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Penetration of etched enamel by bonding agents
EFFECTS OF PROVISIONAL
CEMENTING
AGENTS
4. The effects of provisional cementing agents are not restricted to cured resin. They also inhibit polymerization of added resin, which may be an important clinical consideration if a reline or repair of a provisional restoration is needed at a subsequent patient visit. Further study is needed to identify these interactions. We thank Dr. William M. Johnston for his assistance with the statistical evaluation and Dr. Ralph H. Rosenblum for his editorial assistance. The products used in this study were supplied by their manufacturers. whose assistance is appreciated.
REFERENCES 1. Civjan S, Huget EF, De Simon LB. Compatibility of resin composites with varnishes, Imers and bases [Abstract]. J Dent Res 1073;52:65.
Grajower R, Hirschfeld Z, Zalkind M. Compatibility of a composite resin with pulp insulating materials: a scanning electron microscope study. J F’RO~HET DENT 1974;32:70-7. Millstein PL, Nathanson D. Effect of eugenol and eugenol cements on cured composite resin. J PROSTHET DENT 1983; 50:211-5. Goodnight JH. Tests of hypothesis in fixed effects linear models. SAS Technical Report R-101. Gary. NC:SAS Institute Inc, 1978.
Reprint requeststo: DR. STEPHEN F. R~~EN~TIEL OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY COLUMBUS,OH 43210
Penetration of etched enamel by bonding agents H. Baharav, D.M.D.,* H. S. Cardash, B.D.S., L.D.S., R.C.S. (En@,** M. Helft, D.M.D.,*** and J. Langsam, M.Sc.*+** Tel Aviv University, The Maurice and Gabriela Goldschleger School of Dental Medicine, and Bar Ilan University, Tel Aviv, Israel
E
tching the enamel surface with phosphoric acid creates pores for the mechanical retention of bonding agents. Three types of etching patterns found after exposure of enamel to conditioning solutions have been described: type 1, preferential removal of prism core material leaving the periphery intact; type 2, periphery of the prisms dissolved, leaving the prism core relatively unaffected; and type 3, the etching pattern more random, corresponding to types 1 and 2 together with regions in which the pattern could not be related to prism morphology (Fig. l).’ Baharav et al.2 demonstrated that rubbing the enamel with a fine brush while applying the acid-etching agent enhances the decalcification of enamel. This continuousbrushing technique resulted in a more debris-free surface. Dissolution and reduction in size of the apatite crystals increased the enamel surface available for retention of the composite. In addition to the three types of etching pattern reported by Silverstone et al.,’ a pattern related to apatite crystal morphology was observed. This study was done to determine whether bonding agents can penetrate these small pores between the apatite crystals of the enamel prisms.
*Instructor,
Department of Oral Rehabilitation.
**Clinical Senior Lecturer, Department of Oral Rehabilitation. ***Head, Department of Oral Rehabilitation. ****Department of Life Science. THE JOURNAL
OF PROSTHEI’IC
DENTISTRY
MATERIAL
AND METHODS
Two extracted noncarious human maxillary premolars were stored in distilled water for 24 hours, cleaned with a prophylaxis brush and a water slurry of flour of pumice, and dried with compressed air. An etching agent (Esticid, Kulzer Inc., Friedrichsdorf, W. Germany) containing 35% phosphoric acid was applied to the buccal surface of one tooth. The etchant was continuously brushed for 30 seconds with a fine paint brush. The tooth was then washed with tap water for 30 seconds and dried with compressed air. The buccal surface was divided into three equal parts. Scotchbond (3M Dental Products Div., St. Paul, Minn.) bonding agent was applied to the mesial third of the etched enamel with a brush. A gentle stream of air was blown on the tooth from the center toward the mcsial part of the buccal surface to obtain a thin layer of bonding agent. The resin was polymerized with a visible light unit (Translux, Kulzer Inc.) for 40 seconds. Durafill bond (Kulzer Inc.), bonding agent was applied to the distal third of the buccal surface with the airstream directed distally and polymerized for 40 seconds with the visible light unit. The central third remained untreated after etching. The specimens were prepared for the scanning electron microscope @EM) and photographed. The second tooth was bisected vertically in a mesiodistal direction and the dentin was removed by grinding, leaving a shell of enamel approximately 1 mm thick. 33
BAHARAV
ET AL
Fig. 1. SEM micrograph showing three types of etching patterns of enamel. A, Type I; B,
type II C, type III. (Original magnification, X1000.)
