JOURNAL OF ESTHETIC DENTISTRY VOLUME 4. SUPPLEMENT 1992
6. Chen RCS, Chan DCN, Chan KC. A quantitative study of finishing and polishing techniques for a composite. J Prosthet Dent 1988; 59:292-297. 7. Boghosian AA. Randolph RG. J e w s VJ. Rotary instrument finishing of microfilled and small-particle hybrid composite resins. J Am Dent Assoc 1987; 115:299-301. 8. Goldstein GR.Waknine S.Surface roughness evaluation of composite resin polishing techniques. Quintessence Int 1989; 20:199-204. 9. Zar JH. Biostatistical analysis. 2nd Ed. Englewood Cliffs, NJ:Prentice-Hall, 1984. 10. Xin YI Yu MM, Wieczkowski G, Davis EL, Joynt FU3. The influence of finishing technique on microleakage.J Esthet Dent 1990; 2: 142-144.
REFERENCES 1. Stoddard J W , Johnson GH. An evaluation of polishing agents for composite resins. J Prosthet Dent 1991; 65: 491-495. 2. Herrgott A-ML. Ziemiecki TL, Dennison JB. An evaluation of different composite resin systems finished with various abrasives. J Am Dent Assoc 1989; 119:72!3-732. 3. Northeast SE. van Noort R. Surface characteristics of finished composite resins. Dent Mater 1988; 4:278-288. AHL, Chan CA. The polishabilityof posterior compos4. T~an ites. J Prosthet Dent 1989: 61:138-146. 5. Eide R 'Met AB. Finishing and polishing of composites. Acta Odontol Scand 1988; 46:307-312.
Marginal Leakage of a New Adhesive Restorative System: A Preliminary In Vivo Investigation Marco Ferrari, D.D.S.," Werner J . Finger, D.D.S., Ph.D.1 and Andrea Gesi, D.D.S.
The efficacy of newly developed adhesive restorative materials is commonly described by in uitro test results such as bond strength and microleakage data. Due to the inconsistency often found between in uitro testing and in uiuoperfomance, the purpose of the present investigationwas to restore teeth scheduled for extraction in uivowith an experimentalrestorative bonding system and to evaluate the microleakage of the restorations by common laboratory techniques following extraction after 3 months of clinical service. Two restorations were placed in each of seven anterior teeth, one in the middle of the labial enamel portion and the other labially extending over the cementoenameljunction (CEJ). Six of the seven fillings completely surrounded by enamel showed no microleakage. However, two of the restorations crossing the C W revealed microleakage originating from the cervical margins. In spite of the small number of flllinEls assessed, the experimental enamel-dentin adhesive compound tested is preliminarily considered a promising new system.
T
he function of adhesive restorative materials is to achieve a firm and consistent adaptation between cavity wall and restoration. Insufacientbondingstrength may result in total or partial debonding of the filling. Such debonding is primarily caused by the polymeriza-
tion contraction of restorative resins, and by repetitive thermal and/or mechanical stresses acting on the bonding i n t e r f a ~ e . ~ Consecutively, .~ marginal opening and the presence of gaps may lead to bacterial or toxin invasion along the cavity wall. The possible consequences are formation of caries, adverse pulp reactions, and marginal staining of the r e s t o r a t i ~ n .Recently, ~.~ an experimentaldentoenamel bonding agentwas presented by Kubo et al.s This compound was reported to micromechanically bond composite restorative resins to conditioned enamel and dentin. According to the authors, a resin-impregnated mne in inter- and peritubular dentin is readily achieved due to the compounds outstanding wetting of and penetration into acid-conditioned dentin.
'Assistant Professor. Siena University.School of Dentistry. Departmentof ConservativeDentistry. Siena. Italy: t Professor. Universityofhchen. Dental School. Departmentof ProstheticDentism and Dental Materials and Department of Clinical Research and Dental Materials Sclence. Bayex Dental. Dormagen. Germany; *Instructor. Siena University. School of Dentistry, Siena. Italy Address reprint requests to Dr. Manx, Fermi. Piazza Attla 19, 57125 Livorno. Italy 0 1992 Decker PeriodicalsInc.
