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Background: Er-YAG laser showed to be effective in debonding ceramic bracket from the enamel surface. Until lately, no previous study was conducted to assess the outcome of the laser in debonding ceramic brackets from tooth surface comparing it with conventional occlusal pad debonding pliers. Materials and methods: Total 60 ceramic brackets were bonded on the tooth surface which was divided randomly into 2 groups. One was assigned as a control non-lased group and the other was experimental lased groups. Er-YAG laser irradiated the experimental groups at the power of 5 W for 10 seconds with swiping motion and 50% air-water cooling. In the lased experimental group, the laser was applied at energy of 250 mJ, 20 Hz frequency, and pulse duration of 100 μs. Results: Shear bond strengths and adhesive remnant index scores were statistically calculated. A highly significant difference of SBS between the non-lased control group and the lased experimental group was observed (p<0.000). A non-significant difference in ARI scores was observed when the non-lased control group was compared with the lased experimental group. Conclusion: It could be concluded that Er-YAG laser is effective in ceramic bracket debonding. This protocol promotes debonding without bracket fracture or enamel surface cracks or damage.
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The objective of this study is to compare the neutralization effect of various antioxidant agents on the bond strength of composite resins on stainless steel and ceramic brackets immediately bonded to previously bleached teeth. Materials and Methods: One hundred and sixty human maxillary premolars were used for the study. Teeth were divided into four groups (n = 40): Group 1 (control), Group 2 (bleached), Group 3 (sodium ascorbate), and Group 4 (tocopherol acetate). Each group was divided into two subgroups, one was bonded with stainless steel and other with ceramic brackets using 3M Transbond XT. Universal testing machine was used to determine the shear bond strength (SBS). Results: Among the metal brackets, Group 1A had the highest SBS (12.18 + 1.41 MPa) and Group 2A had the least SBS (6.18 + 1.49 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1A (13.99 MPa) and lowest for Group 2A (8.49 MPa). For ceramic brackets, Group 1B had the highest SBS (13.80 + 1.69 MPa) and Group 2B had the least SBS (8.05 + 1.85 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1B (14.61 MPa) and lowest for Group 2B (8.85MPa). Conclusion: The in vitro study showed that bleaching reduced the SBS significantly, and this could be effectively reversed by the application of antioxidants in both metal and ceramic brackets.
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OBJECTIVES: The aim of this study is to compare the shear bond strengths of ceramic brackets bonded to zirconia surfaces using different zirconia primers and universal adhesive. MATERIALS AND METHODS: Fifty zirconia blocks (15 × 15 × 10 mm, Zpex, Tosoh Corporation) were polished with 1,000 grit sand paper and air-abraded with 50 µm Al2O3 for 10 seconds (40 psi). They were divided into 5 groups: control (CO), Metal/Zirconia primer (MZ, Ivoclar Vivadent), Z-PRIME Plus (ZP, Bisco), Zirconia Liner (ZL, Sun Medical), and Scotchbond Universal adhesive (SU, 3M ESPE). Transbond XT Primer (used for CO, MZ, ZP, and ZL) and Transbond XT Paste was used for bracket bonding (Gemini clear ceramic brackets, 3M Unitek). After 24 hours at 37°C storage, specimens underwent 2,000 thermocycles, and then, shear bond strengths were measured (1 mm/min). An adhesive remnant index (ARI) score was calculated. The data were analyzed using one-way analysis of variance and the Bonferroni test (p = 0.05). RESULTS: Surface treatment with primers resulted in increased shear bond strength. The SU group showed the highest shear bond strength followed by the ZP, ZL, MZ, and CO groups, in that order. The median ARI scores were as follows: CO = 0, MZ = 0, ZP = 0, ZL = 0, and SU = 3 (p < 0.05). CONCLUSIONS: Within this experiment, zirconia primer can increase the shear bond strength of bracket bonding. The highest shear bond strength is observed in SU group, even when no primer is used.
