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A 12-month clinical evaluation of a glass polyalkenoate cement for the direct bonding of orthodontic brackets
CLINICIANS' CORNER
A 12-month clinical evaluation of a glass
polyaUcenoate cement for the direct bonding of orthodontic brackets John P. Fricker, BDS, MDSc, FRACDS* Canberra, Australia
Glass polyalkenoate (ionomer) cements have the unique properties to physicochemically bond to enamel and base metals, and to leach fluoride over prolonged periods. These cements are hybrids of silicate and polycarboxylate cements and, like the silicate cements, retain a cariostatic action on adjacent enamel. This article reports on a 12-month clinical trial of a glass ionomer cement for the direct bonding of orthodontic brackets compared with a standard composite bonding adhesive. This study shows a significant difference in failure rates of direct-bonded orthodontic brackets cemented With a thick mix of Fuji I glass polyalkenoate cement (20%) compared with System I+ composite bonding resin (5%). (AM J ORTHOODENTOFACORTHOP 1992;101:381-4.)
T h e development of the acid etch technique o f dental enamel t dramatically changed the practice o f orthodontics by allowing the direct bonding of orthodontic brackets. Bonded brackets improve esthetics, reduce chairside time at band-up, and allow for reduction o f interproximal tooth enamel during active treatment. However, the bracket base acts as a plaque trap and, in the absence o f good oral hygiene, enamel demineralization can occur around bracket margins. 2 Glass polyalkenoate (ionomer) cements were invented by Wilson and Kent 3 as hybrids o f silicate and polycarboxylate cements and, as such, have properties of both. These cements leach fluoride over prolonged periods and physiochemically bond to base metals and dental enamel. 4.g The shear bond strength of a glass polyalkenoate cement to enamel is greater than to stainless steel. The incorporation of additional powder into the mix increases the bond strength to enamel. 9''~ This article reports on a 12-month clinical evaluation o f a glass polyalkenoate cement for the direct bonding of orthodontic brackets mixed with twice the powder/liquid ratio as recommended by the manufacturer.
MATERIALS AND METHODS Sample. From one practice, 10 subjects with full-fixed appliances and a range of malocclusions covering Angle Class
*Specialist Orthodontist in priva',e practice. Canberra, Australia; Visiting Specialist Orthodontist, Department or Pediatric Dentistry, Westmead Centxe Dental Clinical School, Sydney, Australia. 811129949
I, Class 1I, and Class 11I with crowding were selected. Four subjects had no teeth extracted, four had upper first premolars extracted, and two had four first premolars extracted. A prerequisite for the selection of subjects for this trial was that there was to be no occlusal interference on any of the bonded brackets (Ultratrim high flange lightwire brackets, Dentaurum, Germany). The anterior segments were divided into quadrants, so that in five subjects the maxillary left and mandibular right quadrants were bonded with glass polyalkenoate cement, and the other quadrants were bonded with the control composite resin. The other five subjects had glass polyalkenoate cement on the maxillary right and mandibhlar left quadrants, with the control composite on the remaining anterior teeth. Thus there were 60 brackets bonded with glass polyalkenoate cement and 60 brackets bonded with composite resin. Adhesives. The trial adhesive, Fuji I luting cement (G-C Industrial Co., Tokyo, Japan), used twice the powder/liquid ratio as recommended by the manufacturer, and the control composite, System I + (Ormco Corp., Glendora, Calif.), was mixed according to the manufacturer's instructions. Method. Molar bands were cemented on the first permanent molars, and the cement allowed to set. The anterior teeth were then polished with a pumice slurry and washed. These teeth were then isolated with a cheek retractor and tongue shield. The two quadrants selected for the control composite were bonded first, according to the manufacturer's recommendations. The remaining anterior teeth were conditioned over the labial surface with Fuji I liquid (polyacrylic acid) for 10 seconds, rinsed with a triplex syringe, and lightly dried with compressed air. The polyalkcnoate cement was dispensed onto a chilled glass slab with twice the amount of powder per drop of liquid than recommended by the manufacturer. This was mixed for 1 minute incorporating all the powder, placed on the bracket
381
382
Fricker
Am. J.