32
Marginal Leakage of New Adhesive Restorative System
possible microleakage gateways generated during the time of clinical service of the experimental adhesive restorations.
MATERIALS AND METHODS Seven volunteer patients with one severely periodontally compromised anterior tooth each (four upper incisors and three upper canines), which had not received previous restorative treatment and which was scheduled for extraction, agreed to join the trial. As shown in Figures 1 and 2, circular, V-shaped cavities with a n approximate diameter of 3 mm and a maximum depth of 2 mm were cut under copious waterspray with a diamond tip mounted in a turbine handpiece. A cavosurface angle of 120 to 140 degrees was prepared along the entire cavity margin. While the incisal cavity (type 1)was surrounded by enamel, the cervical cavity (type 2) was located at the cementoenameljunction with half of the cavity margin in enamel and half in root cementum. Following cavity preparation a rubber dam was applied, and the tooth was rinsed and dried prior to a 30-second conditioning treatment of the cavity and a small area of the peripheral unprepared tooth surface. The conditioning solution, Bayer D 666/2 (aqueous solution of oxalic acid, Al-nitrate and glycine;batch: SPK 409/ l),was applied with a soaked cotton pellet under a light dabbing action. According to the manufacturer the purpose of this pretreatment is ( 1)to remove the smear layer produced a s a result of the preparation and (2)to condition enamel and dentin for wetting with and penetration of the adhesive substance into the exposed surface for micromechanical retention of the restoration. The preparation was then carefully rinsed with water for 10 seconds and blown dry with a gentle stream of compressed air from the dental unit for another 5 to 10 seconds. This procedure was followed by application with a soaked pellet of the experimental adhesive, Bayer D 667/2 (aqueous solution of N-methacryloyloxy-ethylN-methyl-formamide,Bis-GMA,acetic acid and ethanol: batch: SPK 410/1), to the entire cavity wall for 30 seconds before the cavity was gently air dried. The microfilled light-curing composite resin Pekalux (Bayer Dental, Leverkusen, Germany, batch: 1154 G) was inserted by a syringe from preloaded tubes (PLT)in three increments. Each increment was separately light activated for 20 seconds. Prior to activation of the Anal increment a transparent matrix was placed for contouring and as an effective barrier for oxygen to prevent inhibition of polymerization at the free surface of the restorative resin. Immediately after curing, the restorations were finished with dry Sof-flex disks (3M. St. Paul, MN). and 80 to 110days later the teeth were extracted. Because of the mobility of the periodontally weakened teeth, extraction was possible without exerting severe bending stresses. The samples were washed with deionized water and immediately transferred in an aqueous 1% Chloramin solution for storage at ambient temperature (approxi-
Figure 1. V-shaped class V cavities are located in the labioenamel portion (type 1) and at the cementoenameljunction (type 2) of anterior teeth of the upperjaw. The circular cavities have a n approximate diameter of 3 mm.
After polymexizationthis hybrid layer acts as an effective coupling site between the cavity wall and the restorative resin. The limitation of the article mentioned is that the data presented are at best suited for a hypothetical prediction of clinical ~ e r f o m a n c e This . ~ holds true generally for in uitro investigations of the efficacy of adhesive restorative materials, in particular when nonhuman teeth are used for testing.8 Therefore the objective of the present trial was to outline and to try a testing procedure involving teeth scheduled for extraction from volunteer patients. This method makes it possible with conventional tracer solution methods to investigate, on extracted, restored teeth,
Figure 2. Buccoling~dsectionthrough the crown of the tooth and through the center of the experimental restorations.The numbers define the microleakage scores: 0 = no dye penetration; 1 = dye penetration not deeper than halfthe length of the cavitywall between margin and bottom:and 2 = dye penetration deeper than score 1.
33
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, SUPPLEMENT 1992
Table 1.
