearfilPhotoBond(Kuraray/J.Morita, 8. Munksgaard EC. Asmussen E. Bond strength between Tustin, CA),All-Bond (Bisco, Downer's Grove, IL),and dentin and restorative resins mediated by mixtures of HEMA and glutaraldehyde. J Dent Res 1984: 63:1087PowerBond (Cosmedent. Chicago, IL). In addition, sev1089. eral other commercial dentin bonding systems include Gwinnett AJ. Aluminum oxalate for dentin bonding. An 9. acidic conditioners that remove the smear layer and SEM study. Am J Dent 1988: 1 5 8 . etch dentin in much the same manner. 10. Gwinnett AJ. Dentin bonding systems: the latest generaStill, more research is needed to clarify the effects of tion. J Esthet Dent 1989: 1 5 9 . dentin etching. For example,the claimed "total seal"has 11. Erickson RL. Mechanism and clinical implications of bond not been substantiated by long-term clinical research.28 formationfor twodentin bonding systems. Am J Dent 1989; Another concern voiced by critics of the Kanca or total2:117-123. 2. Bowen RL. Cobb EN, Rapson JE. Adhesive bonding of etch technique is that etching completely removes the smear layer and opens and widens dentinal t ~ b u l e s . ~ ~ . ~ ~various materials to hard tooth tissues: improvement of bond strength to dentin. J Dent Res 1982: 61:1070-1076. Open tubules allow an outward flow of fluid and provide 3 . Bowen RL. Cobb EN. A method for bonding to dentin and a potential pathway for ingress of b a ~ t e r i a .However, ~.~ enamel. J Am Dent Assoc 1983: 107:734-736. our study shows that the total-etch technique limits 4. Pashley DH. Derkson GD. Tao L,Derkson M, Kalathoor J. permeability almost as much as an adhesive that does The effects of a multi-step dentin bonding system on dentin not aggressively remove the smear layer. Of course, permeability. Dent Mater 1988; 4:60-63. clinicalperformance could be quite different from these 15. Strassler HE, Weiner S.Oxalate dentin bonding. Compend in uitro results. Contin Educ Dent 1988; 998-108. 16. Barkmeier WW, Cooley FU.Shear bond strength, microleakage and SEM study of the XR Bond adhesive CONCLUSIONS system. Am J Dent 1989: 2: 111-1 15. 17. PashleyDH. Andringa HJ. Eichmiller F. Effects of ferric and aluminum oxalates on dentin permeability. Am J Dent 1991: 4:123-126.
The dentin bonding system evaluated in this in uitro study reduced dentin permeability to approximately 171
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, NUMBER 5 September/October 1992
24. Barkmeier WW, Gwinnett AJ. A scanning electron microscopy study of dentin and enamel surfaces treated with three new resin adhesive systems. Compend Contin Educ Dent 1989: 1:145-152. 25. Kanca J. Microleakage of the Cluma system. Am J Dent 1990; 3:105-107. 26. Kanca J. One-year evaluation of a dentin-enamel bonding system. J Esthet Dent 1990: 2: 100-103. 27. Bertolotti RL. Total etch-the rational dentin bonding protocol. J Esthet Dent 1991: 3:1-6. 28. Albers HF, ed. Dentin-resin bonding. ADEPT Report 1990; 1:33-44. 29. Br&mstrtjm M. Removal ofthe dentinal smear layer (letter). Quintessence Int 1990; 21:425-426. 30. B r d s t r t j m M. Removal ofthe dentinal smear layer (letter). Quintessence Int 1990; 21:769-770.
