The Effects Of Different Surface Preparation Methods On The Bond Strength Of Metal Brackets Bonded To Different Ceramic.

With more adults seeking orthodontic treatment, orthodontists must often bond attachments to teeth with ceramic restoration. In such situations, the bond strength of brackets to the ceramic is not enough for the orthodontic treatment if the surface preparation is the same as the way for the bonding bracket to the enamel. Therefore, some special preparations for the bonding between bracket and ceramic are needed, such as etching with hydrofluoric acid(HF), sandblasting the ceramic surface(SB), combination with silane coupling agent(CP). At the present time, the ceramic restorations may be made by different material. Whether could the differences of ceramic restoration materials under different preparations result in the differences of the bond strength? It is very important for the preparation method choice in clinic. This study is focused on the research at this area, and is done from two aspects as follows.1. The effects of various surface preparation methods on the shear bond strength of mental brackets bonded to different ceramic surfaces1.1 Objectives: HF, SB and SB+HF are the usual surface preparations for the brackets to be bonded to the porcelain restorations. Silica -based ceramic, Aluminum-oxide ceramic and Zirconium-oxide ceramic are the usual porcelain restoration materials at the present time. The study is aimed to investigate whether the effects of the preparations on the porcelain restorations made by different materials are different. The study is useful for the choice of preparation method according to the porcelain restoration materials in the clinic work.1.2 Methods:3 kinds of porcelain restoration materials (VITA VMK@95, VITA VM@7,VITA VM@9) were sampled and produced into specimens. Every kind of material specimens were divided into 3 groups according the preparation method. The preparation methods were HF, SB and SB+HF. Shear bond strength (SBS) was tested and compared among different preparation groups and different porcelain materials. The effects of the three kinds of surface preparations were investigated and compared by scanning electronic microscope (SEM).1.3 Results:1.3.1 The results of variance analysis shows that the SB ,HF,SB +HF three surface treatments have significant influence in the shear bonding strength. Compared with SB and SB+HF, the HF surface preparation surface preparation group shows the lowest SBS (P<0.05), and the average is lower than the orthodontic clinic bond strength requirement, while there was no significant difference between SB and SB+HF groups (P>0.05), and generally can achieve orthodontic clinic bond strength requirement. For The same kind of surface treatment method, there was no significant difference of SBS among the three kinds of porcelain materials (P>0.05). There was no significant difference between the three different materials and three surface treatments methods. 1.3.2 The SEM observation results show that no matter what kind of porcelain material were made by three different surface treatment methods, relative to the surface without treatment, there has been an increase in the surface roughness and porosity. While the SB and SB+HF surface roughness of the specimen surface porosity are higher than the HF treatment group alone, SB and SB+HF of surface treatment effect is nearly equal.1.4 Conclusion: The difference of porcelain restoration material does not result in the change of SBS for the metal bracket which were bonded to them, from the perspective of increasing the SBS of orthodontic bracket to porcelain restorations, SB preparation is a priority for surface treatment of choice compared with the HF, but the HF preparation combined with SB can not provide more higher SBS compared with SB treatment alone. It is suggested that the HF after SB is unnecessary for the bonding strength improving.2. The effects of various surface preparation methods with coupling agent on the shear bond strength of orthodontic brackets bonded to different ceramic surfaces2.1 Objectives: this part of the study is aimed to investigate the effects of various surface preparation methods with coupling agent on the shear bond strength of orthodontic brackets bonded to different ceramic surfaces.2.2 Methods: 3 kinds of porcelain restoration materials were sampled and produced into specimens. Every kind of material specimens were divided into 4 groups according the preparation method. The preparation methods were sandblasting (SB), hydrofluoric (HF) acid, sandblasting combined silane coupling agent(SB+CP)and hydrofluoric combined silane coupling agent (HF+CP). Shear bond strength (SBS) was tested and compared among different preparation groups and different porcelain materials.2. 3 Result: The results of variance analysis shows that silane coupling agent (CP) can significantly improve the SBS either SB or HF (P<0.05) when it plays as an auxiliary measures for surface treatment, and the characteristics of CP at this point do not depend on the kind of ceramic restoration material (P>0.05). Through the sole HF preparation can not result in enough SBS for orthodontic treatment, the CP combined with HF surface treatment can improve the SBS to the clinical requirement.2. 4 Conclusion: These results suggest that the CP as an auxiliary measure can result in the improvement of the SBS for the SB or HF porcelain surface treatment. The HF+CP surface treatment could increase the SBS while the SBS of HF preparation is not satisfied with the clinical requirement.3. According to the results of the two parts above, the following conclusions could be achieved.3.1 For the various surface treatment methods, there is no significant difference for the mental bracket to be bonded to the ceramic restoration if the ceramic materials are different. 3.2 For different materials production restoration, the SB surface treatment can ensure the SBS of orthodontic brackets achieve the clinical requirements, while the HF treatment can not reach the SBS, and the SB+ HF treatment can not result in higher strength than the SB alone. It is suggested that SB is a priority surface treatment for the ceramic restorations, and the HF as an auxiliary measure in SB treatment is not necessary for the bonding strength improving.3.3 As the porcelain restorations are made of different material, the CP can improve the SBS significantly either SB or for HF when it is used as an auxiliary measure. And it can change the bonding strength under HF preparation to reach clinical requirement. This result shows it is necessary for the CP to be combined with HF preparation. And if without special requirement for the bonding strength, it is not necessary for the CP to be combined with SB preparation since the strength under SB preparation alone is enough for the orthodontic treatment.