Type
Type
gation was to restore human teeth in uiuo and to retain them for 3 months before extraction and prior to conventional laboratory processing for evaluation of microleakage. This procedure should eliminate several of the concerns associated with in uitro microleakage testing. Among others, variables such as the effects of dentinal fluid and intratubular pressure of the dentinal liquid on the development and the consistency of dentin bonding or the influences of temperature and load cycling of the restored teeth while in service are no longer a matter of dispute. Such effects will show up directly in the consecutively performed in uitro assessment of the restorations. However, this method of microleakage testing is not free from errors and shortcomings. For example, it is not clear whether possible gap formation between cavity and restoration starting from the cavity margin is detected by the dye-penetration method, since such gaps are n o t assumed to stay empty but rather will be closed by pellicle formation and by packing with plaques. Another concern is the difference in temperature between the teeth in uiuo and their storage and processing in uitro,which was around 15°C lower. This cooling effect might give rise to false microleakage registration. Possible effects on microleakage related to masticatory stresses will probably not be pronounced with the sample used in this investigation. The teeth assigned were severely periodontally compromised and showed a pronounced mobility. Thus, due to their reduced loading during mastication, deformation of the teeth, resulting in stresses at the bonding interface, is expected to be minimal. As well, the rather short time during which the restorations have been in service is another limitation of this trial. When the fillings were carefully inspected while still in the mouth, neither marginal staining nor marginal discontinuity were identifled,which would have pointed to microleakage.Therefore,tentatively, the leakage specified by dye penetration may also result from mechanical stresses induced either during extraction or during laboratory processing of the teeth. The present microleakage results seem to indicate that bonding to conditioned enamel with the new adhesive compound is effectiveand safe. Although clinically the conditioned enamel does not look as frosty as phosphoric acid etched enamel, which suggests a less pronounced etching pattern, the micromechanical retention of the adhesively bonded restorations seems to be adequate. Only in one of the 14 fillings was a moderately deep dye penetration found at an enamel margin and registered with a score of 1. Regarding the quality of the bond mediated at the cavity margins apically from the cementcrenameljunction, the results are less favorable. Nevertheless, five of the seven samples showed no dye penetration. Since dentinal adhesives and restorative resins have to be considered synergetically,it may be hypothesized that a combination of the new adhesive material with another compositeresin, preferably not a microfilled type, would
Microleakage by Dye Penetration Scores
’
*
incisal apical incisal apical
0
1
2
7 6 7 5
0 1 0 1
0 0 0 1
mately 22°C) until further processing after a minimum of 2 and a maximum of 7 days. For visualization of possible microleakage, the teeth were immersed in a tracer solution at room temperature for 24 hours (0.5% aqueous solution of basic fuchsin). After removal from the dye solution the specimens were washed, dried with compressed air, and embedded in slow-curing epoxy resin. Each tooth was then sectioned with a low-speed diamond saw (Leitz 1600,Mfinchen, Germany)through the center of the two restorations in a buccolingual direction. Thus, possible dye penetration along the cavity restoration interface of both fillings could be examined on each of the halves of the tooth. For microscopic inspection a dissecting microscope was used at twentyfold magnification (Zeiss, Miinchen, Germany). The extent of microleakage was registered as the depth of dye penetration according to the following scores: 0 = no penetration; 1 = penetration not deeper than half the length of the cavity wall between margin and bottom; 2 = penetration deeper than score 1. Each section was evaluated independently by three evaluators. In case of discrepancies between the scores given by the investigators, mutual agreement was obtained after repeated inspection and discussion.
RESULTS Table 1 summarizes the results of this microleakage study. Dye penetration was registered both for the incisal and the apical portions of the restoration types 1 and 2. None of the restorations leaked at the incisal portion. For the type 1fillings only one case of moderate dye penetration was found, whereas two of the type 2 restorations showed dye penetration originating from the cervical margin, which was located apically from the cementoenameljunction. Because of the small number of specimens and the preliminary character of this investigation, no attempt was made to analyze the data statistically.