18. Kanca J. Bonding to tooth structure: arational rationalefor a clinical protocol. J Esthet Dent 1989; 1:135-138. 19. Kanca J. A method for bonding to tooth structure using phosphoric acid as a dentin-enamelconditioner. Quintessence lnt 1991; 22:285290. 20. Pashley DH, Michelich V, Kehl T. Dentin permeability: effects of smear layer removal. J Prosthet Dent 1981; 46:531-537. 2 1. Tao L. Pashley DH. The relationshipbetween dentin bond strengths and dentin permeability. Dent Mater 1989: 5:133-139. 22. Bowen RL, Marjenhoff WA. Development of an adhesive system for bonding to hard tooth tissues. J Esthet Dent 1991; 3:86-90. 23. Cwinnett A J . Aluminum oxalate for dentin bonding. An SEM study. Am J Dent 1988; 1 5 8 .
172
This in vitro study evaluated the effects of two dentin adhesive systems on dentin permeability.The XR-BondingSystem modifiesthe smear layer but does not open dentinal tubules. The Kanca or “total-etch” technique (phosphoric acid, Tenure A and B, Scotchbond 2 Adhesive) removes the smear layer and opens dentinal tubules. Despite these differences, both systems reduced dentin permeability in a similar manner. XR-Bond decreased permeability to 52% of the smear layer value, while total etching reduced permeability to 66% of that value.
B
acterial ingress around the margins of restorations can cause pulpal This is a particular concern with composite resins, because currently available dentin bonding agents do not completely and predictably inhibit microleakage when restoration margins are in dentin or c e m e n t ~ m .How~.~ ever, the potential adverse pulpal effectsof microleakage may be limited somewhat by the presence of smear layers, which form on dentin during cavity preparat i ~ n Smear .~ layers act as a natural “cavity liner” or protective barrier to seal dentinal tubules, reducing permeability and bacterial p e n e t r a t i ~ n .Smear ~ . ~ layers also reduce sensitivityby limitingfluid movementacross dentinal tubules. Recently, a new generation of dentin bonding systems has been introduced. Adhesion of these systems relies on alteration of the dentin surface by a chemical conditioner or primer.8-11These agents react with or remove the smear layer, and therefore could alter dentin permeability. Bowen et al used an acidifled ferric oxalate conditioner, a surface-activeresinmonomer (NTG-GMA),and a resin coupling agent (PMDM)to develop strong bonds between composite resin and dentin in vitro.l 2 . I 3 Pashley et al reported that Bowen’sbonding system, especially the ferric oxalate conditioner, reduces dentin permeability.14 Tenure (Den-Mat Corporation, Santa Maria, CA), a commercialversion of Bowen’s system, is different from the original system tested by Pashley’s group. Tenure
Dentin Conditioner, which contains 2.5% nitric acid and aluminum oxalate, removes virtually the entire smear layer and opens the dentinal tubules.$ The subsequent steps of Bowen’s in vitro bonding sequence have been combined and shortened for clinical convenience.16 Pashley et al recently reported that Tenure Conditioner does not reduce dentin permeability as much as acidified femc oxalate.I7 The effects of other dentin bonding systems on permeability have not been reported. The purpose of our study, therefore, was to evaluate the effect of two representative bonding systems on dentin permeability in vitro. One of the adhesives, the XR-Bonding System (KerrManufacturing Company, Romulus, MI) modifies the smear layer without opening the dentinal tubules. l6 The other system, commonly called the “total-etch” or Kanca technique, uses phosphoric acid to completely remove the smear layer and open the tubules. This version of the “total-etch”technique also includes components of the Tenure and Scotchbond 2 (3M Dental Products Division, St. Paul, MrJl dentin bonding system~.’~,~~
MATERIALS AND METHODS Thirty recently extracted human molars, which had been stored in distilled water and thymol, were randomly assigned to five groups. A section of midcoronal dentin, 1.0 k 0.2 mm thick, was taken from each tooth using a low-speed diamond blade. These dentin sections were etched on both sides for 60 s with 37% phosphoric acid to remove the smear layers created by the diamond saw. The etched dentin discs were mounted in a splitchamber device so that permeability could be measured as a function of hydraulic conductance.20Aphosphatebuffered saline (PBS) solution was forced under pres-
‘Prfvate Practice. Davenport, Iowa
t Associate Professor, Departmentof Operative Dentistry, The Universityof Iowa. Iowa City. Iowa tprlvate Practice, Des Moines. Iowa Address reprint requests to Edward J. Swift Jr.. D.M.D., Department of Operative Dentistry, The University of Iowa, Iowa City. Iowa 52242 8 1992 Decker Periodicals Inc.
