Fracture incidence on debonding ain veneer laminates Elizabeth
C. Kao,
DMD,*
and William
M. Johnston,
of orthodontic
brackets
from
PhDb
Ohio State University, College of Dentistry, Columbus, Ohio The bonding force and the incidence of porcelain fracture for two porcelain systems, on removal of orthodontic brackets bonded to porcelain veneer laminates after thermocycling, were determined. A factorial design with a total sample size of 256 was used. The factors tested were (1) porcelain type (feldspathic [porcelain CE] or high alumina [porcelain VI]), (2) surface treatment (glazed or roughened), (3) priming agent (silane or alcohol), (4) bonding resin (macrofilled or microfilled), and (5) debonding time (30 minutes or 24 hours). An analysis of variance revealed that surface treatment, primer, resin type, and debonding time each contributed significantly to the debonding force. The probability. of porcelain fracture was dependent on the porcelain type and the debonding force, with porcelain VI exhibiting a significantly higher probability of fracture than porcelain CE at the same debonding force. The etched surface of porcelain CE exhibited a more retentive microstructure than porcelain VI. The success of using bonded orthodontic brackets on porcelain veneer laminates depends on both the bond of resin to porcelain and the resistance of porcelain to fracture during debonding. For a given porcelain veneer, factors that provide a higher debonding force result in a higher probability of porcelain veneer fracture. (J PROSTEET DENT 1991;66:631-7.)
A s new esthetic restorative
techniques and materials become available, restoring teeth for improving esthetics has become a procedure widely accepted by the dental profession. Veneering is often the clinical treatment of choice for teeth with discoloration, unesthetic existing restorations, diastemata, enamel defects, developmental deformities, or malalignment. The types of veneer laminates used to restore unesthetic teeth are the directly made composite resin and the indirectly made veneer. The indirect veneers include resin and porcelain materials. Porcelain offers advantages over other veneering materials in resistance to abrasion, cohesive strength, and the ability to control color and surface texture. Porcelain can be stained both internally and superficially and has a natural fluorescence that lends vitality. Surface texture can simulate that of adjacent natural teeth and can be maintained indefinitely. As veneering is becoming more widely used as a restorative option, it is likely that dentists will face the problem of placing orthodontic appliances on teeth restored with veneers. This is particularly true since adult orthodontics has gained acceptance as a viable treatment option. The research of Buonocorel on the acid-etch technique combined with use of filled resins, as advocated by Bowen,2t 3 has provided technology that allows mechanical
resin bonding between etched teeth and orthodontic appliances. The direct bonding technique, however, was not effective for a nonenamel surface such as porcelain. Recent research has made it possible to achieve direct bonding to nonenamel surfaces. In laboratory and clinical studies, organosilane has been shown to be useful for bonding porcelain teeth to acrylic resin denture bases,4-7 repairing fractured porcelain teeth and facings with composite resin,*-l3 and priming ceramic orthodontic brackets for direct bonding.14 When silanating agents are used, orthodontic attachments have been shown to successfully bond to porcelain denture teeth, cast crowns, and porcelain-fused-to-metal crowns. 15-20A previous study on bonding to veneer laminate systems2r indicated that porcelain failure on debonding may be a considerable risk but did not consider the influences of thermocycling before testing. The objectives of this study were (1) to determine the force required to remove orthodontic attachments bonded to two types of porcelain veneer laminates after thermocycling and to determine the effect of the test resin type, priming agent, porcelain surface preparation, and debonding time on the forces required to debond orthodontic attachments and (2) to relate the incidence of fracture to the debonding force and to determine whether this relation is significantly affected by porcelain type. METHODS
aAssistantProfessor,Department of Restorative and Prosthetic Dentistry. bAssociateProfessor,Department of Restorative and Prosthetic Dentistry. 16/l/29087
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
AND
MATERIAL
Two hundred fifty-six bovine mandibular central and lateral primary incisors of similar size and shape were extracted and stored in physiologic saline solution. Veneer preparations were made to a 0.5 mm depth on the facial
631
Two veneering porcelains, a ~~g~“a~.~~i~aporcelain (Vidur-N [VI], Vita Zahmfabrik ad SBckingen, Germany) an ~~~ra~~o II [CE], Johnson & Johnson, NJ.), were used in the study. Impressions were made of the prepared teeth, and refractory casts were poured with irivestment materials sm~~li~a by the ~a~~factu~er~ (HiBI refractory inve ty porcelain CE a refractory casts and fired glazed according to the ~a~~fact~~e~~’ directiom. the veneer ianhates were bonded onto the of the porcelain was stone Prc its Co., ~~ilade~~~ia~ Pa.), a c~~~~~c~a~~~ available suggested
so%3uoric acid s~bst~tut~~ for 3 minutes a5 by previous studies.22-24 The etched veneer lam-
d teeth with lighti Mieh.) as the vemeer cements Each toetb was partially embedded in an epoxy resin disk with only the veneered surface exposed. To standardize the placement,
each tooth
was at
-forming mold by a s ankakee, Ill.1 weather Id was then placed on a surveyor taartford, Corm.:?. iFhe tooth was repoattachment so that the labial SUTface was aligned ~e~~e~dicula~ to t E long axis of the .mrveyor rod. The veneered 1000
in
teeth
were then
tb~~~~cy~~~d
through
The ~~e~~o~~~~i~g regimen used study was the cycling sequence advocated by Grim
te~~~rat~~~
cycles.