DISCUSSlON The effect of microleakage on the survival of the dentinal bond in uiuo is hypothetical so far. Laboratory microleakage studies do not reliably reflect the clinical performance of adhesive systems, and clinical observations have the shortcoming that, in spite of possible microleakage due to partial debonding, the restoration might still be retained and assessed clinically acceptable. Therefore the basic concept of the present investi-
34
Esthetic Arch Bar in Orthognathic Surgery
have shown better clinical performance. This hypothesis is supported by the study of Hdrsted-Bindslevet a19who found that so-called miniwed composite resins performed significantlybetter with regard to marginal fractures and marginal discoloration than microfilled composite resins when the tillingswere placed in nonundercut cervical erosion lesions and retained with dentin and enamel bonding agents. The new adhesive material tested is a clinically promising agent that seems to mediate an adequate bond to enamel and even to dentin. To substantiate the validity of the in uiuo/in uitro method used, further research involvinga larger number of teeth and different adhesive restorative systems is in progress.
3. BrSnnstr6rn M. Composite resin restorations: biological considerations with special reference to dentin and pulp. In: Vanherle G, Smith DC, eds. Posterior composite resin dental restorative materials. Netherlands: Peter Szulc 1985, 7-8. 4. Torstenson B, NordenvalJ KJ, B r h s t r 6 m M. Pulpal reaction and microorganisms under C l e m composite resin in deep cavities with acid etched dentin. Swed Dent J 1982; 56-176. 5. Triadan H. When is microleakage a real clinical problem? Operat Dent 1987; 12:153-157. 6. Kubo S. Finger WJ, Mtiller M, Podszun W. Principles and mechanisms of bonding with dentin adhesive materials. J Esthet Dent 1991; 2:62-69. 7. S6derholmKJM. Correlationofinvivo andinvitro performance of adhesive restorative materials: a report of the ASC MD 156 Task Group on Test Methods for the Adhesion of Restorative Materials. Dent Mater 1991; 7:74-83. 8. Rueggeberg FA. Substrate for adhesion testing to tooth structure-review of the literature. Dent Mater 1991; 7: 2-10. 9. HBrsted-BindslevP, Knudsen J. Baelum V. Dentin adhesive materials for restoration of cervical erosions. Two and three year clinical observations. Am J Dent 1988: 1:195199.
REFERENCES 1. Torstenson B. Oden A. Effects of bonding agent types and incremental techniques on ' . . i g contraction gaps around resin composites. Dent Mater 1989; 5:21&223. 2. Finger WJ. Dentin bonding agents. Relevance of in vitro investigations. Am J Dent 1988; 1:184-188.
Esthetic Arch Bar for Maxillomandibular Fixation in Orthognathic Surgery Fun-Chee Loh, B.D.S., MB.S., MSc., F.A.M.S.," Kenneth K.K. Lew, B.D.S., M.D.S., FA.M.S.,t and Chee-Hwee Sim
Arch bars are well-known dental appliances for the management of fractures and orthognathic surgery. Traditionally both the commercially available, prefabricated arch bars as well as the custom-made arch bars are made of metal so as to provide good rigidity. Each of these types of arch bars has its own advantages as well as drawbacks. This article looks at a type of custom-made arch bar that is easy to construct and use. At the same time, it provides good rigidity, fit, and esthetics.
T
cause these metallic arch bars provide a precise fit onto the dentition, they are useful for localizing segments of the dental arches. Because the majorityof patients seeking orthognathic surgery for dentofacial deformities are adults who are well aware of esthetics, we have developed an arch bar that is made of self-curing clear acrylic resin that provides good rigidity, precise fit, and at the same time is esthetically acceptable.