Table I. Mean percentage weight of similar volumes of Durafill composite coated with Durafill and Scotchbond bonding agents after immersion in hydrochloric acid (N = 5) Composite + bonding agent
Mean % weight
Durafill t Duraflll Durafill t Scotchbond
99.45 99.22
Standard deviation
kO.38 k 0.25
The photographs were made adjacent to the last portion of the enamel to be dissolved by the hydrochloric acid. Ten samples of a similar volume of Durafill composite were cured. Five were coated with Durafill bond and five with Scotchbond bonding agent, cured, and weighed. The samples were immersed in 10% hydrochloric acid for 2 minutes, washed, dried, and reweighed. The composite samples were immersed for only 2 minutes, the estimated time of contact of the acid with the last remnant of the enamel.
RESULTS Fig. 2. SEM micrograph
perpendicular to buccal surface after etching for 30 seconds. (Original magniflcation ~5000; length of exposed area 18 a)
The buccal enamel was etched and the two bonding agents were applied as in the first tooth. In addition, a 1 mm layer of composite (Durafill, Kulzer Inc.) was applied and cured for 40 seconds with the visible light unit. The specimen was immersed for 20 minutes in a 10% solution of hydrochloric acid, washed in distilled water, dried, and prepared for SEM and photographed. 34
The central third of the premolar treated by acidetching alone is shown in Fig. 2. Dissolution of some apatite crystals occurred and the remaining crystals are reduced in size. The pores created between the crystals are available for retention of the bonding agent. The mesial third of the tooth painted with Scotchbond bonding agent after etching is demonstrated in Fig. 3. Islands of bonding agent fill the pores between the apatite crystals of the enamel prisms. A photograph of the distal third of the tooth painted with Durafill bond after etching is shown in Fig. 4. A similar pattern of Durafill bond penetrating pores between the apatite crystals is seen. JANUARY
1988
VOLUME
59
NUMBER
1
PENETRATION
OF ETCHED
ENAMEL
BY BONDING
AGENTS
Fig. 5. SEM micrograph of specimen of Durafill bonding agent after dissolution of enamel. A, Tag of Durafill bonding agent penetrating prism space. Arrow indicates Durafill bonding agent penetrating pores between apatite crystals. (Original magnification X5000.)
Fig. 3. SEM micrograph perpendicular to buccal surface after application of Scotchbond bonding agent. A, Islands of Scotchbond bonding agent; B, apatite crystals. (Original magnification x5000; length of exposed area 18 IL.)
Fig. 6. SEM micrograph of specimen of Scotchbond bonding agent after dissolution of enamel. Arrow indicates Scotchbond bonding agent penetrating pores between apatite crystals. (Original magnification x5000.)
Fig. 4. SEM micrograph perpendicular to buccal surface after application of Durafill bonding agent. A, Durafill bonding agent; B, apatite crystals. (Original magnification x5000; length of exposed area 18 II.)