an atti~~gly~~ and is based on the WCS%of Browxl et a1.26 and Lloyd et ai.27 They fmnd that in v~o ex~~§~~e§to extrem te~~~~~ratmrgsare wxuaily of short duration. The ~ax~~m~ thermal gradient in enamel develops within 1 second.after exposure, and the temperaZure rapidly returns to oral perature once extreme e~v~Ko~~~nts are removed. sed on their findings, the following t~~~~rat~r~ cycle was chosen: a L-minute
cycle ~Q~sisti~g
of 15 seconds
at 60” 6, 37’ C, and So 6; and then a return to the 37” C water. After tbgr~o~y~~i~g was compiete the veneered teeth were stored in saline solution at 37” C until testing, dration
of
the
teeth.
ks for CE veneer and 96 disks for VI veneer nto 16 groups of 10 and six sanzpies, i-especLively (Table I). The labial surfaces of teeth in half of these groups were modified with a green stone to roughe:~ the surface glaze. The surface giaze was left intact ir the remaining groups.
FRACTURE
INCIDENCE
OF PORCELAIN
VENEER
LAMINATES
0 Ceramco
C. Kao,
DMD,*
and William
M. Johnston,
of orthodontic
brackets
from
PhDb
Ohio State University, College of Dentistry, Columbus, Ohio The bonding force and the incidence of porcelain fracture for two porcelain systems, on removal of orthodontic brackets bonded to porcelain veneer laminates after thermocycling, were determined. A factorial design with a total sample size of 256 was used. The factors tested were (1) porcelain type (feldspathic [porcelain CE] or high alumina [porcelain VI]), (2) surface treatment (glazed or roughened), (3) priming agent (silane or alcohol), (4) bonding resin (macrofilled or microfilled), and (5) debonding time (30 minutes or 24 hours). An analysis of variance revealed that surface treatment, primer, resin type, and debonding time each contributed significantly to the debonding force. The probability. of porcelain fracture was dependent on the porcelain type and the debonding force, with porcelain VI exhibiting a significantly higher probability of fracture than porcelain CE at the same debonding force. The etched surface of porcelain CE exhibited a more retentive microstructure than porcelain VI. The success of using bonded orthodontic brackets on porcelain veneer laminates depends on both the bond of resin to porcelain and the resistance of porcelain to fracture during debonding. For a given porcelain veneer, factors that provide a higher debonding force result in a higher probability of porcelain veneer fracture. (J PROSTEET DENT 1991;66:631-7.)