Subject(s)
Adhesives , Ceramics , Orthodontic Brackets , Solar SystemABSTRACT
Background: When ceramic brackets were introduced as an esthetic alternative to the stainless steel brackets, it was a step ahead in the use of esthetic appliances for orthodontic treatment. Although ceramic brackets had overcome the drawbacks of the initial polycarbonate brackets such as staining and bracket slot distortion, they posed an altogether different problem. This was on account of the physical properties of the ceramic material, namely brittleness. Purpose of the Study: The purpose of this study is to investigate the physical properties of three different varieties of esthetic brackets, i.e., “MXI” ceramic bracket, “Spirit MB” bracket (Ormco), a composite bracket with metal slot reinforcement and the third one fiber bracket, with silicious copolymer, Natura (Leone Co.). Aims and Objective of the Study: The objective of this study is to compare the torsional resistance of the brackets and resistance of brackets to second order archwire activations. Conclusion: The strength of the selected brackets was more than sufficient to withstand orthodontic load without any fracture or deformation.
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OBJECTIVE: To evaluate the bonding strength of the ceramic bracket and composite resin restoration interface, using four types of treatment on the base of the bracket. METHODOLOGY: 48 photoactivated composite resin discs were used (FiltekTM Z250) contained in specimens and divided into 4 groups of 12 specimens for each group according to the type of treatment performed on the base of the brackets. Once the brackets were bonded, the specimens were subjected to shear stress carried out in a universal testing machine (MTS: 810 Material Test System) calibrated with a fixed speed of 0.5 mm / minute. The values obtained were recorded and compared by means of appropriate statistical tests - analysis of variance and then Tukey's test. RESULTS AND CONCLUSIONS: The surfaces of ceramic brackets conditioned with 10% hydrofluoric acid for 1 minute, followed by aluminum oxide blasting, 50µ, after silane application and primer application, was considered the best method to prepare surfaces of ceramic brackets prior to orthodontic esthetic bonding.
OBJETIVO: avaliar a resistência à união da interface entre braquete cerâmico e restauração de resina composta, empregando quatro tipos de tratamento na base do braquete. MÉTODOS: foram utilizados 48 discos de resina fotoativada (Filtek® Z250) incluídos em corpos de prova, divididos em quatro grupos, com 12 espécimes em cada grupo, de acordo com o tipo de tratamento realizado na base do braquete. Uma vez colados os braquetes, os corpos de prova foram submetidos à tensão de cisalhamento, realizado numa máquina universal de ensaios (MTS: 810 Material Test System) calibrada com velocidade fixa de 0,5mm/min. Os valores obtidos foram registrados e comparados por meio de médias, utilizando-se testes estatísticos adequados (análise de Variância e, posteriormente, teste de Tukey). RESULTADOS E CONCLUSÕES: o condicionamento das superfícies dos braquetes cerâmicos com ácido hidrofluorídrico a 10% por 1 minuto, seguido do jateamento com óxido de alumínio com 50um de tamanho, e posterior aplicação do silano e, depois, aplicação de adesivo, foi considerado o melhor método para o preparo de superfícies de braquetes cerâmicos previamente à colagem estética ortodôntica.
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OBJECTIVE: The purpose of this study was to determine (1) the shear bond strength (SBS) of an antimicrobial monomer-containing self-etching primer according to ceramic bracket types and (2) the bracket-adhesive failure mode using an adhesive remnant index (ARI). METHODS: A total of 90 extracted human teeth were randomly divided into 6 groups. Each group consisted of one of two ceramic brackets (monocrystalline, polycrystalline) and one of three primers (Transbond XT primer, Transbond Plus SEP, Clearfil Protect Bond) with each group containing 15 specimens. The SBS was measured, and adhesive residues left on the tooth surface were assessed. RESULTS: The SBS of polycrystalline ceramic bracket groups was significantly higher than that of the monocrystalline ceramic bracket groups (p < 0.001). The SBS of Transbond XT primer groups was significantly higher than those of Transbond Plus SEP groups and Clearfil Protect Bond groups (p < 0.001). All the groups showed bonding failures between the bracket base and adhesive. CONCLUSIONS: The combination of a self-etching primer with a monocrystalline bracket is recommended for clinical use, considering its acceptable SBS and mode of failure.