for maintaMng the dental he use of arch arches in the management offractures and for maxfflomandibular fixationin orthognathic surgery is a wellestablished practice. Prefabricated arch bars are easily obtainable commercially and, unlike the custom-made arch bars, do not require any laboratory procedure. Custom-made arch bars suffer from the d u d disadvantages of requiring rather sophisticated laboratory support and of esthetic unacceptability. Nevertheless, be-
35
6. Chen RCS, Chan DCN, Chan KC. A quantitative study of finishing and polishing techniques for a composite. J Prosthet Dent 1988; 59:292-297. 7. Boghosian AA. Randolph RG. J e w s VJ. Rotary instrument finishing of microfilled and small-particle hybrid composite resins. J Am Dent Assoc 1987; 115:299-301. 8. Goldstein GR.Waknine S.Surface roughness evaluation of composite resin polishing techniques. Quintessence Int 1989; 20:199-204. 9. Zar JH. Biostatistical analysis. 2nd Ed. Englewood Cliffs, NJ:Prentice-Hall, 1984. 10. Xin YI Yu MM, Wieczkowski G, Davis EL, Joynt FU3. The influence of finishing technique on microleakage.J Esthet Dent 1990; 2: 142-144.
REFERENCES 1. Stoddard J W , Johnson GH. An evaluation of polishing agents for composite resins. J Prosthet Dent 1991; 65: 491-495. 2. Herrgott A-ML. Ziemiecki TL, Dennison JB. An evaluation of different composite resin systems finished with various abrasives. J Am Dent Assoc 1989; 119:72!3-732. 3. Northeast SE. van Noort R. Surface characteristics of finished composite resins. Dent Mater 1988; 4:278-288. AHL, Chan CA. The polishabilityof posterior compos4. T~an ites. J Prosthet Dent 1989: 61:138-146. 5. Eide R 'Met AB. Finishing and polishing of composites. Acta Odontol Scand 1988; 46:307-312.
Marginal Leakage of a New Adhesive Restorative System: A Preliminary In Vivo Investigation Marco Ferrari, D.D.S.," Werner J . Finger, D.D.S., Ph.D.1 and Andrea Gesi, D.D.S.
The efficacy of newly developed adhesive restorative materials is commonly described by in uitro test results such as bond strength and microleakage data. Due to the inconsistency often found between in uitro testing and in uiuoperfomance, the purpose of the present investigationwas to restore teeth scheduled for extraction in uivowith an experimentalrestorative bonding system and to evaluate the microleakage of the restorations by common laboratory techniques following extraction after 3 months of clinical service. Two restorations were placed in each of seven anterior teeth, one in the middle of the labial enamel portion and the other labially extending over the cementoenameljunction (CEJ). Six of the seven fillings completely surrounded by enamel showed no microleakage. However, two of the restorations crossing the C W revealed microleakage originating from the cervical margins. In spite of the small number of flllinEls assessed, the experimental enamel-dentin adhesive compound tested is preliminarily considered a promising new system.
T
he function of adhesive restorative materials is to achieve a firm and consistent adaptation between cavity wall and restoration. Insufacientbondingstrength may result in total or partial debonding of the filling. Such debonding is primarily caused by the polymeriza-
tion contraction of restorative resins, and by repetitive thermal and/or mechanical stresses acting on the bonding i n t e r f a ~ e . ~ Consecutively, .~ marginal opening and the presence of gaps may lead to bacterial or toxin invasion along the cavity wall. The possible consequences are formation of caries, adverse pulp reactions, and marginal staining of the r e s t o r a t i ~ n .Recently, ~.~ an experimentaldentoenamel bonding agentwas presented by Kubo et al.s This compound was reported to micromechanically bond composite restorative resins to conditioned enamel and dentin. According to the authors, a resin-impregnated mne in inter- and peritubular dentin is readily achieved due to the compounds outstanding wetting of and penetration into acid-conditioned dentin.
'Assistant Professor. Siena University.School of Dentistry. Departmentof ConservativeDentistry. Siena. Italy: t Professor. Universityofhchen. Dental School. Departmentof ProstheticDentism and Dental Materials and Department of Clinical Research and Dental Materials Sclence. Bayex Dental. Dormagen. Germany; *Instructor. Siena University. School of Dentistry, Siena. Italy Address reprint requests to Dr. Manx, Fermi. Piazza Attla 19, 57125 Livorno. Italy 0 1992 Decker PeriodicalsInc.