169
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, NUMBER 5 September/October 1992
of each disc was different, subsequent permeability values were expressed as a percentage of the maximum value. Thus, each dentin disc served as its own control. The permeability of each treated disc was also expressed as a percentage of its smear layer permeability for further analysis. The data were analyzed using a n analysis of variance of repeated measures with the SAS statistical software package (SAS Institute, Cary, NC). Duncan's multiple range test (alpha = 0.5) was used to rank the permeability effects of the various surface treatments.
sure (15 psi) from a reservoir through polyethylene tubing and a 25-yLmicropipette into the bottom of this split-chamber device. The fluid passed through the dentinal tubules to the top half of the split chamber. Two rubber O-rings limited the tested surface area to 0.178 cm2. The rate of movement (mm/min) of a small air bubble through the micropipette was measured with a millimeter ruler. The fluid movement was measured and recorded at 2-min intervals for 8 min. These measurements were averaged and used to calculate permeability using the hydraulic conductance (Lp)formula described by Pashley.20,21 Standard smear layers were then created on the occlusal surface of each dentin disc by rubbing (handpressure) on 320-grit aluminum oxide abrasive paper in a figure-8 pattern. After measuring the smear layer permeability of each disc, the occlusal dentin surfaces were treated as follows:
RESULTS The results are summarized in Table 1.The permeability values in the table are expressed as percentages of the smear layer values. Smear layers caused an average reduction in dentin permeability of 49.4 k 27.5% from baseline (etched)values. Only one surface treatment increased the hydraulic conductance of dentin. Application of phosphoric acid (Group T-1) increased Lp to 273.9 f 148.6% of the smear layer value or to 134.89 f 89.8% of its baseline level. All of the other surface treatments reduced dentin permeability to some extent. The reductions caused by components of the XR-Bonding System were somewhat greater than those caused by the Kanca technique. However, there was no statistical difference between these surface treatments (at alpha = 0.05). Within the specific treatment groups, only the complete =-Bonding System (Group X-2)showed a statistically signiflcant (p c .02) decrease from its smear layer value.
Group X-1. (n = 6) XR-Primer, an ethanol solution of a phosphonated dimethacrylate resin, was applied to the surface with multiple brush strokes for 30 s. The surface was dried with compressed air, and the primer was cured for 10 s with a Max (L.D. Caulk, Milford, DE) visible light curing unit. Group X-2.(n = 6) m-Primer was applied in the same manner. ThenXR-Bond(phosphonated Bis-GMA) was applied in a thin layer to the surface and light cured for 20 s. Group T-1. (n = 6)The dentin surface was etched with 37% phosphoric acid for 20 s, washed with water for 15 s, and dried with compressed air. Group T-2. (n = 6)After acid-etching in the same manner, components of the Tenure dentin bonding system were used to treat the dentin. Tenure A (NTGGMA in acetone) and Tenure B (PMDM in acetone) were mixed and applied twice to the etched surfaces. Each mixture was left undisturbed on the surface for 15 s. Then the surface was gently air dried to remove unevaporated solvent. Group T-3. (n = 6, etching and application of the Tenure solutions, Scotchbond 2 Adhesive (Bis-GMA and HEMA) was applied in an even layer and light cured for 20 s.
