Fracture incidence on debonding of orthodontic brackets from porcelain veneer laminates.

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.     

Direct bonding of orthodontic brackets

The direct adhesive bonding of orthodontic brackets to enamel was investigated. For a number of resin systems, all based on a bisphenol-GMA type of resin, commercially available or synthesized, the adhesive bonding to the enamel as well as to the bracket was studied.The maximum average bond strength to enamel was 121 Kg. per square centimeter; the maximum adhesion to the bracket material was 53 Kg. per square centimeter. Consequently, the attachment of the adhesive to the bracket material is the bottleneck of the direct-bonding procedure.Special attention has been given to preconditioning procedures to enhance the bonding between adhesive and bracket. The best results were obtained when the bracket base was roughened by means of a small amount of resin powder. Because all adhesives studied show large standard deviations of the bond strength, criteria of reliability are discussed. They show that future approaches should aim not only for higher average bonds strengths but also for a smaller standard deviation.The setting process, one of the factors influencing reliability, has been considered in some detail. Results of different mixing ratios as well as the influence of the amount of catalyst are presented.     

Direct bonding of orthodontic brackets to tooth structure

A bstract — An orthodontic bracket suitable for direct bonding to tooth structure is described and the strength of the bond is tested and evaluated.     

The effect of porcelain surface conditioning on bonding orthodontic brackets

The purpose of this study was to evaluate the effects of a new self-etching primer/ adhesive used to enhance the shear strength of orthodontic brackets bonded to porcelain surfaces. Forty-five porcelain maxillary central incisor teeth were used in the study. The teeth were divided randomly into three groups: group I (control), the porcelain teeth were etched with 37% phosphoric acid followed by a sealant and the brackets were bonded with a composite adhesive; group II, the porcelain teeth were microetched and hydrofluoric acid and silane applied and metal brackets were then bonded with the composite adhesive; and group III, the porcelain teeth were etched with phosphoric acid and a self-etching primer/adhesive applied before bonding. Brackets precoated with the adhesive were used on all three groups of teeth. All teeth were stored for 24 hours at 37 degrees C before debonding. The results of the analysis of variance (F = 10.7) indicated that there was a significant difference (P = .001) between the three groups. The mean shear bond strengths of conventional bonding using a 37% phosphoric acid and sealant was 4.4 +/- 2.7 MPa, whereas that of microetching followed by the application of hydrofluoric acid and silane was 11.2 +/- 4.7 MPa, and for the new self-etching primer/adhesive it was 10.3 +/- 5.3 MPa. The last two groups had the highest bond strength values and were not significantly different from each other.     

Direct bonding of orthodontic brackets to esthetic restorative materials using a silane

Along with adult orthodontics comes a concern for direct-bonding techniques with esthetic anterior restorative materials. Two such materials available today are porcelain and a heat-cured composite resin. The ability to bond orthodontic brackets to these materials was tested with a normal direct-bonding technique. In addition, silane was used to theoretically enhance the bond to porcelain and the glass component of the composite. A normal acid-etch procedure to enamel served as a comparison. Bonding equivalent to the enamel acid-etch procedure was achieved with the heat-cured composite, whether silane was used or not. Silane enhanced the bond to porcelain, but the bond might not be adequate for clinical effectiveness.     

Direct orthodontic bonding to porcelain: an in vitro study.

The shear/peel and tensile/peel bond strengths of mesh-backed orthodontic brackets bonded to porcelain, using a highly filled composite and four different silane bonding agents were determined. Sites of failure were recorded for each method of testing. A method of debonding ane restoring the porcelain surface to its original state after debonding was also investigated. All silane bonding systems tested provided adequate bond strength for clinical use. Fusion produced significantly higher force values to failure in shear testing. There was no significant difference between the bond strengths obtained in tensile testing. Patterns of failure differed in each mode of testing, suggesting that a shear mode of debonding is more likely to cause porcelain fracture and that the possibility of porcelain fracture during function or debonding cannot be excluded. The use of a Lift-Off plier is recommended in debonding brackets from porcelain where a silane bonding agent has been used. Diamond polishing paste was better at restoring the procelain surface to its original appearance than Shofu polishing stones.     