A s new esthetic restorative
techniques and materials become available, restoring teeth for improving esthetics has become a procedure widely accepted by the dental profession. Veneering is often the clinical treatment of choice for teeth with discoloration, unesthetic existing restorations, diastemata, enamel defects, developmental deformities, or malalignment. The types of veneer laminates used to restore unesthetic teeth are the directly made composite resin and the indirectly made veneer. The indirect veneers include resin and porcelain materials. Porcelain offers advantages over other veneering materials in resistance to abrasion, cohesive strength, and the ability to control color and surface texture. Porcelain can be stained both internally and superficially and has a natural fluorescence that lends vitality. Surface texture can simulate that of adjacent natural teeth and can be maintained indefinitely. As veneering is becoming more widely used as a restorative option, it is likely that dentists will face the problem of placing orthodontic appliances on teeth restored with veneers. This is particularly true since adult orthodontics has gained acceptance as a viable treatment option. The research of Buonocorel on the acid-etch technique combined with use of filled resins, as advocated by Bowen,2t 3 has provided technology that allows mechanical
resin bonding between etched teeth and orthodontic appliances. The direct bonding technique, however, was not effective for a nonenamel surface such as porcelain. Recent research has made it possible to achieve direct bonding to nonenamel surfaces. In laboratory and clinical studies, organosilane has been shown to be useful for bonding porcelain teeth to acrylic resin denture bases,4-7 repairing fractured porcelain teeth and facings with composite resin,*-l3 and priming ceramic orthodontic brackets for direct bonding.14 When silanating agents are used, orthodontic attachments have been shown to successfully bond to porcelain denture teeth, cast crowns, and porcelain-fused-to-metal crowns. 15-20A previous study on bonding to veneer laminate systems2r indicated that porcelain failure on debonding may be a considerable risk but did not consider the influences of thermocycling before testing. The objectives of this study were (1) to determine the force required to remove orthodontic attachments bonded to two types of porcelain veneer laminates after thermocycling and to determine the effect of the test resin type, priming agent, porcelain surface preparation, and debonding time on the forces required to debond orthodontic attachments and (2) to relate the incidence of fracture to the debonding force and to determine whether this relation is significantly affected by porcelain type. METHODS
aAssistantProfessor,Department of Restorative and Prosthetic Dentistry. bAssociateProfessor,Department of Restorative and Prosthetic Dentistry. 16/l/29087
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
AND
MATERIAL
Two hundred fifty-six bovine mandibular central and lateral primary incisors of similar size and shape were extracted and stored in physiologic saline solution. Veneer preparations were made to a 0.5 mm depth on the facial
631
Two veneering porcelains, a ~~g~“a~.~~i~aporcelain (Vidur-N [VI], Vita Zahmfabrik ad SBckingen, Germany) an ~~~ra~~o II [CE], Johnson & Johnson, NJ.), were used in the study. Impressions were made of the prepared teeth, and refractory casts were poured with irivestment materials sm~~li~a by the ~a~~factu~er~ (HiBI refractory inve ty porcelain CE a refractory casts and fired glazed according to the ~a~~fact~~e~~’ directiom. the veneer ianhates were bonded onto the of the porcelain was stone Prc its Co., ~~ilade~~~ia~ Pa.), a c~~~~~c~a~~~ available suggested
so%3uoric acid s~bst~tut~~ for 3 minutes a5 by previous studies.22-24 The etched veneer lam-
d teeth with lighti Mieh.) as the vemeer cements Each toetb was partially embedded in an epoxy resin disk with only the veneered surface exposed. To standardize the placement,
each tooth
was at
-forming mold by a s ankakee, Ill.1 weather Id was then placed on a surveyor taartford, Corm.:?. iFhe tooth was repoattachment so that the labial SUTface was aligned ~e~~e~dicula~ to t E long axis of the .mrveyor rod. The veneered 1000
in
teeth
were then
tb~~~~cy~~~d
through
The ~~e~~o~~~~i~g regimen used study was the cycling sequence advocated by Grim
te~~~rat~~~
cycles.
an atti~~gly~~ and is based on the WCS%of Browxl et a1.26 and Lloyd et ai.27 They fmnd that in v~o ex~~§~~e§to extrem te~~~~~ratmrgsare wxuaily of short duration. The ~ax~~m~ thermal gradient in enamel develops within 1 second.after exposure, and the temperaZure rapidly returns to oral perature once extreme e~v~Ko~~~nts are removed. sed on their findings, the following t~~~~rat~r~ cycle was chosen: a L-minute
cycle ~Q~sisti~g
of 15 seconds
at 60” 6, 37’ C, and So 6; and then a return to the 37” C water. After tbgr~o~y~~i~g was compiete the veneered teeth were stored in saline solution at 37” C until testing, dration
of
the
teeth.
ks for CE veneer and 96 disks for VI veneer nto 16 groups of 10 and six sanzpies, i-especLively (Table I). The labial surfaces of teeth in half of these groups were modified with a green stone to roughe:~ the surface glaze. The surface giaze was left intact ir the remaining groups.
FRACTURE
INCIDENCE
OF PORCELAIN
VENEER
LAMINATES
0 Ceramco