32
Marginal Leakage of New Adhesive Restorative System
possible microleakage gateways generated during the time of clinical service of the experimental adhesive restorations.
MATERIALS AND METHODS Seven volunteer patients with one severely periodontally compromised anterior tooth each (four upper incisors and three upper canines), which had not received previous restorative treatment and which was scheduled for extraction, agreed to join the trial. As shown in Figures 1 and 2, circular, V-shaped cavities with a n approximate diameter of 3 mm and a maximum depth of 2 mm were cut under copious waterspray with a diamond tip mounted in a turbine handpiece. A cavosurface angle of 120 to 140 degrees was prepared along the entire cavity margin. While the incisal cavity (type 1)was surrounded by enamel, the cervical cavity (type 2) was located at the cementoenameljunction with half of the cavity margin in enamel and half in root cementum. Following cavity preparation a rubber dam was applied, and the tooth was rinsed and dried prior to a 30-second conditioning treatment of the cavity and a small area of the peripheral unprepared tooth surface. The conditioning solution, Bayer D 666/2 (aqueous solution of oxalic acid, Al-nitrate and glycine;batch: SPK 409/ l),was applied with a soaked cotton pellet under a light dabbing action. According to the manufacturer the purpose of this pretreatment is ( 1)to remove the smear layer produced a s a result of the preparation and (2)to condition enamel and dentin for wetting with and penetration of the adhesive substance into the exposed surface for micromechanical retention of the restoration. The preparation was then carefully rinsed with water for 10 seconds and blown dry with a gentle stream of compressed air from the dental unit for another 5 to 10 seconds. This procedure was followed by application with a soaked pellet of the experimental adhesive, Bayer D 667/2 (aqueous solution of N-methacryloyloxy-ethylN-methyl-formamide,Bis-GMA,acetic acid and ethanol: batch: SPK 410/1), to the entire cavity wall for 30 seconds before the cavity was gently air dried. The microfilled light-curing composite resin Pekalux (Bayer Dental, Leverkusen, Germany, batch: 1154 G) was inserted by a syringe from preloaded tubes (PLT)in three increments. Each increment was separately light activated for 20 seconds. Prior to activation of the Anal increment a transparent matrix was placed for contouring and as an effective barrier for oxygen to prevent inhibition of polymerization at the free surface of the restorative resin. Immediately after curing, the restorations were finished with dry Sof-flex disks (3M. St. Paul, MN). and 80 to 110days later the teeth were extracted. Because of the mobility of the periodontally weakened teeth, extraction was possible without exerting severe bending stresses. The samples were washed with deionized water and immediately transferred in an aqueous 1% Chloramin solution for storage at ambient temperature (approxi-
Figure 1. V-shaped class V cavities are located in the labioenamel portion (type 1) and at the cementoenameljunction (type 2) of anterior teeth of the upperjaw. The circular cavities have a n approximate diameter of 3 mm.
After polymexizationthis hybrid layer acts as an effective coupling site between the cavity wall and the restorative resin. The limitation of the article mentioned is that the data presented are at best suited for a hypothetical prediction of clinical ~ e r f o m a n c e This . ~ holds true generally for in uitro investigations of the efficacy of adhesive restorative materials, in particular when nonhuman teeth are used for testing.8 Therefore the objective of the present trial was to outline and to try a testing procedure involving teeth scheduled for extraction from volunteer patients. This method makes it possible with conventional tracer solution methods to investigate, on extracted, restored teeth,
Figure 2. Buccoling~dsectionthrough the crown of the tooth and through the center of the experimental restorations.The numbers define the microleakage scores: 0 = no dye penetration; 1 = dye penetration not deeper than halfthe length of the cavitywall between margin and bottom:and 2 = dye penetration deeper than score 1.
33
JOURNAL OF ESTHETIC DENTISTRY VOLUME 4, SUPPLEMENT 1992
Table 1.