Fig. 5 shows tags of Durafill bond protruding to the height of the prisms and slightly penetrating between the apatite crystals after decalcification of the enamel. Fig. 6 shows tags of Scotchbond bonding agent THE JOURNAL
OF PROSTHETIC
DENTISTRY
protruding to the level of the prisms and penetrating well between the enamel crystals after decalcification of the enamel. The weight of similar volume of samples of Durafill composite coated with Durafill bond and Scotchbond bonding agent after immersion in hydrochloric acid for 2 minutes is shown in Table I. DISCUSSION The continuous brushing technique used in this study to apply the etchant is in contradiction of Phillips) who suggested that the enamel surface should not be rubbed because this may damage the fragile enamel lattice work or simply
push the decalcified
material
back into the
pores that are being formed. Similarly, overetching must 35
BAHARAV
be avoided because a layer of a tenacious insoluble reaction product forms, which prevents tag formation. Fig. 2 shows enamel treated by the continuous brushing technique. Open pores are present and no deposition of insoluble products are visible on the surface. Penetration of the bonding agent into the microspaces between the apatite crystals requires intimate interfacial contact between the bonding agent and enamel. A liquid with a lower surface tension than the adherend serves this purpose. ‘85 A liquid of low viscosity is required to wet the enamel surface and flow between the apatite crystals. Dogon demonstrated that liquid resin of a viscosity less than 350 centipoise appeared to fill the spaces within the etched enamel prisms. When the contact angle between the surface of a drop of liquid and the surface of the adherend is small, wetting will occur.2*7 From Fig. 2, the dimensions of the pores between the apatite crystals can be estimated to range from 0.1 to 1 pm, creating doubt as to the ability of the bonding agent to enter and wet the walls of the apatite crystals. The photographs showing tips of the apatite crystals protruding through the bonding agent indicate that this has occurred (Figs. 3 and 4). Since a minimal weight loss occurred in the samples of composite coated with bonding agent, it may be assumed that the specimens of composite remaining after the dissolving of enamel were true negatives of the etched enamel. Figs. 5 and 6 showa difference in the wetting potential of the two bonding agents. Scotchbond bonding agent (Fig. 6) shows many more minitags, indicating better wetting properties than Durafill bond (Fig. 5). Durafill bond contains 40% microfiller, which may explain its reduced penetration.
ET AL
CONCLUSIONS 1. Scotchbond and Durafill bonding agents can penetrate pores created by continuous brushing with an acid-etching agent. 2. Scotchbond bonding agent demonstrated better wetting properties than Durafill bond. REFERENCES 1. Silverstone LM, Saxton CA, Dogon IL, Fejerskov 0. Variation in the pattern of acid-etching of human enamel examined by scanning electron microscopy. Caries Res 1975;9:373-87. 2. Baharav H, Cardash HS, Helft M, Langsam J. The continuous brushing acid-etch technique. J PROSTHET DENT 1987;57: 147-9. 3. Phillips RW. Skinner’s science of dental materials. 8th ed. Philadelphia: WB Saunders Co, 1982;239-40. 4. Zisman WA. Adhesive restorative dental materials. In Phillips RW, Ryge GB. Adhesive restorative dental materials. Springfield: Clearinghouse for federal scientific and technical information, 1961;176. 5. Zisman WA. Adhesive restorative dental materials, II. In Phillips RW, Ryge GB. Adhesive restorative dental materials, II. Washington, DC: Public Health Service Publication No. 1494, 1966;21. 6. Dogon IL. Studies demonstrating the need for an intermediary resin of low viscosity for an acid-etch technique. In Silverstone LM, Dogon IL, eds. Proceedings of an international symposium on the acid-etch technique. St. Paul: North Central Publishing co, 1975. 7. Zisman WA. Influence of constitution on adhesion. Ind Eng Chem 1963;55:19-38. Reprint requests to: DR. HAIM BAHARAV TEL AVIV UNIVERWY THE MAURICE AND GABRIELAGOLDSCHLECERSCHWL OF DENTAL MEDICINE RAMAT AVIV 69978 TEL AVIV. ISRAEL
A comparison of the equivalence of jaw and articulator movements Jose DOS Santos, Jr., D.D.S., M.S., Ph.D.,* and Major M. Ash, Jr., D.D.S., M.S.** University of Michigan, School of Dentistry, Ann Arbor, Mich.
T
o simulate mandibular movement is the primary purpose of an articulator. Effectiveness may be deter-
*Ass&ate Professor of Dentistry, Department of Occlusion. **Professor and Chairman, Department of Occlusion.