Subject(s)
Humans , Adhesives , Bisphenol A-Glycidyl Methacrylate , Ceramics , Dentin-Bonding Agents , Resin Cements , ToothABSTRACT
OBJECTIVE: The purpose of this study was to investigate the effect of tribochemical silica coating on the shear bond strength (SBS) of rebonded ceramic brackets using nano-filled flowable composite resin. METHODS: A total of 60 premolars were prepared and divided into 4 equal groups as follows: Tribochemical silica coating (TC) + Transbond XT (XT), TC + Transbond supreme LV (LV), Sandblast treatment (SA) + XT, SA + LV. Treated ceramic brackets were rebonded on the premolars using each adhesive. All samples were tested in shear mode on a universal testing machine. RESULTS: SBS of silica coated groups were high enough for clinical usage (TCLV: 10.82 +/- 1.82 MPa, TCXT: 11.50 +/- 1.72 MPa). But, SBS of the sandblast treated groups had significantly lower values than the tribochemical silica coated groups (SALV, 1.23 +/- 1.16 MPa; SAXT, 1.76 +/- 1.39 MPa; p< 0.05). There was no difference between the shear bond strength by type of adhesive. In the silica coated groups, 77% of the samples showed bonding failure in the adhesive. In the sandblast treated group, all bonding failures occurred at the bracket-adhesive interface. CONCLUSIONS: The result of this study suggest that newly introduced nano-filled flowable composite resin and tribochemical silica coating application on debonded ceramic bracket bases can produce appropriate bond strengths for orthodontic bonding.
Subject(s)
Adhesives , Bicuspid , Bisphenol A-Glycidyl Methacrylate , Ceramics , Collodion , Composite Resins , Resin Cements , Silicon DioxideABSTRACT
OBJECTIVE: The aim of this study was to find out whether Er:YAG laser can aid in debonding ceramic brackets, and to see what kind of method will be the most appropriate for debonding. METHODS: One hundred and ninety teeth, monocrystalline brackets (MISO(TM), HT, Ansan-Si, Korea), polycrystalline brackets (Transcend(TM) series 6000, 3M Untek, Monrovia, CA, USA) and the KEY Laser3 (KavoDental, Biberach, Germany) were used. Experimental groups were classified according to the type of ceramic brackets, and the amount of laser energy (0, 140, 300, 450, 600 mJ). After applying laser on the bracket at two points at 1 pulse each, the shear bond strength was measured. The effect of heat caused by laser was measured at the enamel beneath the bracket and pulp chamber. After measuring the shear bond strength, adhesive residue was evaluated and enamel surface was investigated using SEM. RESULTS: All ceramic bracket groups showed a significant decrease in shear bond strength as the laser energy increased. The greatest average temperature change was 3.78degrees C on the enamel beneath the bracket and 0.9degrees C on the pulp chamber. Through SEM, crater shape holes caused by the laser was seen on the enamel and adhesive surfaces. CONCLUSIONS: If laser is applied on ceramic brackets for debonding, 300 - 450 mJ of laser energy will be safe and efficient for monocrystalline brackets (MISO(TM)), and about 450 mJ for polycrystalline brackets (Transcend(TM) series 6000).