Orthod. Dentofac. Orthop. April 1992
T a b l e I. Bracket failures for each adhesion
Furl i glass polyalkenoate (thick mix) Patient no.
I
Tooth
Time offailure (too.)
System 1 + composite resin Cause of failure
0-3 7-9 4-6 10-12
Unknown Direct trauma Direct trauma Unknown
0-3 4-6 4-6
Unknown Unknown Removing ligature tie Removing arch wire Removing arch wire Unknown Unknown
1
lI
2 3 4 5 6 7
31 It 31 Nil 42,43 41 21
8
21
4-6
9
22 41 23
0-3 4-6 10-12
l0 Total breakages
Nil 12 20%
Tooth
j
Timeoffidlure (too.)
Cause of failure
43
7-9
Unknown
21,22
0-3
Direct trauma
3 5%
df = 1 X = 6.171. Significance, p > 0.010. base, and positioned on the labial tooth enamel with finn pressure. Two brackets were positioned with each mix, and once the cement had reached gel stage, the excess cement was scaled from the margins, and the bracket covered with a generous layer of petroleum jelly. Initial arch wires were then shaped for each case. Of the 20 arch wires placed, 12 were 0.016-inch premium round stainless steel (AJ Wilcock, Australia), 4 were 0.014-inch premium round stainless steel (AJ Wilcock, Australia), and 4 were 0.016-inch nickel titanium round (Nitinol, Unitek, Monrovia, Calif.). These were pinned and ligated approximately 15 minutes after the last bracket was bonded. Bracket failures were then monitored over the 'first 12 months of active treatment. These are an "all or none" phenomenon. The bracket was either fixed to the enamel surface or detached and slid easily along the arch wire. A X2 analysis was carried out on the recorded numbers of failures for each adhesive.
RESULTS The bracket failures were recorded for each adhesive on a 3-month basis (Table I). After 12 months of active treatment, there were 12 failures with glass polyalkenoate cement and 3 with composite resin (df = l X = 6.171. Significance; p > 0.01), indicating that the probability of these results occurring by chance is minimal. Of the 12 failures with glass polyalkenoate cement, two were from direct trauma and three were by the operator adjusting the appliances. Of the three failures
with composite resin, two were from direct trauma. The majority o f all failures occurred within the first 6 months, 8 of the 12 were glass polyalkenoate cement and 2 Of the 3 were composite resin. Of the 10 subjects in this trial, two had no breakages with either glass polyalkenoate adhesive or composite resin adhesive.
DISCUSSION The primary requirement of any bonding adhesive is that it secures the bracket for the duration of active orthodontic treatment. In the absence o f fluoride, demineralization of enamel around orthodontic appliances can occur within 4 weeks.t' Glass polyalkenoate cements release fluoride over prolonged periods,58 and clinical trials have shown their preventive capabilities when cementing molar bands, t2'5 No demineralization occurred around bands cemented with the glass polyalkenoate cement compared with the zinc phosphate cement, t6 In vitro testing o f bond strength of the glass polyalkenoate cements has shown these to be approximately 32 k g / c m 2 when mixed at the manufacturer's specifications. 9"t7 System I + has a bond strength o f 103 kg/cm2. '7 Similar strength values have been reported for other composite bonding resins, Ketac cement and Relyabond, respectively. '~2~ Glass polyalkenoate cements adhere to enamel and base metals by physiochemical bonding, and etching is not indicated. However, Powis et al. 2' found that pre-
Volume 101
Clinicians' corner
Number 4
treatment of the enamel surface with polyacrylic acid improved the adhesion of the cement to enamel. Cook and Youngson ts found no significance in this pretreatment using Ketac Cem (ESPE-Premier, Norristown, Pa.) as an adhesive. This may be because of the different cements used. Ketac Cem is a second generation cement with a water-based liquid and a freeze-dried powder. Fuji I cement liquid contains the polyacrylic acid, and hence, it was decided to follow the recommendations of Powis et al. 2t and condition the enamel for 10 seconds before bonding. More recently, Fajen et al. 22 have shown that pretreatment of enamel may not be necessary. The incorporation of additional powder into the mix of glass polyalkenoate cement reduces the working and setting times.