36
mined by comparison of superimposed pantographic tracings of jaw movements, as recorded from the patient, with analagous mechanical movements of the instrument.‘-’ This study investigated the differences in linear and angular paths of six different semiadjustable articulators JANUARY
1988
VOLUME
59
NUMBER
1
CEMENTING
AGENTS
4. The effects of provisional cementing agents are not restricted to cured resin. They also inhibit polymerization of added resin, which may be an important clinical consideration if a reline or repair of a provisional restoration is needed at a subsequent patient visit. Further study is needed to identify these interactions. We thank Dr. William M. Johnston for his assistance with the statistical evaluation and Dr. Ralph H. Rosenblum for his editorial assistance. The products used in this study were supplied by their manufacturers. whose assistance is appreciated.
REFERENCES 1. Civjan S, Huget EF, De Simon LB. Compatibility of resin composites with varnishes, Imers and bases [Abstract]. J Dent Res 1073;52:65.
Grajower R, Hirschfeld Z, Zalkind M. Compatibility of a composite resin with pulp insulating materials: a scanning electron microscope study. J F’RO~HET DENT 1974;32:70-7. Millstein PL, Nathanson D. Effect of eugenol and eugenol cements on cured composite resin. J PROSTHET DENT 1983; 50:211-5. Goodnight JH. Tests of hypothesis in fixed effects linear models. SAS Technical Report R-101. Gary. NC:SAS Institute Inc, 1978.
Reprint requeststo: DR. STEPHEN F. R~~EN~TIEL OHIO STATE UNIVERSITY COLLEGE OF DENTISTRY COLUMBUS,OH 43210
Penetration of etched enamel by bonding agents H. Baharav, D.M.D.,* H. S. Cardash, B.D.S., L.D.S., R.C.S. (En@,** M. Helft, D.M.D.,*** and J. Langsam, M.Sc.*+** Tel Aviv University, The Maurice and Gabriela Goldschleger School of Dental Medicine, and Bar Ilan University, Tel Aviv, Israel
E
tching the enamel surface with phosphoric acid creates pores for the mechanical retention of bonding agents. Three types of etching patterns found after exposure of enamel to conditioning solutions have been described: type 1, preferential removal of prism core material leaving the periphery intact; type 2, periphery of the prisms dissolved, leaving the prism core relatively unaffected; and type 3, the etching pattern more random, corresponding to types 1 and 2 together with regions in which the pattern could not be related to prism morphology (Fig. l).’ Baharav et al.2 demonstrated that rubbing the enamel with a fine brush while applying the acid-etching agent enhances the decalcification of enamel. This continuousbrushing technique resulted in a more debris-free surface. Dissolution and reduction in size of the apatite crystals increased the enamel surface available for retention of the composite. In addition to the three types of etching pattern reported by Silverstone et al.,’ a pattern related to apatite crystal morphology was observed. This study was done to determine whether bonding agents can penetrate these small pores between the apatite crystals of the enamel prisms.
*Instructor,
Department of Oral Rehabilitation.
**Clinical Senior Lecturer, Department of Oral Rehabilitation. ***Head, Department of Oral Rehabilitation. ****Department of Life Science. THE JOURNAL
OF PROSTHEI’IC
DENTISTRY
MATERIAL
AND METHODS
Two extracted noncarious human maxillary premolars were stored in distilled water for 24 hours, cleaned with a prophylaxis brush and a water slurry of flour of pumice, and dried with compressed air. An etching agent (Esticid, Kulzer Inc., Friedrichsdorf, W. Germany) containing 35% phosphoric acid was applied to the buccal surface of one tooth. The etchant was continuously brushed for 30 seconds with a fine paint brush. The tooth was then washed with tap water for 30 seconds and dried with compressed air. The buccal surface was divided into three equal parts. Scotchbond (3M Dental Products Div., St. Paul, Minn.) bonding agent was applied to the mesial third of the etched enamel with a brush. A gentle stream of air was blown on the tooth from the center toward the mcsial part of the buccal surface to obtain a thin layer of bonding agent. The resin was polymerized with a visible light unit (Translux, Kulzer Inc.) for 40 seconds. Durafill bond (Kulzer Inc.), bonding agent was applied to the distal third of the buccal surface with the airstream directed distally and polymerized for 40 seconds with the visible light unit. The central third remained untreated after etching. The specimens were prepared for the scanning electron microscope @EM) and photographed. The second tooth was bisected vertically in a mesiodistal direction and the dentin was removed by grinding, leaving a shell of enamel approximately 1 mm thick. 33
BAHARAV
ET AL
Fig. 1. SEM micrograph showing three types of etching patterns of enamel. A, Type I; B,
type II C, type III. (Original magnification, X1000.)