Subject(s)
Adhesives , Ceramics , Dental Enamel , Dental Pulp Cavity , Hot Temperature , ToothABSTRACT
OBJECTIVE: The purpose of this study was to investigate the effect of thermocycling and type of porcelain restoration on shear bond strength (SBS) and mode of failure of monocrystalline ceramic brackets. METHODS: A total of 60 porcelain discs were made and divided into three equal groups as follows: Ceramco 3, IPS Empress II, Zi-ceram/Vintage ZR. ceramic brackets were bonded to the prepared porcelain surfaces in the same manner. Each group was divided randomly into two subgroups: thermocycled group and non-thermocycled group (control). All samples were tested in shear mode on an universal testing machine. RESULTS: SBS of the non-thermocycled group was clinically acceptable (Ceramco 3: 7.06 +/- 1.76 MPa, IPS Empress II: 7.55 +/- 2.38 MPa, Zi-ceram/Vintage ZR: 7.19 +/- 1.38 MPa). But, SBS of the thermocycled group was significantly reduced (Ceramco 3: 4.88 +/- 1.00 MPa, IPS Empress II: 5.46 +/- 1.35 MPa, Zi-ceram/Vintage ZR: 4.84 +/- 1.01 MPa, p < 0.05). There was no difference between the shear bond strength by type of porcelain restoration. All bonding failure occurred between bracket base and adhesive, except for 2 samples. CONCLUSIONS: The results of this study suggest that the type of porcelain restoration did not affect SBS, but thermocycling weakened SBS. Therefore, the effect of thermocycling should be considered when using ceramic brackets in practice.
Subject(s)
Adhesives , Ceramics , Collodion , Dental Porcelain , Orthodontic BracketsABSTRACT
OBJECTIVE: The purpose of this study was to evaluate the shear bond strength of rebonded ceramic brackets according to each condition and find an appropriate method to rebond ceramic brackets with proper shear bond strength in clinical practice. METHODS: The study consisted of 12 experimental groups, according to the types of brackets, debonding methods, and treatment methods of the bracket base. Shear bond strength was measured, and adhesive residues left on the tooth surface were assessed. The base of the bracket was examined under scanning electron microscopy. RESULTS: The shear bond strength of the monocrystalline ceramic bracket group was significantly higher than thatof the polycrystalline bracket group with only sandblasting (p 0.05). The shear bond strength of the sandblasted/silane group was significantly higher than that of the selectively grinded group with a low-speed round bur and the sandblasted only group (p < 0.001). The retentive structure was more presented in groups where laser was applied than in groups where shear force was applied to debond brackets prior to rebonding. The bracket bases which were treated before rebonding presented smoother surfaces than new brackets. CONCLUSIONS: Shear bond strength could be increased by applying a silane coupling agent after sandblasting before rebonding. Also, the bond strength of the selectively grinded group with a low-speed round bur and the sandblasted group showed acceptable bond strength for clinical orthodontic treatment.
Subject(s)
Adhesives , Ceramics , Microscopy, Electron, Scanning , ToothABSTRACT
OBJECTIVE: The purpose of this study was to estimate the fracture resistance of commercially available ceramic brackets to torsional force exerted from arch wires and to evaluate the characteristics of bracket fracture. METHODS: Lingual root torque was applied to maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x0.027-inch stainless steel arch wire. A custom designed apparatus that attached to an Instron was used to test seven types of ceramic brackets (n = 15). The torque value and torque angle at fracture were measured. In order to evaluate the characteristics of failure, fracture sites and the failure patterns of brackets were examined with a Scanning Electron Microscope. RESULTS: Crystal structure and manufacturing process of ceramic brackets had a significant effect on fracture resistance. Monocrystalline alumina (Inspire) brackets showed significantly greater resistance to torsional force than polycrystalline alumina brackets except InVu. There was no significant difference in fracture resistance during arch wire torsional force between ceramic brackets with metal slots and those without metal slots (p > 0.05). All Clarity brackets partially fractured only at the incisal slot base and the others broke at various locations. CONCLUSION: The fracture resistance of all the ceramic brackets during arch wire torsion appears to be adequate for clinical use.