~~ This may be controlled by mixing the cement on a chilled glass slab to increase the working I time at r.oom temperature with a rapid set at mouth temperatu're) 4'v'24 Thicker mixes of cement also improve t h e shear bond strength to enamel. ~~ Thus one would suggest that the shear bond strength to the bracket would also be significantly higher than previously recorded. The major forces that the appliances must withstand during orthodontic treatment are occlusal. 2s The selection for this clinical trial aimed at the removal of occlusal interferences, with no deep overbite or anterior cross-bite cases in the sample. Comparisons may then be drawn between the retention of the brackets with a standard bonding agent (System I + ) and the trial glass polyalkenoate cement (Fuji I). Glass polyalkenoate cements have a progressive two-stage setting reaction and are sensitive to moisture even after the apparent set. :6 Hardening and strengthening continues for up to 24 hours after the set. Exposure to moisture reduces the strength of the cement and increases its solubility. It is recommended that the brackets be covered with a generous layer of petroleum jelly once they are positioned to protect them from moisture for at least 20 minutes, z7 This trial would indicate that glass polyalkenoate cements do provide satisfactory strength under clinical conditions when a thicker mix is used. Though there were significantly more breakages with Fuji I cement compared with System I + , two patients had no breakages at all. This supports a clinical trial by-Cook -'s who showed a 12.4% failure rate when Ketac Cem was used. However, it is questionable whether the 20% failure rate for Fuji I cement is clinically acceptable. The banding procedure may need to be modified for glass polyalkenoate cements because of its relatively slow build up of strength and hardness. In this trial only a m i n i m u m of 15 minutes was allowed before placement of the arch wires. It may be more appropriate to
383
allow at least 24 hours after bonding the brackets before the arch wires are placed to take advantage of the increased bond strength of the material. Further trials are indicated to test these cements over the full time of active treatment and to assess techniques of debonding.
CONCLUSION Fuji I glass polyalkenoate cement, when used as a thick mix, has a poorer clinical performance than System I + bonding resin for the direct bonding of orthodontic brackets. The leach of fluoride by glass polyalkeonate cement prevents enamel demineralization around bracket margins and is a definite advantage. These cements may be indicated as bracket adhesives in those patients who have poor oral hygiene a n d / o r a high caries rate.
REFERENCES
1. BuonocoreMG. A simple method of increasingthe adhesionof acrylic filling materials to enamel surface. J Dent Res 1955;34:849-53. 2. Gorelick L, Geiger AM; Gwinnett AJ. Incidenceof white spot formation after bonding and banding. AM J OR'nIOD1982;81: 93-8. 3. Wilson AD, Kent BE. The glass-ionomercement: a new translucent filling material. J Appl Chem Biotechnol 1971;21:313. 4. Wilson AD, Prosser HJ. Biocompatibilityof the glass ionomer cement. JDASA 1982;37:872-9. 5. Tay WM, Braden M. Fluoride diffusion from polyalkenoate (glass ionomer)cements. Biomaterials 1988;9:454-6. 6. Meryon SD, Smith AJ. A comparison of fluoride release from three glass ionomercements and a polycarboxylatecement. Int Endo J 1984;17:16-24. 7. Retief DH, Bradley EL, Denton JC, Switzer P. Enamel and cementum fluoride uptake from a glass ionomercement. Caries Res 1984;18:250-7. 8. Swartz ML, PhillipsRW, Clarke HE. Long term F release from glass ionomercements. J Dent Res 1984;63:158-60. 9. Fricker JP, Kameda A. The bond strength of a glass polyalkenoate cement to enamel and stainlesssteel. Aust Orthod J 1990; i 1:153-3. 10. Fricker JP. A clinical comparison of different powder: liquid ratios of two glass ionomer cements on the retentionof orthodontic molar bands. Aust Orthod J 1989;11:89-92. I 1. OgaardB, RollaG, ArendsJ. Orthodonticappliancesand enamel demineralizations. Part 1. Lesion development. AM J ORTItOD DEN'rOFAeORTttOP1988;94:68-73. 