Type
Type
gation was to restore human teeth in uiuo and to retain them for 3 months before extraction and prior to conventional laboratory processing for evaluation of microleakage. This procedure should eliminate several of the concerns associated with in uitro microleakage testing. Among others, variables such as the effects of dentinal fluid and intratubular pressure of the dentinal liquid on the development and the consistency of dentin bonding or the influences of temperature and load cycling of the restored teeth while in service are no longer a matter of dispute. Such effects will show up directly in the consecutively performed in uitro assessment of the restorations. However, this method of microleakage testing is not free from errors and shortcomings. For example, it is not clear whether possible gap formation between cavity and restoration starting from the cavity margin is detected by the dye-penetration method, since such gaps are n o t assumed to stay empty but rather will be closed by pellicle formation and by packing with plaques. Another concern is the difference in temperature between the teeth in uiuo and their storage and processing in uitro,which was around 15°C lower. This cooling effect might give rise to false microleakage registration. Possible effects on microleakage related to masticatory stresses will probably not be pronounced with the sample used in this investigation. The teeth assigned were severely periodontally compromised and showed a pronounced mobility. Thus, due to their reduced loading during mastication, deformation of the teeth, resulting in stresses at the bonding interface, is expected to be minimal. As well, the rather short time during which the restorations have been in service is another limitation of this trial. When the fillings were carefully inspected while still in the mouth, neither marginal staining nor marginal discontinuity were identifled,which would have pointed to microleakage.Therefore,tentatively, the leakage specified by dye penetration may also result from mechanical stresses induced either during extraction or during laboratory processing of the teeth. The present microleakage results seem to indicate that bonding to conditioned enamel with the new adhesive compound is effectiveand safe. Although clinically the conditioned enamel does not look as frosty as phosphoric acid etched enamel, which suggests a less pronounced etching pattern, the micromechanical retention of the adhesively bonded restorations seems to be adequate. Only in one of the 14 fillings was a moderately deep dye penetration found at an enamel margin and registered with a score of 1. Regarding the quality of the bond mediated at the cavity margins apically from the cementcrenameljunction, the results are less favorable. Nevertheless, five of the seven samples showed no dye penetration. Since dentinal adhesives and restorative resins have to be considered synergetically,it may be hypothesized that a combination of the new adhesive material with another compositeresin, preferably not a microfilled type, would
Microleakage by Dye Penetration Scores
’
*
incisal apical incisal apical
0
1
2
7 6 7 5
0 1 0 1
0 0 0 1
mately 22°C) until further processing after a minimum of 2 and a maximum of 7 days. For visualization of possible microleakage, the teeth were immersed in a tracer solution at room temperature for 24 hours (0.5% aqueous solution of basic fuchsin). After removal from the dye solution the specimens were washed, dried with compressed air, and embedded in slow-curing epoxy resin. Each tooth was then sectioned with a low-speed diamond saw (Leitz 1600,Mfinchen, Germany)through the center of the two restorations in a buccolingual direction. Thus, possible dye penetration along the cavity restoration interface of both fillings could be examined on each of the halves of the tooth. For microscopic inspection a dissecting microscope was used at twentyfold magnification (Zeiss, Miinchen, Germany). The extent of microleakage was registered as the depth of dye penetration according to the following scores: 0 = no penetration; 1 = penetration not deeper than half the length of the cavity wall between margin and bottom; 2 = penetration deeper than score 1. Each section was evaluated independently by three evaluators. In case of discrepancies between the scores given by the investigators, mutual agreement was obtained after repeated inspection and discussion.
RESULTS Table 1 summarizes the results of this microleakage study. Dye penetration was registered both for the incisal and the apical portions of the restoration types 1 and 2. None of the restorations leaked at the incisal portion. For the type 1fillings only one case of moderate dye penetration was found, whereas two of the type 2 restorations showed dye penetration originating from the cervical margin, which was located apically from the cementoenameljunction. Because of the small number of specimens and the preliminary character of this investigation, no attempt was made to analyze the data statistically.