正畸托槽间接粘接的临床应用

目的 探讨正畸托槽的间接粘接技术,以提高托槽定位的准确性。方法 选取南京医科大学附属口腔医院正畸科18名成人正畸患者,采用间接粘接技术粘接托槽,模型粘接和口内粘接均为同一医生进行,技工室压模均由同一技工完成。结果 18例患者的302个托槽在粘接过程中,有13个托槽在压模时发生脱落,1个在口内粘接时脱落。与直接粘接法相比,间接粘接法椅旁操作时间减少,但操作繁琐、总操作时间增加。结论 间接粘接技术托槽放置精确,椅旁操作时间减少,利于初学者培养托槽定位感,适合舌侧矫治器的粘接。     

In vitro orthodontic bracket bonding to porcelain

This in vitro study investigated the influence of using different combinations of bracket, adhesive, and light-curing source on the tensile bond strength to porcelain and on failure patterns at debonding. Tensile tests were performed using: one ceramic bracket versus one metal bracket, two orthodontic composites; type bisphenol A-glycidyldimethacrylate and urethane dimethacrylate (UDMA), and four light-curing units with the same range of emission spectrum but various light intensities: three light-emitting diode (LED) units and one halogen-based unit. One hundred and sixty porcelain samples were randomly divided into 16 equal groups. The porcelain surface was conditioned with 9 per cent hydrofluoric acid before silane application. The composite was photo-polymerized for 40 seconds. After storage in water at 37°C for 24 hours, the samples were subjected to tensile force until bond failure. Bond strength and bond failure mode were recorded; results were analysed (α = 0.05) using R language; linear model with constant variance for the bond strength and multinomial distribution for the failure mode. The bond strength in all groups was sufficient to withstand orthodontic treatment (>6 MPa). There was no statistical difference between the adhesives, but comparing bracket × light interaction, it was significantly higher with the ceramic bracket. No significant differences were seen between the metal bracket groups, but for the ceramic bracket, the results were significantly higher with the LED light. No fracture was observed in porcelain with the metal bracket but it occurred in 35 per cent of the ceramic bracket samples and the risk was higher when using UDMA composite and lower with LED high intensity light.     

Factors affecting the shear bond strength of orthodontic brackets to porcelain

The aim of this investigation was to establish a regime for orthodontic bonding to feldspathic porcelain, which ensures adequate bond strength (6-8 MPa) with minimal damage on debond and consisted of an ex vivo investigation measuring the effects of porcelain surface preparation and thermocycling on shear bond strength of orthodontic brackets. One-hundred-and-twenty feldspathic porcelain bonded crown surfaces were divided into 12 equally-sized groups to assess the effects of: (1) glaze removal, (2) application of hydrofluoric acid, phosphoric acid, or omission of acid treatment, and (3) silane priming upon the bond strength of premolar brackets bonded with Right-on (TM) composite resin adhesive. Specimens were subjected to thermocycling and then to shear debonding forces on an Instron machine. Removal of the porcelain glaze, or use of hydrofluoric acid, prior to bonding were found to be unnecessary to secure the target bond strength. Hydrofluoric acid application was associated with increased porcelain surface damage. Thermocycling caused a significant reduction in shear bond strength to porcelain (P < 0*001). The best regime for orthodontic bonding to feldspathic porcelain was to apply phosphoric acid for 60 seconds, and prime with silane prior to bonding. Usually the porcelain surfaces could be repolished. Refereed Paper     

Tensile bond strength of ceramic orthodontic brackets bonded to porcelain surfaces

The aim of this study was to compare various surface treatment methods to define the procedure that produces adequate bond strength between ceramic brackets and porcelain. The specimens used in this study, 60 porcelain tabs, were produced by duplication of the labial surface of a maxillary first premolar. The 6 different preparation procedures tested were: (1) sandblasting with 50 microm aluminum oxide in a sandblasting device, (2) application of silane to the porcelain and the bracket base, (3) sandblasting followed by application of silane, (4) acid etching with 9.6% hydrofluoric acid, (5) acid etching with 9.6% hydrofluoric acid followed by application of silane, and (6) sandblasting followed by application of 4-Meta adhesive. The ceramic brackets were bonded with no-mix orthodontic bonding material. A bonding force testing machine was used to determine tensile bond strengths at a crosshead speed of 0.5 mm per second. The results of the study showed that porcelain surface preparation with acid etching followed by silane application resulted in a statistically significant higher tensile bond strength (P < .05). Sandblasting the porcelain surface before silane treatment provided similar bond strengths, but sandblasting or acid etching alone were less effective. Silane application was recommended to bond a ceramic bracket to the porcelain surface to achieve bond strengths that are clinically acceptable.