12. Fricker JP, McLachlan MD. Clinical studies of glass ionomer cements. Part I. A 12-month study comparing zinc phosphate to glass ionomer. Aust Orthod J 1985;9:179-80. 13. MaijerR, Smith DC. A comparisonbetweenzinc phosphate and glass ionomercement in orthodontics. AMJ ORTItOD DF.NTOFAC ORnxoP 1988;93:273-9. 14. SeeholzerttW, Dasch W. Bandingwith a glass ionomercement. J Clin Orthod 1988;22:165-9. 15. MizrahiE. Glass ionomer.cementsin orthodontics--an update. AM J O~:'mODDE.'~"roFArOwrHoP 1988;93:505-7. 16. Fricker JP, McLachlan MD. Clinical studies on glass ionomer cements. Part 2. A 2-yearclinicalstudycomparingglass ionomer
384
Fricker
Am. J. Orthod. Dentofac. Orthop. April 1992
cement with zinc phosphate cement. Aust Orthod J 1987;10: 12-4. 17. Fryar BC. An evaluation of the bond strength and failure site of composite resin and glass ionomer in identical direct bonding systems [MScD Thesis]. Indiana University, 1989. 18. Cook PA, Youngson CC. An in vitro study of the bond strength of a glass ionomer cement in the direct bonding of orthodontic brackets. Br J Orthod 1988;15:247-53. 19. Klockowski R, Davis EL, Joynt RB, Wieczkowski G, MacDonald A. Bond strength and durability of glass ionomer cements used as bonding agents in the placement of orthodontic brackets. AM J ORT}tOD DENTOFACOR'I'IIOP 1989;96:60-4. 20. Miller JR. Clinical evaluation o f glass ionomer cement as an adhesive for the bonding of orthodontic brackets [Thesis]. Indiana University, 1988. 21. Powis DR, Folleras T, Merson SA, Wilson AD. Improved adhesion of a glass ionomer cement to dentine and enamel. J Dent Res 1982;62:223-8. 22. Fajen VB, Duncanson MG, Nanda RS, Currier GF, Angolkar PV. An in vitro evaluation of bond strength of three glass ionomer cements. AM J ORTHOD DEN'rOFACORIItOP 1990;97:316-22.
23. Mollenhauer B. New approaches to the Begg technique. Part 1: qualitative aspects. Aust Orthod J 1987;10:67-89. 24. Fricker JP, Hirota K, Tamiya Y. The effects of temperature on the setting of a glass ionomer cement. Aust Dent J 1991;36: 240-2. 25. Reynolds IR. A review of direct orthodontic bonding. Br J Orthod 1975;2:171-8. 26. Walls AWG, McCabe JF, Murray JJ. Factors influencing the setting reaction of glass polyalkenoate (ionomer) cements. J Dent 1988;16:32-5. 27. Earl MSA, ltume WR, Mount GJ. Effects of varnishes and other surface treatments on water movement across the glass-ionomer cement surface. Aust Dent J 1985;30:298-301. 28. Cook PA. Direct bonding with glass ionomer cement. J Clin Orthod 1990;24:509-I 1. Reprint requests to: Dr. J. P. Fricker P.O. Box 3544 Manuka, A.C.T. 2603 Australia
AAO MEETING CALENDAR 1992--St. Louis~ Mo., May 9 to 13, St. Louis Convention Center 1993--Toronto, Canada, May 15 to 19, Metropolitan Toronto Convention Center 1994--Orlando, Fla., May 1 to 4, Orange County Convention and Civic Center 1995--San Francisco, Calif., May 7 to 10, Moscone Convention Center
(International Orthodontic Congress) 1996--Denver, Colo., May 12 to 16, Colorado Convention Center 1997--Philadelphia, Pa., May 3 to 7, Philadelphia Convention Center 1998--Dallas, Texas, May 16 to 20;Dallas Convention Center 1999--San Diego, Calif., May 15 to 19, San Diego Convention'Center
A 12-month clinical evaluation of a glass
polyaUcenoate cement for the direct bonding of orthodontic brackets John P. Fricker, BDS, MDSc, FRACDS* Canberra, Australia
Glass polyalkenoate (ionomer) cements have the unique properties to physicochemically bond to enamel and base metals, and to leach fluoride over prolonged periods. These cements are hybrids of silicate and polycarboxylate cements and, like the silicate cements, retain a cariostatic action on adjacent enamel. This article reports on a 12-month clinical trial of a glass ionomer cement for the direct bonding of orthodontic brackets compared with a standard composite bonding adhesive. This study shows a significant difference in failure rates of direct-bonded orthodontic brackets cemented With a thick mix of Fuji I glass polyalkenoate cement (20%) compared with System I+ composite bonding resin (5%). (AM J ORTHOODENTOFACORTHOP 1992;101:381-4.)