Subject(s)
Aluminum Oxide , Ceramics , Incisor , Stainless Steel , Torque , Torsion, MechanicalABSTRACT
Although ceramic brackets have been used widely for improved esthetics during treatment, ceramic brackets have some inherent problems; brittleness, attrition of the opposing teeth and high frictional resistance. This study was performed to understand the frictional resistance of the ceramic brackets, as well as to be a helpful reference for finding the solutions to the problem of frictional resistance. Three different kinds of brackets were used; metal bracket, polycrystalline ceramic brackets with a metal slot to reduce the high frictional resistance and monocrystalline ceramic brackets. The brackets were tested with a .019 x .025 stainless steel wire with a second order angulation of 0 degrees and 10 degrees, and the static and kinetic frictional forces were measured on the universal testing machine. The results of this study showed that the ceramic brackets, especially the monocrystalline ceramic bracket without a metal slot, generated higher frictional resistance than the metal bracket, and the frictional resistance was increased as the angulation between the bracket slot and the wire increased. Therefore, the development of the ceramic bracket with reduced frictional resistance and the prevention of excessive crown tipping during orthodontic treatment will lead to the simultaneous attainment of more efficient and improved esthetic treatment goals.
Subject(s)
Ceramics , Crowns , Esthetics , Friction , Stainless Steel , ToothABSTRACT
The purpose of this study was to measure and compare the level of frictional resistance generated from three currently used ceramic brackets; 1, Crystaline V(R), Tomy International Inc., Tokyo, Japan; 2, Clarity(R), 3M Unitek, Monrovia, CA, USA; 3, Inspire(R), Ormco, Orange, CA, USA; with composite resin brackets, Spirit(R), Ormco, Orange, CA, USA; and conventional stainless steel brackets, Kosaka(R), Tomy International Inc., Tokyo, Japan used as controls. In this experiment, the resistance to sliding was studied as a function of four angulations (0 degrees, 5 degrees, 10 degrees, and 15 degrees) using 2 different orthodontic wire alloys: stainless steel (stainless steel, SDS Ormco, Orange, CA, USA), and beta-titanium (TMA, SDS Ormco, Orange, CA, USA). After mounting the 22 mil brackets to the fixture and .019 x .025 wires ligated with elastic ligatures, the arch wires were slid through the brackets at 5 mm/min in the dry state at 34 degrees C. Silica-insert ceramic brackets generated a significantly lower frictional force than did other ceramic brackets, similar to that of stainless steel brackets. Beta-titanium archwires had higher frictional resistance than did stainless steel, and all the brackets showed higher static and kinetic frictional force as the angulations increased. When the angulation exceeded 5 degrees, the active configuration emerged and frictional force quickly increased by 2.5 to 4.5-fold. The order of frictional force of the different wire-bracket couples transposed as the angle increased. The silica-insert ceramic bracket is a valuable alternative to conventional stainless steel brackets for patients with esthetic demands.
Subject(s)
Humans , Alloys , Ceramics , Citrus sinensis , Family Characteristics , Friction , Japan , Ligation , Orthodontic Wires , Stainless Steel , SteelABSTRACT
Laser-aided debonding has advantages in that the heat produced is localized and controlled, the debonding tool is not heated, and it can be used for the removal of various types of ceramic brackets, regardless of their design. However, the range of safe power usage for laser-aided debonding has not yet been confirmed. The purpose of this study was to evaluate the histologic changes of pulpal tissue in a rabbit's incisor after Nd-YAG laser-aided ceramic bracket debonding at different levels of power. The result were as follows: 1. At 3-5W Nd-YAG laser power level and 3 seconds of exposure time, the ceramic bracket debonding procedure was not easy. At 5W of power a tie-wing fracture occurred on one bracket during debonding using Weingart plier. The histologic section of pulp represented no adverse changes. 2. At 7-13 W power level and less than 5 seconds of exposure time, the debracketing procedure was done easily and bracket facture did not occur. The histologic section of pulp represented mild and reversible changes. All the results were reversible and no pulpal degeneration or necrosis occurred. Considering the results, it appears that the laser-aided debonding technique is a safe method that does not result in irreversible pulpal changes, softens bracket bonding resin within a safe range of power and exposure time, and is useful for ceramic bracket recycling by lowering the tie- wing fracture rate.