DISCUSSION As expected, smear layers decreased the permeability of dentin specimens. Etching of the specimens with phosphoric acid, the initial step in the Kanca technique, removed the smear layer and increased dentin permeability to approximately three times its smear layer value in our study. Hydraulic conductance Table 1. Effects of Multiple-StepDentin Bonding Systems on Denin Permeability
Group
The permeability of each disc was measured again after surface treatment was completed. The overall effect of each system on permeability was shown by the data from the two groups which represented the entire dentin bonding systems (groups X-2 and T-3). Permeability data for each intermediate step provided information regard% the Of that step to the overall effect of the bonding system. The hydraulic conductance value of each etched dentin disc was considered the maximum (i.e., 100%) permeability of that sample. Because the permeability
X-1 X-2 T-1 T-2 T-3
Treatment XR-Primer XR-Primer, XR-Bond H,P04 H,PO,. NTG-GMA + PMDM H,P04. NTG-GMA + PMDM, Bk-GMA + HEMA
Dentin Permeabilitv
Duncan Growid
76.4f 22.2 52.1 f 43.8. 273.9f148.6t 85.9f 68.3 65.7f 62.5
A A
B A A
Permeabllltyvaluesareexpressedas percentagesof smear layer permeabillty. 'Significantly less than smear layer value (p < ,021. t Slgnlficantly greater than smear layer value (p < ,051. t Group with same letter are not slgnkantly dfferent (p > .05).
170
Permeability of Two Dentin Adhesive Systems
was even greater than the baseline Lp value. This was one-half to two-thirds of the smear layer permeability. due in part to thinning of the dentin discs when the Kanca's total-etch technique, which removes the smear sections were abraded to create standard smear laylayer and opens the dentin tubules, had a n effect ers." similar to that of the XR-Bonding System, which does Subsequent application of NTG-GMA and PMDM not open the tubules. The effects were similar despite reduced permeability to 85.9%of the smear layer value. the fact that the first step of the Kanca technique is NTG-GMA and PMDM polymerize spontaneously to phosphoric acid etching of dentin, which greatly inform a thin resin coating of the dentin ~ u r f a c e . ~The ~ " ~ creases permeability. complete Kanca technique, which also includes Scotchbond 2 Adhesive, reduced permeability further, Acknowledgment to 65.7%of the smear value. Scotchbond 2 Adhesive is This project was supported by Henry Schein. Inc. as a 1989 a relatively hydrophilic bonding agent (Bis-GMA and American Association of Dental Research (AADR) Student ReHEMA),which copolymenizeswiththe NTG-GMA/PMDM search Fellowship. resin l a ~ e r . ~ O , ~ ~ The XR-Bonding System modifles the smear layer, REFERENCES but does not aggressively open the dentinal tubules. Both the primer and adhesive components are lightactivated resins that coat the dentin surface.l 6 The XR1. Brsinnstr6m M. Communication between the oral cavity Bonding System also decreased dentin permeabilityand dental pulp associated with restorative treatment. to 52.1% of the smear layer value. The primer and Oper Dent 1984: 9:57-68. 2. BrsinnstrGm M. The cause of postoperative sensitivity and bonding resin contributed similar percentages of this its prevention. J Endodont 1986: 12:475-481. overall reduction. Crim GA. Chapman KW. Prevention of marginal leakage by 3. Our results indicate that both dentin bonding sysfour dentinal adhesives. Gen Dent 1986 34:235-236. tems decrease dentin permeability. Although the XR4. Barkmeier WW. Cooley RL.Resin adhesive systems: invitro Bonding System may have been slightly more effective, evaluation of dentin bond strength and marginal the Kanca technique also reduced fluid flow through microleakage. J Esthet Dent 1989; 1:67-72. dentin. 