T h e development of the acid etch technique o f dental enamel t dramatically changed the practice o f orthodontics by allowing the direct bonding of orthodontic brackets. Bonded brackets improve esthetics, reduce chairside time at band-up, and allow for reduction o f interproximal tooth enamel during active treatment. However, the bracket base acts as a plaque trap and, in the absence o f good oral hygiene, enamel demineralization can occur around bracket margins. 2 Glass polyalkenoate (ionomer) cements were invented by Wilson and Kent 3 as hybrids o f silicate and polycarboxylate cements and, as such, have properties of both. These cements leach fluoride over prolonged periods and physiochemically bond to base metals and dental enamel. 4.g The shear bond strength of a glass polyalkenoate cement to enamel is greater than to stainless steel. The incorporation of additional powder into the mix increases the bond strength to enamel. 9''~ This article reports on a 12-month clinical evaluation o f a glass polyalkenoate cement for the direct bonding of orthodontic brackets mixed with twice the powder/liquid ratio as recommended by the manufacturer.
MATERIALS AND METHODS Sample. From one practice, 10 subjects with full-fixed appliances and a range of malocclusions covering Angle Class
*Specialist Orthodontist in priva',e practice. Canberra, Australia; Visiting Specialist Orthodontist, Department or Pediatric Dentistry, Westmead Centxe Dental Clinical School, Sydney, Australia. 811129949
I, Class 1I, and Class 11I with crowding were selected. Four subjects had no teeth extracted, four had upper first premolars extracted, and two had four first premolars extracted. A prerequisite for the selection of subjects for this trial was that there was to be no occlusal interference on any of the bonded brackets (Ultratrim high flange lightwire brackets, Dentaurum, Germany). The anterior segments were divided into quadrants, so that in five subjects the maxillary left and mandibular right quadrants were bonded with glass polyalkenoate cement, and the other quadrants were bonded with the control composite resin. The other five subjects had glass polyalkenoate cement on the maxillary right and mandibhlar left quadrants, with the control composite on the remaining anterior teeth. Thus there were 60 brackets bonded with glass polyalkenoate cement and 60 brackets bonded with composite resin. Adhesives. The trial adhesive, Fuji I luting cement (G-C Industrial Co., Tokyo, Japan), used twice the powder/liquid ratio as recommended by the manufacturer, and the control composite, System I + (Ormco Corp., Glendora, Calif.), was mixed according to the manufacturer's instructions. Method. Molar bands were cemented on the first permanent molars, and the cement allowed to set. The anterior teeth were then polished with a pumice slurry and washed. These teeth were then isolated with a cheek retractor and tongue shield. The two quadrants selected for the control composite were bonded first, according to the manufacturer's recommendations. The remaining anterior teeth were conditioned over the labial surface with Fuji I liquid (polyacrylic acid) for 10 seconds, rinsed with a triplex syringe, and lightly dried with compressed air. The polyalkcnoate cement was dispensed onto a chilled glass slab with twice the amount of powder per drop of liquid than recommended by the manufacturer. This was mixed for 1 minute incorporating all the powder, placed on the bracket
381
382
Fricker
Am. J.