Table I. Mean percentage weight of similar volumes of Durafill composite coated with Durafill and Scotchbond bonding agents after immersion in hydrochloric acid (N = 5) Composite + bonding agent
Mean % weight
Durafill t Duraflll Durafill t Scotchbond
99.45 99.22
Standard deviation
kO.38 k 0.25
The photographs were made adjacent to the last portion of the enamel to be dissolved by the hydrochloric acid. Ten samples of a similar volume of Durafill composite were cured. Five were coated with Durafill bond and five with Scotchbond bonding agent, cured, and weighed. The samples were immersed in 10% hydrochloric acid for 2 minutes, washed, dried, and reweighed. The composite samples were immersed for only 2 minutes, the estimated time of contact of the acid with the last remnant of the enamel.
RESULTS Fig. 2. SEM micrograph
perpendicular to buccal surface after etching for 30 seconds. (Original magniflcation ~5000; length of exposed area 18 a)
The buccal enamel was etched and the two bonding agents were applied as in the first tooth. In addition, a 1 mm layer of composite (Durafill, Kulzer Inc.) was applied and cured for 40 seconds with the visible light unit. The specimen was immersed for 20 minutes in a 10% solution of hydrochloric acid, washed in distilled water, dried, and prepared for SEM and photographed. 34
The central third of the premolar treated by acidetching alone is shown in Fig. 2. Dissolution of some apatite crystals occurred and the remaining crystals are reduced in size. The pores created between the crystals are available for retention of the bonding agent. The mesial third of the tooth painted with Scotchbond bonding agent after etching is demonstrated in Fig. 3. Islands of bonding agent fill the pores between the apatite crystals of the enamel prisms. A photograph of the distal third of the tooth painted with Durafill bond after etching is shown in Fig. 4. A similar pattern of Durafill bond penetrating pores between the apatite crystals is seen. JANUARY
1988
VOLUME
59
NUMBER
1
PENETRATION
OF ETCHED
ENAMEL
BY BONDING
AGENTS
Fig. 5. SEM micrograph of specimen of Durafill bonding agent after dissolution of enamel. A, Tag of Durafill bonding agent penetrating prism space. Arrow indicates Durafill bonding agent penetrating pores between apatite crystals. (Original magnification X5000.)
Fig. 3. SEM micrograph perpendicular to buccal surface after application of Scotchbond bonding agent. A, Islands of Scotchbond bonding agent; B, apatite crystals. (Original magnification x5000; length of exposed area 18 IL.)
Fig. 6. SEM micrograph of specimen of Scotchbond bonding agent after dissolution of enamel. Arrow indicates Scotchbond bonding agent penetrating pores between apatite crystals. (Original magnification x5000.)
Fig. 4. SEM micrograph perpendicular to buccal surface after application of Durafill bonding agent. A, Durafill bonding agent; B, apatite crystals. (Original magnification x5000; length of exposed area 18 II.)