Subject(s)
Ceramics , Hot Temperature , Incisor , Lasers, Solid-State , Necrosis , RecyclingABSTRACT
Objective To explore the best parameters of impulse Nd:YAG laser-aided debonding for ceramic bracket.Methods The removal of ceramic bracket from enamel surface by laser irradiation was investigated in vitro.Fifty-four premolars were used to test the tensile strength and 32 premolars for pulp cavity temperature test.The results were compared according to the laser setting(output power:0,2,3,5 W;time:2,4 s),the average force(830.3,556.5 g) necessary to break the adhesion between ceramic bracket and tooth,the different edible pigment on bracket surface(black or not).Results The bonding strength of ceramic bracket was significantly reduced by laser irradiation,averagely by 48%.The average bonding strenth in the six groups for tensile strength test was of statistical difference(P
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The purpose of this study was to evaluate the shear bond strength and failure mode of ceramic brackets according to the surface treatment of porcelain. Sixty porcelain samples were randomly divided into six groups of ten samples. Then they were treated as follows: Group 1(silane only), Group 2(etching + silane), Group 3(stone + silane), Group 4 (sandblasting + silane), Group 5(stone + etching + silane), Group 6(sandblasting + etching + silane) After surface treatment of porcelain, sixty Transcend 6000 brackets were bonded to the prepared porcelain surface and they were stored in 37 degrees C saline for 24 hours. An Instron universal testing machine was used to test the shear bond strength of ceramic brackets to porcelain. After debonding, bases of ceramic brackets and porcelain surfaces were examined under scanning electron microscope(SEM) to determine failure mode. Statistical analysis of the data was carried out with one-way ANOVA and Duncan's multiple range test. The results were as follows: 1. The shear bond strength of surface-treated groups 2 to 6 was higher than that of only silane-treated group 1, and there was statistical significance. (P0.05) As a conclusion we can have a clinically adequate bond strength when an application of silane is done after the treatment of porcelain surface with more than one way to bond ceramic bracket on the porcelain. Also, it is considered that the sandblasting and application of silane is effective for the simplication and convenience of the treatment.
Subject(s)
Ceramics , Dental PorcelainABSTRACT
The purpose of this study is to evaluate the effects of mechanical and thermal fatigue on the shear bond strength(SBS) in orthodontic brackets bonded to human premolars with chemically cured adhesive(Mono-Lok(2), Rocky Mountain Orthodontics). Two types of metal brackets (Ormesh, Microloc) and three types of ceramic brackets (Fascination, Starfire, Transcend 2000) were used in this study. The 10(6) loadcycles of l7.4 x 10(2)sin2piftl g,cm and the 1,000 thermocycles of 15 second dwell time each In 5degrees C and 55degrees C baths were acturated as mechanical and thermal fatigue stress, and SBS were measured after each fatigue test. The fracture sites were examined by stereoscope and scanning electron microscope. The results obtained were summarized as follows ; 1. In static shear bond test, Fascination brackets showed the maximum SBS(20.78+/-3.45 MPa) and Microloc brackets showed the minimum SBS(14.88+/-3.10 MPa). Fascination and Starfire brackets showed significantly greater SBS than Microloc brackets(P<0.05). 2. In mechanical fatigue test, Fascination brackets showed the maximum SBS (20.19+/-3.45 MPa) and Starfire brackets showed the minimum SBS(9.10+/-8.33 MPa). The SBS of Transcend 2000 brackets(P<0.01) and Starfire brackets(P<0.05) significantly decreased after 106 loadcycles. 3. In thermocycling test, Ormesh brackets showed the maximum SBS (19.36+/-2.76 MPa) and Starfire brackets showed the minimum SBS(l1.94+/-6.86 MPa). The SBS of Transcend 2000(P<0.01), Microloc and Starfire brackets(P<0.05) significantly decreased after 10(3) thermocycles. 4. Failure sites of thermocycling groups were similar to those of static groups but after mechanical fatigue test, Ormesh and Transcend 2000 brackets failed at the bracket/resin interface and Microloc brackets failed within adhesive. Facination brackets failed at the enamel/resin interface irrespective of experimental condition.