Orthod. Dentofac. Orthop. April 1992
T a b l e I. Bracket failures for each adhesion
Furl i glass polyalkenoate (thick mix) Patient no.
I
Tooth
Time offailure (too.)
System 1 + composite resin Cause of failure
0-3 7-9 4-6 10-12
Unknown Direct trauma Direct trauma Unknown
0-3 4-6 4-6
Unknown Unknown Removing ligature tie Removing arch wire Removing arch wire Unknown Unknown
1
lI
2 3 4 5 6 7
31 It 31 Nil 42,43 41 21
8
21
4-6
9
22 41 23
0-3 4-6 10-12
l0 Total breakages
Nil 12 20%
Tooth
j
Timeoffidlure (too.)
Cause of failure
43
7-9
Unknown
21,22
0-3
Direct trauma
3 5%
df = 1 X = 6.171. Significance, p > 0.010. base, and positioned on the labial tooth enamel with finn pressure. Two brackets were positioned with each mix, and once the cement had reached gel stage, the excess cement was scaled from the margins, and the bracket covered with a generous layer of petroleum jelly. Initial arch wires were then shaped for each case. Of the 20 arch wires placed, 12 were 0.016-inch premium round stainless steel (AJ Wilcock, Australia), 4 were 0.014-inch premium round stainless steel (AJ Wilcock, Australia), and 4 were 0.016-inch nickel titanium round (Nitinol, Unitek, Monrovia, Calif.). These were pinned and ligated approximately 15 minutes after the last bracket was bonded. Bracket failures were then monitored over the 'first 12 months of active treatment. These are an "all or none" phenomenon. The bracket was either fixed to the enamel surface or detached and slid easily along the arch wire. A X2 analysis was carried out on the recorded numbers of failures for each adhesive.
RESULTS The bracket failures were recorded for each adhesive on a 3-month basis (Table I). After 12 months of active treatment, there were 12 failures with glass polyalkenoate cement and 3 with composite resin (df = l X = 6.171. Significance; p > 0.01), indicating that the probability of these results occurring by chance is minimal. Of the 12 failures with glass polyalkenoate cement, two were from direct trauma and three were by the operator adjusting the appliances. Of the three failures
with composite resin, two were from direct trauma. The majority o f all failures occurred within the first 6 months, 8 of the 12 were glass polyalkenoate cement and 2 Of the 3 were composite resin. Of the 10 subjects in this trial, two had no breakages with either glass polyalkenoate adhesive or composite resin adhesive.
DISCUSSION The primary requirement of any bonding adhesive is that it secures the bracket for the duration of active orthodontic treatment. In the absence o f fluoride, demineralization of enamel around orthodontic appliances can occur within 4 weeks.t' Glass polyalkenoate cements release fluoride over prolonged periods,58 and clinical trials have shown their preventive capabilities when cementing molar bands, t2'5 No demineralization occurred around bands cemented with the glass polyalkenoate cement compared with the zinc phosphate cement, t6 In vitro testing o f bond strength of the glass polyalkenoate cements has shown these to be approximately 32 k g / c m 2 when mixed at the manufacturer's specifications. 9"t7 System I + has a bond strength o f 103 kg/cm2. '7 Similar strength values have been reported for other composite bonding resins, Ketac cement and Relyabond, respectively. '~2~ Glass polyalkenoate cements adhere to enamel and base metals by physiochemical bonding, and etching is not indicated. However, Powis et al. 2' found that pre-
Volume 101
Clinicians' corner
Number 4