DISCUSSlON The effect of microleakage on the survival of the dentinal bond in uiuo is hypothetical so far. Laboratory microleakage studies do not reliably reflect the clinical performance of adhesive systems, and clinical observations have the shortcoming that, in spite of possible microleakage due to partial debonding, the restoration might still be retained and assessed clinically acceptable. Therefore the basic concept of the present investi-
34
Esthetic Arch Bar in Orthognathic Surgery
have shown better clinical performance. This hypothesis is supported by the study of Hdrsted-Bindslevet a19who found that so-called miniwed composite resins performed significantlybetter with regard to marginal fractures and marginal discoloration than microfilled composite resins when the tillingswere placed in nonundercut cervical erosion lesions and retained with dentin and enamel bonding agents. The new adhesive material tested is a clinically promising agent that seems to mediate an adequate bond to enamel and even to dentin. To substantiate the validity of the in uiuo/in uitro method used, further research involvinga larger number of teeth and different adhesive restorative systems is in progress.
3. BrSnnstr6rn M. Composite resin restorations: biological considerations with special reference to dentin and pulp. In: Vanherle G, Smith DC, eds. Posterior composite resin dental restorative materials. Netherlands: Peter Szulc 1985, 7-8. 4. Torstenson B, NordenvalJ KJ, B r h s t r 6 m M. Pulpal reaction and microorganisms under C l e m composite resin in deep cavities with acid etched dentin. Swed Dent J 1982; 56-176. 5. Triadan H. When is microleakage a real clinical problem? Operat Dent 1987; 12:153-157. 6. Kubo S. Finger WJ, Mtiller M, Podszun W. Principles and mechanisms of bonding with dentin adhesive materials. J Esthet Dent 1991; 2:62-69. 7. S6derholmKJM. Correlationofinvivo andinvitro performance of adhesive restorative materials: a report of the ASC MD 156 Task Group on Test Methods for the Adhesion of Restorative Materials. Dent Mater 1991; 7:74-83. 8. Rueggeberg FA. Substrate for adhesion testing to tooth structure-review of the literature. Dent Mater 1991; 7: 2-10. 9. HBrsted-BindslevP, Knudsen J. Baelum V. Dentin adhesive materials for restoration of cervical erosions. Two and three year clinical observations. Am J Dent 1988: 1:195199.
REFERENCES 1. Torstenson B. Oden A. Effects of bonding agent types and incremental techniques on ' . . i g contraction gaps around resin composites. Dent Mater 1989; 5:21&223. 2. Finger WJ. Dentin bonding agents. Relevance of in vitro investigations. Am J Dent 1988; 1:184-188.
Esthetic Arch Bar for Maxillomandibular Fixation in Orthognathic Surgery Fun-Chee Loh, B.D.S., MB.S., MSc., F.A.M.S.," Kenneth K.K. Lew, B.D.S., M.D.S., FA.M.S.,t and Chee-Hwee Sim
Arch bars are well-known dental appliances for the management of fractures and orthognathic surgery. Traditionally both the commercially available, prefabricated arch bars as well as the custom-made arch bars are made of metal so as to provide good rigidity. Each of these types of arch bars has its own advantages as well as drawbacks. This article looks at a type of custom-made arch bar that is easy to construct and use. At the same time, it provides good rigidity, fit, and esthetics.
T
cause these metallic arch bars provide a precise fit onto the dentition, they are useful for localizing segments of the dental arches. Because the majorityof patients seeking orthognathic surgery for dentofacial deformities are adults who are well aware of esthetics, we have developed an arch bar that is made of self-curing clear acrylic resin that provides good rigidity, precise fit, and at the same time is esthetically acceptable.
for maintaMng the dental he use of arch arches in the management offractures and for maxfflomandibular fixationin orthognathic surgery is a wellestablished practice. Prefabricated arch bars are easily obtainable commercially and, unlike the custom-made arch bars, do not require any laboratory procedure. Custom-made arch bars suffer from the d u d disadvantages of requiring rather sophisticated laboratory support and of esthetic unacceptability. Nevertheless, be-
35