5. SchuleinTM.The smear layer on dentin. A status report for The use of phosphoric acid for deliberate etching of the American Journal of Dentistry. Am J Dent 1988: 1:264270. dentin is a controversialtopic that has recently attract6. Vojinovic 0, Nyborg H. BriinnsMm M. Acid treatment of ed widespread attention. Some early clinical reports cavities under resin fillings: bacterial growth in dentinal and in uitro data indicate that etchingmay be a safe and tubules and pulpal reactions. J Dent Res 1973: 52: 1189effective means to facilitate dentin adhesion.18~192627 1193. Many clinicians are currently using the Kanca method 7. Pashley DH. Smear layer: physiological considerations. or other adhesives that rely on phosphoric acid etching Oper Dent 1984; Suppl3:13-29. of dentin, such as ClearfilPhotoBond(Kuraray/J.Morita, 8. Munksgaard EC. Asmussen E. Bond strength between Tustin, CA),All-Bond (Bisco, Downer's Grove, IL),and dentin and restorative resins mediated by mixtures of HEMA and glutaraldehyde. J Dent Res 1984: 63:1087PowerBond (Cosmedent. Chicago, IL). In addition, sev1089. eral other commercial dentin bonding systems include Gwinnett AJ. Aluminum oxalate for dentin bonding. An 9. acidic conditioners that remove the smear layer and SEM study. Am J Dent 1988: 1 5 8 . etch dentin in much the same manner. 10. Gwinnett AJ. Dentin bonding systems: the latest generaStill, more research is needed to clarify the effects of tion. J Esthet Dent 1989: 1 5 9 . dentin etching. For example,the claimed "total seal"has 11. Erickson RL. Mechanism and clinical implications of bond not been substantiated by long-term clinical research.28 formationfor twodentin bonding systems. Am J Dent 1989; Another concern voiced by critics of the Kanca or total2:117-123. 2. Bowen RL. Cobb EN, Rapson JE. Adhesive bonding of etch technique is that etching completely removes the smear layer and opens and widens dentinal t ~ b u l e s . ~ ~ . ~ ~various materials to hard tooth tissues: improvement of bond strength to dentin. J Dent Res 1982: 61:1070-1076. Open tubules allow an outward flow of fluid and provide 3 . Bowen RL. Cobb EN. A method for bonding to dentin and a potential pathway for ingress of b a ~ t e r i a .However, ~.~ enamel. J Am Dent Assoc 1983: 107:734-736. our study shows that the total-etch technique limits 4. Pashley DH. Derkson GD. Tao L,Derkson M, Kalathoor J. permeability almost as much as an adhesive that does The effects of a multi-step dentin bonding system on dentin not aggressively remove the smear layer. Of course, permeability. Dent Mater 1988; 4:60-63. clinicalperformance could be quite different from these 15. Strassler HE, Weiner S.Oxalate dentin bonding. Compend in uitro results. Contin Educ Dent 1988; 998-108. 16. Barkmeier WW, Cooley FU.Shear bond strength, microleakage and SEM study of the XR Bond adhesive CONCLUSIONS system. Am J Dent 1989: 2: 111-1 15. 17. PashleyDH. Andringa HJ. Eichmiller F. Effects of ferric and aluminum oxalates on dentin permeability. Am J Dent 1991: 4:123-126.
The dentin bonding system evaluated in this in uitro study reduced dentin permeability to approximately 171
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, NUMBER 5 September/October 1992
24. Barkmeier WW, Gwinnett AJ. A scanning electron microscopy study of dentin and enamel surfaces treated with three new resin adhesive systems. Compend Contin Educ Dent 1989: 1:145-152. 25. Kanca J. Microleakage of the Cluma system. Am J Dent 1990; 3:105-107. 26. Kanca J. One-year evaluation of a dentin-enamel bonding system. J Esthet Dent 1990: 2: 100-103. 27. Bertolotti RL. Total etch-the rational dentin bonding protocol. J Esthet Dent 1991: 3:1-6. 28. Albers HF, ed. Dentin-resin bonding. ADEPT Report 1990; 1:33-44. 29. Br&mstrtjm M. Removal ofthe dentinal smear layer (letter). Quintessence Int 1990; 21:425-426. 30. B r d s t r t j m M. Removal ofthe dentinal smear layer (letter). Quintessence Int 1990; 21:769-770.
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