treatment of the enamel surface with polyacrylic acid improved the adhesion of the cement to enamel. Cook and Youngson ts found no significance in this pretreatment using Ketac Cem (ESPE-Premier, Norristown, Pa.) as an adhesive. This may be because of the different cements used. Ketac Cem is a second generation cement with a water-based liquid and a freeze-dried powder. Fuji I cement liquid contains the polyacrylic acid, and hence, it was decided to follow the recommendations of Powis et al. 2t and condition the enamel for 10 seconds before bonding. More recently, Fajen et al. 22 have shown that pretreatment of enamel may not be necessary. The incorporation of additional powder into the mix of glass polyalkenoate cement reduces the working and setting times.~~ This may be controlled by mixing the cement on a chilled glass slab to increase the working I time at r.oom temperature with a rapid set at mouth temperatu're) 4'v'24 Thicker mixes of cement also improve t h e shear bond strength to enamel. ~~ Thus one would suggest that the shear bond strength to the bracket would also be significantly higher than previously recorded. The major forces that the appliances must withstand during orthodontic treatment are occlusal. 2s The selection for this clinical trial aimed at the removal of occlusal interferences, with no deep overbite or anterior cross-bite cases in the sample. Comparisons may then be drawn between the retention of the brackets with a standard bonding agent (System I + ) and the trial glass polyalkenoate cement (Fuji I). Glass polyalkenoate cements have a progressive two-stage setting reaction and are sensitive to moisture even after the apparent set. :6 Hardening and strengthening continues for up to 24 hours after the set. Exposure to moisture reduces the strength of the cement and increases its solubility. It is recommended that the brackets be covered with a generous layer of petroleum jelly once they are positioned to protect them from moisture for at least 20 minutes, z7 This trial would indicate that glass polyalkenoate cements do provide satisfactory strength under clinical conditions when a thicker mix is used. Though there were significantly more breakages with Fuji I cement compared with System I + , two patients had no breakages at all. This supports a clinical trial by-Cook -'s who showed a 12.4% failure rate when Ketac Cem was used. However, it is questionable whether the 20% failure rate for Fuji I cement is clinically acceptable. The banding procedure may need to be modified for glass polyalkenoate cements because of its relatively slow build up of strength and hardness. In this trial only a m i n i m u m of 15 minutes was allowed before placement of the arch wires. It may be more appropriate to
383
allow at least 24 hours after bonding the brackets before the arch wires are placed to take advantage of the increased bond strength of the material. Further trials are indicated to test these cements over the full time of active treatment and to assess techniques of debonding.
CONCLUSION Fuji I glass polyalkenoate cement, when used as a thick mix, has a poorer clinical performance than System I + bonding resin for the direct bonding of orthodontic brackets. The leach of fluoride by glass polyalkeonate cement prevents enamel demineralization around bracket margins and is a definite advantage. These cements may be indicated as bracket adhesives in those patients who have poor oral hygiene a n d / o r a high caries rate.
REFERENCES
1. BuonocoreMG. A simple method of increasingthe adhesionof acrylic filling materials to enamel surface. J Dent Res 1955;34:849-53. 2. Gorelick L, Geiger AM; Gwinnett AJ. Incidenceof white spot formation after bonding and banding. AM J OR'nIOD1982;81: 93-8. 3. Wilson AD, Kent BE. The glass-ionomercement: a new translucent filling material. J Appl Chem Biotechnol 1971;21:313. 4. Wilson AD, Prosser HJ. Biocompatibilityof the glass ionomer cement. JDASA 1982;37:872-9. 5. Tay WM, Braden M. Fluoride diffusion from polyalkenoate (glass ionomer)cements. Biomaterials 1988;9:454-6. 6. Meryon SD, Smith AJ. A comparison of fluoride release from three glass ionomercements and a polycarboxylatecement. Int Endo J 1984;17:16-24. 