Subject(s)
Humans , Adhesives , Baths , Bicuspid , Ceramics , Dental Enamel , Fatigue , Orthodontic BracketsABSTRACT
The purpose of this study was to evaluate the effects of different bases of ceramic brackets on shear bond strength and to observe failure patterns of bracket bondings. Lower bicuspid brackets whose bases designed for the macromechanical and silane treated chemical bon?ding, those for silane treated chemical bonding, those for micromechanical bonding, and those for macrome?chanical bonding were tested as experimental groups, and foil mesh-backed metal brackets as a control group. All the brackets were bonded with Mono-Lok 2((TM)) on the labial surface of extracted human lower bicuspids after etching the enamel with 38% phosphoric acid solution for 60 seconds. The shear bond strengths were measured on the universal test machine after 24 hours passed in the 37degrees C water bath. The gathered data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. The shear bond strengths of brackets for macromechanical and chemical bonding, those for chemical bonding, and those for micromechanical bonding were not different (p>0.05), but showed statistically higher than those of metal bracket and those of ceramic bracket for macromechanical bonding(p<0.05). The shear bond strengths of ceramic bracket for macromechanical bonding showed statistically lower than those of metal bracket(p<0.05). The enamel fractures and/or ceramic bracket fractures were observed in the cases of higher bond strength than that of metal bracket. These results supported that silane treated base of ceramic bracket show higher shear bond strength than that of metal bracket, and suggested that micromechanical form of ceramic bracket bases show higher shear bond strength than that of macromechanical form.
Subject(s)
Humans , Baths , Bicuspid , Ceramics , Dental Enamel , WaterABSTRACT
The purpose of this study was to evaluate the in vitro shear bond strengths to enamel and the failure sites of three ceramic brackets and one metal bracket in combination with light cured orthodontic adhesive. The brackets were divided into four groups. Each ceramic bracket group had different bonding mechanisms with adhesive. Group A; metal bracket with foil-mesh base (control group) Group B; ceramic bracket with micromechanical retention Group C; ceramic bracket with chemical bonding Group D; ceramic bracket with mechanical retention and chemical bonding. Forty extracted human lower first premolars were prepared for bonding and 10 brackets for each group were bonded to prepared enamel surfaces with Transbond(R) light cured orthodontic adhesive. Twenty four hours after bonding, the Instron universal testing machine was used to test the shear bond strength of brackets to enamel. After debonding, brackets and enamel surfaces were examined under stereoscopic microscope to determine the failure sites. Statistical analysis of the data was carried out with ANOVA test and Scheffe test using SPSS PC+. The results were as follows: 1. There were statistically significant differences in mean shear bond strengths of three ceramic bracket groups (p<0.05). Shear bond strengths of group C and D were significantly higher than that of group B and shear bond strength of group C was significantly higher than that of group D. 2. Group C and D both had significantly higher shear bond strengths than metal bracket (group A), but there were no significant differences in shear bond strengths between group A and B (p<0.05). 3. The failure sites of four bracket groups were also different. Group C and D failed primarily at enamel-adhesive interface, but group A and B failed primarily at bracket base-adhesive interface. 4. Among all ceramic bracket groups, group B was very similar to metal bracket in the aspect of shear bond strength and failure site.