Fig. 5 shows tags of Durafill bond protruding to the height of the prisms and slightly penetrating between the apatite crystals after decalcification of the enamel. Fig. 6 shows tags of Scotchbond bonding agent THE JOURNAL
OF PROSTHETIC
DENTISTRY
protruding to the level of the prisms and penetrating well between the enamel crystals after decalcification of the enamel. The weight of similar volume of samples of Durafill composite coated with Durafill bond and Scotchbond bonding agent after immersion in hydrochloric acid for 2 minutes is shown in Table I. DISCUSSION The continuous brushing technique used in this study to apply the etchant is in contradiction of Phillips) who suggested that the enamel surface should not be rubbed because this may damage the fragile enamel lattice work or simply
push the decalcified
material
back into the
pores that are being formed. Similarly, overetching must 35
BAHARAV
be avoided because a layer of a tenacious insoluble reaction product forms, which prevents tag formation. Fig. 2 shows enamel treated by the continuous brushing technique. Open pores are present and no deposition of insoluble products are visible on the surface. Penetration of the bonding agent into the microspaces between the apatite crystals requires intimate interfacial contact between the bonding agent and enamel. A liquid with a lower surface tension than the adherend serves this purpose. ‘85 A liquid of low viscosity is required to wet the enamel surface and flow between the apatite crystals. Dogon demonstrated that liquid resin of a viscosity less than 350 centipoise appeared to fill the spaces within the etched enamel prisms. When the contact angle between the surface of a drop of liquid and the surface of the adherend is small, wetting will occur.2*7 From Fig. 2, the dimensions of the pores between the apatite crystals can be estimated to range from 0.1 to 1 pm, creating doubt as to the ability of the bonding agent to enter and wet the walls of the apatite crystals. The photographs showing tips of the apatite crystals protruding through the bonding agent indicate that this has occurred (Figs. 3 and 4). Since a minimal weight loss occurred in the samples of composite coated with bonding agent, it may be assumed that the specimens of composite remaining after the dissolving of enamel were true negatives of the etched enamel. Figs. 5 and 6 showa difference in the wetting potential of the two bonding agents. Scotchbond bonding agent (Fig. 6) shows many more minitags, indicating better wetting properties than Durafill bond (Fig. 5). Durafill bond contains 40% microfiller, which may explain its reduced penetration.
ET AL
CONCLUSIONS 1. Scotchbond and Durafill bonding agents can penetrate pores created by continuous brushing with an acid-etching agent. 2. Scotchbond bonding agent demonstrated better wetting properties than Durafill bond. REFERENCES 1. Silverstone LM, Saxton CA, Dogon IL, Fejerskov 0. Variation in the pattern of acid-etching of human enamel examined by scanning electron microscopy. Caries Res 1975;9:373-87. 2. Baharav H, Cardash HS, Helft M, Langsam J. The continuous brushing acid-etch technique. J PROSTHET DENT 1987;57: 147-9. 3. Phillips RW. Skinner’s science of dental materials. 8th ed. Philadelphia: WB Saunders Co, 1982;239-40. 4. Zisman WA. Adhesive restorative dental materials. In Phillips RW, Ryge GB. Adhesive restorative dental materials. Springfield: Clearinghouse for federal scientific and technical information, 1961;176. 5. Zisman WA. Adhesive restorative dental materials, II. In Phillips RW, Ryge GB. Adhesive restorative dental materials, II. Washington, DC: Public Health Service Publication No. 1494, 1966;21. 6. Dogon IL. Studies demonstrating the need for an intermediary resin of low viscosity for an acid-etch technique. In Silverstone LM, Dogon IL, eds. Proceedings of an international symposium on the acid-etch technique. St. Paul: North Central Publishing co, 1975. 7. Zisman WA. Influence of constitution on adhesion. Ind Eng Chem 1963;55:19-38. Reprint requests to: DR. HAIM BAHARAV TEL AVIV UNIVERWY THE MAURICE AND GABRIELAGOLDSCHLECERSCHWL OF DENTAL MEDICINE RAMAT AVIV 69978 TEL AVIV. ISRAEL
A comparison of the equivalence of jaw and articulator movements Jose DOS Santos, Jr., D.D.S., M.S., Ph.D.,* and Major M. Ash, Jr., D.D.S., M.S.** University of Michigan, School of Dentistry, Ann Arbor, Mich.
T
o simulate mandibular movement is the primary purpose of an articulator. Effectiveness may be deter-
*Ass&ate Professor of Dentistry, Department of Occlusion. **Professor and Chairman, Department of Occlusion.
36
mined by comparison of superimposed pantographic tracings of jaw movements, as recorded from the patient, with analagous mechanical movements of the instrument.‘-’ This study investigated the differences in linear and angular paths of six different semiadjustable articulators JANUARY
1988
VOLUME
59
NUMBER
1