7. Retief DH, Bradley EL, Denton JC, Switzer P. Enamel and cementum fluoride uptake from a glass ionomercement. Caries Res 1984;18:250-7. 8. Swartz ML, PhillipsRW, Clarke HE. Long term F release from glass ionomercements. J Dent Res 1984;63:158-60. 9. Fricker JP, Kameda A. The bond strength of a glass polyalkenoate cement to enamel and stainlesssteel. Aust Orthod J 1990; i 1:153-3. 10. Fricker JP. A clinical comparison of different powder: liquid ratios of two glass ionomer cements on the retentionof orthodontic molar bands. Aust Orthod J 1989;11:89-92. I 1. OgaardB, RollaG, ArendsJ. Orthodonticappliancesand enamel demineralizations. Part 1. Lesion development. AM J ORTItOD DEN'rOFAeORTttOP1988;94:68-73. 12. Fricker JP, McLachlan MD. Clinical studies of glass ionomer cements. Part I. A 12-month study comparing zinc phosphate to glass ionomer. Aust Orthod J 1985;9:179-80. 13. MaijerR, Smith DC. A comparisonbetweenzinc phosphate and glass ionomercement in orthodontics. AMJ ORTItOD DF.NTOFAC ORnxoP 1988;93:273-9. 14. SeeholzerttW, Dasch W. Bandingwith a glass ionomercement. J Clin Orthod 1988;22:165-9. 15. MizrahiE. Glass ionomer.cementsin orthodontics--an update. AM J O~:'mODDE.'~"roFArOwrHoP 1988;93:505-7. 16. Fricker JP, McLachlan MD. Clinical studies on glass ionomer cements. Part 2. A 2-yearclinicalstudycomparingglass ionomer
384
Fricker
Am. J. Orthod. Dentofac. Orthop. April 1992
cement with zinc phosphate cement. Aust Orthod J 1987;10: 12-4. 17. Fryar BC. An evaluation of the bond strength and failure site of composite resin and glass ionomer in identical direct bonding systems [MScD Thesis]. Indiana University, 1989. 18. Cook PA, Youngson CC. An in vitro study of the bond strength of a glass ionomer cement in the direct bonding of orthodontic brackets. Br J Orthod 1988;15:247-53. 19. Klockowski R, Davis EL, Joynt RB, Wieczkowski G, MacDonald A. Bond strength and durability of glass ionomer cements used as bonding agents in the placement of orthodontic brackets. AM J ORT}tOD DENTOFACOR'I'IIOP 1989;96:60-4. 20. Miller JR. Clinical evaluation o f glass ionomer cement as an adhesive for the bonding of orthodontic brackets [Thesis]. Indiana University, 1988. 21. Powis DR, Folleras T, Merson SA, Wilson AD. Improved adhesion of a glass ionomer cement to dentine and enamel. J Dent Res 1982;62:223-8. 22. Fajen VB, Duncanson MG, Nanda RS, Currier GF, Angolkar PV. An in vitro evaluation of bond strength of three glass ionomer cements. AM J ORTHOD DEN'rOFACORIItOP 1990;97:316-22.
23. Mollenhauer B. New approaches to the Begg technique. Part 1: qualitative aspects. Aust Orthod J 1987;10:67-89. 24. Fricker JP, Hirota K, Tamiya Y. The effects of temperature on the setting of a glass ionomer cement. Aust Dent J 1991;36: 240-2. 25. Reynolds IR. A review of direct orthodontic bonding. Br J Orthod 1975;2:171-8. 26. Walls AWG, McCabe JF, Murray JJ. Factors influencing the setting reaction of glass polyalkenoate (ionomer) cements. J Dent 1988;16:32-5. 27. Earl MSA, ltume WR, Mount GJ. Effects of varnishes and other surface treatments on water movement across the glass-ionomer cement surface. Aust Dent J 1985;30:298-301. 28. Cook PA. Direct bonding with glass ionomer cement. J Clin Orthod 1990;24:509-I 1. Reprint requests to: Dr. J. P. Fricker P.O. Box 3544 Manuka, A.C.T. 2603 Australia
AAO MEETING CALENDAR 1992--St. Louis~ Mo., May 9 to 13, St. Louis Convention Center 1993--Toronto, Canada, May 15 to 19, Metropolitan Toronto Convention Center 1994--Orlando, Fla., May 1 to 4, Orange County Convention and Civic Center 1995--San Francisco, Calif., May 7 to 10, Moscone Convention Center
(International Orthodontic Congress) 1996--Denver, Colo., May 12 to 16, Colorado Convention Center 1997--Philadelphia, Pa., May 3 to 7, Philadelphia Convention Center 1998--Dallas, Texas, May 16 to 20;Dallas Convention Center 1999--San Diego, Calif., May 15 to 19, San Diego Convention'Center